Exposure control apparatus including a spatial light modulator

• US 5,546,128 A
• Filed: 03/10/1995
• Issued: 08/13/1996
• Est. Priority Date: 08/20/1991
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation), Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Nakagakiuchi, Susumu, Ueda, Shinobu
• Primary Examiner(s): Greening, Wendy
• Application Number:
  US08/402,057
• Time in Patent Office: 522 Days
• Field of Search: 348/362, 348/335, 348/207, 348/203, 348/771, 359/223, 359/224
• US Class Current: 348/362
• 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

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 reflected to the photoelectric conversion device. A control unit controls the spatial light modulator, and thus the exposure of the image focused on the lens, based on output from the photoelectric conversion device.

Claims

1. An exposure control apparatus comprising:

a lens system;

a spatial light modulator receiving light passing through said lens system and having a plurality of controllable elements;

a photoelectric conversion device for converting said received light reflected from said spatial light modulator into an electrical signal; and

control means for controlling, individually and simultaneously, the plurality of controllable elements of said spatial light modulator on the basis of the output from said photoelectric conversion device, in order to switch the states of the controllable elements between a first state, in which at least a portion of said received light is guided to said photoelectric conversion device, and a second state in which said received light is not guided to said photoelectric conversion device.

2. The exposure control apparatus set forth in claim 1, wherein said plurality of controllable elements are a plurality of reflective members.

3. An exposure control apparatus comprising:

a lens for focusing image light representing an image;

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

a photoelectric conversion device for converting said received image light reflected from said spatial light modulator into an electrical signal;

exposure analysis means for calculating a luminance level of said image as a whole based on said electrical signal output by said photoelectric conversion device; and

control means for controlling, individually and simultaneously, the plurality of controllable elements of said spatial light modulator based on an output of said exposure analysis means, in order to switch the states of the controllable elements between a first state, in which at least a portion of 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.

4. The exposure control apparatus set forth in claim 3, wherein said plurality of controllable elements are a plurality of reflective members.

5. An exposure control apparatus as set forth in claim 3, wherein

said exposure analysis means calculates a luminance level of said image as a whole based on said electrical signal, and compares said luminance level to a predetermined threshold;

and

said control means changes states of a number of said controllable elements based on the results of said comparison performed by said exposure analysis means.

7. A method of exposure control as set forth in claim 5, wherein

said step (c) further comprises the step of (c1) comparing said luminance level to a predetermined threshold, and (c2) outputting a control signal to said spatial light modulator based on output of said step (c1);

and

said step (d) comprises the step of (d1) changing states of a number of said controllable elements based on said control signal.

6. A method of controlling image exposure, comprising the step of:

(a) focusing image light, representing an image, on a spatial light modulator, said spatial light modulator having a plurality of controllable elements;

(b) converting said image light reflected by said spatial light modulator and received by a photoelectric conversion device into an electrical signal;

(c) calculating a luminance level of said image as a whole based on said electrical signal; and

(d) individually controlling said plurality of controllable elements based on output of said step (c) to switch at least a portion of said plurality of controllable elements between a first state, in which said image light is guided to said photoelectric device, and a second state, in which said image light is not guided to said photoelectric device.

8. The exposure control apparatus set forth in claim 6, wherein said plurality of controllable elements are a plurality of reflective members.

9. A method of controlling image exposure, comprising the step of:

(a) focusing image light, representing an image, on a spatial light modulator, said spatial light modulator having a plurality of controllable elements;

(b) converting said image light reflected by said spatial light modulator and received by a photoelectric conversion device into an electrical signal;

(c) calculating a luminance level of a part of said image based on said electrical signal; and

(d) individually controlling said plurality of controllable elements based on output of said step (c) to switch said plurality of controllable elements between a first state, in which at least a portion of said image light is guided to said photoelectric device, and a second state, in which said image light is not guided to said photoelectric device.

10. A method of exposure control as set forth in claim 9, wherein

said step (c) further comprises the step of (c1) comparing said luminance level to a predetermined threshold, and (c2) outputting a control signal to said spatial light modulator based on output of said step (c1), said output signal designating said part of said image;

and

said step (d) comprises the step of (d1) changing states of a number of said controllable elements corresponding to said part of said image based on said control signal.

11. The exposure control apparatus set forth in claim 9, wherein said plurality of controllable elements are a plurality of reflective members.

12. An exposure control apparatus comprising:

a lens for focusing image light representing an image;

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

a photoelectric conversion device for converting said image light reflected by said spatial light modulator into an electrical signal;

exposure analysis means for calculating a luminance level of a part of said image based on said electrical signal output by said photoelectric conversion device; and

control means for controlling, individually and simultaneously, the plurality of controllable elements of said spatial light modulator based on output of said exposure analysis means, in order to switch the states of the controllable elements between a first state, in which at least a portion of 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.

13. An exposure control apparatus as set forth in claim 12, wherein

said exposure analysis means calculates a luminance level of a part of said image based on said electrical signal, compares said luminance level to a predetermined threshold, and outputs an address signal designating said part of said image;

and

said control means changing states of a number of said controllable elements corresponding to said part of said image based on results of said comparison and said address signal.

14. The exposure control apparatus set forth in claim 12, wherein said plurality of controllable elements are a plurality of reflective members.

15. An exposure control apparatus comprising:

a lens system;

a spatial light modulator receiving light passing through said lens system and having a plurality of controllable elements;

a photoelectric conversion device for converting said received light reflected from said spatial light modulator into an electrical signal; and

control means for controlling, individually and simultaneously, the plurality of controllable elements of said spatial light modulator on the basis of said electrical signal.

16. The exposure control apparatus set forth in claim 15, wherein said plurality of controllable elements are a plurality of reflective members.

17. An exposure control apparatus comprising:

a lens system for focusing image light representing an image;

a light source emitting a source light;

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

a photoelectric conversion device for converting said image light received via said spatial light modulator into an electrical signal; and

control means for controlling, individually and simultaneously, said plurality of controllable elements of said spatial light modulator based on said electrical signal to switch states of said controllable elements from a first state, in which said source light is guided through said lens system, and a second state, in which said source light is not guided through said lens system.

18. The exposure control apparatus set forth in claim 17, wherein in said second state at least a portion of said received image light is guided to said photoelectric conversion device, and in said first state said image light is not guided to said photoelectric conversion device.

19. The exposure control apparatus set forth in claim 17, wherein said spatial light modulator guides said image light to said photoelectric conversion device by reflecting said image light.

20. The exposure control apparatus set forth in claim 17, wherein said plurality of controllable elements are a plurality of reflective members.