In order to ensure the optical index of the surface, The thickness of large-sized splitters will increase, In this way, in the process of splitting light, the reflected light from the back surface often interferes with the reflected light from the front surface. In order to eliminate the interference of the reflected light from the back surface, the large-size splitter is generally made into an optical wedge with a certain small angle, which makes the reflected light from the back surface deviate from the normal optical path at a certain angle.