Automatic focus adjustment apparatus and control method therefor

Patent metadata

Field	Value
Publication number	US-9742985-B2
Application number	US-201615069592-A
Country	US
Kind code	B2
Filing date	Mar 14, 2016
Priority date	Mar 19, 2015
Publication date	Aug 22, 2017
Grant date	Aug 22, 2017

Abstract

In an automatic focus adjustment apparatus, a setting unit sets, on an image sensor, a first range in which defocus information is detected using a phase difference detection and a second range in which a focus state is detected using a contrast detection. The second range is set so as to include the first range. In a case where the second range is detected by the contrast detection as being in an in-focus state, a control unit changes a control mode into a predetermined control mode in which the driving of the focus lens is limited according to the defocus information in the first range detected by the phase difference detection.

First claim

What is claimed is:

1. An automatic focus adjustment apparatus comprising:
an image sensor configured to generate an image signal by performing a photoelectric conversion on a light flux incident via an image pickup optical system including a focus lens;
a first focus detection unit configured to detect defocus information by a phase difference detection;
a second focus detection unit configured to detect a focus state based on the image signal;
a setting unit configured to set on the image sensor a first range in which the first focus detection unit detects the defocus information and a second range in which the second focus detection unit detects the focus state; and
a control unit configured to control driving the focus lens based on the defocus information detected by the first focus detection unit,
wherein the setting unit sets the second range such that the second range includes the first range, and
wherein, in a case where the focus state in the second range detected by the second focus detection unit is in an in-focus state, the control unit changes a control mode into a predetermined control mode in which the control unit limits the driving of the focus lens according to the defocus information in the first range detected by the first focus detection unit.

2. The automatic focus adjustment apparatus according to claim 1 , wherein the first focus detection unit detects the defocus information based on a phase difference between a pair of image signals generated at the image sensor.

3. The automatic focus adjustment apparatus according to claim 1 , wherein the second focus detection unit detects a focus state based on an evaluation value obtained using a predetermined frequency component of the image signal.

4. The automatic focus adjustment apparatus according to claim 1 ,
wherein the setting unit sets on the image sensor a third range in which the second focus detection unit detects a focus state, the third range is smaller than the second range, and
wherein the control unit changes a condition for switching the control mode to the predetermined control mode depending on whether the focus state in the third range detected by the second focus detection unit is an in-focus state.

5. The automatic focus adjustment apparatus according to claim 4 ,
wherein the defocus information includes an amount of defocus and a defocus direction,
wherein, in a case where the focus state in the third range detected by the second focus detection unit is not an in-focus state, the control unit determines whether the focus state in the second range is in an in-focus state, and
wherein, in a first case in which the focus state in the second range detected by the second focus detection unit is an in-focus state and the amount of defocus detected by the first focus detection unit is less than a first threshold value, the control unit changes the control mode to the predetermined control mode according to the detected defocus direction.

6. The automatic focus adjustment apparatus according to claim 5 ,
wherein, in a case in which the focus state in the third range detected by the second focus detection unit is an in-focus state and the amount of defocus detected by the first focus detection unit is less than a third threshold value, the control unit changes the control mode to the predetermined control mode according to the detected defocus direction, and
wherein the third threshold value is equal to or less than the first threshold value.

7. The automatic focus adjustment apparatus according to claim 1 ,
wherein the defocus information includes an amount of defocus and a defocus direction, and
wherein, in a second case in which the focus state in the second range detected by the second focus detection unit is an in-focus state and the amount of defocus detected by the first focus detection unit is equal to or greater than a second threshold value, the control unit changes the control mode to the predetermined control mode.

8. The automatic focus adjustment apparatus according to claim 7 , wherein, in the second case, the control unit performs the predetermined control mode only when the focus lens is not being driven.

9. The automatic focus adjustment apparatus according to claim 7 , wherein, until a second period of time elapses since the switching to the predetermined control mode, the control unit maintains the focus lens not to be driven.

10. The automatic focus adjustment apparatus according to claim 7 , wherein the second threshold value is changed depending on at least one of a depth of field and an image capture mode.

11. The automatic focus adjustment apparatus according to claim 10 , wherein the second threshold value is set such that the second threshold value decreases as a depth of field value decreases.

12. The automatic focus adjustment apparatus according to claim 10 , wherein when a moving image is taken, the second threshold value is set to be greater than is set when a still image is taken.

13. The automatic focus adjustment apparatus according to claim 1 ,
wherein the defocus information includes an amount of defocus and a defocus direction, and
wherein, in a first case in which the focus state in the second range detected by the second focus detection unit is an in-focus state and the amount of defocus detected by the first focus detection unit is less than a first threshold value, the control unit changes the control mode to the predetermined control mode according to the detected defocus direction.

14. The automatic focus adjustment apparatus according to claim 13 , wherein in the first case, the control unit performs the predetermined control mode only when the focus lens is being driven.

15. The automatic focus adjustment apparatus according to claim 13 ,
wherein, until a first period of time elapses since the switching to the predetermined control mode, the control unit limits the amount of driving the focus lens to a second driving amount less than a first driving amount set based on the amount of defocus detected by the first focus detection unit.

16. The automatic focus adjustment apparatus according to claim 15 , wherein the second driving amount is set based on an amount of defocus less by a predetermined amount or ratio than the amount of defocus detected by the first focus detection unit.

17. The automatic focus adjustment apparatus according to claim 13 , wherein in the first case, when the defocus direction detected by the first focus detection unit is a particular direction, the control unit switches the control mode to the predetermined control mode.

18. The automatic focus adjustment apparatus according to claim 17 , wherein the particular direction is a defocus direction detected in an immediately previous focus detection by the first focus detection unit.

19. The automatic focus adjustment apparatus according to claim 17 , wherein
the first focus detection unit includes a storage unit configured to store a history of the detected defocus direction, and
the control unit determines the particular direction depending on the history of the defocus direction stored in the storage unit.

20. The automatic focus adjustment apparatus according to claim 13 , wherein the first threshold value is changed depending on at least one of a depth of field and an image capture mode.

21. The automatic focus adjustment apparatus according to claim 20 , wherein the first threshold value is set such that the first threshold value increases as a depth of field value decreas

Assignees

• Canon Kk

Inventors

• Yokozeki Makoto

Classifications

• H04N23/672 Primary

  based on the phase difference signals · CPC title

• H04N23/673

  based on contrast or high frequency components of image signals, e.g. hill climbing method · CPC title

• G02B7/38

  measured at different points on the optical axis {, e.g. focussing on two or more planes and comparing image data} · CPC title

• G02B7/34 Primary

  using different areas in a pupil plane · CPC title

• G02B7/285

  including two or more different focus detection devices, e.g. both an active and a passive focus detecting device · CPC title