BEAM SPREADING OPTICS FOR LIGHT EMITTING DIODES

• US 20100195335A1
• Filed: 02/03/2009
• Published: 08/05/2010
• Est. Priority Date: 02/03/2009
• Status: Active Grant

• Current Assignee: ABL IP Holding LLC (Acuity Brands, Inc.)
• Original Assignee: OSRAM Sylvania Inc. (Ams-Osram AG)
• Inventors: Luo, Hong, Allen, Steven C., Hohl-AbiChedid, Angela
• Granted Patent: US 8,449,150 B2
• Time in Patent Office: Days
• US Class Current: 362/309
• CPC Class Codes: F21K 9/232 specially adapted for generating an essentially omnidirectional light distribution, e.g. with a glass bulb
• CPC Class Codes: F21K 9/60 Optical arrangements integrated in the light source, e.g. for improving the colour rendering index or the light extraction
• CPC Class Codes: F21V 5/048 the lens being a simple lens adapted to cooperate with a point-like source for emitting mainly in one direction and having an axis coincident with the main light transmission direction, e.g. convergent or divergent lenses, plano-concave or plano-convex lenses
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• CPC Class Codes: G02B 19/0061 the light source comprising a LED semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission H01L33/00
• CPC Class Codes: G02B 19/0071 adapted to illuminate a complete hemisphere or a plane extending 360 degrees around the source
• CPC Class Codes: G02B 27/0955 Lenses lenses per se G02B3/00
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

An optical element is disclosed, for receiving relatively narrow light from a planar light-emitting diode (LED) source, and for redistributing the light into a relatively wide range of output angles that span a full 360 degrees. The element may be used to retrofit existing fixtures that were originally designed for incandescent bulbs with LED-based light sources that have similar emission profiles. The element is small enough so that it may be packaged along with an LED module and its control electronics in the volume envelope of an incandescent light bulb. An exemplary element is a single, transparent, rotationally-symmetric lens that has a batwing shape in cross-section, extending angularly away from a longitudinal axis. The lens also includes a variety of curved, straight, specular and optionally diffuse portions on its longitudinal and transverse faces, all of which cause a variety of internal and external reflections, refractions, and optionally scattering. As such, many of the specific lens features cannot be directly linked to specific optical effects at a particular angle; rather, the features all interact with each other to produce the wide-angle light output.

Claims

1. A device (10) for angularly broadening light emitted from a light-emitting diode module (3), comprising:

a lens (10A) having a symmetry about a longitudinal axis (39);

the lens (10A) comprising a transparent material bounded by an exterior surface;

the exterior surface comprising a batwing structure that converts a Lambertian input distribution (4) of light rays emitted from the light-emitting diode module (3) into a generally uniform output distribution (5) of light rays emerging from the lens (10A);

the batwing structure comprising a proximal portion facing the light-emitting diode module (3), the proximal portion comprising;

a concave portion (29) at the center of the proximal portion, wherein any light ray that enters the lens (10A) from the light-emitting diode module (3) does so through the concave portion (29); and

a total internal reflection portion (32) circumferentially surrounding the concave portion (29), wherein any light ray that enters the lens (10A) through the concave portion (29) and directly strikes the total internal reflection portion (32) does so at an incident angle greater than a critical angle for the lens (10A).

2. The device (10) of claim 1,

wherein the Lambertian input distribution (4) of light rays includes a plurality of input light rays, each input light ray in the plurality having an input relationship between relative power and propagation direction, the input relationship varying as a cosine between the propagation direction and the longitudinal axis (39);

and

wherein the generally uniform output distribution (5) of light rays includes a plurality of output light rays, each output light ray in the plurality having an output relationship between relative power and propagation direction, the output relationship being roughly uniform over all propagation directions.

3. The device (10) of claim 2, wherein the roughly uniform output relationship comprises a peak value of 100%, an average value between 60% and 80%, and a minimum value between 20% and 50%.

4. The device (10) of claim 2, wherein the roughly uniform output relationship comprises a peak value of 100%, an average value between 65% and 75%, and a minimum value between 30% and 40%.

5. The device (10) of claim 2, wherein the roughly uniform output relationship comprises a peak value of 100%, an average value of about 70%, and a minimum value of about 35%.

6. The device (10) of claim 1, wherein the lens (10A) has a rotational symmetry about the longitudinal axis (39).

7. The device (10) of claim 1, wherein, for a plane that includes the longitudinal axis (39), for each direction within the plane spanning 360 degrees with respect to the longitudinal axis (39), the generally uniform output distribution (5) of light rays emerging from the lens (10A) comprises at least one emergent light ray propagating along each direction.

8. The device (10) of claim 1, wherein the generally uniform output distribution (5) of light rays emerging from the lens (10A) comprises:

a first plurality of light rays that enter the lens (10A) through the concave portion (29) and then directly exit the lens (10A) through the batwing structure; and

a second plurality of light rays that enter the lens (10A) through the concave portion (29), internally reflect at least once from the batwing structure, then exit the lens (10A) through the batwing structure.

9. The device (10) of claim 8, wherein for the first and second pluralities of light rays, the entering and exiting comprises refraction through the batwing structure, the refraction including a change in ray direction governed by Snell'"'"'s Law and a reduction in relative power governed by a Fresnel transmitted power coefficient.

10. The device (10) of claim 8, wherein for the second plurality of light rays, the internal reflection from the batwing structure includes a change in ray direction governed by the law of reflection and, for incident angles less than the critical angle of the lens (10A), a reduction in relative power governed by a Fresnel reflected power coefficient.

11. The device (10) of claim 1, wherein the critical angle of the lens (10A) is the arc sine of (one divided by a refractive index of the lens (10A)).

12. The device (10) of claim 1,

wherein the concave portion (29) is hemispherical;

and

wherein any light ray that enters the lens (10A) from the light-emitting diode module (3) does so at normal incidence through the concave portion (29).

13. The device (10) of claim 1, wherein a radial cross-section of the total internal reflection portion (32) is straight, is largely perpendicular to the longitudinal axis (39), and advances in the proximal to distal direction from the center to a lateral edge (33) of the lens (10A).

14. The device (10) of claim 1, wherein the exterior surface includes at least one bump (38) on a distal portion opposite the proximal portion, the at least one bump (38) being proximate the longitudinal axis (39).

15. The device (10) of claim 1, wherein the exterior surface includes a lateral edge (33) parallel to the longitudinal axis (39) and directly adjacent to the total internal reflection portion (32).

16. The device (10) of claim 1, wherein a ratio of a lateral diameter of the lens (10A), divided by a diameter of concave portion (29) is in the range of 6:

1 and 4;

1.

17. The device (10) of claim 1, wherein the exterior surface includes a distal curvilinear portion (35, 36) facing away from the light-emitting diode module (3), the distal curvilinear portion including a distal convex portion (35) and a distal concave portion (36), the distal convex portion (35) defining a maximum distal longitudinal extent of the lens (10A).

18. The device (10) of claim 1, wherein the lens (10A) has an inner longitudinal thickness (41) proximate the longitudinal axis (39), an outer longitudinal thickness (43) proximate an outer radial edge (33) of the lens (10A), and an intermediate longitudinal thickness (42) between the longitudinal axis (39) and the radial edge (33) of the lens (10A), the intermediate longitudinal thickness (42) being greater than both the inner longitudinal thickness (41) and the outer longitudinal thickness (43).

19. The device (10) of claim 1, wherein at least one portion of the exterior surface is slightly roughened.

20. A device (10) for broadening an angular light output of a light-emitting diode module (3), comprising:

a lens (10A) for receiving light from the light-emitting diode module (3) and emitting light into a plurality of exiting angles, the lens (10A) having a characteristic emission pattern (6) wider than that (4) of the light emitting diode module (3), the lens (10A) comprising a material having a refractive index greater than one, the material bounded by an exterior surface, a radial cross-section of the exterior surface comprising;

a first linear section (32) extending away from a longitudinal axis (39) of the lens (10A);

a second substantially linear section (33) adjacent to the first linear section (32) and substantially parallel to the longitudinal axis (39) of the lens;

a third linear section (34) adjacent to the second linear section (33) and extending toward the longitudinal axis (39) of the lens (10A); and

a curvilinear portion adjacent to the third linear section (34) and extending toward the longitudinal axis (39) of the lens (10A), the curvilinear portion including a convex portion (35) and a concave portion (36).

21. A wide-angle light emission system, comprising:

a generally planar light emitting diode module (3) for emitting light in an angular distribution centered around a longitudinal axis (39), the longitudinal axis being substantially perpendicular to the light emitting diode module (3); and

a lens (10A) for receiving light from the planar light emitting diode module (3);

wherein the lens (10A) extends longitudinally away from the light emitting diode module (3) and is disposed on only one side of the light emitting diode module plane;

wherein the lens (10A) has an inner longitudinal thickness (41) proximate the longitudinal axis (39), an outer longitudinal thickness (43) proximate an outer radial edge (33) of the lens (10A), and an intermediate longitudinal thickness (42) between the longitudinal axis (39) and the radial edge (33) of the lens (10A), the intermediate longitudinal thickness (42) being greater than both the inner longitudinal thickness (41) and the outer longitudinal thickness (43);

wherein the lens (10A) comprises a material having a refractive index greater than one, the material having an exterior surface, a radial cross-section of the exterior surface having a distal side facing away from the light emitting diode module (3), the distal side including both a distal convex portion (35) and a distal concave portion (36), and having a proximal side facing toward the light emitting diode module (3), the proximal side including;

a proximal concave portion (29) at the center of the proximal side for receiving light from the light-emitting diode module (3); and

a total internal reflection portion (32) circumferentially surrounding the proximal concave portion (29) for totally internally reflecting light that enters the lens (10A) through the concave portion (29) and directly strikes the total internal reflection portion (32).