Correction of optical distortion by image processing

• US 7,529,424 B2
• Filed: 04/30/2004
• Issued: 05/05/2009
• Est. Priority Date: 05/02/2003
• Status: Expired due to Fees

• Current Assignee: Grandeye Limited (Oncam Global Group AG)
• Original Assignee: Grandeye Limited (Oncam Global Group AG)
• Inventors: Ahiska, Yavuz
• Primary Examiner(s): Wu; Jingge
• Assistant Examiner(s): Torres; Jose M
• Application Number:
  US10/837,012
• Publication Number:
  US 20050007477A1
• Time in Patent Office: 1,831 Days
• Field of Search: 382/254, 382/275, 348/335
• US Class Current: 382/275
• CPC Class Codes: H04N 23/62 Control of parameters via user interfaces
• CPC Class Codes: H04N 23/698 for achieving an enlarged field of view, e.g. panoramic image capture
• CPC Class Codes: H04N 23/81 for suppressing or minimising disturbance in the image signal generation

Abstract

An optical system comprising the following. A camera that is capable of reducing distortion from an optical system has an optical system that is configured to capture a wide field of view of a subject. An image sensor and circuitry are coupled to the optical system and are configured to convert the output of the optical system to electrical signals suitable for use by an image processing circuit. The image processing circuit is coupled to the image sensor and is configured to reduce optical distortions from the combination of the optical system and the image sensor where the correction includes reference to a table of parameters held in a solid-state memory, attached to said image processing circuit, wherein the table of parameters may be specific to the particular combination of said optical system and said image.

Claims

1. A camera having reduced distortion from an optical system comprising:

a) an optical system which captures a wide field of view;

b) an image sensor which captures a sensed image of said wide field of view through said optical system, and circuitry coupled to said image sensor and configured to convert the output of the image sensor to electrical signals suitable for use by an image processing circuit;

c) the image processing circuit coupled to the image sensor and configured to provide a correction which reduces optical distortions from the combination of the optical system and the image sensor where the correction includes reference to a table of parameters held in a solid-state memory, attached to said image processing circuit, wherein the table of parameters are specific to the particular combination of said optical system and said image sensor; and

d) wherein said table maps an individual pixel of a corrected output image to an accurate coordinate in the captured sensed image, wherein pixel values within a local neighborhood of the sensed image are used to provide a weighted sum which provides an estimate of the value at the said accurate coordinate on the sensed image, wherein the weight of each pixel within the local neighborhood is determined by its distance from the accurate coordinate provided by the table.

2. The camera of claim 1 in which the table of parameters has missing entries that are interpolated by the image processing circuit.

3. The camera of claim 1 in which the table of parameters is generated by photographing a test pattern through the optical system to be corrected and applying image processing operations to automatically produce the table of parameters.

4. The camera of claim 3 further comprising:

points of attachment coupled to the optical system and configured to support the test pattern.

5. The camera of claim 1 in which the table of parameters is generated by photographing a test pattern through the optical system to be corrected and manually constructing the table of parameters.

6. The camera of claim 5 further comprising:

points of attachment coupled to the optical system and configured to support the test pattern.

7. The camera of claim 1 wherein a plurality of tables of parameters are available to correct distortion for different focal lengths of the optical system, wherein an unrepresented focal length may be corrected by interpolating between some of the plurality of tables of parameters.

8. The camera of claim 1 wherein a plurality of tables of parameters are available to correct distortion for different apertures of the optical system, wherein an unrepresented aperture may be corrected by interpolating between some of the plurality of tables of parameters.

9. The camera of claim 1 wherein a plurality of tables of parameters are stored in the camera.

10. A camera with adjustable image projection distortion correction comprising:

a) an adjustable optical lens system which produces projection with variable optical geometric distortion;

b) an image sensor and circuitry coupled to the adjustable optical lens system and configured to convert the output of said adjustable optical system to electrical signals suitable for use by an image processing circuit;

c) said image processing circuit coupled to the image sensor and configured to provide a correction of said optical geometric distortion where said correction includes using multiple geometric distortion parameters to correct optical distortion that varies according to changes in the projection from said adjustable projection optical lens system onto said image sensor and said parameters automatically selected to adjust said projection and unrepresented projections corrected by interpolating between parameters;

d) said multiple parameters used for correction held in solid-state memory within the housing of said adjustable projection optical lens system, and said image processing circuit; and

e) an individual pixel created using a weighted sum of a selected group of pixels to be used in said correction, a part of each selected pixel of said group of pixels making up the individual pixel and the group of pixels are proximate to the individual pixel, wherein the weight of each pixel of said group of pixels is determined by its distance from the individual pixel based on their relative coordinates derived from the geometric distortion parameter correction.

11. The camera of claim 10 in which a plurality of tables are configured with multiple geometric distortion parameters to be used to correct optical geometric distortion that varies according to one or more parameters of said optical system, said tables to be automatically selected as said parameter varies and unrepresented parameters corrected by interpolating between said tables.

12. A camera with reduced optical distortion comprising:

a) a detachable optical lens system which captures an ultra-wide field of view;

b) an image sensor and circuitry coupled to the optical system and configured to convert the output of said optical system to electrical signals suitable for use by an image processing circuit;

c) said image processing circuit coupled to the image sensor and configured to provide a correction which reduces optical distortions introduced by the combination of said optical lens system and said image sensor where said correction includes reference to a table of parameters;

d) said table of parameters held in a solid-state memory coupled to and within the housing of said detachable optical lens system, said image processing circuit gaining access to said parameters on attachment of said optical lens system to said camera, wherein the table maps an individual pixel of a corrected image to an accurate coordinate in a sensed captured image, wherein pixel values within a selected group are in a local neighborhood and are used to provide a weighted sum to provide an estimate of the value at the said accurate coordinate on the sensed image, wherein the weight of each pixel within the selected group is determined by its distance from the accurate coordinate as provided by the table.

13. The camera of claim 12 in which the table of parameters has missing entries that are interpolated by the image processing circuit.

14. The camera of claim 12 in which the table of parameters is generated by photographing a test pattern through the optical system to be corrected and applying image processing operations to automatically produce the table of parameters.

15. The camera of claim 14 further comprising:

points of attachment coupled to the optical system and configured to support the test pattern.

16. The camera of claim 12 in which the table of parameters is generated by photographing a test pattern through the optical system to be corrected and manually constructing the table of parameters.

17. The camera of claim 16 further comprising:

points of attachment coupled to the optical system and configured to support the test pattern.

18. The camera of claim 12 wherein a plurality of tables of parameters are available to correct distortion for different focal lengths of the optical system, wherein an unrepresented focal length may be corrected by interpolating between some of the plurality of tables of parameters.

19. The camera of claim 12 wherein a plurality of tables of parameters are available to correct distortion for different apertures of the optical system, wherein an unrepresented aperture may be corrected by interpolating between some of the plurality of tables of parameters.

20. A method of reducing geometric distortion in an optical system comprising:

a) capturing a distorted image of a known test pattern through said optical system;

b) automatically defining a mapping between said distorted image of said test pattern and an undistorted test pattern;

c) constructing a table of mapping information in a form suitable for use by an image processing circuit; and

d) using said image-processing circuit to apply said table to images subsequently or previously captured through said optical systems;

wherein said table maps an individual pixel of a corrected output image to an accurate coordinate in the captured image, wherein pixel values within a local neighborhood are used to provide a weighted sum which provides an estimate of the value at the said accurate coordinate on the captured image, wherein the weight of each pixel within the local neighborhood is determined by its distance from the accurate coordinate as provided by the table.