Patent ID: 7088447

Claim:
A system for detecting individual particles suspended in a fluid, said system comprising: a housing having a sample chamber; a fluid inlet orifice directing a fluid flow into said sample chamber; a light source for producing and directing light into said sample chamber and through said fluid flow; a light detecting element producing an output signal characteristic of individual particles suspended in said fluid; an aperture assembly located to aperture said light, said aperture assembly having a portion in direct view of said light detecting element, said aperture assembly having an inside surface exposed to said light and a first end in said sample chamber; and a light collector located to collect light scattered by particles in said fluid flow and direct said collected light to said light detecting element; the optical components of said light collector consisting essentially of a single optical component; said inside surface of said aperture assembly configured to reflect light so that essentially none of said light reflected from said inside surface is capable of directly illuminating said light detector, thereby reducing optical noise in the system for detecting particles.