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摘要:
针对彩色数字相机高成像质量以及高色准的需求，本文研究了基于Philips棱镜的3CMOS相机的光学系统设计以及相机光谱优化方法。通过对Philips棱镜进行光路建模，优化了棱镜的结构参数。在保证全内反射以及出射窗口大小的条件下，减小了系统的体积，并由此设计了Philips棱镜3CMOS相机光学系统。其视场角为45°，相对孔径为1/2.8，在110 lp/mm的奈奎斯特采样频率下，系统的MTF全视场全波段均大于0.4。基于色度学基本原理建立了Philips棱镜相机的矢量成像模型，分析了由光线入射角度变化造成的薄膜光谱偏移，提出了宽光束下光谱偏移的修正模型。利用该模型设计并优化了相机中的4组光学薄膜。通过光路仿真实验以及色差分析，基于优化后的相机光学系统的平均色差降低了15.8%，像面颜色不均匀性降低了60%。结果表明：本文设计的光学系统拥有良好的成像质量，优化后的相机光谱实现了良好的颜色性能以及颜色均匀性。
Abstract:According to the demand for high imaging quality and high chromaticity in color digital cameras, we investigated the optical system design and camera spectral optimization methods of 3CMOS cameras based on Philips prisms. By constructing the model of the optical path of the Philips prism, the structural parameters of the prism were optimized. The volume of the system was reduced while ensuring total internal reflection and exit window size. Based on this method, the Philips prism 3CMOS camera optical system was designed, with a field of view angle of 45 ° and a relative aperture of 1/2.8. The system's MTF was greater than 0.4 in the full field of view and full band at Nyquist sampling frequency of 110 lp/mm. Subsequently, based on the fundamental principles of chromaticity, a vector imaging model for Philips prism cameras was established. The problem of thin film spectral shift caused by changes in light incidence angle was analyzed, and a correction model for spectral shift under wide beam conditions was proposed. Four sets of optical thin films in the camera were designed and optimized using this model. Through optical path simulation experiments and color error analysis, based on the optimized camera spectrum, the average color error of the system was reduced by 15.8%, and the color non-uniformity of the image plane was reduced by 60%. The results indicate that the designed optical system has good imaging quality, and the optimized camera spectrum achieves good color performance and uniformity.
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Key words:
- optical design /
- 3CMOS camera /
- colorimetry /
- camera spectral optimization
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图 8 简化的宽光束薄膜光谱计算模型
Figure 8. Calculation model of simplified broad beam thin film spectral
图 9 优化中使用到的(a) 24色卡样本、(b)样本反射率、(c)光源光谱以及(d)颜色匹配函数
Figure 9. (a) 24 color checker samples, (b) sample reflectance, (c) light source spectrum, and (d) color matching functions used in optimization
图 10 优化得到的(a)理想薄膜透过率以及(b)相机光谱
Figure 10. Optimized (a) ideal film transmittance and (b) camera spectra
图 11 (a)设计得到的基础薄膜光谱；(b)优化后的薄膜光谱
Figure 11. (a) Designed basic thin film spectrum and (b) optimized thin film spectrum
图 12 简化模型计算的(a)优化前和(b)优化后的相机光谱;蒙特卡洛光线追迹得到(c)优化前和(d)优化后的相机光谱
Figure 12. Camera spectra obtained from simplified model (a) before and (b) after optimization; camera spectra obtained from Monte Carlo ray tracing (c) before and (d) after optimization
表 1 光学系统设计指标
Table 1. Parameters of optical system
Parameter Value Field of view: 2ω 45° Focal length 35.5 mm F# <3 Distortion <1% Incident angle <6 degree MTF@110 lp/mm >0.3 
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表 2 Philips棱镜参数
Table 2. Philips prism parameters
Parameter Value α 25.1 mm β 12.9 mm L1 10.6 mm L2 8.1 mm L 44 mm θB 50.2° θR 50.9° DB 22.17 mm DR 22.15 mm D1 1.62 mm D2−DG 0.53 mm
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表 3 4组相机光谱的色差值
Table 3. Color errors of four sets of camera spectra
ΔE0 ΔE1 ΔE2 $\Delta {E'_{01}} $ $\Delta {E'_{02}} $ $\Delta {E'_{12}} $ ε Basic film，
SimplifiedAvg 0.248 0.460 0.777 0.457 0.673 1.105 1.017 Max 1.245 1.526 4.190 1.537 3.051 4.553 Basic film，
Monte CarloAvg 0.238 0.501 0.678 0.372 0.709 1.038 0.967 Max 0.865 1.471 4.557 1.149 3.937 4.992 Optimized film，
SimplifiedAvg 0.387 0.431 0.431 0.222 0.212 0.360 0.601 Max 1.577 1.667 1.579 0.851 0.804 1.299 Optimized film，
Monte CarloAvg 0.417 0.466 0.311 0.239 0.278 0.329 0.595 Max 1.522 1.629 1.401 0.987 1.111 1.152
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