The distance from the top of the fresnel to the top of the helmet (above the fresnel) is just over 10cm:

That means that the optical path I had probably was going to intersect with the user head area.

I've got this new path that has a couple of benefits:

• There is no lens near a focal point
• Only 2 glass lenses are needed, so that (starting from the fresnel lens), it's F40 -> F30 -> F40
• The screen is less than 10mm behind the front of the eye.

The steepest angle emmited from the screen is under 15 degrees, and according to this blog post (see below), the OLED brightness at a given angle is cos(angle) * 100%. The result for 15 degrees is 96.6% brightness so I'd probably never notice. I wouldn't be suprised if I see steeper angles from normal sized OLED panels.

Overlaying the path, it seems that I've still got space to go up even further, perhaps to allow more head padding space.