Abstract: An iris driving circuit, adapted to a color video camera, detects excessive intensity of radiation above a predetermined level from a white-colored subject so that an iris is controlled to optimize the function of auto white balance.

Abstract: A chrominance subcarrier generating circuit for adjusting output levels of a plurality of chrominance subcarriers having different phases to the optimum level is disclosed. A filter removes harmonic components from the square signals to extract only the sinusolidal subcarriers, a first terminal provides first chrominance subcarriers after blocking DC components, a phase-shifter shifts the phases of the chrominance subcarriers, another terminal provides second chrominance subcarriers after blocking the DC components, and a power source filter and an auxiliary power source filter for preventing the first and second chrominance subcarriers from influencing other power sources and for blocking the noise coming from other power sources. Levels of the first and second chrominance subcarriers can be set properly regardless of the characteristics of the transistors.

Abstract: An automatic optical filter displacing circuit for optimizing the white balance of video cameras is disclosed which comprises a buffer means; a sample and holder means for producing average values of the buffered luminance signals and for carrying out a sampling out of the average values; a first reference signal supply means; a first comparing means; a second reference signal supply means; a second comparing means; an optical filter control means; a trigger means for generating a white balance setting signal automatically; and a power supply means. The optical filters are automatically displaced so as to achieve the optimum state of the white balance by making judgements on the color temperature condition and the light amount condition of the illumination, and the electrical corrections are decided optimally depending on the illuminating conditions, thereby producing a good image quality.

Abstract: A noise reduction circuit for video contour emphasis signal including an amplification circuit for the contour signal, mean value detection circuit for the contour signal, a noise reduction level control circuit, positive and negative noise reduction circuit and output level control circuit, thereby eliminating the noise signal included in the contour signal and improving the signal to noise ratio.