Despeckling devices and methods

• US 20130010265A1
• Filed: 07/09/2012
• Published: 01/10/2013
• Est. Priority Date: 07/07/2011
• Status: Active Grant

• Current Assignee: RealD Incorporated
• Original Assignee: Readid Incorporated
• Inventors: Curtis, Kevin
• Granted Patent: US 9,158,063 B2
• Time in Patent Office: Days
• US Class Current: 353/31
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: G02B 6/02 Optical fibres with cladding with or without a coating
• CPC Class Codes: G02B 6/028 with core or cladding having graded refractive index G02B6/02033, G02B6/02295 take precedence
• CPC Class Codes: G02B 6/0281 Graded index region forming part of the central core segment, e.g. alpha profile, triangular, trapezoidal core G02B6/0288, G02B6/0286 take precedence
• CPC Class Codes: G02B 6/0283 Graded index region external to the central core segment, e.g. sloping layer or triangular or trapezoidal layer G02B6/0288, G02B6/0286 take precedence
• CPC Class Codes: G02B 6/0285 Graded index layer adjacent to the central core segment and ending at the outer cladding index
• CPC Class Codes: G02B 6/0286 Combination of graded index in the central core segment and a graded index layer external to the central core segment G02B6/0288 takes precedence
• CPC Class Codes: G02B 6/0288 Multimode fibre, e.g. graded index core for compensating modal dispersion
• CPC Class Codes: G02B 6/421 the intermediate optical component consisting of a short length of fibre, e.g. fibre stub
• CPC Class Codes: G03B 21/2013 Plural light sources
• 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: G03B 33/06 by additive-colour projection apparatus
• CPC Class Codes: H01S 5/02251 using optical fibres
• CPC Class Codes: H01S 5/4012 Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms

Abstract

Illuminating coherent or partially coherent light may be directed over an optical fiber and may be despeckled by vibrating the optical fiber or by increasing the number of modes and modal dispersion. An exemplary embodiment is directed to an optical fiber attached to a vibrating device operable to vibrate the optical fiber above a threshold frequency. Another exemplary embodiment is directed to an optical fiber configured to have a refractive index profile operable to increase the number of modes and modal dispersion.

Claims

1. A laser system comprising:

a laser light source operable to output illuminating light;

a display device operable to receive the illuminating light;

an optical fiber operable directed the illuminating light from the laser light source to the display device;

a vibration device attached to the optical fiber, wherein the vibration device is operable to vibrate at a frequency greater than a threshold frequency so as to reduce speckle.

2. The laser system of claim 1, wherein the threshold frequency is about 20 Hz.

3. The laser system of claim 2, wherein the threshold frequency is about 60 Hz.

4. The laser system of claim 1, further comprises at least one additional vibration device attached the optical fiber, the at least one additional vibration device operable to vibrate at a second frequency greater than the threshold frequency.

5. The laser system of claim 1, further comprising a controller operable to receive information about speckle in the illuminating light at the display device and control the vibration device depending on the information.

6. The laser system of claim 1, wherein a portion of the optical fiber is coiled, and the vibration device is attached to the portion.

7. The laser system of claim 1, wherein the optical fiber has a core extending along a central longitudinal axis and a cladding layer covering the core, the core having a refractive index profile defined from the central longitudinal axis to a longitudinal edge, the refractive index profile comprising a first refractive index at the longitudinal edge that is greater than a second refractive index at the longitudinal axis.

8. A method of providing illumination, comprising:

outputting illuminating light from a laser light source;

directing the illuminating light through an optical fiber to a display device; and

vibrating the optical fiber at a frequency greater than a threshold frequency so as to reduce speckle.

9. The method of claim 8, further comprising:

receiving information about speckle in the illuminating light; and

adjusting the vibrating of the optical fiber according to the information about speckle.

10. The method of claim 8, wherein the threshold frequency is about 20 Hz.

11. The method of claim 8, wherein the threshold frequency is about 60 Hz.

12. The method of claim 8, wherein vibrating the optic fiber comprises vibrating the optic fiber at two or more different longitudinal locations along the optic fiber.

13. A laser system comprising:

a laser light source operable to output illuminating light;

a display device operable to receive the illuminating light;

an optical fiber operable to direct the illuminating light from the laser light source to the display device;

wherein the optical fiber has a core extending along a central longitudinal axis and a cladding layer covering the core, the core having a refractive index profile defined from the central longitudinal axis to a longitudinal edge, the refractive index profile comprising a first refractive index at the longitudinal edge that is greater than a second refractive index at the central longitudinal axis.

14. The laser system of claim 13, wherein a radius of the core is defined between the central longitudinal axis to the longitudinal edge, the radius being between 30 to 1000 microns.

15. The laser system of claim 14, wherein the radius is between 100 to 600 microns.

16. The laser system of claim 13, wherein the cladding layer is doped and comprises a reduced cladding refractive index.

17. The laser system of claim 13, wherein the refract index profile comprises a nadir at the central longitudinal axis and a zenith at the longitudinal edge.

18. The laser system of claim 13, wherein the laser light source comprises a plurality of laser modules having different wavelength bands, each laser module comprising a plurality of sub-modules, and the optical fiber is operable to receive light from each sub-modules.

19. The laser system of claim 13, wherein the layer system further comprises a vibration device attached to the optical fiber, wherein the vibration device is operable to vibrate at a frequency greater than a threshold frequency.

20. The laser system of claim 13, wherein the display device comprises a projector.