Modification of a Beckman Spectrophotometer for Direct Measurements of Spectral Energy Distribution of Light Sources

A Beckman DK-2R spectroeflectometer has been modified for obtaining spectral energy distributions of various light sources in the spectral region between 300–2500 mμ. Measurements are made by comparing a test source to a standard source. By including in the circuitry a function generator, which introduces the known energy distribution of the standard source, direct reading of the energy distribution of the test source is obtained. The instrument has been successfully used to measure a variety of light sources, including tungsten lamps, fluorescent lamps, line sources, and natural daylight. It has enough response to measure also sources of intensity as low as one candlepower. Either relative or absolute energy data can be provided by the modified instrument.