The sensitivity of photodetectors (vidicon type tubes with Se+Sb2S3, Sb2S3, and PbO + PbS phototargets), used in applied TV systems, is estimated. The sensitivities of these photodetectors rated in photometric units (lux) show differences of three orders of magnitude, whereas in radiant units (Wcm-2), the sensitivities of these photodetectors differ only several times. This effect results from the fact that the spectral characteristics of the sensitivities of the investigated photodetectors in the region from 0.38 to 0.67 µm (the region of the measurement of illuminance that changes in photometric units) differ significantly. The amount of radiation (in radiant units) required for photodetectors with different types of phototargets to generate the same output signal appears practically the same.
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