Image display apparatus

• US 20070252918A1
• Filed: 04/11/2007
• Published: 11/01/2007
• Est. Priority Date: 04/12/2006
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Yokoyama, Toshifumi, Furuya, Hiroyuki, Itoh, Tatsuo, Mizuuchi, Kiminori, Kurozuka, Akira, Yamamoto, Kazuhisa
• Granted Patent: US 8,350,789 B2
• Time in Patent Office: Days
• US Class Current: 348/742
• 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;

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

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

wherein;

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

a scan timing of the beam scan portion is synchronized with the light emitting timing of the laser light source.

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

a scan cycle of the beam scan portion, T_scan, and a light emitting time of the laser light source, T<sub>Laser—

ON</sub>, satisfy an equation expressed as;

T<sub>Laser—

ON</sub>=n·

T_scan

where n is an integer.

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

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

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

4. The image display apparatus according to claim 2, wherein:

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

5. The image display apparatus according to claim 2, wherein:

the spatial light modulator is a micro electromechanical system element.

6. The image display apparatus according to claim 2, wherein:

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

to 5°

both inclusive.

7. The image display apparatus according to claim 2, wherein:

the laser light source is a green laser light source, and

wherein the green laser light source includes;

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, and

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

8. The image display apparatus according to claim 2, wherein:

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

9. The image display apparatus according to claim 2, 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

.

10. The image display apparatus according to claim 2, wherein:

the number of the plural fields is an even number.

11. The image display apparatus according to claim 2, wherein:

the beam scan portion is driven at a resonance frequency.

12. The image display apparatus according to claim 2, 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.

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

the spatial light modulator spatially digital-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.

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

the scan direction of the beam scan portion inverts in 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.

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

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

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

16. The image display apparatus according to claim 14, wherein:

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

17. The image display apparatus according to claim 14, wherein:

the spatial light modulator is a micro electromechanical system element.

18. The image display apparatus according to claim 14, wherein:

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

to 5°

both inclusive.

19. The image display apparatus according to claim 14, wherein:

the laser light source is a green laser light source, and

wherein the green laser light source includes;

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, and

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

20. The image display apparatus according to claim 14, wherein:

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

21. The image display apparatus according to claim 14, 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

.

22. The image display apparatus according to claim 14, wherein:

the number of the plural fields is an even number.

23. The image display apparatus according to claim 14, wherein:

the beam scan portion is driven at a resonance frequency.

24. The image display apparatus according to claim 14, 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.

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

the spatial light modulator spatially digital-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.