Pechan Prism: Definition and Working Principle

Pechan prisms comprise two air-spaced components, and have the ability to revert (flip horizontally) or invert (flip vertically) an image, depending upon it's orientation. It can be used in convergent, divergent and parallel light. This prism can be rotated if required to compensate for image rotation.

The Pechan prism operates in a similar manner to the Dove prism. It can be operated with convergent or divergent light, which enables the size of the instrument to be reduced. When not centered correctly, it may displace the line of sight, but will not deviate it. The Pechan prism can be adapted for image rotation and derotation.

The Pechan prism resembles the Pechan-Schmidt prism but does not have a roof edge. Converting the top surface of the Pechan prism into a roof, a Pechan-Schmidt prism can be created with six reflections.

The Pechan prism is commonly used as a compact image rotator/derotator instead of the Dove, double-Dove, and delta prisms as it can be used in convergent or divergent beams.

References

• Prisms - Florida State University
• Prisms Frequently Used in Optical Systems - Align Optics
• Geometrical and Instrumental Optics - Edited by Daniel Malacara
• Opto-Mechanical Systems Design, Third Edition - Paul R. Yoder, Jr.