Toshiba 4580, Service Manual

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6570/5570 IMAGE PROCESSING 6 - 2 Mar. 1999 © TOSHIBA TEC
6.2 Image Processing Circuit
6.2.1 Overview
Unlike existing analog copiers where reflected light is projected directly to the photosensitive drum,
digital copiers project reflected light (from the original document) to the Charged Coupled Device (CCD).
The CCD converts optical images into electrical signals which ultimately undergo shading correction
which is nothing more than compensations for variance in the light source and the CCD unit.
After shading corrections are made, signals are sent to the image processing section where processing
operations are performed. Data are then sent to the printer section for conversion into light beam that are
directed to the photosensitive drum for printing of the latent image.
The image processing operation is performed by the SLG board (PWA-F-SLG-300) and PLG board
(PWA-F-PLG-300).
(1) Image processing circuit on the SLG board
One image processing ASIC is mounted on the SLG board and implement the following functions:
<Functions>
High quality image processing, image memory editing, editing processing, gamma correction, tone
processing, external output system interface
(2) Image processing circuit on the PLG board
One image processing ASIC is mounted on the PLG board and implements the following functions:
<Functions>
Smoothing processing, external input system interface, image area control, laser related control