Frequency Control of Despeckling

• US 20130021586A1
• Filed: 09/25/2012
• Published: 01/24/2013
• Est. Priority Date: 12/07/2010
• Status: Abandoned Application

• Current Assignee: Projection Ventures Inc.
• Original Assignee: Laser Light Engines, Inc.
• Inventors: Lippey, Barret
• Application Number:
  US13/625,933
• Publication Number:
  US 20130021586A1
• Time in Patent Office: Days
• US Class Current: 353/69
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: H01S 2301/02 ASE (amplified spontaneous emission), noise; Reduction thereof
• 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: H01S 3/0092 Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity nonlinear frequency conversion per se G02F1/35
• CPC Class Codes: H01S 3/094003 the pumped medium being a fibre
• CPC Class Codes: H01S 3/094076 Pulsed or modulated pumping H01S3/1024 takes precedence
• CPC Class Codes: H01S 3/1305 Feedback control systems
• CPC Class Codes: H01S 3/2391 emitting at different wavelengths
• CPC Class Codes: H01S 3/302 in an optical fibre
• CPC Class Codes: H04N 9/3161 using laser light sources using laser beams scanning the display screen H04N9/3129

Abstract

A method and apparatus that reduces laser speckle by using stimulated Raman scattering in an optical fiber. The pulse repetition frequency of the laser is adjusted to control aspects of the laser light such as color or despeckling. In DLP projection systems, an optical monitor may be used to send information to a bit sequence, and the bit sequence may control the pulse repetition frequency of the laser based on the optical monitor signal.

Claims

1. A method of despeckling comprising:

generating a laser beam;

focusing the laser beam into an optical fiber;

generating stimulated Raman scattering light in the optical fiber;

using the stimulated Raman scattering light to form a projected digital image; and

adjusting a frequency of the laser beam to control a first aspect of the projected digital image.

2. The method of claim 1 wherein the first aspect of the projected digital image is a primary color of the projected digital image.

3. The method of claim 2 wherein the primary color of the projected digital image is green.

4. The method of claim 1 further comprising:

adjusting a power of the laser beam to control a second aspect of the projected digital image.

5. The method of claim 4 wherein the second aspect of the projected digital image is a brightness of the projected digital image.

6. The method of claim 1 wherein the first aspect of the projected digital image is a speckle characteristic of the projected digital image.

7. The method of claim 1 wherein the first aspect of the projected digital image is a brightness of the projected digital image.

8. The method of claim 1 wherein the projected digital image is formed by using a liquid crystal on silicon (LCOS) light valve.

9. The method of claim 1 wherein the projected digital image is formed by using a digital light processing (DLP) light valve.

10. The method of claim 9 wherein the DLP light valve is operated with a bit sequence;

and the bit sequence is adapted for use with the adjustable frequency of the laser beam.

11. The method of claim 10 further comprising:

generating an optical monitor signal that measures the first aspect of the projected digital image.

12. The method of claim 11 further comprising:

sending the optical monitor signal to the bit sequence; and

using the bit sequence to control the frequency of the laser beam.

13. An optical apparatus comprising:

An optical fiber;

wherein a stimulated Raman scattering in the optical fiber reduces a speckle characteristic of a light output from the optical fiber; and

a frequency of the light output from the optical fiber is adjusted to control a first aspect of the light output from the optical fiber.

14. The apparatus of claim 13 wherein the first aspect of the light output from the optical fiber is the color of the light output from the optical fiber.

15. The apparatus of claim 14 wherein the color of the light output from the optical fiber is green.

16. The apparatus of claim 13 further comprising:

a laser light source that illuminates the optical fiber;

wherein the laser light source has an adjustable power output; and

the adjustable power output is adjusted to control a second aspect of the light output from the optical fiber.

17. The apparatus of claim 16 wherein the second aspect of the light output from the optical fiber is a brightness of the light output from the optical fiber.

18. The apparatus of claim 13 wherein the first aspect of the light output from the optical fiber is a speckle characteristic of the light output from the optical fiber.

20. The apparatus of claim 13 further comprising:

a digital projection system that forms a digital projected image.

21. The apparatus of claim 20 wherein the digital projection system comprises a liquid crystal on silicon (LCOS) light valve.

22. The apparatus of claim 20 wherein the digital projection system comprises a digital light processing (DLP) light valve.

23. The apparatus of claim 22 wherein the DLP light valve is operated with a bit sequence;

and the bit sequence is adapted for use with the adjustable frequency of the light output from the optical fiber.

24. The apparatus of claim 23 further comprising:

an optical monitor that measures the first aspect of the light output from the optical fiber.

25. The apparatus of claim 24 wherein the optical monitor sends a signal to the bit sequence and the bit sequence controls the frequency of the light output from the optical fiber.

19. The apparatus of claim 131 wherein the first aspect of the light output from the optical fiber is a brightness of the light output from the optical fiber.