Abstract:

In the laser communication terminal in space, the scanning trajectory on the CMOS camera is not orthogonal when the fine pointing mechanism of the 45° scanning mirror vibrates around different shaft systems, which reduces the scanning probability and makes it more difficult to calibrate the optical axis of the laser terminal in orbit. In order to solve this problem, the ray tracing method is used to establish a three-dimensional light vector scanning trajectory model, and the orthogonality of the light vector trajectory on the CMOS camera is calculated and simulated when the vibration axis of the 45° mirror scans along two sets of commonly used orthogonal axes. Then, an experimental test system is built to verify the performance of the reflected light vector in the scanning process of the fine pointing mechanism. The results show that: the non-orthogonality of the 45° scanning mirror vibrates around P=(1/2,-1/2, \sqrt{2}/2)^T and P'=(1/2,-1/2,- \sqrt{2}/2)^T is 19.47°, and the included angle of the scanning trajectory on the CMOS camera changes with the scanning angle according to the relationship between the scanning angle and the orthogonality curve of the scanning trajectory; the non-orthogonality of the scanning trajectory is 6.4 mrad when the scanning angle is 9 mrad. This study provides insights into the internal mechanism and has guiding significance for the installation mode and optical axis calibration of the off-axis field of view of the fine pointing mechanism of space laser communication terminal.

Key words: space laser communication, laser terminal, 45° scanning mirror, scanning, ray tracing