Scanner Mechanism Operation; Mechanism - Epson STYLUS Scan 2000 Service Manual

EPSON Stylus Scan 2000

2.3 Scanner Mechanism Operation

2.3.1 Mechanism

The figure below describes how the light reflected off the document passes
through the lens and reaches the CCD and how the CCD reproduce an image.
The CCD reads the light, converts light into various analog data according to
the strength of the light, and sends this various analog data to the MAIN
board. The analog data received by the MAIN board is converted into digital
data, and after being processed, the digital data is sent to the host.
Cooling Cathode
Fluorescence Lamp
Lens
CCD
Figure 2-18. Scanner Operating Principle
2.3.1.1 Video Circuit
The video circuit of the scanner mechanism has a CCD drive circuit and a CCD
signal process circuit.
1. CCD drive circuit
The CCD drive circuit generates the appropriate signal for the CCD so that
the CCD can accurately read the image.
2. CCD signal process circuit
The CCD signal processor contains the circuits that are necessary for
adjustment and sampling of the three channels. Each signal from CCD goes
through CDS (correlated doule sampling) to PGA (programmable gain
amplifier). Each R, G, B signal, after having gone through PGA, is selected
by multiplexer, converted from analog data to digital data by 10-bit A/D
Converter (ADC), and then is output to the B101 MAIN board.
Operating Principles
Analog
Signal
Digital
Signal
MAIN
Board
Scanner Mechanism Operation
R
CCD
G
B
Figure 2-19. CCD Signal Process Circuit
2.3.1.2 Scanner ASF Sensor Input
Sensor Input includes the ASF paper edge sensor.
Host
The leading edge of the paper is loaded by hand through the front paper edge
guides. When the paper enters the scanner feed path, it pushes the sensor flag
which activates the ASF paper edge sensor. The ASF motor then feeds the
paper roughly a quarter of an inch.
CDS
PGA
CDS
PGA
ADC
MUX
CDS
PGA
CCD Signal Processor
Revision A
Digital
Signal
OUT
46