-
摘要:
为了研究全光相机对火焰等半透明介质的光场采样并优化全光相机的参数,基于近轴光学,建立了全光相机的逆向光线追迹模型。在此基础上,针对弥散介质沿采集方向的半透明特性,提出了像素采样锥形角以及物方采样角度等评价光线角度采样的性能指标,据此分析了全光相机像素和微透镜的位置对光场采样特性的影响,以及全光相机光学参数变化对光线方向采样性能的影响。结果表明:采集火焰辐射光场时,较小的微透镜直径有利于提高光场采样的单方向性,并减小主镜头入瞳直径,而较小的主镜头焦距有利于增大物方采样角度。
Abstract:To investigate the radiation sampling of the translucent media and optimize the parameters of a plenoptic camera, a backward ray tracing model is established based on the paraxial approximation in this paper. Considering the integrating properties along the sampling path of the translucent media, several indices for evaluating the angular sampling are then proposed such as cone angle of a single pixel and sampling angel of object side. The effects of the positions of the pixels and micro lenses of the plenoptic camera on the radiation sampling and the effects of the optical parameters of the plenoptic camera on ray direction sampling performance are analyzed. The results indicate that, for the light field sampling on flame radiation, a smaller diameter of the micro lens is useful for improving the accuracy of radiation sampling in certain direction and decreasing the size of main lens aperture. Moreover, smaller focal length of main lens is advantageous for improving the sampling angle of object side.
-
Key words:
- flame radiation /
- light field imaging /
- backward ray tracing /
- translucent media /
- angular sampling
-
表 1 全光相机参数
Table 1. Parameters of plenoptic camera
参数 数值 主镜头焦距fU/mm 50 微透镜焦距fs/μm 567 微透镜直径pm/μm 165 主镜头-微透镜距离bU/mm 52 物距a/mm 1 300 微透镜-CCD距离lm/μm 573 像素尺寸pp/μm 5.5 表 2 全光相机参数变化范围
Table 2. Variation range of parameters of plenoptic camera
参数 数值 主镜头焦距fU/mm 20~51.5 主镜头-微透镜距离bU/mm 50.5~200 微透镜焦距fs/μm 50~1 500 微透镜直径pm/μm 50~500 表 3 性能指标和光学参数的变化
Table 3. Variation of performance indices and optical parameters
参数 fU bU fs pm β NA - NA + ω - + - + D NA + - + a + - NA NA -
[1] 周怀春, 娄新生, 肖教芳, 等.炉膛火焰温度场图象处理试验研究[J].中国电机工程学报, 1995, 15(5):295-300. http://kns.cnki.net/KCMS/detail/detail.aspx?filename=zgdc505.001&dbname=CJFD&dbcode=CJFQZHOU H C, LOU X S, XIAO J F, et al.Experimental study on image processing of flame temperature distribution in a pilot-scale furnace[J].Proceedings of the CSEE, 1995, 15(5):295-300(in Chinese). http://kns.cnki.net/KCMS/detail/detail.aspx?filename=zgdc505.001&dbname=CJFD&dbcode=CJFQ [2] HOSSAIN M M, LU G, SUN D, et al.Three-dimensional reconstruction of flame temperature and emissivity distribution using optical tomographic and two-colour pyrometric techniques[J].Measurement Science and Technology, 2013, 24(7):074010. doi: 10.1088/0957-0233/24/7/074010 [3] ADELSON E H, WANG J Y A.Single lens stereo with a plenoptic camera[J].IEEE Transactions on Pattern Analysis and Machine Intelligence, 1992, 14(2):99-106. doi: 10.1109/34.121783 [4] BRISLEY P M, LU G, YAN Y, et al.Three dimensional temperature measurement of combustion flames using a single monochromatic CCD camera[J].IEEE Transactions on Instrumentation and Measurement, 2005, 54(4):1417-1421. doi: 10.1109/TIM.2005.851074 [5] SUN J, XU C, 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 [6] NG R, LEVOY M, BREDIF M, et al.Light field photography with a hand-held plenoptic camera[J].Computer Science Technical Report, 2005, 2(11):1-11. http://graphics.stanford.edu/papers/lfcamera/ [7] ZHANG C, CHEN T.View-dependent non-uniform sampling for image-based rendering[C]//Proceedings of the 2004 International Conference on Image Processing.Piscataway, NJ:IEEE Press, 2004, 4:2471-2474. http://ieeexplore.ieee.org/xpls/icp.jsp?arnumber=1421603 [8] GEORGIEV T, ZHENG K C, CURLESS B, et al.Spatio-angular resolution tradeoff in integral photography[C]//Proceedings of the Eurographics Symposium on Rendering Techniques, 2006:263-272. doi: 10.2312/EGWR/EGSR06/263-272 [9] SUREN J, ADITHYA P, SRIRAM S, et al.Depth fields:Extending light field techniques to time-of-flight imaging[C]//Proceedings of the International Conference on 3D Vision.Piscataway, NJ:IEEE Press, 2015:1-9. http://arxiv.org/abs/1509.00816v1 [10] JI Y, YE J, YU J.Reconstructing gas flows using light-path approximation[C]//IEEE Conference on Computer Vision and Pattern Recognition.Piscataway, NJ:IEEE Press, 2013:2507-2514. http://ieeexplore.ieee.org/xpls/icp.jsp?arnumber=6619168 [11] YANG Y, QIU T, LU G, et al.Recent advances in flame tomography[J].Chinese Journal of Chemical Engineering, 2012, 20(2):389-399. doi: 10.1016/S1004-9541(12)60402-9 [12] 孙俊, 许传龙, 张彪, 等.基于单光场相机的火焰三维温度场测量[J].工程热物理学报, 2016, 37(3):527-532. http://kns.cnki.net/KCMS/detail/detail.aspx?filename=gcrb201603014&dbname=CJFD&dbcode=CJFQSUN J, XU C L, ZHANG B, et al.Measurement of three-dimensional temperature field of flame based on a single light field camera[J].Journal of Engineering Thermophysics, 2016, 37(3):527-532(in Chinese). http://kns.cnki.net/KCMS/detail/detail.aspx?filename=gcrb201603014&dbname=CJFD&dbcode=CJFQ [13] LEVOY M, HANRAHAN P.Light field rendering[C]//Proceedings of the 23rd Annual Conference on Computer Graphics and Interactive Techniques.New York:ACM, 1996:31-42. [14] HAHNE C, AGGOUN A, HAXHA S, et al.Light field geometry of a standard plenoptic camera[J].Optics Express, 2014, 22(22):26659-26673. doi: 10.1364/OE.22.026659 [15] HECHT E.Optics[M].4th ed.Boston:Addison Wesley, 2001:93-95. [16] RICOLFE-VIALA C, SANCHEZ-SALMERON A J.Using the camera pin-hole model restrictions to calibrate the lens distortion model[J].Optics and Laser Technology, 2011, 43(6):996-1005. doi: 10.1016/j.optlastec.2011.01.006