Detecting control points for camera calibration

Patent metadata

Field	Value
Publication number	US-9319666-B1
Application number	US-201313908565-A
Country	US
Kind code	B1
Filing date	Jun 3, 2013
Priority date	Jun 3, 2013
Publication date	Apr 19, 2016
Grant date	Apr 19, 2016

Abstract

A device is configured to receive an image including a calibration pattern and apply a filter to the image based on a first coordinate plane. The device is configured to determine a first set of response peaks associated with the calibration pattern based on applying the filter, the first set of response peaks being associated with a set of control points and a set of boundary points. The device is configured to determine a second set of response peaks associated with the calibration pattern based on a second coordinate plane and a third coordinate plane, the second set of response peaks being associated with the boundary points. The device is configured to determine the control points based on determining the first set of response peaks and the second set of response peaks, and provide information that identifies the control points.

First claim

What is claimed is:

1. A device, comprising:
one or more processors to:
receive an image including a calibration pattern;
apply a cross derivative filter to the image based on a first coordinate plane,
the cross derivative filter including a cross derivative of a Gaussian function;

determine a first plurality of response peaks associated with the calibration pattern based on applying the cross derivative filter,
the first plurality of response peaks being associated with a plurality of control points associated with the calibration pattern and a plurality of boundary points associated with the calibration pattern,
the plurality of boundary points being points along an edge of the calibration pattern;

determine a second plurality of response peaks associated with the calibration pattern based on applying a first filter, including a derivative of the Gaussian function based on a second coordinate plane, and applying a second filter, including a derivative of the Gaussian function based on a third coordinate plane,
the second plurality of response peaks being associated with the plurality of boundary points;

determine the plurality of control points based on removing the second plurality of response peaks, associated with the plurality of boundary points, from the first plurality of response peaks; and
provide information that identifies the plurality of control points.

2. The device of claim 1 , where the second coordinate plane is rotated substantially forty-five degrees clockwise from the first coordinate plane; and
where the third coordinate plane is rotated substantially forty-five degrees counter-clockwise from the first coordinate plane.

3. The device of claim 1 , where the calibration pattern includes a checkerboard pattern of a plurality of squares;
where a control point, of the plurality of control points, includes a point where two squares, of the plurality of squares, having a first tonal contrast, respectively, and two squares, of the plurality of squares, having a second tonal contrast, respectively, share a common border,
the first tonal contrast being lighter than the second tonal contrast; and

where a boundary point, of the plurality of boundary points, includes a point along an edge of the checkerboard pattern.

4. The device of claim 1 , where the one or more processors, when applying the cross derivative filter to the image, are to:
determine an orientation of the calibration pattern; and
determine the first coordinate plane based on the orientation of the calibration pattern.

5. The device of claim 1 , where at least one of the first filter or the second filter includes at least one of:
an x-derivative of a Gaussian function;
a y-derivative of a Gaussian function; or
a linear combination of an x-derivative and a y-derivative.

6. The device of claim 1 , where the one or more processors, when determining the second plurality of response peaks, are to:
determine a first derivative of the image with respect to an x-axis,
the x-axis being associated with a coordinate associated with the first coordinate plane;

determine a second derivative of the image with respect to a y-axis,
the y-axis being associated with another coordinate associated with the first coordinate plane, and
the y-axis being perpendicular to the x-axis;

determine a linear combination of the first derivative and the second derivative based on the second coordinate plane and the third coordinate plane; and
determine the second plurality of response peaks based on the linear combination of the first derivative and the second derivative.

7. The device of claim 1 , where the one or more processors are further to:
determine a camera projection matrix based on the plurality of control points; and
calibrate a camera based on the camera projection matrix.

8. A non-transitory computer-readable medium storing instructions, the instructions comprising:
one or more instructions that, when executed by one or more processors of a device, cause the one or more processors to:
receive an image including a calibration pattern;
apply a cross derivative filter to the image based on a first coordinate plane,
the cross derivative filter including a cross derivative of a Gaussian function;

determine a first plurality of response peaks associated with the calibration pattern based on applying the cross derivative filter,
the first plurality of response peaks being associated with a plurality of control points associated with the calibration pattern and a plurality of boundary points associated with the calibration pattern,
the plurality of boundary points being points along an edge of the calibration pattern;

apply a first oriented filter to the image,
the first oriented filter including a derivative of the Gaussian function based on a second coordinate plane;

apply a second oriented filter to the image,
the second oriented filter including a derivative of the Gaussian function based on a third coordinate plane;

determine a second plurality of response peaks associated with the calibration pattern based on the first oriented filter and the second oriented filter,
the second plurality of response peaks being associated with the plurality of boundary points;

determine the plurality of control points based on removing the second plurality of response peaks, associated with the plurality of boundary points, from the first plurality of response peaks; and
provide information that identifies the plurality of control points.

9. The non-transitory computer-readable medium of claim 8 , where the second coordinate plane is rotated substantially forty-five degrees clockwise from the first coordinate plane; and
where the third coordinate plane is rotated substantially forty-five degrees counter-clockwise from the first coordinate plane.

10. The non-transitory computer-readable medium of claim 8 , where the calibration pattern includes a checkerboard pattern of a plurality of squares;
where a control point, of the plurality of control points, includes a point where two squares, of the plurality of squares, having a first tonal contrast, respectively, and two squares, of the plurality of squares, having a second tonal contrast, respectively, share a common border,
the first tonal contrast being lighter than the second tonal contrast; and

where a boundary point, of the plurality of boundary points, includes a point along an edge of the checkerboard pattern.

11. The non-transitory computer-readable of claim 8 , where the one or more instructions, that cause the one or more processors to apply the cross derivative filter to the image, further cause the one or more processors to:
determine an orientation of the calibration pattern; and
determine the first coordinate plane based on the orientation of the calibration pattern.

12. The non-transitory computer-readable medium of claim 8 , where the one or more instructions that, when executed by the one or more processors, cause the one or more processors to apply the first oriented filter, further cause the one or more processors to:
determine a first derivative of the Gaussian function with respect to an x-axis,
the x-axis being associated with the first coordinate plane;

determine a second derivative of the Gaussian function with respect to a y-axis,
the y-axis being associated with the first coordinate plane, and
the y-axis being perpendicular to the x-axis;

determine a linear combination of the first derivative and the second derivative based on the second coordinate plane and the third coordinate plane; and
determine the second plurality of response peaks based on the linear combinat

Assignees

• Mathworks Inc

Inventors

• Lisin Dimitri

Classifications

• H04N23/80

  Camera processing pipelines; Components thereof · CPC title

• H04N17/00

  Diagnosis, testing or measuring for television systems or their details · CPC title

• H04N17/002 Primary

  for television cameras · CPC title

• G06T7/80

  Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration · CPC title