Description

There are two kinds of luminescent materials widely used in industry, differing only in the locations of their excitation and emission wavelength regions. The first, which is mainly considered in this report, are the chromatic luminescent materials used for safety and signal applications. These materials are generally excited by absorption of radiation in the ultraviolet and short-wavelength visible region. The second type, containing fluorescent whitening agents (FWAs), absorbs in the ultraviolet and emits in the short-wavelength visible region, otherwise the two types are very similar. 

The most widely used type of instrumentation for measuring specimens of these luminescent materials is the one-monochromator spectrophotometer, with the viewing beam. The large majority of these instruments in the field have integrating-sphere geometry. 

This Technical Report describes an intercomparison of measurements of the (total) spectral radiance factor (SRF) of luminescent materials. Seven luminescent specimens were provided as painted panels: two were white containing FWAs and five were chromatic (green, yellow, two orange, red). 

The SRFs were to be measured with direct specimen illumination by a source simulating CIE D65. The SRFs that would have been obtained under D65 illuminations were to be calculated by a method from among those previously studied by the committee. 

The report reviews the nature of the problem producing systematic errors in the measurement and possibilities for correcting the measurements results. 

From the performed investigation described in detail, the committee concluded that the measurement and calculation of the SRFs of luminescent materials can be made, on various one-monochromator instruments in different laboratories, to within an average CIELAB color difference of about 2,6 units from the mean results, with a range among specimens from 1,9 to 3,4 units, and a range among data sets from 1,5 to 4,2 units. Similar orders of magnitude are found if one laboratory is selected as the reference and the color differences are calculated relative to it. The range of maximum SRFs among samples is, however, quite large, varying from 11,4% to 33,6%. These results include correction for integrating-sphere-efficiency effects where this geometry was used. 

The conclusion drawn from the intercomparison and the evaluation of the different data reduction and correction procedures described in the literature is that no officially agreed CIE recommendation should be formulated at this time. The report has been presentedfor study and use. The readers will find, however, a number of methods in this publication, by the application of which their measurement results can be made more accurate. 

The publication contains 68 pages and 29 tables.

Description

In CIE 41-1978 a difference was clearly shown to exist between the luminous efficiency function of the CIE, V(lambda), and the function obtained by the direct heterochromatic brightness matching method, the efficiency of the latter being much higher than that of the former at both long and short wavelengths when both functions were normalized at 570 nm. 

This Technical Report summarizes spectral luminous efficiency functions based on heterochromatic brightness matching for point sources, 2° and 10° fields. Their averaged functions are derived with the intention that they be used to evaluate the luminous efficiency for the brightness of monochromatic lights. These functions could be used as the basis for further work to evaluate light sources with compound spectra. 

The spectral luminous efficiency function for a point source may be adequately represented by the Judd modified V(lambda) function. 

The spectral luminous efficiency functions for the brightness of a 2° field and a 10° field at photopic levels are different from the CIE V(lambda) function and are tabulated in the Technical Report. These functions should be used only to evaluate the luminous efficiencies of monochromatic light sources in terms of their brightnesses. Further work utilizing these functions is required to evaluate lights with compound spectra with allowance for additivity failure. 

CIE 75-1988 is a Technical Report written in Englishi with a short summary in English, French and German. It consists of 20 pages with 6 figures and 8 tables.