Abstract: White shading of an image signal is corrected by a white shading correction system which requires a small amount of memory. Rather than storing correction signals for an entire image frame for each possible condition of zoom lens position and iris opening degree, the present system stores correction signals for a single frame corresponding to a single condition where the zoom lens is at a medium position and the iris is at a medium opening degree. The present system also generates a set of correction factors corresponding to each possible condition of zoom lens position and iris opening degree. When the conditions of zoom lens position and iris opening change from their medium values, the correction signals used for correcting the image data picked up by the camera are modified by the appropriate correcting factor prior to performing correction of the picked-up image data.

Abstract: An apparatus for generating a carrier frequency suitable for frequency band conversion of a color signal in a digital color signal processing circuit of a video tape recorder includes an adder, an integrator and a memory device. The adder combines a first phase variation amount signal, which can be obtained with respect to a change in a horizontal sync signal, to a second phase variation amount signal, which can be obtained with respect to a change in a color burst signal. The integrator integrates the resultant phase variation amount signal, and generates a phase value signal. The memory, which in an exemplary case can be a read only memory (ROM), then provides a carrier signal corresponding to the phase value signal output by the integrator. Thus, the required carrier for digital processing of the color signal can be generated using a simpler structure., e.g., without the use of a multiplier and a band-pass filter.

Abstract: A color signal demodulation circuit demodulates a color signal in correspondence with different chrominance subcarrier frequencies. The input color signal is delayed by .pi./2 using a so-called Hilbert transformer and the carrier signal for use in the demodulation is generated from a carrier generator. The input color signal and the carrier signal are selectively multiplied and added so as to demodulate a color difference signal of the desired baseband, to thereby correspond to the chrominance subcarriers having different frequencies while simplifying the hardware. A method for demodulating the chrominance signal, which method is particularly adapted to the demodulation circuit is also detailed.