CHAPTER 4 IMAGE FORMATION SYSTEMCOPYRIGHT © 1999 CANON INC. CANON NP6317 REV.0 APR. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)4-8IV. CONTROLLING DEVELOPING BIASA. OutlineThe circuit shown in Figure 4-402 controls the developing bias. Its main functions are as fol-lows:1. Switching the AC component of the developing bias ON/OFF.2. Regulating the voltage of the DC component of the developing bias.The copy density can be controlled by varying the voltage of the developing bias to suit thefollowing variables:1. Setting of the COPY DENSITY lever and recalibration dial2. AE sensor outputThe photosensitive drum gradually deteriorates with use, causing the potential (VL) of lightareas of the drum to increase, causing the copy density to be incorrect for a given setting of the copydensity lever. To compensate for this, a COPY DENSITY knob, which can be turned to raise theDC bias by exactly the increase in VL, and thus produce clear copies again.
