Head up display with incident light filter

摘要

Glare and spurious reflections of external light on the image source of a head up display are eliminated by a circular polarizer in the optical path of the display. The head up display includes a mirror system for projecting a pattern from the image source onto a vehicle windshield where it is reflected to the operator, wherein polarization is effected at the windshield reflection. The circular polarizer includes a linear polarizer and a quarter wave plate arranged to extinguish the external incident light after reflection from the image source. The linear polarizer axis is aligned with the polarization axis at the windshield to optimize the brightness of the display.