Right‑Angle Prism The right‑angle prism is the most common reflective optical prism with a geometry of 45°‑45°‑90° isosceles right triangle. It is usually made of N‑BK7 (H‑K9L) or fused silica, with two perpendicular leg faces for light input/output and one 45‑degree hypotenuse reflective face. Light enters vertically through one leg face, undergoes total internal reflection on the hypotenuse, and exits from the other leg face, deflecting the beam by 90° and producing a mirrored image. It can also work in 180° retro‑reflection mode when light enters from the hypotenuse surface. Features: compact structure for folding optical paths. Anti‑reflection coatings can be applied on leg faces. If total internal reflection condition cannot be satisfied, reflective coating shall be deposited on hypotenuse. Applications: microscope, endoscope, machine vision, laser beam turning, rangefinders, binocular Porro prism assemblies, optical inspection instruments.