Automatic focusing apparatus and control method therefor

Patent metadata

Field	Value
Publication number	US-10162248-B2
Application number	US-201615074958-A
Country	US
Kind code	B2
Filing date	Mar 18, 2016
Priority date	Sep 16, 2008
Publication date	Dec 25, 2018
Grant date	Dec 25, 2018

Abstract

An automatic focusing apparatus detects presence or absence of change in a distance between an object and the automatic focusing apparatus while operating in an operation mode to continuously perform an adjustment of the position of a focus lens to focus on the object, and stops a movement of the focus lens if a change in the distance is not detected.

First claim

What is claimed is:

1. An imaging apparatus comprising:
an image sensor configured to capture an image of an object through a photographic system including a focus lens and output image data;
a scan unit configured to move the focus lens within a predetermined scan range, having a scan center position, defined by a scan-starting point and a scan-ending point;
a calculation unit configured to calculate a focus evaluation value based on the image data while the scan unit moves the focus lens, and to determine a maximal focus evaluation value based on the focus evaluation value;
a control unit configured to adjust the focus lens to a lens position where the maximal focus evaluation value was obtained; and
a setting unit configured to set a scan range for a next scan depending on whether a direction of a lens position where the maximal focus evaluation value was obtained in a previous scan to a scan center position of the scan range in the previous scan is the same as a direction of a lens position where the maximal focus evaluation value is obtained in a present scan to a scan center position of the scan range for the present scan, or not,
wherein, if the direction of the lens position where the maximal focus evaluation value was obtained in the previous scan to the scan center position of the scan range for the previous scan is not the same as the direction of the lens position where the maximal focus evaluation value is obtained in the present scan to the scan center position of the scan range for the present scan, the scan range for the next scan is set without using a prediction calculation.

2. The imaging apparatus according to claim 1 , wherein, if the direction of the lens position where the maximal focus evaluation value was obtained in the previous scan to the scan center position of the scan range for the previous scan is the same as the direction of the lens position where the maximal focus evaluation value is obtained in the present scan to the scan center position of the scan range for the present scan, the scan range for the next scan is set based on a prediction calculation.

3. The imaging apparatus according to claim 1 , wherein, if the direction of the lens position where the maximal focus evaluation value was obtained in the previous scan to the scan center position of the scan range for the previous scan is not the same as the direction of the lens position where the maximal focus evaluation value is obtained in the present scan to the scan center position of the scan range for the present scan, the scan range for a next scan is set so that the scan center position for the next scan coincides with a lens position where the maximal focus evaluation value is obtained in the present scan.

4. The imaging apparatus according to claim 1 , wherein the scan unit is configured to move the focus lens in a one-way direction from the scan-starting point to the scan-ending point.

5. The imaging apparatus according to claim 1 , wherein the scan unit is configured to obtain a plurality of focus evaluation values including the maximal focus evaluation value by moving the focus lens for one-way scanning at a predetermined range, including the scan center position, defined by the scan-starting point and the scan-ending point, and the predetermined range is narrower than a movement range of the focus lens.

6. The imaging apparatus according to claim 1 , wherein an AF operation by the control unit with the scan unit is not a hill-climbing AF operation.

7. The imaging apparatus according to claim 1 , wherein the prediction calculation is based on the lens positions corresponding to each of a plurality of the maximal focus evaluation values.

8. A method for controlling an imaging apparatus, comprising:
capturing an image of an object through a photographic system including a focus lens and outputting image data;
moving the focus lens within a predetermined scan range, having a scan center position, defined by a scan-starting point and a scan-ending point;
calculating a focus evaluation value based on the image data while moving the focus lens, and determining a maximal focus evaluation value based on the focus evaluation value;
adjusting the focus lens to a lens position where the maximal focus evaluation value was obtained; and
setting a scan range for a next scan depending on whether a direction of a lens position where the maximal focus evaluation value was obtained in a previous scan to a scan center position of previous scan is the same as a direction of a lens position corresponding to the maximal focus evaluation value obtained in a present scan to a scan center position of the present scan, or not,
wherein, if the direction of the lens position where the maximal focus evaluation value was obtained in the previous scan to the scan center position of the scan range for the previous scan is not the same as the direction of the lens position where the maximal focus evaluation value is obtained in the present scan to the scan center position of the scan range for the present scan, the scan range for the next scan is set without using a prediction calculation.

9. The method according to claim 8 , wherein, if the direction of the lens position where the maximal focus evaluation value was obtained in the previous scan to the scan center position of the scan range for the previous scan is the same as the direction of the lens position where the maximal focus evaluation value is obtained in the present scan to the scan center position for the present scan, the scan range for the next scan is set based on a prediction calculation.

10. The method according to claim 8 , wherein, if the direction of the lens position where the maximal focus evaluation value was obtained in the previous scan to the scan center position of the scan range for the previous scan is not the same as the direction of the lens position where the maximal focus evaluation value is obtained in the present scan to the scan center position of the scan range for the present scan, a scan range for a next scan is set so that the scan center position for the next scan coincides with a lens position where the maximal focus evaluation value is obtained in the present scan.

11. An imaging apparatus comprising:
an image sensor configured to capture an image of an object through a photographic system including a focus lens and output image data;
a scan unit configured to move the focus lens within a predetermined scan range, having a scan center position, defined by a scan-starting point and a scan-ending point;
a calculation unit configured to calculate a focus evaluation value based on the image data while the scan unit moves the focus lens, and to determine a maximal focus evaluation value based on the focus evaluation value;
a control unit configured to adjust the focus lens to a lens position where the maximal focus evaluation value was obtained; and
a setting unit configured to set a scan range for a (N+1)st scan depending on whether a direction of a lens position where the maximal focus evaluation value was obtained in the (N−1)st scan to a scan center position of the scan range for the (N−1)st scan is the same as the direction of a lens position where the maximal focus evaluation value obtained in a Nth scan to the scan center position of the scan range for the Nth scan, or not, wherein N is natural number
wherein, if the direction of the lens position where the maximal focus evaluation value was obtained in the (N−1)st scan to the scan center position of the scan range for the (N−1)st scan is not the same as the direction of the lens position where the maximal focus evaluation value is obtained in the Nth scan to the scan center positio

Assignees

• Canon Kk

Inventors

• Uenishi Masaaki

Classifications

• H04N23/631

  Graphical user interfaces [GUI] specially adapted for controlling image capture or setting capture parameters · CPC title

• H04N23/61

  based on recognised objects · CPC title

• H04N23/673

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

• H04N23/634

  Warning indications · CPC title

• G03B13/36 Primary

  Autofocus systems · CPC title