Light field volumetric particle image velocimetry
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摘要: 将光场三维成像技术与实验流体力学相结合,实现单相机对空间三维瞬态流场(3D3C)的精确测量,为流体力学实验研究提供了一种全新的测试技术。详细介绍了具有自主知识产权的光场相机硬件系统、基于乘积代数重建技术(MART)的粒子光场图像重构算法以及基于光线追迹的数字光场图像合成算法。利用DNS数字合成图像以及低速射流实验图像,将所发展的光场单相机三维流场测试技术(Light Field Particle Image Velocimetry,LF-PIV)与目前最成熟的三维流场测试技术层析PIV(Tomographic Particle Image Velocimetry,Tomo-PIV)进行对比研究分析。实验结果表明LF-PIV技术完全能达到与Tomo-PIV同等量级的测量精度。Abstract: A novel single camera volumetric velocity measurement technique is presented, which utilizes the advanced light field imaging technology to capture 3D PIV tracer particle images. The framework of Light Field Particle Image Velocimetry (LF-PIV) includes an in-house high resolution light field camera, multiplicative algebraic reconstruction technique (MART) based light field particle image reconstruction method and a ray tracing based synthetic light field particle image generation platform. The LF-PIV technique is compared with Tomographic Particle Image Velocimetry (Tomo-PIV) by using both synthetic DNS jet flow images as well as water jet experimental images. Results show that LF-PIV is capable of reconstructing the instantaneous volumetric velocity field with the accuracy similar to that of Tomo-PIV.
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Keywords:
- Light Field PIV /
- light field camera /
- single camera volumetric PIV /
- Tomo-PIV
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图 1 光场的2种参数化表示方式[29]
Fig. 1 Two methods of light field parameterisation
表 1 用于产生数字合成光场图像的光学参数数值
Table 1 Parameters for generating synthetic light field images
符号 意义 相机参数 合成图像参数 nlx MLA x方向分辨率 410 410 nly MLA y方向分辨率 310 310 pl 微透镜单元直径 77μm 77μm fl 微透镜焦距 310μm 310μm npx 相机x方向分辨率 6600pixel 6600pixel npy 相机y方向分辨率 4400pixel 4400pixel pp 像素直径 5.5μm 5.5μm fm 主镜头焦距 - 50mm pm 主镜头孔径 - 25mm So 物距 - 100mm Sl 相距 - 100mm M 放大系数 - -1 (f/#)m 主镜头f数 - 2 (f/#)l 微透镜f数 - 4 -
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