Research on multi-plane particle image velocimetry based on digital refocusing technology
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摘要:目的
光场相机在传统相机的CCD探测器前方增设微透镜阵列（Micro-lens Array，MLA），以同时捕获入射光线的空间信息和角度信息，可实现先拍摄、后对焦的数字重聚焦，进而获得物空间中任意深度平面的清晰对焦图像。为了获取三维流场中多个深度平面的速度场分布，
方法本文提出了一种基于逆向光线追迹数字重聚焦的多平面粒子图像测速技术（Particle Image Velocimetry, PIV）。为了实现光线追迹，本文重新推导了光场相机的
F 数匹配关系，计算了光场图像中子图像的渐晕区域和非渐晕区域，并通过逆向光线追迹技术，分别追迹渐晕区域和非渐晕区域发出的主光线，使其依次穿过微透镜阵列、主镜头并映射至三维物理空间，从而获得不同深度平面的粒子的重聚焦图像。随后，利用期望最大化 (Expectation-Maximization，EM)算法对重聚焦图像进行去模糊处理。最后，利用二维互相关技术计算三维流场中多平面的速度场分布。为了验证所提方法的有效性，搭建了淹没水射流实验装置并开展实验。结果实验结果表明，所提出的基于数字重聚焦技术的多平面PIV技术能实现三维流场中多平面速度场的测量。
Abstract:ObjectiveA light field camera incorporates a micro-lens array (MLA) in front of the CCD sensor to simultaneously capture both the spatial and angular information of the incident light rays, thereby enabling digital refocusing after image acquisition and generating sharply focused images at arbitrary depths in the object space. To achieve multi-plane velocity field measurements in three-dimensional (3D) flow fields,
Methoda multi-plane particle image velocimetry (PIV) method based on the backward ray tracing-based digital refocusing is proposed in this paper. First, the F-number matching relationship of the light field camera is re-derived to facilitate the implementation of the ray-tracing process. The vignetted and non-vignetted regions within the sub-images of the light field image are then calculated. Subsequently, backward ray tracing is employed to project the principal rays from different regions through the MLA and the main lens into the 3D physical space, thereby generating refocused particle images at different depth planes. Subsequently, the Expectation-Maximization (EM) algorithm is further applied to deblur the refocused particle images. Finally, the velocity field distributions at multiple depth planes are calculated using a two-dimensional (2D) cross-correlation algorithm. To validate the effectiveness of the proposed method, a submerged water jet experimental system is constructed and corresponding experiments are conducted.
ResultThe experimental results demonstrate that the proposed multi-plane PIV method based on the digital refocusing technique can achieve measurements of multi-plane velocity fields in 3D flow fields.
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Key words:
- particle image velocimetry /
- light field /
- digital refocusing technology /
- ray tracing /
- vignetting
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图 1 多平面2D PIV技术的原理示意图
Figure 1. Schematic Diagram of the Principle of Multi-Plane 2D PIV Technology
图 3 不同光场相机的F数匹配原理示意图
Figure 3. Schematic Diagram of F-Number Matching Principle for Different Light Field Cameras
图 5 子图像的渐晕和非渐晕示意
Figure 5. Schematic of the vignetting and non-vignetting of the sub-image
图 6 非渐晕区域的主光线的逆向光线追迹示意图
Figure 6. Schematic of the backward ray tracing of the chief ray in the non-vignetting region
图 7 渐晕区域的主光线的逆向光线追迹示意图
Figure 7. Schematic of the backward ray tracing of the chief ray in the vignetting region
图 9 淹没水射流的原始光场图像、重聚焦的粒子和去模糊的粒子图像
Figure 9. Examples of raw Light Field image, refocused particle image and deblurred image in the Submerged Water Jets
图 10 淹没水射流的多平面速度场分布
Figure 10. Multi-plane velocity field distribution of submerged water jets
表 1 Raytrix R29光场相机的光学参数
Table 1. Optical parameters of Raytrix R29 light field camera
d2
(mm)fm
(mm)fm1
(mm)fm2
(mm)fm3
(mm)f
(mm)l1
(mm)lv2
(mm)l′v2
(mm)lm
(mm)Pm
(mm)Px
(μm)Wx×Wy
微透镜数量Nx×Ny
像素数量1.317 - 1.936 1.626 2.335 100 - 200 200 193.07 0.1705 5.5 159×203 4320 ×6340 
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[1] 陈家成, 陈泰然, 梁文栋, 等. 收缩扩张管内液氮空化流动演化过程试验研究[J]. 力学学报, 2022, 54(5): 1242-1256. doi: 10.6052/0459-1879-21-614CHEN J CH, CHEN T R, LIANG W D, et al. Experimental study on the evolution of liquid nitrogen cavitating flows through converging-diverging nozzle[J]. Chinese Journal of Theoretical and Applied Mechanics, 2022, 54(5): 1242-1256. (in Chinese). doi: 10.6052/0459-1879-21-614 [2] 董亮, 张立新, 刘厚林, 等. 车用凸轮式氢气循环泵内非定常流动特性[J]. 排灌机械工程学报, 2022, 40(5): 433-439. doi: 10.3969/j.issn.1674-8530.20.0290DONG L, ZHANG L X, LIU H L, et al. Unsteady flow characteristics of cam type hydrogen circulation pump for vehicle[J]. Journal of Drainage and Irrigation Machinery Engineering, 2022, 40(5): 433-439. (in Chinese). doi: 10.3969/j.issn.1674-8530.20.0290 [3] 房兴龙, 杨伟平. 时序效应对双级涡轮非定常流场和性能的影响[J]. 风机技术, 2022, 64(2): 25-32. doi: 10.16492/j.fjjs.2022.02.0004FANG X L, YANG W P. Influence of clocking on the unsteady flow field and efficiency in a two-stage turbine[J]. Chinese Journal of Turbomachinery, 2022, 64(2): 25-32. (in Chinese). doi: 10.16492/j.fjjs.2022.02.0004 [4] ZHONG L J, LIU P L, HUA J X, et al. Experimental study on combustion characteristics and pressure oscillations of turbulent jet ignition in a confined space[J]. Combustion Science and Technology, 2023, 195(5): 958-981. doi: 10.1080/00102202.2021.1976768 [5] 李龙飞, 杨宝庆, 葛树宏, 等. 流场不均匀对液体火箭发动机纵向振荡燃烧影响及控制[J]. 航空动力学报, 2023, 38(1): 223-229. doi: 10.13224/j.cnki.jasp.20210356LI L F, YANG B Q, GE SH H, et al. Influence and control of non-uniform flow field on longitudinal combustion instability of liquid rocket engines[J]. Journal of Aerospace Power, 2023, 38(1): 223-229. (in Chinese). doi: 10.13224/j.cnki.jasp.20210356 [6] 孙俊. 基于光场成像的火焰三维温度场测量方法研究[D]. 南京: 东南大学, 2018.SUN J. Three-dimensional temperature measurement of flame based on light field imaging[D]. Nanjing: Southeast University, 2018. (in Chinese). [7] 李嘉, 李华聪, 张伟, 等. 高压燃油离心泵压力脉动及非定常流动分析[J]. 西北工业大学学报, 2022, 40(1): 199-205. doi: 10.3969/j.issn.1000-2758.2022.01.025LI J, LI H C, ZHANG W, et al. Transient flow structures and pressure pulsations of a high-pressure aero-fuel centrifugal pump[J]. Journal of Northwestern Polytechnical University, 2022, 40(1): 199-205. (in Chinese). doi: 10.3969/j.issn.1000-2758.2022.01.025 [8] KIM D, SHIN J, SON Y, et al. Characteristics of in-cylinder flow and mixture formation in a high-pressure spray-guided gasoline direct-injection optically accessible engine using PIV measurements and CFD[J]. Energy Conversion and Management, 2021, 248: 114819. doi: 10.1016/j.enconman.2021.114819 [9] DE SILVA C M, BAIDYA R, KHASHEHCHI M, et al. Assessment of tomographic PIV in wall-bounded turbulence using direct numerical simulation data[J]. Experiments in Fluids, 2012, 52(2): 425-440. doi: 10.1007/s00348-011-1227-7 [10] SCARANO F, POELMA C. Three-dimensional vorticity patterns of cylinder wakes[J]. Experiments in Fluids, 2009, 47(1): 69-83. doi: 10.1007/s00348-009-0629-2 [11] 曹丽霞, 张彪, 宋祥磊, 等. 聚焦光场成像三维粒子场重建方法[J]. 北京航空航天大学学报, 2017, 43(11): 2322-2330. doi: 10.13700/j.bh.1001-5965.2017.0068CAO L X, ZHANG B, SONG X L, et al. Reconstruction method of three-dimensional particle field based on focused light field imaging[J]. Journal of Beijing University of Aeronautics and Astronautics, 2017, 43(11): 2322-2330. (in Chinese). doi: 10.13700/j.bh.1001-5965.2017.0068 [12] FAN Q B, LIN P CH, TAN L, et al. Non-invasive and fully two-dimensional quantitative visualization of transparent flow fields enabled by photonic spin-decoupled metasurfaces[J]. Light: Science & Applications, 2025, 14(1): 113. [13] 巩子琦. 基于粒子图像测速技术的不同润湿性侧壁面气泡生长和上升行为研究[D]. 广州: 华南理工大学, 2024.GONG Z Q. Research on growth and rising behavior of bubbles on sidewalls with different wettability properties based on PIV[D]. Guangzhou: South China University of Technology, 2024. (in Chinese). [14] 朱海东, 马壮壮, 李虎, 等. 基于图像处理技术的消除双帧粒子图像背景反射研究[J]. 中国工程机械学报, 2025, 23(4): 601-605. doi: 10.15999/j.cnki.311926.2025.04.018ZHU H D, MA ZH ZH, LI H, et al. Research on elimination of background reflection in dual-frame particle images based on image processing techniques[J]. Chinese Journal of Construction Machinery, 2025, 23(4): 601-605. (in Chinese). doi: 10.15999/j.cnki.311926.2025.04.018 [15] 包全. 层析粒子图像测速技术几个关键问题研究及湍流边界层Tomo-TRPIV测量[D]. 天津: 天津大学, 2013.BAO Q. Research of several key problems in tomographic particle image velocimetry and turbulent boundary layer Tomo-TRPIV measurement[D]. Tianjin: Tianjin University, 2013. (in Chinese). [16] 李晓辉, 王宏伟, 黄湛, 等. 层析粒子图像测速技术研究进展[J]. 实验流体力学, 2021, 35(1): 86-96. doi: 10.11729/syltlx20190160LI X H, WANG H W, HUANG ZH, et al. Research advances of tomographic particle image velocimetry[J]. Journal of Experiments in Fluid Mechanics, 2021, 35(1): 86-96. (in Chinese). doi: 10.11729/syltlx20190160 [17] NG R, LEVOY M, BRÉDIF M, et al. Light field photography with a hand-held plenoptic camera[R]. Stanford: Stanford University, 2005. [18] 刘煜东, 许传龙, 孙俊, 等. 火焰辐射光场成像光线采样特性[J]. 北京航空航天大学学报, 2017, 43(11): 2207-2215. doi: 10.13700/j.bh.1001-5965.2017.0067LIU Y D, XU CH L, SUN J, et al. Characterization of ray sampling for flame radiation in light field imaging[J]. Journal of Beijing University of Aeronautics and Astronautics, 2017, 43(11): 2207-2215. (in Chinese). doi: 10.13700/j.bh.1001-5965.2017.0067 [19] FAHRINGER T W, LYNCH K P, THUROW B S. Volumetric particle image velocimetry with a single plenoptic camera[J]. Measurement Science and Technology, 2015, 26(11): 115201. doi: 10.1088/0957-0233/26/11/115201 [20] TAN Z P, JOHNSON K, CLIFFORD C, et al. Development of a modular, high-speed plenoptic-camera for 3D flow-measurement[J]. Optics Express, 2019, 27(9): 13400-13415. doi: 10.1364/OE.27.013400 [21] CAO L X, ZHANG B, LI J, et al. Characteristics of tomographic reconstruction of light-field Tomo-PIV[J]. Optics Communications, 2019, 442: 132-147. doi: 10.1016/j.optcom.2019.03.026 [22] SHI SH X, DING J F, NEW T H, et al. Volumetric calibration enhancements for single-camera light-field PIV[J]. Experiments in Fluids, 2019, 60(1): 21. doi: 10.1007/s00348-018-2670-5 [23] MEI D, DING J F, SHI SH X, et al. High resolution volumetric dual-camera light-field PIV[J]. Experiments in Fluids, 2019, 60(8): 132. doi: 10.1007/s00348-019-2781-7 [24] ZHU X Y, LU J X, HOSSAIN M, et al. Investigation of particle reconstruction quality for three-dimensional light field PIV[J]. Flow Measurement and Instrumentation, 2025, 104: 102888. doi: 10.1016/j.flowmeasinst.2025.102888 [25] ZHU X Y, HOSSAIN M, LI J, et al. Weight coefficient calculation through equivalent ray tracing method for light field particle image velocimetry[J]. Measurement, 2022, 193: 110982. doi: 10.1016/j.measurement.2022.110982 [26] ZHU X Y, ZHANG B, LI J, et al. Volumetric resolution of light field imaging and its effect on the reconstruction of light field PIV[J]. Optics Communications, 2020, 462: 125263. doi: 10.1016/j.optcom.2020.125263 [27] ZHU X Y, WU ZH A, LI J, et al. A pre-recognition SART algorithm for the volumetric reconstruction of the light field PIV[J]. Optics and Lasers in Engineering, 2021, 143: 106625. doi: 10.1016/j.optlaseng.2021.106625 [28] ZHU X Y, XU CH L, HOSSAIN M, et al. Approach to select optimal cross-correlation parameters for light field particle image velocimetry[J]. Physics of Fluids, 2022, 34(7): 073601. doi: 10.1063/5.0098933 [29] ZHU X Y, XU CH L, HOSSAIN M, et al. Fast and accurate flow measurement through dual-camera light field particle image velocimetry and ordered-subset algorithm[J]. Physics of Fluids, 2023, 35(6): 063603. doi: 10.1063/5.0153135 [30] 刘心爱, 孟娟, 杜海, 等. 基于ConvLSTM与LiteFlowNet架构的粒子图像测速方法[J]. 液晶与显示, 2025, 40(7): 1023-1035. doi: 10.37188/CJLCD.2025-0052LIU X A, MENG J, DU H, et al. Particle image velocimetry method based on ConvLSTM and LiteFlowNet architecture[J]. Chinese Journal of Liquid Crystals and Displays, 2025, 40(7): 1023-1035. (in Chinese). doi: 10.37188/CJLCD.2025-0052 [31] ZHU X Y, XU CH L, HOSSAIN M M, et al. Accurate weight coefficient estimation of multi-camera light field PIV through backpropagation neural network[J]. Measurement, 2024, 226: 114096. doi: 10.1016/j.measurement.2023.114096 [32] CAO L X, HOSSAIN M, LI J, et al. Three-dimensional particle image velocimetry measurement through three-dimensional U-Net neural network[J]. Physics of Fluids, 2024, 36(4): 047136. doi: 10.1063/5.0205872 [33] HALL E M, FAHRINGER T W, GUILDENBECHER D R, et al. Volumetric calibration of a plenoptic camera[J]. Applied Optics, 2018, 57(4): 914-923. doi: 10.1364/AO.57.000914 [34] PERWASS U, PERWASS C. Digital imaging system, plenoptic optical device and image data processing method: US, 8619177B2[P]. 2013-12-31. [35] SUN J, XU CH L, ZHANG B, et al. Three-dimensional temperature field measurement of flame using a single light field camera[J]. Optics Express, 2016, 24(2): 1118-1132. doi: 10.1364/OE.24.001118 [36] CAO L X, ZHANG B, HOSSAIN M, et al. Tomographic reconstruction of light field PIV based on a backward ray-tracing technique[J]. Measurement Science and Technology, 2021, 32(4): 044007. doi: 10.1088/1361-6501/abd281 -
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