Optical feedback system with improved accuracy

• US 7,482,567 B2
• Filed: 08/18/2005
• Issued: 01/27/2009
• Est. Priority Date: 09/24/2004
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Hoelen, Christoph Gerard August, Ansems, Johannes Petrus Maria, Van Lier, Edwin
• Primary Examiner(s): Luu; Thanh X
• Application Number:
  US11/575,515
• Publication Number:
  US 20080093530A1
• Time in Patent Office: 1,258 Days
• Field of Search: 250/205, 250/216, 345/76, 345/77, 362326-340, 362/552, 362/231, 359726-731, 359856-861
• US Class Current: 250/205
• CPC Class Codes: F21K 9/62 using mixing chambers, e.g. housings with reflective walls
• CPC Class Codes: F21V 23/0457 the sensor sensing the operating status of the lighting device, e.g. to detect failure of a light source or to provide feedback to the device
• CPC Class Codes: F21Y 2113/13 comprising an assembly of point-like light sources
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: G01J 1/04 Optical or mechanical part supplementary adjustable parts
• CPC Class Codes: G01J 1/0407 Optical elements not provided otherwise, e.g. manifolds, windows, holograms, gratings
• CPC Class Codes: G01J 1/32 adapted for automatic variation of the measured or reference value regulation of light intensity G05D25/00
• CPC Class Codes: G01J 2001/4247 for testing lamps or other light sources
• CPC Class Codes: G01J 3/505 measuring the colour produced by lighting fixtures other than screens, monitors, displays or CRTs
• CPC Class Codes: G01J 3/513 having fixed filter-detector pairs
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 25/167 comprising optoelectronic devices, e.g. LED, photodiodes
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

The illumination system has a plurality of light emitters (R, G, B) and a light-collimator (1) for collimating light emitted by the light emitters. Light propagation in the light-collimator is based on total internal reflection (TIR) towards a light-exit window (4) of the light-collimator. At least one light sensor (8) for optical feedback is placed outside the light-collimator and is arranged to receive light emitted by the light emitters exclusively through reflection at the light-exit window of the light-collimator. Preferably, the light sensor is placed substantially coplanar with the light emitters. Preferably, a side wall (35) of the light-collimator is provided with a protruding portion (9) for guiding the light reflected at the light-exit window of the light-collimator towards the light sensor. Preferably, the illumination system is provided with a reflector (12). Preferably, the illumination system comprises a holographic diffuser (17). Accurate sensing of the color mixing of light emitted by the illumination system is obtained.

Claims

1. An illumination system comprising:

a plurality of light emitters,

a light-collimator for collimating light emitted by the light emitters,

light propagation in the light-collimator being based on total internal reflection,

at least one light sensor for optical feedback being placed outside the light-collimator,

the light sensor being arranged to receive light emitted by the light emitters exclusively through reflection at a light-exit window of the illumination system,

wherein the light sensor is connected to a controller for controlling the electrical current of the light emitters in response to the light received by the light sensor.

2. An illumination system as claimed in claim 1, wherein the light sensor is placed substantially coplanar with the light emitters.

3. An illumination system as claimed in claim 1, wherein the controller employs time-resolved detection.

4. An illumination system as claimed in claim 1, wherein detection in the controller is synchronous with pulse-width driving of the light-emitters.

5. An illumination system as claimed in claim 1, wherein the controller employs frequency-resolved detection in combination with a driving scheme of the light emitters that operates in pre-defined frequency bands.

6. An illumination system as claimed in claim 1, wherein the illumination system comprises at least two sensors provided with color filters for determining a color point of the light emitted by the illumination system, the controller influencing the color of the point of the light emitted by the illumination system.

7. An illumination system as claimed in claim 1, wherein the illumination system further comprises a thermal sensor, the controller controlling the electrical current of the light emitters in response to the information received from the thermal sensor.

8. An illumination system as claimed in claim 1, wherein the light-collimator is made from a dielectric material with a refractive index larger than or equal to 1.3.

9. An illumination system as claimed in claim 1, wherein the light emitters comprise at least a first light-emitting diode (R) of a first primary color, at least a second light-emitting diode (G) or a second primary color, and at least a third light-emitting diode (B) of a third primary color, the three primary colors being distinct from each other.

10. An illumination system as claimed in claim 9, wherein each of the the first, second, and third light-emitting diodes has a radiant power output of at least 25 mW when driven at nominal power and at room temperature.

11. An illumination system comprising:

a plurality of light emitters,

a light-collimator for collimating light emitted by the light emitters,

light propagation in the light-collimator being based on total internal reflection,

at least one light sensor for optical feedback being placed outside the light-collimator,

the light sensor being arranged to receive light emitted by the light emitters exclusively through reflection at a light-exit window of the illumination system,

wherein a side wall of the light-collimator is provided with a protruding portion for guiding the light reflected at the light-exit window of the light-collimator towards the light sensor.

12. An illumination system comprising:

a plurality of light emitters,

a light-collimator for collimating light emitted by the light emitters,

propagation in the light-collimator being based on total internal reflection,

at least one light sensor for optical feedback being placed outside the light-collimator,

the light sensor being arranged to receive light emitted by the light emitters exclusively through reflection at a light-exit window of the illumination system,

wherein the illumination system comprises a holographic diffuser, the holographic diffuser being provided at the light-exit window of the light-collimator.

13. An illumination system comprising:

a plurality of light emitters,

a light-collimator for collimating light emitted by the light emitters,

light propagation in the light-collimator being based on total internal reflection,

at least one light sensor for optical feedback being placed outside the light-collimator,

the light sensor being arranged to receive light emitted by the light emitters exclusively through reflection at a light-exit window of the illumination system,

wherein the light-collimator is provided with a reflector, and

wherein the reflector is facetted or is shaped substantially according to a compound parabolic concentrator.

14. An illumination system as claimed in claim 13, wherein the illumination system comprises a holographic diffuser, the holographic diffuser being provided at a light-exit window of the reflector.

15. An illumination system comprising:

a plurality of light emitters,

a light-collimator for collimating light emitted by the light emitters,

light propagation in the light-collimator being based on total internal reflection,

at least one light sensor for optical feedback being placed outside the light-collimator,

the light sensor being arranged to receive light emitted by the light emitters exclusively through reflection at a light-exit window of the illumination system,

wherein the light emitters comprise at least a first light-emitting diode of a first primary color and at least a second light-emitting diode of a second primary color, the first and the second primary colors being distinct from each other.