High working distance and six-degree-of-freedom grating encoder based on lens batch collimation

In order to solve a series of application problems caused by the difficulty of adjusting prism collimation and the short working distance of small period gratings in current collimation solutions, this paper proposes a six-degree-of-freedom measurement scheme that uses a combination of large period gratings and long focus plano-convex lenses. This solution can achieve six degrees of freedom measurement at a working distance of more than 80mm. The main principle is that the displacement is calculated using the phase information formed by the interference of the four diffracted lights of the two-dimensional grating. The angle is based on the principle of autocollimation. According to the propagation direction of the diffracted light caused by the change of the grating diffracted light with the grating angle changes, thereby changing the angle obtained based on the location changes in the detected diffraction spot, ultimately forming a measurement of six degrees of freedom.