Method and apparatus for rapid particle identification utilizing scattered light histograms

Abstract

Unique methods and apparatus are provided for rapidly identifying microscopic particles, such as protozoa and other microbes suspended in a fluid or gas. In one embodied form, the apparatus comprises: a polarized laser that produces a beam waist; an optical chassis including multiple light detectors, each light detector positioned around and oriented to view, without obscuration, a common region of regard of the laser beam waist; a sample chamber for containing a fluid sample to be analyzed; means for holding the sample chamber in a prescribed orientation with respect to the laser beam waist and in the common region of regard of the light detectors; means for causing the particles in the sample to circulate through the laser beam waist; means for covering the light source and optical chassis to create a dark enclosure; means for converting the light intensity values measured by the detectors into digital values; means for continuously entering the digital values into a computer; means for determining when a particle has entered the light beam at the common region of regard based on the digitized measurements; means for converting the digitized values to calibrated values; means for extracting Event Descriptors from the digitized and calibrated event data; means for calculating Discriminant Function values from the Event Descriptors; and means for defining probability histograms that enable the calculation of the probability that a Discriminant Function value calculated from measured values was caused by a specific particle species