Patent ID: 6522405
Filing Date: 2003-02-18
Classification: G01N,Y10S

Abstract:
A method for detecting particles comprising converging a light beam from a coherent light source so that the resulting focused light passes through a stream of fluid containing particles therein in such a manner that a focus of the focused light is located in the stream of fluid, receiving a light passed through the stream of fluid and diffracted by the particles by a photo-detector which is positioned at an opposite side of the coherent light source with respect to the stream and on an optical axis of the light beam to produce electrical signals, and counting numbers of particles in the stream by treating the electrical signal;wherein the electrical signals have frequencies dependent on a size of each particle and a distance of each particle from the focus and in that the electrical signals are distinguished into plural ranges according to the frequency of each of the signals and counting each number of the particles contained the ranges by treating the electrical signals.