Patent ID: 7375808
Filing Date: 2008-05-20
Classification: G01J,G01N

Abstract:
1. An optical system for use in sensing and identifying a foreign particle in a gaseous environment, comprising: a light source for generating light having a known wavelength; an electrically-conductive opaque sheet having first and second faces opposing one another with an array of holes formed through said sheet and extending between said first and second faces, each of said holes having a diameter that is less than one quarter of said known wavelength, said sheet positioned relative to said light source such that said light is incident on said first face; and optical detection means positioned adjacent said second face and spaced apart therefrom such that a gaseous environment is adapted to be disposed therebetween, said optical detection means detecting a light pattern at said second face when said light is incident on said first face, wherein alterations in said light pattern are indicative of the presence of a foreign particle between said first face and said optical detection means.