Patent ID: 6280960
Filing Date: 2001-08-28
Classification: G01N,Y10S

Abstract:
A method for the optical detection and analysis of sub-micron particulates comprising the steps of:I. illuminating with radiation from a suitable optical source, an optically transparent substrate coated on one side with a thin layer of an optically opaque metal such that the optical beam is caused to be incident on the substrate-metal interface at or close to grazing incidence such that a portion of the incident optical beam propagates along the surface of the metal film or at an angle close to the plane of the metal film or at an angle at which surface plasmons are caused to be excited in the metal film such that a portion of the electromagnetic field associated with said beam propagates at least in part in the medium above the metal film to form a measurement zone;II. placing onto the surface of the metal film not in contact with the optical substrate a sample containing a population of particles of sub-micron dimensions such that particles enter the measurement zone;III. detecting, by a suitable lens and detector arrangement situated in a far field at normal or high angle to the plane of the metal film, the electromagnetic radiation individually scattered by or otherwise caused to emanate from the particle through its interaction with the electromagnetic field within the measurement zone for the purposes of analysis of particles in said sample.