Focus-adjustment signal generating apparatus and method, and imaging apparatus and method, with manual focus adjustments

1. An imaging apparatus comprising:

a video signal generator configured to take an image of an object and generate a video signal carrying the image;

a filter configured to extract a high frequency component at a specific frequency or higher from a luminance signal of the video signal;

a 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 a second detection signal when the absolute value is smaller than the reference value;

a selector configured to select a first chrominance difference signal indicating a specific color in response to the first detection signal whereas a second chrominance difference signal indicating an achromatic color in response to the second detection signal, the first or the second chrominance difference signal being output as a focus-adjustment signal;

a down converter configured to down-convert the focus-adjustment signal by decreasing at least either the number of lines in a vertical direction or the number of pixels in a horizontal direction of the focus-adjustment signal;

a display configured to display an image of the object with the specific color at an edge portion of the image;

a peak detector configured to detect a peak level of the luminance signal;

a block-average calculator configured to calculate an average of the peak level in blocks of the image; and

an arithmetic unit configured to perform a specific operation to the peak level and the average to obtain the reference value.

2. The imaging apparatus according to claim 1 further comprising an iris mechanism configured to control an amount of an incident light of the object based on the peak level.

3. An imaging method comprising the steps of:

taking an image of an object and generating a video signal carrying the image;

extracting a high-frequency component at a specific frequency or higher from a luminance signal of the input video signal;

comparing 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 a second detection signal when the absolute value is smaller than the reference value;

selecting a first chrominance difference signal indicating a specific color in response to the first detection signal, whereas a second chrominance difference signal indicating an achromatic color in response to the second detection signal, the first or the second chrominance difference signal being output as a focus-adjustment signal;

down-converting the focus-adjustment signal by decreasing at least either the number of lines in a vertical direction or the number of pixels in a horizontal direction of the focus-adjustment signal;

displaying an image of the object with the specific color at an edge portion of the image;

detecting a peak level of the luminance signal;

calculating an average of the peak level in blocks of the image; and

performing a specific operation to the peak level and the average to obtain the reference value.

4. The imaging method according to claim 3 further comprising the step of controlling an amount of an incident light of the object based on the peak level.