Image capturing apparatus and focus detection method

• US 8,854,529 B2
• Filed: 12/03/2012
• Issued: 10/07/2014
• Est. Priority Date: 12/13/2011
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Yoshimura, Yuki, Fukuda, Koichi
• Primary Examiner(s): CHEN, CHIA WEI A
• Application Number:
  US13/692,173
• Publication Number:
  US 20130147998A1
• Time in Patent Office: 673 Days
• Field of Search: 348345-356, 348/222.1, 348/223.1, 348/224.1, 382/255
• US Class Current: 348/345
• CPC Class Codes: H01L 27/14645 Colour imagers
• CPC Class Codes: H04N 23/672 based on the phase difference signals
• CPC Class Codes: H04N 25/134 based on three different wavelength filter elements
• CPC Class Codes: H04N 25/704 Pixels specially adapted for focusing, e.g. phase difference pixel sets

Abstract

An image capturing apparatus performs focus detection based on a pair of image signals obtained from an image sensor including pixels each having a pair of photoelectric conversion units capable of outputting the pair of image signals obtained by independently receiving a pair of light beams that have passed through different exit pupil regions of an imaging optical system. In the focus detection, an f-number of the imaging optical system is acquired, the pair of image signals undergo filtering using a first filter formed from an summation filter when the f-number is less than a predetermined threshold, or using a second filter formed from the summation filter and a differential filter when the f-number is not less than the threshold, and focus detection is performed by a phase difference method based on the pair of filtered image signals.

Claims

1. An image capturing apparatus comprising:

an image sensor including a plurality of two-dimensionally arranged pixels including pixels each having a pair of photoelectric conversion units arranged to output a pair of image signals obtained by independently receiving a pair of light beams that have passed through different exit pupil regions of an imaging optical system;

a first filter formed from a summation filter;

a second filter formed from the summation filter and a differential filter;

an acquisition unit arranged to acquire an f-number of the imaging optical system;

a filtering unit arranged to perform filtering of the pair of image signals by selecting the first filter when the f-number is less than a predetermined threshold and selecting the second filter when the f-number is not less than the threshold; and

a focus detection unit arranged to perform focus detection by a phase difference method based on the pair of image signals that have undergone the filtering by the filtering unit.

2. The image capturing apparatus as claimed in claim 1, wherein in the summation filter, all components of the filter have positive values, and in the differential filter all components of the filter have positive and negative values.

3. An image sensor adapted for use in the image capturing apparatus of claim 1.

4. A focus detection method of performing focus detection based on a pair of image signals obtained from an image sensor including a plurality of two-dimensionally arranged pixels including pixels each having a pair of photoelectric conversion units capable of outputting the pair of image signals obtained by independently receiving a pair of light beams that have passed through different exit pupil regions of an imaging optical system, the method comprising:

an acquisition step of acquiring an f-number of the imaging optical system;

a filtering step of performing filtering of the pair of image signals using a first filter formed from a summation filter when the f-number is less than a predetermined threshold, and performing filtering of the pair of image signals using a second filter formed from the summation filter and a differential filter when the f-number is not less than the threshold; and

a focus detection step of performing focus detection by a phase difference method based on the pair of image signals that have undergone the filtering in the filtering step.