New Method for Realizing a Luminous Flux Scale using an Integrating Sphere with an External Source
نویسنده
چکیده
A method is proposed to realize a luminous flux scale (lumens) using an integrating sphere with a known amount of flux introduced from an external source. The integrating sphere features an opening for a detector, a test lamp in its center, a baffle between the test lamp and the detector. A second opening is used to introduce flux from an external source, and is appropriately baffled from the test lamp. Flux from the external source is introduced into the sphere through a limiting aperture of known area. The flux entering the sphere is determined from knowledge of the illuminance on the aperture plane and the area of the aperture. The total flux from the test lamp is deduced by comparison to the flux from the external source. Theoretical analysis is first made by computer simulation based on a ray tracing technique. Several integrating sphere designs are analyzed under various conditions, and based on the results of the simulation, an integrating sphere 50 cm in diameter is built to conduct experiments. The characteristics of the sphere are measured and compared with the simulation results. The total luminous flux values of several miniature lamps measured with this method are found to agree within 0.5% with measurements using goniophotometric technique. This method can be applied also to realize a total spectral radiant flux scale.
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