机匣视窗折射对LDV聚焦的影响分析

为了分析激光束经过机匣视窗后聚焦状态的变化情况, 发展了一套通用程序, 可用于计算不同的测量条件下, 激光束穿过不同尺寸机匣视窗时的折射情况, 并对其结果的可信性进行了验证.利用所发展的程序, 以二维LDV探头为例, 分析了典型情况下蓝光、绿光焦点偏移情况, 以及蓝光与绿光焦点之间偏移量的变化情况, 并给出了确定焦点重合的计算准则.计算结果表明:如果不进行特殊的光学修正, LDV测量时必须要选取小的探头角度和浅的测点深度. 

Analysis of beam refraction effects in laser doppler velocimetry

A general mathematical program is developed in the paper to analyze the change of focus status after laser beams refracted at curved surface and to consider the displacement of focuses caused by refraction with various dimensions of window and various optical parameters.The creditability of the program has been validated and the associated parameters have been reviewed.The analyses of displacement of focus of blue beams,displacement of focus of green beams,and displacement between focus of green beams and focus of blue beams have been conducted in the case of two-dimensional laser doppler velocimetry(LDV) system,while a calculation criterion was presented to determine the superposition of focuses.The results demonstrated that small probe angle and shallow object depth should be essential in the case of lack of special optical correction.