Epson GT-30000 Series, Service Manual

Page: 25 / 93

A3 Size Color Flat Bed Scanner GT-30000 Revision A
OPERATING PRINCIPLES Electrical Circuit Operations 25
2.3 Electrical Circuit Operations
2.3.1 Control Circuit Operation
The control circuits of this scanner are (See "Figure 2-3. Control Circuit
Composition of GT-30000"):
" PBA-MAIN board (Main control circuit board)
" PBA-ISN board (CCD sensor board located on the CR)
" PWS-POWER board
" PBA-CONNECT board (Relay board)
" PBA-PANEL board (Control panel)
"
PBA-LAMP board (Lamp board)
Among the various functions controlled by the PBA-MAIN board as well as the
PBA-ISN, these boards control the scanning process from the CCD sensors to
the image signal processing as described below.
1. PBA-MAIN Board (document size detection)
! Document size sensors detect the size of the document.
2. PBA-ISN Board (CCD image sensor)
! Photoelectric conversion:
Converts light reflected from the document (light energy) into electrical
energy (electrical charge).
! Amplification
3. PBA-MAIN Board (processes image data)
ASIC (IC2) on this board manages most of the following functions:
! A/D conversion:
Converts the image data produced in the form of analog electrical
signals into 12-bit digital data.
!
Shading correction:
Performs image data correction on a black and white basis.
! Processes the image data according to various setting information
provided by the host, such as gamma correction, color correction, and
halftoning correction.
After completing these processes, image data is output to the host.