Distortion correction method, distortion correction apparatus, and image pickup apparatus

Patent metadata

Field	Value
Publication number	US-10908416-B2
Application number	US-201815958463-A
Country	US
Kind code	B2
Filing date	Apr 20, 2018
Priority date	Apr 21, 2017
Publication date	Feb 2, 2021
Grant date	Feb 2, 2021

Abstract

Provided is a distortion correction method for an image pickup mode in which an image pickup is performed with an image pickup area, whose diagonal length is Ib, of an image pickup element which receives light from an optical system, an expression, 1.05<Ia/Ib, being satisfied in a case where a distortion correction is not performed, where Ia represents a diagonal length of an effective pixel area of the image pickup element, wherein distortion correction is performed for an image having a positive distortion so that image information positioned at an image height of Ic/2 is positioned at an image height of Ib/2, and so that a conditional expression, 1.0<Ic/Ib, is satisfied.

First claim

What is claimed is:

1. A distortion correction method of correcting distortion, where Ia represents a diagonal length of an effective pixel area of an image pickup element that receives light from an optical system, Ic represents a diagonal length of a first area, which is inside the effective pixel area, of the image pickup element, and Ib represents a diagonal length of a second area, which is inside the first area, of the image pickup element, the distortion correction being performed to obtain image data corresponding to the second area of the image pickup element, the distortion correction being performed to obtain image data corresponding to the second area for an image pickup mode, the method comprising:
satisfying a conditional expression 1.05<Ia/Ib; and
satisfying a conditional expression 1.0<Ic/Ib to correct distortion for data of an image having a positive distortion so that image information corresponding to an image height of Ic/2 becomes image information corresponding to an image height of Ib/2.

2. The distortion correction method according to claim 1 , wherein the obtained image data is motion image data.

3. The distortion correction method according to claim 1 , wherein the optical system does not include an extender.

4. The distortion correction method according to claim 1 , further comprising satisfying a conditional expression 0.90<Ie/Ia, where Ie represents a diameter of an effective image circle of the optical system.

5. The distortion correction method according to claim 1 , wherein the distortion correction is performed for data of an image having a positive distortion to generate image information corresponding to an image height of y based on image information corresponding to an image height of x, which is smaller than y, in a mode where an image pickup is performed with an image pickup area of the image pickup element at a resolution higher than that in the image pickup mode.

6. The distortion correction method according to claim 1 , wherein the distortion correction is performed in a case where an amount of light at a periphery of an image circle satisfies an allowable condition thereof.

7. A distortion correction apparatus comprising:
an image processor configured to correct distortion, where Ia represents a diagonal length of an effective pixel area of an image pickup element that receives light from an optical system, Ic represents a diagonal length of a first area, which is inside the effective pixel area, of the image pickup element, and Ib represents a diagonal length of a second area, which is inside the first area, of the image pickup element, the distortion correction being performed to obtain image data corresponding to the second area of the image pickup element, to obtain image data corresponding to the second area for an image pickup mode,
wherein the image processor, during the distortion correction:
satisfies a conditional expression 1.05<Ia/Ib; and
satisfies a conditional expression 1.0<Ic/Ib to correct distortion for data of an image having a positive distortion so that image information corresponding to an image height of Ic/2 becomes image information corresponding to an image height of Ib/2.

8. An image pickup apparatus comprising:
a zoom lens including a lens unit closest to an object side and providing a positive refractive power;
an image pickup element configured to pickup an image formed by the zoom lens; and
a distortion correction apparatus comprising:
an image processor configured to correct distortion, where Ia represents a diagonal length of an effective pixel area of an image pickup element that receives light from an optical system, Ic represents a diagonal length of a first area, which is inside the effective pixel area, of the image pickup element, and Ib represents a diagonal length of a second area, which is inside the first area, of the image pickup element, the distortion correction being performed to obtain image data corresponding to the second area of the image pickup element, to obtain image data corresponding to the second area for an image pickup,
wherein the image processor, during the distortion correction:
satisfies an expression 1.05<Ia/Ib; and
satisfies a conditional expression 1.0<Ic/Ib to correct distortion for data of an image having a positive distortion so that image information corresponding to an image height of Ic/2 becomes image information corresponding to an image height of Ib/2.

9. The image pickup apparatus according to claim 8 , wherein following conditional expressions are further satisfied:
36.0°<arctan {( Ia/ 2)/ fw}; and

4.0< z,
where fw represents a focal length of the zoom lens at a wide angle end, and z represents a zoom ratio of the zoom lens.

10. The image pickup apparatus according to claim 8 , wherein the zoom lens is interchangeable with another zoom lens including a lens unit closest to an object side and providing a positive refractive power.

11. A distortion correction method of correcting distortion, wherein conditional expressions
1.05<Ia/Ib; and 1.0<Ic/lb are satisfied, where la represents a diagonal length of an effective pixel area of an image pickup element, the image pickup element receiving light from an optical system, Ic represents a diagonal length of a first area, which is in the effective pixel area, of the image pickup element, and lb represents a diagonal length of a second area, which is in the first area, of the image pickup element,
wherein the method obtains image data corresponding to the second area of the image pickup element by correcting distortion for data of an image having a positive distortion so that image information corresponding to an image height of Ic/2 becomes image information corresponding to an image height of lb/2.

12. A distortion correction apparatus comprising:
an image processor configured to correct distortion; and
a memory configured to store information used by the image processor,
wherein conditional expressions
1.05<Ia/Ib; and
1.0<Ic/lb are satisfied, where la represents a diagonal length of an effective pixel area of an image pickup element, the image pickup element receiving light from an optical system, Ic represents a diagonal length of a first area, which is in the effective pixel area, of the image pickup element, and lb represents a diagonal length of a second area, which is in the first area, of the image pickup element,

wherein the processor is configured to obtain image data corresponding to the second area of the image pickup element by correcting distortion for data of an image having a positive distortion so that image information corresponding to an image height of Ic/2 becomes image information corresponding to an image height of lb/2.

13. An image pickup apparatus comprising:
a distortion correction apparatus of claim 12 ; and
the image pickup element configured to pick up an image formed by the optical system.

14. The image pickup apparatus according to claim 13 , further comprising the optical system.

Assignees

• Canon Kk

Inventors

• Miyazawa Nobuyuki

Classifications

• H04N25/61

  the noise originating only from the lens unit, e.g. flare, shading, vignetting or "cos4" · CPC title

• H04N23/698

  for achieving an enlarged field of view, e.g. panoramic image capture · CPC title

• H04N23/69

  Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming · CPC title

• G02B15/145 Primary

  having five groups only · CPC title

• G02B27/0037 Primary

  with diffracting elements (G02B27/0056 takes precedence; holographic optical elements G02B5/32; zone systems G02B5/1876) · CPC title