Lamp with variable-beam output by discretely activating LED light sources
Lamp including an array of LEDs disposed at or near the focus of a reflecting optic having multiple segments with different aiming angles (i.e. the angle corresponding to a reflected beam output direction), and a driver circuit for discretely activating some of the LEDs in the array. The angular distribution of the output light beam (e.g., the beam divergence) is adjusted by selectively changing the currents supplied to the LEDs.
1. A light source producing a beam of variable divergence, comprising:
a plurality of light-emitting devices arranged on a plane that includes a first set of light emitting devices positioned around a second set of light emitting devices;
a concave reflecting optic having an axis of symmetry traveling through the second set of light emitting diodes, and comprising a plurality of segments for reflecting at least a portion of light emitted by the light-emitting devices and reflected by the optic forming a light beam, the segments having an aiming angle which increases gradually with increasing distance from the plane of the plurality of light emitting devices for increasing light divergence of the light beam; and
driver circuitry for controlling drive currents to the light-emitting devices such that a maximum divergence of the light beam is produced by said driver circuitry powering outermost light emitting devices of the first set of light emitting devices, and a gradually decreasing divergence of the light beam is produced by said driver circuitry decreasing a number of powered outermost light emitting devices of the first set of light emitting devices while selectively powering a combination of the inner light emitting devices of the first set of light emitting devices and the second set of light emitting devices.
2. The light source of claim 1 , wherein the reflecting optic comprises two regions, segments in a first region having relatively large aiming angles with respect to the axis of symmetry for providing divergence of the light beam and segments in a second region having relatively small aiming angles with respect to the axis of symmetry for collimating the light beam.
3. The light source of claim 1 , wherein the segments are parabolic and the light-emitting devices are disposed substantially at a focus of the parabolic segments.
4. The light source of claim 1 , wherein the light-emitting devices are arranged in a pattern having a center, the driver circuitry being configured to control the drive currents to the light-emitting devices based on their distances from the center.
5. The light source of claim 1 , wherein the driver circuitry is configured to selectively drive a subset of the light-emitting devices so as to generate a pattern.
6. The light source of claim 1 , wherein the driver circuitry is programmable.
7. The light source of claim 1 , wherein an area density of the light-emitting devices is uniform.
8. The light source of claim 1 , wherein the driver circuitry is configured to control the drive currents based on at least one of sizes or positions of respective light-emitting devices.
9. The light source of claim 1 , wherein the light-emitting devices are arranged in a pattern having a center region and an outer region outside the center region, light-emitting devices located in the center region being higher-power devices than light-emitting devices located in the outer region.
10. The light source of claim 1 , wherein the aiming angle of each segment with respect to the axis of symmetry increases gradually as the distance between the segment and the plane of the light-emitting devices decreases.
11. The light source of claim 10 , wherein the reflecting optic comprises first and second edge segments having a shortest distance and a longest distance, respectively, from the plane of the light-emitting devices, the first edge segment having a first aiming angle approximately equal to a desired divergence angle of the light beam and the second edge segment having a second aiming angle approximately parallel to the axis of symmetry for collimating the light beam.
12. The light source of claim 1 , wherein the light-emitting devices are arranged symmetrically.
13. The light source of claim 12 , wherein the arrangement of the light-emitting devices is circularly symmetric or radially symmetric.
14. The light source of claim 12 , wherein the light-emitting devices are arranged in a pattern having a center region and an outer region outside the center region such that none of the light-emitting devices is located in the center region.
15. The light source of claim 1 , wherein the light-emitting devices comprise LEDs.
16. The light source of claim 15 , wherein the LEDs are disposed on a single substrate having a plurality of electrical contacts.
17. The light source of claim 16 , wherein the substrate comprises a semiconductor material.
18. A method of varying a divergence of a light source comprising (i) a plurality of light-emitting devices arranged on a plane and in a pattern having a center region and an outer region outside the center region, (ii) a concave reflecting optic having an axis of symmetry and a plurality of segments, each segment having an aiming angle with respect to the axis of symmetry for redirecting light emitted thereon, the concave reflecting optic including a portion of the plurality of segments having a gradually increasing aiming angle with increasing distance from the plane of the plurality of light emitting diodes for increasing light divergence, and (iii) a driver circuitry for selectively controlling a drive current supplied to the light emitting devices, the method comprising:
driving the light-emitting devices to create a light beam emerging from the reflecting optic; and
controlling the divergence of an output beam of the light source by the driver circuitry controlling drive currents to the light-emitting devices based on distances of the devices from the axis of symmetry, wherein a maximum divergence of the output beam is produced by supplying a drive current to the light emitting devices outermost from the axis of symmetry, and an output beam with a gradually decreasing divergence is produced by selectively supplying a drive current for decreasing a number of powered outermost light emitting devices while powering light emitting devices closer to the axis of symmetry.
19. The method of claim 18 , wherein the reflecting optic comprises two regions, segments in a first region having relatively large aiming angles with respect to the axis of symmetry for providing divergence of the light beam and segments in a second region having relatively small aiming angles with respect to the axis of symmetry for collimating the light beam.
20. The method of claim 18 , wherein the segments are parabolic and the light-emitting devices are disposed substantially at a focus of the parabolic segments.
21. The method of claim 18 , wherein an area density of the light-emitting devices is uniform.
22. The method of claim 18 , wherein controlling the drive currents comprises decreasing the drive currents to the light-emitting devices in an outer region thereof to thereby narrow the beam.
23. The method of claim 18 , further comprising simultaneously and uniformly varying the drive currents to all light emitting devices to thereby vary the beam brightness.
24. The method of claim 18 , wherein the aiming angle of each segment with respect to the axis of symmetry increases gradually as the distance between the segment and the plane of the light-emitting devices decreases.
25. The method of claim 24 , wherein the reflecting optic comprises first and second edge segments having a shortest distance and a longest distance, respectively, from the plane of the light-emitting devices, the first edge segment having a first aiming angle approximately equal to a desired divergence angle of the light beam and the second edge segment having a second aiming angle approximately parallel to the axis of symmetry for collimating the light beam.
26. The method of claim 18 , wherein the light-emitting devices are arranged symmetrically.
27. The method of claim 26 , wherein the arrangement of the light-emitting devices is circularly symmetric or radially symmetric.
28. The method of claim 26 , wherein the light-emitting devices are arranged in a pattern having a center region and an outer region outside the center region such that none of the light-emitting devices is located in the center region.
29. The method of claim 18 , wherein the light-emitting devices comprise LEDs.
30. The method of claim 29 , wherein the LEDs are disposed on a single substrate having a plurality of electrical contacts.
31. The method of claim 30 , wherein the substrate comprises a semiconductor material.