Not sure the exact details- I heard they were sampling 10 bits per pixel but a bunch of their release notes talked about photon count detection back when they switched to that system.
Given that the HW3 cameras started being used to just generate RGB images, I suspect the current iteration is working by just pulling RAW format frames and interpreting them as a photon count grid, from there detecting edges and geometry with the occupancy network.

I've not seen much of anything published by Tesla on the subject. I suspect most of their research they are keeping hush hush to get a leg up on the competition. They share everything regarding EV tech because they want to push the industry in that direction, but I think they see FSD as their secret sauce that they might sell hardware kits but not let others too far under the hood.