Sensors, I’m sure there’s a post showing the underside of the head unit and labeling each sensor but I can’t find it.
Pretty sure openglow has you covered. Google it if you’ve never been.
Pic is here. Or you can pop your head off the carriage plate and take a look at your own. https://support.glowforge.com/hc/en-us/articles/360033633614-Cleaning
I guess I meant more along the lines of what each of those are pointing at.
Two diodes and a sensor presumably the diodes. One for sure is measurements of focal height (not sure which or both or all three).
The camera sees the red dot from the laser diode (as well as close ups for passthrough alignment and snapmarks). The other diode is a flash for those operations.