Hi all,

I just wanted to comment on this thread, as I think there are a few other considerations going on when OpticStudio reports luminance/radiance that may also explain the results you’re seeing.

When OpticStudio generates Luminance (Angle Space) results, it will start with Luminous Intensity data, and then scale data per-pixel based on the area of the detector times a cosine factor with the angle represented at the center of any given pixel. In other words, the solid angle information is broken down per-pixel. For the same size, resolution, and Max/Min Angle Range values for a Detector Rectangle, this angular pixel mapping would remain the same, but then you would get different results if your far-field distribution has changed. Since it looks like the lens “narrows” the angular distribution of rays after the lens, you are putting more energy in a smaller angular range, resulting in a higher peak luminous intensity value, thus getting a higher peak Luminance (Angle Space) result.

This stands in contrast to the treatment of radiance where I think you’d need to know the changing solid angle of the illumination itself after the lens in order to observe the conservation of radiance you’re expecting. Again, OpticStudio will just post-process either the illuminance or luminous intensity data for Luminance depending on whether you select Position or Angle Space. You can also find more discussion on this in our Help Files at “The Analyze Tab (non-sequential ui mode) > Detectors Group > Detector Viewer ”.

Let us know if you have any more questions here -- thanks!