Method of calibrating a direction of a pan, tilt, zoom, camera with respect to a fixed camera, and a system in which such a calibration is carried out
First Claim
1. A method of calibrating a direction of a pan, tilt, zoom, PTZ, camera with respect to a first, fixed, camera, comprising:
- receiving an overview image of a scene captured by a first, fixed, camera,directing a PTZ camera in a first direction,when the PTZ camera is in the first direction, performing the steps of;
a) receiving an image of the scene captured by the PTZ camera, wherein a field of view of the image captured by the PTZ camera partly overlaps a field of view the overview image,b) identifying a first set of features in the image of the scene captured by the PTZ camera,c) localizing at least a portion of the first set of features in the overview image so as to associate the at least a portion of first set of features in the image captured by the PTZ camera with a second set of features in the overview image,d) logging positional data of the second set of features in the overview image,e) defining a mapping between the image captured by the PTZ camera and the overview image based on the at least a portion of first set of features and the second set of features, and calculating a quality of the mapping,performing a first calibration of the PTZ camera by correlating the first direction of the PTZ camera with the positional data of the second set of features being logged when the PTZ camera is directed in the first direction,in case the quality of the mapping is below a first threshold;
redirecting the PTZ camera to a second direction,performing steps a)-d) when the PTZ camera is in the second direction, andperforming a second calibration of the PTZ camera by correlating the second direction of the PTZ camera with positional data of the second set of features being logged when the PTZ camera is directed in the second direction,wherein step e) further comprises mapping an object in the image captured by the PTZ camera to the overview image by using the defined mapping, wherein calculating the quality of the mapping includes calculating a similarity between an appearance of the object in the image captured by the PTZ camera and an appearance of the object after mapping to the overview image.
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Abstract
A method of calibrating a pan, tilt, zoom (PTZ) camera with a fixed camera utilizing an overview image of a scene captured by the fixed camera, and an image of the scene captured by the PTZ camera when directed in a first direction. By matching features in the overview image and the PTZ camera image, a first calibration is carried out by correlating the first direction to matching features in the overview image. A mapping between the PTZ camera image and the overview image is defined based on the matching features. The mapping is used to map an object from the PTZ camera image to the overview image. Based on an appearance of the mapped object, a quality of the mapping is calculated. If the quality is not good enough, the PTZ camera is redirected to a second direction, and a further calibration is carried out by again.
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Citations
14 Claims
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1. A method of calibrating a direction of a pan, tilt, zoom, PTZ, camera with respect to a first, fixed, camera, comprising:
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receiving an overview image of a scene captured by a first, fixed, camera, directing a PTZ camera in a first direction, when the PTZ camera is in the first direction, performing the steps of; a) receiving an image of the scene captured by the PTZ camera, wherein a field of view of the image captured by the PTZ camera partly overlaps a field of view the overview image, b) identifying a first set of features in the image of the scene captured by the PTZ camera, c) localizing at least a portion of the first set of features in the overview image so as to associate the at least a portion of first set of features in the image captured by the PTZ camera with a second set of features in the overview image, d) logging positional data of the second set of features in the overview image, e) defining a mapping between the image captured by the PTZ camera and the overview image based on the at least a portion of first set of features and the second set of features, and calculating a quality of the mapping, performing a first calibration of the PTZ camera by correlating the first direction of the PTZ camera with the positional data of the second set of features being logged when the PTZ camera is directed in the first direction, in case the quality of the mapping is below a first threshold; redirecting the PTZ camera to a second direction, performing steps a)-d) when the PTZ camera is in the second direction, and performing a second calibration of the PTZ camera by correlating the second direction of the PTZ camera with positional data of the second set of features being logged when the PTZ camera is directed in the second direction, wherein step e) further comprises mapping an object in the image captured by the PTZ camera to the overview image by using the defined mapping, wherein calculating the quality of the mapping includes calculating a similarity between an appearance of the object in the image captured by the PTZ camera and an appearance of the object after mapping to the overview image. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 14)
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12. A system, comprising:
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a first, fixed, camera arranged to capture an overview image of a scene, a pan, tilt, zoom, PTZ, camera which is separate from the first, fixed camera, and a controller operatively connected to the first camera and the PTZ camera, the controller being configured to direct PTZ camera in a first direction, and, when the PTZ camera is in the first direction, to perform the steps of; a) controlling the PTZ camera to capture an image of the scene, wherein a field of view of the image captured by the PTZ camera partly overlaps a field of view the overview image, b) identifying a first set of features in the image of the scene captured by the PTZ camera, c) localizing at least a subset of the first set of features in the overview image of the scene so as to associate the at least a subset of the first set of features in the image captured by the PTZ camera with a second set of features in the overview image, d) logging positional data of the second set of features in the overview image, e) defining a mapping between the image captured by the PTZ camera and the overview image based on the at least a subset of the first set of features and the second set of features, and calculating a quality of the mapping, the controller further being configured to; perform a first calibration of the PTZ camera by correlating the first direction of the PTZ camera with the positional data of the second set of features being logged when the PTZ camera is directed in the first direction, in case the quality of the mapping is below a first threshold; redirect the PTZ camera to a second direction, perform steps a)-d) when the PTZ camera is in the second direction, and perform a second calibration of the PTZ camera by correlating the second direction of the PTZ camera with positional data of the second set of features being logged when the PTZ camera is directed in the second direction, wherein step e) further comprises mapping an object in the image captured by the PTZ camera to the overview image by using the defined mapping, wherein calculating the quality of the mapping includes calculating a similarity between an appearance of the object in the image captured by the PTZ camera and an appearance of the object after mapping to the overview image. - View Dependent Claims (13)
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Specification