Image capture device and focus control method

Patent metadata

Field	Value
Publication number	US-9602717-B2
Application number	US-201615011993-A
Country	US
Kind code	B2
Filing date	Feb 1, 2016
Priority date	Sep 5, 2013
Publication date	Mar 21, 2017
Grant date	Mar 21, 2017

Abstract

Provided are an image capture device and a focus control method capable of performing auto-focus (AF) at high speed by reducing time until a focus control is completed even when a focus control based on a phase difference AF method and a focus control based on a contrast AF method are used in combination. A digital camera performs a correlation operation of two images captured by a pixel pair P 1 , performs a correlation operation of two images captured by a pixel pair P 2 , and determines reliability of correlation operation results based on information generated from the two correlation operation results. When the reliability is low, the digital camera performs the contrast AF. Here, the digital camera variably controls a movement step (arbitrary distance) when moving a focus lens in a predetermined range to calculate a contrast value, according to the height of the reliability.

First claim

What is claimed is:

1. An image capture device that includes an imaging element that images a subject through an imaging optical system including a focus lens, the imaging element including a first signal detector that detects a signal based on one beam among a pair of beams that passes through different portions in a pupil region of the imaging optical system, and a second signal detector that detects a signal based on the other beam among the pair of beams, and the image capture device comprising:
a focus controller that performs any one of a first focus control for moving the focus lens to a focusing position determined based on detection signals of the first signal detector and the second signal detector and a second focus control for moving the focus lens along an optical axis direction by an arbitrary distance in a predetermined movement range and moving the focus lens to a focusing position determined based on contrast of images captured by the imaging element at respective movement positions;
a focus control determinator that determines which one of the first focus control and the second focus control is to be performed based on information generated using the detection signals of the first signal detector and the second signal detector;
a controller that variably controls, in the case where it is determined that the second focus control is to be performed, at least the arbitrary distance, among the movement range and the arbitrary distance in the movement range, based on the information; and
an information generator that generates, based on correlation operation results between detection signals from the first signal detector and detection signals from the second signal detector, output from a first pair of a first signal detector group including a plurality of first signal detectors arranged along a phase difference detection direction in the first signal detector and the second signal detector and a third signal detector group including the second signal detectors arranged at the same distance in a direction orthogonal to the phase difference detection direction with respect to the respective signal detectors of the first signal detector group, and based on correlation operation results between detection signals from the first signal detector and detection signals from the second signal detector, output from a second pair of a second signal detector group including a plurality of first signal detectors arranged at the same distance in the same direction with respect to the respective signal detectors of the first signal detector group and arranged along the detection direction and fourth signal detector group including the second signal detectors arranged at the same distance in a direction opposite to a direction orthogonal to the phase difference detection direction with respect to the respective signal detectors of the second signal detector group, a reliability determination value for determining reliability of the correlation operation results as the information,
wherein the focus control determinator determines which one of the first focus control and the second focus control is to be performed according to the size of the reliability determination value, and
wherein the controller determines, in the case where it is determined that the second focus control is to be performed, a factor for the determination that the second focus control is to be performed according to the size of the reliability determination value, and reduces, in the case where the factor is based on a frequency of a subject image, the arbitrary distance compared with a case where the factor is not based on the frequency of the subject image.

2. The image capture device according to claim 1 ,
wherein in the case where the factor is not based on the frequency of the subject image, the reliability of the correlation operation results based on the reliability determination value is equal to or greater than a first threshold value, and phase differences which are the correlation operation results are equal to or greater than a second threshold value, the controller increases the arbitrary distance, compared with a case where the factor is not based on the frequency of the subject image, the reliability of the correlation operation results based on the reliability determination value is smaller than the first threshold value, or compared with a case where the factor is not based on the frequency of the subject image, the reliability of the correlation operation results based on the reliability determination value is equal to or greater than the first threshold value, and the phase differences are smaller than the second threshold value.

3. The image capture device according to claim 1 ,
wherein in the case where the factor is not based on the frequency of the subject image and the reliability of the correlation operation results based on the reliability determination value is equal to or greater than the first threshold value, the controller narrows the movement range compared with a maximum range where the focus lens is movable.

4. The image capture device according to claim 2 ,
wherein in the case where the factor is not based on the frequency of the subject image and the reliability of the correlation operation results based on the reliability determination value is equal to or greater than the first threshold value, the controller narrows the movement range compared with a maximum range where the focus lens is movable.

5. The image capture device according to claim 1 ,
wherein in the case where the factor is based on the frequency of the subject image, the controller narrows the movement range compared with the maximum range where the focus lens is movable.

6. The image capture device according to claim 2 ,
wherein in the case where the factor is based on the frequency of the subject image, the controller narrows the movement range compared with the maximum range where the focus lens is movable.

7. The image capture device according to claim 3 ,
wherein in the case where the factor is based on the frequency of the subject image, the controller narrows the movement range compared with the maximum range where the focus lens is movable.

8. The image capture device according to claim 4 ,
wherein in the case where the factor is based on the frequency of the subject image, the controller narrows the movement range compared with the maximum range where the focus lens is movable.

9. An image capture device that includes an imaging element that images a subject through an imaging optical system including a focus lens, the imaging element including a first signal detector that detects a signal based on one beam among a pair of beams that passes through different portions in a pupil region of the imaging optical system, and a second signal detector that detects a signal based on the other beam among the pair of beams, and the image capture device comprising:
a focus controller that performs any one of a first focus control for moving the focus lens to a focusing position determined based on detection signals of the first signal detector and the second signal detector and a second focus control for moving the focus lens along an optical axis direction by an arbitrary distance in a predetermined movement range and moving the focus lens to a focusing position determined based on contrast of images captured by the imaging element at respective movement positions;
a focus control determinator that determines which one of the first focus control and the second focus control is to be performed based on information generated using the detection signals of the first signal detector and the second signal detector;
a controller that variably controls, in the case where

Assignees

• Fujifilm Corp

Inventors

• Sakurabu Hitoshi

Classifications

• H04N23/632

  for displaying or modifying preview images prior to image capturing, e.g. variety of image resolutions or capturing parameters · CPC title

• H04N23/635

  Region indicators; Field of view indicators · CPC title

• H04N23/672 Primary

  based on the phase difference signals · CPC title

• H04N23/673

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

• H04N25/134

  based on three different wavelength filter elements · CPC title