Image processing device that performs white balance control, method of controlling the same, and image pickup apparatus

Patent metadata

Field	Value
Publication number	US-2016007001-A1
Application number	US-201514790652-A
Country	US
Kind code	A1
Filing date	Jul 2, 2015
Priority date	Jul 7, 2014
Publication date	Jan 7, 2016
Grant date	—

Abstract

An image processing device capable of stably performing white balance control. A first WB correction value is calculated according to an infrared light amount obtained from a first image. A second WB correction value different from the first one is calculated according to white pixels obtained from the first image. A third WB correction value is calculated based on the first and second WB correction values. White balance processing is performed on the first image using the third WB correction value, which is stored as a reference WB correction value. When the infrared light amount not smaller than a predetermined amount is obtained from the second image and also the number of obtained white pixels is smaller than a predetermined number, white balance processing is performed on the second image using the stored reference WB correction value.

First claim

What is claimed is:

1 . An image processing device that performs white balance processing, comprising:
a first calculation unit configured to calculate a first white balance correction value for performing white balance processing, according to an amount of infrared light obtained from a first image; a second calculation unit configured to calculate a second white balance correction value which is different from the first white balance correction value, according to white pixels obtained from the first image; a third calculation unit configured to calculate a third white balance correction value based on the first white balance correction value and the second white balance correction value; a white balance control unit configured to perform white balance processing on the first image using the third white balance correction value; and a storage unit configured to store the third white balance correction value as a reference white balance correction value, wherein when performing white balance processing on a second image which is obtained through photographing performed later than photographing the first image, said white balance control unit performs, in a case where an amount of infrared light not smaller than a predetermined amount is obtained from the second image, and also the number of obtained white pixels in the second image is smaller than a predetermined number, white balance processing on the second image using the reference white balance correction value stored in said storage unit.

2 . The image processing device according to claim 1 , wherein when the amount of infrared light not smaller than the predetermined amount is obtained from the second image and also the number of white pixels in the second image is not smaller than the predetermined number, said white balance control unit updates the reference white balance correction value stored in said storage unit with the third white balance correction value calculated using the second image.

3 . The image processing device according to claim 1 , wherein when the amount of infrared light not smaller than the predetermined amount is not detected from the second image, said white balance control unit initializes the reference white balance correction value stored in said storage unit.

4 . The image processing device according to claim 1 , wherein when the white pixels in the second image are more than the white pixels in an image used for calculation of the reference white balance correction value stored in said storage unit, said white balance control unit performs white balance processing using the third white balance correction value calculated using the second image, and updates the reference white balance correction value stored in said storage unit with the third white balance correction value calculated using the second image.

5 . The image processing device according to claim 1 , wherein when the white pixels in the second image are less than the white pixels in an image used for calculation of the reference white balance correction value stored in said storage unit, said white balance control unit performs white balance processing using the reference white balance correction value stored in said storage unit.

6 . The image processing device according to claim 1 , wherein when a difference between the third white balance correction value calculated using the second image and the reference white balance correction value stored in said storage unit is not smaller than a predetermined difference threshold value, said white balance control unit performs white balance processing using a shifted white balance correction value obtained by shifting the reference white balance correction value stored in said storage unit by a predetermined shift threshold value toward the third white balance correction value calculated using the second image, and updates the reference white balance correction value stored in said storage unit with the shifted white balance correction value.

7 . The image processing device according to claim 1 , wherein when a difference between the third white balance correction value calculated using the second image and the reference white balance correction value stored in said storage unit is smaller than the predetermined difference threshold value, said white balance control unit performs white balance processing using the third white balance correction value calculated using the second image, and updates the reference white balance correction value stored in said storage unit with the third white balance correction value calculated using the second image.

8 . The image processing device according to claim 1 , wherein when a predetermined time period elapses after a time at which the first image was obtained, said white balance control unit initializes the reference white balance correction value stored in said storage unit.

9 . The image processing device according to claim 1 , wherein when a difference between a color temperature of light from a light source in the second image and a color temperature of light from a light source in an image from which the reference white balance correction value stored in said storage unit is calculated is not smaller than a predetermined temperature, said white balance control unit performs white balance processing using the third white balance correction value calculated using the second image, and updates the reference white balance correction value stored in said storage unit with the third white balance correction value calculated using the second image.

10 . An image pickup apparatus comprising:
an image pickup device; an infrared light sensor that detects infrared light; an acquisition unit configured to acquire a color evaluation value from a first image obtained through photographing performed using said image pickup device; a calculation unit configured to calculate a white balance correction value using a result of detection of an amount of infrared light when photographing the first image and the color evaluation value acquired from the first image; an image processing unit configured to perform white balance correction processing on the first image using the white balance correction value; and a storage unit configured to store the white balance correction value used for the white balance correction processing, wherein when performing white balance processing on a second image which is obtained through photographing performed later than photographing the first image, said image processing unit determines, using the result of detection of the amount of infrared light when photographing the second image, whether or not to take over the reference white balance correction value stored in said storage unit, and then performs white balance processing on the second image.

11 . The image pickup apparatus according to claim 10 , wherein said acquisition unit acquires a color evaluation value from each area obtained by dividing the first image into a plurality of area, and
wherein said calculation unit determines, based on an amount of infrared light detected from each area, whether or not the color of the area is a color of an object, and calculates the white balance correction value from color evaluation values of areas the color of which is determined to be the color of the object.

12 . A method of controlling an image processing device that performs white balance processing and includes a storage unit, comprising:
calculating a first white balance correction value for performing white balance processing, according to an amount of infrared light obtained from a first image; calculating a second white balance correction value whic

Assignees

• Canon Kk

Inventors

• Kuchiki Hiroaki

Classifications

• H04N23/74

  by influencing the scene brightness using illuminating means · CPC title

• H04N25/134

  based on three different wavelength filter elements · CPC title

• H04N23/843

  Demosaicing, e.g. interpolating colour pixel values · CPC title

• H04N23/88 Primary

  for colour balance, e.g. white-balance circuits or colour temperature control · CPC title

• G01J5/60 Primary

  using determination of colour temperature · CPC title