Illumination system employing an array of microprisms

• US 5,555,109 A
• Filed: 02/24/1995
• Issued: 09/10/1996
• Est. Priority Date: 11/05/1993
• Status: Expired due to Term

• Current Assignee: Advanced Display Technologies of Texas LLC (Advanced Display Technologies)
• Original Assignee: Alliedsignal Inc. (Honeywell International Inc.)
• Inventors: Zimmerman, Scott M., Beeson, Karl W., Hou, Janpu, Schweyen, John C.
• Primary Examiner(s): Fahmy, Wael M.
• Assistant Examiner(s): Abraham, Fetsum
• Application Number:
  US08/394,098
• Time in Patent Office: 564 Days
• Field of Search: 359/42, 359/48, 359/49, 359/69, 362/26, 362/27, 362/39
• US Class Current: 349/57
• CPC Class Codes: F21V 5/02 of prismatic shape F21V5/04 takes precedence
• CPC Class Codes: F21Y 2103/00 Elongate light sources, e.g. fluorescent tubes
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer

Abstract

An optical illumination system comprising a waveguide that accepts light generated by a diffuse light source and transmits the light via total internal reflection. Attached on one face of the waveguide is an array of microprisms, with each microprism having an light input surface parallel to a light output surface and at least two sidewalls tilted at an angle from the direction normal to the surface of the waveguide such that light escapes from the waveguide, reflects off the tilted sidewalls and emerges from the microprism as a spatially directed light source. An array of microlenses may be positioned to accept the output of the microprisms so that the light exiting from the microlenses is a substantially collimated light source. The optical illumination system is advantageous for any application that requires a non diffuse or substantially collimated that is both energy efficient and contained in a low profile assembly.

Claims

1. An illumination assembly for providing a spatially directed light source comprising:

(a) a light transmitting means having a first light accepting surface in close proximity to a first diffuse light source, wherein said light transmitting means transports light emanating from said first diffuse light source;

(b) reflecting means for redirecting said light comprising an array of microprisms wherein each microprism comprises;

(i) a light input surface attached to said light transmitting means;

(ii) a light output surface distal from and parallel to said light input surface and having a surface area at least equal to the surface area of said light input surface;

(iii) a first pair of oppositely disposed sidewalls disposed between and continuous with said light input surface and said light output surface and intersecting said light transmitting means wherein the lines of intersection are substantially parallel to said first light accepting surface and at least one of said sidewalls forms a first tilt angle with respect to the normal of the surface of said light transmitting means;

(iv) a second pair of oppositely disposed tilted sidewalls, disposed between and continuous with said light input surface and said light output surface and intersecting said light transmitting means wherein said lines of intersection are substantially perpendicular to said first light accepting surface and at least one of said sidewalls forms a second tilt angle with respect to the normal of the surface of said light transmitting means;

wherein, said light reflecting through said light transmitting means enters said microprisms through said light input surfaces, is redirected by said sidewalls and emerges through said light output surfaces as a spatially directed light source.

2. An illumination assembly comprising:

(a) a light transmitting means for accepting light from a light source and causing light to transmit therethrough;

(b) an array of microprisms wherein each 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 with each having an edge defined by said light 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 with each having an edge defined by said light 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.

3. The illumination assembly of claim 2 wherein said light transmitting means is a waveguide.

4. The illumination assembly of claim 2 to further comprising an array of microlenses, wherein the light output of each microprism is directed to at least one corresponding microlens.

5. The illumination assembly of claim 4 wherein said microprisms and microlenses are constructed from organic polymeric material.

6. The illumination assembly of claim 4 wherein said array of microprisms and array of microlenses are integrally formed.

7. The illumination assembly of claim 4 wherein said microprisms, microlenses, and light transmitting means have an index of refraction of between about 1.45 and about 1.65.

8. An illumination assembly comprising:

(a) a light transmitting means having a first light accepting surface in close proximity to a first light source, wherein said light transmitting means transports light emanating from said first light source;

(b) an array of microprisms wherein each 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 light output surface having a surface area greater than the surface area of said light input surface;

(iii) a first pair of sidewalls disposed between and contiguous with said light input surface and said light output surface and at least one of said sidewalls forms a first tilt angle to the normal of the surface of said light transmitting means;

(iv) a second pair of sidewalls, disposed between and contiguous with said light input surface and said light output surface and at least one of said sidewalls forms a second tilt angle to the normal of the surface of said light transmitting means;

wherein, said light reflecting through said light transmitting means enters said microprisms through said light input surfaces, is redirected by said sidewalls and emerges through said light output surfaces as a spatially directed light source.

9. The illumination assembly of claim 8 wherein said reflecting means further comprises an array of microlenses, wherein the light output of each microprism is directed to at least one corresponding microlens.

10. The illumination assembly of claim 9 wherein said microprisms, microlenses, and light transmitting means have an index of refraction of between about 1.40 and about 1.65.

11. The illumination assembly of claim 9 herein said array of microprisms and array of microlenses are integrally formed.

12. The illumination assembly of claim 8 wherein said first tilt angle is between 15 to 50 degrees to the normal of the surface of said light transmitting means.

13. The illumination assembly of claim 8 wherein second tilt angle is between 0 to 25 degrees to the normal of the surface of said light transmitting means.

14. The illumination assembly of claim 8 wherein said light transmitting means further comprises a second light accepting surface in close proximity to a second light source, wherein said light transmitting means transports light emanating from said second light source.

15. The illumination assembly of claim 14 wherein said first light accepting surface is oppositely disposed from said second light accepting surface.

16. The illumination assembly of claim 8 wherein said output surface is parallel to said input surface.

17. An illumination assembly comprising:

(a) a light transmitting means;

(b) an array of microprisms wherein each microprism comprises;

(i) a light input surface optically coupled to said light transmitting means;

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

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

(c) an array of microlenses integrally formed with said array of microlenses wherein a portion of light reflecting through said light transmitting means enters each microprisms through said light input surfaces, and is redirected by said sidewalls through said microprisms.

18. The illumination assembly of claim 17 wherein said microprisms and microlenses are formed from organic polymeric material having an index of refraction of between about 1.40 and 1.65.

19. The illumination assembly of claim 17 wherein said first pair of sidewalls forms a tilt angle of between 15 to 50 degrees to the normal of said light transmitting means.

20. The illumination assembly of claim 17 wherein said second pair of sidewalls forms a tilt angle of between 0 to 25 degrees to the normal of said light transmitting means.