Real F-22 HUD

This video is dated 7 July 1995. The F-22 HUD did not use what at the time was the more ubiquitous conventional HUD set up with a simple collimating lens. It is a holographic display which involves reflecting the HUD image several times using diffraction gratings to filter out unwanted spectrums of visible light (Non-green light in this case) from the HUD image before it reaches the combiner glass for viewing. Instead of a separate lens the combiner itself will collimate the HUD image, causing the HUD symbology to appear always in focus to the human eyeball no matter what distance the lens of their eyeball is focused at. Collimation restricts the direction of light into one parallel direction. This is how the illusion of infinite focus is achieved, as both eyes are not able to observe the same parts of the HUD image at the same time so a double image is never perceived. Cameras do not capture this effect of collimation as its effect is only observable and useful to binocular vision. A HUD which utilizes holographic diffraction gratings also allows us to have a much wider field of view since we are not restricted by the smaller window of visiblity presented by requiring the presence of a particular raw lens so the symbology can appear on the entire field of the combiner glass instead of just the center, reducing clutter.