Illuminating optical device in image display device and image display device

• US 7,433,126 B2
• Filed: 07/02/2003
• Issued: 10/07/2008
• Est. Priority Date: 07/11/2002
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Kikuchi, Hiroki, Hashimoto, Shigeki, Oka, Michio
• Primary Examiner(s): Chang; Audrey Y
• Application Number:
  US10/489,152
• Publication Number:
  US 20040257664A1
• Time in Patent Office: 1,924 Days
• Field of Search: 359/572, 359/577, 359/636, 359/618, 359/627, 359/707, 359/237, 385/115, 385/116, 385/33, 362/552, 362/553, 372/93, 372/25, 372/108, 372/26
• US Class Current: 359/577
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• CPC Class Codes: G02B 19/0057 in the form of a laser diode array, e.g. laser diode bar semiconductor laser arrays with beam combining arrangement H01S5/4012
• CPC Class Codes: G02B 2207/117 Adjustment of the optical path length
• CPC Class Codes: G02B 27/1033 having a single light modulator for all colour channels
• CPC Class Codes: G02B 27/123 The splitting element being a lens or a system of lenses, including arrays and surfaces with refractive power
• CPC Class Codes: G02B 27/143 using macroscopically faceted or segmented reflective surfaces
• CPC Class Codes: G02B 27/144 using partially transparent surfaces without spectral selectivity G02B27/147 takes precedence
• 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

Speckle noise is reduced to increase image quality in an image display apparatus such as a projection display or the like.

An illuminating optical device in an image display apparatus (1) applies a laser beam L to a GLV (spatial modulator) (6) and modulates the laser beam based on an image signal input to the GLV to display an image. A plurality of laser beams (1, 1, . . . ) each having an optical path difference greater than the coherence length of the laser beam are applied to the GLV.

Claims

1. An apparatus for improving quality of an image display by reducing laser speckle effects through reducing coherence of a laser, the apparatus comprising:

a reflective spatial light modulator configured to have an image signal input;

an optical component configured to introduce an optical path difference between a plurality of laser beams originating from a laser beam that is greater than or equal to a coherence length of the laser beam, the optical component comprising;

a polarizing separator configured to accept a polarized laser beam comprising a first polarized component and a second polarized component and spatially separate the first polarized component of the polarized laser beam from the second polarized component of the polarized laser beam by directing the first polarized component and the second polarized component in different respective first and second directions;

an optical path difference generator configured to accept the first polarized component from the polarizing separator and delay the first polarized component with respect to the second polarized component to develop a first optical path difference between the first polarized component and the second polarized component, the first optical path difference being greater than a coherence length of the polarized laser beam, wherein the first optical path difference is developed by directing the first polarized component through a series of mirrors and back toward the polarizing separator;

wherein the polarizing separator is further configured to combine the first and second polarized components with the first optical path difference therebetween to form a low coherence laser beam; and

parallel reflection surfaces configured to accept the low coherence laser beam and generate the plurality of laser beams from the low coherence laser beam, at least some of the plurality of laser beams being delayed by the parallel reflection surfaces to introduce a second optical path difference between each of the plurality of laser beams, the second optical path difference being greater than the coherence length of the polarized laser beam; and

a deflecting optical component configured to direct the plurality of laser beams to the reflective spatial light modulator such that the plurality of laser beams converge and focus on the reflective spatial light modulator at different angles as viewed from a perspective along the longitudinal direction of the spatial light modulator, the first optical path difference and the second optical path difference serving to reduce the coherence of the plurality of laser beams.

2. The image display apparatus according to claim 1, wherein the parallel reflection surfaces comprise a total reflection surface formed on one of the parallel reflection surfaces and a semi-transmissive reflection surface having a predetermined transmittance formed on the other of the parallel reflection surfaces, the arrangement being such that the low coherence laser beam is introduced into the multiple reflection plate at a predetermined incident angle from an entrance window which is formed by removing a portion of the total reflection surface, wherein the low coherence laser beam undergoes multiple reflections and is partly emitted from the semi-transmissive reflection surface, so that the low coherence laser beam is separated into the plurality of laser beams.

3. The image display apparatus according to claim 2, wherein the reflective spatial light modulator comprises a grating light valve.

4. The image display apparatus according to claim 1, wherein the reflective spatial light modulator comprises a grating light valve.

5. The image display apparatus according to claim 1, wherein the reflective spatial light modulator comprises a grating light valve.

6. The image display apparatus of claim 1, further comprising:

a line generator component configured to shape the plurality of laser beams to have linear beam configurations.

7. The image display apparatus of claim 1, wherein the polarizing separator comprises a polarization beam splitter, the polarization beam splitter being adapted to reflect the first polarized component in a first direction and reflect the second polarized component in a second direction, the first direction being perpendicular to the second direction.

8. The image display apparatus of claim 1, wherein the polarization rotator separates the laser beam into a P-polarized component and an S-polarized component.

9. The apparatus of claim 1, further comprising:

a line generator optical system to accept the plurality of laser beams from the parallel reflection surfaces and make uniform the intensity of each of the plurality of laser beams and output the uniform plurality of laser beams to the deflecting optical component.

10. A method for improving quality of an image display by reducing laser speckle effects through reducing coherence of a laser, the method comprising acts of:

introducing an optical path difference between a plurality of laser beams originating from a laser beam, the optical path difference being greater than or equal to a coherence length of the laser beam, wherein introducing the optical path difference comprises acts of;

directing a first polarized component and a second polarized component of a polarized laser beam in different respective first and second directions to spatially separate the first polarized component of the polarized laser from the second polarized component of the laser beam;

developing a first optical path difference between the first polarized component and the second polarized component of the polarized laser beam, the first optical path difference being greater than a coherence length of the polarized laser beam, wherein developing the first optical path difference comprises directing the first polarized component through a series of mirrors and back toward the polarizing separator to delay the first polarized component with respect to the second polarized component;

combining the first and second polarized components with the first optical path difference therebetween to form a low coherence laser beam; and

separating the low coherence laser beam into the plurality of laser beams by parallel reflection surfaces, at least some of the plurality of laser beams being delayed to introduce a second optical path difference between each of the plurality of laser beams, the second optical path difference being greater than the coherence length of the polarized laser beam; and

directing the plurality of laser beams to a reflective spatial light modulator such that the plurality of laser beams converge on the reflective spatial light modulator, the first optical path difference and the second optical path difference serving to reduce the coherence of the plurality of laser beams.

11. The method according to claim 10, wherein the act of separating the low coherence laser beam into the plurality of laser beams is performed by parallel reflection surfaces with a total reflection surface formed on one of the parallel reflection surfaces and a semi-transmissive reflection surface having a predetermined transmittance formed on the other of the parallel reflection surfaces, the arrangement being such that the laser beam is introduced into the multiple reflection plate at a predetermined incident angle from an entrance window which is formed by removing a portion of the total reflection surface, wherein the low coherence laser beam undergoes multiple reflections and is partly emitted from the semi-transmissive reflection surface, so that the low coherence laser beam is separated into the plurality of laser beams.

12. The method according to claim 11, wherein the reflective spatial light modulator comprises a grating light valve.

13. The method according to claim 10, wherein the reflective spatial light modulator comprises a grating light valve.

14. The method according to claim 10, wherein the reflective spatial light modulator comprises a grating light valve.

15. The method of claim 10, further comprising an act of:

shaping the plurality of laser beams to have linear beam configurations.

16. The method of claim 10, wherein spatially separating the first polarized component and the second polarized component comprises reflecting the first polarized component in a first direction and reflecting the second polarized component in a second direction, the first direction being perpendicular to the second direction.

17. The method of claim 10, wherein first polarized component and the second polarized component comprise a P-polarized component and an S-polarized component.

18. The method of claim 10, further comprising:

making uniform the intensities of each of the plurality of laser beams prior to directing the plurality of laser beams to the reflective spatial light modulator.