Laser projector with reduced speckle

• US 9,482,877 B2
• Filed: 04/12/2011
• Issued: 11/01/2016
• Est. Priority Date: 04/12/2011
• Status: Active Grant

• Current Assignee: Barco NV
• Original Assignee: Barco NV
• Inventors: Janssens, Peter
• Primary Examiner(s): Dowling, William C
• Application Number:
  US14/110,807
• Publication Number:
  US 20140028985A1
• Time in Patent Office: 2,030 Days
• Field of Search: 353/38, 353/31, 353/33, 353/34, 353/37, 353/85
• US Class Current: 1/1
• CPC Class Codes: G02B 27/0905 Dividing and/or superposing multiple light beams
• CPC Class Codes: G02B 27/0927 Systems for changing the beam intensity distribution, e.g. Gaussian to top-hat
• CPC Class Codes: G02B 27/0955 Lenses lenses per se G02B3/00
• 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: G03B 21/2033 LED or laser light sources
• CPC Class Codes: G03B 21/208 Homogenising, shaping of the illumination light
• CPC Class Codes: H04N 9/3152 for shaping the light beam beam shaping per se G02B27/09

Abstract

The present invention provides a light source for a projector system, and method of operating the light source as well as a projector system that provides:

i. a substantially uniform brightness across the surface of an image modulator, and

ii. at each point of the surface of the image modulator a more uniform filling of the available angular space.

Embodiments of the present invention use a laser light source for use with an image modulator, the light source emitting light with multiple wavelengths for at least one primary color and a light integrator system that for each of the wavelengths is adapted to provide:

i. a substantially uniform brightness across the surface of the image modulator, and

ii. at each point of the surface of the image modulator a more uniform filling of the available angular space.

Claims

1. A light source apparatus for use with a projector having a light modulator for receiving a plurality of light beams and for projecting the light beams towards a display, comprising:

a laser light source with multiple wavelengths for at least one primary color arranged to output a laser light beam;

an integrator assembly comprising;

a first integrator and a second integrator; and

a first light diffusing element, positioned in between said first integrator and said second integrator, wherein the first light diffusing element is arranged to receive a laser light and forward a plurality of light beams at a range of angles,

the integrator assembly being adapted such that for each of the wavelengths;

a substantially uniform brightness is achieved across the surface of an image modulator and

at each point of the surface of the image modulator a substantially uniform filling of the available angular space is achieved.

2. The light source of claim 1, wherein the integrator assembly is adapted to provide a substantially uniform brightness across the surface of the image modulator and at each point of the surface of the image modulator a substantially uniform filling of the available angular space at each point in time.

3. The light source of claim 1, wherein the first light diffusing element is a diffuser, a lenslet array, a diffraction element, a refractive prism array or a holographic element.

4. The light source of claim 1, wherein any of the first integrator and the second integrator are a rod or a light pipe integrator.

5. The light source of claim 1, wherein any of the first integrator and the second integrator are a fly-eye integrator.

6. A light source apparatus according to claim 1, wherein the rod or light pipe integrator has a variable cross-section along its longitudinal axis.

7. A light source apparatus according to claim 4, wherein the rod or light pipe integrator has a tapered cross-section along its longitudinal axis in at least one dimension.

8. A light source apparatus according to claim 1, further comprising a second light diffusing element positioned in front of the first integrator.

9. A light source apparatus according to claim 1, wherein the first light diffusing element is movable.

10. A light source apparatus according to claim 1, wherein the first light diffusing element is static.

11. A light source apparatus according to claim 1, wherein the first integrator has a different form and/or different length to width ratio compared to the second integrator.

12. A light source apparatus according to claim 11, wherein the first integrator or the second integrator as a length to width ratio of greater than 7.5.

13. A light source apparatus according to claim 1, wherein the first integrator is tapered and the second integrator is non-tapered or vice versa.

14. A light source apparatus according to claim 1, wherein the laser light source comprises an array of light emitting devices, and wherein one of the devices outputs a light beam at one of the plurality of wavelengths.

15. A light source apparatus according to claim 14, wherein multiple devices outputting a light beam at the same wavelength are offset from one another in the array, and are optionally evenly distributed across the array.

16. A light source apparatus according to claim 1, wherein the plurality of wavelengths have an offset of less than 2 nm and optionally more than 0.5 nm from one another.

17. A light source apparatus according to claim 1, wherein a light beam has two orthogonal polarizations.

18. A light source apparatus according to claim 17, wherein the first or second diffuser element does not maintain polarization.

19. A light source apparatus according to claim 17, wherein a time varying retarder is placed after the first and/or second diffuser element.

20. A light source apparatus according to claim 1, wherein the multiple wavelengths are generated by multiple laser emitters.

21. A light source apparatus according to claim 1, wherein the multiple wavelengths are generated by multiple laser packages.

22. A light source apparatus according to claim 20, in which the number of individual laser emitters contributing to each wavelength is sufficiently high and the first and second diffusing element are static.

23. A projector comprising a light source apparatus-according to claim 1.

24. A projector according to claim 23, wherein said light source apparatus is provided with two orthogonal polarizations for at least one primary color and using a light integrator system that is conceived such that for each of the polarization directions:

v. a substantially uniform brightness is achieved across the surface of the image modulator, and

vi. at each point of the surface of the image modulator a substantially uniform filling of the available angular space is achieved.