Laser pointing error analysis and compensation method of low-power laser diode source applied to triangulation ranging system

The pointing drift and dither of the light source greatly reduces the measurement accuracy of the laser triangulation ranging system. In particular, for the low-power laser diode (LD) source, the temperature drift and the dither of the LD itself are more obvious. In this paper, the influence factors on the laser pointing error were analyzed by experiments and simulations based on the triangulation ranging system, and a combined optimization algorithm was proposed to compensate the pointing error. First, we built a platform for testing the directivity of low-power LD and analyzed the directivity drifting error caused by the change in LD temperature, the dithering error of the LD at constant temperature. In addition, the measurement error caused by the thermal deformation of the focusing lens was also analyzed in ZEMAX. Second, polynomial fitting was adapted to preliminarily correct the LD temperature drifting error, and the Kalman filter was introduced to further optimize the measurement results with the aim of improving both the absolute accuracy and repeatability of the laser triangulation ranging system. The experimental results showed that the measurement root mean square error was 0.91 µm and the repeatability was 0.61 µm after the pointing error was compensated by the method we proposed.