Canon imagePRESS C1 P, Service Manual, Page: 340 / 1265

Chapter 6
6-6
6.3.2 Controlling the Intensity of Laser Light
6.3.2.1 APC Control
0012-7586
imagePRESS C1 P / imagePRESS C1 / imagePRESS C1+ (Printer) / imagePRESS C1+
In the APC control, the laser is controlled to keep the constant light intensity by adjusting the laser diode output on the laser driver.
This control is executed with the DC controller PCB.
The DC controller PCB output the laser signal to the laser driver IC in the laser driver PCB.
Herewith, the APC mode is set to the laser driver IC, and the laser diode (LD) is compulsorily emitted.
At the same time, the laser driver IC monitors the laser diode (LD) with the photo diode (PD), and it adjusts the laser diode output until the light intensity becomes
constant.
F-6-7
[1] Laser Driver IC
DC-CON: DC Controller PCB
6.3.2.2 PWM Control
0012-7589
imagePRESS C1 P / imagePRESS C1 / imagePRESS C1+ (Printer) / imagePRESS C1+
The PWM control determines the laser lighting time depending on the image data transmitted from the main controller PCB.
The laser lighting time (see Note) is selected at the DC controller PCB, and it determines the one pattern from 30-level of lighting patterns for each pixel.
MEMO:
The relationship between the laser lighting time and the image density is shown below.
With this machine, the laser is exposed to the dark area (image area), not to the bright area (non-image area).
When the image density gets higher, the laser lighting time becomes longer, whereas when it gets lower, the time becomes shorter.
F-6-8
6.3.3 Controlling the Laser Scanner Motor
6.3.3.1 Laser Scanner Motor Control
0012-7592
imagePRESS C1 P / imagePRESS C1 / imagePRESS C1+ (Printer) / imagePRESS C1+
The laser scanner motor control is used for rotating the scanner motor with the specified speed.
This control is executed at the motor speed control block in the DC controller PCB and the standard signal generation block.
The motor speed control block detects the speed detection signal (FG, BD), and controls the acceleration signal (ACC) and deacceleration signal (DEC) to be the
specified speed by comparing the standard signal generated in the standard signal generation block.
With this machine, in order to shorten the scanner motor control time, the speed detection point is switched depending on the printer condition. FC signal is the
detection signal for roughly adjusting the motor speed, and it is used when turning on the power or at the last rotation.
BD signal is the detection signal for finely adjusting the motor speed, and it is used at printing.
Laser Driver
[1]
LD
LD
PD
DC-CON
J3500 J1170
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