Mita-Kyocera FS175375 Electrophotographics system
Chapter Four OPERATION OVERVIEW
Chapter Four
Electrophotographics system 4-4
Amorphous-silicon drum 4-5
Charging the drum 4-6
Toner 4-7
Exposure 4-8
Scanner unit 4-10
Scanning laser 4-12
Development 4-14
Developing roller bias 4-20
Transfer 4-22
Fusing 4-23
Drum cleaning and erasing static charge 4-24
Typical photo process timing chart 4-25
Paper feeding system 4-26
Paper feed components/signals 4-27
Cassette feeding 4-28
Manual/multi purp ose tray feeding 4-29
Paper jam sensing 4-30
Basic engine functions 4.32
Basic sequence of operation 4-33
Engine controller system 4-34
Flash memory 4-34
High-voltage generator 4-34
Laser scanner control 4-35
Polygon motor control 4-35
Safety interlock 4-36
The engine gate array 4-37
Pin assignment 4-38
Power supply 4-42
OPERATION OVERVIEW
Logic controller system 4-44
Logic controller sp ecifications 4-45
Printing data processing 4-48
API ROM socket (U14) 4-49
API ROM socket pin assignment 4-50
System ROMs (U4 to U7) 4-51
RAM (U15 to U18) 4-51
Memory card slot interface 4-52
Option interface 4-52
Option interface pin assignment 4-54
Option interface pin assignment - Continued 4-55
Parallel interfa ce 4-56
Serial interface 4-56
Debugging outputs 4-57
Engine interface 4-57
Engine interface connector assignment 4-58
Signals used for the engine interface 4-59
Engine interface signals 4-60
Electrophotographics system
Electrophotography is the technology used in laser printing which transfers data representing texts
or graphics objects into a visible image which is developed on the photosensitive drum, finally
fusing on paper, using light beam generated by a laser diode.
The key features for the electrophotography system used in the printer are:
Operation overview
Electrophotographics system
!
600 dpi resolution
!
Newly developed amorphous silicon drum with no heating device
!
Diode laser scanning
!
Mono component toner
The electrophotography system of the printer performs a cyclic action made of seven steps as
shown below.
2 Exposure
1 Main Charging
3 Developing7 Erasing
6 Cleaning
4 Transfer
5 Fusing
4-4
FS-1750/FS-3750 Series
Operation overview
Electrophotographics system
Amorphous-silicon drum
The printer uses the long lasting amorphous silicon drum. The drum surface is a composite of five
substances coated in five layers as shown below.
A
B
C
D
E
AAAA
Secondary protection layer
BBBB
Primary protection layer (1µµµµm)
CCCC
Photoconductor αααα-Si
DDDD
Carrier block (1-3
EEEE
Aluminum base
The primary and secondary layers are for protecting the amorphous silicon layer underneath. The
amorphous silicon layer is of photoconductive, meaning it can be electronically conductive when
exposed to a (laser) light source to effectively ground electrons charged on its outer surface to the
ground. This layer is approximately 9µm thick.
The carrier block layer lies between the amorphous silicon layer and the aluminum base cylinder
and prevents the backward electron flow, from the base cylinder to the drum’s outer surface, which
might give adverse effect (usually “ghost”) on the print quality.
µµµµ
m)
Drum unit
4-5
FS-1750/FS-3750 Series
Operation overview
Electrophotographics system
Charging the drum
Figure below is a simplified diagram of the electrophotographics components. Charging the drum
is done by the main charger wire (in the main charger unit) marked A in the diagram.
A
B
As the drum (B) rotates in a “clean (neutral)” state, its photoconductive layer is given a uniform,
positive (+) electrical charge dispersed by the main charger wire (A).
Due to high-voltage scorotron charging, the cha rging wire can get cont aminated by oxidiz ation and
therefore must be cleaned periodically from time to time using the method explained in section
Main charger unit
such as black streaks caused by the oxide ac-cumulated around the charging wire.
on page 3-7. Cleaning the charging wire prevents print quality problems
4-6
FS-1750/FS-3750 Series
Operation overview
Electrophotographics system
Toner
The toner is fed from the toner pack TK-20/H. The toner is comprised of the following substances
as depicted below.
Single component toner TK-20/H
A B C D -
A
B
C
D
Resin
Ferrite
Silica
Polisher
4-7
FS-1750/FS-3750 Series
Operation overview
Electrophotographics system
Exposure
The charged surface of the drum (“B”) is then scanned by the laser beam from the scanner unit
(“A”).
A
B
4-8
FS-1750/FS-3750 Series
Operation overview
Electrophotographics system
The laser beam is switched on for a black dot and off for a white (blank) dot according to the print
data. Whenever it is illuminated by the laser beam, the electrical resistance of the photoconductor
is reduced, the potential on the photoconductor is also lowered to 20V, effectively driving the
charge through the a-Si layer down to the aluminum base.
LASER BEAM
+++++
a-Si LAYER
ALUMINUM
++++
----
240V-260V
LASER BEAM
++++
20V
0V
4-9
FS-1750/FS-3750 Series
Operation overview
Electrophotographics system
Scanner unit
The 600 dpi scanner unit includes the diode laser that produces the 670 nm wavelength laser beam.
This wavelength is specifically designed to match the photoconductive response of amorphous silicon.
+
To drum
'
&
%
*
$
#
(
)
"
4-10
FS-1750/FS-3750 Series
Operation overview
Electrophotographics system
"
Laser diode -
#
Collimeter lens -
$
Cylindrical lens -
%
Polygon mirror (motor) -
one scanned line width on the drum when laser beam scans on it.
&
Primary f-theta lens -
'
Secondary f-theta lens -
edges. The effective length of line (“A,” “B” below) the laser beam draws on the drum becomes longer as the laser beam
hits closer to the drum edges. In the figure below, distances represented by “A” and “B” are not the same (A>B) until the
f-theta lenses are provided between the polygon mirror and the drum (A’=B).
emits diffused, visible laser.
aligns the laser beam to the cylindrical lens.
compensates the slant angle at which the laser beam hits a polygon mirror segment.
has six mirror segments around its octagonal circumference; each mirror corresponding to
See below.
The primary (above) and secondary f-theta lenses equalize focusing distortion on the drum
(
Diversion mirror -
the drum.
)
Protective glass -
*
Sensor mirror -
+
Beam detect or sensor -
engine controller to start activating the paper feeding system.
diverts the laser beam vertically onto the drum. Note the diffused laser beam finally pin-points on
prevents dust, debris, etc., from entering the scanner assembly.
bends the very first shot of a laser scan towards the beam detection sensor (See next.).
when shone by the sensor mirror above, this photosensor generates a trigger signal for the
4-11
FS-1750/FS-3750 Series
Operation overview
Electrophotographics system
Scanning laser
The laser beam hits one of six polygonal mirrors. As the mirror revolves (at the revolution of
18,700 rpm for model FS-1750; 27,000 rpm for model FS-3750), the laser beam reflects off of it
and reaches the charged drum surface in a lengthwise manner.
A pair of (plastic) lenses provides focusing the horizontally sweeping laser beam onto the drum.
As the drum rotates, the laser beam sweeps the entire length of the drum so that the drum’s entire
circumference is exposed to the laser beam. The revolution of the polygon mirror motor and the
drum itself is timing-controlled so that each successive sweeping of the laser beam produces a
inch offset. The printer’s controller system continuously turns the laser beam on and off to put a
dot at every
1
/
inch distance horizontally. The diameter of a dot is typically 70 µm.
600
Synchronizing the output data with one scanning line is achieved by the photo sensor provided
next to the first mirror. At the beginning of each laser sweeping, the beam hits the photo sensor
which in turn sends a command to the logic controller for synchronization.
1
/
600
4-12
FS-1750/FS-3750 Series
Pseudo-1200 dpi Resolution Theory
Image Processing
Gray Scaler (Dither)
Image Processing
Operation overview
Electrophotographics system
Data Process in g Flow
Computer Controller
The amount of
data deployed in
VRAM for A4 at
600dpi
PCL etc.
1200dot/25.4mm×200mm=9449bit
287mm=13560bit
×
1200dot/25.4mm
PCL
KIR Light
Medium
Dark
Data Deployment in Video RAM
A4 size data
9449×13560
=16.02MB
PCL-6 Ver.1.1, HP LJ-6P (Supported by Kyocera printers)
PCL-6 Ver.2.0, HP LJ-4000 (Unsupported by Kyocera printers)
PCL-5e
PCL-6, Ver.2.0
PCL-EX (similar to PS/2)
4-13
FS-1750/FS-3750 Series
Operation overview
Electrophotographics system
KIR
600dpi(KIR OFF)
Jagged
representation
With KIR, dots of half or
quadruple sizes (grey
boxes at right) are
added or remove d
within the area of 7 by 3
dots.
Duration of laser emission
Light
Jagged dots are replaced by
the voids. The resultant printed
output becomes light (or thin).
Medium
Voids evenly replaces the
jagged areas. The resultant
printed output remain as the
original.
4-14
Dark
New dots are supplemented
around the jagged areas,
causing the resultant printed
output to be dark (or thick).
FS-1750/FS-3750 Series
Operation overview
Electrophotographics system
Gray scale and dither
Though monochrome printers can only render black or white (2-value) for a dot, it can provide 256 grey
scape levels on a cell that is constituted by 256 dots in a 16 by 16 cell. This cell is referred to as a pixel or a
half-tone cell. This method of recognising a pixel as a dot to prevent degradation of the printing resolution is
called the grayscale technique.
If dots placed within a pixel is expressed by the typical 2-value data, the data will be in 256 bits as
“01000110...” By expressing the number of dots to be placed in a pixel by a multi-value (FFh) data, dots
can fill a p ixe l in 8 b its. Th is sc he m e is ca lled th e “ dith er.”
For typical printer language, data are handled as follows:
Prescribe, PCL5e: 2 values (0, 1)
PostScript, PCL EX: Multi value (00h – FFh)
287mm(A4)=6780dot
×
600dot/25.4mm
600dot/25.4mm×200mm(A4)=4725dot
1Pixel (16dot)
As being a new
dot, this dot has
the 256-level of
grey.
1Pixel (16dot)
4-15
FS-1750/FS-3750 Series
Operation overview
Electrophotographics system
Gamma Correction Curve
For so me p r in t da ta , a d o t in a pixel is not a lway s re p re se n te d a s a d o t when it is p rin te d by the
printer; or, for example, 256 dots in a pixel could be represented as if dots were 256, resulting in
infid elity in th e pr in t ou tput.T h e Gam ma c or re ctio n cu r v e is u se d to co mpe n sa te th e numbe r o f
dots in the origin al p r int d a ta fo r th e o p timu m prin t q u ality.
Nu mb e r o f d o ts o u tp u t
Less dots for the image
(Printing gets lighter.)
More dots for the image
(Printing gets darker.)
256
0
Number of dots input
256
Line of screen and angle of screen
T h e lin e o f s cr ee n is th e n um ber o f th e lin es co n stitu e d b y a p ixe l o r s u b ce lls c o mpris in g a
pixel and expressed in line-per-pitch (lpi). The angle of screen is used to deform the cell,
giving a virtual enhancement in the number of lines (resolution).
T h e n u mbe r o f lin e s o f sc re en is a u to m atic ally d e te rmine d b y th e siz e o f th e ce ll. T h e mo r e th e
num ber of lines of screen, the less the size of the cell, the greyscale level is decreased, and the
resolution becomes high, and vice versa.
T h e lin e s o f sc re en h a s th e fo llo win g re la th ion s h ip w ith r es o lu tio n :
(Printer’s re solu tion/nu mb er o f lines of sc reen )
4-16
2
+1 = Level of greyscale reproduced
FS-1750/FS-3750 Series
45°/212 lines
8-dot pitch=50 lpi(300dpi)
Operation overview
Electrophotographics system
45°
Sub Pixel
4-dot pitch=212lpi
(424dpi)
45°/106 lines
16-dot pitch=75lpi
(150dpi)
8-dot pitch
=106lpi (212dpi)
63.4°/300 lines
8-dot pitch=150lpi
(300dpi)
16-dot pitch=75 lpi (150dpi)
45°
Sub Pixel
4-dot pitch=
300lpi (600dpi)
63.4°
Sub Pixel
8-dot pitch=150lpi
(300dpi)
3.57 dots=300lpi
(600dpi)
4-17
FS-1750/FS-3750 Series
Operation overview
Electrophotographics system
Pulse-sliced laser exposure technology
In XLI technology, the width of a pulse emitted as a dot is divided into eight segments each of
which varies according to the original data to be represented. This allows optimum laser exposure
for the drum according to the properties of the drum such as the sensitivity and development response. In overall, it is possible that the dots are consistently distributed over the photoconductor
in 1200 dpi resolution.
Pulse-sliced laser
4-18
FS-1750/FS-3750 Series
Development
Operation overview
Electrophotographics system
The latent image constituted on the drum is developed into a visible image. The developing roller
contains a 3-pole (
Toner attracts to the developing roller since it is powdery ink made of black resin bound to iron
particles. A magnetized blade positioned approximately 0.3 mm above the developing roller constitutes a smooth layer of toner in accordance with the roller revolution.
S-N-S
) magnet core and an aluminum cylinder rot ating around the magne t core.
Blade
Magnet
Magnetism
0.1mm
N
S
0.3-0.4mm
S
Drum
N
S
Developing roller
4-19
FS-1750/FS-3750 Series
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