LED luminaire with electrically adjusted color balance using photodetector
US6495964B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 27, 2000 |
| Grant date | Dec 17, 2002 |
| Priority date | — |
| Expiry date | Feb 14, 2021 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B6/003
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
The combined light output (chromaticity) of a white light emitting LED luminaire is electronically controlled based on measurements by a single photodiode arranged to measure the light outputs of at least a plurality of the LEDs in the array. This is accomplished by measuring the light output of the LEDs in each color separately in a sequence of time pulses. For an array of red, green, and blue LEDs there are three time pulses in a measuring sequence. During each time pulse, the current for the color being measured is turned off. The response time of a typical photodiode is extremely short, so the measuring sequence can be performed in a sufficiently short time that an-observer will not detect it (e.g. 10 ms). Measured light outputs for the colors are compared to desired outputs, which may be set by user controls, and changes to the power supply for the color blocks are made as necessary. Chromaticity is thus automatically controlled without regard to the factors which may cause it to change. The user inputs permit varying the desired chromaticity to either warm white (more red output) or cool white (more blue output).
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.