Speckle suppressed laser projection system using RF injection

• US 6,600,590 B2
• Filed: 02/20/2001
• Issued: 07/29/2003
• 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): Mack, Ricky
• Application Number:
  US09/788,862
• Publication Number:
  US 20020154375A1
• Time in Patent Office: 889 Days
• Field of Search: 359/238, 359/278, 359/285, 359/287, 359/305, 359/312, 359/327, 359/328, 372/13, 372/23, 372/28
• US Class Current: 359/287
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: H01S 5/06213 Amplitude modulation
• CPC Class Codes: H01S 5/06226 Modulation at ultra-high frequencies
• CPC Class Codes: H04N 5/74 Projection arrangements for image reproduction, e.g. using eidophor
• CPC Class Codes: H04N 5/7425 the modulator being a dielectric deformable layer controlled by an electron beam, e.g. eidophor projector
• CPC Class Codes: H04N 9/3105 for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators simultaneous projection in colour photography G03B33/10; beam splitting or combining systems per se G02B27/10
• 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
• CPC Class Codes: H04N 9/3161 using laser light sources using laser beams scanning the display screen H04N9/3129

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. Since the eye is very sensitive to horizontal and vertical edges, but less sensitive to angles in between, beam movement of approximately 45 degrees may minimize the loss of MTF in the horizontal and vertical directions.

Claims

1. A speckle suppressed laser projection system comprising:

a radio frequency oscillator;

a semiconductor laser;

wherein said frequency oscillator injects said laser with a radio frequency signal to produce a multi-wavelength output; and

an optical projection system.

2. A speckle suppressed laser projection system as in claim 1 wherein said laser has an internal photodiode which senses power output.

3. A speckle suppressed laser projection system as in claim 2 wherein a power control circuit monitors said internal photodiode and adjusts a DC bias drive signal for said laser.

4. A speckle suppressed laser projection system as in claim 1 wherein said system is a motion picture projection system.

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

generating a radio frequency signal;

injecting said radio frequency signal into a semiconductor laser to produce a multi-wavelength output beam;

directing said multi-wavelength output beam of said laser through an optical projection system; and

projecting said multi-wavelength output beam onto a projection surface to form an image.

6. A method for speckle suppressed laser projection system as in claim 5 wherein said laser has an internal photodiode which senses power output.

7. A method for speckle suppressed laser projection system as in claim 5 wherein a power control circuit monitors said internal photodiode and adjusts a DC bias drive signal for said laser.

8. A method for speckle suppressed laser projection system as in claim 5 wherein said system is a motion picture projection system.

9. A method of speckle reduction in a laser projection system comprising the steps of:

generating a radio frequency signal;

injecting said radio frequency signal into a laser to produce a multimode output beam;

directing said multimode output beam of said laser through an optical projection system; and

projecting said multimode output beam onto a projection surface to form an image.