The complex reflective properties of highly reflective surface bring overexposure and underexposure problems to surface structured light technology. In order to reconstruct the measured surface completely and accurately, a multiple exposure method is proposed, which can predict the exposure time according to the reflective intensity of the measured surface. Firstly, the camera response curve of the imaging system is obtained by projecting a series of uniform gray images at different exposure times, and at the same time, the irradiance image which can reflect the reflection intensity of the measured surface is calculated. Then, the fuzzy C-means clustering method is used to adaptively segment different irradiance regions of the target and obtain the central irradiance of each region, and the optimal exposure time is predicted for different reflection regions based on the camera response curve. Finally, the 3D reconstruction of the highly reflective surface is realized by combining the multiple exposure fusion algorithm. The experimental results show that the proposed method can simultaneously reconstruct the strongly reflective area and the excessively dark area of the aluminum alloy surface, with the reconstruction error less than 0.5mm, the maximum deviation reduced by 74.78% and the standard deviation reduced by 48.96%. The proposed method can correctly predict the exposure time according to the regional reflection characteristics, effectively overcome the problems of phase loss and phase distortion caused by regional overexposure and regional darkness, and completely and accurately reconstruct different reflection regions of the highly reflective surface.
Aiming at the problems of low accuracy and easy to fall into local optimal solutions of the existing lens distortion parameter estimation methods, a catadioptric omnidirectional camera lens distortion parameter method based on the improved Aquila optimization (AO) algorithm is proposed.
Firstly, the optimization ability of the Aquila optimization algorithm is enhanced by integrating chaotic mapping, adaptive adjustment strategy and population optimization strategy, which solves the problems of slow convergence speed and easy to fall into local optimal solutions. Secondly, the distribution range of distortion parameters is derived and determined by the corresponding distortion edges of straight lines in the space and the one parameter divisive model, and then the optimization objective function containing the distortion parameters is constructed. Finally, the improved Aquila optimization algorithm is used to find the best distortion parameters for the optimization objective function.
After analyzing the correction results of standard gallery images and omnidirectional images, the method proposed in this paper estimates the main point error within 0.5 pixel and the radial aberration coefficient error within 2.5%, which is able to effectively estimate the lens aberration parameters and realize the omnidirectional image aberration correction.
It improves the image quality of the visual navigation system under the task of environment perception and is valuable in engineering applications.
In order to accurately measure an object’s three-dimensional surface shape, the influence of sampling on it was studied. First, on the basis of deriving spectra expressions through the Fourier transform, the generation of CCD pixels was analyzed, and its expression was given. Then, based on the discrete expression of deformation fringes obtained after sampling, its Fourier spectrum expression was derived, resulting in an infinitely repeated "spectra island" in the frequency domain. Finally, on the basis of using a low-pass filter to remove high-order harmonic components and retaining only one fundamental frequency component, the inverse Fourier transform was used to reconstruct the signal strength. A method of reducing the sampling interval, i.e., reducing the number of sampling points per fringe, was proposed to increase the ratio
目的:粒化是柑橘类水果常见的一种内部病害,患有该病害的水果外部特征并不明显难以从外观上直接进行识别。方法:本研究基于激光多普勒测振技术对果冻橙粒化病进行无损检测。本研究使用微型激光多普勒测振仪(micro-LDV)和共振喇叭搭建了一套声学振动实验装置,将其用于采集“爱媛38号”果冻橙的振动响应信号。将一维的振动响应信号转换为振动多域图像,并构建了一个Resnet-Transformer网络(ResT),用于提取振动多域图像中的深层特征,以识别果冻橙粒化病。首先,使用振动多域图像训练ResT、Resnet50和Vision Transformer(ViT)模型,将ResT的性能与Resnet50和ViT的性能进行比较。然后使用振动多域图像纹理特征或振动频谱特征训练PLS-DA和SVM模型,并与ResT模型进行性能对比。结果:结果表明,使用振动多域图像训练的ResT模型可以实现精准识别果冻橙粒化病并且检测准确率为98.61%,模型的F1为0.986、精确率为0.986、召回率为0.986。结论:提出的方法可在简单、快速、低成本的前提下准确识别粒化果冻橙。
为了实现对短距光纤数据通信系统接收端非线性损伤的低复杂度均衡,提出了一种基于全连接神经网络的接收端均衡算法,并在其中引入判决反馈结构的判决反馈神经网络。通过使用线性工作区与实验系统不匹配的光电探测器引入非线性畸变,实现了基于C波段直接调制激光器的56 Gbit/s PAM4信号的20km传输验证实验,并对判决反馈神经网络和其他均衡方案的均衡性能进行了对比实验。实验结果表明,相比全连接神经网络,改进方案实现了20 km传输时2 dB的灵敏度提升。所提算法可以很好地均衡光电器件的非线性不均衡性的同时计算复杂度更低,具有很好的应用意义。
红外数据作为信息化数据库的重要组成部分,在夜视侦察、武器制导、远程预警等方面得到广泛应用。针对红外辐射特性测量系统在环境温度变化情况下产生温漂,导致目标的红外反演精度收到较大影响,本文提出了基于环境温度自适应修正的内外联合定标方法,通过自适应插值的方式对环境温度变化影响进行修正;以高精度面源黑体作为目标进行辐射反演测量试验,最小误差为6.82%、最大误差为10.21%。同时,对水上动态目标开展辐射特性反演,得到高置信度的实测目标辐射特性数据;通过黑体以及水上动态目标的测量试验可以得到:本方法可以在海洋气候复杂环境下实现环境温度变化对辐射反演精度的影响修正,验证了所提出的定标算法的有效性,同时可以基于修正参数进行红外系统环境温度敏感性的有效评估测试。
针对目前中波红外变焦系统,在大变倍比,长焦距变焦的条件下,难以实现极短总长且具备较低敏感度的问题,本文采用合理的分配非球面和衍射面,以及独立组元低敏感度设计的方法,通过降低各个组元的像差从而达到降低系统公差敏感度的目的,实现系统的简洁化和小型化,并提高工程应用的可行性。设计出一套无需折叠光路,总长仅有337mm的低敏感度中波红外变焦光学系统。该系统达到了30倍大变倍比,30~900mm的长焦距连续变焦。系统具有变倍比大,长焦距变焦,极短总长以及低敏感度并且全焦距范围内像质良好等优点,对在狭小空间内进行目标识别、跟踪、探测等军事领域的需求,具有较大的应用优势。
Non-uniformity correction is a crucial procedure for infrared imaging systems to achieve high quality infrared images. Currently, many large-aperture infrared radiation measurement system encounter numerous issues, such as non-uniformity correction being time-consuming and inadequate in-field applications. In this paper, a rapid and extensive dynamic non-uniformity correction algorithm is suggested for the requirement of continuous change of integration time in infrared radiation measurement system. The algorithm considers the impact of integration time effect and stray radiation of the optical system. The experimental verification was conducted by employing cooled mid-wave infrared radiation characteristic measurement system with a 25 mm aperture. The correction efficiency of the classical algorithm and the proposed algorithm are compared. The results indicate that the proposed algorithm is 3.4 times more efficient than the traditional non-uniformity correction algorithm. This paper evaluates the effect of the raw image and the two algorithms on the image correction using residual non-uniformity. Multiple integration times (0.6 ms, 3 ms and 3.5 ms) are used to simulate the continuous change of integration. The results indicate that the residual non-uniformity of the proposed algorithm is consistent and the corrected image has been effectively corrected.
To address the bottleneck that makes the conventional polarization spectral imaging method difficult to apply to the ballistic platform, a fast multi-dimensional imaging guidance optical system based on array optics is proposed. The correlation model between channel resolution and telescopic magnification is constructed. The precise matching and efficient utilization of the parameters of the microlens array, spectral filter array, and micro-nano-polarization array detector are realized. Based on the conventional guidance head and commercial polarization detector, a multi-dimensional imaging guidance optical system with spherical dome is designed. The system adopts a 4×4 optical field segmentation layout, forming 16 spectral channels through the visible light band with a spectral resolution of 16 nm. A polarization spectral data cube in four polarization directions, such as 0°, 45°, 90°, and 135° is acquired efficiently under the conditions of a single optical path and a single detector. The system has an effective focal length of 150 mm and a structure length of 145 mm. Simulation results show that the full-field modulation transfer function of the system is close to the diffraction limit at the Nyquist frequency for 16 channels. The imaging quality meets the requirements of bullet-loaded target multi-dimensional detection and identification.
Quantum Fisher information is used to witness the quantum phase transition in a non-Hermitian trapped ion system with balanced gain and loss, from the viewpoint of quantum parameter estimation. We formulate a general non-unitary dynamic of any two-level non-Hermitian system in the form of state vector. The sudden change in the dynamics of quantum Fisher information occurs at an exceptional point characterizing quantum criticality. The dynamical behaviors of quantum Fisher information are classified into two different ways which depends on whether the system is located in symmetry unbroken or broken phase regimes. In the phase regime where parity and time reversal symmetry are unbroken, the oscillatory evolution of quantum Fisher information is presented, achieving better quantum measurement precision. In the broken phase regime, quantum Fisher information undergoes the monotonically decreasing behavior. The maximum value of quantum estimation precision is obtained at the exceptional point. It is found that the two distinct kinds of behaviors can be verified by quantum entropy and coherence. Utilizing quantum Fisher information to witness phase transition in the non-Hermitian system is emphasized. The results may have potential applications to non-Hermitian quantum information technology.
In order to improve the image quality and variable range of focal length of liquid lens, by using dielectrophoretic and hydraulic driven, the double-interface liquid lens based on combination structure is designed, which mainly consists of dielectrophoretic double-liquid lens and PDMS membrane liquid lens. Firstly, the liquid lens model is established with Comsol software, the surface profile changes of droplets and PDMS membrane under different voltages are studied, then the surface profile data of two surfaces are derived. Secondly, the aspherical expression is used to fit with Matlab software, the interface profiles of droplets and PDMS membrane under different voltages and the corresponding aspherical coefficient are obtained. Finally, the corresponding double-interface combined liquid lens optical model is built with Zemax software, the image plane is selected as Gaussian image plane, then through the fabrication and the preliminary experimental research of the corresponding device, the simulation and experimental data are compared and analyzed. The results show that the variable range of focal length of the designed double-interface liquid lens based on the combined structure of the simulation is consistent with that of the experiment. Additionally, the zoom ratio can reach
With its advantages of high torque ratio and stable low-speed operation, the Segmented Arc Permanent Magnet Synchronous Motor provides high-performance drive technology support for large-diameter astronomical telescope observations. Due to the existence of other internal and external interferences such as parameter distortion, harmonics, etc. during the operation of the motor, it is a challenge to improve the performance of the motor. To this end, this paper proposes an integral sliding mode controller based on a new reaching law and a hybrid control strategy that combines an expanded state observer and a load observer, aiming to optimize the traditional sliding mode control and enhance the anti-interference ability of the system. The parameters of the traditional reaching law are complicated and cannot suppress chattering well. The new reaching law simplifies the parameters and effectively overcomes the system chattering. Secondly, an expanded state observer is used to estimate the feedback speed, and then the q-axis current information and the estimated precise speed data are combined as the input of the load torque observer, which further improves the load observation performance and converts the load observation value into current for pre-processing. Feedback compensation is used to improve the anti-interference performance of the motor. Simulation and experimental results show that the proposed dual observer method can accurately observe the motor's speed and load, significantly enhancing the motor's ability to resist load disturbances; at the same time, the new sliding mode speed controller used reduces the motor speed overshoot, and suppresses the buffeting of the sliding mode to a certain extent, providing theoretical and experimental support for arc motors in high-precision observation applications of large-aperture astronomical telescopes.
First, mathematical models for the dual grating interference system and the wavefront segmentation of the optical wedge array were established, and a parameter design method for non-imaging optical systems under paraxial conditions was proposed. Then a one-dimensional high-precision angle measurement system was designed. Finally, the measurement error of the system within the whole measurement range was analyzed and calculated.
The designed angle measurement system has a resolution of 0.02" in the paraxial region with a measurement range of [−5°, 5°]. The measurement error increases as the measurement range increases when the paraxial approximation condition is no longer satisfied. At the maximum measurement angle, the accuracy of the precision axis reduces to 0.42". The main source of measurement error is the precision positioning error caused by nonlinear changes in the phase of interference fringes.
The proposed model and parameter design method can be used to design an optical angle measurement system with high accuracy. The accuracy of the measurement decreases as the range of measurement increases. Simply increasing the subdivision factor of precise positioning cannot improve the accuracy of the measurement.
In order to precisely control the direction of laser beams, this paper analyzes the error caused by the grating tilt in the system based on the optical beam pointing algorithm of the dual liquid crystal polarization grating system. Firstly, a ray tracing method based on the diffraction grating equation is used to solve the outgoing beam pointing, introducing the incident beam pointing and grating tilt angle. The correctness and accuracy of this method are verified by comparing with simulation results. Secondly, by analyzing different situations of grating tilt, this article provides expressions for the grating attitude under different tilt conditions, and, in combination with the ray tracing method, obtains the expressions for the outgoing beam pointing for corresponding situations, analyzing the zeroing error and rotation error caused by grating tilt. The research results indicate that within the range of 0° to 0.3° grating tilt angle, the zeroing errors are within 0.25 mrad and 2 mrad respectively, and the rotation errors are around 85 mrad and 430 mrad respectively. This article describes a method for accurately calculating the pointing direction and grating tilt errors in the exit beam of a dual liquid crystal polarization grating system.
Beam arrays have great application value in free-space optical communication. The light intensity evolution and the on-axis scintillation index of radial Gaussian vortex beam array propagating through atmospheric turbulence are analyzed based on multi-phase screen simulation. The effect of initial beam parameters on the scintillation properties of radial Gaussian vortex beam array is studied, and the variation of the on-axis scintillation index values of radial Gaussian vortex beam array and a Gaussian vortex beam is compared. The results indicate that in the weak fluctuation regime, the on-axis scintillation index of Gaussian vortex beams remains within a numerical range of less than 1, while the on-axis scintillation index of radial Gaussian vortex beam arrays is around 1. In the medium fluctuation regime, the on-axis scintillation index of the radial Gaussian vortex beam array is smaller than that of a single Gaussian vortex beam. And the on-axis scintillation index of radial Gaussian vortex beam array decreases with the decrease of orbital angular momentum and the increase of radial array radius. The research results have certain theoretical significance and application value for vortex optical communication in turbulent atmospheric environments.
Liquid crystal optical phased array (LC OPA) is widely used in lidar, laser communication and laser weapons to scan and control laser beams. In order to realize the optimal design of LC OPA and high-precision control of laser beam, this paper focuses on the influence of working wavelength, number of pixels, pixel size and effective grey levels on beam pointing accuracy. Firstly, according to the principle of liquid crystal phase modulation, the effective scanning angle and diffraction efficiency of the period grating and the variable period grating methods are simulated and analyzed. Secondly, assuming the phase modulation is equally divided by the driving voltage, the variation law of the pointing error with the working wavelength, the number of pixels, the pixel size and the effective grey levels is simulated and analyzed, and the multivariable universal formula is derived. Thirdly, the pointing accuracy of the nonuniform phase modulation is simulated, analyzed, and compared with the results of the uniform phase modulation. Finally, the relationship between the effective grey levels and the pointing error is verified by experiments, and the validity of the empirical formula is preliminarily confirmed. The research results can provide a theoretical basis for the design of LC OPA.
In order to acquire and monitor the low frequency vibration signal, a two-dimensional vibration sensor with symmetrical circular flexure hinge is designed, which can work in the
In order to meet the needs of broad band, high diffraction efficiency and polarization independent, a double-layer trapezoidal polarization independent beam grating is proposed in this paper. Firstly, based on the strict coupled wave theory, a design model of polarimetric independent combined beam grating based on particle swarm optimization algorithm is established, and the efficiency characteristics are optimized by randomly generating characteristic wavelengths. Then, the effects of slot depth, width ratio, side Angle and other structural parameters on the diffraction efficiency and bandwidth of single-layer and double-layer trapezoidal grating are analyzed in detail. Finally, the electric field enhancement characteristics of the two structures are analyzed and discussed. The results show that the double-layer trapezoidal polarimetric beam independent grating achieves a theoretical diffraction efficiency of more than 99% in the bandwidth range of 51 nm (
Segmented mirrors co-phase error detection is one of the hot topics in current scientific research. Co-phase detection technology based on broad-band light source solves the problem of long measurement times caused by the Shackle-Hartmann method due to the low target flow rates, which improves the detection accuracy and range of piston error. However, in the application of the current broad-band algorithm, the complex environment and the presence of disturbing factors such as camera perturbations will cause the acquired circular aperture diffraction images to contain a certain amount of noise, which will lead to the correlation coefficient value being lower than the set threshold, and reduce the accuracy of the method or even make it ineffective. To tackle this problem, the paper proposes integrating an algorithm based on Denoising Convolutional Neural Network (DnCNN) into the broad-band algorithm in order to realize the control of the noise interference and retain the phase information of the far-field image. First, the circular hole diffraction image obtained using MATLAB is used as the training data for DnCNN. After the training, the images with different noise levels are imported into the trained noise reduction model to obtain the noise reduced image as well as the peak signal-to-noise ratios of the circular hole diffraction images before and after noise reduction and the structural similarity between the two and the clear and noiseless image. The results indicate that the average structural similarity between the denoised image and the ideal clear image has significantly improved compared to before processing, and this achieves an ideal denoising effect, which effectively increases the ability of broad-band algorithms to cope with the effects of high noise conditions. This study has strong theoretical significance and application value for exploring the broad-band light source algorithm for applications in practical co-phase detection environments.
In order to improve the communication quality of LEO-OGS laser link, commercial ground station telescopes equipped with large aperture primary mirror need to adapt to harsh outdoor temperature conditions.
A central support scheme based on room temperature vulcanized silicone rubber was proposed for a high-precision primary mirror with optical aperture of 500 mm. The structure consists of a Zerodur mirror blank, a pair of bushing and support made of titanium alloy, and a 1mm-thick adhesive layer which can effectively reduce the thermal stress inside assembly while temperature changes and unload the gravity of mirror blank. The thickness and height of the adhesive layer were determined by optimization. Specially designed fixture can accurately control the shape and thickness of the adhesive layer, meanwhile the ventilation holes on the bushing promote its full solidification.
Simulation indicates that the surface shape accuracy of primary mirror is 4.199 nm in RMS under 40 °C temperature variation, with 13.748 nm under vertical gravity, and 4.187 nm under horizontal gravity, accompanied by the maximum mirror inclination and displacement of 4.722" and 3.597 μm, and the fundamental frequency of the assembly reaches 53.45 Hz. The measured surface shape accuracy of primary mirror is RMS 0.017λ (λ=632.8 nm), after extensive heat cycling test and vacuum coating, the surface can maintain high-precision.
The central support structure can significantly improve the temperature adaptability of precise mirrors, and has broad application in large-scale ground optoelectronic equipment.
In order to adapt to the complex dynamic changing wake bubble field environment, the detection signal-to-noise ratio and detection rate of ship wake weak signal are improved, and the detection range is expanded.
In this paper, a detection method of ship wake weak signals based on synchronous accumulation method is proposed. By taking advantage of the repeatability of periodic signals and the randomness of noise, cumulative normalization is performed on successive periodic signals, which can effectively improve the detection signal-to-noise ratio and reduce the interference of random signals on detection performance. In order to evaluate the detection performance of the algorithm under multi-parameter coupling, a multi-time scale detection capability evaluation model for ship wake weak signals is established.
By conducting a large number of simulated ship wake detection experiments in indoor large pools and outdoor typical lakes, it is verified that the algorithm is suitable for the detection of sparse and discrete tiny far-field wake bubbles to large-scale near-field bubbles under high turbulence disturbance, thus realizing the full-time ship wake tracking and detection and effectively improving the underwater weapon strike capability.
It can provide support for ship wake laser detection and identification engineering practice.
Long-period fiber gratings have the advantages of small size, corrosion resistance, anti-electromagnetic interference, and high sensitivity, making them widely used in biomedicine, the power industry, and aerospace. This paper proposes a long-period fiber grating sensor based on periodic microchannels. First, a series of linear structures were etched in the cladding of a single-mode fiber by femtosecond laser micromachining. Then, the laser-modified region was selectively eroded by selective chemical etching to obtain the periodic microchannel structure. Finally, the channels were filled with polydimethylsiloxane (PDMS) to improve the spectral quality. The experimental results show that the sensor has good sensitivity in the measurement of various parameters such as temperature, stress, refractive index, and bending: it has a temperature sensitivity of −55.19 pm/°C, a strain sensitivity of −3.19 pm/με, a maximum refractive index sensitivity of 540.28 nm/RIU, and a bending sensitivity of 2.65 dB/m−1. All of the measurement parameters show good linear responses. The sensor has strong application prospects in the field of precision measurement and sensing.
Fourier transform spectroscopy (FTS) is an effective method for gas composition analysis and accurate measurement of concentration. However, in the process of analysis, the saturated absorption and weak absorption of the measured gas make the transmittance of some bands deviate from the stable range, which leads to the decrease of spectral signal-to-noise ratio and the nonlinear response of the instrument, and reduces the accuracy of concentration inversion.
In this paper, an adaptive multi-band joint concentration inversion algorithm is proposed, which combines the transmittance stable range and the spectral width threshold to adaptively select the effective band of the measured gas. The nonlinear least squares fitting method is used to invert the concentration of each effective band and the residual analysis is carried out to obtain the concentration inversion results and their weights of each effective band. The accurate quantitative analysis of the measured gas is realized by weighted average.
: The algorithm verification experiment is designed and carried out; the results show that the stability coefficient of the adaptive multi-band joint concentration inversion algorithm is 0.9976. Compared with the traditional single-band and multi-band concentration inversion algorithms, the root mean square error of the inversion results is reduced by 64.44% and 41.52%, the mean relative error is reduced by 65.97% and 46.72%, and the mean absolute error is reduced by 66.32% and 47.74% respectively,
the inversion accuracy and stability are significantly improved.
In order to enhance the continuous tunable range of a self-injection-locked laser frequency, a study is conducted on the variation relationship of the injected locking phase of the FP microcavity during the frequency-thermal tuning process.
Building upon traditional frequency thermotuning methods, this study explores the characteristics of frequency and phase parameters of a self-injection locked laser. We proposed an improved algorithm that integrates injection locking phase compensation and DFB chip current compensation during frequency thermotuning. Experimental validation of this algorithm was conducted on a Fabry-Perot (FP) micro-cavity self-injection locked laser. The laser operates at a wavelength of 1550nm with a 3dB linewidth of 785Hz, achieving frequency thermotuning of the FP micro-cavity using a pair of heating resistors.
The enhanced algorithm is implemented within the microcontroller program of the laser's original drive control circuit. No modifications are made to the hardware components of the laser. Ultimately, this implementation achieves a continuous frequency tuning range of 6 GHz.
This work provides a simple, efficient, and stable frequency tuning solution for self-injection-locked lasers, demonstrating high practicality and promising market prospects.
To mitigate reliance on operators during fundus imaging, an automated rapid localization and alignment method for the human pupil was proposed for visible light pupil imaging.
Initially, the pupil alignment device was constructed on the laboratory fundus imaging system using a visible light camera module and a three-axis motorized displacement stage.Subsequently, the effective area of the image was extracted using the Hough gradient method to determine the center of the fundus imaging system. The pupil region was identified through the maximum inter-class variance method and image histogram feature, while the center of the pupil was ascertained via the minimum circle fitting method. Ultimately, the electric displacement stage's movement is regulated through feedback mechanisms, ensuring that the center of the fundus imaging system aligns precisely with the pupil's center.
The experimental results show that the average recognition speed of human pupil is 0.11s, the average recognition accuracy of the pupil center is 98.7%, and the average Euclidean distance of the center deviation is 4.3 pixels.
It can satisfy the system requirements of the real-time and accuracy, and provides an efficient automatic pupil alignment solution for fundus imaging system.
Solar glint is a significant factor influencing sea surface target detection. For land observation platforms, a sea surface glint suppression method based on the reconstruction of common characteristics of linearly polarized images is proposed using the polarization characteristics of glints. The proposed method uses a focal plane polarization camera to obtain four-channel linear polarized images, calculates the scene’s polarization information, and generates a glint suppression image. Based on suppressing scene glint with polarization information combined with the characteristics of linear polarization images, the light intensity components of the glint suppression image are decomposed into common and characteristic components, and new weight factors are given to obtain the reconstructed glint suppression image. The results of field polarization experiments show that the maximum relative decrease in the proportion of saturated pixels in the reconstructed glint suppression image compared to the intensity image was 79.07%, and the maximum relative increase in spatial frequency and contrast were 73.77% and 172.73%, respectively. The method proposed in this paper effectively suppresses the glint noise in the sea scene and performs well in restoring background detail information.
The development of third-generation infrared focal plane detectors allows them to respond simultaneously to two different bands of infrared radiation, and the dual-band image brings great benefits to target detection and identification. In this paper, for aerial detection applications, adopting 320×256 dual-color infrared cooled detector, a large-magnification-ratio cooled infrared dual-band zoom optical system with operating bands of 3.7−4.8 μm in the midwave and 7.7−9.5 μm in the longwave has been designed for infrared detection of targets. The optical system adopts a combination of transmissive and refractive structures to realize an optical four-field-of-view switching wide-range zoom, and in order to meet the 100% cold diaphragm efficiency, a secondary imaging mode is adopted. The four-field focal lengths of the optical system are 32 mm, 200 mm, 800 mm, and 1600 mm, and the zoom ratio is 50×. The experimental results show that the optical system is close to the diffraction limit at a modulation transfer function eigenfrequency of 17 lp/mm in each of the dual-band zoom states. The optical system has the characteristics of dual-band, large zoom ratio, large zoom range, fast switching of multiple fields of view, simple and compact structure, and high-quality imaging, which will be widely used in the security fields such as searching, reconnaissance, and so on.
The anamorphic optical system is a relatively special optical system with bi-planar symmetry, whose structure gives rise to non-rotationally symmetric polarization aberrations. This thesis constructs a foldback anamorphic optical system. It also systematically analyzes the polarization aberration of this system and its effect on the point spread function, with the aim of providing a reference for the design of subsequent anamorphic optical systems.
Simulations of a folded-reversal anamorphic optical system based on a three-dimensional polarized light trace were performed to obtain detailed data on the polarization aberration and to compute the two-way attenuation and phase delay distribution characteristics of individual surfaces, as well as the Jones pupil, the amplitude response matrix, the point spread function, and the polarization crosstalk contrast of the system.
The maximum two-way attenuation is 0.145, and the maximum phase delay is 1.46×10−2 rad, both occurring at the secondary mirror position. The amplitude response function of the optical system with a 2∶1 anamorphic ratio has a 40.6% difference between the polarization crosstalk term in the long and short focal end directions, and the polarization crosstalk is limited by an order of magnitude of 10-6 for this anamorphic optical system contrast.
Polarization aberration in high-precision anamorphic optical systems is not negligible. The effects of polarization aberration can be reduced by film layer design and folded-back structure. The conclusions of this study can serve as a reference for designing anamorphic optical systems in deep space exploration and coherent communication systems.
In order to realize the industrial application of high-current pulsed electron beam on material surface modification, real-time tiny perturbation monitoring of the electron beam action process is needed. The electric field strength is one of the key parameters to reflect the characteristics of electron beam. The laser induced fluorescence-dip spectroscopy method based on Stark effect can realize the tiny perturbation measurement of electric field. Therefore, study the influence of laser power density on the electric field has important theoretical and application value for the parameter setting and result interpretation of similar electric field measurement methods.
By the theoretical analysis and calculation, the relationship model between excitation laser power density and the parameters of the test environment in the tiny perturbation state of electric field measurement is obtained; Then, based on the above relationship model and theoretical calculation, the influence of excitation laser power density on electric field measurement is verified experimentally.
The experimental results show that under the conditions that the tracer gas xenon pressure is 1.0×10-4 mbar and the electric field strength is 2 kV/cm or below, the excitation laser power density of tiny perturbations on the electric field measurement is 5 MW/cm2, which is basically consistent with the theoretical calculation value.
The research results provides the quantitative analysis method of the influence of laser power density on electric field in the laser induced fluorescence-dip spectroscopy method, and can be applied in the same kind of electric field measurement methods, providing the way for the setting of laser power density and experimental parameters, support the development of electric field measurement experiments, and effectively improve the accuracy of electric field measurement.
Phase delay mirrors were designed and prepared to regulate femtosecond laser systems’ group-delay dispersion (GDD). This paper systematically investigates the principle of compensating group-delay dispersion by phase-delay mirrors. Nb2O5 and SiO2 were used as the materials with high and low refractive indices. The group-delay dispersion curves were smoothed out by pairing the phase-delay mirrors with their complementary mirrors. The phase-delayed mirrors with phase modulation data of −800 GDD were prepared, and the reflectivity reached more than 99% in the range of 900 nm−1100 nm. The bandwidth adjustment problem of femtosecond laser systems is solved to meet the requirements of femtosecond lasers
Visual detection of sonar image is one of the important technologies in the field of resource exploration in complex waters and underwater foreign object target detection. Aiming at the problem of weak features and background information interference of small targets in sonar images, this paper proposes a weak feature confocal channel modulation algorithm for underwater sonar target detection. Firstly, in order to improve the model's ability to capture and characterize the information of weak targets, we design a weak target-specific activation strategy and introduce an a priori frame scale calibration mechanism to match the underlying semantic feature detection branch to improve the accuracy of small target detection; secondly, we apply the global information aggregation module to deeply excavate the global features of weak targets to avoid the redundant information from covering the small target's weak key features; lastly, in order to solve the problem of the traditional space pyramid Finally, in order to solve the problem of traditional spatial pyramid pooling which is easy to ignore the channel information, the confocal channel regulation pooling module is proposed to retain the effective channel domain small target information and overcome the interference of complex background information. Experiments show that the model in this paper achieves an average detection accuracy of 83.3% on nine types of weak targets in the underwater sonar dataset, which is 5.5% higher than the benchmark, among which the detection accuracy of iron bucket, human body model and cube is significantly improved by 24%, 8.6% and 7.3%, respectively, which effectively improves the problem of leakage and misdetection of weak targets in the underwater complex environment.
Aiming at the low accuracy of existing non-contact blood oxygen saturation measurement methods in dynamic head scenes, a denoising method based on improved adaptive noise complete set empirical mode decomposition and wavelet threshold is proposed to extract pulse wave signals with high signal-to-noise ratio. Firstly, in order to solve the problem of false components and mode aliasing in the early stage of decomposition and reconstruction, white Gaussian noise is added to the decomposition process to make it become an improved ICEEMDAN (ICEEMDAN), so as to reduce the residual noise in the modal components. Then, ICEEMDAN was used for mode decomposition of pulse wave signals of red and blue channels, and db8 wavelet basis function was used for 3-stage decomposition and reconstruction of components conforming to the spectrum range of blood oxygen, and the reconstructed signals were used for subsequent calculation of blood oxygen value. Finally, the experimental comparison and analysis of the blood oxygen saturation results measured in different dynamic head scenes show that the average error of blood oxygen saturation obtained in different head scenes is 0.73%, which is 1.93% lower than the average error of other algorithms. The denoising method proposed in this paper has good stability in different head scenes and can meet the needs of daily blood oxygen saturation measurement.
In order to improve the detection accuracy of Doppler asymmetric spatial heterodyne (DASH) interferometer in harsh temperatures, an Opto-mechanical-thermal integration analysis was carried out. Firstly, the correlation between the interference phase and temperature is established according to the working principle and the phase algorithm of the interferometer. Secondly, the optical mechanical thermal analysis model and thermal deformation data acquisition model are designed. The deformation data of the interference module and the imaging optical system at different temperatures are given by temperature load simulation analysis, and the phase error caused by thermal deformation is obtained by fitting. Finally, based on the wind speed error caused by thermal deformation of each component, a reasonable temperature control scheme is proposed. The results show that the interference module occupies the main cause, the temperature must be controlled within 20±0.05 °C, and the temperature control should be carried out for the temperature sensitive parts, and the wind speed error caused by the part is 3.8 m/s. The thermal drift of the magnification of the imaging optical system and the thermal drift of the relative position of the imaging optical system and the detector should occupy the secondary cause, which should be controlled within 20±2 °C, and the wind speed error caused by the part is 3.05 m/s. In summary, the wind measurement error caused by interference module, imaging optical system, imaging optical system and relative position of detector can be controlled within 6.85 m/s. The analysis scheme and temperature control measures presented in this paper can provide theoretical basis for DASH interferometer engineering applications.
为了提高压电定位系统(Piezo-positioning system)的控制性能,对迟滞特性产生的影响及其补偿控制方法进行了研究。利用Hammerstein模型表征压电陶瓷定位器的动态迟滞非线性特性,分别以Prandtl-Ishlinskii(P-I)模型和Hankel矩阵系统辨识法求得的模型表示Hammerstein模型的静态非线性部分和动态线性部分。此模型对于200 Hz以内的典型输入频率具有较好的泛化能力。提出了基于P-I逆模型与积分增广的滑模逆补偿跟踪控制策略,实验结果表明,相较于PID逆补偿控制和无逆补偿的滑模控制,滑模逆补偿控制具有更加理想的阶跃响应,无超调且调节时间仅为6.2 ms,在频域内系统闭环跟踪带宽达到119.9 Hz,且扰动抑制带宽达到86.2 Hz。所提控制策略实现了迟滞非线性的有效补偿,提高了压电定位系统的跟踪精度与抗扰性能。
There is nonradiative recombination in waveguide region owing carrier leakage, which in turn reduces output power and wall-plug efficiency. In this paper, we designed a novel epitaxial structure, which suppresses carrier leakage by inserting n-Ga0.55In0.45P and p-GaAs0.6P0.4 between barriers and waveguide layers, respectively, to modulate the energy band structure and to increase the height of barriers. The results showed that leakage current density reduced by 87.71%, compared to traditional structure. The output power reached 12.80 W with wall-plug efficiency of 78.24% at an injection current density 5 A/cm2 at room temperature. In addition, temperature drift coefficient of center wavelength was 0.206 nm/°C at the temperature range from 5 to 65 °C. The novel epitaxial structure provides a theoretical basis for achieving high-power laser diode.
The photonic integrated interferometric imaging system generally adds single-mode fiber arrays at the focal plane of the subaperture, and completes the large-field-of-view splicing imaging by receiving beams with different field-of-view angles, but the direct use of fiber arrays leads to the discontinuity of the imaging field-of-view, the focal length of the subaperture becomes longer, and the thickness is increased substantially. To address the above problems, this paper proposes a combination of microlens arrays and fiber optic arrays to subdivide the subaperture image plane to achieve a seamless splicing of the field of view, and through the combination of the telephoto objective lens and the three-lens spatial compression plate significantly reduces the overall thickness of the subaperture array. The design results show that by adding 65*65 microlens array in front of the fiber array to focus the beam twice to achieve the system field of view seamless splicing, the field of view is expanded 65 times, the full field of view is 0.0489 °, the efficiency of spatial optical coupling in the center of each fiber in the single-mode fiber array is not less than 40% when the visible light is incident, and after adding the spatial compression plate to compress the free-space light path, the overall thickness of the system achieves one order of magnitude compression. The system in the realization of photonic integrated interference imaging system large field of view seamless splicing imaging at the same time, for the solution of the problem of ultra-long focal length lens thickness is too large to provide a new way of thinking.
The study systematically analyzes the impact of various parameters such as laser repetition frequency, pulse duration, average power, water jet pressure, repeat times, nozzle offset, focal position, offset distance between grooves, and processing speed on the surface morphology of stainless steel. The findings reveal that micro-groove depth increases with higher laser power but decreases with increasing jet pressure and processing speed. Interestingly, repeat times have minimal effect on depth. On the other hand, micro-groove width increases with higher laser power and repeat times but decreases with processing speed. By optimizing these parameters, the researchers achieved high-quality pound sign-shaped trap structures with consistent dimensions. We tested the secondary electron emission coefficient of the "well" structure. The coefficient is reduced by 0.5 at most compared to before processing, effectively suppressing secondary electron emission.
Laser communication utilizes light waves as the transmission medium. It offers many advantages, including high data rates, expansive bandwidth, compactness, robust interference resistance, and superior confidentiality. It has the critical capability to enable high-speed transmission and secure operation of space information networks. Prominent research institutions have committed to studying a series of challenges that need to be solved in the process of networking laser communication technology, including point-to-multipoint simultaneous laser communication, all-optical switching and forwarding of multi-channel signals within nodes, node dynamic random access, and network topology design. Numerous demonstration and verification experiments have been conducted, with a subset of these research results finding practical applications. Based on the analysis and discussion of space laser communication networking technology, this paper summarizes the development of laser communication networking technology both domestically and internationally, focusing on the application of laser communication networking technology in the fields of satellite constellations, satellite relays, and aviation networks; furthermore, it presents a review of pertinent domestic research methodologies, experimental validations, and technical solutions; finally, it predicts the development trend of laser communication networking technology and applications.
With the rapid advancement of spectral imaging technology, the use of multispectral filter array (MSFA) to collect the spatial and spectral information of multispectral images has become a research hotspot. The uses of the original data are limited because of its low sampling rate and strong spectral inter-correlation for reconstruction. Therefore, this paper proposes a multi-branch attention residual network model for spatial-spectral association based on an 8-band 4 × 4 MSFA with all-pass bands. First, the multi-branch model was used to learn the image features after interpolation in each band; second, the feature information of the eight bands and the all-pass band were united by the spatial channel attention model designed in this paper, and the application of multi-layer convolution and the convolutional attention module and the use of residual compensation effectively compensated the color difference of each band and enriched the edge texture-related feature information; finally, the preliminary interpolated full-pass band and the rest of the band feature information were used in feature learning by residual dense blocks without batch normalization on the spatial and spectral correlation of multispectral images to match the spectral information of each band. Experimental results show that the peak signal-to-noise ratio, structural similarity, and spectral angular similarity of the test image under the D65 light source outperform the state-of-the-art deep learning method by 3.46%, 0.27%, and 6%, respectively; in conclusion, this method not only reduces artifacts but also obtains more texture details.
The Terahertz wave possesses characteristics of high penetration, low energy, and fingerprint spectrum, etc., making it widely used in the detection field. Therefore, developing a Terahertz wave detection optical imaging system holds substantial significance and wide application prospects. Firstly, we refer to the structure of Tessar objective lens, which consists four lenses. The balance equations of aberration for the system were established through the application of the aberration theory of the paraxial optical system. Subsequently, we provide a solution function and method of the initial structure parameters of the system. Then, we combine it with optical design software to further correct the aberration of the system. Finally, we design a Terahertz wave detection optical imaging system with a large aperture. The optical system consists of four coaxial refractive lenses with a total focal length of 70 mm, an F-number of 1.4, and a full field of view angle of 8°. The value of modulation transfer function (MTF) in the range of full field of view angle is greater than 0.32 at the Nyquist frequency of 10 lp/mm, and the root mean square (RMS) radius of the diffused spot in each field of view is less than the airy disk radius. Finally, the paper analyzes and discusses the various tolerance types of the system. The results indicate that the Terahertz wave detection optical imaging system, designed in this paper, has a large aperture, a simple, compact form, a lightweight structure, excellent imaging performance and simple processing, which meets the design requirements, and it has important applications in the field of high-resolution detection and other fields within the Terahertz wave band.
Brain glioma is a common type of brain tumor with a low cure rate and a high recurrence rate. Precise identification of tumor boundaries is an important prerequisite for reducing recurrence and improving prognosis. Developing a rapid, high-sensitivity and label-free diagnostic method is of crucial clinical significance regarding glioma. Raman spectroscopy can reflect substance’s chemical and structural information at the molecular level due to its fingerprint characteristics. It has already shown excellent prospects for the location and identification of glioma. Firstly, we introduce the different types of Raman spectroscopy technologies in this paper. Secondly, the research status of glioma diagnosis based on Raman spectroscopy is reviewed. Finally, the future development of glioma diagnosis through Raman spectroscopy is prospected.
Hydroxyl (OH) is a widely existing product in the combustion reaction process. In combustion diagnosis technology, the two-dimensional spatial distribution based on hydroxyl is commonly used to characterize the structure of the flame front. Hydroxyl is an important parameter in characterizing the flame temperature, flame surface density, and heat release rate. The effective detection of hydroxyl in combustion flame is an important support for exploring the evolution of combustion dynamics and revealing the mechanism of random flame events. Planar laser-induced fluorescence (PLIF) has several advantages as an optical measurement method: high spatial and temporal resolution, non-intrusiveness, and component selection. PLIF has successfully observed the structure of various combustion flames, such as Bunsen burner flame, turbulent flame, swirl flame, and supersonic flame, which provides an important reference for establishing combustion models. This paper starts with the basic principle of PLIF detection, followed by the development history and research status of PLIF technology in the field of combustion diagnosis. Then, it introduces the PLIF ultraviolet light source technology based on dye laser, optical parametric oscillation, and Ti:sapphire tripling-frequency, and discusses the characteristics of different technical routes. Finally, it prospects the development of UV laser technology for OH-PLIF.
Narrow linewidth lasers are the basic components of spectroscopy, precision metrology, and other experiments. Because diode lasers are very sensitive to external optical feedback, the phase noise of diode lasers, can be suppressed by using a high optical feedback bandwidth, enabling the narrowing of the linewidth. In the paper, we use fiber Bragg grating (FBG) as a feedback element and builds a long external cavity feedback loop. In order to reduce the influence of temperature fluctuation of external environment and air flow disturbance, the temperature of the optical fiber is controlled. Then, the maximum temperature fluctuation within 1 hour is reduced from 0.039 °C to 0.003 °C. In addition, the effect of feedback bandwidth on laser linewidth is also tested. Although the bandwidth of the FBG used in the experiment is much larger than the free-running laser linewidth, a narrowing of the laser linewidth is still observed. The smaller the FBG bandwidth, the narrower the laser linewidth. For this phenomenon, we believe that there should be a negative feedback mechanism in the feedback loop, which can stabilize the laser linewidth to a certain slope of the feedback spectrum. Therefore the narrower the feedback bandwidth of the fiber grating, the larger the slope of the feedback spectrum, and the more sensitive the feedback. In addition, by changing the feedback power of FBG in the range of 0~1 mW, it is observed that at the reflected power of 0.8 mW, the optical feedback narrows the laser linewidth from the free-running 100.5 kHz to the narrowest 11.5 kHz, and phase noise in the range of 0.2 kHz to 2 MHz is reduced by about 20 dB.
This paper reports a 4.7-μm mid-wave infrared quantum cascade laser based on double active region structure with a ridge width of 9.5 μm, which can achieve continuous single transverse mode operation at room temperature. By inserting 0.8-μm InP, the original single active region is transformed into a double active region structure, which can significantly reduce the peak temperature of the device's active region and suppress the generation of higher-order transverse modes. At a temperature of 288 K, the device with a double active region structure with a cavity length of 5 mm has a threshold current density of 1.14 kA/cm2, a continuous output power of 0.706 W, a fast axis divergence angle of 27.3°, and a slow axis divergence angle of 18.1°. Compared with conventional devices with a single active region structure, the devices with a double active region structure have no degradation in their maximum optical output power and show a significant improvement in the beam quality in the slow axis direction of the device. These results provide a solution to the problem of the slow axis beam quality of high-power mid-wave quantum cascade lasers.
Traditional cleaning methods can not clean small pollution particles on the surface of cultural relics. Moreover it can easily cause irreversible damage. In order to improve the ability to clean pollutants, laser cleaning technology has been gradually applied to the cleaning of different types of cultural relics. In this paper, we develop a nanosecond laser cleaning system to clean the simulated marble samples and marble fragments in the Palace Museum. The object of the cleanout is black crust pollutants. To avoid the yellowing effect, a dual wavelength combination of
The coal-fired boiler combustion process's economic, safety, and environmental performance holds great significance when constructing smart power plants. In coal-fired boiler combustion, H2S and CO are the two main high-temperature corrosive gases. They not only corrode the boiler near the wall surface but also pose severe harm to the atmospheric environment through their exhaust gases. Based on the near-infrared tunable diode laser absorption spectroscopy technology, combined with wavelength modulation spectroscopy and frequency division multiplexing technology, an unstaffed online real-time monitoring instrument for H2S and CO gas concentrations in the main combustion zone of coal-fired boilers was developed. Gas absorption spectroscopy in the
Laser beam quality is one of the key indicators to measure the application performance of laser. To meet the application requirements of long-distance optoelectronic countermeasures, we cany out the research on the design of unstable resonators and beam quality improvement techniques for non-chain pulsed deuterium fluoride (DF) lasers. Three sets of positive branch virtual confocal unstable resonators with different magnifications are designed. An inner cavity unstable resonator with two support structures of convex mirror, transverse support and longitudinal support, are constructed. The transverse support structure is equipped with a circulating water-cooling channel. Using 86.5% surrounding energy to define laser beam diameter, the laser beam quality is evaluated with beam quality factor
In this study, we propose an active polarization imaging method based on laser illumination to tackle the issue of low target detection contrast in strong light backgrounds, which is a challenge in conventional photoelectric detection. Through constructing a laser incident bidirectional reflection distribution model, a laser incident polarization bidirectional reflection distribution model and a target surface polarization model of laser illumination, the coupling relationship between the polarization characteristics of three typical target materials and the divergence angle of a laser beam is analyzed. Backlight observation experiments are conducted in a controlled darkroom to verify the impact of the scattering angle of the laser beam on the polarization characteristics of the target. The experimental results show an 86.11% increase in target contrast for active polarization imaging under strong light background compared to traditional passive intensity imaging. Additionally, the visible polarization characteristics of different target materials vary with different divergence angles, and the line polarization of metallic materials is higher than that of non-metallic materials. The experimental results are in good agreement with the theoretical analysis. The outdoor solar backlight observation experiment verifies the applicability of the research method in high-intensity light and long-distance settings. This study can lay a theoretical foundation for improving accurate target perception under a strong light background.
In order to solve the problems of low image exposure, low contrast and difficulty of feature extraction in real-time animal monitoring at night, we proposed a lightweight self-supervised deep neural network Zero-Denoise and an improved YOLOv8 model for image enhancement and accurate recognition of nocturnal animal targets. The first stage of rapid enhancement was performed by lightweight PDCE-Net. A new lighting loss function was proposed, and the second stage of re-enhancement was carried out in PRED-Net based on the Retinex principle and the maximum entropy theory, using the original image and fast enhancement image corrected by the parameter adjustable Gamma. Then, the YOLOv8 model was improved to recognize the re-enhanced image. Finally, experimental analysis was conducted on the LOL dataset and the self-built animal dataset to verify the improvement of the Zero-Denoise network and YOLOv8 model for nocturnal animal target monitoring. The experimental results show that the PSNR, SSIM, and MAE indicators of the Zero-Denoise network on the LOL dataset reach 28.53, 0.76, and 26.15, respectively. Combined with the improved YOLOv8, the mAP value of the baseline model on the self-built animal dataset increases by 7.1% compared to YOLOv8. Zero-Denoise and improved YOLOv8 can achieve good quality images of nocturnal animal targets, which can be helpful in further study of accurate methods of monitoring these targets.
To address the issues of blurred edge details and poor contrast in multi-scale transform fused images obtained using remote sensing detection methods for mixed background features, an image fusion method that combines the sparse representation of non-downsampled contour wavelet transform and a guided filter is utilised to enhance the quality and visual appearance of the fused images. This method involves several steps: firstly, a multi-scale and multi-directional decomposition is performed on both spectral and polarimetric images using non-downsampled contour wavelet transform to isolate the feature information in each subband; secondly, the low-frequency subbands are fused using a sparse representation to minimize the loss of contrast in the fused image; additionally, the high-frequency subbands are fused through a bootstrap filter to enhance the detail information and the contours of the image; finally, the low-frequency and high-frequency fusion coefficients are inverted using non-downsampled contour wavelet inversion to generate the final fused image. Analysis results indicate that the contrast of the fused image is improved by up to 54.5% and 15.4% respectively compared to the original spectral image and the polarimetric image, making it easier to distinguish objects in shadows under a mixed background. This method is used to fuse spectral and polarimetric images captured by a polarimetric spectral imager at different wavelengths, which resulted in true-colour reproduction. These true-colour restored images demonstrate that this fusion method retains environmental information within the mixed background while distinguishing the object from the background, effectively improving the image quality of polarization spectral remote sensing detection imaging. This method can enhance the integrity and authenticity of image information in polarization spectral remote sensing detection imaging, thereby expanding its application scope in remote sensing detection of complex environments and image recognition.
Triangular mesh model registration is an important part of industrial automation detection software. The registration accuracy has an important influence on mechanical parts' shape and position tolerance. Aiming to solve the problems of low accuracy and poor robustness of the automatic registration of triangular mesh models, we propose a segmentation method for enhanced features in the automatic registration of triangular mesh models for mechanical parts. First, the K value of the feature segmentation of the triangular mesh model was determined, and the Laplacian matrix determined the seed points for iterative initialization. Second, the appropriate region shape agent and cost function were used to accelerate the process and perform multi-source iterative clustering to obtain the intended feature segmentation results. Finally, based on the feature segmentation results of the triangular mesh model, the coarse registration based on the singular value decomposition method was performed, then the fine registration was performed according to the EM-ICP. The experimental results show that the proposed method reduces registration error by 25.2% and shortens the automatic registration time by 62.6%, compared with the traditional feature descriptor coarse registration combined with ICP fine registration method. This effectively improves the accuracy and efficiency of the automatic registration of the triangular mesh model.
Teaching scans are cumbersome and have poor versatility when performing scan reconstruction. Viewpoint planning has continued to focus on automatically obtaining the minimum set of viewpoints covering the model. To realize automated 3D scanning and reconstruction of parts with different complexity levels, we study issues such as viewpoint redundancy, viewpoint occlusion, and binocular reconstruction constraints that may occur during viewpoint planning. First, given the difficulty of completely scaning the model with existing viewpoint planning, Lloyd's algorithm is improved by analyzing the characteristics of surface structured light scanning and the energy function of Euclidean distance and normal vector deviation is applied to perform Voronoi partitioning of the model to generate an initial scanning viewpoint. Then, to address the viewpoint redundancy problem, an iterative algorithm for splitting the initial scanning viewpoints is proposed. Finally, given the problem that the generated viewpoints are prone to occlusion, a line-of-sight de-occlusion strategy is proposed. Moreover, to improve the model coverage, a method of using panning viewpoints is proposed. The experimental results show that under the optimal number of viewpoints, the coverage rate of automobile castings and shells reaches more than 94%, and that of the simple curved automobile sheet metal reaches more than 99.5%, and automatic planning and scanning of the automotive steering knuckle is realized. Planning scanning meets the coverage and efficiency requirements of automatic viewpoint planning and the adaptability requirements for parts with different complexity levels.
In order to meet the requirements of the national synchrotron radiation source, the anisotropic wet-etching technology of monocrystalline silicon grating with small blazed angle is studied, and the blazed grating suitable for the medium wave soft X-ray band is prepared. Based on the rigorously coupled wave theory, the structural parameters and process tolerance of the small blazed angle grating are designed. In the crystal alignment process, the crystal orientation of the silicon wafer is determined by ring-preetching, and then the grating mask is aligned with the crystal direction of monocrystalline silicon <111> based on the frequency doubling adjustment method. At the same time, the effect of the photoresist ashing technique and the active agent on the groove quality of the grating is investigated, and the scintillating gratings close to the ideal sawtooth groove shape are successfully prepared by the monocrystalline silicon anisotropic wet etching process. The experimental results show that the blazed angle of the prepared grating is 1°, the linear density is
In the digital grating displacement measurement technique, the CMOS pixel array of the camera is regarded as a ‘digitized’ grating. The micron-scale grating images can realize nanoscale displacement measurements by constructing the period difference between optical grating and digital grating. Combined with the detection light path of oblique incidence, it can be applied to the lithography machine’s focusing and leveling sensor to measure the wafer surface height accurately. In the actual measurement, the unexpected patterns on the wafer surface interfere with the reflection imaging of the optical grating, then affect the image processing results. In this paper, a process adaptability method for digital grating displacement measurement is proposed, which reconstructs the light intensity and recovers the light intensity curve from the CMOS image when interference patterns exist. The proposed method shows good stability when the large area pattern appears on the wafer substrate, and can adapt to multiple surface defects such as scratches, particles, stains and grooves. The experimental results show that the mean square error of the light intensity curve is significantly reduced and the method’s
Focusing on the visible polarization reflection characteristics of typical target materials surfaces, the polarization bidirectional reflection distribution function model based on the improved Blinn masking function was established considering the effects of specular reflection, diffuse reflection and volume scattering, which maked up for the defect of traditional "V" masking function. The physical parameters of the target materials were inverted by genetic algorithm, and the visible light polarization characteristics of four target materials, namely polypropylene, 99 alumina ceramic, iron and green painted aluminum, were simulated. Experimental tests validate the model’s accuracy. Results indicate that at an incidence angle of 50°, relative azimuth angles of 90°−270°, and detection angles of 0°−60°, the improved model reduces the root mean square error (RMSE) by 70.61% to 24.73%, with a minimum RMSE of 0.0129. Significant polarization is observed at relative azimuth angles of 120°−240°. The larger the ratio of the real part to the imaginary part of the complex refractive index of the four materials, the greater the peak value of the degree of polarization. In the visible light band, the wavelength has little effect on the degree of polarization. These findings provide theoretical data supporting the understanding of polarization characteristics in typical target materials.
For revealing the microphysical mechanism of the formation and development of the cloud-ground lightning channel, the radial structure and optical radiation characteristics of the cloud-ground lightning channel were studied. We carried out field observation experiments in the Qinghai Plateau region using a slit-less high-speed spectrograph. The clearly visible channel core was recorded in a cloud-ground lightning, and a weak luminescent region was found between the outer edge of the channel core and the external luminescent channel. Based on the spectral observation results, the optical radiation characteristics of the first return stroke and the third subsequent return stroke were compared and analyzed. The corona sheath model of the lightning channel was verified experimentally, the location of the connection point was determined. The estimated striking distance of the two return strokes is 57 m and 53 m respectively, and the strongest point of the return discharge is confirmed at the connection point. It can be inferred that in the initial stage of the return stroke, the cloud ground lightning return stroke channel consists of the channel core , the weak luminescence region and the outer corona sheath from the inside to the outside, that is, the charge distribution along the radial direction of the lightning channel is uneven. The light radiation characteristics of lightning channel are closely related to the intensity and duration of discharge.
To investigate the impact of ghost images on optical system performance, we develope a Modulation Transfer Function (MTF) calculation model under the influence of ghost images generated by secondary reflection. We first introduce the analyzing and describing method of ghost image using the paraxial approximation. Then, starting from the definition of the MTF, and considering the influence of ghost image irradiance on the modulation of the image plane, an MTF calculation model under the influence of ghost images is constructed. By conducting a case study calculation on a system and comparing it with the simulation results, it is found that the maximum mean square error is less than
Monocentric multiscale systems offer the advantages of miniaturization and a large field of view. In order to further realize the miniaturization and light weight of the large field-of-view system, we adopt the Galileo-type monocentric multiscale system form and design a monocentric multiscale system operating in the visible spectrum. The modulation transfer function of the system is greater than 0.3 at a frequency of 208 lp/mm, the root-mean-square radius of the full-field diffuse spot is smaller than the detector pixel size of 2.4 μm, and the imaging quality is close to the diffraction limit. The monocentric multiscale system structure has a couple of special characteristics: the relay lenses are closely arranged and the crosstalk stray light between the relay lenses seriously affects the imaging quality. To solve the problem, we apply the method of suppressing the crosstalk stray light with the built-in stary light stop. On the basis, we carry out the simulation and analysis of the stray light of the optical system. Analysis results show that the stray light coefficients are all reduced to less than 1×10−6 after the addition of the stray light stop, which verifies the crosstalk stray light suppression method.
To mitigate the impact of clouds on sea surface texture analysis in marine remote sensing images, this paper studies the removal of cloud interference using an information entropy-low-pass-filter combined mask. Initially, we analyze the fundamental principles and limitations of the existing remote sensing image declouding algorithms, highlighting their unsuitability for applications requiring high fidelity. Subsequently, we propose a cloud interference removal technology based on information entropy-low-pass filtering combined mask. This technology encompasses destriping procedures with improved moment matching for remote sensing images, local information entropy filtering, and joint low-frequency filtering as correction parameters for each pixel in the images. The algorithm is characterized by low complexity and high time efficiency. Experimental results demonstrate that, compared to existing algorithms, the proposed method significantly enhances texture detail information in thin cloud areas and cloud edges while maintaining low computational complexity. It achieves an image information entropy over 7.8, a contrast ratio exceeding 60, and a mean gradient above 200. In comparisons of image details, the proposed algorithm enhances texture details without introducing artifacts or non-uniformities, thereby meeting the high-fidelity requirements for remote sensing applications.
Aiming at the wavefront detection without an ideal point beacon in the adaptive optical system under the strong turbulent environment, we proposed a method to detect the optical field information of extended beacons using a Plenoptic sensor. The optical field imaging principle, wavefront phase reconstruction algorithm, and error influence rule of extended beacons were studied. The imaging process of the extended beacon on the optical field sensor was simplified through the equivalence method, and the optical field images were rearranged in a specific way. The image cross-correlation and Zernike mode methods were used to realize the wavefront reconstruction of the 0° field of view. Simulation studies were conducted on error-influencing factors such as different input aberration coefficients, the number of single-row microlens elements, and noise. The results show that when the input aberration is less than 6.5 λ, the wavefront reconstruction accuracy is about 0.08 λ. For the image detector with an image resolution of 1080×1080 and pixel size of 5.5 μm, the wavefront reconstruction accuracy is the highest when the number of single row microlens units is between 40 and 50, and the system noise hardly affects the accuracy. Finally, an extended beacon wavefront detection system was built to reconstruct the four aberrant wavefronts of 0° field of view by detecting the extended beacon. The wavefront reconstruction accuracy of the experimental system is about 0.04 λ, which meets the wavefront detection requirements of the adaptive optical system.
Shared secret-key extraction from random channel characteristics is an effective approach to ensuring the physical layer security of atmospheric optical channels. The secret-key generation rate and disagreement rate are two issues that attract a lot of attention. Using the random characteristics of atmospheric turbulent optical channels as a shared source of randomness, a secret-key extraction scheme for multiple-input multiple-output (MIMO) atmospheric optical channels is proposed. The alternative singular value decomposition is used to decompose the channel matrix; the correlation between the two channel characteristic sequences obtained by the two legitimate parties is enhanced through a simple moving average, and the single-threshold interleaved quantization is performed on the channel characteristic sequences after moving average. The two legitimate parties generate random controlling sequences for coding mapping based on differential diversity values, in order to implement encoding mapping for the single threshold interleaved quantization results of the channel characteristic sequences. The experimental results show that our scheme’s initial key disagreement rate can reach 4.5×10−5 at a signal-to-noise ratio of 30 dB, and that the generated random bit sequences have passed the National Institute of Standards and Technology (NIST) randomness test. The results are useful in the implementation of secret-key extraction from atmospheric MIMO optical channels.
Bright-field imaging can provide cellular and histological morphological information, while fluorescence imaging can provide expression information of key proteins. Dual-mode correlation imaging that combines both techniques is used for examining tissue samples in medical and scientific research. However, in clinical, correlation imaging often relies on adjacent tissue sections for observation. This can result in inconsistencies at both the tissue structure and the cellular level, which is problematic when the sample volume is limited, the number of cells on the slices is sparse, or precise point-to-point morphological information is required. In this study, we present a sample preparation method that enables both Hematoxylin and Eosin (H&E) staining and immunofluorescence staining on a single tissue section, enabling dual-mode imaging. We focused on optimizing the decolorizing process and the immunofluorescence restaining protocol, comparing three decolorization methods (hydrochloric acid ethanol, acetic acid-oxalic acid, and potassium permanganate-oxalic acid) and three antigen retrieval methods (EDTA, Tris-EDTA, and citric acid). By analyzing the signal-to-noise ratios (SNR) of images obtained under different conditions, we found that the combination of acetic acid-oxalic acid decolorization with EDTA antigen retrieval produced the best quality immunofluorescence images. Additionally, we successfully fused brightfield and fluorescence images, providing more comprehensive tissue morphology and immunological information on a single section.
As the pulse contains rich blood flow information of the human body, detecting the pulse and deducing the health status of human cardiovascular system are becoming a hot spot. In this study, PbS quantum dots with a size of 3 nm were synthesized using the hot injection method, and a PbS quantum dot photodetector was constructed on the surface of gold forked finger electrode through spin coating. Based on the prepared PbS quantum dot photodetector, a data visualization pulse detection system was developed. Using the optoelectronic capacitance pulse wave recording method, the same tester was measured under different exercise states and different testers were measured under the same exercise state. The measured data was displayed on the electronic display screen through circuit processing. The results show that under the illumination of 15.2 μW·cm−2 light intensity, its responsivity (
A widely-wavelength-tunable Brillouin fiber laser (BFL) with improved optical signal-to-noise ratio (OSNR) based on parity-time (PT) symmetric and saturable absorption (SA) effect is present. This novel BFL realizes PT symmetry and SA effect through polarization-maintaining erbium-doped fiber (PM-EDF) Sagnac loop, which is composed of a PM-EDF, a coupler and two polarization controllers (PCs). By using the inherent birefringence characteristic of PM-EDF, two feedback loops in orthogonal polarization state are formed when the Strokes signal in injected. One of these loops provides gain in the clockwise direction with in the Sagnac loop, while the other loop generates loss in the counterclockwise direction. By adjusting the PCs to control the polarization state of the PM-EDF, a single-longitudinal-mode (SLM) BFL can be achieved, as the PT symmetry is broken when the SA participating stimulated Brillouin scattering (SBS) gain and loss are well-matched and the gain surpasses the coupling coefficient. Compared to previous BFLs, the proposed BFL has a more streamlined structure and a wider wavelength tunable range, at the same time, it is not being limited by the bandwidth of the erbium-doped fiber amplifier while still maintaining narrow linewidth SLM output. Additionally, thanks to SA effect of the PM-EDF, the PT symmetric SBS gain contract is enhanced, resulting in a higher optical signal-to-noise (OSNR). The experimental results show that the laser has a wide tunable range of
The data simulation for Space Situational Awareness (SSA) can provide critical data support for the development, testing, and validation of space surveillance equipment and situational awareness algorithms (including detection, tracking, recognition, and characterization of space object), playing a significant role in building SSA capabilities. Taking the optical data simulation for space-based situational awareness as the research subject, the purpose and main research content of SSA data simulation are presented, and the typical research methods and processes of SSA optical imaging simulation are set forth. The current research status and progress in domestic and foreign related research are introduced, covering the imaging modeling and simulation achievements of different optical sensing systems such as binocular vision sensors, LiDAR, infrared sensors, visible light telescopes, and star trackers. The development trend of SSA data simulation research is analyzed, providing reference for future research ideas and approaches of SSA data simulation.
Fringe structured light technology is a non-contact measurement method, which has developed rapidly in recent years and provides a new solution for on-machine detection in mechanical processing. However, the accuracy of structured light for on-machine detection is compromised by the convoluted lighting in machining environments and metal parts’ high reflectivity, leading to inaccurate measurements. Applying high dynamic range (HDR) technology to structured light detection can reduce the effect of high reflectivity, achieving the measurement of metal parts in complex scenes. This paper introduces the measurement principle of structured light and summarizes the challenges of on-machine detection for HDR structured light. Subsequently, this paper provides a comprehensive review of HDR structured light technology. In the context of on-machine detection of mechanical processing, the HDR technology based on hardware equipment and the HDR technology based on stripe algorithm are discussed and analyzed, respectively. Following this, different technologies are summarized according to the requirements of on-machine detection. The advantages and disadvantages of various methods are presented, and the applicability of on-machine detection is compared. Finally, the potential applications are analyzed, and the technological prospects will be proposed in combination with the research hotspots of advanced manufacturing technology and precision measurement in recent years.
Laser Induced Breakdown Spectroscopy (LIBS) is a new method for qualitative and quantitative analysis of the constituents of a material using plasma spectra produced by the interaction of a strong pulsed laser with the material. In the process of pulsed laser-induced plasma, different laser parameters (energy, pulse width, wavelength), environmental conditions during the detection process and the properties of the material itself have different degrees of influence on the physical mechanism of laser-induced plasma, which in turn affects the results of LIBS quantitative analysis. We review the physical mechanisms of LIBS technology in the current state, including the basic principles of LIBS, the differences in laser parameters, and the physical mechanisms involved in the differences in environmental and material properties. It provides a basis for a deeper understanding of laser-matter interactions and for improving the detection capabilities of LIBS.
Narrow linewidth fiber lasers, based on the multi-longitudinal-mode oscillator seed source, have obvious advantages in engineering applications and space-limited loading platforms. Additionally, they are considered ideal sub-modules for high-power spectral combinations. The time domain of this type of seed is unstable due to the self-pulse effect, causing significant spectral broadening and stimulated Raman scattering effects during the amplification process, which limits their further improvement in output power and affects the purity of laser spectra. In this paper, we introduce four commonly used narrow linewidth seeds. The mechanism and suppression methods of the self-pulse effect in multi-longitudinal mode oscillator seeds are analyzed. Critical technologies essential for the optimization and relevant progress of the multi-longitudinal-mode oscillator seed source and amplifier stages are discussed in detail. A future development outlook is also presented. This paper serves as a useful reference for the design of narrow linewidth fiber lasers based on the multi-longitudinal-mode oscillator seed source.
Optical path absorption spectroscopy is an important branch of absorption spectroscopy. In recent years, there has been a proliferation of optical path absorption spectroscopy techniques based on different light source technologies, absorption cavity technologies, and detection methods. As the demands on detection sensitivity and absorption optical path length increased, optical path absorption spectroscopy techniques based on the principle of enhanced absorption emerged, including integrated cavity spectroscopy (ICOS), cavity-enhanced absorption spectroscopy (CEAS) and cavity ring-down spectroscopy (CRDS). Enhanced absorption spectroscopy is advantageous for its high spectral resolution, high sensitivity, fast response time, and portability, but it presently lacks a unified concept and clear classification criteria. This paper compares the development history of absorption spectroscopy techniques and clarifies the concept of their multi-optical path. Based on whether resonant absorption occurs in the absorption cavity, the concept of absorption spectroscopy techniques based on resonance is proposed, and the current research status of resonant absorption spectroscopy techniques is analyzed and summarized, and the applications of this technique in various fields are outlined. Finally, the future development of key technologies in resonance absorption spectroscopy is envisioned.
Optical fiber tweezers are widely used in biochemical analysis, life sciences, and other fields due to their simple structure, flexible operation, and compact size. The hetero-core structure of the optical fiber probe possesses inherent advantages in near-field evanescent wave optical trapping force, core beam coupling transmission, and cross-synergistic application of microfluidic technology, which can realize the functions of cell and subcellular particle collection and transportation, and can significantly improve the three-dimensional particle trapping capability as well as dynamic manipulation level. In this paper, the structural characteristics and application technology research progress of optical fiber tweezers based on different core structures are reviewed. This paper sorts and compares key technologies, including probe preparation, laser source, and coupling mode, in hetero-core optical fiber tweezers systems. It also summarizes and provides a perspective on the role and development of hetero-core fibers with different structures in optical fiber tweezers.
Micro-LEDs offers the benefits of high brightness, high response frequency, and low power consumption, making them an attractive candidate for future display technologies and Visible Light Communication (VLC) systems. Nonetheless, their low External Quantum Efficiency (EQE) currently impedes their scaled mass production and further applications. In order to break through the bottleneck of low EQE, we conducted an analysis of Micro-LED external quantum efficiency’s contributing factors. The influencing factors for EQE are analyzed. It is concluded that the carrier loss and non-radiative recombination caused by sidewall defects are the main reasons for the decrease in EQE. In addition, we summarized the impact of sidewall defects on carrier transport and composites, and we also reviewed the commonly used sidewall treatment technology and repair methods, and pointed out that the existing sidewall treatment methods are helpful but insufficient for improving EQE, and the mechanism of carrier interaction with sidewall defects is not very clear. It is suggested to carry out a thorough and systematic study on the types and distribution of sidewall defects, the mechanism of carrier and sidewall defects, and the defect repair mode in the sidewall treatment process. Finally, future development trends are projected. This paper offers design ideas and theoretical foundations to enhance the external quantum efficiency and accelerate the process of commercialization and mass production of Micro-LEDs.
Polarization imaging, a novel photoelectric detection technology, can simultaneously acquire the contour information and polarization features of a scene. For specific application scenarios, polarization imaging has the excellent ability to distinguish different objects and highlight their outlines. Therefore, polarization imaging has been widely applied in the fields of object detection, underwater imaging, life science, environmental monitoring, 3D imaging, etc. Polarization splitting or the filtering device is the core element in a polarization imaging system. The traditional counterpart suffers from a bulky size, poor optical performance, and being sensitive to external disturbances, and can hardly meet the requirements of a highly integrated, highly functional, and highly stable polarization imaging system. A metasurface is a two-dimensional planar photonic device whose comprising units are arranged quasi-periodically at subwavelength intervals, and can finely regulate the amplitude and phase of the light field in different polarization directions. Polarization devices based on metasurface are featured with compactness, lightweight and multi-degree freedom, offering an original solution to ultracompact polarization imaging systems. Targeted at the field of polarization imaging, this paper illustrates the functional theory, developmental process and future tendency of related metasurfaces. We discuss the challenges and prospect on the future of imaging applications and systematic integrations with metasurfaces.
In order to clarify the cavity design methods of thin-disk multi-pass amplifiers, we summarize the different types of thin-disk multi-pass amplifiers and concludes that there are four fundamental design concepts: (1) 4
Miniature head-mounted single-photon fluorescence microscopy is a breakthrough approach for neuroscience research that has emerged in recent years. It can image the neural activity of freely moving vivo animals in real time, providing an unprecedented way to access neural signals and rapidly enhancing the understanding of how the brain works. Driven by the needs of brain science research, there have been many types of miniature head-mounted single-photon fluorescence microscopes, such as high-resolution imaging, wireless recording, 3D imaging, two-region imaging and two-color imaging. In order to have a more comprehensive understanding of this new optical neuroimaging technology, we classify its technologies according to the imaging field of view, introduce the characteristics of different types of micro-head-mounted single-photon fluorescence microscopes reported so far, and focus on the optical system scheme and optical performance parameters used. The advantages and disadvantages of different schemes are analyzed and compared and the future direction of development is described to provide reference for the practical application of brain science researchers.
Non-line-of-sight (NLoS) imaging is a promising technique developed in recent years, which can reconstruct hidden scenes by analyzing the information in the intermediate surface, and "see around the corner", and has strong application value in many fields. In this paper, we review the reconstruction algorithm for NLoS imaging tasks. Firstly, considering the crossover and non-independent phenomena existing in the NLoS imaging classification, we use the different features of physical imaging models and algorithm models to reclassify them. Secondly, according to the proposed classification criteria, we respectively review the traditional and deep learning-based NLoS imaging reconstruction algorithms, summarize the state-of-the-art algorithms, and derive the implement principle. We also compare the results of deep learning-based and traditional NLoS imaging reconstruction algorithms for reconstruction tasks. Finally, the current challenges and the future development of NLoS imaging are summarized. Different types of NLoS imaging reconstruction algorithms are comprehensively analyzed in this review, which provides important support for the further development of NLoS imaging reconstruction algorithms.
Laser-Induced Thermo-Elastic Spectroscopy (LITES) is a new developed gas detection technology based on the thermoelastic effect of Quartz Tuning Forks (QTF). The QTF has the advantages of low cost, small volume, high sensitivity and wide spectral response range, and the LITES is becoming a vital method for trace gas detection. In this paper, the basic principle of gas concentration measuring based on LITES is firstly analyzed. Secondly, from the perspective of various technical methods, this paper introduces the methods for improving the sensitivity of QTF detectors, and reviews the research progress of LITES system in recent years. The performance of these systems is evaluated by the signal amplitude, Signal-to-Noise Ratio (SNR), minimum detection limit, and Normalized Noise Equivalent Absorption (NNEA) coefficient. Finally, the practical application of LITES in the field of gas detection technology is briefly reviewed, and the methods for further improving its sensitivity are summarized and prospected.
Atmospheric temperature, humidity and pressure are deemed important atmospheric parameters. Quickly and accurately understanding the temperature, humidity and pressure information of the atmosphere and their changing trends is of great significance to research on meteorology, climatology, and artificial weather research. Raman lidar can obtain various atmospheric environment-related parameters by separating Raman scattering signal inversion, which can achieve high accuracy detection of atmospheric parameter profile information. Raman lidar has unique advantages and potential in atmospheric temperature, humidity and pressure detection. With an introduction to the principle and inverse analysis algorithm of Raman lidar for atmospheric temperature, humidity and pressure detection, this paper also highlights the advantages and disadvantages along with related advances of spectral devices such as filters, etalons and gratings commonly used in Raman lidar. The detection techniques involved in Raman lidar are also included. Finally, typical applications of meteorological parameter measurements by Raman lidar are shown.
With the continuous development of optical imaging technology and the growing demand for remote sensing applications, cross-scale high-resolution optical technology has been widely used in the field of remote sensing. In order to obtain more detailed information on the target, domestic and foreign researchers have carried out relevant research in different technical directions. In this paper, through the technical classification of remote sensing imaging, we introduce a representative aerospace optical remote sensing high-resolution imaging system. It focuses on monomer structure, block expandable imaging, optical interference synthesis aperture imaging, diffraction main mirror imaging, optical synthetic aperture and other technologies. It provides a new idea for the development of high-resolution optical remote sensing loads on the ground.
With the rapid development of laser technology, the application of laser in the medical field has gained growing attention. Due to its advantages of non-contact, high precision, low damage, portability and operational flexibility, laser treatment significantly enriches the clinical treatment toolkit. Moreover, it has substituted traditional methods for certain diseases and improved the overall medical treatment capability. Currently, laser treatment has gained increasing market share and has a great potential for even more widespread applications. Here, we introduce the laser treatment technique and the requirements of medical laser systems, expound the current status of the applications of laser treatment in clinical departments in a comprehensive manner, and give suggestions regarding to the problems in the laser treatment field in China.
Periodic optical systems, such as photonic crystals and optical metamaterials, can localize high-density electromagnetic field energy at subwavelength scales and obtain extremely small mode volumes, so they have great application potential in the field of light manipulation. In recent years, a strong interaction between light and matter in periodic optical systems has been discovered, which is called Bound States in Continuum (BIC). Optics BICs are special electromagnetic eigenstates whose frequencies lie in the radiation continuum but are completely localized, and have shown interesting physics and rich application scenarios. This paper systematically reviews the classification and theory of BICs in periodic optical systems, and summarizes their basic physical properties and the latest application development. BICs in periodic optical systems are injecting new impetus into the fields of integrated optics, information optics, bio-optics, topological optics, and nonlinear optics.
Two-dimensional (2D) Bi2O2Se has attracted broad attention in the field of electronic and optoelectronic applications in the UV-Vis-NIR region due to its unique crystal structure, energy band, high carrier mobility, and excellent stability. In this paper, we review the recent research progress in the material synthesis and optical characterization of Bi2O2Se. Firstly, the synthetic method and growth mechanism of 2D Bi2O2Se are introduced, including Chemical Vapor Deposition (CVD), wet chemical process, Molecular Beam Epitaxy (MBE) and Pulsed Laser Deposition (PLD), etc. Via steady-state spectrum study, the properties change of 2D Bi2O2Se with thickness change can be studied, such as the band gap. The defect type, temperature coefficient and thermal conductivity of 2D Bi2O2Se material can be further studied by focusing on the crystal vibration mode. Transient spectrum techniques can benefit the study of relaxation process and carriers transport properties in 2D Bi2O2Se materials. Finally, we summarize the existing challenges and application prospects for the promising Bi2O2Se field.
Panoramic endoscopic imaging technology can effectively reduce the observation blind area of internal organs. It has many advantages, such as shortening the operation time, reducing the risk of intraoperative bleeding, improving the prognosis and shortening the postoperative recovery time. It has important application value in minimally invasive surgery and preoperative examination. It is a research hotspot in recent years. This paper combs the panoramic endoscopic imaging technology from two aspects: principle and product applications. Firstly, various panoramic endoscopic imaging technologies based on two-dimensional and three-dimensional imaging are reviewed, their implementation methods are described, and their key indexes and performances are analyzed. Secondly, the capsule endoscope, panoramic enteroscope and other different types of products derived from panoramic endoscopic imaging technology are compared and analyzed, and the development trend and application prospect of panoramic endoscopic imaging technology are prospected.
Besides its advantages in volume, power and beam quality, a monolithic integration Master-Oscillation Power-amplifier (MOPA) can also realize a narrower linewidth and dynamic single-mode by integrating Bragg grating. Its application value is high in the fields of frequency doubling, pumping, optical communication and sensing, which makes it a popular research topic in recent years. This paper firstly went over the mainstream structure and characteristics of monolithic integrated MOPA, including a tapered amplifier, ridge amplifier, Bragg grating and three-section MOPA. Based on their working principles and performance characteristics, we introduce the main research directions and the latest development trends in combination with their problems. Aiming at the problem of beam quality degradation at high power in monolithic integrated MOPA, the optimal design of epitaxial layer structure, facet optical film and electrode aspects are then summarized for monolithic integrated MOPAs. After that, we sort out the research progress of MOPAs with different performance characteristics for various application requirements including high power, narrow linewidth, high beam quality and high brightness. Finally, we prospect the development trend of monolithic integrated MOPA.
Rare earth-doped upconversion luminescence nanomaterials have received considerable attention from researchers due to their great potential for applications in many fields such as information security, biomedicine, optical fiber communication, digital displays, and energy. The recently-developed upconversion luminescence nanoparticles with orthogonal excitation-emission properties have attracted especially strong research interest because their distinct luminescence outputs can be dynamically modulated by switching the excitation conditions. The orthogonal luminescence properties further endow such nanocrystals with a set of new features and functionalities, which largely expands their potential applications. This review summarizes the progress in the development of orthogonal upconversion luminescence of rare earth ions, and provides a systematic discussion on design principles and construction strategies of orthogonal excitation-emission systems based on core-shell structures, as well as introduces their recent advances in various fields of applications including data storage, security anti-counterfeiting, digital displays, sensing, bioimaging and therapy. Furthermore, the prospective opportunities and challenges in the future research of orthogonal luminescence systems are also provided.
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Supervisor: Chinese Academy of Sciences
Sponsors: the Changchun Institute of Optics, Fine Mechanics, and Physics (CIOMP), CAS
Editor-in-Chief: Wang Jiaqi, Academician
ISSN 2097-1842
CN 22-1431/O4
CODEN ZGHUC8
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