Patent ID: 8471949

Claim:
A focus-adjustment signal generating apparatus comprising: a filter configured to extract a high-frequency component at a specific frequency or higher from a luminance signal of an input video signal; a level comparator configured to compare an absolute value of the high-frequency component with a specific reference value, to output a first detection signal when the absolute value is equal to or larger than the reference value whereas to output a second detection signal when the absolute value is smaller than the reference value; an extender configured to extend a first output period from output start to output end during which the first detection signal is output to a second output period from output start to output end longer than the first output period by changing a first number of output times of the first detection signal to a second number of output times larger than the first number of output times based on an input period-setting signal, thereby outputting a third detection signal having the second output period thus extended; and a focus-adjustment signal generator configured to select a first chrominance difference signal indicating a specific color in response to the third detection signal and to consecutively output the selected first chrominance difference signal during the second output period thus extended whereas to select a second chrominance difference signal indicating an achromatic color in response to the second detection signal and to output the selected second chrominance difference signal, the output first or second chrominance difference signal being generated as a manual focus-adjustment signal.