Patent ID: 7217937

Claim:
A method for analyzing a liquid sample to differentiate and count particles of different species in an overall population, comprising the steps of: a) tagging particles in certain species with a fluorescent material; b) passing the liquid sample through a sample cell a portion at a time; c) illuminating the sample cell with a first optical source having a wavelength and intensity λ 1 , which causes tagged particles to emit fluorescent signals at a fluorescent wavelength λ 2 ; d) separating the light exiting the sample cell into the optical source wavelength λ 1 and the fluorescent wavelength λ 2 using a wavelength selective filter; e) forming a first image of the tagged particles in the sample cell with the light having the fluorescent wavelength λ 2 exiting the sample cell using a first magnification system on a first pixel array; f) forming a second image of each portion of the liquid sample in the sample cell with the light having the optical source wavelength λ 1 exiting the sample cell using a second magnification system on a second pixel array or with light periodically illuminating the sample cell from a second light source at the fluorescent wavelength λ 2 using the first magnification system on the first pixel array synchronized with the second light source; g) determining at least two morphological parameters of a particle in each image; and h) correlating the morphological parameters from the first image and the second image to differentiate and count the number of particles in each different species in the sample cell and in the overall population.