Solid state traffic light apparatus having homogenous light source

• US 6,450,662 B1
• Filed: 09/14/2000
• Issued: 09/17/2002
• Est. Priority Date: 09/14/2000
• Status: Expired due to Term

• Current Assignee: Light Vision Systems Incorporated
• Original Assignee: General Signal Technology Corp. (SPX Corporation)
• Inventors: Hutchison, Michael C.
• Primary Examiner(s): Cariaso, Alan
• Assistant Examiner(s): Sawhney, Hargobind S.
• Application Number:
  US09/662,521
• Time in Patent Office: 733 Days
• Field of Search: 362/800, 362/235, 362/236, 362/240, 362/244, 362/246, 362/184, 362/355, 362/558, 362/238, 362/308, 362/309, 362/239, 340/815.45
• US Class Current: 362/246
• CPC Class Codes: F21S 8/00 Lighting devices intended for fixed installation F21S9/00, F21S10/00 take precedence; using a string or strip of light sources F21S4/00
• CPC Class Codes: F21W 2111/02 for roads, paths or the like
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

A solid state light apparatus generating a homogenous light beam ideally suited for use in traffic control signals. A solid state light source comprises an area array of LEDs uniformly illuminating a light diffuser to achieve the homogenous light beam. In one embodiment, a plurality of light guides direct light from each LED such that each LED illuminates the same square area of the light diffuser. In another embodiment, the LEDs are provided with lenses having a different radius of curvature such that a convex bottom surface of the light diffuser is uniformly illuminated. The LEDs proximate the center of the array have a smaller radius of curvature than the outer LEDs having flatter lenses.

Claims

1. A solid state light, comprising;

a solid state light source comprising an area array of light emmitting diodes (LEDs) generating a light output;

a light diffuser positioned over said LED array; and

a device coupled between said LED array and said light diffuser adapted to couple said light output to said light diffuser to generate a homogenous light beam.

2. The solid state light specified in claim 1 wherein said light diffuser is concave and having a convex outer surface.

3. The solid state light specified in claim 2 wherein said light source is coupled to and across said light diffuser convex outer surface.

4. The solid state light specified in claim 2 wherein said device comprises a plurality of lenses positioned over said LED array.

5. The solid state light specified in claim 4 wherein said lenses having different radii of curvature.

6. The solid state light specified in claim 5 wherein said lenses proximate a center of the LED array have a smaller radius of curvature than said lenses disposed less proximate said center of the LED array.

7. The solid state light specified in claim 4 wherein each said light diffuser portion is illuminated by said respective LED and at a substantially equal intensity.

8. The solid state light specified in claim 2 wherein said device comprises a plurality of light guides positioned between said LED array and said light diffuser.

9. The solid state light specified in claim 8 wherein one said light guide is positioned between each said respective LED and a portion of said light diffuser convex outer surface.

10. The solid state light specified in claim 9 wherein each said light guide has a geometry such that each said light diffuser portion has a substantially equal surface area.

11. The solid state light specified in claim 8 wherein said light guides have a light reflective inner surface.

12. The solid state light specified in claim 8 wherein said light guides taper outwardly from said respective LED to said light diffuser.

13. The solid state light specified in claim 8 wherein said light guides terminate closely proximate, but spaced from, said light diffuser.

14. The solid state light specified in claim 8 wherein each said light diffuser portion is illuminated by said respective LED and at a substantially equal intensity.

15. A method of generating a homogeneous light beam, comprising the steps of:

a) generating a light output using an area array of light emitting diodes (LEDs); and

b) coupling said light output to a light diffuser such that said light intensity of said light output from said light diffuser is homogeneous.

16. The method as specified in claim 15 wherein said light diffuser has a convex outer surface illuminated by said light output from said LED array.

17. The method as specified in claim 16 further comprising the step of using light guides to couple light from each said LED to a respective portion of said light diffuser convex outer surface.

18. The method as specified in claim 16 further comprising the step of disposing lenses over said LEDs, said lenses having different radii of curvature.

19. The method as specified in claim 18 wherein said lenses disposed proximate a center of said LED area array have a greater radii of curvature than said lenses disposed less proximate said center of said LED area array.

20. The method as specified in claim 17 wherein said light guides terminate closely proximate, but spaced from, said light diffuser.