Method and apparatus for distinguishing regions where a material is present on a surface

摘要

A property of the surface such as height is sensed as a function of position on the surface. A statistical spread in the sensed property as a function of the position is computed. Regions where the material is present are distinguished from other regions on the basis of the spread, e.g. conductor tracks on a PCB assembly are distinguished from a PCB substrate by having lower spread.