Incident angle vs. transmittance angle using Ray Tracing

Hello,

I am new to Comsol and I am still getting familiar with its functionalities. My current simulation aim is to use the Ray Tracing tool with a rotating convex lens and plot the incident angle on the lens vs. transmittance angle hitting an image plane. I was able to set-up the design, rays, and rotation sweep but I am still not sure how to plot ray angles as I did not find a predefined ray angle expression to compute the angles.

Is there a way to define planes at the incident and image surfaces then compute it from there? Or what is the best way to approach this?

Thanks.

Best regards, R