TIR retroreflector prisms consists of three mutually perpendicular right angled surfaces, and the incident light forms total reflection on the three right angled surfaces, reflecting the image or beam back to its initial direction through three reflections. It is not affected by the size of the incident angle, and even if the incident angle is not zero, it will reflect the incident light by 180 degrees. Its accuracy is represented by the angle error (parallelism) between the incident and outgoing light rays. Because it has this characteristic of being unaffected by alignment, they are very suitable for backward reflective optical systems.