Patent ID: 8045162

Claim:
A method for determining the maximum intensities of interactions of a beam of a source of light with particles moving with a sample stream in a flow cell, said method comprising the steps of: (a) measuring actual peak intensities by performing individual raster scans across the sample stream, with rapid digitization and isolation of peaks from individual raster scans; and (b) calculating maximum intensities by correlating measured peak intensities from multiple adjacent raster scans and fitting the sequence of peak values to a curve that represents the profile of the laser beam in the direction of the moving sample stream, wherein said raster scans are carried out by an apparatus comprising: (1) a source of light; (2) a flow cell containing a moving sample stream, whereby particles in the sample move with the sample stream; (3) at least one optical element for focusing light from the source of light onto the particulate material moving with the sample stream in the flow cell; (4) a scanning device for deflecting the focused light from the source of light to enable the focused light to sweep back-and-forth across the moving sample stream; and (e) at least one detector channel to convert analog signals in an analog submodule in said at least one detector channel into digitized values and discrete, but closely spaced, time intervals, and a digital signal processing module (A) to select the highest digitization value from a cell interaction during a single raster scan (or a plurality of such values, if more than a single cell is present during a single raster scan); (B) to apply a known factor to the digitization value(s) thus selected, based on the position of the digitization value(s) along the raster scan, in order to effect any necessary residual intensity compensation of the scanning device not already executed in the analog submodule; (C) to correlate highest digitization value(s) across successive raster scans in order to reconstruct the peak value of the interactions between each cell and the source of light; (D) to apply programmatically predetermined numerical upper, lower, or upper and lower, thresholds specific to said at least one detector channel, to the peak values so reconstructed in order to select out of the population of detected events those that, within a particular assay, are most likely to represent the population of interest, and to reject or differently classify the remainder; and (E) to coordinate the information thus constructed and filtered, coming from said at least one detector channel, into a digital entity that contains time-stamp information as well as the reconstructed value from each detector channel involved in the measurement pertaining to the same individual detection event.