Image capturing apparatus, image capturing method, and control method for reducing the influence of flicker on still image exposure

Patent metadata

Field	Value
Publication number	US-9756258-B2
Application number	US-201414520728-A
Country	US
Kind code	B2
Filing date	Oct 22, 2014
Priority date	Oct 30, 2013
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

There is provided an image capturing apparatus comprising an image capturing unit. A control unit controls the image capturing unit to capture a first image having exposure unevenness caused by flicker in a light source. A detection unit detects a timing at which there is a low change in a light amount caused by the flicker, based on the exposure unevenness in the first image. An accepting unit accepts an image capturing instruction. The control unit controls the image capturing unit to capture a second image at the detected timing in response to the image capturing instruction.

First claim

What is claimed is:

1. An image capturing apparatus comprising:
an image capturing unit having an image sensor that starts exposure at different timings from region to region; and
at least one processor programmed to function as a calculation unit and a determination unit, wherein:
the calculation unit is configured to calculate a timing at which a light amount of a light source meets a predetermined condition based on image data obtained by the image capturing unit; and
the determination unit is configured to determine an exposure timing for the image capturing unit based on the timing that meets the predetermined condition calculated by the calculation unit,
wherein the image capturing unit obtains image data using a first exposure time that is shorter than a cycle of a change in a light amount of a flickering light source during a period from when the image capturing unit starts to obtain image data for a moving picture to when the image capturing unit starts to obtain image data for a still image;
the calculation unit calculates the timing that meets the predetermined condition based on the image data obtained using the first exposure time; and
the determination unit determines the exposure timing for the image capturing unit for obtaining the image data for a still image based on the timing that meets the predetermined condition calculated by the calculation unit.

2. The image capturing apparatus according to claim 1 ,
wherein the calculation unit calculates the timing that meets the predetermined condition based on a result of comparing the image data for a moving picture with the image data obtained using the first exposure time.

3. The image capturing apparatus according to claim 1 , further comprising:
an accepting unit configured to accept an image capturing instruction,
wherein in a case where the accepting unit has accepted the image capturing instruction while the image data for a moving picture is being repeatedly obtained, the image capturing unit obtains the image data using the first exposure time during a period from when the image capturing instruction is accepted by the accepting unit to when the image data for a still image starts to be obtained in response to the image capturing instruction.

4. The image capturing apparatus according to claim 1 ,
wherein the image capturing unit obtains the image data using the first exposure time during a period from when a piece of the image data for a moving picture is obtained to when a next piece of the image data for a moving picture is obtained.

5. The image capturing apparatus according to claim 4 , wherein the at least one processor is further programmed to function as an accepting unit configured to accept an image capturing instruction,
wherein in a case where the accepting unit has accepted the image capturing instruction while the image data for a moving picture is being repeatedly obtained, the image capturing unit does not obtain the image data using the first exposure time during a period from when the image capturing instruction is accepted by the accepting unit to when the image data for a still image starts to be obtained in response to the image capturing instruction; and
the calculation unit calculates the timing that meets the predetermined condition based on the image data obtained using the first exposure time before the image capturing instruction is accepted by the accepting unit.

6. The image capturing apparatus according to claim 4 ,
wherein the image capturing unit periodically obtains the image data using the first exposure time.

7. The image capturing apparatus according to claim 6 ,
wherein the calculation unit calculates the timing that meets the predetermined condition based on a latest image data obtained using the first exposure time.

8. The image capturing apparatus according to claim 1 , further comprising:
a display unit configured to continuously display an image based on the image data for a moving picture obtained by the image capturing unit,
wherein the display unit does not display an image based on the image data obtained using the first exposure time.

9. The image capturing apparatus according to claim 1 , wherein the at least one processor is further programmed to function as a storage configured to store moving picture information based on the image data for a moving picture in a storage medium,
wherein the storage does not include the image data obtained using the first exposure time in the moving picture information.

10. The image capturing apparatus according to claim 1 ,
wherein the image capturing unit obtains the image data for a moving picture using a second exposure time that is equivalent to an integral multiple of the cycle of the change in the light amount of the flickering light source.

11. The image capturing apparatus according to claim 10 ,
wherein the calculation unit calculates the timing that meets the predetermined condition by dividing the image data obtained using the first exposure time by the image data obtained using the second exposure time.

12. The image capturing apparatus according to claim 11 ,
wherein the timing that meets the predetermined condition is a timing at which there is a low change in a light amount caused by flicker.

13. A control method for an image capturing apparatus including an image capturing unit having an image sensor that starts exposure at different timings from region to region, the method comprising:
calculating a timing at which a light amount of a light source meets a predetermined condition based on image data obtained by the image capturing unit;
determining an exposure timing for the image capturing unit based on the timing that meets the predetermined condition calculated in the calculating; and
obtaining image data using a first exposure time that is shorter than a cycle of a change in a light amount of a flickering light source during a period from when the image capturing unit starts to obtain image data for a moving picture to when the image capturing unit starts to obtain image data for a still image,
wherein in the calculating, the timing that meets the predetermined condition is calculated based on the image data obtained using the first exposure time; and
in the determining, the exposure timing for the image capturing unit for obtaining the image data for a still image is determined based on the timing that meets the predetermined condition calculated in the calculating.

Assignees

• Canon Kk

Inventors

• Ariga Yuichi

Classifications

• H04N23/70

  Circuitry for compensating brightness variation in the scene · CPC title

• H04N23/73

  by influencing the exposure time · CPC title

• G03B7/093

  for control of exposure time · CPC title

• H04N25/531

  by controlling rolling shutters in CMOS SSIS · CPC title

• H04N23/745 Primary

  Detection of flicker frequency or suppression of flicker wherein the flicker is caused by illumination, e.g. due to fluorescent tube illumination or pulsed LED illumination · CPC title