The notable feature of pyramid prism is that for any incident light entering the aperture, no matter the incident angle, the light will be reflected back in the original direction. The angle error is determined by the machining accuracy of prism. Even if the angle of the pyramid prism is slightly changed in the measurement, the angle of the returned light will not change, and the light will return to the detector of the measuring instrument. Corner prism is often used in situations where light steering is difficult or difficult to control.