Method and apparatus for registration control during processing of a workpiece, particularly during producing images on substrates in preparing printed circuit boards

A method of processing a substrate comprising the following steps:

• (a) performing a first processing operation on the substrate;
• (b) mounting the substrate on a processing machine to perform a second processing operation thereon;
• (c) sensing the actual locations of preselected features on the substrate produced by said first processing operation;
• (d) and controlling said second processing operation in accordance with the sensed features;
• wherein said steps (c) and (d) are performed by:
• (i) determining, before step (b), the nominal locations of at least one reference feature on the substrate in terms of the coordinate of the substrate;
• (ii) after step (b), sensing, and measuring the location of, said reference feature in terms of the coordinates of said processing machine to perform the second operation on the substrate;
• (iii) determining at least one geometrical transformation needed to transform the substrate coordinates of the nominal location of said reference feature to the machine coordinates of the sensed location of said reference feature;
• and
• (iv) controlling said second processing operation in accordance with said at least one geometrical transformation.