Focusing position detecting device and focusing position detecting method

A focusing position detecting device as a part of an electronic device having an electronic imaging function comprising:

• first contrast evaluation value calculating unit configured to calculate contrast evaluation values from a plurality of image data items obtained by imaging a subject a multiple number of times at a set exposure time while moving a focus lens in an optical axis direction within a first search range;
• first focusing position calculating unit configured to calculate a first focusing position from focus positions at the time of imaging the subject a multiple number of times and the calculated contrast evaluation values in the first contrast evaluation value calculating unit;
• drive unit configured to drive the focus lens in the first focusing position;
• second contrast evaluation value calculating unit configured to calculate contrast evaluation values from a plurality of image data items obtained by imaging the subject a multiple number of times at the set exposure time in the first focusing position;
• time variation detecting unit configured to detect a time variation in a plurality of the contrast evaluation values calculated by the second contrast evaluation value calculating unit;
• determination unit configured to determine whether or not the contrast evaluation values are influenced by atmospheric fluctuation from the detection result of the time variation;
• exposure time setting unit configured to set an exposure time so as to be longer than the set exposure time in a case where it is determined that the contrast evaluation values are influenced by the atmospheric fluctuation;
• third contrast evaluation value calculating unit configured to calculate contrast evaluation values from a plurality of image data items obtained by imaging the subject a multiple number of times at the exposure time set by the exposure time setting unit while moving the focus lens within a second search range which includes the first focusing position and is narrower than the first search range in the optical axis direction in a case where it is determined that the contrast evaluation values are influenced by the atmospheric fluctuation;
• and
• second focusing position calculating unit configured to calculate a second focusing position from focus positions at the time of imaging the subject a multiple number of times and the calculated contrast evaluation values in the third contrast evaluation value calculating unit.

A focusing position detecting method executed by an electronic device having an electronic imaging function comprising a contrast evaluation value calculating step of calculating contrast evaluation values from a plurality of image data items obtained by imaging a subject a multiple number of times at a set exposure time while moving a focus lens in an optical axis direction within a search range, and a focusing position calculating step of calculating a focusing position from focus positions at the time of imaging the subject a multiple number of times and the calculated contrast evaluation values, the method comprising:

• a detection step of detecting atmospheric fluctuation;
• and
• an exposure time setting step of setting an exposure time in a case where the atmospheric fluctuation is detected so as to be longer than an exposure time in a case where the atmospheric fluctuation is not detected;
• wherein the atmospheric fluctuation is at least one selected from the group consisting of change in heat haze, change in wind and change in temperature.

A focusing position detecting method executed by an electronic device having an electronic imaging function comprising:

• a first contrast evaluation value calculating step of calculating contrast evaluation values from a plurality of image data items obtained by imaging a subject a multiple number of times at a set exposure time while moving a focus lens in an optical axis direction within a first search range;
• a first focusing position calculating step of calculating a first focusing position from focus positions at the time of imaging the subject a multiple number of times and the calculated contrast evaluation values in the first contrast evaluation value calculating step;
• a drive step of driving the focus lens in the first focusing position;
• a second contrast evaluation value calculating step of calculating contrast evaluation values from a plurality of image data items obtained by imaging the subject a multiple number of times at the set exposure time in the first focusing position;
• a time variation detecting step of detecting a time variation in a plurality of the contrast evaluation values calculated in the second contrast evaluation value calculating step;
• a determination step of determining whether or not the contrast evaluation values are influenced by atmospheric fluctuation from the detection result of the time variation;
• an exposure time setting step of setting an exposure time so as to be longer than the set exposure time in a case where it is determined that the contrast evaluation values are influenced by the atmospheric fluctuation;
• a third contrast evaluation value calculating step of calculating contrast evaluation values from a plurality of image data items obtained by imaging the subject a multiple number of times at the exposure time set in the exposure time setting step while moving the focus lens within a second search range which includes the first focusing position and is narrower than the first search range in the optical axis direction in a case where it is determined that the contrast evaluation values are influenced by the atmospheric fluctuation;
• and
• a second focusing position calculating step of calculating a second focusing position from focus positions at the time of imaging the subject a multiple number of times and the calculated contrast evaluation values in the third contrast evaluation value calculating step.