Head up display with incident light filter

Claim 1

A head up display for reflecting information from a combiner wherein the angle of reflection effects light polarization, the display including optical filtering of extraneous reflections due to external incident light comprising: a light emitting image source for generating display information, the image source comprising selectively energized segments subject to undesired illumination by external light incident on the combiner; an optical system for projecting light from the image source onto the combiner at an incident angle near Brewster's angle to define a horizontal axis of polarization for light reflected from the combiner that originates from the image source; and a circular polarizer between the optical system and the image source for suppressing external incident light reflected from the display surface, the circular polarizer comprising a linear polarizer and quarter-wave plate in combination, the linear polarizer and quarter-wave plate being disposed to circularly polarized external incident light reaching the image source and to absorb such polarized light after reflection from the image source, and the linear polarizer having a polarization axis substantially parallel to the horizontal axis of polarization for horizontally polarizing light projected onto the combiner that originates from the image source to maximize the display efficiency.