Image display apparatus

• US 8,350,789 B2
• Filed: 04/11/2007
• Issued: 01/08/2013
• Est. Priority Date: 04/12/2006
• Status: Expired due to Fees

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Furuya, Hiroyuki, Mizuuchi, Kiminori, Yokoyama, Toshifumi, Itoh, Tatsuo, Kurozuka, Akira, Yamamoto, Kazuhisa
• Primary Examiner(s): Lao, Lun-Yi
• Assistant Examiner(s): MERKOULOVA, OLGA VLADIMIROVNA
• Application Number:
  US11/783,693
• Publication Number:
  US 20070252918A1
• Time in Patent Office: 2,099 Days
• Field of Search: 345/84, 345/88, 345/690, 345/83, 353/31, 353/33, 353/34, 353/37, 353/122, 349/22, 349/5, 349 7- 8, 348/751, 348/761, 348/766, 348/790, 348/744
• US Class Current: 345/84
• CPC Class Codes: G02B 27/48 Laser speckle optics
• 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

Abstract

A 2D image display apparatus using a laser light source. By controlling the timing of a scan by a beam scan portion in response to the characteristic of a laser light source and by setting a light emitting time of the laser light source to an integral multiple of a scan cycle of the beam scan portion, it is possible to illuminate a spatial light modulator homogeneously with a laser beam. It is thus possible to display an image at high accuracy without causing a bright line, irregularities in brightness, and contrast deterioration.

Claims

1. An image display apparatus, comprising:

a laser light source;

a beam scan portion that scans a laser beam emitted from the laser light source so that an image of one frame is formed by a continuous display of plural fields;

a spatial light modulator that spatially digitally-modulates the laser beam scanned by the beam scan portion;

a modulator controller that is configured to control the spatial light modulator based on an inputted video signal;

a diffusing member, disposed between the beam scan portion and the spatial light modulator, that diffuses the laser beam scanned by the beam scan portion in a scan direction of the beam scan portion; and

a control portion that is configured to control emitting of the laser beam from the laser light source and scanning of the beam scan portion so as to synchronize a scan timing of the beam scan portion with a light emitting timing of the laser light source,

wherein the control portion controls the laser light source and the beam scan portion to cause the laser beam to reciprocate across a display region of the spatial light modulator once, as the beam scan portion scans in one cycle, so that the entire display region of the spatial light modulator is illuminated by the laser beam,

wherein the control portion controls the laser light source to start the emitting of the laser beam such that the laser beam scanned by the beam scan portion illuminates one end of the display region of the spatial light modulator, and to stop the emitting of the laser beam when the laser beam scanned by the beam scan portion illuminates the one end of the display region of the spatial light modulator after reciprocating across the display region of the spatial light modulator, and

wherein a scan cycle of the beam scan portion, T_scan, which is an interval of time required for the laser beam to reciprocate across the display region of the spatial light modulator once, and a light emitting time of the laser light source, T<sub>Laser —

ON</sub>, which is an interval of time between a timing to start the emitting of the laser beam and a timing to stop the emitting of the laser beam, satisfy an equation expressed as;

T<sub>Laser —

ON</sub>=n·

T_scan, where n is an integer.

2. The image display apparatus according to claim 1, further comprising:

a detection portion that detects an output of the laser light source,

wherein the control portion controls the output of the laser light source according to a detection value of the detection portion.

3. The image display apparatus according to claim 1, wherein:

the spatial light modulator is a liquid crystal on silicon made of ferroelectric liquid crystals.

4. The image display apparatus according to claim 1, wherein:

the spatial light modulator is a micro electro mechanical system element.

5. The image display apparatus according to claim 1, wherein:

an angle of diffusion of the diffusing member is in a range of 3°

to 5°

both inclusive.

6. The image display apparatus according to claim 1, wherein:

the laser light source is a green laser light source including;

a fiber containing a laser activated material and having a fiber grating formed therein;

an exciting light source from which exciting light goes incident on the fiber; and

a wavelength conversion element that converts a fundamental wave of a laser coming out from the fiber to a higher harmonic,

wherein the higher harmonic outputted from the wavelength conversion element is frequency modulated.

7. The image display apparatus according to claim 1, wherein:

the laser light source emits light after scanning by the beam scan portion starts.

8. The image display apparatus according to claim 1, wherein:

the laser light source includes three laser light sources defined as a red laser light source, a blue laser light source, and a green laser light source; and

each field is formed by a continuous display of three color fields in red, blue, and green and a display duty of the three color fields is ⅓

.

9. The image display apparatus according to claim 1, wherein:

the number of the plural fields is an even number.

10. The image display apparatus according to claim 1, wherein:

the beam scan portion is driven at a resonance frequency.

11. The image display apparatus according to claim 1, wherein:

the apparatus is configured in such a manner that when a grayscale image having a grayscale in a direction perpendicular to the scan direction of the beam scan portion is displayed, a variation in a pixel value of each pixel forming the grayscale image that results from a scan by the scan portion is compensated for.

12. The image display apparatus according to claim 11, wherein:

the spatial light modulator spatially digitally-modulates the laser beam scanned by the beam scan portion based on a result achieved with the inverse transformation of a tone curve that follows the variation in the pixel value of each pixel forming the grayscale image.

13. An image display apparatus, comprising:

a laser light source;

a beam scan portion that scans a laser beam emitted from the laser light source, so that an image of one frame is formed by a continuous display of plural fields;

a spatial light modulator that spatially digitally-modulates the laser beam scanned by the beam scan portion;

a modulator controller that is configured to control the spatial light modulator based on an inputted video signal;

a diffusing member, disposed between the beam scan portion and the spatial light modulator, that diffuses the laser beam scanned by the beam scan portion in a scan direction of the beam scan portion; and

a control portion that is configured to control emitting of the laser beam from the laser light source and scanning of the beam scan portion so as to synchronize a scan timing of the beam scan portion with a light emitting timing of the laser light source,

wherein the control portion is configured to control the scan direction of the beam scan portion so as to invert an order of display of the plural fields, as a scan frequency of the beam scan portion, fs, and a light emitting frequency of the laser light source, fi, satisfy an equation expressed as;

fs=(n−

0.5)fi, where n is an integer,

wherein the control portion is configured to control the laser light source and the beam scan portion to cause the laser beam to scan a display region of the spatial light modulator one way from one end to an opposite end of the display region as the beam scan portion scans in half cycle, and

wherein the control portion is configured to cause the laser light source to start emitting the laser beam such that the laser beam scanned by the beam scan portion illuminates the one end of the display region of the spatial light modulator, and to stop emitting the laser beam when the laser beam scanned by the beam scan portion illuminates the opposite end of the display region of the spatial light modulator.

14. The image display apparatus according to claim 13, further comprising:

a detection portion that detects an output of the laser light source,

wherein the control portion controls the output of the laser light source according to a detection value of the detection portion.

15. The image display apparatus according to claim 13, wherein:

the spatial light modulator is a liquid crystal on silicon made of ferroelectric liquid crystals.

16. The image display apparatus according to claim 13, wherein:

the spatial light modulator is a micro electro mechanical system element.

17. The image display apparatus according to claim 13, wherein:

an angle of diffusion of the diffusing member is in a range of 3°

to 5°

both inclusive.

18. The image display apparatus according to claim 13, wherein:

the laser light source is a green laser light source including;

a fiber containing a laser activated material and having a fiber grating formed therein;

an exciting light source from which exciting light goes incident on the fiber; and

a wavelength conversion element that converts a fundamental wave of a laser coming out from the fiber to a higher harmonic,

wherein the higher harmonic outputted from the wavelength conversion element is frequency modulated.

19. The image display apparatus according to claim 13, wherein:

the laser light source emits light after scanning by the beam scan portion starts.

20. The image display apparatus according to claim 13, wherein:

the laser light source includes three laser light sources defined as a red laser light source, a blue laser light source, and a green laser light source; and

each field is formed by a continuous display of three color fields in red, blue, and green and a display duty of the three color fields is ⅓

.

21. The image display apparatus according to claim 13, wherein:

the number of the plural fields is an even number.

22. The image display apparatus according to claim 13, wherein:

the beam scan portion is driven at a resonance frequency.

23. The image display apparatus according to claim 13, wherein:

the apparatus is configured in such a manner that when a grayscale image having a grayscale in a direction perpendicular to the scan direction of the beam scan portion is displayed, a change of a pixel value of each pixel forming the grayscale image that results from a scan by the scan portion is compensated for.

24. The image display apparatus according to claim 23, wherein:

the spatial light modulator spatially digitally-modulates the laser beam scanned by the beam scan portion based on a result achieved with the inverse transformation of a tone curve that follows the variation in the pixel value of each pixel forming the grayscale image.