Patent ID: 6906799

Claim:
A method for processing a scattered light signal to determine the presence of particles in a scanned measurement volume, said method comprising the steps of: applying a scanning light beam onto a measurement volume; detecting scattered light pulses from particles moving through said measurement volume; and processing the detected light pulses, including the steps of: determining the existence of multiple pulse events representative of a scanned particle in a time domain by generating a corresponding particle pulse envelope (PPE) in order to segregate particles moving in the measurement volume from noise; said envelope generating step including steps of: identifying a second pulse adjacent to a first pulse in the time domain, said second pulse being spaced substantially one scanner period from said first pulse; and identifying a plurality of pulses adjacent to said first and second pulses indicative of a pulse envelope representative of a single particle in said measurement volume wherein said step of identifying a plurality of pulses includes the steps of forward and reverse autocorrelating said pulses over a predetermined time period to determine the size of said pulse envelope.