Known as a conventional quantum-yield measurement device is a technique which irradiates a sample such as a light-emitting material with pumping light, employs an integrating sphere to cause therein multiple reflections of a fluorescence emitted from the sample, and detects thus reflected light, so as to measure a quantum yield (ratio of “the number of photons of the fluorescence emitted from the light-emitting material” to “the number of photons of the pumping light absorbed by the light-emitting material”) of the sample (see, for example, Patent Literatures 1 to 3).
When the sample is optically absorptive with respect to the fluorescent component in such a technique, there is a case where a part of the fluorescence is absorbed by the sample (which phenomenon will be referred to as “reabsorption” hereinafter). In such a case, the number of photons will be calculated smaller than the true number (i.e., the number of photons of the fluorescence actually emitted from the light-emitting material). It has therefore been proposed to use a fluorometer separately to measure the intensity of a fluorescence emitted from the sample in a state generating no reabsorption and correct according thereto the number of photons of the former fluorescence, so as to determine the quantum yield (see, for example, Non Patent Literature 1).