CHAPTER 2 NEW FUNCTIONS2-90 COPYRIGHT © 2001 CANON INC. 2000 2000 2000 2000 CANON iR8500/7200 REV.1 AUG. 2001b. Shading AdjustmentIn this adjustment, the density of white paper and that of the standard white plate are mea-sured, and the results are stored in memory.The data is computed for use as the target level during shading correction. The adjustmentis designed for service mode and is used upon installation of the machine, after replacementof the scanning lamp, or when correcting changes in the intensity of the scanning lamp oc-curring over time.c. Shading CorrectionThis correction is executed each time an original is scanned. The density of the standardwhite plate is measured and the result is compared against the target value stored in theshading correction circuit. The difference is used as the shading correction value, which willbe used to correct the variation in CCD pixels, thereby ensuring a specific level of imagedensity.F02-503-02CCD outputOriginal densityStandard white plateCharacteristicsbefore correctionTarget valueResults ofmeasurementCharacteristicsafter correctionWhite
