Image pickup apparatus that automatically adjusts black balance, control method therefor, and storage medium

• US 10,182,188 B2
• Filed: 03/23/2016
• Issued: 01/15/2019
• Est. Priority Date: 03/27/2015
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Uemura, Hidetaka
• Primary Examiner(s): Ho, Tuan
• Assistant Examiner(s): Camargo, Marly
• Application Number:
  US15/078,108
• Publication Number:
  US 20160286112A1
• Time in Patent Office: 1,028 Days
• Field of Search: 3482231, 3482241, 3482291, 348175, 348187, 3482211, 348362, 34820812, 348379, 348655, 348 E507, 348 E5072, 348 E9051, 348360, 348361, 396 63, 396 65, 396 89, 396155, 396157, 396161, 396166, 396167, 396180, 396215, 396241, 250204, 2502081, 359888
• CPC Class Codes: H04N 17/002 for television cameras
• CPC Class Codes: H04N 23/71 Circuitry for evaluating the brightness variation
• CPC Class Codes: H04N 23/72 Combination of two or more compensation controls

Abstract

An image pickup apparatus which is capable of performing automatic adjustment of black balance properly without the need to have a member for fully shielding light. A diaphragm of a lens barrel and an ND filter, which is provided separately from the diaphragm, adjust the amount of light incident on an image pickup device that picks up an image of a subject. Whether the automatic adjustment is possible in present image pickup environment is judged based on evaluation values of a picked-up image obtained in a state where the amounts of incident light are maximized by respective ones of the diaphragm and the ND filter, and a predetermined judgment threshold value which is determined based on a range over which the amount of incident light is adjustable by the diaphragm and a range over which the amount of incident light is adjustable by the ND filter.

Claims

1. An image pickup apparatus comprising:

an image pickup unit configured to pick up an image of a subject;

a first adjustment unit configured to adjust an amount of light incident on said image pickup unit;

a second adjustment unit configured to be provided separately from said first adjustment unit and adjust an amount of light incident on said image pickup unit;

a judgment unit configured to judge whether an image pickup environment is dark to the extent that automatic adjustment of black balance is possible, based on evaluation values of a picked-up image obtained in a state where the amounts of incident light are maximized by respective ones of said first adjustment unit and said second adjustment unit, and a predetermined judgment threshold value;

a determination unit configured to determine the judgment threshold value based on a range over which the amount of incident light is adjustable by said first adjustment unit and a range over which the amount of incident light is adjustable by said second adjustment unit; and

a generation unit configured to, when said judgment unit judges that the automatic adjustment is possible in a state in which the image pickup environment is sufficiently dark, generate image correction data for adjusting black balance in a state where the amounts of incident light are minimized by respective ones of said first adjustment unit and said second adjustment unit.

2. The image pickup apparatus according to claim 1, wherein said judgment unit divides the picked-up image into a plurality of areas, and when all the evaluation values in the respective ones of the plurality of areas are not greater than the judgment threshold value, said judgment unit judges that the automatic adjustment is possible.

3. The image pickup apparatus according to claim 2, further comprising a changing unit configured to change an angle of view, at which said image pickup unit picks up an image, by at least one of panning, tilting, and zooming,

wherein said changing unit changes the angle of view such that evaluation values in all areas within the angle of view do not become greater than the judgment threshold value when said judgment unit judges that an evaluation value in at least one among the plurality of areas is greater than the judgment threshold value, and

said generation unit generates the image correction data in an area after the angle of view is changed by said changing unit.

4. The image pickup apparatus according to claim 2, further comprising a monitoring unit configured to, when said judgment unit judges that an evaluation value in at least one among the plurality of areas is greater than the judgment threshold value, monitor whether the area with an evaluation value that is greater than the judgment threshold value moves,

wherein said judgment unit does not make the automatic adjustment when said monitoring unit judges that the area with an evaluation value that is greater than the judgment threshold value moves, and said judgment unit makes the automatic adjustment when said monitoring unit judges that the area with an evaluation value that is greater than the judgment threshold value does not move.

5. The image pickup apparatus according to claim 1, wherein said first adjustment unit includes at least a diaphragm provided in a lens barrel which the image pickup apparatus has.

6. The image pickup apparatus according to claim 1, wherein said second adjustment unit is a neutral density filter or an electro chromic device.

7. A control method for an image pickup apparatus that automatically adjusts black balance, the image pickup apparatus having an image pickup unit that picks up an image of a subject, and a first adjustment unit and a second adjustment unit that adjust an amount of light incident on the image pickup unit, the control method comprising:

a determination step of, based on ranges over which amounts of light incident on an image pickup unit that picks up an image of a subject are adjustable by respective ones of a first adjustment unit and a second adjustment unit that adjust the amounts of light incident on the image pickup unit, determining a judgment threshold value for use in judging whether the automatic adjustment is possible in a present image pickup environment;

an image pickup step of picking up an image using the image pickup unit in a state where the amounts of incident light are maximized by respective ones of the first adjustment unit and the second adjustment unit;

a judgment step of judging whether an image pickup environment is dark to the extent that the automatic adjustment is possible, based on evaluation values of an picked-up image obtained in said image pickup step and the judgment threshold value determined in said determination step; and

a generation step of, when it is judged in said judgment step that the automatic adjustment is possible in a state in which the image pickup environment is sufficiently dark, picking up an image using the image pickup unit in a state where the amounts of incident light are minimized by respective ones of the first adjustment unit and the second adjustment unit, and based on the picked-up image thus obtained, generating image correction data for adjusting black balance for the automatic adjustment.

8. A non-transitory computer-readable storage medium storing a program for causing a computer to execute a control method for an image pickup apparatus that automatically adjusts black balance, the image pickup apparatus having an image pickup unit that picks up an image of a subject, and a first adjustment unit and a second adjustment unit that adjust an amount of light incident on the image pickup unit, the control method for the image pickup apparatus comprising:

a determination step of, based on ranges over which amounts of light incident on an image pickup unit that picks up an image of a subject are adjustable by respective ones of a first adjustment unit and a second adjustment unit that adjust the amounts of light incident on the image pickup unit, determining a judgment threshold value for use in judging whether the automatic adjustment is possible in a present image pickup environment;

an image pickup step of picking up an image using the image pickup unit in a state where the amounts of incident light are maximized by respective ones of the first adjustment unit and the second adjustment unit;

a judgment step of judging whether an image pickup environment is dark to the extent that the automatic adjustment is possible, based on evaluation values of an picked-up image obtained in said image pickup step and the judgment threshold value determined in said determination step; and

a generation step of, when it is judged in said judgment step that the automatic adjustment is possible in a state in which the image pickup environment is sufficiently dark, picking up an image using the image pickup unit in a state where the amounts of incident light are minimized by respective ones of the first adjustment unit and the second adjustment unit, and based on the picked-up image thus obtained, generating image correction data for adjusting black balance for the automatic adjustment.

9. An image pickup apparatus comprising:

an image pickup device configured to pick up an image of a subject; and

one or more processors configured to implement a first adjustment unit, a second adjustment unit, a judgement unit, a determination unit and a generation unit, wherein;

said first adjustment unit is configured to adjust an amount of light incident on said image pickup unit,

said second adjustment unit is configured to be provided separately from said first adjustment unit and adjust an amount of light incident on said image pickup unit,

said judgment unit is configured to judge whether an image pickup environment is dark to the extent that automatic adjustment of black balance is possible, based on evaluation values of a picked-up image obtained in a state where the amounts of incident light are adjusted to a first amount by respective ones of said first adjustment unit and said second adjustment unit, and a predetermined judgment threshold value,

said determination unit is configured to determine the judgment threshold value based on a range over which the amount of incident light is adjustable by said first adjustment unit and a range over which the amount of incident light is adjustable by said second adjustment unit; and

said generation unit is configured to, when said judgment unit judges that the automatic adjustment is possible in a state in which the image pickup environment is sufficiently dark, generate image correction data for adjusting black balance in a state where the amounts of incident light are adjusted to a second amount smaller than the first amount by respective ones of said first adjustment unit and said second adjustment unit.

10. The image pickup apparatus according to claim 9, wherein said judgment unit divides the picked-up image into a plurality of areas, and when all the evaluation values in the respective ones of the plurality of areas are not greater than the judgment threshold value, said judgment unit judges that the automatic adjustment is possible.

11. The image pickup apparatus according to claim 9, wherein said first adjustment unit includes at least a diaphragm provided in a lens barrel which the image pickup apparatus has.

12. The image pickup apparatus according to claim 9, wherein said second adjustment unit is a neutral filter or an electro chromatic device.