This work presents, summarizes and validates a fast, accurate and general measurement and modeling technique to obtain spectral near field data of LED systems in order to improve the optical design process of modern high quality LED systems. It requires only a minimum of goniophotometric near field measurements as well as no time-consuming angularly resolved spectral measurements. The procedure is named physically motivated basis spectra (PMBS) as its main assumption is that each piece of angularly and spatially varying spectral information can be described as the weighted sum of its physical basis spectra such as the individual semiconductors or a phosphor. Based on detailed spectral information regarding the goniophotometric measurement setup, the spectral model is obtained by solving a simple system of linear equations using the obtained near field measurements. The complete process is validated and applied to different state-of-the-art LED systems. The obtained results can be used directly in state-of-the-art ray tracers.
Xe excimer lamps are used as VUV source for industrial application like surface cleaning. To determine the VUV
efficiency of the lamp the radiant flux need to be known. Due to the difficulties of VUV measurements, it is often
determined by interpolation from a value of a fixed angle, which results in large uncertainties. Here a goniometric setup
is presented to measure the radiant flux of VUV sources like Xe excimer lamps which emit a narrow spectral band in the
VUV range between &lgr; = 147 nm and 200 nm with a peak at 172 nm and spectral lines in NIR. By the use of two
monochromators, we measure the spectral resolved radiant flux from 120 nm to 1000 nm. The measurement uncertainty
of 9.7 % is rather low for the VUV spectral range and depends mainly on the uncertainty of the used deuterium
calibration standard from PTB (7%). Due to the strong temperature dependence of the transmission edge of silica used
for the lamp vessel, the measurements are done in nitrogen atmosphere to ensure the convection cooling of the lamp. We
measured the radiance distribution curve and radiant flux of Xe excimer lamps and could show the angle dependence of
the spectrum. The measured correlation between the VUV band and the NIR lines gives us a better understanding of the
plasma kinetics, which is used to optimize the pulsed excitation of the lamp.
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