Sign of Conic Constant for OAP

  • 16 November 2021
  • 2 replies


  I am setting up a system with a diverging source (object space NA), a fold mirror, and then an OAP to collimate the light. In order to collimate the light, the radius on the OAP had to be positive, though I expected it to be negative, which I assume is due to the coordinate breaks and reference position. My question is if I want to model an OAP in this system, is the conic constant still -1 or is it +1?

Thank you,



Best answer by Jeff.Wilde 16 November 2021, 18:45

View original

2 replies

Userlevel 3
Badge +2

For an OAP the conic constant should always be -1 so that the surface is parabolic (surface sag proportional to r^2):


Here’s an example:


Thank you! This answers/solves my question.