Choice of reference markings for enabling fast estimating of the position of an imaging device
First Claim
1. A method of estimating the position of the field of view of an imaging device relative to a board having markings visible thereon, the method comprising the step of:
- estimating the position of the field of view of the imaging device based on changes in position of a selected set of reference groups of markings, wherein for each selected reference group of markings, the change in position is determined by acquisition and analysis of image data of a corresponding;
selecting group(s) of one or more markings on the board to serve as respective reference group, the field of view of the image device being at a first position relative to the board when the selected reference group(s) are at a nominal position in the field of view;
using the image device to generate an image of a subset of the board corresponding to the nominal position of each respective reference group, at least one dimension of the subset image being substantially equal to or greater than the maximal positioning error of the image device in each respective subset image, detecting the image of the corresponding reference group, and determining the offset between the nominal position of the reference group in the field of view of the image device and the detected position thereof; and
determining the position of the field of view of the image device based on the determined offsets and based on the known relationship between the first position of the image device and the nominal position of the reference group(s).
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Accused Products
Abstract
A method of estimating the position of the field of view of an imaging device, such as a camera, relative to a board involves designating markings on the board as references and detecting the shift in these reference markings within the field of view of the camera compared to a known position therein. The reference markings are selected such that detection thereof involves analysis of only a subset of the image produced by the imaging device. The selection of a group of one or more markings to serve as a reference involves determination of the image region (error window) in which the reference marking(s) may appear, given the maximal positional error of the imaging device. It is also checked (step T4) that the entire error window will be within the useable field of view of the imaging device and that, within the error window, no other group of markings will appear that could be confused with the selected group of markings (step T5). Detection of the reference group of markings involves generation of an image profile along a line crossing the center of the error window and finding the best match between the markings along this profile and the markings in the reference group.
11 Citations
15 Claims
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1. A method of estimating the position of the field of view of an imaging device relative to a board having markings visible thereon, the method comprising the step of:
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estimating the position of the field of view of the imaging device based on changes in position of a selected set of reference groups of markings, wherein for each selected reference group of markings, the change in position is determined by acquisition and analysis of image data of a corresponding; selecting group(s) of one or more markings on the board to serve as respective reference group, the field of view of the image device being at a first position relative to the board when the selected reference group(s) are at a nominal position in the field of view; using the image device to generate an image of a subset of the board corresponding to the nominal position of each respective reference group, at least one dimension of the subset image being substantially equal to or greater than the maximal positioning error of the image device in each respective subset image, detecting the image of the corresponding reference group, and determining the offset between the nominal position of the reference group in the field of view of the image device and the detected position thereof; and determining the position of the field of view of the image device based on the determined offsets and based on the known relationship between the first position of the image device and the nominal position of the reference group(s). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 12)
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11. A method for estimating a position of a view of an imaging device relative to a board having markings thereon based on changes in position of a selected set of reference groups of the markings, comprising the steps of:
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selecting for consideration as candidate groups of markings only straight-line segments on the board; rejecting segments that are shorter than twice the maximal positioning error of the imaging device in the direction along which the respective segment extends; and acquiring and analyzing image data of a corresponding subset of the board to determine the changes in position of the selected set of reference groups of the markings; wherein the step of generating an image of a subset of the board comprises acquiring a profile along a line crossing the center of the error window, said line being oriented substantially perpendicular to the normal orientation of the segments in the respective reference group and having a length at least twice the maximal positioning error of the imaging device in the direction along which the profile is taken.
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13. An apparatus comprising:
- a processor adapted to acquire image data of a subset of a board corresponding to a selected reference group of markings, determine the change in position of the selected reference group of markings by analyzing the image data, and estimate the position of the field of view of an imaging device producing the image data relative to the board based on said changes in position of the selected reference group of markings;
select groups of one or more markings on the board to serve as respective reference groups, the field of view of the imaging device being at a first position relative to the board when the selected reference groups are at a nominal position in the field of view;
in each respective subset image, detect the image of the corresponding reference group, and determine the offset between the nominal position of the reference group in the field of view of the imaging device and the detected position thereof; and
determine the position of the field of view of the imaging device based on the determined offsets and based on the known relationship between the first position of the imaging device and the nominal position of the reference group(s); and
an imaging device adapted to generate an image of a subset of the board corresponding to the nominal position of each respective reference group, at least one dimension of the subset image being substantially equal to or greater than the maximum positioning error of the image device. - View Dependent Claims (15)
- a processor adapted to acquire image data of a subset of a board corresponding to a selected reference group of markings, determine the change in position of the selected reference group of markings by analyzing the image data, and estimate the position of the field of view of an imaging device producing the image data relative to the board based on said changes in position of the selected reference group of markings;
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14. A computer program product for estimating the position of the field of view of an imaging device relative to a board having markings visible thereon comprising computer readable media having encoded thereon:
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computer readable program code for selecting groups of one or more markings on the board to serve as respective reference groups, the field of view of the imaging device being at a first position relative to the board when the selected reference groups are at a nominal position in the field of view; computer readable program code for selecting groups of one or more markings on the board to serve as respective reference groups, the field of view of the imaging device being at a first position relative to the board when the selected reference groups are at a nominal position in the field of view; computer readable program code for acquiring image data of a subset of a board corresponding to the nominal position of each respective reference group, at least one dimension of the subset image being substantially equal to or greater than the maximum positioning error of the image device; computer readable program code for detecting the image of the corresponding reference group in each respective subset image, and determining the offset between the nominal position of the reference group in the field of view of the imaging device and the detected position thereof; computer readable program code for determining offsets and based on the known relationship between the first position of the imaging device and the nominal position of the reference group(s).
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Specification