DIFFUSER HAVING SHAPE PROFILE FOR REDUCING SPECKLE NOISE AND A LASER PROJECTION SYSTEM EMPLOYING THE SAME

• US 20080129891A1
• Filed: 08/20/2007
• Published: 06/05/2008
• Est. Priority Date: 12/01/2006
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd. (Samsung Group)
• Original Assignee: Samsung Electronics Co. Ltd. (Samsung Group)
• Inventors: Prudnikov, Oleg
• Granted Patent: US 8,240,855 B2
• Time in Patent Office: Days
• US Class Current: 348/744
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: G02B 3/0006 Arrays G02B3/02, G02B5/188 take precedence
• CPC Class Codes: G02B 3/005 arranged along a single direction only, e.g. lenticular sheets G02B3/0043 takes precedence
• CPC Class Codes: G02B 5/0215 the surface having a regular structure
• CPC Class Codes: G02B 5/0278 used in transmission
• CPC Class Codes: G03B 11/00 Filters or other obturators specially adapted for photographic purposes
• CPC Class Codes: G03B 21/005 Projectors using an electronic spatial light modulator but not peculiar thereto
• 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 diffuser having a shape for reducing speckle noise and a laser projection system including the diffuser are provided. The diffuser is employed by a laser projection system to reduce speckle noise, and includes a scattering pattern. The scattering pattern includes a plurality of scattering ribbons, and a curved surface of each of the plurality of scattering ribbons satisfies equations so that speckle noise is minimized for an aperture size of an optical system.

Claims

1. A diffuser employed in a laser projection system for reducing speckle noise, the diffuser comprising a scattering pattern,

wherein the scattering pattern comprises a plurality of scattering ribbons arranged in a direction of a first axis and extending in a direction parallel to a second axis, and

each of the plurality of scattering ribbons comprises a second surface, wherein a height of the second surface with respect to a first surface defined by the first axis and the second axis varies based on a measuring point on the first axis, and the second surface satisfies the Equations

$\frac{}{}$



x 

h 

( x ) = - tan 

( β



( x ) ) $\mathrm{\beta <br><br>}<br><br>\left(x\right)=\mathrm{\alpha <br><br>}<br><br><br><br>x,$

where h(x) is a height of the second surface with respect to the first surface measured from a point x of the first axis if a point on the first surface corresponding to an apex of the second surface is an origin, β

(x) is an angle between a line tangent to the second surface and the first axis, and α

is a constant.

3. The diffuser of claim 1, wherein α

is greater than 0, and each of the scattering ribbons has a convex shape.

4. The diffuser of claim 1, wherein α

is less than 0, and each of the scattering ribbons has a concave shape.

5. The diffuser of claim 1, wherein the diffuser is formed of a light transmissive material.

6. The diffuser of claim 1, wherein the second surface of each of the plurality of scattering ribbons comprises a reflective surface.

2. A diffuser employed in a laser projection system for reducing speckle noise, the diffuser comprising a scattering pattern,

wherein the scattering pattern comprises a plurality of scattering ribbons arranged in a direction of a first axis and extending in a direction parallel to a second axis, and

each of the plurality of scattering ribbons comprises a second surface, wherein a height of the second surface with respect to a first surface defined by the first axis and the second axis varies based on a measuring point on the first axis, and the second surface satisfies the Equation

$h$

( x ) = h 0 - α





x 2 2 ,

where h(x) is a height of the second surface with respect to the first surface measured from a point x of the first axis if a point on the first surface corresponding to an apex of the second surface is an origin, h₀ is a height of an apex of the second surface, and α

is a constant.

7. A laser projection system comprising:

a laser light source,

an optical modulator which modulates light generated from the light source corresponding to image information,

a projection lens unit which projects modulated light on a screen, and

a diffuser disposed on an optical path facing the screen,

wherein the diffuser oscillates with respect to an optical axis and comprising a scattering pattern,

and the scattering pattern has an optimized shape profile to minimize speckle noise with respect to an aperture of the laser projection system.

8. The laser projection system of claim 7, wherein the scattering pattern comprises a plurality of scattering ribbons arranged in a direction of a first axis and extending in a direction parallel to a second axis, each of the plurality of scattering ribbons comprises a second surface, and

a height of the second surface with respect to a first surface defined by the first axis and the second axis varies based on a measuring point on the first axis.

9. The laser projection system of claim 8, wherein the second surface satisfies the Equations

$\frac{}{}$



x 

h 

( x ) = - tan 

( β



( x ) ) $\mathrm{\beta <br><br>}<br><br>\left(x\right)=\mathrm{\alpha <br><br>}<br><br><br><br>x,$

where h(x) is a height of the second surface with respect to the first surface measured from a point x of the first axis if a point on the first surface corresponding to an apex of the second surface is an origin, β

(x) is an angle between a line tangent to the second surface and the first axis, and a is a constant.

10. The laser projection system of claim 8, wherein the second surface satisfies the Equation

$h$

( x ) = h 0 - α





x 2 2

where h(x) is a height of the second surface with respect to the first surface measured from a point x of the first axis if a point on the first surface corresponding to an apex of the second surface is an origin, h₀ is the height of an apex of the second surface, and α

is a constant.

11. The laser projection system of claim 9, wherein α

is greater than 0, and each of the scattering ribbons has a convex shape.

12. The laser projection system of claim 9, wherein α

is smaller than 0, and each of the scattering ribbons has a concave shape.

13. The laser projection system of claim 7, wherein the optical modulator comprises a line type light modulation device, and

the laser projection system further comprises a scanning unit which is formed on a optical path between the projection lens unit and the screen, and is driven so that a line panel formed by the optical modulator is scanned in a direction perpendicular to a line direction of the line panel.

14. The laser projection system of claim 13, wherein the diffuser is formed of a light transmissive material.

15. The laser projection system of claim 14, wherein the optical modulator generates and irradiates light of the line panel towards an opposite surface to a surface on which the scattering pattern is formed.

16. The laser projection system of claim 13, wherein a surface on which the scattering pattern is formed comprises a reflective surface.

17. The laser projection system of claim 16, wherein the optical modulator generates and irradiates light of the line panel towards the surface on which the scattering pattern is formed.

18. The laser projection system of claim 17, further comprising:

an optical path conversion member formed on an optical path between the optical modulator and the diffuser, wherein the optical path conversion member converts the light of the line panel so the light proceeds towards the surface on which the scattering pattern is formed.

19. The laser projection system of claim 13, wherein an oscillating direction of the diffuser is perpendicular to a direction along which the scanning unit scans the line panel.