Liquid crystal display for projection systems

• US 5,187,510 A
• Filed: 12/10/1990
• Issued: 02/16/1993
• Est. Priority Date: 04/30/1987
• Status: Expired due to Fees

• Current Assignee: N-View Corporation
• Original Assignee: N-View Corporation
• Inventors: Vogeley, Arthur W., Vogeley, James H.
• Primary Examiner(s): HAROIAN, HARRY
• Application Number:
  US07/625,037
• Time in Patent Office: 799 Days
• Field of Search: 353/122, 353/121, 353/57-61, 353/DIG. 3, 353/DIG. 5, 353/20, 353/21, 353/25, 353/69, 353/70
• US Class Current: 353/122
• CPC Class Codes: G02F 1/133385 with cooling means, e.g. fans
• CPC Class Codes: G03B 21/132 Overhead projectors, i.e. capable of projecting hand-writing or drawing during action epidiascopic projectors G03B21/08
• CPC Class Codes: Y10S 353/03 Transparent

Abstract

Disclosed is a liquid crystal display unit comprising liquid twisted nematic liquid crystal material sandwiched between two polarizers. Transparent electrodes are provided on each side of the layer of liquid crystal for locally energizing liquid crystal material in the vicinity of two energized transparent electrodes. Polarized light passing through one polarizer is twisted or not twisted depending upon the energization state of the liquid crystal material and depending upon the second polarizer orientation does or does not pass therethrough. Accordingly, depending upon energization locations, images are formed which can be projected upon a screen. In preferred embodiments the liquid crystal display unit is used in conjunction with a cabinet to provide a low stress work station. A further embodiment includes a folded optical path in combination with the liquid crystal display so as to provide a compact projector. When operating in conjunction with an overhead projector, a preferred embodiment of the present invention is powered by light energy from the overhead projector and in a further preferred embodiment is controlled through the use of infrared or other non-visible electromagnetic communication.

Claims

1. A compact information projector for projecting electronically generated display images on a remote surface, said projector comprising:

means for projecting a beam of light along an optical path to a viewing screen, said projecting means including a light source;

computer control means, responsive to at least one of stored commands and a keyboard input, for generating liquid crystal means energizing signals;

keyboard means for providing a keyboard input to said computer control means;

twisted nematic liquid crystal means, located along said optical path, for controlling polarization of light passing therethrough in response to localized energization and de-energization of said crystal means in accordance with said crystal means energizing signals;

means, responsive to said computer control means energizing signals, for selectively and locally energizing and de-energizing said crystal means;

back polarizing means disposed in said beam and located between said crystal means and said light source, for polarizing light passing therethrough; and

front analyzing means, located between said crystal means and said remote surface, for allowing light of a selected polarization to pass therethrough and for blocking light not having said selected polarization.

2. The compact information projector according to claim 1, wherein said selectively and locally energizing means comprises:

a first plurality of conductors; and

a second plurality of conductors at least partially crossing said first plurality of conductors, such that when a single conductor from said first plurality and a single conductor from said second plurality are energized, said crystal means is energized in the vicinity of the crossing of said single conductors.

3. The compact information projector according to claim 1, wherein at least one infrared reflecting means is located optically between said light source and said liquid crystal means, said at least one reflecting means comprises a means for reflecting infrared light and passing visible light.

4. The compact information projector according to claim 1, wherein said computer control means includes a disk drive storage means for storing computer commands for driving said liquid crystal means.

5. The compact information projector according to claim 1, wherein said keyboard means and said computer control means are separate units, and there is further provided a means for communicating from said keyboard to said computer control means.

6. The compact information projector according to claim 5, wherein said means for communicating comprises a cable connection.

7. The compact information projector according to claim 5, wherein said means for communicating comprises:

an infrared transmitter means, located on said keyboard means and responsive to operation of said keyboard means, for transmitting infrared pulses related to operation of said keyboard means; and

an infrared receiver means, located on said computer control means and responsive to said infrared pulses from said infrared transmitter means, for providing a keyboard input to said computer control means.

8. The compact information projector according to claim 5, wherein said means for communicating comprises:

a radio frequency transmitter means, located on said keyboard means and responsive to operation of said keyboard means, for transmitting radio signals related to operation of said keyboard means; and

a radio frequency receiver means, located on said computer control means and responsive to said radio signals from said radio frequency transmitter means, for providing a keyboard input to said computer control means.

9. The compact information projector according to claim 1, wherein said means for projecting includes a means for preventing keystone distortion in said beam, said means for preventing including means for rotating said liquid crystal means about a horizontal axis.

10. The compact information projector according to claim 1, wherein said means for projecting includes at least one collecting lens in said optical path.

11. The compact information projector according to claim 1, wherein said projector includes means for cooling said crystal means.

12. The compact information projector according to claim 1, wherein said projector includes means for preventing heating of said crystal means.

13. The compact information projector according to claim 1, further including monitor means for monitoring the electronically generated display images.

14. A compact projector for projecting electronically generated display images from a computer onto a remote surface, said projector comprising:

means for projecting a beam of light along an optical path to a viewing screen, said projecting means including a light source;

control means, responsive to said electronically generated display images from said computer, for generating liquid crystal means energizing signals on a pixel-by-pixel basis;

twisted nematic liquid crystal means, located along said optical path, for controlling polarization of light passing through a plurality of pixels in response to localized energization and de-energization of each pixel of said crystal means in accordance with said crystal means energizing signals;

means, responsive to said control means energizing signals, for selectively and locally energizing said crystal means;

back polarizing means disposed in said beam and located between said crystal means and said light source, for polarizing light passing therethrough; and

front analyzing means, located between said crystal means and said remote surface, for allowing light of a selected polarization to pass therethrough and for blocking light not having said selected polarization.

15. The compact information projector according to claim 14, wherein said selectively and locally energizing means comprises:

a first plurality of conductors; and

a second plurality of conductors at least partially crossing said first plurality of conductors, each crossing associated with a single pixel, such that when a single conductor from said first plurality and a single conductor from said second plurality are energized, said crystal means pixel is energized in the vicinity of the crossing of said single conductors.

16. The compact information projector according to claim 14, wherein at least one infrared reflecting means is located optically between said light source and said liquid crystal means, said at least one infrared reflecting means comprises a means for reflecting infrared light and passing visible light.

17. The compact information projector according to claim 14, wherein said means for projecting includes a means for preventing keystone distortion in said beam, said means for preventing including means for rotating said liquid crystal means about a horizontal axis.

18. The compact information projector according to claim 14, wherein said means for projecting includes at least one collecting lens in said optical path.

19. The compact information projector according to claim 14, wherein said projector includes means for cooling said crystal means.

20. The compact information projector according to claim 14, wherein said projector includes means for preventing heating of said crystal means.

21. The compact information projector according to claim 14, further including monitor means for monitoring the electronically generated display images.