Imaging apparatus and control method

• US 8,195,042 B2
• Filed: 09/16/2009
• Issued: 06/05/2012
• Est. Priority Date: 09/16/2008
• Status: Expired

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kimoto, Satoshi
• Primary Examiner(s): Fuller, Rodney
• Assistant Examiner(s): Chang, Fang-Chi
• Application Number:
  US12/560,552
• Publication Number:
  US 20100067892A1
• Time in Patent Office: 993 Days
• Field of Search: 396/124, 348/349
• US Class Current: 396/124
• CPC Class Codes: G03B 13/36 Autofocus systems
• CPC Class Codes: H04N 23/61 based on recognised objects
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method
• CPC Class Codes: H04N 23/675 comprising setting of focusing regions

Abstract

In an imaging apparatus, wherein when performing auto focus control while continuously moving a focusing lens by using an image sensor that has a lag in timing of electric charge accumulation, a focusing accuracy can be improved. To this end, the imaging apparatus includes the rolling shutter function, an imaging unit configured to convert an object image into an image signal, and a setting unit. When a difference exceeds a predetermined amount in the barycentric position of the optical system between an upper line and an a lower line of the AF area due to the rolling shutter function, the setting unit imposes a limitation on the AF area to reduce the size of a desired AF area to an AF area where the difference in the barycentric position becomes a predetermined amount.

Claims

1. An imaging apparatus comprising:

an imaging unit having a plurality of pixels arranged two-dimensionally in a row direction and a column direction and configured to obtain an image of an object by sequentially scanning a plurality of pixels to read out an image signal while moving the position of a focusing lens;

a detection unit to detect an object area in an image obtained by the imaging unit;

a setting unit to set an AF area corresponding to the object area detected by the detection unit; and

a focusing control unit configured to obtain in-focus states of a plurality of images in the AF area set by the setting unit, the plurality of images being captured by the imaging unit, and based on information about the in-focus states, to perform focusing control of the focusing lens,

wherein when the object area is larger than a predetermined size, the setting unit sets an AF area which is smaller than an AF area which corresponds to the object area by decreasing only the size of the object area in the row direction or in the column direction in which a difference occurs in charge readout timing.

2. The imaging apparatus according to claim 1, wherein the detection unit detects the object by extracting face information from the image, and the setting unit sets the AF area according to the face information.

3. The imaging apparatus according to claim 1,

wherein the setting unit switches over depending on whether to set a smaller AF area than an AF area corresponding to the object area according to at least one of a state and a mode of an AF operation.

4. The imaging apparatus according to claim 3, wherein in a mode of placing more priority on tracking of the object than in a case of shooting a still image, the setting unit does not set a smaller AF area than an AF area corresponding to the object area even if the object area is larger than the predetermined size.

5. An imaging apparatus comprising:

an imaging unit having a plurality of pixels arranged two-dimensionally and configured to obtain an image of an object by sequentially scanning a plurality of pixels to read out an image signal while moving the position of a focusing lens;

a detection unit to detect an object area in an image obtained by the imaging unit;

a setting unit to set an AF area corresponding to the object area detected by the detection unit; and

a focusing control unit configured to obtain in-focus states of a plurality of images in the AF area set by the setting unit, the plurality of images being captured by the imaging unit, and based on information about the in-focus states, to perform focusing control of the focusing lens,

wherein when the object area is larger than a predetermined size, the setting unit sets an AF area which is smaller than an AF area which corresponds to the object area, and

wherein when the setting unit sets an AF area smaller than an AF area corresponding to the object area, if the face orientation detected by the detection unit is the same as the direction in which a difference occurs in the charge readout timing, the setting unit sets an AF area so as to include both of eyes detected by the detection unit, and if those two directions differ from each other, the setting unit sets an AF area so as to include one eye detected by the detection unit.

6. The imaging apparatus according to claim 5, wherein the setting unit switches over depending on whether to set a smaller AF area than an AF area corresponding to the object area according to at least one of a state and a mode of an AF operation.

7. The imaging apparatus according to claim 6, wherein in an AF operation, when a still image is captured, the setting unit sets a smaller AF area than an AF area corresponding to an area of the object.

8. The imaging apparatus according to claim 5, further comprising a calculation unit configured to calculate barycentric position of the focusing lens corresponding to the AF area,

wherein the focusing control unit performs focusing control by moving the focusing lens to a barycentric position at which the in-focus state in the AF area is at a maximum.

9. A control method for an imaging apparatus having an imaging unit including a plurality of pixels arranged two-dimensionally and configured to capture an image of an object by sequentially scanning a plurality of pixels to read out an image signal from each pixel while moving the position of a focusing lens, and configured to perform focusing control of the imaging apparatus by taking a plurality of images of an object while moving a position of a focusing lens, and obtaining in-focus states in the AF areas set in the plurality of images, the method comprising:

detecting the object areas in the images; and

setting AF areas associated with the object areas,

wherein when an object area is larger than a predetermined size, a smaller AF area than the AF area corresponding to the object area is set, and

wherein when a set AF area is smaller than the AF area corresponding to the object area, if a face orientation detected is the same as the direction in which a difference occurs in a charge readout timing, an AF area is set so as to include both eyes detected, and if those two directions differ from each other, the an AF area is set so as to include at least one eye detected.