COPYRIGHT © 2001 CANON INC. 2000 2000 2000 2000 CANON iR2200/iR2800/iR3300 REV.0 MAR. 2001CHAPTER 3 IMAGE PROCESSING SYSTEM3-4 R3 Digital Image Processing3.1 OutlineDigital image processing is performed by the reader controller PCB, which has the fol-lowing major functions:[1] Shading correction[2] Auto density adjustment (AE)F03-301-013.2 Shading Correction3.2.1 OutlineThe output of the CCD will not necessarily be uniform because of the following factorseven if the density of the original in question is perfectly uniform:1) The level of sensitivity of a CCD pixel differs from that of another.2) The level of penetration of light differs between the center and the periphery of a lens.3) The intensity of the scanning lamp differs between the middle and the ends of thelamp.4) The scanning lamp is subject to deterioration.Shading correction is executed to correct discrepancies in the output of the CCD, and itmay be of either of the following two: shading adjustment used to determine a target level inservice mode and shading correction executed when scanning each original.To make up for the fluctuations in the intensity of light occurring at short intervals, edgearea gain correction is also executed.EEP-ROMSRAMCPU888J409Gain/offsetcorrection data· Shading correction· Auto densitycorrection (AE)· Serial/parallelconversiondigital imagesignalReader controller PCBdigital imagesignalEven-numberpixelOdd-numberpixelTargetvalueAnalogimageprocessingblock
