METHOD AND DEVICE FOR SPECKLE REDUCTION

• US 20100110364A1
• Filed: 11/06/2007
• Published: 05/06/2010
• Est. Priority Date: 11/07/2006
• Status: Abandoned Application

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Teunissen, Hein Johannes, Wang, Lingli
• Application Number:
  US12/513,395
• Publication Number:
  US 20100110364A1
• Time in Patent Office: Days
• US Class Current: 349/201
• CPC Class Codes: G02B 27/48 Laser speckle optics
• 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 device and method for speckle reduction are disclosed, wherein a coherent laser beam (3) is expanded by using a beam expander (7). The expanded beam is subsequently allowed to pass through a variable optical element (11), which may comprise a liquid crystal cell, and applies a diffractive function on the expanded beam. The cross-section of the beam is then reduced by means of a collimator (17). The speckle pattern of the collimated beam is varied quickly, such that the extent of annoying speckle, which is perceived when the beam is projected on a surface, is reduced.

Claims

1. Device for reducing speckle produced by a laser beam, the device comprising:

a beam expander, arranged to produce an expanded beam (9) from an incident beam (3), the expanded beam having an increased cross-section area as compared to the incident beam;

a variable optical element comprising at least one liquid crystal cell containing a liquid crystal material and having a grating structure and electrodes to influence the contained liquid crystal material, wherein the optical element is arranged in the path of the expanded beam to apply a diffractive function on at least a sub-portion of the expanded beam, thereby producing a diffracted beam (15), wherein the diffractive function varies over time; and

a beam collimator arranged to produce a collimated (19) beam from the diffracted beam (15), the collimated beam having a decreased cross-section area as compared to the diffracted beam.

5. Device according to claim 1, wherein the optical element (11′

) comprises a liquid crystal cell, containing a liquid crystal material and having a grating structure and a plurality of electrodes interconnected in groups to influence the contained liquid crystal material.

6. Device according to claim 1, wherein the optical element (11″

) comprises a plurality of liquid crystal cells (81, 83, 85, 87, 89), each cell containing a liquid crystal material and having a grating structure and electrodes to influence the contained liquid crystal material, wherein each cell affects a sub-portion of the expanded beam.

2. (canceled)

3. Device according to claim 2, wherein the optical element (11) further comprises a second liquid crystal cell (35), containing a liquid crystal material (37) and having a grating structure (39) and electrodes (41, 43) to influence the contained liquid crystal material, wherein the first and second cells are individually controllable.

4. Device according to claim 3, wherein the grating periods and/or the grating orientations of the first and second cells are mutually different.

7-8. -8. (canceled)

9. Method for reducing experienced speckle produced by a laser beam, the method comprising:

producing an expanded beam from an incident beam, the expanded beam having an increased cross-section area as compared to the incident beam;

applying a diffractive function, using a variable optical element comprising at least one liquid crystal cell, on at least a sub-portion of the expanded beam, thereby producing a diffracted beam, wherein the diffractive function varies over time; and

producing a collimated beam from the diffracted beam, the collimated beam having a decreased cross-section area as compared to the diffracted beam.