Method and system for calibrating a sensor
First Claim
1. A method of calibrating a field of view of a sensor within an observable area, comprising the steps of:
- defining a reference image of a first observable area having at least one distinctive feature, said reference image defined by a first sensor placed at a base location;
establishing a set of reference points relative to said first sensor that represent a location within said reference image of said at least one distinctive feature;
placing a second sensor in a second observable area that is similar to said first observable area, said second sensor being placed in a location that generally corresponds in position to said base location;
obtaining a test image of said second observable area, said test image obtained by said second sensor and depicting at least one distinctive feature present in said second observable area;
comparing said set of reference points to said at least one distinctive feature depicted in said test image in order to assess a relative accuracy in placement of said second sensor; and
transforming said test image into distance image by assigning a location value to every pixel making up said test image, said location value representing a distance between said pixel and said distinctive feature depicted in said test image that lies closest to said pixel;
mapping said set of reference points onto said distance image for at least one possible orientation of said second sensor, said at least one orientation residing in a defined region of space; and
calculating an average distance between said at least one distinctive feature depicted in said test image and said set of mapped reference points, said calculated average distance representing a relative level of accuracy between a presumed orientation of said second sensor and an actual orientation of said second sensor.
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Abstract
A new system and method for calibrating the field-of-view of a sensor that is part of a vehicle occupancy sensing system. Calibration is carried out by generating an image of the vehicle interior and then identifying within the image at least one distinctive feature of the vehicle interior. The location of the distinctive feature(s) identified in the image are then compared to a set of reference points for a plurality of different sensor positions. The presumed sensor position that corresponds to the set of reference points that most closely match the location of the identified distinctive feature(s) is then presumed to estimate the actual position of the sensor.
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Citations
27 Claims
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1. A method of calibrating a field of view of a sensor within an observable area, comprising the steps of:
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defining a reference image of a first observable area having at least one distinctive feature, said reference image defined by a first sensor placed at a base location;
establishing a set of reference points relative to said first sensor that represent a location within said reference image of said at least one distinctive feature;
placing a second sensor in a second observable area that is similar to said first observable area, said second sensor being placed in a location that generally corresponds in position to said base location;
obtaining a test image of said second observable area, said test image obtained by said second sensor and depicting at least one distinctive feature present in said second observable area;
comparing said set of reference points to said at least one distinctive feature depicted in said test image in order to assess a relative accuracy in placement of said second sensor; and
transforming said test image into distance image by assigning a location value to every pixel making up said test image, said location value representing a distance between said pixel and said distinctive feature depicted in said test image that lies closest to said pixel;
mapping said set of reference points onto said distance image for at least one possible orientation of said second sensor, said at least one orientation residing in a defined region of space; and
calculating an average distance between said at least one distinctive feature depicted in said test image and said set of mapped reference points, said calculated average distance representing a relative level of accuracy between a presumed orientation of said second sensor and an actual orientation of said second sensor. - View Dependent Claims (2, 3)
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4. A method of calibrating a field of view of a sensor within an observable area, comprising the steps of:
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obtaining a test image of the observable area, said test image comprising a plurality of pixels;
transforming said test image into a distance image by assigning a location value to each pixel within said test image, said location value representing a distance between said pixel and a distinctive feature that lies closest to said pixel;
mapping at least one set of reference points, representing an ideal location of said at least one distinctive feature, onto said distance image for at least one possible orientation of said sensor, said at least one orientation residing in a defined region of space;
calculating an average distance between said at least one distinctive feature in said distance image and said at least one set of mapped reference points, said calculated average distance representing a relative level of accuracy between said presumed orientation of said sensor and an actual orientation of said sensor. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12)
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13. A vehicle occupancy sensing (VOS) system, comprising:
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a digital sensor mounted within a vehicle in such a manner as to be able to generate an image of an interior of the vehicle;
a processor in communication with said sensor and capable of analyzing said image generated by said sensor in accordance with at least one heuristic; and
memory in communication with said processor and capable of storing data generated by said processor, wherein said at least one heuristic includes a calibration heuristic that instructs said sensor to generate an image of the vehicle interior and said processor to identify and isolate within said image at least one distinctive feature of the vehicle interior, whereupon said processor compares an image location of said at least one distinctive feature to at least one set of reference points for a plurality of different presumed sensor positions, said comparison yielding the closest set of reference points for said presumed sensor position that best estimates an actual position of said sensor. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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21. A method of calibrating a field of view of a sensor for a vehicle occupancy sensing system, comprising the steps of:
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generating a digital image of an interior of the vehicle;
identifying within said image at least one distinctive feature of the vehicle interior, said at least one distinctive feature appearing in the image as an edge existing between two regions of differing contrast;
comparing within said image a location of said at least one identified distinctive feature to at least one set of reference points, said at least one set of reference points adjusted for one particular position of the sensor and representing an ideal location of said at least one distinctive feature for said particular sensor position;
repeating said comparison step a plurality of times, each time adjusting said at least one set of reference points for a different particular position of the sensor; and
determining which particular position of the sensor yields at least one set of adjusted reference points that most closely match said location of said at least one identified distinctive feature, said determined particular position estimating an actual position of the sensor. - View Dependent Claims (22, 23, 24, 25, 26, 27)
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Specification