The light source image does not match the image at the detector

[999-x]

Hello, sorry to bother you. I have a question that I would like to ask you.
The example I ran is' examples\withRaycing\07-AnalyzerBent2D '.
I use the code plot in Figure 1 to plot the image of the position of the light source and the position of the detector. I just moved the position of the detector by 0.2 millimeters from its initial position, in theory, the image at the detector should be scaled proportionally to the size of the image at the light source, and the shape should be basically consistent.But the image at the light source is circular, while the image at the detector is square.Why does the image shape at the light source and detector not match? Is it because the analysis of the crystal is square?
(Figure 2 shows the image at the light source, and Figure 3 shows the image at the detector)
I’m looking forward to your reply！