Speckle suppressed laser projection system with partial beam reflection

• US 6,625,381 B2
• Filed: 02/20/2001
• Issued: 09/23/2003
• Est. Priority Date: 02/20/2001
• Status: Expired due to Term

• Current Assignee: IMAX Corporation
• Original Assignee: Eastman Kodak Company
• Inventors: Roddy, James E., Markis, William R.
• Primary Examiner(s): Dang, Hung Xuan
• Assistant Examiner(s): Tra, Tuyen
• Application Number:
  US09/788,866
• Publication Number:
  US 20020126981A1
• Time in Patent Office: 945 Days
• Field of Search: 385/907, 385/115, 385/116, 385/120, 385/88, 385/147, 372/6, 372/29.011, 372/38.1, 372/23, 372/19
• US Class Current: 385/147
• CPC Class Codes: G02B 26/101 with both horizontal and vertical deflecting means, e.g. raster or XY scanners colour television using laser beams scanning a display screen H04N9/3129
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: G02B 6/42 Coupling light guides with opto-electronic elements
• CPC Class Codes: H01S 5/06209 in single-section lasers H01S5/0608 takes precedence
• CPC Class Codes: H01S 5/06213 Amplitude modulation
• CPC Class Codes: H01S 5/0652 Coherence lowering or collapse, e.g. multimode emission by additional input or modulation
• CPC Class Codes: H04N 9/3129 scanning a light beam on the display screen scanning a light beam on a screen in displays other than projection devices G09G3/02; scanning systems in general G02B26/10; projectors using laser light sources in general H04N9/3161

Abstract

A system and method for reducing or eliminating the speckle intensity distribution of a laser imaging system. In one embodiment of the invention, a radio frequency signal is injected into a semiconductor laser light source (12) for a projection system (10) to create different speckle patterns that blend together on a projection surface (19). In another embodiment of the invention, optical feedback is used to induce a laser light source for a projection system (10) to create different speckle patterns that blend together on a projection surface (19). In another embodiment of the invention, the laser light source wavelength is Doppler shifted to produce different speckle patterns. In another embodiment of the invention, a means of deflection is used to directionally move the beam to reduce noticeable speckle.

Claims

1. A speckle suppressed laser projection system comprising:

a constant current supply;

a semiconductor laser;

an optical fiber positioned in front of an output of said laser, wherein said fiber induces optical feedback in said laser which causes said laser to produce a multimode output beam; and

an optical projection system, wherein said optical projection system projects said multimode beam on a screen.

2. A speckle suppressed laser projection system as in claim 1 wherein a thermoelectric cooler maintains the temperature of said laser and said fiber.

3. A speckle suppressed laser projection system as in claim 2 wherein a temperature controller controls said thermoelectric cooler.

4. A speckle suppressed laser projection system as in claim 1 wherein image data is supplied to said optical projection system.

5. A speckle suppressed laser projection system comprising:

a laser which projects a beam;

a partially reflecting mirror located in front of said laser and which partially reflects a portion of said beam back to said laser which cause said laser to generate a multimode beam;

wherein a portion of said multimode beam is transmitted through said partially reflecting mirror; and

an optical projection system which projects said multimode beam onto a screen.

6. A speckle suppressed laser projection system as in claim 5 wherein image data is supplied to said projection system.

7. A method of speckle reduction, the method comprising the steps of:

placing an optical fiber in front of the output window of a semiconductor laser;

inducing optical feedback in said laser, wherein the output of said laser is a multimode beam;

directing said multimode beam into an optical projection system;

projecting said multimode beam onto a projection surface, wherein the multimode beam has different speckle patterns that blend together.

8. A method of speckle reduction, the method comprising the steps of:

placing a partially reflecting mirror in front of the output window of a laser;

reflecting part of the output beam of said laser with said partially reflecting mirror back into said laser;

inducing optical feedback in said laser, wherein the output of said laser is a multimode beam;

directing said multimode beam towards an optical projection system; and

projecting said multimode beam onto a projection surface, wherein the multimode beam has different speckle patterns that blend together.