Recently, light-emitting diode (LED) lighting systems have become popular due to their increased system performance.
LED lighting system performance is affected by heat; therefore, it is important to know the temperature of a target
surface or bulk medium in the LED system. In-situ temperature measurements of a surface or bulk medium using
intrusive methods cause measurement errors. Typically, thermocouples are used in these applications to measure the
temperatures of the various components in an LED system. This practice leads to significant errors, specifically when
measuring surfaces with high-luminous exitance.
In the experimental study presented in this paper, an infrared camera was used as an alternative to temperature probes in
measuring LED surfaces with high-luminous exitance. Infrared thermography is a promising method because it does not
respond to the visible radiation spectrum in the range of 0.38 to 0.78 micrometers. Usually, infrared thermography
equipment is designed to operate either in the 3 to 5 micrometer or the 7 to 14 micrometer wavelength bands. To
characterize the LED primary lens, the surface emissivity of the LED phosphor surface, the temperature dependence of
the surface emissivity, the temperature of the target surface compared to the surrounding temperature, the field of view
of the target, and the aim angle to the target surface need to be investigated, because these factors could contribute
towards experimental errors. In this study, the effects of the above-stated parameters on the accuracy of the measured
surface temperature were analyzed and reported.