Visual display system and exposure control apparatus

• US 5,418,546 A
• Filed: 08/07/1992
• Issued: 05/23/1995
• Est. Priority Date: 08/20/1991
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Nakagakiuchi, Susumu, Ueda, Shinobu
• Primary Examiner(s): BRIER, JEFFERY A
• Application Number:
  US07/925,880
• Time in Patent Office: 1,019 Days
• Field of Search: 345/30, 345/31, 345/32, 345/84, 345/85, 345/108, 345/109, 358/213.13, 358/226, 358/228, 348/770, 348/771
• US Class Current: 345/85
• CPC Class Codes: G09G 3/002 to project the image of a two-dimensional display, such as an array of light emitting or modulating elements or a CRT
• CPC Class Codes: G09G 3/02 by tracing or scanning a light beam on a screen
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene
• CPC Class Codes: H04N 5/7416 involving the use of a spatial light modulator, e.g. a light valve, controlled by a video signal
• CPC Class Codes: H04N 9/312 Driving therefor driving of electronic spatial light modulators in displays other than projection devices G09G3/34, G09G3/36; control of liquid crystal elements G02F1/133; control of micromechanical modulators G02B26/08
• CPC Class Codes: H04N 9/3129 scanning a light beam on the display screen scanning a light beam on a screen in displays other than projection devices G09G3/02; scanning systems in general G02B26/10; projectors using laser light sources in general H04N9/3161
• CPC Class Codes: H04N 9/3194 including sensor feedback

Abstract

A visual display system in which light from a light source is modulated by a spatial light modulator having a plurality of controllable elements arranged in a first dimension. The modulated light is scanned by an optical scanning device along a second dimension to display an image. An exposure control apparatus has a lens, a photoelectric conversion device, and a spatial light modulator. The spatial light modulator varies the amount of light received from the lens and supplied to the photoelectric conversion device, thereby controlling the exposure of the image focused by the lens.

Claims

1. A visual display system, comprising:

a light source emitting a light beam;

an image forming surface having a first and second dimension;

a spatial light modulator including a plurality of linearly arranged controllable elements, said controllable elements modulating said light beam to form an image line, said image line representing a line of a image along said first dimension; and

an optical scanning device scanning said image line across a portion of said image forming surface only in a direction of said second dimension.

2. A visual display system as set forth in claim 1, wherein said optical scanning device is one selected from the group consisting of a reflecting mirror, a prism and a lens.

3. A visual display system as set forth in claim 1, wherein said optical scanning device selectively scans said image line according to the wavelength thereof to display a color on said image forming surface.

4. A visual display system as set forth in claim 1, wherein said optical scanning device has a movable reflecting or refracting surface.

5. A visual display system as set forth in claim 1, wherein said optical scanning device has a double-sided reflecting mirror whose reflecting surfaces are turned to scan said image line.

6. A visual display system as set forth in claim 1, wherein said optical scanning device has a plane prism whose refracting surfaces are turned to scan said image line.

7. A visual display system as set forth in claim 1, wherein said optical scanning device is of polygonal columnar shape, with a polygonal cross section, whose reflecting or refracting surfaces are turned to scan said image line.

8. A visual display system as set forth in claim 1, wherein said optical scanning device has a plurality of reflecting or refracting surfaces, each of the reflecting or refracting surfaces having filter characteristic that reflects or refracts light of a particular wavelength or wavelength range.

9. A visual display system as set forth in claim 1, wherein said optical scanning device has a plurality of reflecting or refracting surfaces, each of the reflecting or refracting surfaces being periodically provided with filter characteristic that reflects or refracts light of a particular wavelength or wavelength range.

10. A visual display system as set forth in claim 1, wherein said optical scanning device has at least two reflecting or refracting surfaces, and said reflecting or refracting surfaces complete at least one cycle of rotation within one cycle period of the critical flicker frequency of the human eye.

11. A visual display system as set forth in claim 1, wherein said light source emits white light.

12. A visual display system as set forth in claim 1, wherein said light source has at least three light emitting elements that radiate light at the central wavelengths approximately equal to red, blue, and green colors, respectively.

13. A visual display system as set forth in claim 1, wherein said light source emits, as said light beam, a pulse light, said pulse light being set in an on-state for a period of time equal to one line display period, an image displayed on said image forming surface consists of a plurality of image lines, said line display period is a period of time for said optical scanning device to scan one image line on said image forming surface.

14. A visual display system as set forth in claim 13, further comprising means for synchronizing the scanning of said optical scanning device, the control of said controllable elements, and the emission of said pulse light.

15. A visual display system as set forth in claim 14, wherein said means for synchronizing causes said optical scanning device to complete at least one scan of said image forming surface within one cycle period of the critical flicker frequency of the human eye.

16. A visual display system as set forth in claim 1, wherein the scanning time of said optical scanning device corresponds to the dimensions of said spatial light modulator.

17. A visual display system as set forth in claim 1, wherein

said optical scanning device includes at least two scanning sections and rotates to scan said image line across said portion of said image forming surface, and said optical scanning device rotates incrementally through an angle to display one image line on said image forming surface.

18. A visual display system as set forth in claim 1, wherein said spatial light modulator controls said controllable elements more than one time within one cycle period of the critical flicker frequency of the human eye.

19. A visual display system as set forth in claim 1, wherein

said light source emits, as said light beam, a pulse light, said pulse light being set in an on-state for a period of time equal to one line display period, an image displayed on said image forming surface consists of a plurality of image lines, said line display period is a period of time for said optical scanning device to scan one image line on said image forming surface;

and

wherein said spatial light modulator controls said controllable elements more than one time during said on-state.

20. A visual display system as set forth in claim 1, further comprising a processor for receiving an image signal representing an image, said image consisting of a plurality of lines in said first dimension arranged along said second dimension, for controlling said spatial light modulator to form an image line corresponding to one of said plurality of lines, and for controlling said optical scanning device to display said image line on said image forming surface at a position along said second dimension corresponding to a position of said one of said plurality of lines in said second dimension of said image.

21. A visual display system as set forth in claim 20, wherein said processor controls said spatial light modulator to modulate said light beam to sequentially form image lines corresponding to said plurality of image lines, and controls said optical scanning device in synchronization with the control of said spatial light modulator to position said image lines along said second dimension on said image forming surface to display said image.

22. A visual display system as set forth in claim 21, further comprising means for synchronizing the rotation of said optical scanning device and the control of said controllable elements.

23. A visual display system as set forth in claim 1, further comprising an optical shutter disposed on the light emitting side of said light source, said optical shutter being set in an open-state for a period of time equal to one line display period, an image displayed on said image forming surface consists of a plurality of image lines, said line display period is a period of time for said optical scanning device to scan one image line on said image forming surface.

24. A visual display system as set forth in claim 23, wherein said spatial light modulator controls said controllable elements more than one time during said open-state.

25. A visual display system comprising:

a light source disposed in a first optical path;

an image forming surface disposed in a second optical path;

a spatial light modulator disposed in said first and second optical paths and composed of a plurality of controllable elements arranged in a line;

an optical scanning device, disposed between said spatial light modulator and said image forming surface, for scanning the light reflected from said spatial light modulator; and

an optical shutter disposed on the light emitting side of said light source, said optical shutter being set in an open-state for a period of time equal to one line display period, an image displayed on said image forming surface consists of a plurality of image lines, said line display period is a period of time for said optical scanning device to scan one image line on said image forming surface.

26. A visual display system as set forth in claim 25, wherein said spatial light modulator controls said controllable elements more than one time during said open-state.

27. A visual display system as set forth in claim 25, further comprising means for synchronizing the scanning of said optical scanning device, the control of said controllable elements, and the actuation of said optical shutter.

28. A visual display system as set forth in claim 27, wherein said means for synchronizing causes said optical scanning device to complete at least one scan of said image forming surface within one cycle period of the critical flicker frequency of the human eye.

29. A visual display system comprising:

a light source disposed in a first optical path;

an image forming surface disposed in a second optical path;

a spatial light modulator disposed in said first and second optical paths and composed of a plurality of controllable elements arranged in a line;

an optical scanning device, disposed between said spatial light modulator and said image forming surface, for scanning the light reflected from said spatial light modulator; and

wherein

said spatial light modulator controls said controllable elements more than one time within one cycle period of the critical flicker frequency of the human eye.

30. A visual display system comprising:

a light source disposed in a first optical path;

an image forming surface disposed in a second optical path;

a spatial light modulator disposed in said first and second optical paths and composed of a plurality of controllable elements arranged in a line;

an optical scanning device, disposed between said spatial light modulator and said image forming surface, for scanning the light reflected from said spatial light modulator; and

wherein

said light source emits, as said light beam, a pulse light, said pulse light being set in an on-state for a period of time equal to one line display period, an image displayed on said image forming surface consists of a plurality of image lines, said line display period is a period of time for said optical scanning device to scan one image line on said image forming surface; and

wherein

said spatial light modulator controls said controllable elements more than one time during said on-state.

31. A visual display system comprising:

a light source disposed in a first optical path;

an image forming surface disposed in a second optical path;

a spatial light modulator disposed in said first and second optical paths and composed of a plurality of controllable elements arranged in a line;

an optical scanning device, disposed between said spatial light modulator and said image forming surface, for scanning the light reflected from said spatial light modulator; and

wherein

the rotation of said optical scanning device is controlled in such a manner that the scanning section thereof is turned incrementally with an angle equivalent to the angle through which to scan an image line formed by said controllable elements of said spatial light modulator.

32. An exposure control apparatus comprising:

a lens for focusing an image light representing an image;

a photoelectric conversion device for converting light into an electrical signal;

a light source emitting a light beam;

a spatial light modulator receiving said image light and said light beam, and having a plurality of controllable elements; and

a control unit controlling, individually and simultaneously, the plurality of controllable elements of said spatial light modulator in a first and second switching mode based on said electrical signal output from said photoelectric conversion device, in the first switching mode, said control means switching the states of said controllable elements between a first state, in which said received image light is guided to said photoelectric conversion device, and a second state in which said received image light is not guided to said photoelectric conversion device, and in the second switching mode said control means switching the states of the controllable elements between a third state, in which the received light is guided to said lens, and a fourth state in which said received light beam is not guided to lens.

33. An exposure control apparatus as set forth in claim 32, further comprising:

an exposure analysis unit analyzing an exposure level of said image based on said electrical signal; and

wherein

said control unit controls said controllable elements based on output from said exposure analysis unit.