Patent ID: 7751053

Claim:
Apparatus for the optical detection and/or analysis of individual sub-micron particles, the apparatus comprising: a substrate, part of one surface of which is coated with a film comprising an optically opaque metal, and part of which surface is left uncoated, such that the surface has a coated portion and an uncoated portion; means for illuminating said substrate with a focussed beam of radiation from a source, such that a focussed optical beam is caused to be incident on the substrate at a point on the uncoated portion of the surface adjacent to, but not coincident with, the metal film coated portion of the surface, such that the optical beam is caused to propagate above but substantially parallel or at an angle of less than 5° and close to the surface of the metal film; and means for individually detecting, by a lens and detector arrangement situated in the far field at the normal or high angle to the plane of the metal film, the optical radiation individually scattered by, or otherwise caused to emanate from, individual particles in a sample placed on the coated portion of the substrate surface through their interaction with the optical beam.