yeah, I know because trying to make a halo EVA helmet, I wanted a substitute for polarizing that massive, compound curved visor. So I tried putting my cell phone camera viewing out a small hole. I got a general idea of where I was, I didn;t smash into walls, but it is incredibily blurry, and it honestly isn't worth the money. HUD's (like in games) work by having the whole image on your visor. Your eye is somewhat capable of focusing at that point. but viewing a screen even closer in is impossible unless your eyes are capable of focusing at any range.
Oh, but SOME helmets might be capable of it. A stormtrooper helmet MIGHT work, but the helmet has to have a bulge at the front, or fit rather large.
