Why Level D flight simulators utilize massive spherical collimating mirrors rather than flat projection screens.
When captain and first officer look out the cockpit windshield at runway centerlines on a flat projection screen, their different physical eye positions introduce angular parallax distortion, making it impossible for both pilots to see aligned runway lights.
Level D simulators utilize collimated mirror systems: high-resolution projectors project imagery onto a back-projection screen, which reflects off a continuous spherical mirror, focusing the light rays to optical infinity. Both pilots see parallel light rays without parallax distortion.
Collimated optics deliver high dynamic contrast, faithfully rendering the subtle glare of airport approach lighting piercing through nighttime cloud decks.