Incident angle measurement of collimated laser based on the pinhole principle

The incident angle of collimated laser is difficult to measure accurately within a large measurement range. A measurement method based on the pinhole principle, which is more accurate after modifying the lens distortion and focal length, was presented in this paper. The parameters which influence the accuracy, such as lens distortion coefficients and focal length, were analyzed using Monte Carlo method and corrected by experimental data to enhance the accuracy of angle measurement. The proto type based on the method was developed. Experiments show that the proto type gets an accuracy less than 0.006° in the entire measurement range of ±10°, which is in accord with theoretical predictions. The reliability of the measurement accuracy was also proved via repetitive experiments. The proto type can be widely used in many fields such as automatic controls of industrial robot and large engineering machinery.