Image Sensor Drive Circuit - Epson FilmScan 200 Service Manual

2.3.5 Image Sensor Drive Circuit

Figure 2-21 is a block diagram of the image sensor drive circuit. Gate array E02A14 (IC4) controls image
sensor operation. The sensor receives the following control signals: the SP signal, which drives the main
sensor's shift electrode; transmission pulses CLK, which transmit the signal charges (and which are
described, as ƒÓ1 and ƒÓ2, in Section 2.1.1); and the RS reset signal, which resets the image sensor's
output section following the reading of each pixel. The image sensor receives these control signals, and
outputs the image data as signal Vout. The process is illustrated in Figure 2-22.
The image data output by the image sensor is in the form of an analog signal. ms signal is passed
through an amplifying circuit.
The analog signal output from the amplifier is passed into the 10-bit A/D converter and converted into 10-
bit digital data. This data is sent to gate array E02A14 (IC4). Details of subsequent image pressing may be
found in section 2.3.1.
The original image frame must be illuminated to be read. The scanner uses fluorescent lamps for this
purpose. These lamps are also controlled by gate array E02A14. The gate array provides switching in
order to maintain the proper radiation intensity (Refer to Figure 2-23.).
Vout
SH
CLK
RS
CCD
Sensor
Optical Unit
Rev. A
A/D
AMP
Converter
Figure 2-21. Image Sensor Drive Circuit
OPERATING PRINCIPLES
10-bit data
AD0-9
SH
SNCLK
RS
ASIC
E02A14 (IC4)
B028 MAIN Board
2-17