Alignment correction prio to image sampling in inspection systems

An apparatus to inspect a wafer defining at least one die thereon comprising:

• an x-y stage to transport said die;
• a scanner to obtain an electronic image equivalent of said at least one die as said x-y stage transports said die;
• a first comparator coupled to said scanner to determine the x and y offset between the electronic images of two die;
• an alignment computer to reposition said scanner to adjust the x and y positions of one electronic image of one die with respect to said electronic image of said other die;
• a second comparator coupled to said scanner to compare said electronic images of said first and second die following the operation of said alignment computer;
• and
• a defect detector coupled to said second comparator to identify defect differences between said electronic images compared by said second comparator.