Laser projection system

• US 7,775,670 B2
• Filed: 08/25/2005
• Issued: 08/17/2010
• Est. Priority Date: 08/30/2004
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Sanders, Renatus Hendricus Maria, Weekamp, Johannus Wilhelmus
• Primary Examiner(s): Epps; Georgia Y
• Assistant Examiner(s): Chowdhury; Sultan
• Application Number:
  US11/573,915
• Publication Number:
  US 20080278692A1
• Time in Patent Office: 1,818 Days
• Field of Search: 359/205, 359/577, 359/620, 359/667, 359/900, 359/259, 359/665, 359/666, 372/22, 372/99, 372/103, 353/98, 353/100, 353/122
• US Class Current: 353/122
• CPC Class Codes: G02B 26/005 based on electrowetting
• CPC Class Codes: G02B 26/06 for controlling the phase of light G02B26/08 takes precedence , measuring optical phase difference G01J9/00
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: G02B 3/14 of variable focal length
• CPC Class Codes: G03F 7/70583 Speckle reduction, e.g. coherence control or amplitude/wavefront splitting
• CPC Class Codes: H04N 5/74 Projection arrangements for image reproduction, e.g. using eidophor
• 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

The present invention relates to a laser projection system (1) having means for reducing the coherence of a generated laser beam (3) in order to reduce the occurrence of annoying speckle artifacts in images produced by the system. Coherence is reduced by letting the laser beam (3) pass through a transparent cell (6) comprising first (A) and second (B) immiscible fluids having different refractive indices. The fluids are displaced in the cell, preferably using an electrowetting technique. The cell (6) may thus be realized as an electrowetting lens, which is driven with a pseudo random driving signal.

Claims

1. A laser projection system comprising:

a laser light source for generating a laser beam;

means for projecting the laser beam onto a surface; and

speckle reduction means for reducing speckle artifacts appearing on the surface due to incidence of the laser beam, wherein said speckle reduction means comprises;

a transparent cell arranged in a path of the laser beam, said transparent cell comprising first and second immiscible fluids having different refractive indices; and

control means coupled to said transparent cell for controlling positions of the first and second immiscible fluids in the cell in order to vary an optical path length of the laser beam when propagating through the cell.

2. The laser projection system as claimed in claim 1, wherein the control means controls the positions of the first and second immiscible fluids based on an electrowetting effect.

3. The laser projection system as claimed in claim 2, wherein the speckle reduction means comprises an electrowetting lens.

4. The laser projection system as claimed in claim 3, wherein the electrowetting lens is provided with a pseudo random control signal.

5. The laser projection system as claimed in claim 1, wherein said control means varies the optical path length more than •

/4, where •

is the wavelength of the laser beam produced by the light source.