Focal point adjusting apparatus, image-taking apparatus, interchangeable lens, conversion coefficient calibrating method, and conversion coefficient calibrating program

A conversion coefficient calibration method, comprising:

• photoelectrically converting at least a pair of optical images and outputs at least a pair of image signals;
• detecting a phase difference between the image signals;
• carrying out the conversion of the phase difference into a defocus amount by using the conversion coefficient;
• moving the focal point position based on the defocus amount that is the result of the conversion;
• and
• calibrating the conversion coefficient according to the result of moving the focal point position.

A non-transitory computer readable storage medium that stores a conversion coefficient calibration program that causes a computer of a focal point adjusting apparatus, which is provided with a photoelectric converting unit that photoelectrically converts at least a pair of optical images and outputs at least a pair of image signals, to function as:

• a phase difference detecting unit that detects a phase difference between the pair of image signals that are output by the photoelectric conversion unit;
• a conversion unit that carries out the conversion of a phase difference that is detected by the phase difference detecting unit into a defocus amount by using a conversion coefficient;
• a focal point moving unit that moves the focal point position based on the defocus amount resulting from the conversion by the conversion unit;
• and
• a calibrating unit that calibrates the conversion coefficient depending on the result of the focal point moving unit moving the focal point position.