LED illumination device and calibration method for accurately characterizing the emission LEDs and photodetector(s) included within the LED illumination device
First Claim
1. A method for calibrating an illumination device comprising at least a first emission light emitting diode (LED) and a photodetector, the method comprising:
- subjecting the illumination device to a first ambient temperature;
successively applying a plurality of different drive currents to the first emission LED to produce illumination at different levels of brightness;
obtaining wavelength and intensity measurement values for the illumination produced by the first emission LED at each of the different drive currents;
measuring a forward voltage developed across the first emission LED by applying a non-operative drive current to the first emission LED before or after each of the different drive currents is applied to the first emission LED; and
storing the forward voltage measurements and at least a subset of the wavelength and intensity measurements within a storage medium of the illumination device to characterize the first emission LED at the first ambient temperature.
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Abstract
An illumination device and method is provided herein for calibrating individual LEDs and photodetector(s) included within the illumination device, so as to obtain a desired luminous flux and a desired chromaticity of the device over time as the LEDs age. Specifically, a calibration method is provided herein for characterizing each emission LED and each photodetector separately. The wavelength and intensity of the illumination produced by each emission LED is accurately characterized over a plurality of different drive currents and ambient temperatures, and at least a subset of the wavelength and intensity measurement values are stored with a storage medium of the illumination device for each emission LED. The responsivity of the photodetector is accurately characterized over emitter wavelength and photodetector junction temperature, and results of said characterization are stored with the storage medium.
288 Citations
23 Claims
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1. A method for calibrating an illumination device comprising at least a first emission light emitting diode (LED) and a photodetector, the method comprising:
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subjecting the illumination device to a first ambient temperature; successively applying a plurality of different drive currents to the first emission LED to produce illumination at different levels of brightness; obtaining wavelength and intensity measurement values for the illumination produced by the first emission LED at each of the different drive currents; measuring a forward voltage developed across the first emission LED by applying a non-operative drive current to the first emission LED before or after each of the different drive currents is applied to the first emission LED; and storing the forward voltage measurements and at least a subset of the wavelength and intensity measurements within a storage medium of the illumination device to characterize the first emission LED at the first ambient temperature. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An illumination device, comprising:
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a plurality of emission light emitting diodes (LEDs) configured to produce illumination for the illumination device; an LED driver and receiver circuit coupled to the plurality of emission LEDs and configured for successively applying a plurality of different drive currents to each of the emission LEDs, one emission LED at a time, to produce illumination at different levels of brightness; an interface configured for receiving wavelength and intensity values, which are measured by an external calibration tool upon receiving the illumination produced by each of the emission LEDs at each of the plurality of different drive currents; and a storage medium configured for storing at least a subset of the wavelength and intensity values obtained for each of the emission LEDs within a table of calibration values. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification