3–27OPERATIONS AND TIMINGCOPYRIGHT © 1998 CANON INC. CANON NP6621 REV.0 FEB. 1998 PRINTED IN JAPAN (IMPRIME AU JAPON)B. Lens Drive System1. OutlineThe lens drive system is driven by the lens motor(M3), and the drive generated by the lens motor istransmitted to the blanking shutter exposure unitthrough a relay gear. (See p. 3-53.)To move the lens, the relay gear is engaged withthe lens gear by turning ON the change solenoid(SL1). When the lens motor rotates in the directionof the arrow in this condition, the lens moves in thedirection of enlargement ( ) because of the drivecoming through the relay lens gear and the lenscable.In reduction mode, the blank exposure shutteroperates according to the degree of movement ofthe lens, thereby blanking out both sides of the copyto suit the selected reduction ratio.The machine’s scanner lens home positionsensor (PS2) is located in the middle of the scannerlens drive rail so that the scanner lens home positionmay be detected quickly at power-on, therebyshortening the first copy time. (Additionally, a merepress on each Ratio button causes the scanner lensto move to the appropriate position to shorten thefirst copy time.)II. EXPOSURE SYSTEMA. Varying the ReproductionRatioThe reproduction ratio in the axial direction ofthe photosensitive drum is varied by the lens drivesystem, and that in the peripheral direction of thephotosensitive drum is varied by the scanner drivesystem.The lens drive system uses a zoom lens, and thereproduction ratio in the axial direction of the photo-sensitive drum is varied by changing both the posi-tion of the lens and the focal distance as shown inFigure 3-201.The scanner drive system moves the No. 1mirror faster in relation to the peripheral speed ofthe photosensitive drum (reduction) or slower(enlargement), thereby varying the reproductionratio in the peripheral direction of the photosensitivedrum.FF'F1F2F2'F1'DIRECTREDUCEENLARGEFigure 3-201
