Auto Density Adjustment (Ae); Outline; Measuring The Density Of The Original - Canon NP7160 Service Manual

F. Auto Density Adjustment (AE)

1. Outline

The copier is equipped with an automatic density adjustment mechanism (AE), which
controls the developing DC bias to suit the density of originals. As long as the original is of even
density, the AE mechanism is capable of ensuring copies free of fogging by changing the
developing DC bias to suit the density of the original.

2. Measuring the Density of the Original

In initial rotation state (INTR), the scanning lamp (LA1) is turned on at a specific intensity
and the scanner is moved forward 70 mm to expose the original. When the scanner has stopped,
the light reflected by the area shown in Figure 4-208 (in reference to the original butting
position) is measured by the AE sensor (photodiode), whose output is sent to the DC controller
PCB as the AE sensor output signal (AE_DATA).
Based on the signal, the DC controller PCB computes the optimum level of the developing
DC bias for copying, and sends the result to the high-voltage power supply PCB as the
developing bias control signal (DV_DC_CNT).
Area of AE detection
28 mm (approx.)
56 mm (approx.)
20 mm
(approx.)
70 mm
(distance of scanner travel)
COPYRIGHT © 1998 CANON INC.
Center of image
Figure 4-208
CANON NP7161/NP7160 REV.0 AUG. 1998 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 4 IMAGE FORMATION SYSTEM
4–21