All the sample files used in this article are included in a zip file that can be downloaded from a link on the last page of this article. The first file we will look at is 'Cooke one field, one wavelength.zmx', which is based on the Cooke triplet sample file distributed with ZEMAX. As the name implies, this file is based on a single (field, wavelength) pair.



and its wavefront looks like so:



and its spot size is like so:



Now Zernike coefficients are a compact way of describing the wavefront error produced by an optical system. In order to produce a 'black box' model, we must first produce a paraxial optical system with the same first-order properties, and then aberrate the wavefront produced by this paraxial system with the Zernike data.

The key paraxial data we need is the exit pupil position, and exit pupil diameter. All wavefront data is measured in the exit pupil, and so our black box system must have the same pupil data. For this file, the pupil data is as follows:

Exit Pupil Diameter = 10.2337 mm
Exit Pupil Position = -50.9613 mm