2. Scanner section
A. How to scan documents
The scanner has sensors that are arranged in a line. These sensors scan a
certain area of a document at a time and deliver outputs sequentially. When
the line is finished, the next line is scanned, and this procedure is repeated.
The figure below shows the case where the latter two sections of an image
which are scanned are shown with solid lines and the former two sections
which are being transmitted are shown with dotted lines.
The direction of this line is called “main scanning direction,” and the scanning
direction “sub scanning direction.”
In the figure above, one line is divided into 4 sections. Actually, however, one
line is divided into thousands of sections. For scanning, the light receiving ele-
ment called CCD is used.
The basic resolution indicates the scanner capacity. The basic resolution is ex-
pressed in dpi (dot/inch) which shows the number of light emitting elements per
inch on the document.
The basic resolution of this machine is 400dpi.
In the sub scanning direction, at the same time, the motor that drives the op-
tical system is controlled to scan the image at the basic resolution.
B. Basic structure of scanner section
1
Copy lamp (Xenon lamp)
2
Reflector (light conversion plate)
3
No. 1 mirror
4
No. 2 mirror
5
No. 3 mirror
6
Lens
7
No. 2/3 mirror unit
8
Copy lamp unit
9
CCD
10
Mirror motor
11
MHPS (Mirror home position sensor)
The scanner unit performs scanning in the digital optical system.
The light from the light source (Xenon lamp) is reflected by a document and passed through three mirrors and reduction lenses to the CCD element
(image sensor) where images are formed. This system is known as the reduction image sensor system. Photo energy on the CCD element is con-
verted into electrical signals (analog signals). (Photo-electric conversion). The output signals (analog signals) are converted into digital signals (A/D
conversion) and passed to the MCU (main control/image process section). The resolution at that time is 400dpi.
The mirror unit in the scanner section is driven by the mirror motor.
The MHPS is provided to detect the home position of the copy lamp unit.
(6)
(5)
(4)
(3)
(2)
(1)
(10)
(11)
(9)
(8)
(7)
1
2
3
4
5
5
4
3
2
1
Sub scanning direction
Sensor scanning area
Main
scanning
direction
Original
Image data sent to the ICU PWB
To MCU PWB
3. Laser unit
The image data sent from the MCU (image process circuit) is sent to
the LSU (laser unit), where it is converted into laser beams.
A. Basic structure
The LSU unit is the writing section of the digital optical system.
The semiconductor laser is used as the light source, and images are
formed on the OPC drum by the polygon mirror and f
θ
lens, etc.
The laser beams are passed through the collimator lens, the cylindrical
lens, the polygon mirror, the f
θ
lens, and the mirror to form images on
the OPC drum in the main scanning direction. The laser emitting PWB
is provided with the APC (auto power control) in order to eliminate fluc-
tuations in the laser power. The BF PWB works for measurement of the
laser writing start point.
(1)
(2)
(3)
(4)
(5)
: Laser beam
path for BF PWB
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