Importance

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Abstract

The method and apparatus are utilized for quickly and accurately positioning a workpiece, which is situated on a movable platform and which has at least one indicia mark thereon having a different sensitivity to a sensing means than an adjacent contrast area, to a position where the indicia mark is in registry with a registration axis. The method includes the steps of: effecting a scan of the sensing means transverse to the registration axis in the area on the workpiece through which the registration axis extends with sensing means that are capable of generating electrical signals related to what is sensed; providing in the sensing means a sensor system which can function as one or two sensors, real or pseudo; processing the electrical signals generated by the sensing systems in a manner whereby some of the signals are treated as the scan data of a first sensor, real or pseudo, and the other of the signals are treated as the scan data of a second sensor, real or pseudo; setting the effective width of the sensor system at rest to be no greater than slightly greater than the width of the indicia mark; setting the amplitude of the scan which is effected transversely of the indicia mark when the indicia mark is close to the registration axis to be substantially equal to a real or pseudo single sensor width and about a center axis of the sensing means; and setting the center axis of the sensing means in registration with the registration axis.

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