Patent ID: 7218386
Filing Date: 2007-05-15
Classification: G01N,G07D

Abstract:
1. A method of determining if a surface contains a specific OVM comprising the steps of: (1) illuminating the surface using light containing two substantially monochromatic components of wavelength λ (2) detecting the intensity of scattered light from the surface at two scattering angles Ø (3) computing the magnitude of the difference between the intensity values for λ (4) generating an output signal indicating the presence or absence of the specific OVM depending on the computed difference magnitude relative to a predetermined value, wherein the surface is illuminated separately first with monochromatic light of one wavelength and then with monochromatic light of the other wavelength, and wherein detection is performed by a single detector which is moved between two positions so as to receive light reflected/scattered from the surface first at one and then the other of the two angles Ø