Liquid crystal display for projection systems

• US 5,255,029 A
• Filed: 07/22/1992
• Issued: 10/19/1993
• Est. Priority Date: 04/30/1987
• Status: Expired due to Fees

• Current Assignee: N-View Corporation
• Original Assignee: N-View Corporation
• Inventors: Vogeley, Arthur H., Vogeley, James W.
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Dowling, William C.
• Application Number:
  US07/920,190
• Time in Patent Office: 454 Days
• Field of Search: 353/122, 353/20, 353/DIG. 5, 353/DIG. 3, 353/77, 353/78, 359/63, 359/37
• 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

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 low stress work station for providing display images to an operator, said images based upon an electronic signal, said work station comprising:

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

a rear projection screen located at one end of said optical path and in a position to be viewed by said operator;

control means, responsive to said electronic signal, for generating liquid crystal means energizing signals;

twisted nematic 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 control means energizing signals, for selectively and locally energizing said crystal means;

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

front analyzing means, at least partially disposed in said beam and located between said crystal means and said rear projection screen, for allowing light of a selected polarization to pass therethrough and for blocking light not having said selected polarization.

2. The low stress work station according to claim 1, wherein said apparatus further includes visible light transparent insulation means disposed in said beam and located between said light source and said crystal means.

3. The low stress work station according to claim 2, wherein said insulation means comprises a means for reflecting visible light and for passing infrared light.

4. The low stress work station according to claim 2, wherein said insulation means comprises a means for reflecting infrared light and for passing visible light.

5. The low stress work station according to claim 1, wherein said projecting means includes:

at least one reflector means for reflecting light along said optical path; and

lens means for focusing light along said optical path.

6. The low stress work station according to claim 1, wherein said projecting means light source comprises a single point source of light with no additional reflectors or lenses along said optical path.

7. The low stress work station according to claim 5, wherein said lens means comprises a collimating lens located between said light source and said twisted nematic crystal means.

8. The low stress work station according to claim 7, wherein said collimating lens comprises a Fresnel lens.

9. The low stress work station according to claim 1, wherein said means for selectively and locally energizing said crystal 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, a portion of said crystal means related to said crossing is energized.

10. The low stress work station according to claim 1, wherein said rear projection screen comprises a flat rear projection screen.

11. The low stress work station according to claim 1, wherein said apparatus further includes:

a means for reflecting infrared light and for passing visible light; and

a visible light transparent insulation means, located between said means for reflecting and said crystal means, for retarding the flow of heat from said light source to said crystal means.

12. The low stress work station according to claim 11, wherein said visible light transparent insulation means comprises:

spacer means for providing a space between said crystal means and said reflecting means; and

a means for circulating a light transparent cooling fluid through said space.

13. The low stress work station according to claim 12, wherein said light transparent cooling fluid is air and said means for circulating comprises a fan.

14. A cathode ray tube (CRT) replacement for a computer work station, said replacement for providing display images to a work station operator, said display images based upon an at least partially computer controlled signal, said replacement comprising:

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

a rear projecting screen, having front and rear surfaces and located at one end of said optical path, where said beam of light is projected on the rear of said screen and the front of said screen is in a position to be viewed by said operator;

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

means, responsive to said at least partially computer controlled signal, for selectively and locally energizing said crystal means;

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

front analyzing means, at least partially disposed in said beam and located between said crystal means and said rear projection screen, for allowing light of a selected polarization to pass therethrough to the rear of said screen and for blocking light not having said selected polarization.

15. The cathode ray tube (CRT) replacement according to claim 14, wherein said apparatus further includes visible light transparent insulation means at least partially disposed in said beam and located between said light source and said crystal means.

16. The cathode ray tube (CRT) replacement according to claim 15, wherein said insulation means comprises a means for reflecting visible light and for passing infrared light.

17. The cathode ray tube (CRT) replacement according to claim 15, wherein said insulation means comprises a means for reflecting infrared light and for passing visible light.

18. The cathode ray tube (CRT) replacement according to claim 14, wherein said projecting means includes:

at least one reflector means for reflecting light along said optical path; and

lens means for focusing light along said optical path.

19. The cathode ray tube (CRT) replacement according to claim 14, wherein said projecting means light source comprises a single point source of light with no additional reflectors or lenses along said optical path.

20. The cathode ray tube (CRT) replacement according to claim 18, wherein said lens means comprises a collimating lens located between said light source and said twisted nematic crystal means.

21. The cathode ray tube (CRT) replacement according to claim 20, wherein said collimating lens comprises a Fresnel lens.

22. The cathode ray tube (CRT) replacement according to claim 14, wherein said means for selectively and locally energizing said crystal 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, a portion of said crystal means related to said crossing is energized.

23. The cathode ray tube (CRT) replacement according to claim 14, wherein said rear projection screen comprises a flat rear projection screen.

24. The cathode ray (CRT) replacement according to claim 14, wherein said apparatus further includes:

a means for reflecting infrared light and for passing visible light; and

a visible light transparent insulation means, located between said means for reflecting and said crystal means, for retarding the flow of heat from said light source to said crystal means.

25. The cathode ray tube (CRT) replacement according to claim 24, wherein said visible light transparent insulation means comprises:

spacer means for providing a space between said crystal means and said reflecting means; and

a means for circulating a light transparent cooling fluid through said space.

26. The cathode ray tube (CRT) replacement according to claim 25, wherein said light transparent cooling fluid is air and said means for circulating comprises a fan.

27. A low stress work station for providing display images to an operator, said images based upon an electronic signal, said work station comprising:

a light source projecting a beam of light along an optical path;

a rear projection screen located at one end of said optical path and in a position to be viewed by said operator;

a control, responsive to said electronic signal, for selectively and locally energizing said crystal means;

a twisted nematic liquid crystal display, located along said optical path and responsive to said control;

a back polarizer, at least partially disposed in said beam and located between said crystal means and said light source, for polarizing light passing therethrough; and

a front analyzer, at least partially disposed in said beam and located between said crystal means and said rear projection screen, for allowing light of a selected polarization to pass therethrough and for blocking light not having said selected polarization.