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.