Image device and focus control method

Patent metadata

Field	Value
Publication number	US-9288384-B2
Application number	US-201414529979-A
Country	US
Kind code	B2
Filing date	Oct 31, 2014
Priority date	May 1, 2012
Publication date	Mar 15, 2016
Grant date	Mar 15, 2016

Abstract

When reliability of a defocus amount which is calculated using a signal from a region 50 A is low, a digital camera expands the phase difference detection target region to the regions 50 A, 50 B, and 50 C. Further, the digital camera calculates a defocus amount using a correlation operation result of an output signal group of pixel cells 31 R in an odd numbered column and an output signal group of the pixel cells 31 L in an odd numbered column and a correlation operation result of an output signal group of pixel cells 31 R in an even numbered column and an output signal group of the pixel cells 31 L in an even numbered column, in the regions 50 A, 50 B, and 50 C.

First claim

The invention claimed is:

1. An imaging device, comprising:
an imaging element that has a plurality of pairs of first pixel cells and second pixel cells receiving a pair of light fluxes passing through different pupil regions of an photographing optical system and outputting signals according to a light amount;
a first defocus amount calculating unit that calculates a defocus amount using a narrow range signal group obtained from the plurality of pairs in a first range;
a second defocus amount calculating unit that calculates a defocus amount using a broad range signal group obtained from all the pairs in a second range which includes the first range and is broader than the first range; and
a focus control unit that controls a focus state of the imaging optical system based on the defocus amount calculated by the first defocus amount calculating unit and the defocus amount calculated by the second defocus amount calculating unit,
wherein the second defocus amount calculating unit generates a broad pitch signal group having an arrangement pitch being larger than an arrangement pitch of the narrow range signal groups using the broad range signal group and calculates the defocus amount using the broad pitch signal group.

2. The imaging device of claim 1 , wherein the second defocus amount calculating unit performs first processing which generates as the broad pitch signal groups, two signal groups of a signal group obtained by sampling the pair of signals with an interval of a predetermined number of pixel cells from the broad range signal group and the remaining signal group, performs a correlation operation on the signals of the first pixel cells and the signals of the second pixel cells with respect to each of the two broad pitch signal groups and calculates the defocus amount using the two correlation operation results.

3. The imaging device of claim 2 , wherein when a brightness of a subject exceeds a predetermined value, the second defocus amount calculating unit performs second processing which calculates the defocus amount based on the correlation operation result on one of the two broad pitch signal groups.

4. The imaging device of claim 2 , further comprising:
an imaging element driving unit that, when the defocus amount is calculated by the first processing, is driven to independently read out the two broad pitch signal groups from the imaging element.

5. The imaging device of claim 4 , wherein when a brightness of a subject exceeds a predetermined value, the second defocus amount calculating unit performs second processing which calculates the defocus amount based on the correlation operation result on one of the two broad pitch signal groups, and
when the brightness of the subject exceeds the predetermined value, the imaging element driving unit omits to read out the other of the two broad pitch signal groups from the imaging element.

6. The imaging device of claim 1 , wherein the second defocus amount calculating unit performs third processing which divides the broad range signal group into a plurality of groups which is continuously arranged and each of which has a plurality of pixel cells, adds the signals in the first pixel cells in each group and adds the signals in the second pixel cells in each group to generate the broad pitch signal group and calculates the defocus amount based on the correlation operation result of the signal group in the first pixel cells and the signal group in the second pixel cells in the broad pitch signal group.

7. The imaging device of claim 6 , wherein when the brightness of the subject is equal to or smaller than the predetermined value, the second defocus amount calculating unit calculates the defocus amount by the third processing.

8. The imaging device of claim 6 , wherein the third processing is processing which adds the signals of the first pixel cells in each group in the imaging element and adds the signals of the second pixel cells in each group in the imaging element to generate the broad pitch signal group.

9. A focus control method of an imaging device including an imaging element that has a plurality of pairs of first pixel cells and second pixel cells receiving a pair of light fluxes passing through different pupil regions of an photographing optical system and outputting signals according to a light amount, the method comprising:
a first defocus amount calculating step that calculates a defocus amount using a narrow range signal group obtained from the plurality of pairs in a first range;
a second defocus amount calculating step that calculates a defocus amount using a broad range signal group obtained from all the pairs in a second range which includes the first range and is broader than the first range; and
a focus control step that controls a focus state of the imaging optical system based on the defocus amount calculated by the first defocus amount calculating step and the defocus amount calculated by the second defocus amount calculating step,
wherein the second defocus amount calculating step generates a broad pitch signal group having an arrangement pitch being larger than an arrangement pitch of the narrow range signal groups using the broad range signal group and calculates the defocus amount using the broad pitch signal group.

Assignees

• Fujifilm Corp

Inventors

• Aoki Takashi

Classifications

• 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

• H04N25/703

  SSIS architectures incorporating pixels for producing signals other than image signals · CPC title

• H04N23/11

  for generating image signals from visible and infrared light wavelengths · CPC title