Laser coarse-fine coupling tracking by cascaded rotation Risley-prism pairs.

Rotation Risley prisms are increasingly used for laser tracking due to high precision and good dynamic performance. In this paper, a novel laser coarse-fine coupling tracking method based on two pairs of rotation Risley prisms is proposed to perform the forward and inverse tracking function. The second pair of rotation Risley prisms with narrower wedge angle can achieve higher precision tracking with narrower field of view than the first one, enriching the coarse-fine coupling tracking trajectory patterns. Moreover, an inverse algorithm based on the two-step method and Newton's iterative method is applied to solve the inverse issue for laser coarse-fine coupling tracking. Two cases further demonstrate that the motion switching strategy executed with the inverse solutions can steer the beam to track the desired motion trajectory. An experiment validates the availability of the cascaded rotation Risley-prism pairs to perform the laser coarse-fine coupling tracking function.