Source: {"pile_set_name": "USPTO Backgrounds"}

1. Field of the Invention
The present invention relates to an image pickup apparatus having a function for correcting an in-focus position detected by a phase difference AF (autofocus) method or the like.
2. Description of the Related Art
In the related art, in a single lens reflex camera which is arranged to attain an in-focused state by the phase difference AF, there is a case where in association with long-time use of the camera, a position which is recognized as an in-focus position is changed due to long-time use of each of a lens and a camera body and an in-focus precision deteriorates to a level lower than an initial precision. In the case of the lens, a case where while the lens is driven to a correct in-focus position, a lens stop position may be shifted from the correct position due to a mechanical deterioration caused by long-time use of a camera is considered. In the case of the camera body, there is considered a case where a mirror which is used in a phase difference detection method is driven many times so that an angle of the mirror is gradually changed and this causes change of an angle at which incident object light is guided to an AF sensor so that a position shifted from the correct in-focus position is recognized as an in-focus position. In the foregoing case, a unit for shifting the in-focus position to an original state without allowing the user to bring the camera to a service center has been installed in a recent image pickup apparatus.
In the detection of the in-focus position by the phase difference AF, there is a case where the correct in-focus position cannot be detected by an influence by colors, types, and the like of a light source and a photographing object. If such a problem occurs, such a technique that the detected in-focus position is corrected by the phase difference AF in accordance with an environment where the camera is used is considered. At this time, in a construction in which there are a plurality of focus adjustment areas (AF frames) for the phase difference AF, there is a case where the correction is necessary every AF frame or the like. However, if the number of portions to be corrected increases, there raises an actual problem such that it is difficult for a user to spend time to make individual correction each time the correction is necessary. Therefore, the user wants to correct in accordance with the AF frame which the user wants to use by himself. The Japanese Patent Application Laid-Open No. 2000-292684 discloses a function (AF calibration) which can automatically correct the in-focus position of the phase difference AF by using a contrast detection method. A correction value can be held every focal length.
However, in the technique disclosed in the above patent literature, in the case where there are a plurality of AF frames for the phase difference AF, there is not a control technique about how to select the AF frame which is used for correction of the in-focus position by the phase difference AF when a limitation processing of a selection of the AF frames is executed at the time of photographing.