05729242 is referenced by 196 patents and cites 16 patents.

An optical system is provided that produces bright, high contrast head-up display images which are not adversely affected by the direct exposure to sunlight of the system's virtual image source. The optical system comprises a light source system which projects a focused light beam to a segmented, electronically-addressed polymer-dispersed liquid crystal ("PDLC")-type film, which serves as a primary image source. Selected segments of the image source are made transmissive while other selected segments scatter light. Accordingly, the portions of the focused light beam incident to transmissive segments are transmitted to form a real image, while the balance of the focused light beam is scattered. A stray light-blocking means, such as a lens/aperture combination, is employed to block the scattered light. The real image is projected onto an unsegmented, electronically-addressed PDLC-type film serving as an image screen. The image screen is the head-up display image source and replaces other emissive light sources in conventional head-up displays. The PDLC-type image screen is unsegmented so that there are no display elements to provide false information upon exposure to sunlight. Moreover, the image screen is highly forward scattering, so that stray sunlight incident to the image screen is forward scattered in the direction opposite to the image source, thereby preventing the reflection of sunlight into viewers' eyes. The light transmitted through the PDLC-type image screen comprises the head-up display image, which is then projected by a projection means, such as a concave mirror or lens, to the desired location for viewing as a virtual image.

Title
Dual PDLC-projection head-up display
Application Number
8/646576
Publication Number
5729242
Application Date
May 8, 1996
Publication Date
March 17, 1998
Inventor
Khoon Cheng Lim
Los Angeles
CA, US
John H Erdmann
Phoenix
AZ, US
J David Margerum
Woodland Hills
CA, US
Agent
W K Denson Low
V D Duraiswamy
Assignee
Hughes Electronics
CA, US
IPC
G03H 1/00
G09G 5/00
View Original Source