COPYRIGHT © 1999 CANON INC. CANON imageRUNNER 600 REV.1 JAN. 2000 PRINTED IN U.S.A. 6-9CHAPTER 6 IMAGE FORMATION SYSTEMD. Determining the Optimum Laser OutputThe laser output is determined so that the surface potential (light area potential VL) of the drumat time of laser exposure will be identical to the target potential.E. Laser Output Corrective ControlIf an optimum laser output cannot be selected after measuring the surface potential of the drumseveral times, a corrective control sequence is started to determine the optimum laser output.Figure 6-207 Sequence of Operations (corrective control)WMUPRWMUP STBY195˚C 200˚CPotentialsensorLaserReference outputReference output -10%-10%-20%-20%Measurement(VL1)Measurement(VL2) Measurement(VL3)PwVL1VL2VL3Laser outputThe relationship between the surface potential of thedrum (VL) and the laser output is determined basedon measurements taken several times.If the target VL is obtained atthis measurement, control isended; otherwise, correctivecontrol is stated.Activation usingthe reference outputdetermined at time ofshipment.Activation at an output 10%lower than the referenceoutput.The laser output (P)needed to attain the targetVL is determined.Developingbias (DC)Measurement(target VL)WMUPRWMUP STBY195˚C 200˚CPotential sensorDeveloping bias(DC)Laser-10% -20% Pw Pw1 Pw2 Pw3 Pw8VL1VL1 VL2 VL3 VL8VL-NGVL-NGVL2VL3Target VLMeasurement is continued by varying thelevel of the laser output so as to attainthe target VL. If the measurement is identical to thetarget VL, control is ended.Measurements are taken as manyas 8 times; at times, an approximate(to the target VL) may be used.Corrective control sequencestartedThe laser output needed toattain the target VL isdetermined.ReferenceoutputFigure 6-206 Sequence of Operations
