Pentagonal prism is the beam Angle (90 °), one of the steering gear.It has two purposes: one is that no matter how much the first incident Angle on the side is the emergent light incident light steering Angle (90 °);The other is that, unlike a rectangular prism, the resulting image has neither rotation nor specular reflection.Pentaprism is commonly used in camera viewfinders, image observation systems or measuring instruments.
Characteristics of pentagonal prism is a 90 ° Angle of the light became a vertical incidence, and then after the 45 ° Angle of two surface reflection, from the Angle of 90 ° exit, on the other side of the incident light and emergent light is equal to 90 ° Angle, such application pentagonal prism can turn axis around 90 °. Recently, the use of the characteristics of a pentagonal optical prism measurement  the planarity of the Pacific Ocean, namely the pentagonal prism rotates around the horizontal axis for emergent light in the vertical plane sweep out a plane, and vice around the vertical axis rotation, can be measured in horizontal plane, when using laser as light source, because the laser range far, you can sweep out a big plane, this for housing construction, large engineering construction of planar measurement obviously is simple and convenient and of high precision, so the pentagonal prism needs more and more.
Pentagonal prisms cannot achieve internal total reflection based on the critical-angle principle. Therefore, the two reflective surfaces of this prism are generally coated with aluminum film and black paint, and the incident and outgoing surfaces are coated with MgF2 single anti-reflective coating.
|Flatness:||λ/4 @ 632.8nm|
|Bevel:||<0.25mm X 45°|
|Coating:||S1&S2: Single layer MgF2 coating|
|S3&S4: Aluminized and painted black|