LED collimation optics with improved performance and reduced size

• US 20020080615A1
• Filed: 12/22/2000
• Published: 06/27/2002
• Est. Priority Date: 12/22/2000
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Marshall, Thomas, Pashley, Michael
• Granted Patent: US 6,547,423 B2
• Time in Patent Office: Days
• US Class Current: 362/333
• CPC Class Codes: F21V 5/04 of lens shape
• CPC Class Codes: F21V 7/0091 using total internal reflection
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: G02B 3/00 Simple or compound lenses
• CPC Class Codes: G02B 6/4206 Optical features G02B6/4207, G02B6/421 take precedence
• CPC Class Codes: H01L 33/54 having a particular shape
• CPC Class Codes: H01L 33/58 Optical field-shaping elements
• CPC Class Codes: H01L 33/60 Reflective elements

Abstract

An LED module that includes an LED (light-emitting diode) and a rotationally symmetrical, bowl-shaped collimator lens is provided. The collimator lens has an inner refractive wall, an outer reflective wall, a first surface having an entrance aperture with a recess in which the LED is situated and which collimator lens is also provided with a second surface from which light generated by the LED emerges, the normal to the surface extending substantially parallel to the axis of symmetry of the lens, and the LED module also includes one or more of the following structures: (1) a conic wall portion of the recess of the inner refractive wall at the entrance aperture that includes a curved portion, and an outer reflective wall so configured in accordance with the structure of the inner refractive wall to achieve substantial collimation of a source of light at the entrance aperture; and/or (2) a first surface of the lens that is recessed away from the LED source; and/or (3) two surfaces of said refractive wall between which the refractive function of said refractive wall is divided. The LED module offers an improvement in the performance of the Flat top Tulip Collimator disclosed and claimed in our co-pending application Ser. No. 09/415,833 in terms of reduced size, beam divergence, beam uniformity, and to some degree efficiency. Moreover, it allows a wider variety of choices in optimizing various performance characteristics, and this in turn allows more flexibility in the structure design.

Claims

1. An LED module comprising an LED (light-emitting diode) and a rotationally symmetrical, bowl-shaped collimator lens which comprises an inner refractive wall, an outer reflective wall, a first surface having an entrance aperture with a recess in which the LED is situated and which collimator lens is also provided with a second surface from which light generated by the LED emerges,

wherein the LED module also includes one or more of the following structures

(1) a conic wall portion of the recess of the inner refractive wall at the entrance aperture that includes a curved portion, and an outer reflective wall so configured in accordance with the structure of said inner refractive wall to achieve substantial collimation of a source of light at the entrance aperture;

(2) a first surface of the lens that is recessed away from the LED source

(3) two surfaces of said refractive wall between which the refractive function of the lens is divided.

2. An LED module as claimed in claim 1, wherein said conic wall portion of the recess of the inner refractive wall at the entrance aperture includes a curved portion and said portion of the inner refractive wall is at a first angle from the optic axis that is larger than a second angle from the optic axis of a comparable portion of a refractive wall in a Reference Collimator.

3. An LED module as claimed in claim 1, wherein said curved portion is achieved by providing a structure wherein a slope angle of a tangent to said portion of the inner refractive wall at an angle of 90°

to the optic axis is farther away from the vertical than is the comparable portion of the refractive wall in a Reference Collimator.

4. An LED module as claimed in claim 3, wherein the inner refractive wall of the recess near the entrance aperture has a curved portion that is inclined to the vertical at an angle substantially greater than is the comparable slope angle of the tangent in a Reference Collimator.

5. An LED module as claimed in claim 1, wherein the lens is divided between a first surface and a second surface.

6. An LED module as claimed in claim 5, wherein said first surface is that portion of a bounding surface of the recess that lies within a cone of a cone angle lens θ

about the optic axis with vertex at the LED center.

7. An LED module as claimed in claim 6, wherein the second surface is a planar top surface.

8. An LED module as claimed in claim 6, wherein the second surface is a curved top surface.

9. An LED module as claimed in claim 6, wherein the first surface and the second surface is a curved surface.

10. An LED module as claimed in claim 7, which comprises a diffusing element on or within the lens to improve uniformity.

11. An LED module as claimed in claim 1, wherein a portion of the inner refractive wall is at a first angle from the optic axis that is greater than is a second angle from the optic axis of a comparable portion of a refractive wall in a Reference Collimator.

12. An LED module as claimed in claim 11 wherein the distance from the center of the LED source to the inner refractive wall at a first angle from the optic axis is larger than is the distance from the center of the LED source to the inner refractive wall at a second angle from the optic axis of the comparable portion of the refractive wall in a Reference Collimator.

13. An LED module as claimed in claim 11 ,wherein a distance d₂ from the center of the LED chip to the inner refractive wall at an angle of 45°

to the optic axis (z axis) is greater than the comparable distance d₁ in a Reference Collimator.

14. An LED module as claimed in claim 1, wherein the surface of the inner refractive wall is configured using a Constant Magnification Prescription whereby the refractive wall and the reflective wall are such that equal intervals of a polar-angle direction cosine in an input beam are mapped onto equal intervals of radial distance from the axis in an output beam.

15. An LED module as claimed in claim 14, wherein the inner and outer wall surfaces are defined point-by-point and wherein the inner wall surface tapers inward towards the optic axis as the polar-angle decreases.

16. An LED module as claimed in claim 15, wherein the inner wall surface also is inflected and flared away from the optic axis.

17. An LED module as claimed in claim 1, wherein said curved portion is achieved in a structure so configured that the average angle of incidence on the inner refractive wall surface has a value close to normal incidence.

18. An LED module as claimed in claim 1, wherein said first surface of the lens is recessed away from the LED source in a structure wherein a starting point of the lens surface is shifted along a line from the focus point so that an edge ray from the LED source has a direct line-of-sight to the lens surface.

19. An LED module as claimed in claim 1, which also includes a sawtooth-like structure provided in a separate foil, which is secured to the second surface of the collimator lens.

20. An LED module as claimed in claim 1, wherein the collimator lens is injection molded.

21. An LED module as claimed in claim 1, wherein the collimator lens is manufactured in a single step.

22. A luminaire comprising a box-like housing which accommodates one or a plurality of LED modules as defined in claim 1.

23. A luminaire comprising a box-like housing which accommodates one or a plurality of LED modules as defined in claim 2.

24. A luminaire comprising a box-like housing which accommodates one or a plurality of LED modules as defined in claim 3.

25. A luminaire comprising a box-like housing which accommodates one or a plurality of LED modules as defined in claim 4.

26. A luminaire comprising a box-like housing which accommodates one or a plurality of LED modules as defined in claim 5.

27. A luminaire comprising a box-like housing which accommodates one or a plurality of LED modules as defined in claim 6.

28. A luminaire comprising a box-like housing which accommodates one or a plurality of LED modules as defined in claim 7.

29. A luminaire comprising a box-like housing which accommodates one or a plurality of LED modules as defined in claim 8.

30. A luminaire comprising a box-like housing which accommodates one or a plurality of LED modules as defined in claim 9.

31. A luminaire comprising a box-like housing which accommodates one or a plurality of LED modules as defined in claim 10.

32. A luminaire comprising a box-like housing which accommodates one or a plurality of LED modules as defined in claim 11.

33. A luminaire comprising a box-like housing which accommodates one or a plurality of LED modules as defined in claim 12.

34. A luminaire comprising a box-like housing which accommodates one or a plurality of LED modules as defined in claim 17.