| abstract |
A particle counter (10) passes a sample stream of particles (72) through an elongated, flattened nozzle (16) and into a view volume (18) formed by an intersection of the sample stream and a laser beam (13). Scattered light (24) from the view volume is focused onto a linear array (32) of photodiode detectors (40) positioned such that a longitudinal length (70) of the view volume is imaged on the detectors. Because the sample stream produces nonuniform particle velocities along the longitudinal dimension of the view volume, for same-sized particles higher velocity particles will generate lower output amplitude signals than lower velocity particles. Therefore, the gain associated with each photo-detector element is adjustable to compensate for the nozzle velocity differences, laser beam intensity differences caused by beam divergence and fluctuations, optical path efficiency variations, and photo-detector element-to-element sensitivity differences. |