The purpose of this control is to adjust the position where scanning starts in the horizontal direction (main scan direction) of the image with reference to the hori-

zontal synchronization signal (/BD) sent from the BD sensor in the laser scanner. The horizontal synchronization signal is also used as a vertical synchronization

signal to recognize the leading edge of paper. Upon detection of arrival of the fed paper at the prescribed position, the DC controller PCB starts sending the /BD

signal to the image porcessor PCB. The image processor PCB recognizes the leading edge of paper at the start of the continuous /BD signal; it recognizes the trailing

edge of paper at the end of the continuous /BD signal.

MEMO:

About Generation of BD Signal

The BD sensor on the BD circuit board receives only the beam of laser B; it does not receive the beam of laser A. The BD signal is generated from the beam of laser A.

5.2.2 Controlling the Intensity of Laser Light

5.2.2.1 Automatic Photocurrent Control (APC)

The purpose of this control is to monitor the laser beam emitted to the photodiode on the laser driver circuit board in order to adjust the light quantity.

Laser control signal

Laser status

CTL2

CTL1

CTL0 Laser A

OFF

Video signal input

enable

OFF