The LINT signal varies the pulse duty between 10% and 57.6% according to thesetting of the Copy Density key or the density of the original, sensitivity of the drum andthe setting of the intensity control VR so that the supply voltage to the scanner variesbetween 45 and 65 V (effective value) by way of exerting phase control.Figure 4-106c. Detecting the Activation of the Scanning LampThe activation detection signal generates the ON detection signal (CVRON) at alltimes as long as the scanning lamp remains ON. The CVRON signal is sent to the errordetection circuit of the DC controller PCB. If the lamp ON signal (LAON) goes ‘0’because of a short circuit or the like in the activation circuit and the scanning lamp turnsON, the DC controller PCB causes the PWOFF signal to go ‘0’. This condition turns OFFthe relay in the power switch to turn OFF the power switch (SW1), thereby cutting off theAC power to the lamp regulator.3. Automatic Exposure Control (AE)The copier is equipped with an automatic exposure function that automatically con-trols the intensity of the scanning lamp according to the density of the original.When copies are made in AE mode, copies free of fogging may be obtained withouthaving to adjust the copy density for different originals. The lamp intensity controlled inAE mode is indicated by the copy density indicator on the control panel.a. Points of AE MeasurementDuring AE rotation (AER), the scanner is moved forward 120 mm while keeping thescanning lamp ON; when the scanner moves in reverse, the drum surface potential cor-responding to the four points on the copyboard is measured, and the measurements aresent to the DC controller PCB.The DC controller PCB computes the average from the surface potential measure-ments to determine the intensity of the scanning lamp for copying.Figure 4-1074 3 2 130 30 30 30 mm120 mm10% pulse duty100% pulse dutyCOPYRIGHT © 1997 CANON INC. CANON NP6045 REV. 1 MAR. 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)CHAPTER 4 IMAGE FORMATION SYSTEM4-7
