Focus detection apparatus and control method thereof

Patent metadata

Field	Value
Publication number	US-9531944-B2
Application number	US-201514665618-A
Country	US
Kind code	B2
Filing date	Mar 23, 2015
Priority date	Mar 26, 2014
Publication date	Dec 27, 2016
Grant date	Dec 27, 2016

Abstract

A first phase difference between a first image signal output from a first pixel configured to detect a light flux having passed through a first partial area of the exit pupil, and a second image signal output from a third pixel configured to detect a light flux having passed through the entire exit pupil is computed. A second phase difference between a third image signal output from a second pixel configured to detect a light flux having passed through a second partial area of the exit pupil, and a fourth image signal output from a fourth pixel arranged at a position different from the third pixel and configured to detect a light flux having passed through the entire exit pupil is computed. The defocus amount of the imaging optical system is computed by using the sum of the first and second phase differences.

First claim

What is claimed is:

1. A focus detection apparatus comprising:
a first pixel configured to detect a light flux having passed through a partial area of an exit pupil of an imaging optical system;
a second pixel configured to detect a light flux having passed through a partial area of the exit pupil of the imaging optical system that is different from the area through which the light flux detected by said first pixel has passed;
a third pixel configured to detect a light flux having passed through an entire area of the exit pupil of the imaging optical system;
a fourth pixel arranged at a position different from said third pixel and configured to detect a light flux having passed through the entire area of the exit pupil of the imaging optical system;
a first computation unit configured to compute a first phase difference between a first image signal output from said first pixel, and a second image signal output from said third pixel;
a second computation unit configured to compute a second phase difference between a third image signal output from said second pixel, and a fourth image signal output from said fourth pixel; and
a defocus amount computation unit configured to compute a defocus amount of the imaging optical system by using a sum of the first phase difference and the second phase difference.

2. The apparatus according to claim 1 , wherein said first pixel and said second pixel are spaced apart from each other in a direction perpendicular to a direction in which the first phase difference and the second phase difference are detected.

3. The apparatus according to claim 2 , wherein
a distance between said first pixel and said third pixel in the perpendicular direction is smaller than a distance between said first pixel and said second pixel in the perpendicular direction, and
a distance between said second pixel and said fourth pixel in the perpendicular direction is smaller than the distance between said first pixel and said second pixel in the perpendicular direction.

4. The apparatus according to claim 3 , wherein said first pixel and said third pixel are adjacent pixels, and said second pixel and said fourth pixel are adjacent pixels.

5. The apparatus according to claim 1 , wherein each of the second image signal and the fourth image signal is generated based on a plurality of pixel values.

6. The apparatus according to claim 1 , further comprising:
a third computation unit configured to detect a third phase difference between the first image signal and the third image signal; and
a fourth computation unit configured to detect a fourth phase difference between the second image signal and the fourth image signal,
wherein when a current defocus amount is larger than a predetermined threshold, said defocus amount computation unit computes the defocus amount of the imaging optical system based on a difference between the third phase difference and the fourth phase difference, and
when the current defocus amount is not larger than the predetermined threshold, said defocus amount computation unit computes the defocus amount of the imaging optical system based on a sum of the first phase difference and the second phase difference.

7. A focus detection apparatus comprising:
a first pixel configured to detect a light flux having passed through a partial area of an exit pupil of an imaging optical system;
a second pixel configured to detect a light flux having passed through a partial area of the exit pupil of the imaging optical system that is different from the area through which the light flux detected by said first pixel has passed;
a third pixel arranged at a position closer to said first pixel than said second pixel and configured to detect a light flux having passed through an entire area of the exit pupil of the imaging optical system;
a fourth pixel arranged at a position closer to said second pixel than said first pixel and configured to detect a light flux having passed through the entire area of the exit pupil of the imaging optical system;
a first computation unit configured to compute a first phase difference between a first image signal output from said first pixel, and a second image signal output from said third pixel;
a second computation unit configured to compute a second phase difference between a third image signal output from said second pixel, and a fourth image signal output from said fourth pixel; and
a defocus amount computation unit configured to compute a defocus amount of the imaging optical system by using a sum of the first phase difference and the second phase difference.

8. A focus detection apparatus comprising:
a first pixel configured to detect a light flux having passed through an exit pupil of an imaging optical system, a barycentric position of a projection image of a pixel that is projected on the exit pupil being shifted from a barycentric position of the exit pupil in a first direction perpendicular to an optical axis;
a second pixel configured to detect a light flux having passed through the exit pupil of the imaging optical system, a barycentric position of a projection image of a pixel that is projected on the exit pupil being shifted from the barycentric position of the exit pupil in a direction opposite to the first direction;
a third pixel configured to detect a light flux having passed through the exit pupil of the imaging optical system, a barycentric position of a projection image of a pixel that is projected on the exit pupil being positioned at the barycentric position of the exit pupil;
a fourth pixel arranged at a position different from said third pixel and configured to detect a light flux having passed through the exit pupil of the imaging optical system, a barycentric position of a projection image of a pixel that is projected on the exit pupil being positioned at the barycentric position of the exit pupil;
a first computation unit configured to compute a first phase difference between a first image signal output from said first pixel, and a second image signal output from said third pixel;
a second computation unit configured to compute a second phase difference between a third image signal output from said second pixel, and a fourth image signal output from said fourth pixel; and
a defocus amount computation unit configured to compute a defocus amount of the imaging optical system by using a sum of the first phase difference and the second phase difference.

9. A focus detection apparatus control method comprising:
a first detection step of detecting a light flux having passed through a partial area of an exit pupil of an imaging optical system;
a second detection step of detecting a light flux having passed through a partial area of the exit pupil of the imaging optical system that is different from the area through which the light flux detected in the first detection step;
a third detection step of detecting a light flux having passed through an entire area of the exit pupil of the imaging optical system;
a fourth detection step of detecting, at a position different from a position at which the third detection step detects the light flux, a light flux having passed through the entire area of the exit pupil of the imaging optical system;
a first computation step of computing a first phase difference between a first image signal obtained in the first detection step, and a second image signal obtained in the third detection step;
a second computation step of computing a second phase difference between a third image signal obtained in the second detection step, and a fourth image signal obtained in the fourth detection step; and
a defocus amount computation step of computing a defocus amount of the imaging optical system by using a sum of the

Assignees

• Canon Kk

Inventors

• Hamano Hideyuki

Classifications

• H04N25/704

  Pixels specially adapted for focusing, e.g. phase difference pixel sets · CPC title

• H04N23/673

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

• H04N23/672 Primary

  based on the phase difference signals · CPC title

• H04N25/134

  based on three different wavelength filter elements · CPC title

• H04N5/23212 Primary

  Electricity · mapped topic