A Quartz-bromine Lamp as a Secondary Standard of Spectral Irradiance

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  • 新しい分光放射照度標準用しゅう素電球

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The quartz-bromine lamp here described was designed as a secondary standard lamp of spectral irradiance (0.25-2.5μm). In order to obtain a desirable reproducibility of spectral irradiance, the lamp bulb having steatite blocks on both ends is united with a “U”-shaped steel holder, under which a rectangular steel plate is fixed. The front edge of the plate is polished and its center serves as the original point of measuring the distance along the normal to this plane.<BR>The lamps are classified into two types: One with clear bulb and the other with frosted bulb. The former lamps are selected for the smaller variation of the radiant intensity around the designated direction (less than 0. 25% within angles of 1. 5 degress), but the latter need no selection in this point. Both types are based on the commercial halogen lamps (JPD-5000) having coiled coil filaments and being operated horizontally. When operated at the rated voltage of 100 V, distribution temperature of the lamp is 3150±15 K, and the useful calibration life of 70 to 100 hours for 0. 5% change of radiant intensity may be expected, while the lamp current decreases about 0. 008 % per hour. The time recuired for aging varies from 10 to 50 hours.<BR>The spectral distribution of the lamp with clear bulb is compared with that of the full radiator at the same temperature as the distribution temperature of the lamp, and the ratios of the spectral distributions at each wavelength are normalized at the wavelengths of 460 and 660 nm. The coefficients thus obtained are used to estimate the spectral distribution of the lamp operated at a known distribution temperature.

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