Apparatus and method for determining vehicle wheel alignment measurements from three dimensional wheel positions and orientations

A method of calibrating wheel alignment apparatus having first and second fields of view, said method comprising the steps of:

• disposing a first optical target in the first field of view and disposing a second optical target in the second field of view, said first and second optical targets being fixed with respect to each other;
• obtaining a first image of the first optical target in the first field of view and obtaining a first image of the second optical target in the second field of view;
• changing the orientation of the first optical target in the first field of view to a new orientation and changing the orientation of the second optical target in the second field of view to a new orientation without changing the orientation of the first and second optical targets with respect to each other;
• obtaining a second image of the first optical target in the first field of view at the new orientation and obtaining a second image of the second optical target in the second field of view at the new orientation;
• and
• determining from said images the relative alignment of the first field of view relative to the second field of view.

A method for calibrating wheel alignment apparatus, said method comprising the steps of:

• providing a first video camera having a first field of view and a second video camera having a second field of view;
• providing a first fixture arranged so as to rigidly align said first field of view with said second field of view;
• providing a first and second calibration optical target such that said first and second calibration targets are rigidly joined together by a second fixture such that said first calibration optical target is at a first orientation in said first field of view while said second calibration optical target is at a first orientation in said second field of view;
• determining a first set of coordinates and orientation of said first calibration optical targets in a first three dimensional coordinate system from the image formed of said first calibration optical target by said first video camera;
• determining a first set of coordinates and orientation of said second calibration optical targets in a second three dimensional coordinate system from the image formed of said second calibration optical target by said second video camera;
• rotating said first and second calibration targets along with said second fixture about an axis through at least a partial revolution such that said first calibration optical target lies at a second orientation within said first field of view and such that said second calibration optical target lies at a second orientation within said second field of view;
• determining a second set of coordinates and orientation values of said first calibration optical targets in a first three dimensional coordinate system from the image formed of said first calibration optical target by said first video camera;
• determining a second set of coordinates and orientation values of said second calibration optical targets in a second three dimensional coordinate system from the image formed of said second calibration optical target by said second video camera;
• and
• determining, from said first and second sets of coordinates and orientations of said first calibration target and from said first and second sets of coordinates and orientations of said second calibration targets, the relative alignment of said first field of view relative to said second field of view.

A method for measuring the relative alignment of the runways of an automotive lift rack used for measuring the alignment of vehicle wheels, said method comprising the steps of:

• disposing at least first and second predetermined optical targets along a first runway of the automotive lift rack;
• disposing at least third and fourth predetermined optical targets along the a second runway of the automotive lift rack;
• obtaining images of said first, second, third and fourth optical targets;
• determining from the images of the first, second and third optical targets a plane which contains said first, second and third optical targets;
• determining from the image of the fourth optical target the distance between said fourth target and the plane defined by the other three targets, said distance being a measure of the relative alignment of the first and second runways.

A method for measuring the relative alignment of the runways of an automotive lift rack used for measuring the alignment of vehicle wheels, said method comprising the steps of:

• providing a first set of at least two optical targets of predetermined configuration and appearance mounted to one runway of a lift rack so as to represent the surface of said one runway on which the corresponding wheels of a vehicle rolls;
• providing a second set of at least two optical targets of predetermined configuration and appearance mounted to the other runway of a lift rack so as to represent the surface of said other runway on which the corresponding wheels of a vehicle rolls;
• providing a first video camera arranged so as to be able to view said first optical targets;
• providing a second video camera arranged so as to be able to view said second optical targets;
• providing a computer operatively connected to said first and said second camera, said computer being responsive to the viewed images of said first set of targets to determine the coordinates of said first set of targets in a three dimensional coordinate system, said computer also being responsive to the viewed images of said second set of targets to determine the coordinates of said second set of targets in said three dimensional coordinate system,
• determining a plane from two optical targets of said first set of optical targets and one optical target of said second set of optical targets;
• determining the distance between said plane and another optical target of said second set of optical targets;
• providing a display operatively connected to computer;
• and
• driving said display to show a visual indication of said distance.

A method of calibrating wheel alignment apparatus having first and second fields of view, said method comprising the steps of:

• disposing a first optical target in the first field of view and disposing a second optical target in the second field of view, said first and second optical targets being fixed with respect to each other;
• obtaining a first image of the first optical target in the first field of view and obtaining a first image of the second optical target in the second field of view;
• changing the location of the first optical target in the first field of view to a new location and changing the location of the second optical target in the second field of view to a new location without changing the locations of the first and second optical targets with respect to each other;
• obtaining a second image of the first optical target in the first field of view at the new location and obtaining a second image of the second optical target in the second field of view at the new location;
• and
• determining from said images the relative alignment of the first field of view relative to the second field of view.

A method of checking the calibration of wheel alignment apparatus having first and second fields of view, said method comprising the steps of:

• initially imaging a first optical target in the first field of view and imaging a second optical target in the second field of view, said first and second optical targets being fixed with respect to each other, and said imaging being made by at least one optical camera;
• determining an initial distance between said first and second optical targets from said images of said first and second optical targets;
• subsequently imaging the first and second optical targets and determining from their images a subsequent distance between said targets;
• comparing the initial distance with the subsequent distance to determine whether the focal length of said at least one optical camera has changed.