Corner Cube retroreflectors use three mutually orthogonal reflectors to retro-reflect any ray that lands on it. A flat mirror will only achieve retro-reflection in the specific case where the ray lands at normal incidence. By contrast, the corner cube retroreflector will retro-reflect over a wide range of incident angles. This makes it very useful in applications where precise alignment is difficult to achieve, where vibration is present, or where the retroreflector must be moved, for example.

The simplest way to model a retro-reflector is with the sequential 'Retro-Reflect' surface. This idealized surface is a planar surface which reflects rays back exactly along the incident path, acting as a perfect phase-conjugate mirror. The file 'perfect retro-reflector.zmx' shows such a system:



(All the ZEMAX files used in this article are included in a .zip file which can be downloaded via the link on the last page of this article.)

The retro-reflect surface can be tilted as much as is wished, and the rays will always reflect exactly along the incident direction. There is zero OPD or lateral offset introduced by this mirror. Perfect!

But in reality, such perfection does not exist. Corner cube retroreflectors are made to finite precision, and there can be complicating effects due to the faces not being exactly orthogonal, surface form errors, material inhomogeneity and more. In this article we will build a complete model of a corner cube retroreflector and examine the effects of these imperfections.