Backlighting for bright liquid crystal display
First Claim
1. An image illumination apparatus for back lighting a display including a liquid crystal cell having an active region comprising:
- a light source spaced from the display and having an area equal to or greater than the area of the active region;
an elongated duct having a specularly reflecting inner surface for coupling light from the light source to the display, a first aperture of the duct being adjacent the light source and substantially the same size and shape as the light source, a second aperture of the duct being aligned with the cell and having substantially the same size and shape as the active region of the cell;
the first aperture of the duct being covered by an IR reflecting mirror serving as a thermal barrier;
a holographic diffuser element over the second aperture for enhancing illumination uniformity;
the liquid crystal cell spaced from the diffuser element for illumination by light passing through the duct and the diffuser element; and
an air cooling passage between the liquid crystal cell and the diffuser element.
6 Assignments
0 Petitions
Accused Products
Abstract
A bright bulb with a parabolic or elliptical reflector project light through a duct with internal reflective walls to a liquid crystal display having the same or smaller area than the reflector area. The duct tapers from a circular entrance aperture to a rectangular exit aperture and enhances brightness and uniformity. An IR mirror between the lamp and the duct reflects heat to the lamp. A holographic diffuser at the exit aperture further improves uniformity. The LCD polarizer is mounted on the diffuser and spaced from the liquid crystal cell by an intervening cooling air passage to minimize heating of the cell. The display is suitable for HUD applications.
-
Citations
7 Claims
-
1. An image illumination apparatus for back lighting a display including a liquid crystal cell having an active region comprising:
-
a light source spaced from the display and having an area equal to or greater than the area of the active region; an elongated duct having a specularly reflecting inner surface for coupling light from the light source to the display, a first aperture of the duct being adjacent the light source and substantially the same size and shape as the light source, a second aperture of the duct being aligned with the cell and having substantially the same size and shape as the active region of the cell; the first aperture of the duct being covered by an IR reflecting mirror serving as a thermal barrier; a holographic diffuser element over the second aperture for enhancing illumination uniformity; the liquid crystal cell spaced from the diffuser element for illumination by light passing through the duct and the diffuser element; and an air cooling passage between the liquid crystal cell and the diffuser element. - View Dependent Claims (2, 3, 4, 5, 6, 7)
-
Specification