Patent US 4,254,433

The movement of an article such as a product carried by a conveyor is monitored by providing a patterned target, preferably striped with contrasting lines, to move with the object. A solid state line scan camera views the pattern of the target as it moves relative to the camera and the electronic output of the camera representing the light and dark areas of the target is analyzed by an electronic circuit to determined the movement of the target and therefore of the object being monitored. The resulting electronic signal representing the motion of the object is useful for coordinating the movement of a robot which is operating upon the object during its movement.