Machine vision methods using feedback to determine an orientation, pixel width and pixel height of a field of view
First Claim
1. A machine vision method of determining a calibration relationship between a motion reference frame of a moveable object and an imaging reference frame of an imaging device that acquires an image of the object, the method comprising the steps of:
 A. positioning the object so that a fiducial thereon is at a first specified position with respect to the imaging reference frame and recording a position of the object with respect to the motion reference frame, that recorded position being referred to as a first object position;
B. positioning the object so that a fiducial thereon is at a second specified position with respect to the imaging reference frame and recording a position of the object with respect to the motion reference frame, that recorded position being referred to as a second object position;
C. positioning the object so that a fiducial thereon is at a third specified position with respect to the imaging reference frame and recording a position of the object with respect to the motion reference frame, that recorded position being referred to as a third object position; and
D. determining a calibration relationship between the reference frame of motion of the object and the reference frame of the camera as a function of respective motion reference frame coordinates of the first, second, and third object positions.
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Accused Products
Abstract
The invention provides machine vision methods and apparatus for determining a calibration relationship between the imaging reference frame of an image acquisition device (e.g., a camera) and the motion reference frame of a moveable object (e.g., a motion stage) by positioning the object so that a fiducial thereon (e.g., a calibration mark) lies at a first fiducial position in the field of view and recording the corresponding position of the object in the motion reference frame. The object is then repositioned so that the fiducial moves to a second fiducial position in the field of view. Again, the corresponding position of the object in the motion reference frame is recorded. Likewise, the object is moved to a third fiducial position in the field of view, and its corresponding position in the motion reference frame is recorded. A calibration relationship between the motion reference frame of the object and the imaging reference frame of the camera as a function of the first, second and third fiducial positions and as a function of the first, second and third object positions.
169 Citations
27 Claims

1. A machine vision method of determining a calibration relationship between a motion reference frame of a moveable object and an imaging reference frame of an imaging device that acquires an image of the object, the method comprising the steps of:

A. positioning the object so that a fiducial thereon is at a first specified position with respect to the imaging reference frame and recording a position of the object with respect to the motion reference frame, that recorded position being referred to as a first object position; B. positioning the object so that a fiducial thereon is at a second specified position with respect to the imaging reference frame and recording a position of the object with respect to the motion reference frame, that recorded position being referred to as a second object position; C. positioning the object so that a fiducial thereon is at a third specified position with respect to the imaging reference frame and recording a position of the object with respect to the motion reference frame, that recorded position being referred to as a third object position; and D. determining a calibration relationship between the reference frame of motion of the object and the reference frame of the camera as a function of respective motion reference frame coordinates of the first, second, and third object positions.  View Dependent Claims (2, 3, 4, 5, 6, 7, 8)


9. A machine vision method of determining a calibration relationship between a motion reference frame of a moveable object and an imaging reference frame of an imaging device that acquires an image of the object, the method comprising the steps of:

A. positioning the object so that a fiducial thereon moves to each of three specified positions with respect to the imaging reference frame and recording, for each of those specified positions, a corresponding position of the object with respect to the motion reference frame;
wherein the specified positions lie substantially on axes of the imaging reference frame; and
wherein a first specified position substantially lies on a center of the imaging reference frame; and
wherein second and third specified positions substantially lie on respective axes of the imaging reference frame;B. determining a calibration relationship between the reference frame of motion of the object and the reference frame of the camera in accord with any of the following mathematical relations;
space="preserve" listingtype="equation">τ
=atan2 (m.sub.y1 m.sub.y0,m.sub.x1 m.sub.x0)
space="preserve" listingtype="equation">w=sqrt ((m.sub.y1 m.sub.y0).sup.2 +(m.sub.x1 m.sub.x0).sup.2)/abs (i.sub.x1 i.sub.x0)
space="preserve" listingtype="equation">h=sqrt ((m.sub.y2 m.sub.y0).sup.2 +(m.sub.x2 m.sub.x0).sup.2)/abs (i.sub.y2 i.sub.y0)where τ
is an angular orientation of the imaging reference frame with respect to the motion reference frame;h is a pixel height in the imaging reference frame with respect to the motion reference frame; w is a pixel width in the imaging reference frame with respect to the motion reference frame; (m_{x0},m_{y0}) are the motion reference frame coordinates of the first object position; (m_{x1},m_{y1}) are the motion reference frame coordinates of the second object position; (m_{x2},m_{y2}) are the motion reference frame coordinates of the third object position; atan2 ( ) is an arctangent function; (i_{x0}, i_{y0}) are the image coordinates of the first object position; (i_{x1}, i_{y1}) are the image coordinates of the second object position; (i_{x2}, i_{y2}) are the image coordinates of the second object position; sqrt ( ) is a square root function; and abs ( ) is an absolute value function.


10. A machine vision apparatus for determining a calibration relationship between a motion reference frame of moveable object and an imaging reference frame of an imaging device that acquires an image of the object, the apparatus comprising:

A. first positioning means, coupled to the object and to the imaging device, for positioning the object so that a fiducial thereon is at a first specified position with respect to the imaging reference frame and recording a position of the object with respect to the motion reference frame, that recorded position being referred to as a first object position; B. second positioning means, coupled to the object and to the imaging device, for positioning the object so that a fiducial thereon is at a second specified position with respect to the imaging reference frame and recording a position of the object with respect to the motion reference frame, that recorded position being referred to as a second object position; C. third positioning means, coupled to the object and to the imaging device, positioning the object so that a fiducial thereon is at a third specified position with respect to the imaging reference frame and recording a position of the object with respect to the motion reference frame, that recorded position being referred to as a third object position; and D. analysis means, coupled to the first, second and third positioning means, for determining a calibration relationship between the reference frame of motion of the object and the reference frame of the camera as a function of respective motion reference frame coordinates of the first, second, and third object positions.  View Dependent Claims (11, 12, 13, 14, 15, 16, 17)


18. A machine vision apparatus for determining a calibration relationship between a motion reference frame of a moveable object and an imaging reference frame of an image acquisition device that acquires an image of the object, the apparatus comprising:

A. positioning means, coupled to the object and to the image acquisition device, for positioning the object so that a fiducial thereon moves to each of three specified positions with respect to the imaging reference frame and recording, for each of those specified positions, a corresponding position of the object with respect to the motion reference frame;
wherein the specified positions lie substantially on axes of the imaging reference frame; and
wherein a first specified position substantially lies on a center of the imaging reference frame; and
wherein second and third specified positions substantially lie on respective axes of the imaging reference frame;B. analysis means for determining a calibration relationship between the reference frame of motion of the object and the reference frame of the camera in accord with any of the following mathematical relations;
space="preserve" listingtype="equation">τ
=atan2 (m.sub.y1 m.sub.y0,m.sub.x1 m.sub.x0)
space="preserve" listingtype="equation">w=sqrt ((m.sub.y1 m.sub.y0).sup.2 +(m.sub.x1 m.sub.x0).sup.2)/abs (i.sub.x1 i.sub.x0)
space="preserve" listingtype="equation">h=sqrt ((m.sub.y2 m.sub.y0).sup.2 +(m.sub.x2 m.sub.x0).sup.2)/abs (i.sub.y2 i.sub.y0)where τ
is an angular orientation of the imaging reference frame with respect to the motion reference frame;h is a pixel height in the imaging reference frame with respect to the motion reference frame; w is a pixel width in the imaging reference frame with respect to the motion reference frame; (m_{x0},m_{y0}) are the motion reference frame coordinates of the first object position; (m_{x1},m_{y1}) are the motion reference frame coordinates of the second object position; (m_{x2},m_{y2}) are the motion reference frame coordinates of the third object position; atan2 ( ) is an arctangent function; (i_{x0}, i_{y0}) are the image coordinates of the first object position; (i_{x1}, i_{y1}) are the image coordinates of the second object position; (i_{x2}, i_{y2}) are the image coordinates of the second object position; sqrt ( ) is a square root function; and abs ( ) is an absolute value function.


19. An article of manufacture comprising a computer usable medium embodying program code for causing a digital data processor to carry out a method of determining a calibration relationship between a motion reference frame of a moveable object and an imaging reference frame of an imaging device that acquires an image of the object, the method comprising the steps of:

A. positioning the object so that a fiducial thereon is at a first specified position with respect to the imaging reference frame and recording a position of the object with respect to the motion reference frame, that recorded position being referred to as a first object position; B. positioning the object so that a fiducial thereon is at a second specified position with respect to the imaging reference frame and recording a position of the object with respect to the motion reference frame, that recorded position being referred to as a second object position; C. positioning the object so that a fiducial thereon is at a third specified position with respect to the imaging reference frame and recording a position of the object with respect to the motion reference frame, that recorded position being referred to as a third object position; and D. determining a calibration relationship between the reference frame of motion of the object and the reference frame of the camera as a function of respective motion reference frame coordinates of the first, second, and third object positions.  View Dependent Claims (20, 21, 22, 23, 24, 25, 26)


27. An article of manufacture of determining a calibration relationship between a motion reference frame of a moveable object and an imaging reference frame of an imaging device that acquires an image of the object, the method comprising the steps of:

A. positioning the object so that a fiducial thereon moves to each of three specified positions with respect to the imaging reference frame and recording, for each of those specified positions, a corresponding position of the object with respect to the motion reference frame;
wherein the specified positions lie substantially on axes of the imaging reference frame; and
wherein a first specified position substantially lies on a center of the imaging reference frame; and
wherein second and third specified positions substantially lie on respective axes of the imaging reference frame;B. determining a calibration relationship between the reference frame of motion of the object and the reference frame of the camera in accord with any of the following mathematical relations;
space="preserve" listingtype="equation">τ
=atan2 (m.sub.y1 m.sub.y0,m.sub.x1 m.sub.x0)
space="preserve" listingtype="equation">w=sqrt ((m.sub.y1 m.sub.y0).sup.2 +(m.sub.x1 m.sub.x0).sup.2)/abs (i.sub.x1 i.sub.x0)
space="preserve" listingtype="equation">h=sqrt ((m.sub.y2 m.sub.y0).sup.2 +(m.sub.x2 m.sub.x0).sup.2)/abs (i.sub.y2 i.sub.y0)where τ
is an angular orientation of the imaging reference frame with respect to the motion reference frame;h is a pixel height in the imaging reference frame with respect to the motion reference frame; w is a pixel width in the imaging reference frame with respect to the motion reference frame; (m_{x0},m_{y0}) are the motion reference frame coordinates of the first object position; (m_{x1},m_{y1}) are the motion reference frame coordinates of the second object position; (m_{x2},m_{y2}) are the motion reference frame coordinates of the third object position; atan2 ( ) is an arctangent function; (i_{x0}, i_{y0}) are the image coordinates of the first object position; (i_{x1}, i_{y1}) are the image coordinates of the second object position; (i_{x2}, i_{y2}) are the image coordinates of the second object position; sqrt ( ) is a square root function; and abs ( ) is an absolute value function.

1 Specification