I just purchased a used Rift and I gotta say it's better than I expected. Works great for racing and flight sims.
Although the resolution is low they use some kind of checkerboard filter to make the subpixels less apparent and pre-distort the the RGB channels to minimize chromatic aberration due to having a single magnifying lens for each eye. The color fringing is still there, but not as much of an issue as you get immersed and look mainly to the center of your vision.
Everything is focused at 1.3 m distance to minimze vergence/accomodation conflict for most scenes.

After using it for a while I was interested in disassembling it and checking what's inside.

TLDR it's not that complicated inside. There is a single board which handles the video/audio and sensors, bunch of sensors on the front of the device connected with a ribbon cable, two square OLED panels (not one) that can mechanically shift from each other for different interpupilary distances and two plastic lenses for the eyes. They are not aspheres or Fresnel lens but a hybrid of the two. I compared their lens with ordinary flat Fresnels and I'm struggling to find an improvement in image quality when looking through both.

I'm suprised why they didn't go with a lens doublet to minimize chromatic aberrarion since there's about a 40mm free space between the lens and the OLED panel. It could be weight but it could also be cutting corners to reduce production cost.

I'm not thinking of swapping the lenses yet as it's difficult to modify the firmware with the correct frame distortion, but some other things may be improved. Main issue is due to stray light from an OLED screen inside the device bouncing off of the ridges of the fresnel lens, as well as the plastic walls around the screen between the screen and lens. https://i.imgur.com/ojpdOCS.jpg
Ordinary glare (not the highlight of the rings) is also apparent. http://i.imgur.com/XaPk0VL.jpg
This gets annoying in space simulators where the background is very dark.


Perhaps something could be done with polarizers. The screen is already a bit too bright by default for my preference.
Will making the light polarized, then another polarizer film after the lens minimize the stray light?


This will probably filter out the light that has bounced off of the black plastic walls but for this to really make an improvement the light that has been bouncing from the lens to the screen and back and also refracting and reflecting in the Fresnel lens ridges would need to be reduced. I don't know much about polarization to know if these refractions would change it and be filtered by a polarizer. Maybe someone else does? I could definitely order some polarizer film and test it if there's a point.

This is another, perhaps silly idea I had for fixing this issue:
https://i.imgur.com/ZNrlW31.png


The other thing which is annoying is the device is covering your face so tightly your face gets sweaty and fogs the lenses. A small 12V fan inside should help with that.