Some Perceptual Effects of Differential Luminance Induced by the use of a Monocular Head-Up Display

Abstract

Head-up displays (HUDs) are currently used to present a pilot with a view of the outside world and simultaneously with overlapping instrument-related symbology. Monocular HUDs (MHUDs) have also been developed that present symbology only to one eye. Because not all of the light from the external scene passes through the MHUD, the result is differential illumination between the MHUD and non-MHUD eyes. The literature suggests that under appropriate circumstances differential illumination of the eyes can lead to distortions of depth, size, and direction and velocity of motion. If of sufficient magnitude, these distortions could seriously disrupt pilot performance during low level flight and on approach and landing. The extent to which these possible distortions will actually occur cannot be determined from the existing literature and must be determined empirically.