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The waveguides work by total internal reflection (TIR) cause by the index of refraction mismatch between glass and air. If the layers of glass were bonded together with no gap (or other indexed mismatched material in between) then the light would exit the waveguide to the next layer an you don’t have a waveguide/TIR.
I want to add to my prior comment that I have only seen the teardown pictures and had to mentally reconstruct what was going on from picture. I did not see the components as they were taken off. Based off the pictures, I was trying to make it work based on what I was seen from static pictures.
Something that concerns me in this design is that the LED light is shot straight at the beam splitter and if the polarization is not great with the first/LED polarizer and the beam splitter, there will be a spot of uncontrolled light (about the size of the LEDs) in the center of the image. I’m assuming they are using wire grid polarizers in both locations.
Another issue with the design is that the image has to pass through and reflect off the beam splitter (if based on what I was shown and was told is correct). Usually with a wire grid polarizer, you don’t want to pass the “image” of the LCOS through the polarizer as it will do damage to the image. The FIG 6 from the patents would be the “normal” configuration.
Wick, you seem to know something about this subject, but you are wrong about the Figure from the patent. The beam splitter will polarize the light but having two might work better.
In the final configuration and as diagrams by iFixit (the 3rd figure with respect to Step 10) they absolutely need a polarizer (as show) right after the LEDs or else half the light will go strait into the injection optics without modulation. This 3rd figure does leave out a quarter-wave plate and polarizing mirror on the right side of the beam splitter cube that is necessary to bounce the light back to the beam splitter so it can be directed out to the injection logic. As drawn, the light from the LCOS would go through the beam splitter and out the side of the cube.