Are your tissue samples alive or dead, or should I say can you afford to have them die? If so, have you considered SEM Scanning Electron Microscopy? Do a google search for David Scharf if you want to see some excellent sample SEM photos.
I can't remember the vendor name but check into laser shows such as the old "Laserium" who used both mirror galvanometers and servo driven scanners. I think it might have been called General Scanning.
This won't drive your mirror that big but might give you some ideas. Perhaps going...
A good start is a Minolta Luminance meter like the LS-100 for stable measurements and then a "standard" linear polarizer like a 3M/Polaroid HN42HE with known properties. You can then rotate this over your test polarizer over a stable light table or aim through it at the sky to measure...