Focus adjustment device and focus adjustment method

Patent metadata

Field	Value
Publication number	US-10051174-B2
Application number	US-201715407115-A
Country	US
Kind code	B2
Filing date	Jan 16, 2017
Priority date	Jan 18, 2016
Publication date	Aug 14, 2018
Grant date	Aug 14, 2018

Abstract

A direction judgment unit calculates a first evaluation value based on an image signal of a first focus detection region among focus detection regions to judge a drive direction of a focus lens to be in focus and calculates a second evaluation value based on an image signal of at least one second focus detection region smaller than the first region, the focus detection regions being at least partly the same and being different in size. A control unit determines whether a change of the second evaluation value is a monotonous change when the focus lens is slightly driven a first number of times in a first direction judged on the basis of the first evaluation value and the focus lens is slightly driven a second number of times smaller than the first number of times in a second direction opposite to the first direction, and the control unit performs focus adjustment on the basis of the second evaluation value when the change of the second evaluation value is not a monotonous change.

First claim

What is claimed is:

1. A focus adjustment device which includes an imager to receive a light flux passing through an imaging lens including a focus lens and then generate an image signal and which performs focus adjustment on the basis of the image signal, the focus adjustment device comprising:
a focus detection region setting unit which sets focus detection regions in a region of the imager where the light flux is received, the focus detection regions being at least partly the same and being different in size;
a direction judgment unit which calculates a first evaluation value based on an image signal of a first focus detection region among the focus detection regions to judge a drive direction of the focus lens to be in focus, and calculates a second evaluation value based on an image signal of at least one second focus detection region smaller than the first focus detection region among the focus detection regions to judge a drive direction of the focus lens to be in focus; and
a control unit which controls a focus adjustment operation on the basis of the drive direction judged by the direction judgment unit,
wherein the control unit determines whether a change of the second evaluation value is a monotonous change when the focus lens is slightly driven a first number of times in a first direction judged on the basis of the first evaluation value and the focus lens is slightly driven a second number of times smaller than the first number of times in a second direction opposite to the first direction, and the control unit performs focus adjustment on the basis of the second evaluation value when the change of the second evaluation value is not a monotonous change, and
the first number of times is larger than or equal to 2.

2. The focus adjustment device according to claim 1 , wherein the direction judgment unit judges a drive direction of the focus lens on the basis of each of the second evaluation values calculated for each of the second focus detection regions, and
the control unit performs focus adjustment on the basis of the second evaluation value when the number of drive directions indicating a near direction is equal to or more than a predetermined number among the drive directions judged by the respective second evaluation values.

3. The focus adjustment device according to claim 1 , wherein when the first direction is a far direction, the control unit slightly drives the focus lens twice in the far direction, and then slightly drives the focus lens once in a near direction which is the second direction.

4. The focus adjustment device according to claim 1 , wherein when the first direction is a near direction, the control unit slightly drives the focus lens more than once in the near direction and at the same time causes the direction judgment unit to judge the drive direction, and the control unit slightly drives the focus lens once in a far direction which is the second direction after the drive direction judged by the direction judgment unit changes from the near direction to the far direction.

5. The focus adjustment device according to claim 1 , wherein a drive amount of the focus lens in the second direction is greater than a drive amount of the focus lens in the first direction.

6. The focus adjustment device according to claim 1 , further comprising a subject condition detection unit which detects a change in a subject condition on the basis of a difference between contrasts that are calculated based on image signals acquired at different timings, or a motion vector calculated based on the image signals acquired at different timings,
wherein, when the subject condition detection unit detects the change in the subject condition on the basis of a change of contrast or a change of a motion vector based on the image signal from the imager, the control unit determines whether the change of the second evaluation value is a monotonous change, and performs the focus adjustment on the basis of the second evaluation value when the change of the second evaluation value is not a monotonous change.

7. The focus adjustment device according to claim 1 , further comprising a posture change determination unit which includes a circuit for detecting an angular velocity with a gyro sensor and acquires information regarding a posture of the focus adjustment device to determine whether or not there is a posture change on the basis of the detected angular velocity,
when the posture change determination unit detects a panning movement or a tilting movement of the focus adjustment device, the control unit determines whether a change of the second evaluation value is a monotonous change, and performs the focus adjustment on the basis of the second evaluation value when the change of the second evaluation value is not a monotonous change.

8. The focus adjustment device according to claim 1 , wherein the control unit performs focus adjustment on the basis of the first evaluation value when a change of the second evaluation value is a monotonous change.

9. A focus adjustment device which includes an imager to receive a light flux passing through an imaging lens including a focus lens and then generate an image signal and which performs focus adjustment on the basis of the image signal, the focus adjustment device comprising:
a focus detection region setting unit which sets focus detection regions in a region of the imager where the light flux is received, the focus detection regions being at least partly the same and being different in size;
a direction judgment unit which calculates a first evaluation value based on an image signal of a first focus detection region among the focus detection regions to judge a drive direction of the focus lens to be in focus, and calculates a second evaluation value based on an image signal of at least one second focus detection region smaller than the first focus detection region among the focus detection regions to judge a drive direction of the focus lens to be in focus; and
a control unit which controls a focus adjustment operation on the basis of the direction judged by the direction judgment unit,
wherein the control unit determines whether a far-and-near mixing subject is present from a change of the second evaluation value when the focus lens is slightly driven a first number of times in a first direction judged on the basis of the first evaluation value and the focus lens is slightly driven a second number of times smaller than the first number of times in a second direction opposite to the first direction, and the control unit performs focus adjustment on the basis of the second evaluation value when the far-and-near mixing subject is present, and
the first number of times is larger than or equal to 2.

10. The focus adjustment device according to claim 9 , wherein when the first direction is a far direction, the control unit slightly drives the focus lens twice in the far direction, and then slightly drives the focus lens once in a near direction which is the second direction.

11. The focus adjustment device according to claim 9 , wherein when the first direction is a near direction, the control unit slightly drives the focus lens more than once in the near direction and at the same time causes the direction judgment unit to judge the drive direction, and the control unit slightly drives the focus lens once in a far direction which is the second direction after the drive direction judged by the direction judgment unit changes from the near direction to the far direction.

12. The focus adjustment device according to claim 9 , wherein a drive amount of the focus lens in the second direction is greater than a drive amount of the focus lens in the fi

Assignees

• Olympus Corp

Inventors

• Miyazawa Shingo
• Ikeda Makoto

Classifications

• H04N23/673 Primary

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

• H04N23/73

  by influencing the exposure time · CPC title

• G02B7/28 Primary

  Systems for automatic generation of focusing signals · 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

• G02B7/09

  adapted for automatic focusing or varying magnification · CPC title