IMAGE PROCESSING APPARATUS AND METHOD

• US 20080252750A1
• Filed: 04/08/2008
• Published: 10/16/2008
• Est. Priority Date: 04/13/2007
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Ogawa, Katsuhisa
• Granted Patent: US 8,189,069 B2
• Time in Patent Office: Days
• US Class Current: 348/229.1
• CPC Class Codes: H04N 23/667 Camera operation mode switching, e.g. between still and video, sport and normal or high- and low-resolution modes
• CPC Class Codes: H04N 23/76 by influencing the image signals
• CPC Class Codes: H04N 23/951 by using two or more images to influence resolution, frame rate or aspect ratio

Abstract

An image processing apparatus can determine a correction gain factor at a high rate of speed to synthesize an image. The image processing apparatus includes a long second middle luminance image detecting unit for detecting a pixel position of a pixel having a pixel value in a first middle luminance pixel value region from the long second exposure image, a short second middle luminance image detecting unit for detecting a pixel position of a pixel having a pixel value in second middle luminance pixel value region from the short second exposure image; a correction gain factor calculating unit for designating, as a common pixel, a pixel having a common pixel position such that the pixel position detected by the long second middle luminance image detecting unit is the same as the pixel position detected by the short second middle luminance image detecting unit, and for calculating a correction gain factor based on the pixel value of the long second exposure image and the pixel value of the short second exposure image at a pixel position of the common pixel position.

Claims

1. An image processing apparatus for synthesizing a long second exposure image derived by larger exposure quantity and a short second exposure image derived by smaller exposure quantity, for imaging of the same scene, comprising:

a long second middle luminance image detecting unit for detecting a pixel position of a pixel having a pixel value in first middle luminance pixel value region from the long second exposure image;

a short second middle luminance image detecting unit for detecting a pixel position of a pixel having a pixel value in second middle luminance pixel value region from the short second exposure image;

a correction gain factor calculating unit for designating, as a common pixel, a pixel having a common pixel position such that the pixel position detected by the long second middle luminance image detecting unit is the same as the pixel position detected by the short second middle luminance image detecting unit, and for calculating a correction gain factor based on the pixel value of the long second exposure image and the pixel value of the short second exposure image at a pixel position of the common pixel position; and

an image synthesizing unit for synthesizing for multiplying the short second exposure image by the correction gain factor, and for synthesizing the short second exposure image subjected to the multiplication and the long second exposure image.

2. The apparatus according to claim 1, wherein

the correction gain factor calculating unit calculates, as correction gain factor, an average value of ratio between the pixel value of the long second exposure image and the pixel value of the short second exposure image at the pixel position of the common pixel.

3. The apparatus according to claim 1, wherein

the first middle luminance pixel value region is within a range of 30 to 70% of a maximum luminance pixel value, and

the second middle luminance pixel value region is within a range of 30 to 70% of a maximum luminance pixel value.

4. The apparatus according to claim 1, wherein

the first middle luminance pixel value region is within a range of 10 to 80% of a maximum luminance pixel value, and

the second middle luminance pixel value region is within a range of 20 to 90% of a maximum luminance pixel value.

5. The apparatus according to claim 1, wherein

the numbers of the pixels included in the first and second middle luminance pixel value regions are converted by a moving image mode and a still image mode, such that the number of the pixels in the moving image mode is larger than that in the still image mode.

6. An image processing method for synthesizing a long second exposure image derived by larger exposure quantity and a short second exposure image derived by smaller exposure quantity, for imaging of the same scene, comprising:

a long second middle luminance image detecting step for detecting a pixel position of a pixel having a pixel value in first middle luminance pixel value region from the long second exposure image;

a short second middle luminance image detecting step for detecting a pixel position of a pixel having a pixel value in second middle luminance pixel value region from the short second exposure image;

a correction gain factor calculating step for designating, as a common pixel, a pixel having a common pixel position such that the pixel position detected by the long second middle luminance image detecting unit is the same as the pixel position detected by the short second middle luminance image detecting unit, and for calculating a correction gain factor based on the pixel value of the long second exposure image and the pixel value of the short second exposure image at a pixel position of the common pixel position; and

an image synthesizing step for synthesizing for multiplying the short second exposure image by the correction gain factor, and for synthesizing the short second exposure image subjected to the multiplication and the long second exposure image.