Illuminating lens designed by extrinsic differential geometry

• US 5,924,788 A
• Filed: 09/23/1997
• Issued: 07/20/1999
• Est. Priority Date: 09/23/1997
• Status: Expired due to Fees

• Current Assignee: Teledyne Lighting & Display Products, Inc. (Teledyne Technologies Incorporated)
• Original Assignee: Teledyne Lighting & Display Products, Inc. (Teledyne Technologies Incorporated)
• Inventors: Parkyn, William A. Jr.
• Primary Examiner(s): Sember, Thomas M.
• Application Number:
  US08/935,774
• Time in Patent Office: 665 Days
• Field of Search: 362/545, 362/249, 362/800, 362/311, 362/332, 362/335, 362/329, 362/328, 362/235, 362/240
• US Class Current: 362/329
• 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 27/0012 Optical design, e.g. procedures, algorithms, optimisation routines
• CPC Class Codes: G02B 3/02 with non-spherical faces G02B3/10 takes precedence
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

An illumination system with a prescribed output pattern comprising a light source and an optical lens redirecting the light of the source into an output beam, the lens with multiple surfaces at least one of which has a shape that is not a surface of revolution, the shape generated by the following method: on the Gaussian sphere of directions of the output beam exiting the surface of the lens, in accordance with the prescribed output pattern, establish a first grid of equal-flux zones of solid angle; on a portion of the Gaussian sphere of directions of the light emitted from the source into the interior of the lens, establish a second grid with the same number of equal-flux zones of solid angles as the first grid, with a coordinate-system topology congruent with that of the first grid, such that the zones of the second grid are in one-to-one correspondence with the zones of the first grid, with the flux of each zone in proportion to its corresponding zone of the first grid, according to the local transmittance of the lens, with either of both of the grids being rotationally non-symmetric; by this correspondence define a flux-redistributing directional mapping function from the first Gaussian sphere to the second Gaussian sphere, whereby any light ray from the source can be assigned a direction in the output beam, according to the zone of the second grid into which the ray falls, so that the redirected ray falls in the corresponding zone of the first grid; establish one or more lens surfaces to redirect the source rays to the output rays, using the vector laws of refraction or reflection to derive a distribution of normal vectors for each surface; from the distributions of normal vectors, successively generate each lens surface, beginning with that nearest source and going outwards.

Claims

1. An illumination system with a prescribed output pattern comprising a light source and an optical lens redirecting the light of said source into an output beam, said lens with multiple surfaces at least one of which has a shape that is not a surface of revolution, said shape generated by the following method:

a) on a Gaussian sphere of directions of said output beam exiting a surface of said lens in accordance with said prescribed output pattern, establish a first grid of equal-flux zones of solid angle,

b) on a portion of the Gaussian sphere of directions of the light emitted from said source into an interior of said lens, establish a second grid with the same number of equal-flux zones of solid angles as said first grid, with a coordinate-system topology congruent with that of said first grid, such that the zones of said second grid are in one-to-one correspondence with the zones of said first grid, with the flux of each zone in proportion to its corresponding zone of said first grid, according to a local transmittance of said lens, with either of both of said grids being rotationally non-symmetric,

c) by said correspondence define a flux-redistributing directional mapping function from said first Gaussian sphere to said second Gaussian sphere, whereby most light rays from said source can be assigned a direction in said output beam, according to the zone of said second grid into which each of said rays fall, so that said redirected ray falls in the corresponding zone of said first grid,

d) establish one or more lens surfaces to redirect the source rays to the output rays, using the vector laws of refraction or reflection to derive a distribution of normal vectors for each surface, and

e) from said distributions of normal vectors, successively generate each lens surface, beginning with that nearest said source and progressing outwards.

2. The system of claim 1 whereby the said lens surfaces are generated from said distributions of normal vectors by the following method:

f) from an initial starting point, calculate surface coordinates of each surface of said lens by contact-integrating said distribution of surface normal vectors, along an initial strip that follows one principal curvature of the surface and then, by successive contact-integrations, orthogonally outwards from said initial strip, of said grid of surface normals, generate adjacent characteristic strips outward to a boundary of said second grid,

g) to ensure that the surface of said lens possesses surface normals necessary for it to transform the light from said source into an output beam substantially fulfilling said prescription, perform successive integrations of adjacent characteristic strips so as to fulfill the integrability condition dictating equality of crossed second derivatives of the surface of said lens,

h) and determine an overall size of said lens relative to a size of said light source by selecting a distance of said initial point from said source to keep the angular blurring by a finite size of said source of said output beam below a level defined by an angular resolution of said prescription.

3. The system of claim 1 wherein said source is provided to be in optical contact with said lens, and said redirection is from within a lens material outwards into the environment, by refraction, with said distribution of surface normals determined by the vector form of Snell'"'"'s law of refraction.

4. The system of claim 1 wherein said lens is provided to have an entry surface admitting light from said source into its interior and an exit surface for light leaving said interior.

5. The system of claim 4 wherein said entry surface performs negligible redirection, and substantially an entirety of said redirection is performed by an external surface.

6. The system of claim 4 wherein said entry surface redirects said source light, so that a new system of interior rays is used to generate the surface normal distributions of both of said surfaces, with a total redirection of said source light allocated between said entry and exit surface normals.

7. The system of claim 4 wherein said source is provided to be a high-temperature lamp.

8. The system of claim 7 wherein said source is an incandescent lamp, said prescription is the Coast Guard 360-degree masthead navigation light, and said lens has a horizontal cross section with a teardrop shape that eliminates shadowing of a filament of said lamp by support posts of said filament.

9. The system of claim 7 wherein said source is an incandescent lamp with a substantially cylindrical filament in a vertical orientation, said prescription is the Coast Guard 225-degree forward navigation light.

10. The combination of the system of claim 7 wherein said source is an incandescent lamp with a substantially cylindrical filament in a vertical orientation, said prescription is the Coast Guard 135-degree stern navigation light, and said lens utilizes a reflective surface to redirect a portion of the output of said lamp into said prescribed output.

11. The system of claim 1 including providing a reflecting surface, and wherein large redirection angles are implemented with said reflecting surface.

12. The system of claim 11 wherein said reflecting surface utilizes total internal reflection.

13. The system of claim 11 wherein said reflecting surface utilizes a thin-film metal coating.

14. The system of the combination of claims 11 wherein said reflecting surface is generated by the method that includes:

a) partitioning said first grid into an inner refraction-only portion and an outer reflection-assisted zone, according to the maximum practical redirection angle of the refractive index of the material of said lens, and effect a corresponding partition of said third grid of light interior to said lens,

b) surrounding an exterior surface of the central refraction-only portion of said lens, establish an outer conicoid portion of the exterior surface of said lens, said conicoid tilted so as to minimize the impingement upon it of rays coming directly from said source,

c) via backwards ray tracing of refraction through said tilted surface, transform said outer portion of said first grid into a grid upon the Gaussian sphere of directions of light interior to said lens,

d) establish a one-to-one correspondence between said partial grid of backwards-ray-traced light interior to said lens and said outer portion of said third grid,

e) by the vector form of the law of reflection, express said correspondence by establishing on said outer portion of said third grid an overlaying distribution of surface normal vectors,

f) utilizing the outer perimeter of said tilted exterior surface as an initial strip, mathematically generate the surface coordinates of said reflective surface by said method of contact integration of orthogonal characteristic strips,

g) and extending said conical surface sufficiently far so that said characteristic strips will not impinge upon said light source or said inner lens surface.

15. The method of claim 14 wherein said lens is characterized as having surfaces the selected from the group consisting of

a) TIR surface,

b) mirror surface.

16. The method of claim 14 wherein said source is selected from the group consisting of

a) an incandescent light,

b) an LED,

c) an array of LEDs,

d) together with a light diffuser through which source light passes before entering the lens,

e) an LED together with a light diffuser through which source light passes before entering the lens

f) an array of LEDs together with a light diffuser through which source light passes before entering the lens.

17. The method of claim 14 wherein said output prescription is the U.S. Department of Transportation photometric standard for automotive stop lamps, center high mounted stop lamps, directional markers, or side markers, and said source is one or more light-emitting diodes.

18. The method of claim 14 wherein said output prescription is an Institute of Transportation Engineers standard for automotive or railroad colored traffic signals, and said light source is a red, yellow, green, or blue light-emitting diode.

19. The method of claim 14 wherein said output prescription corresponds to an illuminance pattern on a nearby non-spherical surface.

20. The system of claim 1 wherein said output prescription is one of the Coast Guard standards for navigation lights.

21. The system of claim 1 wherein said output prescription is a Society of Automotive Engineers'"'"' standard for vehicular lights.

22. The system of claim 1 wherein said source is one or more light emitting diodes.

23. The system of claim 22 including providing said lens to have a bulbous shape with quadrilateral symmetry comprised by a horizontal major axis and a vertical minor axis.

24. The system of claim 22 wherein said light-emitting diodes are provided to have several wavelengths so as to metamerically combine their light for white color.

25. The system of claim 22 wherein said multiple light-emitting diodes are provided to have several wavelengths and have individual intensity controls capable of video signal rendition.

26. The system of claim 25 wherein multiple said lenses lie in an array comprising a video screen for display of television or computer imagery, so that each of said lenses comprises a pixel of said display.

27. The system of claim 26 wherein said multiple lenses have output prescriptions aimed at a specific audience location.

28. The system of claim 25 wherein said array of lenses is mounted on a surface of low reflectance.

29. The system of claim 1 wherein said output prescription is provided in terms of an illuminance pattern on a nearby non-spherical surface.

30. For use in providing an illumination system with a prescribed output pattern comprising a light source and an optical lens redirecting the light of said source into an output beam, said lens with a shape that is not a surface of revolution, said shape generated by the method that includes:

a) on a Gaussian sphere of directions of said output beam exiting a surface of said lens, in accordance with said prescribed output pattern, establish a first grid of equal-flux zones of solid angle,

b) on a portion of the Gaussian sphere of directions of the light emitted from said source into an interior of said lens, establish a grid with the same number of equal-flux zones of solid angle as said first grid, and with a coordinate system topology congruent with that of said first grid, such that the zones of said second grid are in one-to-one topological correspondence with the zones of said first grid, with the flux of each zone of said second grid in proportion to the flux of its corresponding zone of said first grid, according to a local transmittance of said lens, with either or both of said grids being rotationally non-symmetric,

c) by use of said correspondence, define a flux-redistributing directional mapping function from said first Gaussian sphere to said second Gaussian sphere, whereby any light ray from said source is assigned a direction in said output beam, according to the zone of said second grid into which said ray falls, and so that the redirected ray also falls in the corresponding zone of said first grid,

d) by the vector form of Snell'"'"'s law of refraction, express said correspondence by establishing on said second grid an overlaying distribution of surface normal vectors,

e) from an initial starting point, mathematically generate the surface coordinates of said lens by contact-integrating said distribution of said surface normal vectors, along an initial strip that follows a principal curvature of the surface, and then, by successive contact-integrations, orthogonally outwards from said initial strip, of said surface normals, generate adjacent characteristic geodesic strips that follow the other principal curvature of said lens surface, outward to a boundary of said second grid,

f) perform successive integrations of adjacent characteristic geodesic strips, so as to fulfill an integrability condition dictating equality of crossed second derivatives of the surface of said lens, thereby to ensure that the surface of said lens possesses the surface normals necessary for it to transform the light from said source into an output beam substantially fulfilling said prescription,

g) and determine an overall size of said lens relative to a size of said light source by selecting a distance of said initial point from said source so as to keep the blurring of said output beam below a level defined by an angular resolution of said prescription.

31. The method of claim 30 wherein said lens is characterized as employing two refractive surfaces.

32. The method of claim 31 wherein said two refractive surfaces are generated by the method that includes:

a) on the Gaussian sphere of directions of said output beam exiting said outer refractive surface of said lens, in accordance with said prescribed output pattern, establish a first grid of equal-flux zones of solid angle,

b) on a portion of the Gaussian sphere of directions of light exiting said source into air, establish a grid with the same number of equal-flux zones of solid angle as said first grid, and with a coordinate-system topology congruent with that of said first grid, such that the zones of said second grid are in one-to-one topological correspondence with the zones of said first grid, with the zones of said first grid, with the flux of each zone of said second grid in proportion to the flux of its corresponding zone of said first grid, according to the local transmittance of said lens,

c) on the Gaussian sphere of directions of light refracted into said interior of said lens by said inner surface, establish a third grid with the same number of equal-flux zones of solid angle as said second grid, and with a coordinate system topology congruent with that of said second grid, such the zones of said third grid are in one-to-one topological correspondence with the zones of second grid, with the flux of each zone of said third grid in proportion to the flux of its corresponding zone of said second grid, according to the local transmittance of said inner surface of said lens, with any one, any two, or all three of said grids being rotationally non-symmetric,

d) by the use of said correspondences, define flux-redistributing directional mapping functions from said first Gaussian sphere to said third Gaussian sphere, and from said second Gaussian sphere to said third Gaussian sphere, whereby most light rays from said source is assigned a direction in said output beam, according the zone of said second grid into which each said ray falls, so that a refracted interior ray also falls in the corresponding zone of said third grid, and so that a refracted output ray also falls in the corresponding zone of said first grid,

e) by the vector form of Snell'"'"'s law of refraction, express said correspondences by establishing on said second grid an overlaying distribution of surface normal vectors for said interior lens surface and by establishing on said third grid an overlaying distribution of surface normal vectors for said exterior lens surface,

f) from an initial starting point, mathematically generate the surface coordinates of said interior surface of said lens by contact-integrating said distribution of said surface normal vectors on said second grid, along an initial strip that follows a principal curvature of said interior surface, and then, by successive contact-integrations, orthogonally outwards from said initial strip, of said surface normals, generate adjacent characteristic geodesic strips that follow the other principal curvature of said interior lens surface, outward to the boundary of said second grid,

g) at a suitable distance along the interior ray refracted from said initial starting point of said interior surface of said lens, establish an initial starting point for said exterior surface of said lens, and by said method of contact integration generate said exterior surface, said suitable distance determined by keeping said exterior surface from intersecting said interior surface at any point inside the boundary of said interior surface,

h) and determine the overall size of said lens relative to the size of said light source by selecting the distance of said initial point of said interior surface of said lens from said source so as to keep the blurring of said output beam below a level defined by the angular resolution of said prescription.

33. The method of claim 30 wherein said source is in optical contact with said lens.

34. The method of claim 30 wherein said lens has an entry surface admitting source light to its interior.

35. The method of claim 30 wherein said output prescription is the Coast Guard standard for navigation lights and said source is one or more light-emitting diodes, said lens having a bulbous shape, with quadrilateral symmetry comprised by a horizontal major axis and a vertical minor axis.

37. The method of claim 30 wherein said lens body is assembled to have an overall length L₁ and overall width W₂, above said base, where L₁ >

W₂.

38. The method of claim 30 including locating the LED in a base, so that there is no air gap between the LED means and the lens body, which is light transmitting.

39. The method of claim 32 whereby said third grid is established so that said interior and exterior surfaces have substantially equal amounts of refraction.

36. In combination, an optical lens in the form of an asymmetric dome-shaped body located above an integral support base, and LED light source means associated with said base, said base upwardly divergent relatively away from a recess, and wherein said light source means is embedded in a transparent mass of material received in the recess, said base and dome-shaped body being laterally elongated, said dome-shaped body overhanging said base, and said body being generally ellipsoidal in lateral horizontal planes above said base.

40. A luminaire comprising:

a) a lens body having a forwardly dome-shaped inner portion, and an outer portion extending abut and spaced from said inner portion, said portions being light-transmitting, and integral,

b) the inner portions extending non-circularly about a forwardly and upward axis,

c) their being a reflector on said outer portion, whereby a light source in rearward alignment with said inner portion provides certain light rays that travel forwardly and are refracted by said dome-shaped inner portion to travel forwardly from said inner portion, and other light rays that travel in said outer portion and are reflected by said reflector to travel forwardly in said outer portion, and forwardly from said outer portion,

d) said dome-shaped inner portion located above an integral base, said light source associated with said base, said base upwardly divergent relatively away from a recess, and wherein said light source means is embedded in a transparent mass of material received in the recess, said base and dome-shaped body being laterally elongated, said dome-shaped body overhanging said base, and said body being generally ellipsoidal in lateral horizontal planes above said base.