Focus adjusting apparatus, focus adjusting method, image capturing apparatus, and storage medium

1. A focus adjusting apparatus, comprising:

a tracking unit that detects a first area of a subject to be tracked, and reliability of a tracking position from an image signal output from an image sensor that captures a subject image formed on the image sensor by an optical system;

a focus detection unit that detects focus states of a plurality of focus detection areas based on the image signal that is output from the image sensor;

a determination unit that determines an in-focus area for which focus adjustment of the optical system is to be performed;

a prediction unit that predicts a focus state in next focus detection based on a history of focus states of the in-focus area detected by the focus detection unit; and

a selection unit that selects a second area from the plurality of focus detection areas,

wherein the determination unit determines the first area as the in-focus area in a case where a state in which the reliability is higher than a predetermined first threshold continues for a predetermined time period or longer, and determines the second area as the in-focus area in a case where the state does not continue for the predetermined time period.

2. The focus adjusting apparatus according to claim 1 , wherein the selection unit selects the second area from predetermined part of the plurality of focus detection areas.

3. The focus adjusting apparatus according to claim 1 , wherein, in a case where a difference between a focus state of the first area and the predicted focus state is within a predetermined first range, the determination unit determines the first area as the in-focus area regardless of the reliability.

4. The focus adjusting apparatus according to claim 1 , wherein, in a case where the reliability is higher than the first threshold and a difference between a focus state of the second area and the predicted focus state is not within a second range, the determination unit determines the first area as the in-focus area.

5. The focus adjusting apparatus according to claim 1 , wherein, in a case where the reliability is equal to or less than the first threshold and a difference between a focus state of the second area and the predicted focus state is within a second range, the determination unit determines the second area as the in-focus area.

6. The focus adjusting apparatus according to claim 1 , wherein, in a case where the reliability is equal to or less than the first threshold and a difference between a focus state of the second area and the predicted focus state is not within a second range, the determination unit determines the in-focus area determined last time as the in-focus area.

7. The focus adjusting apparatus according to claim 1 , wherein the predetermined time period is changed in accordance with at least one of the reliability and a difference between a focus state of the second area and the predicted focus state.

8. The focus adjusting apparatus according to claim 1 , further comprising:

a display unit that displays an image based on the image signal;

a setting unit that sets an area corresponding to the in-focus area determined by the determination unit and an area that satisfies a predetermined condition,

wherein the display unit superimposes a display that indicates the area set by the setting unit on the image.

9. The focus adjusting apparatus according to claim 8 , wherein the predetermined condition is that a difference between the focus state of each of the part of the focus detection areas and the focus state of an area corresponding to the in-focus area is smaller than a predetermined threshold.

10. The focus adjusting apparatus according to claim 8 , wherein the predetermined condition is that a difference between the focus state of an area corresponding to the in-focus area and a weighted focus state of each of the part of the focus detection areas is smaller than a predetermined threshold, wherein each weight is based on a distance from the in-focus area.

11. An image capturing apparatus, comprising:

an image sensor that outputs as image signal by capturing a subject image formed by an optical system; and

a focus adjusting apparatus that comprises:

a tracking unit that detects a first area of a subject to be tracked, and reliability of a tracking position from an image signal output from an image sensor that captures a subject image formed on the image sensor by an optical system;

a focus detection unit that detects focus states of a plurality of focus detection areas based on the image signal that is output from the image sensor;

a determination unit that determines an in-focus area for which focus adjustment of the optical system is to be performed;

a prediction unit that predicts a focus state in next focus detection based on a history of focus states of the in-focus area detected by the focus detection unit; and

a selection unit that selects a second area from the plurality of focus detection areas,

wherein the determination unit determines the first area as the in-focus area in a case where a state in which the reliability is higher than a predetermined first threshold continues for a predetermined time period or longer, and determines the second area as the in-focus area in a case where the state does not continue for the predetermined time period.

12. A focus adjusting method, comprising:

detecting a first area of a subject to be tracked, and reliability of a tracking position from an image signal output from an image sensor that captures a subject image formed on the image sensor by an optical system;

detecting focus states of a plurality of focus detection areas based on the image signal that is output from the image sensor;

determining an in-focus area for which focus adjustment of the optical system is to be performed;

predicting a focus state in next focus detection based on a history of focus states of the detected in-focus area; and

selecting a second area from the plurality of focus detection areas,

determining the first area as the in-focus area in a case where a state in which the reliability is higher than a predetermined first threshold continues for a predetermined time period or longer, and determining the second area as the in-focus area in a case where the state does not continue for the predetermined time period.

13. The focus adjusting method according to claim 12 , further comprising:

setting an area corresponding to the determined in-focus area and an area that satisfies a predetermined condition; and

displays an image based on the image signal, and superimposes a display that indicates the set area on the image.

14. A computer-readable storage medium having stored therein a program which is executable by a computer, the program having program codes for realizing the focus adjusting method that comprises:

detecting a first area of a subject to be tracked, and reliability of a tracking position from an image signal output from an image sensor that captures a subject image formed on the image sensor by an optical system;

detecting focus states of a plurality of focus detection areas based on the image signal that is output from the image sensor;

determining an in-focus area for which focus adjustment of the optical system is to be performed;

predicting a focus state in next focus detection based on a history of focus states of the detected in-focus area; and

selecting a second area from the plurality of focus detection areas,

determining the first area as the in-focus area in a case where a state in which the reliability is higher than a predetermined first threshold continues for a predetermined time period or longer, and determining the second area as the in-focus area in a case where the state does not continue for the predetermined time period.