squidward_eyes_93
Lots of home cinema projectors use single chip DLP and a colour wheel, could be you were using one of these? Its a bit difficult to explain how they work in text, but: imagine a monochrome display running at 180frames per second; every frame a physical colour filter (red, blue, green) is laid over the screen, and the screen's pixels update to show the correct level of red/blue/green; this results in the appearance of a 60fps full colour display; now imagine all that crammed into a projector.
These are probably bad for eyestrain because there is a lot of flicker as the display swaps out each colour. High end DLP cinema projector would use three dlp chips, one for each colour, so would have no need to be constantly swapping colours and creating flicker.