Patent ID: 6091492
Filing Date: 2000-07-18
Classification: G01N

Abstract:
A method of obtaining particle size distribution data, comprising the steps of:(a) illuminating a group of dispersed particles with a dose of light in a collimated beam from a light source so as to scatter rays of said light beam;(b) passing at least a portion of said rays scattered by said particles during said illuminating step through a lens such that rays parallel to one another are focused at one location in a focal surface of said lens;(c) detecting at least a portion of said rays passing through said lens with a two dimensional array of light detectors positioned in the focal surface, wherein a substantial portion of the array of light detectors comprises a plurality of functionally equivalent, densely arranged photosensitive pixels;(d) selecting a series of at least twenty particle-size intervals per particle-size decade;(e) defining at least as many angle classes as there are particle-size intervals;(f) assigning each of a plurality of pixels to one or more of said angle classes according to the angle one of said rays scattered by said particles makes to said light beam in order to strike the pixel being assigned;(g) reading output data from said array into a storage device;(h) repeating steps (a), (b), (c), (f) and (g) for at least two exposures of said array, and, between said two exposures, changing the relative angle between the incident direction of said light beam and the optic axis of said lens, wherein said relative angle between the incident direction of said light beam and said optic axis of said lens is variable from approximately 0 degrees to approximately 180 degrees; and(i) processing said stored output data to obtain particle size distribution data with a resolution of said at least twenty particle-size intervals per particle-size decade.