Toshiba 4580, Service Manual

Page: 90 / 379

Mar. 1999 © TOSHIBA TEC 6 - 9 6570/5570 IMAGE PROCESSING
6.5 Scanner
Light that is reflected from the original document’s surface is directed to the CCD where photovoltaic
conversion occurs. During this operation, optical image data are converted into electrical signals which
are then converted into digital signals by the A/D conversion portion of the image processing system.
(1) Photo-voltaic conversion
A conversion from optical signals to electrical signals performed by the CCD. See Chapter 7, 6-1.
(2) Signal amplification
The amplification of the electrical signals from the CCD.
(3) A/D conversion
The conversion from Analog signals to Digital signals.
(4) Shading correction
Corrections made by the shading compensation circuit to make up for distortions of images produced
by the mirrors and the elements of the CCD. See Chapter 7, 6-2.
6.6 Printer
Image signals processed by the PLG board perform the laser writing operation through the writing con-
trol ASIC and the laser drive board processings.
(1) Setting of effective image area .........................
•
The top, bottom, left and right margins are set.
(2) Synchronization Clock Generation block ..........
•
HSYNC and the reference clock signal at printer
of horizontal synchronizing signal (HSYNC) block synchronized with the signal.
(3) Laser drive block ...............................................
•
ON/OFF control of the semiconductor laser and
DAPC (Double Auto Power Control) control.
CCD
Signal
amplification
A/D
conversion
Shading
compensation
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