Sharp AR-651 (serv.man23) Service Manual ▷ View online
AR-651/810 SCANNING SECTION 6 - 14
The reflection type photosensor is comprised of an infrared light emitting diode and a phototransistor. It
uses the pulse modulation to detect an original.
The light emitting diode is driven by a pulse having a 130-µsec cycle and an 8-µsec ON time. When the
phototransistor receives the same signal as this pulse, it is determined that there is an original. The
pulse modulation is performed inside the reflection type phototransistor.
About reflection type photosensor
130µsec
LED
8µsec
Original
Phototransistor
AR-651/810 IMAGE PROCESSING 7 - 1
7. IMAGE PROCESSING
7. 1. General Description
The following diagram shows the process from scanning of the original to data writing on the photoconduc-
tive drum surface of the digital copier.
ASIC stands for “Application Specific IC”, meaning an IC designed for a particular use.
The followings are the boards used for the image processing.
Board
Number of image
Function
processing ASIC
SLG board
(PWA-F-SLG-340)
1
PLG board
1
(PWA-F-PLG-340)
Image processing/
writing control
section
[PLG]
Image processing section
Photo
conductive
drum
System
control section
[SYS]
Image
processing
section
[SLG]
Scanning section
Original
Original glass
Scanning
section
[CCD]
Semi-
conductive
laser element
conductive
laser element
Laser drive board
[LDR]
Writing section
Polygonal motor
High-quality image processing, image memory editing, editing
processing, gamma correction, gradation processing, external
output system interface
Smoothing processing, external input system interface, image area
control, laser related control
Machine
control section
[LGC]
AR-651/810 IMAGE PROCESSING 7 - 2
7. 2. Image Processing Circuit
7. 2. 1. General description
The image of an original placed on the original glass is scanned by the carriage. The CCD (Charge Coupled
Device) reads the optical image signals and converts them into the electrical signal. The electrical signals
then undergo the analog-to-digital conversion and are changed into digital signal. The shading correction
(correction of variance in CCD elements and the light source) is performed on the digital signal, then it is
output as an image signal from the scanning section.
The image processing section receives this image signal from the scanning section and applies various
types of image processing to it, then sends the output result to the writing section.
Images are processed by the SLG board (PWA-F-SLG-340) and PLG board (PWA-F-PLG-340).
(1) Image processing circuit on the SLG board
One image processing ASIC is mounted on the SLG board, realizing the following functions:
<Functions>
High-quality image processing, image memory editing, edit processing, gamma correction,
gradation processing and external output system interface
(2) Image processing circuit on the PLG board
One image processing ASIC is mounted on the PLG board, realizing the following functions:
<Functions>
Smoothing processing, external input system interface, image area control and laser related control
AR-651/810 IMAGE PROCESSING 7 - 3
7. 2. 2. Configuration
The following diagram shows the image processing section of this copier.
Configuration of image processing section
CCD board
(PWA-F-CCD-340)
(PWA-F-CCD-340)
CCD
A/D conversion
Image processing ASIC for scanner section
High-quality image processing
Image memory editing
Editing processing
Gamma correction
Gradation processing
External output system interface
SLG board
(PWA-F-SLG-340)
(PWA-F-SLG-340)
SYS board
(PWA-F-SYS-340)
(PWA-F-SYS-340)
Sorting, group copy, magazine
sorting, 2in1/4in1 (single-sided/
double-sided), image composi-
tion, date insertion, sheet
insertion mode, etc.
sorting, 2in1/4in1 (single-sided/
double-sided), image composi-
tion, date insertion, sheet
insertion mode, etc.
PLG board
(PWA-F-PLG-340)
(PWA-F-PLG-340)
Image processing ASIC for printer
section
Smoothing processing
External input system interface
Image area control
Laser related control
Laser drive board
(PWA-F-LDR-340)
(PWA-F-LDR-340)
Image data flow
Image processing
section
section
Laser drive
Shading correction
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