To examine the thickness boundary constraint capabilities of ZEMAX, please download the attached sequential ZEMAX file on the last page of this article:

FILE:  “Schmidt_Camera_Start.ZMX”

This is a model of a Schmidt camera. While Schmidt cameras are generally used for wide field of view applications, we will just work on-axis for the purposes of this article. This particular Schmidt camera is a standard configuration. It consists of an aspheric lens along with a spherical mirror:

We want to improve the imaging performance of our Schmidt camera so we will optimize for best RMS spot size. Variables have already been set for the front radius of curvature of the aspheric lens along with the r⁴ coefficient of the asphere:

With variables set, we will now build a default merit function for RMS spot radius. In the Merit Function Editor, select “Tools > Default Merit Function”. Be sure to set the number of “Rings” to 4 given that we are optimizing the r⁴ aspheric coefficient. While we are not going to optimize the thickness of the lens, changes to the radius of curvature and 4^th order aspheric coefficient will change the effective thickness of our lens. As such, we will incorporate default boundary constraints on thickness in our merit function. We will bound a minimum thickness of 1 mm at the center and edge along with a maximum thickness of 5 mm.