激光与光电子学进展, 2014, 51 (12): 121201, 网络出版: 2014-12-02
采用二元编码的正弦光栅提高PMP测量速度和精度的方法 下载: 597次
Method for Improving Accuracy and Measurement Speed of PMP Using Error Diffusion Binary Encoded Sinusoidal Grating
相位测量轮廓术 DLP 投影仪 误差扩散 二元编码正弦光栅 phase measurement profilometry DLP projectors error diffusion algorithm binary encoding sinusoidal grating
摘要
利用误差扩散方法产生二元编码正弦光栅可以消除数字投影仪的非线性对投影光栅正弦性的影响,且能充分利用基于数字光处理技术(DLP)投影仪中数字微镜的二元高速开关特性,高速投影二元编码正弦光栅。投影仪分辨率不足会导致电子二元编码正弦光栅正弦性下降,从而影响测量精度。先对比了两种典型误差扩散编码算法:Floyd-Steinberg距离加权和Sierra Lite“蛇”形扫描获得的光栅的正弦性。然后针对目前DLP 投影仪产生频率较高的二元编码正弦光栅时,二元编码正弦光栅的正弦性较差的问题,提出了两种改善方法:1) 利用柱透镜卷积作用,在栅线方向上对二元编码正弦光栅进行平滑;2) 组合多帧具有不同微结构的二元编码正弦光栅,来减小二元编码正弦光栅的误差,保证相位测量轮廓术(PMP)方法的测量精度。所提方法充分利用了DLP 投影二值图像的高速特性,又明显改善了由于DLP 分辨率有限导致的二元编码正弦光栅的正弦性较差的问题,实验验证了这两种方法的有效性。
Abstract
Projecting a binary encoding sinusoidal grating calculated by the error diffusion algorithm can not only solve the problem of the effect on nonlinearity of a digital projector but also improve the projection speed by taking the advantage of binary high-speed switching characteristics of digital micro-mirror in digital light processing (DLP) projectors when a digital projector is used in the optical measurement system. As insufficient resolution of projector can degrade the quality of the electronic binary encoding sinusoidal fringe pattern, it influences the measurement accuracy further. Two typical encoding algorithms of error diffusion (Floyd-Steinberg distance weighted and Serpentine raster Sierra Lite) are firstly compared. Then, aimed at the problem that the quality of sinusoidal grating is not good enough to be suitable for the high accuracy measurement when high density binary encoding grating is projected by a DLP projector with lower resolution because of the less number of the sampling points in a grating period, two resolutions are proposed: One is that a cylindrical lens is introduced in the light path of the measurement system to smooth the resulted binary encoded sinusoidal grating along the grating line direction by the optical convolution operation of the lens. The other one is that superimpositing multi-frame binary encoding sinusoidal gratings with different microstructure is used to reduce the standard error of the binary encoding sinusoidal grating and guarantee the accuracy of phase-shift measurement method. The proposed method not only takes the advantage of high-speed characteristics of DLP projectors for projecting binary images, but also improves the sinusoidal characteristic of the binary encoding sinusoidalgrating caused by the limited resolution of DLP obviously. Simulations and experiments both verify the validity of the above two methods.
田紫霞, 陈文静, 苏显渝. 采用二元编码的正弦光栅提高PMP测量速度和精度的方法[J]. 激光与光电子学进展, 2014, 51(12): 121201. Tian Zixia, Chen Wenjing, Su Xianyu. Method for Improving Accuracy and Measurement Speed of PMP Using Error Diffusion Binary Encoded Sinusoidal Grating[J]. Laser & Optoelectronics Progress, 2014, 51(12): 121201.