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Development of a Tunable LED-Based Colorimetric Source



Steven W. Brown, C Santana, George P. Eppeldauer


A novel, spectrally tunable light-source utilizing light emitting diodes (LED's) for radiometric, photometric, and colorimetric applications is described. The tunable source can simulate standard sources and can be used as a transfer sources and can be used as a transfer source to propagate photometric and color scales from calibrated reference instruments to field devices with minimal increase in uncertainty. In this prototype source, 40 LED's with 10 different spectral distributions were mounted onto a commercial integrating sphere. A voltage to current control circuit was designed and implemented, enabling independent control of the current sent to each set of 4 LED's. The LED's have been characterized for stability and dependence on drive current. The prototype source demonstrates the feasibility of development of a spectrally tunable LED source with up to 40 different LED's. Simulations demonstrate that such a source would be able to approximate standard light-source distributions over the visible spectral range - from 380 nm to 780 nm - with errors on the order of 0.5% to 2% or less. The tunable LED source can also simulate spectral distributions of special sources such as discharge lamps and display monitors. With this tunable source, a test instrument can be rapidly calibrated against a variety of different source distributions tailored to the anticipated uses of the artifact. Target uncertainties for the calibration of test artifacts are less than 2% in luminance and 0.002 in chromaticity for any source distribution.
Journal of Research (NIST JRES) -
107 No. 4


colorimetry, integrating sphere, light emitting diode, photometry, radiometry


Brown, S. , Santana, C. and Eppeldauer, G. (2002), Development of a Tunable LED-Based Colorimetric Source, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD (Accessed April 17, 2024)
Created August 1, 2002, Updated February 17, 2017