A STATISTICAL STUDY OF DIRT-COUNT MEASUREMENT SYSTEM VARIATION USING OPTICAL-SCANNER-BASED IMAGE-ANALYSIS

Optically-based systems have been introduced to replace traditional vi sual methods for quantifying the amount of finely divided ink particle s that show up as visible specks in pulp. There is no standard method for evaluating the accuracy and precision of these new systems, but th e authors present a general method for the quantitative comparison of two ''dirt count'' measurement systems. The variation in the measureme nt system was reduced significantly using a Hewlett Packard ScanJet II c as the scanning device in place of the earlier ScanJet Plus scanner when both were operated at 300 dpi. Variation was further reduced when the ScanJet IIc was operated at 400-dpi resolution. The ScanJet IIc a lso provided better accuracy.