Color separating backlight

• US 5,748,828 A
• Filed: 01/13/1997
• Issued: 05/05/1998
• Est. Priority Date: 11/10/1993
• Status: Expired due to Term

• Current Assignee: Alliedsignal Inc.
• Original Assignee: Alliedsignal Inc.
• Inventors: Steiner, Ivan B., Zimmerman, Scott M., Beeson, Karl W.
• Primary Examiner(s): Ullah, Akm E.
• Application Number:
  US08/782,133
• Time in Patent Office: 477 Days
• Field of Search: 385/31, 385/36, 385/146, 385/147, 385/901, 359/34, 359/291, 359/454, 359/292, 349/62-65, 362/32
• US Class Current: 385/146
• CPC Class Codes: F21Y 2103/00 Elongate light sources, e.g. fluorescent tubes
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02F 1/133621 providing coloured light G02F1/133617, G02F1/133533 take precedence

Abstract

A backlight for use in a flat panel display backlight consists of three components, (1) a collimating means, optically coupled to a waveguide suitable for transmitting light, which collimates white light and directs the light at an angle to the normal (perpendicular) direction to the surface of the flat panel display, (2) diffraction means that extend across the entire display between the collimating means and the flat panel, which angularly separates the white light into red, green and blue components, and (3) light directing means, also extending across the entire display between the diffraction means and the flat panel display, for focusing the red, green and blue light components onto the individual red, green and blue color subpixels of the LCD in an aligned fashion.

Claims

1. A backlight assembly for use in a flat panel electronic display, said display having a modulating means capable of providing an image to a remotely positioned observer, said backlight assembly comprising means for transmitting light and having a generally planar first surface;

a reflecting means having at least one input surface optically coupled to said first surface for receiving a portion of light from said light transmitting means and for reflecting a portion of light so as to produce a collimated light output at a desired output angle;

a diffraction means disposed between said reflecting means and said modulating means for accepting said collimated light and separating said light into at least one of red, blue and green light components and;

light directing means for spatially directing said light components.

2. The backlight assembly of claim 1 wherein said light directing means spatially directs said light components to corresponding subpixels of said light modulating means.

3. The backlight assembly of claim 1 wherein said reflecting means comprises an array of microprisms wherein each microprism comprises:

(a) an input surface optically coupled to said light transmitting means for receiving a portion of light transmitting through said light transmitting means;

(b) a sidewall having an edge defined by said light input surface and further positioned for (i) effecting total internal reflection of a portion of light received by said light input surface; and

(ii) directing said reflected light as a substantially collimated output from said microprism.

4. The backlight assembly of claim 3 wherein said reflecting means further comprises a convex output surface.

5. The backlight assembly of claim 1 wherein said diffraction means being selected from the group consisting of a surface relief hologram, a volume hologram, a grooved diffraction grating, an array of prisms, and a computer generated holographic optical element.

6. The backlight assembly of claim 1 wherein said light directing means being selected from the group consisting of an array of plano convex micro lenses, an array of biconvex microlenses, an array of graded refractive index lenses or a computer generated holographic optical element.

7. An illumination assembly comprising light transmitting means;

a reflecting means having at least one input surface optically coupled to said first surface for receiving a portion of light from said light transmitting means and for reflecting a portion of light so as to produce a collimated light output at a desired output angle;

a diffraction means for accepting said collimated light and separating said light into at least one of red, blue and green light components and;

light directing means for spatially directing said light components.

8. A illumination assembly comprising:

(a) a light transmitting means having means for accepting light;

(b) an array of microprisms wherein at least one microprism comprises;

(i) an input surface optically coupled to said light transmitting means for receiving a portion of light transmitting through said light transmitting means;

(ii) a sidewall having an edge defined by said light input surface and positioned for effecting total internal reflection of a portion of light received by said light input surface;

(c) diffracting means positioned to accept light reflecting off said sidewall and for separating light into at least a red, blue or green component; and

(d) light directing means for spatially directing at least one of said light components.

9. The illumination assembly of claim 8 wherein said microprism further comprises a convex output surface.

10. An illumination assembly comprising:

(a) a light transmitting means;

(b) an array of microprisms wherein at least one microprism comprises;

(i) a light input surface optically coupled to said light transmitting means for receiving a portion of light transmitting through said light transmitting means;

(ii) a first pair of sidewalls each having a common edge with said input surface and at least one of said sidewalls is positioned for effecting total internal reflection of a portion of light received by said light input surface;

(iii) a second pair of sidewalls each having a common edge with said input surface and at least one of said sidewalls is positioned for effecting total internal reflection of a portion of light received by said light input surface;

(c) diffracting means positioned to accept light reflecting off said sidewall for separating light into at least a red, blue or green component; and

(d) light directing means for spatially directing at least one of said light components.

11. The illumination assembly of claim 10 wherein said microprism further comprises a convex output surface.