An off-axis parabolic (OAP) mirror consists of a small section cut out (either figuratively or literally) from a larger, so-called “parent” parabolic mirror (although such a mirror should more correctly be called a “decentered parabola,” OAP is the almost universally accepted name for it).  Working with these mirrors, especially for the first time, can seem like a daunting task.  However, with a little instruction and a bit of practice, OAPs can be fairly straightforward to manipulate and very handy to use.

When designing systems using OAPs, it can be helpful to keep the parent parabola in mind, and it can also be helpful to keep the parent parabola in your system, only trimming down to the decentered (or so-called “Off-Axis”) aperture at the very last step in the design process.  In this example, we’re going to design, position, and clock an OAP in an optical system in such a way as to provide a specified output, and then we’re going to specify the placement of the OAP relative to other optical elements in the system. This is a realistic design problem, and one that demonstrates many different, useful ZEMAX techniques.

The article is accompanied by a zip file which can be downloaded from the last page. It contains the starting point of this design.