Image processing apparatus for correcting pixel value based on difference between spectral sensitivity characteristic of pixel of interest and reference spectral sensitivity, image processing method, and computer-readable recording medium

Patent metadata

Field	Value
Publication number	US-10416026-B2
Application number	US-201715700254-A
Country	US
Kind code	B2
Filing date	Sep 11, 2017
Priority date	Mar 12, 2015
Publication date	Sep 17, 2019
Grant date	Sep 17, 2019

Abstract

An image processing apparatus is configured to: acquire a correction factor from a recording unit for recording, for each of a plurality of pixels, the correction factor for correcting a difference in pixel value corresponding to a difference between a spectral sensitivity and a preset reference spectral sensitivity in a predetermined wavelength range at a pixel of interest, based on image data generated by an image sensor, the image sensor having the plurality of pixels on which color filters of a plurality of colors with different spectral transmittances are respectively located, the color filters forming a predetermined array pattern; calculate a correction amount for correcting a pixel value of the pixel of interest based on the correction factor at the pixel of interest and pixel values of pixels surrounding the pixel of interest; and correct the pixel value of the pixel of interest by using the correction amount.

First claim

What is claimed is:

1. An image processing apparatus comprising:
a processor comprising hardware, wherein the processor is configured to:
perform a correction factor acquiring process comprising:
acquire image data from an image sensor, the image sensor comprising a pixel of interest in which a color filter of a first color is disposed and one or more additional pixels on which color filters of the first color are disposed;
determine a spectral sensitivity characteristic in a first predetermined wavelength range of the pixel of interest itself;
determine a spectral sensitivity characteristic in the first predetermined wavelength range of each of the one or more additional pixels;
determine a reference spectral sensitivity in the first predetermined wavelength range based on the spectral sensitivity characteristic in the first predetermined wavelength range of the each of the one or more additional pixels;
determine a difference between the spectral sensitivity characteristic of the pixel of interest and the reference spectral sensitivity in the first predetermined wavelength range; and
determine the correction factor for correcting a pixel value in the first predetermined wavelength range of the pixel of interest based on the difference;

calculate a correction amount for correcting the pixel value of the pixel of interest based on the correction factor at the pixel of interest acquired and pixel values of pixels surrounding the pixel of interest; and
correct the pixel value of the pixel of interest based on the correction amount calculated.

2. The image processing apparatus according to claim 1 ,
wherein the processor is configured to calculate the correction amount based on pixel values of pixels surrounding the pixel of interest on which color filters of colors different from the first color are disposed.

3. The image processing apparatus according to claim 1 ,
wherein the processor is configured to calculate the correction amount based on pixel values of pixels surrounding the pixel of interest on which color filters of the first color are disposed.

4. The image processing apparatus according to claim 1 ,
wherein the one or more additional pixels are any of pixels adjacent to the pixel of interest in horizontal and vertical directions, pixels adjacent to the pixel of interest in diagonal directions, and pixels away from the pixel of interest by a predetermined number of pixels in the horizontal and vertical directions.

5. The image processing apparatus according to claim 1 ,
wherein the processor is configured to calculate only the correction amount for the pixel of interest on which the color filter of the first color is disposed.

6. The image processing apparatus according to claim 1 ,
wherein the processor is configured to:
perform the correction factor acquiring process to acquire correction factors respectively for light sources that emit light of different wavelength ranges; and
select a correction factor from among the correction factors depending on the light sources; and
calculate the correction amount based on the correction factor selected.

7. The image processing apparatus according to claim 1 ,
wherein the processor is configured to correct the pixel value of the pixel of interest by adding or subtracting the correction amount calculated to or from the pixel value of the pixel of interest.

8. The image processing apparatus according to claim 1 ,
wherein the processor is configured to correct the pixel value of the pixel of interest in moving image data generated continuously by the image sensor, by using the correction amount.

9. The image processing apparatus according to claim 1 ,
wherein the first color is selected from one of red, green, and blue.

10. The image processing apparatus according to claim 1 ,
wherein the first color is selected from one of cyan, magenta, yellow, and green.

11. An image processing method comprising:
performing a correction factor acquiring process comprising:
acquiring image data from an image sensor, the image sensor comprising a pixel of interest in which a color filter of a first color is disposed and one or more additional pixels on which color filters of the first color are disposed;
determining a spectral sensitivity characteristic in a first predetermined wavelength range of the pixel of interest itself;
determining a spectral sensitivity characteristic in the first predetermined wavelength range of each of the one or more additional pixels;
determining a reference spectral sensitivity in the first predetermined wavelength range based on the spectral sensitivity characteristic in the first predetermined wavelength range of the each of the one or more additional pixels;
determining a difference between the spectral sensitivity characteristic of the pixel of interest and the reference spectral sensitivity in the first predetermined wavelength range; and
determining the correction factor for correcting a pixel value in the first predetermined wavelength range of the pixel of interest based on the difference;
calculating a correction amount for correcting the pixel value of the pixel of interest based on the correction factor at the pixel of interest acquired and pixel values of pixels surrounding the pixel of interest; and
correcting the pixel value of the pixel of interest based on the correction amount calculated.

12. A non-transitory computer-readable recording medium with an executable program stored thereon, the executable program causing a computer to at least:
perform a correction factor acquiring process comprising:
acquire image data from an image sensor, the image sensor comprising a pixel of interest in which a color filter of a first color is disposed and one or more additional pixels on which color filters of the first color are disposed;
determine a spectral sensitivity characteristic in a first predetermined wavelength range of the pixel of interest itself;
determine a spectral sensitivity characteristic in the first predetermined wavelength range of each of the one or more additional pixels;
determine a reference spectral sensitivity in the first predetermined wavelength range based on the spectral sensitivity characteristic in the first predetermined wavelength range of the each of the one or more additional pixels;
determine a difference between the spectral sensitivity characteristic of the pixel of interest and the reference spectral sensitivity in the first predetermined wavelength range; and
determine the correction factor for correcting a pixel value in the first predetermined wavelength range of the pixel of interest based on the difference;

calculate a correction amount for correcting the pixel value of the pixel of interest based on the correction factor at the pixel of interest acquired and pixel values of pixels surrounding the pixel of interest; and
correct the pixel value of the pixel of interest based on the correction amount calculated.

Assignees

• Olympus Corp

Inventors

• Ichikawa Manabu
• Maruyama Hiroki

Classifications

• H04N9/646 Primary

  for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters · CPC title

• H04N1/6041

  for controlling uniformity of color across image area · CPC title

• H04N25/671

  for non-uniformity detection or correction · CPC title

• H04N23/12

  with one sensor only · CPC title

• H04N23/84

  for processing colour signals · CPC title