It has been a couple of years since I went looking for parts
to build a viewer. A challenging bit to find was a decent
light source. Edge-lit panels have been my preferred choice.
Finding and building them has been hard.

Today, I stumbled across an instructive document from OSRAM
(A maker of optical semiconductors). In it, is a discussion
of internal reflections, critical angles, and some practical
considerations when designing such a panel.

> https://dammedia.osram.info/media/resource/hires/osram-dam-2496771/Light%20Guides.pdf

'tis a well-written document, and I recommend it to anyone
who has seriously considered making a viewer from the ground up.

--
John Thurston
Juneau Alaska
http://stereo.thurstons.us