Distortion-corrected image generation unit and distortion-corrected image generation method

• US 7,965,325 B2
• Filed: 10/22/2008
• Issued: 06/21/2011
• Est. Priority Date: 12/04/2007
• Status: Active Grant

• Current Assignee: Alpine Electronics Incorporated (Alps Alpine Co., Ltd.)
• Original Assignee: Alpine Electronics Incorporated (Alps Alpine Co., Ltd.)
• Inventors: Imamura, Kosuke
• Primary Examiner(s): Ye; Lin
• Assistant Examiner(s): Camargo; Marly
• Application Number:
  US12/255,932
• Publication Number:
  US 20090141148A1
• Time in Patent Office: 972 Days
• Field of Search: 348/241, 348/243, 348/360, 348/335, 348/246, 359/637, 359/16, 396/79, 396/80, 382/254, 382/255, 382/274, 382/275
• US Class Current: 348/246
• CPC Class Codes: G06T 3/12 Panospheric to cylindrical image transformations
• CPC Class Codes: G06T 5/80 Geometric correction
• CPC Class Codes: H04N 23/81 for suppressing or minimising disturbance in the image signal generation
• CPC Class Codes: H04N 25/61 the noise originating only from the lens unit, e.g. flare, shading, vignetting or "cos4"

Abstract

An internal parameter storage unit stores, in advance, a plurality of sets of internal parameters each of which can be applied to correct a pixel position in a direction from an image principal point, i.e., a plurality of sets of internal parameters for accommodating errors of different magnitudes that occur in individual directions from an image principal point. An internal parameter selection unit selects a set of internal parameters from the plurality of sets of internal parameters stored in advance on the basis of the direction of a pixel position to be corrected from the image principal point, and a distortion-corrected image generator corrects distortion on the basis of the selected set of internal parameters, so that, even when a surface of a lens is not exactly parallel to a surface of an image pickup device, distortion is corrected more accurately.

Claims

1. A distortion-corrected image generation unit that generates a distortion-corrected image by correcting distortion of a distorted image captured using a fish-eye lens, the distortion-corrected image generation unit comprising:

a distorted image acquisition unit that obtains the distorted image;

an internal parameter storage unit that stores a plurality of sets of internal parameters, related to the fish-eye lens, each of the sets being applied to correct a pixel position in a radially extending direction from an image principal point of the distorted image;

an internal parameter selection unit that selects, on the basis of a radial direction of a pixel position to be corrected in the distorted image obtained by the distorted image acquisition unit from the image principal point, one set of internal parameters to be applied to correct the pixel position to be corrected from the plurality of sets of internal parameters stored in the internal parameter storage unit; and

a distortion-corrected image generator that generates the distortion-corrected image from the distorted image by replacing a pixel value at the pixel position to be corrected with a pixel value at another pixel position on the basis of the set of internal parameters selected by the internal parameter selection unit.

2. The distortion-corrected image generation unit according to claim 1, further comprising:

an output region information storage unit that stores output region information that represents an output region to be externally output, out of regions of the distorted image,

wherein the internal parameter selection unit refers to the output region information stored in the output region information storage unit and determines, as the pixel position to be corrected, a pixel position in the output region indicated by the output region information.

3. The distortion-corrected image generation unit according to claim 1, wherein the internal parameter storage unit stores the plurality of sets of internal parameters in association with radial line identification information identifying a plurality of lines that radially extend from the image principal point and divide an entire region of the distorted image.

4. The distortion-corrected image generation unit according to claim 3, wherein the internal parameter selection unit selects, as a set of internal parameters to be applied to correct the pixel position to be corrected, one set of internal parameters associated with the radial line identification information identifying a radial line, the distance between the radial line and the pixel position to be corrected being shortest.

5. The distortion-corrected image generation unit according to claim 3, further comprising:

an internal parameter calculation unit that calculates a new set of internal parameters by obtaining weighted averages of a plurality of sets of internal parameters,

wherein the internal parameter selection unit selects, as sets of internal parameters to be applied to correct the pixel position to be corrected, a first set of internal parameters associated with the radial line identification information identifying a radial line, the distance between the radial line and the pixel position to be corrected being shortest, and a second set of internal parameters associated with the radial line identification information identifying a radial line, the distance between the radial line and the pixel position to be corrected being second shortest,

the internal parameter calculation unit calculates a new set of internal parameters by obtaining weighted averages of the first and second sets of internal parameters selected by the internal parameter selection unit, and

the distortion-corrected image generator generates the distortion-corrected image from the distorted image on the basis of the new set of internal parameters calculated by the internal parameter calculation unit instead of the first and second sets of internal parameters selected by the internal parameter selection unit.

6. The distortion-corrected image generation unit according to claim 3, further comprising:

an internal parameter calculation unit that calculates a new set of internal parameters by obtaining weighted averages of a plurality of sets of internal parameters; and

an image height determination unit that determines whether an image height that represents distance between the pixel position to be corrected and the image principal point is less than a predetermined value,

wherein, when the image height determination unit determines that the image height is less than the predetermined value, the internal parameter selection unit selects, as a set of internal parameters to be applied to correct the pixel position to be corrected, a first set of internal parameters associated with the radial line identification information identifying a radial line, the distance between the radial line and the pixel position to be corrected being shortest, and when the image height determination unit determines that the image height is equal to or more than the predetermined value, the internal parameter selection unit selects, as sets of internal parameters to be applied to correct the pixel position to be corrected, the first set of internal parameters and a second set of internal parameters associated with the radial line identification information identifying a radial line, the distance between the radial line and the pixel position to be corrected being second shortest,

when the first and second sets of internal parameters are selected, the internal parameter calculation unit calculates a new set of internal parameters by obtaining weighted averages of the first and second sets of internal parameters selected by the internal parameter selection unit, and

when the internal parameter calculation unit calculates the new set of internal parameters, the distortion-corrected image generator generates the distortion-corrected image from the distorted image on the basis of the new set of internal parameters calculated by the internal parameter calculation unit instead of the first and second sets of internal parameters selected by the internal parameter selection unit.

7. The distortion-corrected image generation unit according to claim 1, wherein the internal parameter storage unit stores the plurality of sets of internal parameters in association with region identification information for identifying a plurality of divided regions into which an entire region of the distorted image is divided and that radially extend from the image principal point.

8. The distortion-corrected image generation unit according to claim 7, wherein the internal parameter selection unit selects, as a set of internal parameters to be applied to correct the pixel position to be corrected, one set of internal parameters associated with the region identification information identifying a divided region that includes the pixel position to be corrected.

9. The distortion-corrected image generation unit according to claim 1, further comprising:

a selectability information storage unit that stores selectability information that represents relationships between correction levels for correcting distortion of the distorted image and sets of internal parameters that can be selected for correcting the distortion at the respective correction levels;

a correction level reception unit that receives a correction level; and

a correction level storage unit that stores the correction level received by the correction level reception unit,

wherein the internal parameter selection unit refers to the correction level stored in the correction level storage unit and the selectability information stored in the selectability information storage unit and selects one set of internal parameters to be applied to correct the pixel position to be corrected at the correction level stored in the correction level storage unit from the sets of internal parameters, which can be selected for correcting the distortion.

10. A method for generating a distortion-corrected image by correcting distortion of a distorted image captured using a fish-eye lens, the method comprising:

obtaining the distorted image;

when the distorted image is obtained, referring to an internal parameter storage unit that stores a plurality of sets of internal parameters, related to the fish-eye lens, each of the sets being applied to correct a pixel position in a radially extending direction from an image principal point of the distorted image, and selecting, on the basis of a radial direction of a pixel position to be corrected in the distorted image from the image principal point, one set of internal parameters to be applied to correct the pixel position to be corrected from the plurality of sets of internal parameters stored in the internal parameter storage unit; and

when the set of internal parameters is selected, generating the distortion-corrected image from the distorted image by replacing a pixel value at the pixel position to be corrected with a pixel value at another pixel position on the basis of the selected set of internal parameters.

11. The distortion-corrected image generation method according to claim 10, further comprising:

providing an output region information storage method that stores output region information that represents an output region to be externally output, out of regions of the distorted image,

wherein the internal parameter selection act refers to the output region information stored in the output region information storage unit and determines, as the pixel position to be corrected, a pixel position in the output region indicated by the output region information.

12. The distortion-corrected image generation method according to claim 10, wherein the internal parameter storage unit stores the plurality of sets of internal parameters in association with radial line identification information identifying a plurality of lines that radially extend from the image principal point and divide an entire region of the distorted image.

13. The distortion-corrected image generation method according to claim 12, wherein the internal parameter selection act selects, as a set of internal parameters to be applied to correct the pixel position to be corrected, one set of internal parameters associated with the radial line identification information identifying a radial line, the distance between the radial line and the pixel position to be corrected being shortest.

14. The distortion-corrected image generation method according to claim 12, further comprising:

an internal parameter calculation act that calculates a new set of internal parameters by obtaining weighted averages of a plurality of sets of internal parameters,

wherein the internal parameter selection act selects, as sets of internal parameters to be applied to correct the pixel position to be corrected, a first set of internal parameters associated with the radial line identification information identifying a radial line, the distance between the radial line and the pixel position to be corrected being shortest, and a second set of internal parameters associated with the radial line identification information identifying a radial line, the distance between the radial line and the pixel position to be corrected being second shortest,

the internal parameter calculation act calculates a new set of internal parameters by obtaining weighted averages of the first and second sets of internal parameters selected by the internal parameter selection act, and

the method generates the distortion-corrected image from the distorted image on the basis of the new set of internal parameters calculated by the internal parameter calculation act instead of the first and second sets of internal parameters selected by the internal parameter selection act.

15. The distortion-corrected image generation method according to claim 12, further comprising:

an internal parameter calculation act that calculates a new set of internal parameters by obtaining weighted averages of a plurality of sets of internal parameters; and

an image height determination act that determines whether an image height that represents distance between the pixel position to be corrected and the image principal point is less than a predetermined value,

wherein, when the image height determination act determines that the image height is less than the predetermined value, the internal parameter selection act selects, as a set of internal parameters to be applied to correct the pixel position to be corrected, a first set of internal parameters associated with the radial line identification information identifying a radial line, the distance between the radial line and the pixel position to be corrected being shortest, and when the image height determination act determines that the image height is equal to or more than the predetermined value, the internal parameter selection act selects, as sets of internal parameters to be applied to correct the pixel position to be corrected, the first set of internal parameters and a second set of internal parameters associated with the radial line identification information identifying a radial line, the distance between the radial line and the pixel position to be corrected being second shortest,

when the first and second sets of internal parameters are selected, the internal parameter calculation act calculates a new set of internal parameters by obtaining weighted averages of the first and second sets of internal parameters selected by the internal parameter selection act, and

when the internal parameter calculation act calculates the new set of internal parameters, the method generates the distortion-corrected image from the distorted image on the basis of the new set of internal parameters calculated by the internal parameter calculation act instead of the first and second sets of internal parameters selected by the internal parameter selection act.

16. The distortion-corrected image generation method according to claim 10, wherein the internal parameter storage unit stores the plurality of sets of internal parameters in association with region identification information for identifying a plurality of divided regions into which an entire region of the distorted image is divided and that radially extend from the image principal point.

17. The distortion-corrected image generation method according to claim 16, wherein the internal parameter selection act selects, as a set of internal parameters to be applied to correct the pixel position to be corrected, one set of internal parameters associated with the region identification information identifying a divided region that includes the pixel position to be corrected.

18. The distortion-corrected image generation method according to claim 10, further comprising:

providing a selectability information storage unit that stores selectability information that represents relationships between correction levels for correcting distortion of the distorted image and sets of internal parameters that can be selected for correcting the distortion at the respective correction levels;

a correction level reception act that receives a correction level; and

providing a correction level storage unit that stores the correction level received by the correction level reception act,

wherein the internal parameter selection act refers to the correction level stored in the correction level storage unit and the selectability information stored in the selectability information storage unit and selects one set of internal parameters to be applied to correct the pixel position to be corrected at the correction level stored in the correction level storage unit from the sets of internal parameters, which can be selected for correcting the distortion.