Illumination system to eliminate laser speckle and projection system employing the same

• US 20060126184A1
• Filed: 10/25/2005
• Published: 06/15/2006
• Est. Priority Date: 12/15/2004
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Sung-ha, Dho, Sang-whoe
• Granted Patent: US 7,527,384 B2
• Time in Patent Office: Days
• US Class Current: 359/599
• CPC Class Codes: G02B 27/0944 Diffractive optical elements, e.g. gratings, holograms gratings per se G02B5/18; holograms used as optical elements per se G02B5/32
• CPC Class Codes: G02B 27/0994 Fibers, light pipes optical fibers per se G02B6/02
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: G02B 5/1866 Transmission gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G03B 21/005 Projectors using an electronic spatial light modulator but not peculiar thereto
• CPC Class Codes: G03H 2227/03 Means for moving one component G03H1/0476, G03H2001/2695 take precedence
• CPC Class Codes: H01S 3/005 Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B
• CPC Class Codes: H04N 9/3152 for shaping the light beam beam shaping per se G02B27/09
• CPC Class Codes: H04N 9/3161 using laser light sources using laser beams scanning the display screen H04N9/3129

Abstract

An illumination system designed to remove laser speckle and a projection system including the same. The illumination system includes a laser light source having at least one laser, a diffractive optical element to divide a laser beam emitted from the laser light source into a plurality of sub-beams and to periodically move in such a way as to temporally average the speckle of the laser beam, and an optical fiber bundle including a plurality of fibers with the same length to divide the sub-beams into smaller sub-beams. The illumination system divides the laser beam emitted from the laser light source into sub-beams and temporally or spatially averages the sub-beams, thereby effectively reducing or removing laser speckle. The projection system employing the illumination system can provide improved image quality.

Claims

1. An illumination system to remove speckle of a laser beam, the illumination system comprising:

a laser light source having at least one laser to emit a laser beam;

a diffractive optical element to divide the laser beam emitted from the laser light source into a plurality of first sub-beams and to periodically move to temporally average the speckle of the laser beam; and

an optical fiber bundle including a plurality of fibers with the same length to divide the first sub-beams into smaller second sub-beams such that an image is formed according to the smaller second sub-beams.

2. The illumination system of claim 1, wherein each of the plurality of first sub-beams comprises a plurality of beamlets that are focused in an overlaying fashion on one another.

3. The illumination system of claim 1, wherein the diffractive optical element is rotatable with respect to the laser beam.

4. The illumination system of claim 1, further comprising:

a beam-shaping unit to convert a cross-section of each of the second sub-beams into a predetermined shape.

5. An illumination system to remove speckle of a laser beam, the illumination system comprising:

a laser light source having at least one laser to emit a laser beam;

an optical fiber bundle including a plurality of fibers with the same length to divide the laser beam emitted from the laser light source into a plurality of sub-beams; and

a vibrator to vibrate to temporally average the plurality of sub-beams such that an image is formed according to the sub-beams.

6. The illumination system of claim 5, wherein the vibrator comprises:

a reflecting mirror; and

a piezoelectric element to vibrate the reflecting mirror.

7. The illumination system of claim 5, further comprising:

a beam-shaping unit disposed after the optical fiber bundle along a path of the laser beam to convert a cross-section of each of the plurality of sub-beams into a predetermined shape of a display device.

8. The illumination system of claim 7, wherein the beam-shaping unit comprises a light pipe.

9. The illumination system of claim 7, wherein the beam-shaping unit includes a collimating lens and first and second fly-eye lens arrays.

10. The illumination system of claim 8, wherein the beam-shaping unit includes a collimating lens and a beam-shaping diffractive optical element having a predetermined diffractive pattern.

11. An illumination system, comprising:

a laser light source unit to emit a laser beam;

a movable temporal averaging unit to temporally average the laser beam emitted from the laser light source unit; and

an optical fiber bundle having a plurality of optical fibers each having the same length to divide the averaged laser beam emitted from the laser light source unit into a plurality of sub-beams so that an image is formed according to the sub-beams.

12. The illumination system of claim 11, wherein the movable temporal averaging unit comprises:

a diffractive optical element to spatially average the laser beam emitted from the laser light source by dividing the laser beam into a plurality of overlapping beams; and

a driving unit to periodically move the diffractive optical element to temporally average the laser beam emitted from the laser light source.

13. The illumination system of claim 11, wherein the optical fiber bundle is disposed between the laser light source unit and the movable temporal averaging unit, and the movable temporal averaging unit comprises:

a reflective mirror to reflect the plurality of sub-beams output from the optical fiber bundle; and

one or more piezoelectric elements to vibrate the reflective mirror to temporally average the plurality of sub-beams.

14. A projection system to remove speckle of a laser beam, the projection system comprising:

a laser light source having at least one laser to emit a laser beam;

a diffractive optical element to divide the laser beam emitted from the laser light source into a plurality of first sub-beams and to periodically move to temporally average the speckle of the laser beam;

an optical fiber bundle including a plurality of fibers with the same length to divide the first sub-beams into smaller second sub-beams;

a beam-shaping unit to shape the second sub-beams output by the optical fiber bundle;

a display device to produce an image using the second sub-beams shaped by the beam shaping unit;

a screen; and

a projection lens unit to enlarge and project the image onto the screen.

15. The projection system of claim 14, wherein each of the plurality of first sub-beams comprises a plurality of beamlets that are focused in overlaying fashion on one another.

16. The projection system of claim 14, wherein the diffractive optical element is rotable.

17. The projection system of claim 14, further comprising:

a light path changer disposed between the beam-shaping unit and the display device.

18. A projection system to remove speckle of a laser beam, the projection system comprising:

a laser light source having at least one laser to emit a laser beam;

an optical fiber bundle including a plurality of fibers with the same length to divide the laser beam emitted from the laser light source into a plurality of sub-beams;

a beam-shaping unit to shape the plurality of sub-beams output by the optical fiber bundle;

a vibrator to vibrate to temporally average the plurality of sub-beams;

a display device to produce an image using the plurality of sub-beams temporally averaged by the vibrator;

a screen; and

a projection lens unit to enlarge and project the image produced by the display device onto the screen.

19. The projection system of claim 18, wherein the vibrator comprises:

a reflecting mirror; and

a piezoelectric element to vibrate the reflecting mirror.

20. The projection system of claim 18, wherein the beam-shaping unit comprises a light pipe.

21. The projection system of claim 20, further comprising:

a condensing lens disposed between the optical fiber bundle and the beam-shaping unit.

22. The projection system of claim 18, wherein the beam-shaping unit includes a collimating lens and first and second fly-eye lens arrays.

23. The projection system of claim 18, wherein the beam-shaping unit includes a collimating lens and a beam-shaping diffractive optical element having a diffractive pattern.

24. The projection system of claim 18, wherein the display device comprises one of a transmissive liquid crystal display (LCD), a Liquid Crystal on Silicon (LCOS) display, a Deformable Micromirror Device (DMD), and a Grating Light Valve (GLV).

25. An image projection system, comprising:

a laser light source to emit a laser beam;

a first averaging unit to average the laser beam;

an optical bundle to divide the laser beam averaged by the first averaging unit into sub-beams;

a second averaging unit to average the sub-beams; and

a display device to form and display an image using the sub-beams.

26. An image projection system, comprising:

a laser light source to emit a laser beam;

an optical fiber bundle having a plurality of optical fibers to divide the laser beam into first sub-beams;

a collimating lens to collimate the first sub-beams;

a first fly-lens array to divide the collimated first sub-beams into second sub-beams;

a second fly-lens array to focus the second sub-beams to overlap with each other and to provide a beam of a predetermined shape;

an averaging unit to temporally average the beam of the predetermined shape; and

a display device to form and display an image using the temporally averaged beam of the predetermined shape.