Abstract: A measurement apparatus for measuring and evaluating the latent photoluminescence present in a radio photoluminescent (RPL) glass which has been irradiated by gamma or x-ray radiation. The latent photoluminescence is measured by irradiating the glass by ultraviolet light and by measuring the resulting photoluminescence that emanates from the glass. In addition to the conventional measurement components which include one measurment branch for measuring the photoluminescence emitted from the glass and a second measurement branch for measuring the magnitude of the light emitted from the ultraviolet source there is provided an auxiliary common light source, the light of which is coupled, via a an optical beam splitter, to the first and second measurement branches. By using a single, common auxiliary light source, measurement inaccuracies that otherwise result from dark currents and parameter drifting in the first and second measurement systems are factored out.