I've built an AR headset with a normal backlit LCD, fresnel lens, and a semi-transparent mirror. Not great but it works. You can certainly build a DIY projecto

I've built an AR headset with a normal backlit LCD, fresnel lens, and a semi-transparent mirror. Not great but it works. You can certainly build a DIY projector that way. Building a high quality projector is hard but a crappy one is very simple. If you jam an LCD between a light source and a lens at the right distances you will get an image. Slide projectors, camera lenses, magnifying glass lenses, even those fresnel page magnifier lenses work.