HUD Autobrilliance Sensor (ABS) Module

Autobrilliance Sensor

A HUD Auto-Brilliance Sensor (ABS) is mounted on the display unit (or nearby) such that it gazes at the same region of the outside world as the HUD's field of view. The ABS has a similar field of view to that of the HUD and the spectral response of its photocell is matched to that of the human eye's daylight vision by the use of a coloured filter window that forms part of the ABS.
The resulting photocell's output responds to the luminance of the HUD background in a manner that matches the HUD user's visual perception. This allows the luminance of the HUD's display to be automatically adjusted to maintain its user-set contrast ratio against its background over a few decades of luminance change. Strictly it should be called an Auto-Contrast Sensor.