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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.

A novel measurement system for a high-precision roll angle measurement of long working distance on the basis of two parallel beams in association with two detectors is presented. The measurement system consists of a light source part and a detecting part. The light source part uses transmission grating and a plane mirror to produce a pair of high-precision parallel beams. The nonparallelism of the dual beam caused by the installation error can be compressed to ensure the measurement system achieves high-precision measurement and long working distance. The effectiveness of the measurement system and proposed methods are demonstrated by a series of experiments. The resolution of 0.5′′ and measurement accuracy of 1.1′′ can be obtained by the set-up measurement system.

This article proposes a novel optical method for three-dimensional (3D) angle measurement. Using a simple and compact measurement system, the 3D angle can be determined simultaneously in real time based on geometric relation transformation and autocollimation. Additionally, the crosstalk error can be avoided between the three angles. In order to enable 3D angle measurement and simplify the system, a compact combined target with transmission grating and mirror group is designed. Theoretically, the relationship between the 3D angle and the light spot displacement on the PSD (position sensitive detector) has been deduced to demonstrate the possibility of this method. Practically, the verification experiments have been carried out to verify the feasibility of this approach, and the results fit well with the theoretical analysis.