Do you remember Kubrick's "2001"?
The entire "Dawn Of Man"-sequence at the beginning that looks like it was shot outdoors was really staged on a giant sound stage in London. The African backgrounds were projected onto a huge 90 by 40 ft. front projection screen. This was one big innovation of the film, among many others.
The front projection or "Scotchlite" process uses the retro-reflective capacities of 3M Scotchlite material . It concentrates light and reflects it back to the source in a very narrow angle. Traffic signs light up brightly when hit by car lights using the same materials. The stuff is also used for reflective strips on clothes. The most interesting material is Scotchlite 7610. It reflects light along the optical axis with 1610 times the brightness of a flat white wall.
In closeup the material consists of microscopic glass beads with a reflective coating. Light enters the beads and is reflected in a 180 degree turn back to the source almost without loss. I did a lot of front projection experiments in the 1970s and have worked on several projects in the movies that used the process. BAVARIA studios in Munich at the time had an enormous 30 ft. front projection screen in one of their soundstages. On the opposite corner of the stage, I took out my cigarette lighter and looked at the screen through the flame. AND THE ENTIRE SCREEN LIT UP, just from that little lighter flame!
The material can still be bought, in the form of adhesive tape or as large rolls. It has a grey matte surface.
For the film process, a movie or still projector was set up next to the camera at 90 degrees to it. In front of the camera was a half silvered mirror at a 45 degree angle, reflecting side turned towards the screen. The axes of camera and projector lenses were made to coincide exactly. This way the shadows of the actors fell behind them and were masked by their own bodies. This alignment had to be done very precisely or a fringe or black line would appear around the foreground actors.
My idea is that this process could be very useful in the context of NBTV. Nipkow disks could be made to reflect the images instead of passing them thru tiny holes. Beaded disks, as I have seen here on the forum could profit from this technique. This really squeezes every lumen out of a light source.If you had small transparent glass beads or pin heads instead of the holes in the disk, the light would travel back to the source, the LED array would have to come up to the front of the disk, nothing would have to pass THRU the disk anymore. The half silvered mirror should have a 70 /30 ratio -70 % transmission, 30 % reflectance. The scotchlite is so efficient it works even with a simple glass plate.
Other scanner shapes like a drum with strips of scotchlite could be realized.
Attached is my simple drawing with the N. disk , the LED Array pulled up front and the viewing lens. Would love to hear what you think of the idea.