Image-capturing system diagnostic device, image-capturing system diagnostic program product and image-capturing device for monitoring foreign matter

An image-capturing system diagnostic device comprising:

• an image acquisition unit that obtains an image;
• and
• a monitoring unit that monitors a quantity of foreign matter present in an optical path by generating defect information indicating a defect at pixels caused by the foreign matter in the optical path based upon the image obtained by the image acquisition unit and calculating an area ratio of defective pixels in the image based upon the defect information having been generated and issues a warning for a photographer if the area ratio of the defective pixels exceeds a predetermined value,
• wherein the monitoring unit
• calculates a relative ratio of a value indicated at a target pixel and an average of values at a plurality of pixels present in a predetermined range containing the target pixel for each of pixels constituting the image obtained by the image acquisition unit,
• generates the defect information indicating a defect in the image based upon the relative ratio and monitors the Quantity of foreign matter based upon the defect information.
• compares the relative ratio with a plurality of threshold values,
• calculates area ratios each of which corresponds to one of the plurality of threshold values and is based on pixels with relative ratios further deviating from 1 relative to one of the threshold values, and
• makes a decision as to whether or not an area ratio having been calculated exceeds a predetermined area ratio in correspondence to each of the plurality of threshold values.