Analog Image Processing; Outline; Driving The Ccd - Canon Image Reader-A1 iR5000i Service Manual

CHAPTER 3 IMAGE PROCESSING SYSTEM

2. Analog Image Processing

2.1 Outline

Analog image processing is performed by the CCD/AP PCB, which has the following
major functions:
[1] Drives the CCD.
[2] Corrects the gain in the CCD output, corrects offset.
[3] Performs A/D conversion of CCD output.
CCD
Odd-number pixels Even-number pixels
Analog image
signal
Analog signal
processing unit
· Gain correction
· Offset correction
CCD/AP PCB

2.2 Driving the CCD

The machine's CCD sensor is a single-line linear image sensor, and is composed of 7450
pixel photo cells.
The signals subjected to phtoconversion in the light-receiving segment are sent out in two
types of analog signals: even-number (EVEN) pixels and odd-number (ODD) pixels.
Shift register
Light receiving
segment
(photodiode)
Shift register
3-2 R
CCD drive
control
Even-number
pixels A/D
conversion
Odd-number
pixels A/D
conversion
F03-201-01
Gate
6 5 4 3
Gate
F03-202-01 CCD Block Diagram
COPYRIGHT © 2001 CANON INC.
J6001
A12V
A5V
J6002
CCD control signal
Gain/offset
correction data
Digital image signal
Digital image signal
Output buffer
Odd-number pixel data
2 1
Even-number pixel data
Output buffer
2000 2000 2000 2000
J5002
J5003
Reader
controller
PCB
8
8
CANON iR5000i/iR6000i REV.0 JUNE 2001