Method and apparatus for calibrating cameras used in the alignment of motor vehicle wheels

A method of calibrating an opto-electronic alignment system including at least first and second spaced apart optical inspection devices and an associated data processor adapted to inspect and determine the position and orientation relative to said inspection devices of targets affixed to objects such as vehicle wheels to be aligned, and from such determination to infer the position and orientation of the objects to which the targets are affixed, comprising the steps of:

• providing first and second target means;
• providing a means for supporting said first and second target means in rigid disposition relative to each other and at a predetermined fixed distance from each other;
• disposing said supporting means relative to a work surface such that both said first and second target means lie within the field of view of said first inspection device;
• optically inspecting said first and second target means to obtain first optical information useful to determine the position and orientation of each said target means relative to said first inspection device;
• reorienting said supporting means such that said first target means lies within the field of view of said first inspection device and said second target means lies within the field of view of said second inspection device, and again optically inspecting said first and second target means to obtain second optical information useful to determine the present position and orientation of said first target means relative to said first inspection device and the present position and orientation of said second target means relative to said second inspection device;
• and
• using the first and second optical information to compute the precise position and orientation of said second inspection device relative to said first inspection means.

Apparatus for calibrating an opto-electronic alignment system including at least first and second spaced apart optical inspection devices and an associated data processor adapted to inspect and determine the position and orientation relative to said inspection devices of targets affixed to objects such as vehicle wheels to be aligned, and from such determination to infer the position and orientation of the objects to which the targets are affixed, comprising:

• first and second targets each having predetermined geometric attributes that can be optically detracted;
• a support for supporting said first and second targets in rigid disposition relative to each other and at a predetermined fixed distance from each other so that when said support is disposed relative to a work surface such that both said first and second targets lie within the field of view of said first inspection device, the targets can be optically inspected by the alignment system to obtain first optical information useful to determine the position and orientation of each said target relative to said first inspection device, and when said support is reoriented such that said first target lies within the field of view of said first inspection device and said second target lies within the field of view of said second inspection device, the targets can be optically inspected by the alignment system to obtain second optical information useful to determine the present position and orientation of said first target relative to said first inspection device and the present position and orientation of said second target relative to said second inspection device, and the first and second optical information can be used to compute the precise position and orientation of said second inspection device relative to said first inspection device.