Other

Public Health Laboratory Service Board

Robert J Carr

David J Clarke

Tony Atkinson

Anthony Atkinson

Sumaia Al-Shukri

Method and apparatus for the single particle detection of submicron structures such as biological molecules and viruses utilises and optically transparent substrate coated with a thin film of metal illuminated with an optical beam incident at or close to critical or SPR angle wherein part of the beam propagates along the metal surface defining a measurement zone from which submicron particles contained in a sample placed in contact with the metal film scatter light which can be detected in the far field by conventional photodetection systems. The apparatus can be configured in a flow cytometric of optical microscope configuration.

Optical detection and analysis of sub-micron particles

Examination of objects of macromolecular size

Particle velocity is determined optically through the use of crossed interference fringe patterns. The fringe patterns are produced by passing laser beams of distinct wavelength along a common optical fibre and through two crossed diffraction gratings which are bonded to the free end of the fibre. Each diffraction grating is constructed in the manner of an interference filter so as to produce interference fringes at one wavelength but to transmit the other wavelength substantially uniformly across the grating. Other interference elements can be used in place of diffraction gratings and the use of a single diffraction grating is envisaged in certain circumstances. An indication of the sense of particle movement can be achieved by creating a fringe pattern of steadily increasing fringe spacing.

Optical determination of velocity using crossed interference fringe

Optical analysis

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Wiltshire, United Kingdom

Robert J Carr