Blackbody standard source

Blackbody radiation sources are accurate radiant energy standards of known flux and spectral distribulion. They are used for calibrating other infrared sources, detectors, and optical systems. The radiating properties of a blackbody source are described by Planck s law. Energy distribution... 

One method of standardizing illumination is to consider it relative to the radiation released by an object called a blackbody radiator. Blackbody radiation correlates with the spectral emission profile of a perfect blackbody radiation source when it is heated to a given temperature. The term "white hot" is taken in the same vein If an object such as an iron rod is heated sufficiently, it glows red, then yellow, and then, at the hottest, white to blue. When light has the same spectral spread as a blackbody emitter at a given temperature, tiie light is said to have that temperature. Here, "temperature" is a descriptor, but it... 

Relative state populations (NvJ or Nv) are derived from the observed spectrum in two stages. First, the spectrometer-detector unit must be calibrated with a standard blackbody source to allow for changes in sensitivity with wavelength. Then the corrected relative intensities are converted to the NvJ (or Nv) using values of the spontaneous emission coefficients. This procedure is quite simple when individual rotational lines can be resolved [101, 102]. Karl et al. have described a computational technique for analyzing the overlapped first overtone (Av = 1) spectra of CO [261] and NO [262] when the rotational distribution is known to be equilibrated, and Hancock and Smith [256] have extended this method. 

By definition, photometers do not respond to radiation in the infrared or the ultraviolet (Fig. 4-4a). They are light meters in the sense that they mimic human vision that is, they respond to photons in the visible region, similar to the light meter on a camera. A candle is a unit of luminous intensity, originally based on a standard candle or lamp. The current international unit is called a candela (sometimes still referred to as a candle ), which was previously defined as the total light intensity of 1.67 mm2 of a blackbody radiator (one that radiates maximally) at the melting temperature of pure platinum (2042 K). In 1979 the candela was redefined as the luminous intensity of a monochromatic source with a frequency of 5.40 x 1014 cycles s-1 (A, of 555 nm) emitting 0.01840 Js-1 or 0.01840 W (1.464 mW steradian-1, where W is the abbreviation for watt and steradian... 

Other sources are incandescent electric lamps (tungsten), the Welsbach mantle, hot glass, and the quartz-jacketed high-pressure mercury arc. The tungsten ribbon filament lamp makes a good secondary standard (compared to a primary blackbody) in the near... 

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