Eliminating routine alignment calibrations in perspective dimensional measurements
First Claim
1. An apparatus for determining the locations of points on an object in three dimensions, said apparatus including a camera having an optical axis, and a support means, said support means providing a substantially straight axis of translation whereby said camera can be moved from a first viewing position to a second viewing position, said camera forming images of said points in an image plane, said optical axis being so arranged with respect to said axis of translation that there are created substantial shifts of said images in said image plane when said camera is moved between said first and second viewing positions, said apparatus also including image measurement means for measuring said shifts of said images and computing means which is adapted to compute said locations of said points using said shifts said images, wherein said support means also provides an axis of rotation, whereby said camera can also be rotated about said axis of rotation for alignment with objects of interest, said axis of rotation having an orientation with respect to said axis of translation, wherein the improvement comprises:
- (a) means for measurement of an angle of rotation of said camera about said axis of rotation; and
(b) means for incorporating said measurement of said angle of rotation into said determination of said locations of said points.
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Abstract
An improved system of perspective dimensional measurement uses complementary reference surfaces on a camera and on a camera translating unit to provide a repeatable relative orientation between the perspective displacement and the camera'"'"'s measurement coordinate system while still allowing a rotational and an optional translational degree of freedom for alignment of the camera with an object of interest. In one set of embodiments the rotational axis is accurately aligned with the translation axis. In a second set of embodiments, the geometry of the system is determined in an expanded alignment calibration procedure, the rotation of the camera about the rotational axis is measured, and these additional data are incorporated into the perspective measurement procedure.
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Citations
15 Claims
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1. An apparatus for determining the locations of points on an object in three dimensions, said apparatus including a camera having an optical axis, and a support means, said support means providing a substantially straight axis of translation whereby said camera can be moved from a first viewing position to a second viewing position, said camera forming images of said points in an image plane, said optical axis being so arranged with respect to said axis of translation that there are created substantial shifts of said images in said image plane when said camera is moved between said first and second viewing positions, said apparatus also including image measurement means for measuring said shifts of said images and computing means which is adapted to compute said locations of said points using said shifts said images, wherein said support means also provides an axis of rotation, whereby said camera can also be rotated about said axis of rotation for alignment with objects of interest, said axis of rotation having an orientation with respect to said axis of translation, wherein the improvement comprises:
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(a) means for measurement of an angle of rotation of said camera about said axis of rotation; and (b) means for incorporating said measurement of said angle of rotation into said determination of said locations of said points. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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- 9. An apparatus for determining three-dimensional distances between points on an object, the determination of said distances having a maximum allowable error, said apparatus including a substantially side-looking rigid borescope, said borescope having an optical system containing a nodal point, said nodal point being located at a range from said object, wherein said borescope can be moved along a substantially straight translational axis from a first viewing position to a second viewing position, and wherein said borescope can also be rotated about a rotational axis for alignment with objects of interest, wherein the improvement comprises the arrangement of said rotational axis to be aligned parallel to said translational axis, the alignment having an allowable error, as expressed in radians, smaller than said allowable error in said determination of said three-dimensional distances, as expressed as a fraction of the range between said object and said nodal point.
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14. A method of calibrating a perspective measurement system, wherein said system includes a camera which can be translated along a translational axis between a first viewing position and a second viewing position, thereby creating a perspective displacement, and wherein said camera can also be rotated about a rotational axis, and wherein an angle of rotation about said rotational axis is measured, and wherein said camera also includes a visual coordinate system, comprising the steps of:
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(a) performing a first alignment calibration procedure with said camera rotated to a first angle of rotation, thereby determining the orientation of said perspective displacement in a first temporary visual coordinate system; (b) performing a second alignment calibration procedure with said camera rotated to a second angle of rotation, thereby determining the orientation of said perspective displacement in a second temporary visual coordinate system; and (c) using said orientations of said perspective displacement in said first and second temporary visual coordinate systems, together with said first and second angles of rotation, to determine two angles of alignment of said rotational axis with respect to said translational axis and two angles of alignment of said visual coordinate system with respect to said rotational axis. - View Dependent Claims (15)
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Specification