# US 8,786,940 B2 · Despeckling apparatus and method

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 8,786,940 B2
- Document ID: US8786940B2
- Status: Granted
- Kind: B2
- Application number: 12/962,185
- Filed: 2010-12-07
- Published: 2011-06-09
- Granted: 2014-07-22
- Earliest claimed: 2009-12-07
- Assignees: Laser Light Engines, Inc.
- Applicants: Barret Lippey; William Beck; Ian Turner
- Inventors: Barret Lippey; William Beck; Ian Turner
- Web page: https://patentgrep.com/patent/US8786940B2

## CPC

- G02F 1/35: Non-linear optics
- G02B 27/48: Laser speckle optics
- G02F 1/37: for second-harmonic generation {(G02F1/3532 takes precedence)}
- H01S 3/2383: {Parallel arrangements}
- H01S 3/30: using scattering effects, e.g. stimulated Brillouin or Raman effects
- H01S 3/302: {in an optical fibre}
- H04N 9/3161: {using laser light sources (using laser beams scanning the display screen H04N9/3129)}
- 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)}
- H01S 2301/02: ASE (amplified spontaneous emission), noise; Reduction thereof
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

An apparatus and method that reduces laser speckle by using stimulated Raman scattering in an optical fiber. The fiber core diameter and length are selected to achieve a desired output color. An adjustable despeckler is formed by combining two optical fibers in parallel and adjusting the amount of light in each path.

## Claims

### Claim 1

An optical apparatus comprising:
an optical fiber; and
a red light source;
wherein a stimulated Raman scattering in the optical fiber reduces a speckle characteristic of a light output from the optical fiber, a core diameter and a length of the optical fiber are selected to achieve a desired color of the light output, the desired color of the light output is a primary color, the primary color is a green color, a portion of the stimulated Raman scattering forms a red stimulated Raman scattering light, and the red light source is combined with the red stimulated Raman scattering light.

### Claim 2

An optical apparatus comprising:
a first optical fiber;
wherein a stimulated Raman scattering in the first optical fiber reduces a first speckle characteristic of a first light output from the first optical fiber;
a second optical fiber; and
a variable light splitter;
wherein the variable light splitter illuminates the first optical fiber and the second optical fiber, and a stimulated Raman scattering in the second optical fiber reduces a second speckle characteristic of a second light output from the second optical fiber.

### Claim 3 (depends on 2)

The apparatus of claim 2 wherein the variable light splitter comprises:
a rotating waveplate; and
a polarizing beam splitter.

### Claim 4 (depends on 2)

The apparatus of claim 2 wherein the second optical fiber has a second core diameter and a second length and the second core diameter and the second length are selected to achieve a second desired amount of reduction in the second speckle characteristic.

### Claim 5 (depends on 2)

The apparatus of claim 2 further comprising:
a laser light source; and
a digital projector;
wherein the laser light source illuminates the variable light splitter, and the first optical fiber and the second optical fiber illuminate the digital projector.

### Claim 6 (depends on 2)

The apparatus of claim 2 wherein the variable light splitter is adjusted to achieve a desired color for a combined light output of the first optical fiber and the second optical fiber.

### Claim 7

A method of despeckling comprising:
generating a first laser beam;
splitting the first laser beam into second and third laser beams;
focusing the second laser beam into a first optical fiber;
generating a first stimulated Raman scattering light in the first optical fiber;
focusing the third laser beam into a second optical fiber;
generating a second stimulated Raman scattering light in the second optical fiber;
combining the first stimulated Raman scattering light and the second stimulated Raman scattering light to form a combined stimulated Raman scattering light;
using the combined stimulated Raman scattering light to form a projected digital image; and
adjusting the amount of light in the second laser beam and the third laser beam to achieve a desired color for a primary color in the projected digital image.