Thanks, all, for this discussion. It gives me something to think about as I try to understand my data.
The triplet lens in question serves to collimate the light coming out of an LED light source. The development
of this stellar source was long ago in the past, so am not sure of the glass type. I do know that this lens
has been measured on a Zygo interferometer to have a wavefront error of 0.010 RMS, well within the requirement of 0.050 RMS. No attempts are ever made to adjust the focus, which would simply amount to repositioning the light source with respect to the collimation lens via a translation stage. The stage maintains its position to within 2 microns.
This beam of collimated light is collected/focused onto a sensor. We first sum up 120 frames of
data to form a pixel response function (PRF) from the individual PSFs. I wonder if a barely perceptible
temperature-induced error for a single image frame (i.e. PSF) might become more noticeable at the level
of the PRF.
The hardware that generates this collimated light is capable of producing a log file, not that it was
generated in this test case. The log file would include the temperature of the collimation lens. I suppose
the best thing to do is to see if there is a correlation between the collimation lens temperature
and the shape of the PRF, if I can ever convince the test group to rerun the experiment.
Sorry that I cannot be any more specific than this, as the work is proprietary. Regardless, this
discussion is helpful.
Edited by AXAF, 04 May 2021 - 01:10 PM.