Image capturing apparatus performing filtering process with variable cut-off frequency

An image capturing apparatus comprising:

• an optical system having distortion aberration characteristics for expanding a central part and compressing a peripheral part of an object to be photographed;
• an image sensor for photodetecting an optical image obtained through the optical system, converting the optical image to image signals, and outputting the image signals;
• an A/D converting device for converting each image signal output from the image sensor into a digital signal;
• a filtering device for performing a filtering process for cutting low-frequency signal components of the image signal which has been converted into the digital signal;
• a filter coefficient setting device for selecting and assigning:
• first filter coefficients for cutting the low-frequency signal components, which have frequencies equal to or lower than a first frequency, to an image area corresponding to the central part, and
• second filter coefficients for cutting the low-frequency signal components, which have frequencies equal to or lower than a second frequency which is higher than the first frequency, to an image area corresponding to the peripheral part, wherein the filter coefficient setting device provides the selected filter coefficients to the filtering device;
• an integration device for integrating each image signal which was subjected to the filtering process by the filtering device, so as to generate an evaluation value;
• an area dividing device for performing area division based on area data relating to divided areas formed by dividing an effective image area into smaller areas, wherein the area dividing device sets each divided area for executing the integral and generating the evaluation value, for the integration device;
• and
• a control device for controlling focusing of the optical system based on the evaluation value with respect to each divided area.