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CHAPTER 3 EXPOSURE SYSTEM
B.
Controlling the Pre-Heating Mechanism of the Scanning Lamp
To reduce the time over which the scanning lamp reaches its optimum intensity after a press on the Copy Start key, the filament of the scanning lamp is supplied with power. This mechanism is called "pre-heating," and it may be standby pre-heating, pre-activation pre-heating, or activation pre-heating. 1. Standby Pre-Heating The filament is supplied with a voltage of 2.9 ±0.25 V after power-on, during initial rotation, and after copying. If the lamp turns on and then off at the end of copying, standby pre-heating is ended and it will be started as soon as the lamp heater turns on next time. Thereafter, standby pre-heating remains on until the next time the lamp turns on. Pre-Activation Pre-Heating The filament is supplied with a voltage of 4.35 ±0.45 V 1.5 sec before the scanning lamp is turned on for copying. Activation Pre-Heating The filament is supplied with a voltage of 3.8 ±0.4 V during copying. Thereafter, a voltage determined based on the intensity duty value read while the scanning lamp is on will be applied. 3. 2.
C.
Turning On and Off the Scanning Lamp
The scanning lamp is turned on and off by the scanning lamp on signal (FLPWM), scanning lamp clock signal (FLCLK*), and scanning lamp ON signal (FLONOUT) from the reader controller PCB.
D.
Controlling the Intensity of the Scanning Lamp
The FLPWM signal is a pulse signal, and the intensity of the scanning lamp is controlled so that it remains a constant level by changing the duty ratio of the signal according to the scanning lamp intensity signal (FL_S) detected by the intensity detection PCB and the scanning lamp VR setting.
3-8
COPYRIGHT © 1999 CANON INC.
CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
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