Back to results
US 8,804,013 B2Granted
Method of calculating lens shading compensation factor and method and apparatus for compensating for lens shading by using the method
AssigneeLG Innotek Co., Ltd.
InventorsSoo Jin Park, Deepak Chandra Bijalwan, Raghubansh B. Gupta
Life of this patent
Estimating the term…
Abstract
Provided is a method of calculating a compensation factor to compensate for lens shading due to the characteristics of an image capturing device, which requires a small amount of memory. A reference image is captured, and a compensation factor is calculated using the characteristics of a lens shading pattern of the captured reference image. A distribution of pixel values is approximated using an exponential spline function, and a compensation factor is calculated using the approximated distribution. In addition, a method and an apparatus for compensating for lens shading by using a calculated compensation factor are provided.
Claims17
A lens shading compensation factor calculating method comprising:
- obtaining a reference image;
- dividing the reference image into division images according to channels;
- dividing the division images into circular sectors;
- extracting a plurality of samples from pixels of the division images;
- fitting a distribution of pixel values of the division images to a three-dimensional sphere polynomial in an xyz space, based on the samples;
- extracting a maximum pixel value based on x and y coordinate values having a maximum z value from the three-dimensional sphere polynomial;
- determining a mean pixel value of each of the circular sectors using the three-dimensional sphere polynomial;
- and
- calculating a compensation factor of each of the circular sectors based on the maximum pixel value and the mean pixel value.
6 more elements
A lens shading compensation method comprising:
- capturing an image;
- dividing the captured image into division images according to channels;
- dividing the division images into circular sectors;
- multiplying each of the circular sectors by a compensation factor determined according to the circular sector;
- and
- integrating the division images,
- wherein the compensation factor is calculated by obtaining a reference image, dividing the reference image into division images according to channels, dividing the division images into circular sectors, extracting a plurality of samples from pixels of the division images, fitting a distribution of pixel values of the division images to a three-dimensional sphere polynomial in an xyz space, based on the samples, extracting a maximum pixel value based on x and y coordinate values having a maximum z value from the three-dimensional sphere polynomial, determining a mean pixel value of each of the circular sectors using the three-dimensional sphere polynomial, and using the maximum pixel value and the mean pixel value.
4 more elements
A lens shading compensation apparatus comprising:
- an image capturing device configured to obtain an image;
- an image capturing part performing a predetermined image processing process on the obtained image and transmitting the image;
- and
- a lens shading compensation part dividing the image transmitted from the image capturing part into division images according to color channels, dividing the division images into circular sectors, and multiplying each of circular sectors by a compensation factor determined according to the circular sector;
- and integrating the division images after the multiplying of the circular sectors;
- wherein the compensation factor is calculated by obtaining a reference image, dividing the reference image into division images according to channels, dividing the division images into circular sectors, extracting a plurality of samples from pixels of the division images, fitting a distribution of pixel values of the division images to a three-dimensional sphere polynomial in an xyz space, based on the samples, extracting a maximum pixel value based on x and y coordinate values having a maximum z value from the three-dimensional sphere polynomial, determining a mean pixel value of each of the circular sectors using the three-dimensional sphere polynomial, and using the maximum pixel value and the mean pixel value.
3 more elements
A lens shading compensation factor calculating method comprising:
- obtaining a reference image;
- dividing the reference image into division images according to channels;
- determining sample pixels from each of the division images;
- fitting a two dimensional exponential spline function to each of the division images by using pixel values of the sample pixels;
- adjusting one of a coefficient and an order of the two dimensional exponential spline function to calculate a distribution of brightness values of each of the division images;
- and
- calculating a compensation factor based on the two dimensional exponential spline function;
- wherein the compensation factor is calculated using the following Equation:
- Compensation factor=(maximum pixel value of each division image)/(pixel value of each pixel calculated from distribution of pixel values).
6 more elements
A lens shading compensation method comprising:
- capturing an image;
- dividing the captured image into division images according to channels;
- multiplying each of the division images by a compensation factor calculated using a two dimensional exponential spline function;
- and
- integrating the division images;
- wherein the compensation factor is calculated using the following Equation:
- compensation factor=(maximum pixel value of each division image)/(pixel value of each pixel calculated from distribution of pixel values).
4 more elements
A lens shading compensation apparatus comprising:
- an image capturing device configured to obtain an image;
- an image capturing part performing a predetermined image processing process on the obtained image and transmitting the image;
- and
- a lens shading compensation part dividing the image transmitted from the image capturing part into division images according to channels, multiplying each of the division images by a compensation factor calculated using a two dimensional exponential spline function, and integrating the division images;
- wherein the compensation factor is calculated using the following Equation:
- compensation factor=(maximum pixel value of each division image)/(pixel value of each pixel calculated from distribution of pixel values).
3 more elements
Dependencies are inferred from the claim text.