News

Prisms are used to fold up optical paths, manipulate image orientations and sizes, and diffract light. In many applications, a combination of prisms are used to achieve several of these effects. In order to design assemblies containing multiple prisms , it is important to understand where light enters, travels, and exits through each prism, and it may also be important to understand the optical path length of the light as it travels through the prism.

A ray starts outside of the prism and enters via one of the faces. Inside the prism, the ray contacts another of the prism’s faces. If the ray strikes the new surface at an angle equal to or greater than the critical angle (associated with the refractive indices of the interfacial media), or if this surface is coated with an appropriate mirror coating, then the light will be totally internally reflected or almost totally and internally reflected. When the ray reflects off of this surface, the cross-section, representing the prism, is flipped over the line representing the reflecting surface of the prism, such that the ray appears to continue straight through the next cross-section without changing its original direction through the first cross-section. If the ray strikes at an angle that is not greater than or equal to the critical angle, and the surface is not mirrored, then the light will pass through this surface and exit the prism. 

Right Angle Prisms:

Ray deviation of 90° or 180°

Produce left-handed images due to a single reflection

Used in combination for image/beam displacement

Littrow Dispersion Prisms:

Ray deviation of 60° when coated

Produce right-handed images

Will disperse light into its component spectrum without reflections when uncoated

Penta Prisms:

Ray deviation of 90°

Produce left-handed images due to a single reflection

Slight shift of prism does not affect the true right angle at which rays are reflected

Amici Roof Prisms:

Ray deviation of 90°

Produce right-handed images

Roofed surface causes extra reflection

Dove Prisms:

Either used coated or uncoated

When uncoated, left-handed image rotates by twice the prism rotation angle

When coated, right-handed image reflected back towards itself

Half-Penta Prisms:

Deviate ray path by 45°

Right-handed image

Combined with Schmidt prisms to create Pechan prisms

Schmidt Prisms:

Deviate ray path by 45°

Right-handed image

Combined with half-penta prisms to create Pechan prisms

Pechan Prisms:

Inverts image, rotating it by 180°

Right-handed image

Combination of a Schmidt prism and half-penta prism

Rhomboid Prisms:

Lateral displacement of beam

Lateral displacement equivalent to prism length

Does not invert image

Please contact us if you have any need for them.