# Drawing an off-axis parabolic mirror in pst-optexp and pst-optic

Having looked through the pst-optexp manual, it doesn't seem that there is a built-in off-axis parabolic mirror. I'm trying to make a diagram of a lab setup that goes like this:

1. Collimated beam falls on a converging lens.

2. The focal point of the lens is at the same point as the focal point of the OAP.

3. OAP reflects a collimated beam at a 90 degree angle to the incident beam.

• Welcome to TeX-SX. Can you tell us more about this thing since we are not all optics people. Best is to draw on a paper or on Paint and upload the picture to the question by editing it. – percusse Oct 2 '14 at 17:56
• Have you tried using my solution? If you're having problems with it, I would be glad to here about it in order to get some feedback about this feature before integrating it in the main release :) – Christoph Oct 28 '14 at 10:51
• @Christoph - Geez, I totally missed all of the replies to this post. I'll try implementing your solution over the weekend. percusse - An off-axis parabolic mirror is a mirror whose reflective surface is in the shape of a piece of a parabolic surface instead of a piece of a spherical surface. These are nice because they don't exhibit spherical abberations. – zmitchell Nov 18 '14 at 17:19
• is there a bug related to \oapmirror? I've been trying to draw one in my experimental setup sketch without success. In fact, I tried to compile the code from Christoph and it didn't work. – Ludwig Regalado Nov 27 '18 at 21:45

Version 5.1 of pst-optexp contains an off-axis parabolic mirror as \oapmirror. You must specify three nodes to align the mirror properly: the input nodes, the center node, where the actual mirror center is placed, and the focal point.

Here is an example for a mirror which reflects by 90°:

\documentclass[margin=5pt, pstricks]{standalone}
\usepackage{pst-optexp}
\begin{document}
\begin{pspicture}(5,4)
\pnodes(5,0.5){In}(1,0.5){C}(1,2){Focus}(1,4){Out}