Method of correcting image distortion and apparatus for processing image using the method

• US 8,000,559 B2
• Filed: 08/27/2008
• Issued: 08/16/2011
• Est. Priority Date: 08/27/2007
• Status: Expired due to Fees

• Current Assignee: Synergy Innovation Co., Ltd.
• Original Assignee: Synergy Innovation Co., Ltd.
• Inventors: Kwon, Sung Jin
• Primary Examiner(s): Ye; Lin
• Assistant Examiner(s): CHEN, CHIA WEI A
• Application Number:
  US12/199,191
• Publication Number:
  US 20090059041A1
• Time in Patent Office: 1,084 Days
• Field of Search: 348/222.1, 348/241, 382/276
• US Class Current: 382/276
• CPC Class Codes: H04N 23/81 for suppressing or minimising disturbance in the image signal generation

Abstract

A method of correcting image distortion and an apparatus for processing an image using the method are provided, where the method can overcome the disadvantages of the conventional methods of correcting lens distortion and can minimize image quality degradation at outer portions,. The method includes: receiving an image from a wide-angle lens; extracting a distortion coefficient of the distortion in the image caused by the wide-angle lens; correcting the distortion of the image by using the extracted distortion coefficient; and displaying a corrected image. The apparatus includes: a wide-angle lens for receiving an image; an image processing unit comprising a distortion coefficient extracting unit for extracting a distortion coefficient of distortion in the image caused by the wide-angle lens and a distortion correcting unit for correcting the distortion of the image using the extracted distortion coefficient; and a display unit for displaying a corrected image.

Claims

1. A method of correcting image distortion, the method comprising:

receiving an image with a distortion from a wide-angle lens;

extracting a distortion coefficient for the image with the distortion caused by the wide-angle lens;

correcting the distortion of the image using the extracted distortion coefficient;

wherein the step of correcting the distortion comprises fitting a curve at outer portions of the corrected image in order to reduce blurring at outer portions of the corrected image;

wherein the step of fitting the curve comprises selecting a plurality of points based on an inflection point in an R_C-R_D graph and fitting the curve using the selected plurality of points;

wherein R_C is a distance from a predetermined point to an origin of a coordinate system of the corrected image, and R_D is a distance from a predetermined point to the origin of a coordinate system of the image with the distortion, and

displaying the corrected image.

2. The method of claim 1, wherein the wide-angle lens comprises a fish-eye lens having a viewing angle of less than 120°

.

3. The method of claim 1, wherein the step of extracting the distortion coefficient comprises manually obtaining the distortion coefficient within a predefined range using a lens distortion model.

4. The method of claim 3, wherein the step of correcting the distortion comprises correcting the distortion of the image through backward mapping using the extracted distortion coefficient.

5. The method of claim 3, wherein the lens distortion model is given as follows:

R_C, a distance from a predetermined point to an origin of a coordinate system of the corrected image, is equal to R_D, a distance from a predetermined point to an origin of a coordinate system of the image with the distortion, plus the cube of R_D;

wherein a coefficient of the cube of R_D is a distortion coefficient k, and the distortion coefficient k is greater than 0 and is equal to or less than (a−

1) divided by R_DM, and

wherein R_DM is a maximum distance from the origin of the coordinate system of the image with the distortion to an outermost point of the image with the distortion, and a is a constant greater than 2.

6. The method of claim 5, wherein the step of correcting the distortion comprises correcting a radial distortion using the extracted distortion coefficient.

7. The method of claim 6, wherein the step of correcting the distortion comprises removing jagged-edge artifacts using bilinear interpolation.

8. The method of claim 1, wherein the fitting the curve at the outer portions is performed using a cubic equation.

9. An apparatus for processing an image, the apparatus comprising:

a wide-angle lens for receiving an image;

an image processing unit comprising;

a distortion coefficient extracting unit for extracting a distortion coefficient of a distortion caused in the image by the wide-angle lens, and

a distortion correcting unit for correcting the distortion of the image using the extracted distortion coefficient to produce a corrected image;

wherein the image processing unit further comprises a curve fitting unit for fitting a curve at outer portions of the corrected image in order to reduce blurring;

wherein the curve fitting unit selects a plurality of points based on an inflection point in an R_C-R_D graph and fits the curve at the outer portions using a cubic equation;

wherein R_C is a distance from a predetermined point to an origin of a coordinate system of the corrected image, and R_D is a distance from a predetermined point to the origin of a coordinate system of the image with the distortion, and

a display unit displaying the corrected image.

10. The apparatus of claim 9, wherein the wide-angle lens comprises a fish-eye lens having a viewing angle of less than 120°

.

11. The apparatus of claim 9, wherein the distortion coefficient extracting unit obtains the distortion coefficient within a predefined range using a lens distortion model.

12. The method of claim 11, wherein the lens distortion model is given as follows:

R_C, a distance from a predetermined point to an origin of a coordinate system of the corrected image, is equal to R_D, a distance from a predetermined point to an origin of a coordinate system of the image with the distortion, plus the cube of R_D;

wherein a coefficient of the cube of R_D is a distortion coefficient k, and the distortion coefficient k is greater than 0 and is equal to or less than (a−

1) divided by R_DM, and

wherein R_DM is a maximum distance from the origin of the coordinate system of the image with the distortion to an outermost point of the image with the distortion, and a is a constant greater than 2.

13. The apparatus of claim 12, wherein the distortion correcting unit corrects a radial distortion caused by the wide-angle lens through backward mapping using the distortion coefficient.

14. The apparatus of claim 13, wherein the distortion correcting unit removes jagged-edge artifacts using a bilinear interpolation.