| 摘要 |
Apparatus for detecting the color temperature of a source of light for use in, for example, a color television camera. First and second semiconductor photo-sensing elements are connected in series and are oppositely poled with respect to each other. Light of predetermined, respective colors having respectively different spectral characteristics is supplied to the first and second photo-sensing elements, for example, through different light filters. An output signal is derived from the opposite ends of the series circuit representing the color temperature of the light source. In a preferred embodiment, the output signal is produced by an operational amplifier having a pair of inputs, one of which being connected to one end of the series circuit, an output connected to the opposite end of the series circuit, and a resistance connected between the two inputs of the operational amplifier, the derived output signal being a voltage across the operational amplifier output and other input. In one application, the output voltage produced by the operational amplifier is supplied to a differential amplifier which, in turn, provides first and second voltages representing the relative intensities of the light received by the photo-sensing elements. The difference between these first and second voltages is combined with first and second color video signal components, respectively, such as color difference signals, so as to vary the levels of these respective color video signal components. The first and second voltages also are used to adjust the levels of the respective color video signal component outputs from the combining means so as to be substantially equal to the white balanced levels thereof at a predetermined color temperature. In another application, the voltage produced by the operational amplifier is supplied to the differential amplifier by yet another amplifier, and the differential amplifier includes a constant current source having a control input supplied with a color component voltage, such as the red color signal voltage VR or the blue color signal voltage VB. The differential amplifier has a single output for providing a white-balanced red or blue color signal voltage.
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