20 October 1998 Novel method to correct inaccuracies of photometer heads for the measurement of LEDs
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LED's are radiators with a spectrally narrow emission band generally less than 50 nm. Compared to broadband light sources, like lamps, their spectral power distribution can be classified as quasi-monochromatic. Photometer heads integrate the spectral emission of a light source for the whole visible spectral range, this generally averages out a great part of the error caused by the local spectral mismatch of the V((lambda) ) detector. On the contrary, if LED's are measured this local mismatch error appears entirely in the measurement results. Measuring red LED's with a photometer head of f1' <3% the absolute error can be even greater than 5%. The same head produces for commercial broadband light sources absolute errors less than 0.8% (in many cases less than 0.3%). Concerning quality industrial measurements this level of high error is not acceptable. A simple method will be shown how to increase the measurement accuracy of existing photometer heads. A computer simulation using generated and real LED spectral power distributions as well as spectral responsivity curves of a large number of real photometer heads took place. The results show that this method provides much higher absolute accuracy than the classical one.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Gyorgy Czibula, Janos P. Makai, "Novel method to correct inaccuracies of photometer heads for the measurement of LEDs", Proc. SPIE 3428, Illumination and Source Engineering, (20 October 1998); doi: 10.1117/12.327955; https://doi.org/10.1117/12.327955

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