Light Emitting Diodes (LEDs) are unique light sources differing greatly from traditional lamps in terms of physical size, flux level, spectrum and spatial distribution. The transfer of photometric scales from luminous intensity standard lamps to LEDs is not trivial, and large discrepancies among companies have been reported. The National Institute of Standards and Technology (NIST) has established a capability for calibrating the averaged LED intensity of LEDs using the detector-based method. The calibration service of illuminance responsivity available for LED photometers has a typical overall uncertainty of 0.70 % for Condition A and 0.90 % for Condition B. The calibration service available for averaged LED intensity typically has an overall expanded uncertainty (k=2) of 0.8 to 3 % for LEDs depending on the LED characteristics. In support of the luminous intensity and the total luminous flux measurements of LEDs, a reference spectroradiometer for colorimetry of LEDs has been built and characterized for uncertainties in color measurements. The final uncertainty budget for the NIST spectroradiometer is in progress.
Citation: IEEE Internet Computing
Pub Type: Journals
average LED intensity, calibration standard, led, luminous intensity