Method for imaging workpiece surfaces at high robot transfer speeds with reduction or prevention of motion-induced distortion

A method for obtaining an image of a workpiece in a processing system comprising at least one processing chamber and a robot for transporting a workpiece to said at least one processing chamber along a workpiece transit path, said method comprising:

• causing said robot to transport the workpiece along said workpiece transit path;
• capturing at a variable frame rate successive frames of an elongate stationary field of view transverse to a portion of said workpiece transit path lying within said field of view, said field of view having a length not less than a diameter of said workpiece and a width that is a fraction of said diameter, said successive frames corresponding to respective slices of a still image of said workpiece;
• illuminating at least a portion of said workpiece within said field of view;
• obtaining information defining movement of said robot, and, during said capturing, computing from said information a current velocity of said workpiece;
• adjusting said variable frame rate in accordance with a difference between said current velocity of said workpiece and a reference velocity or previous velocity;
• and
• providing a still image of said workpiece comprising said successive frames.