Chapter 55-14F-5-265.3.6.2 CCD Drive 0006-5931iR2270 / iR2870 / iR3570 / iR4570 / / iR2270N / / iR2870N / / iR3570N / / iR4570N / iR2230 / / / iR3530 /The machine's CCD sensor is a 1-line linear image sensor consisting of 7488 photocells. After completion of photoelectric conversion in the light-receiving block,the signals are output to the AP circuit in the reader controller circuit board in parallel for each channel (total eight channels) of the CCD array.F-5-275.3.6.3 Gain Correction and Offset Correction of the CCD Output 0006-5932iR2270 / iR2870 / iR3570 / iR4570 / / iR2270N / / iR2870N / / iR3570N / / iR4570N / iR2230 / / / iR3530 /The analog video signal generated by the CCD is corrected so that it will have a specific level (gain correction); moreover, the output voltage occurring in the ab-sence of incident light is also corrected so that it will have a specific level (offset correction).5.3.6.4 A/D Conversion of the CCD Output 0006-5933iR2270 / iR2870 / iR3570 / iR4570 / / iR2270N / / iR2870N / / iR3570N / / iR4570N / iR2230 / / / iR3530 /The analog video signal is further converted into a digital signal that is suited to the voltage level of individual pixels by the A/D converter.5.3.6.5 Shading Correction (outline) 0006-5936iR2270 / iR2870 / iR3570 / iR4570 / / iR2270N / / iR2870N / / iR3570N / / iR4570N / iR2230 / / / iR3530 /The output of the CCD is not necessarily even for the following factors even when the density of the original is uniform:1) Variation in the Sensitivity Among Pixels of the CCD2) Variation in the Intensity of the Rod Lens ArrayThe machine executes shading correction to even out the output of the CCD. Shading correction may be shading adjustment executed at power-on or shading cor-rection executed for each job.5.3.6.6 Shading Adjustment 0006-5937iR2270 / iR2870 / iR3570 / iR4570 / / iR2270N / / iR2870N / / iR3570N / / iR4570N / iR2230 / / / iR3530 /In this adjustment, the machine measures the density of the standard while plate, and stores the results in memory as density data. It then performs computationson the shading data, and uses the result as the target value for shading correction.CCD(1 line)AnalogimagesignalAnalog imageprocessing-gain correction-offset correctionA/DconversionCCDdrive controlCCDcontrol signalGaincorrectiondataDigitalimage signalCCD/AP circuit10Digitalimage signal8Reader controller PCBContact image sensor CIS)Target valueJ502EEP-ROMSRAMCPUShadingcorrectionCCD7 CCD5 CCD1CCD2CCD8 CCD6HL L HH L HL H H LoutputLight-receiving block
