Apparatus and method for storing interferometric images of scanned defects and for subsequent static analysis of such defects

Apparatus for determining characteristics of a test surface of a test specimen, wherein said apparatus comprises:

• an instrument having an objective section for viewing said test surface, a first optical path directing a first image of said test surface at said objective section to a first sensing means for sensing features of said first image along an image receptive line, said first sensing means operating first output means to provide a first signal responsive to variations in said image, and a second optical path directing a second image of said test surface in said objective section to a second sensing means for sensing features of said second image extending within an area;
• specimen drive means for driving said test specimen so that said test surface is moved past said objective section according to a preferred path of motion;
• defect detection means for detecting variations in said first signal as said test specimen is driven to produce a flowing image on said first sensing means;
• data storage means;
• location sensing means providing location data describing movement of said test surface past said objective section;
• first control means storing said location data within said data storage means in response to said defect detection means;
• and
• second control means operating said specimen drive means to move said test surface into locations corresponding to said location data stored within said data storage means, wherein said second control means moves said test surface successively between said locations, holding said test surface at said locations as a stationary image of said test surface is projected on said second sensing means.