A Novel Enhanced Roll-Angle Measurement System Based on a Transmission Grating Autocollimator

A resolution-enhanced roll-angle measurement system based on a transmission grating autocollimator is proposed. The measurement principle is analyzed in detail. The system uses a transmission grating and a mirror group to produce a pair of central symmetric differential measurement beams that enable the measurement of roll angle. Because the measurement beams transmit through the rotating grating twice, the resolution is enhanced compared to conventional grating autocollimation methods with the same device. The roll-angle resolution reached 0.1 arcsec. Additionally, the effect of laser beam drift on the stability of angular measurement is effectively suppressed by using differential measurement method, the stability of the proposed grating autocollimator after the differential measurement is 0.11 arcsec.