Backlight assembly for improved illumination employing tapered optical elements

• US 5,598,281 A
• Filed: 11/19/1993
• Issued: 01/28/1997
• Est. Priority Date: 11/19/1993
• Status: Expired due to Term

• Current Assignee: Alliedsignal Inc. (Honeywell International Inc.)
• Original Assignee: Alliedsignal Inc. (Honeywell International Inc.)
• Inventors: Beeson, Karl W., Zimmerman, Scott M., Ferm, Paul M.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Dudek, James A.
• Application Number:
  US08/203,232
• Time in Patent Office: 1,166 Days
• Field of Search: 359/42, 359/48, 359/49, 359/40, 359/41
• US Class Current: 349/5
• CPC Class Codes: G02F 1/133524 Light-guides, e.g. fibre-optic bundles, louvered or jalousie light-guides
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members
• CPC Class Codes: G02F 1/133607 the light controlling member including light directing or refracting elements, e.g. prisms or lenses

Abstract

An improved backlight assembly comprising an array of apertures in close proximity to a light source, an array of tapered optical elements that have a light input surface area smaller than the light output surface area. Light rays pass through the apertures and are directed to the optical elements which transmit the light rays via internal reflection to provide a partially collimated light source. The light rays then pass through an array of microlenses that transmit the light rays via refraction and provide a substantially more collimated light source for the display elements of a display. The backlight assembly is advantageously used as a backlighting means for electro-optical displays, especially those designed for military and avionics applications.

Claims

1. A backlight assembly for use in an electo-optical display, said display having a modulating means capable of providing an image to a remotely positioned observer, and said backlight assembly comprising:

(a) a light generating means;

(b) an aperturing means operatively disposed in close proximity between said light generating means and said modulating means;

(c) a first collimating means disposed between said aperturing means and said modulating means, said first collimating means having a planar light input surface in close proximity to said aperture means and a planar light output surface distal from and parallel to said light input surface and larger in surface area than said light input surface, wherein said light rays transmit through said first collimating means via total internal reflection and exit from said light output surface in a substantially collimated pattern; and

(d) a second collimating means disposed between said first collimating means and said modulating means and having a light input surface that accepts said substantially collimated light rays from said first collimating means and transmits the light rays via refraction and directs said light rays towards said modulating means in a substantially more collimated pattern.

2. The backlight assembly of claim 1 wherein said first collimating means comprises an array of tapered optical elements.

3. The backlight assembly of claim 2 wherein at least one of said optical elements has a circular cross-sectional area.

4. The backlight assembly of claim 2 wherein at least one of said optical elements has a polygonal cross-sectional area.

5. The backlight assembly of claim 1 wherein said second collimating means comprises an array of microlenses.

6. The backlight assembly of claim 1 wherein said aperturing means and said first collimating means comprise an array of tapered optical elements having reflective sides.

7. A backlight assembly for use in an electro-optical display comprising

(a) a light generating means;

(b) a concentrating means having a planar light input surface in close proximity to said light generating means, a planar light output surface distal from and parallel to said light input surface and smaller in surface area than said light input surface and mirrored sidewalls wherein said light rays enter through said light input surface and travel through said concentrating means via reflection and emerge from said light output surface as a more concentrated light source; and

(c) a collimating means disposed in close proximity to said output surface and having a light input surface that accepts said concentrated light source from said concentrating means and transmits the light rays via refraction that emerge as a substantially collimated light source.

8. The backlight assembly of claim 7 wherein said concentrating means is an array of tapered optical elements.

9. The backlight assembly of claim 8 wherein at least one of said optical elements has a circular cross-sectional area.

10. The backlight assembly of claim 8 wherein at least one of said optical elements has a polygonal cross-sectional area.

11. The backlight assembly of claim 7 wherein said collimating means comprises an array of microlenses.

12. A backlight assembly for providing a substantially collimating light source comprising:

(a) a light generating means;

(b) an aperturing means operatively disposed in close proximity between said light generating means and said modulating means;

(c) an array of microcollimators disposed between said aperturing means, wherein each microcollimator comprises a planar light input surface in close proximity to said aperture means and a planar light output surface distal from and parallel to said light input surface and larger in surface area than said light input surface, wherein said light rays first transmit through said aperturing means and then through said array of microcollimators via total internal reflection and exit from said light output surface in a substantially collimated pattern; and

(d) an array of microlenses operatively disposed in close proximity to said array of microcollimators and comprising a light input surface that accepts said substantially collimated light rays from said array of microcollimators, wherein said light rays transmit through said array of microlenses via refraction and emerge as a substantially more collimated light source.

13. The backlight assembly of claim 12 wherein said microcollimators and said microlenses are constructed from organic polymeric material.

14. The backlight assembly of claim 12 wherein said microcollimators and said microlenses have an index of refraction of between about 1.45 and about 1.65.

15. A direct-view flat panel display comprising:

(a) a modulating means for modulating light to form an image visible to a remote observer;

(b) an image display means for displaying said image from said modulating means positioned adjacent to the light output surface of said modulating means, said display means comprising an array of tapered optical waveguides on a planar substrate, the tapered end of each of said waveguides extending outward from said substrate and having a light input surface adjacent said substrate and a light output surface distal from said light input surface;

(c) a backlight assembly comprising;

(i) a light generating means;

(ii) an aperturing means operatively disposed in close proximity between said light generating means and said modulating means;

(iii) an array of microcollimators disposed between said aperturing means and said modulating means, wherein each microcollimator comprises a light input surface in close proximity to said aperture means and a light output surface larger in surface area than said corresponding light input surface, wherein light rays first transmit through said aperturing means and then through said array of microcollimators via total internal reflection and exit from said microcollimator light output surface in a substantially collimated pattern; and

(iv) an array of microlenses operatively disposed in close proximity between said array of microconcentrators and said modulating means and comprising a light input surface that accepts said substantially collimated light rays from said array of microcollimators, wherein said light rays transmit through said array of microlenses via refraction and emerge as a substantially more collimated light source for said modulating means.

16. A backlight assembly for use in an electo-optical display, said display having a modulating means capable of providing an image to a remotely positioned observer, and said backlight assembly comprising:

(a) a light generating means;

(b) an aperturing means operatively disposed in close proximity between said light generating means and said modulating means;

(c) a first collimating means disposed between said aperturing means and said modulating means, said first collimating means having a light input surface in close proximity to said aperture means and a light output surface larger in surface area than said light input surface, wherein said light rays transmit through said first collimating means via total internal reflection and exit from said light output surface in a substantially collimated pattern; and

(d) a second collimating means disposed between said first collimating means and said modulating means and having a light input surface that accepts said substantially collimated light rays from said first collimating means and transmits the light rays via refraction and directs said light rays towards said modulating means in a substantially more collimated pattern.

17. A backlight assembly for use in an electo-optical display, said display having a modulating means capable of providing an image to a remotely positioned observer, and said backlight assembly comprising:

(a) a light generating means;

(b) an aperturing means operatively disposed in close proximity between said light generating means and said modulating means;

(c) a first collimating means comprising a planar slab of transparent material disposed between said aperturing means and said modulating means, wherein said light rays transmit through said first collimating means via total internal reflection and exit from said light output surface in a substantially collimated pattern; and

(d) a second collimating means disposed between said first collimating means and said modulating means and having a light input surface that accepts said substantially collimated light rays from said first collimating means and transmits the light rays via refraction and directs said light rays towards said modulating means in a substantially more collimated pattern.