Lightweight and compact three-axis angle measurement method based on an optical wedge

In response to the issue that existing non-contact three-axis angle measurement methods are unsuitable for measuring the three-axis angles between the inner and outer ring frames of the fifth-generation airborne optoelectronic gimbal platform, this paper proposes a novel three-axis angle measurement method that utilises an optical wedge as a reflector and two PSDs as light spot receivers. This method offers advantages such as a compact structure, a wide measurement range, and fast measurement speed, making it capable of performing high-speed, non-contact three-axis angle measurements in confined spaces. The corresponding angle calculation model was derived based on the space vector analysis method. A ternary multiple regression equation was used to fit the errors of the angle calculation model, and the model was subsequently corrected according to the fitting results. Finally, a prototype was developed, and its angular measurement performance was validated through experimental testing. The experimental results indicate that within the measurement range of ±2° when the measuring distances are 8 mm, 10 mm and 12 mm, respectively, the RMS values of the measurement errors of the pitch angle α are 7.79^'', 12.05^'', and 10.73^'' respectively, the RMS values of the measurement errors of the yaw angle β are 6.45^'', 1.51^'', and 3.26^'', respectively, and the RMS values of the measurement errors of the roll angle γ are 28.39^'', 22.21^'', and 15.61^'', respectively.