Right-angle prism mirrors can deflect light and also be used to adjust the direction of an image. When light enters from one right angle surface of a prism, it undergoes total internal reflection at the glass/air interface of the inclined plane and exits from the other right angle surface; When light is incident from the oblique plane, it will be completely reflected on the right angled surface of the glass/air interface, and the second total reflection will occur on the next right angled surface. It is also possible to directly apply high reflectivity film or metal film on the inclined surface. Compared with ordinary flat mirrors, right angle prisms are easier to install and have better stability and strength.