optical stages and alignment, sending beams of light to specific locations.
https://en.wikipedia.org/wiki/Optical_table
Optical suppliers are
https://www.edmundoptics.com/ (highly recommend ordering their catalog)
https://www.newport.com/g/optical-tables
https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=70...
Youtube channels on optics
Man, Edmund Scientific is a throwback. They used to have an awesome surplus store in NJ full of all kinds of nerd stuff.
They are still around as
https://www.scientificsonline.com/ (Edmund's Scientific) though it is mostly k-8 science toys.
https://sciplus.com/ (Chicagoland)
https://www.surplusgizmos.com/ (Intel and Portland electronics surplus)