Self-Calibration Method for Roll Angle Measurements of Dual Beams Based on Polarization

When dual beams are used to measure the roll angle, the angle between the double-collimated beams is easily disturbed by environmental changes, mechanical deformation, and other factors, which seriously affect measurement accuracy. The roll angle measured by the dual beam is sensitive to the spot position. By contrast, the roll angle measured by polarization depends on the polarization state of the incident light and is relatively less affected by laser angle drift. Therefore, to improve the accuracy of the roll error in five-degree- of-freedom measurements at long distances, a polarization- based roll angle optical path is proposed. The path is used to measure the roll angle of the sensor at different positions, calculate the angle between the dual beams, and perform calibrations, thus improving measurement accuracy. The test results show that in the measurement range of 0. 75.2. 00 m, the roll angle measurement error after compensation is reduced by 88. 97%. This meets the long-distance roll angle measurement requirements for high precision and easy installation.