Patent ID: 6097428
Filing Date: 2000-08-01
Classification: G01N,G06T

Abstract:
An apparatus for use in inspecting the surface of an object for contaminant particles, said apparatus comprising:(a). a light source for illuminating an area on the surface of the object,(b). a camera for detecting light scattered by any particles present on the surface at that area, the intensity of the scattered light being proportional to the size of the particles,(c). a lens for focusing said scattered light onto said camera, said camera detecting light scattered from the area on the surface of the object over a field of view, or window, which is defined by said camera, said lens and the relative distance therebetween, and(d). a computer coupled to said camera for storing, processing, identifying and/or analyzing the light detected by said camera, wherein said computer calculates a minimum light intensity threshold level for each window of the object defined by said apparatus based on light intensity characteristics of the particular window by which all scattered light which falls below the threshold level is filtered out from further storing, processing, identifying and/or analyzing by said computer, herein the value of the thesehold level for each window of the object defined by said apparatus is calculated using the equation:T.sub.W =.mu..sub.W +.eta..delta..sub.Wwhere T.sub.W represents the threshold value for the particular window, .mu..sub.W resents the mean light intensity for the particular window, .eta. is a floating point constant value and .delta..sub.W is the light intensity standard deviation for the pagicular window.