Evaluation of calibration methods of a photometer measuring maritime light-emitting diode buoy lanterns

Erkki Ikonen Helsinki University of Technology Metrology Research Institute P.O. Box 3000 FIN-02015 HUT Finland Abstract. A photometer used for on-line product testing of light-emitting diode (LED) buoy lanterns is calibrated for illuminance responsivity using two different methods. The first method is based on absolute calibration of the photometer with the CIE standard illuminant A light source, combined with spectral correction factors (SCFs) calculated from the measured spectral responsivity of the photometer and relative spectra of the LED lanterns. The second method is based on direct comparison with a characterized reference photometer using the LED lanterns as light sources. Comparison of the resulting correction factors shows that both methods agree within 1%. However, the second method includes geometrical aspects and LED characteristics that caused problems. These problems are discussed and the reasons for recommending the first method are given. © 2004 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.1628245]