Sbu - Gestetner A294 Service Manual

IMAGE PROCESSING

2.3.2 SBU

OS4
Analog
Processing (Last)
OS3
OS2
Analog
Processing (First)
OS1
The CCD converts the light reflected from the original into an analog signal. The
CCD line has 7,500 pixels and the resolution is 600 dpi (23.6 lines/mm).
The CCD has four output lines: OS1, OS2, OS3, and OS4. OS1 and OS2 are for
the first half of the scan line (Non-operation side), and OS3 and OS4 are for the
last half of the scan line (Operation side). There are two analog processing ICs;
one handles the first half line (OS 1 and OS2) and the other handles the last half
line (OS3 and OS4). The analog processing IC performs the following operations:
1) Combines the odd and even signals into one line signal.
2) Adjust the black reference level of each CCD output channel.
3) Amplifies the analog signal from the CCD.
After the above processing, the analog signals are converted to 8-bit signals by the
A/D converter. This gives a value for each pixel on scale of 256 grades. Then, the
two 8-bit signals are sent to the SICU board through the LVDS (Low Voltage
Differential Signaling). The LVDS is a noise-resistant interface.
A294/A295
CÓPIA NÃO CONTROLADA
SBU
A/D 1
G A
A/D 2
2-18
CÓPIA NÃO CONTROLADA
L V D S
8-bit data
L V D S
8-bit data
SICU
IPU
A294D579.WMF
SM