1. Field of the Invention
The present invention relates to an image capturing apparatus, a control method of the image capturing apparatus, and an image capturing system, and more specifically, to an image capturing apparatus having auto focus control function, a control method of the image capturing apparatus, and an image capturing system.
2. Description of the Related Art
Typical schemes of focus control methods for image capturing apparatuses include a contrast AF scheme and a phase difference AF scheme. The contrast AF scheme and the phase difference AF scheme are AF schemes widely used in video cameras and digital still cameras, with an image sensor being used as a focus detection sensor. In these focus control methods, focus detection results may contain errors due to various aberrations of an optical system. Various methods have been proposed to reduce such errors.
For example, Japanese Patent No. 5087077 discloses a method of calculating a correction value for correcting a focus detection result in accordance with a frequency band for evaluation of a signal used for focus detection. Regardless of the above-mentioned focus control methods, such a focus detection error occurs depending on, for example, a frequency band for evaluation of a focus control signal used in the contrast AF scheme or the phase difference AF scheme.
With the structure described in Japanese Patent No. 5087077, however, when the number of kinds of signals used for focus detection is larger, more correction values are needed. This requires more memory to store the correction values, leading to an increase in cost. Especially in the case of an image capturing apparatus having auto focus control function to which an interchangeable imaging lens unit can be attached, the imaging lens unit needs to store correction values corresponding to different focus detection functions or different focus detection methods, and the need for more memory leads to an increase in cost of the imaging lens unit.