Patent ID: 7675615

Claim:
A method for calibration of length measurement systems providing probability density functions (PDFs) for tapered beards, comprising: forming a tapered beard subsample from a bulk sample of at least one sample of known, monolength staple fibers, the fibers of the bulk sample having diameter and surface properties similar to those of a subsequent sample under test having unknown length distributions; measuring the uncalibrated amount versus distance response for each such monolength group; developing correction functions from each such monolength sample to provide calibrated amount versus distance for said monolength fibers; storing said calibration functions and interpolations thereof in a computer memory; forming a tapered beard subsample of unknown length fibers and measuring the uncalibrated amount versus distance response; correcting the uncalibrated amount versus distance response for said unknown tapered beard to produce a calibrated amount versus distance response; determining the second derivative of said calibrated amount versus distance response for said unknown tapered beards; normalizing and filtering the second derivative to produce a calibrated PDF for the unknown subsample; and calculating from said calibrated PDF any length data products desired.