Image processing system for estimating camera parameters

An image processor that receives a video signal from a camera representative of a scene as viewed by the camera, the scene including a calibration surface including thereon a calibration pattern, the calibration pattern including a plurality of alternately colored elements which provide a corresponding plurality of corners at locations on the calibration pattern at which more than two of the colored elements adjoin, the corner locations defining a first group of lines and a second group of lines, the lines in each of the group of lines being parallel with respect to each other and on the calibration surface, the first group of lines being orthogonal to the second group of lines, the image processor comprising:

• a detection unit configured to detect from the video signal at least some of the corner locations to identify the first and second group of lines of the calibration pattern;
• an extrapolation unit configured to extrapolate the lines from each group of lines to determine a presence and a location of a first intersection point on a plane of the scene as viewed by the camera at which the extrapolated lines from the first group intersect and a second intersection point on the plane of scene as viewed by the camera at which the extrapolated lines from the second group intersect;
• and
• an estimating unit configured to estimate from the presence and the location of the first and second intersection points one or more of an estimated roll angle value, an estimated pitch angle value and an estimated yaw angle value corresponding to a roll angle, pitch angle and yaw angle of the camera relative to the calibration surface, wherein
• the detection of the corner locations by the detection unit includes identifying from the video signal a plurality of potential corner locations, defining an area of the scene as viewed by the camera centered around each potential corner location, analyzing a color of points lying on a periphery of each area to estimate a likelihood that a corner is located at each potential corner location, and
• the analyzing of the color of the points lying on the periphery of the area includes dividing the periphery into a first part and a second part, and comparing a distribution of color of the points on the first part with a distribution of color of the points on the second part.

A method of estimating camera parameters from a captured image, the method comprising:

• generating a video signal representative of a scene as viewed by a camera, the scene including a calibration surface including thereon a calibration pattern, the calibration pattern including a plurality of alternately colored elements which provide a corresponding plurality of corners at locations on the calibration pattern at which more than two of the colored elements adjoin, the corner locations defining a first group of lines and a second group of lines, the lines in each of the group of lines being parallel with respect to each other and with respect to the calibration surface, the first group of lines being orthogonal to the second group of lines;
• detecting from the video signal at least some of the corner locations to identify the first and second group of lines of the calibration pattern;
• extrapolating the lines from each group of lines;
• determining from the extrapolated lines a presence and a location of a first intersection point on a plane of the scene as viewed by the camera at which the extrapolated lines from the first group intersect and a second intersection point on the plane of the scene as viewed by the camera at which the extrapolated lines from the second group intersect;
• and
• estimating from the presence and the location of the first and second intersection points one or more of an estimated roll angle value, an estimated pitch angle value and an estimated yaw angle value corresponding to a roll angle, pitch angle and yaw angle of the camera relative to the calibration surface, wherein
• the detecting of the corner locations, includes
• identifying from the video signal a plurality of potential corner locations,
• defining an area of the scene as viewed by the camera centered around each potential corner location, and
• analyzing a color of points lying on a periphery of each area to estimate a likelihood that a corner is located at each potential corner location, the analyzing of the color of the points lying on the periphery of the area including dividing the periphery into a first part and a second part, and comparing a distribution of color of the points on the first part with a distribution of color of the points on the second part.

A computer graphics generation system, comprising:

• a camera configured to generate video images of a scene captured by the camera, the scene including a calibration surface including thereon a calibration pattern, the calibration pattern including a plurality of alternately colored elements which provide a corresponding plurality of corners at locations on the calibration pattern at which more than two of the colored elements adjoin, the corner locations defining a first group of lines and a second group of lines, the lines in each of the group of lines being parallel with respect to each other and on the calibration surface, the first group of lines being orthogonal to the second group of lines;
• and
• an image processor configured to receive the video signal from the camera, and to combine the video images with rendered computer generated objects, the computer generated objects being rendered in accordance with a position and orientation of the camera determined by
• detecting from the video signal at least some of the corner locations to identify the first and second group of lines of the calibration pattern,
• extrapolating the lines from each group of lines to determine a presence and a location of a first intersection point on a plane of the scene as viewed by the camera at which the extrapolated lines from the first group intersect and a second intersection point on the plane of scene as viewed by the camera at which the extrapolated lines from the second group intersect, and
• estimating from the presence and the location of the first and second intersection points one or more of an estimated roll angle value, an estimated pitch angle value and an estimated yaw angle value corresponding to a roll angle, pitch angle and yaw angle of the camera relative to the calibration surface, wherein
• the detection of the corner locations by the image processor includes identifying from the video signal a plurality of potential corner locations, defining an area of the scene as viewed by the camera centered around each potential corner location, analyzing a color of points lying on a periphery of each area to estimate a likelihood that a corner is located at each potential corner location, and
• the analyzing of the color of the points lying on the periphery of the area includes dividing the periphery into a first part and a second part, and comparing a distribution of color of the points on the first part with a distribution of color of the points on the second part.

A non-transitory computer readable storage medium having computer executable instructions, which when loaded on to a computer cause the computer to perform a method of estimating camera parameters from a captured image, the method comprising:

• generating a video signal representative of a scene as viewed by a camera, the scene including a calibration surface including thereon a calibration pattern, the calibration pattern including a plurality of alternately colored elements which provide a corresponding plurality of corners at locations on the calibration pattern at which more than two of the colored elements adjoin, the corner locations defining a first group of lines and a second group of lines, the lines in each of the group of lines being parallel with respect to each other and with respect to the calibration surface, the first group of lines being orthogonal to the second group of lines;
• detecting from the video signal at least some of the corner locations to identify the first and second group of lines of the calibration pattern;
• extrapolating the lines from each group of lines;
• determining from the extrapolated lines a presence and a location of a first intersection point on a plane of the scene as viewed by the camera at which the extrapolated lines from the first group intersect and a second intersection point on the plane of the scene as viewed by the camera at which the extrapolated lines from the second group intersect;
• and
• estimating from the presence and the location of the first and second intersection points one or more of an estimated roll angle value, an estimated pitch angle value and an estimated yaw angle value corresponding to a roll angle, pitch angle and yaw angle of the camera relative to the calibration surface, wherein
• the detecting of the corner locations includes
• identifying from the video signal a plurality of potential corner locations,
• defining an area of the scene as viewed by the camera centered around each potential corner location, and
• analyzing a color of points lying on a periphery of each area to estimate a likelihood that a corner is located at each potential corner location, the analyzing of the color of the points lying on the periphery of the area including dividing the periphery into a first part and a second part, and comparing a distribution of color of the points on the first part with a distribution of color of the points on the second part.

An apparatus for estimating camera parameters from a captured image, the apparatus comprising:

• means for generating a video signal representative of a scene as viewed by a camera, the scene including a calibration surface including thereon a calibration pattern, the calibration pattern including a plurality of alternately colored elements which provide a corresponding plurality of corners at locations on the calibration pattern at which more than two of the colored elements adjoin, the corner locations defining a first group of lines and a second group of lines, the lines in each of the group of lines being parallel with respect to each other and with respect to the calibration surface, the first group of lines being orthogonal to the second group of lines;
• means for detecting from the video signal at least some of the corner locations to identify the first and second group of lines of the calibration pattern;
• means for extrapolating the lines from each group of lines;
• means for determining from the extrapolated lines a presence and a location of a first intersection point on a plane of the scene as viewed by the camera at which the extrapolated lines from the first group intersect and a second intersection point on the plane of the scene as viewed by the camera at which the extrapolated lines from the second group intersect;
• and
• means for estimating from the presence and the location of the first and second intersection points one or more of an estimated roll angle value, an estimated pitch angle value and an estimated yaw angle value corresponding to a roll angle, pitch angle and yaw angle of the camera relative to the calibration surface, wherein
• the means for detecting the corner locations includes
• means for identifying from the video signal a plurality of potential corner locations,
• means for defining an area of the scene as viewed by the camera centered around each potential corner location, and
• means for analyzing a color of points lying on a periphery of each area to estimate a likelihood that a corner is located at each potential corner location, the means for analyzing the color of the points lying on the periphery of the area including means for dividing the periphery into a first part and a second part, and means for comparing a distribution of color of the points on the first part with a distribution of color of the points on the second part.