Typewriting machines – Including control of format and selection of type-face by... – Including editing or revision system
Reexamination Certificate
2000-02-28
2002-04-16
Hilten, John S. (Department: 2854)
Typewriting machines
Including control of format and selection of type-face by...
Including editing or revision system
C400S074000
Reexamination Certificate
active
06371669
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a printer controller of color printer; more specifically, a printer controller that detects relative dislocation among colors in an electro-photographic tandem color image generator that uses a plurality of photosensitive elements. The detection of color dislocation is for the purpose of precise color alignment on a recording medium.
BACKGROUND OF THE INVENTION
A data flow of in a conventional color image forming device is shown in FIG.
10
.
An electro-photographic printer
31
generates an image based on print data delivered from a personal computer
30
(or a CAD, a work station, a digital camera or the like) to the printer
31
via an interface.
The printer
31
is formed of a printer controller and a color image generator (sometimes referred to as “printer engine”, depending on situation).
The printer controller receives print data of a document to be printed delivered in the form of a mixture of print language and bit map data, or the like, and converts the data into raster data to enable a printer engine form an image. The printer engine forms a latent image in accordance with the raster data delivered form the printer controller. An image is thus created.
An image forming process in the electro-photography is described more in detail. A photosensitive drum, or an image carrier, is charged by a charger, and then irradiated with light in accordance with image information. A latent image thus formed is developed by a developer to become a toner image, which image is transferred on paper, or such other material that is an object of the transfer (hereinafter referred to as “transfer material”).
A tandem color image former as illustrated in
FIG. 11
is proposed to better meet the needs of color image era.
As shown in
FIG. 11
, the color image generator comprises four image generating devices (hereinafter referred to as “imaging station”)
1
a,
1
b,
1
c,
1
d,
each of the imaging stations
1
a,
1
b,
1
c,
1
d
is provided with a photosensitive drum (photosensitive element)
2
a,
2
b,
2
c,
2
d,
respectively. Disposed around the drum includes a charger
3
a,
3
b,
3
c,
3
d,
a developer
4
a,
4
b,
4
c,
4
d,
a cleaner
5
a,
5
b,
5
d,
5
d,
an exposure device having scanning optical system
6
a,
6
b,
6
c,
6
d,
and a transfer device
8
a,
8
b,
8
c,
8
d
for transferring toner image on a transfer belt
12
, which being a part of transfer means
7
.
At imaging stations
1
a,
1
b,
1
c,
1
d,
an image is formed in yellow, in magenta, in cyan and in black, respectively. Exposure devices
6
a,
6
b,
6
c,
6
d
irradiate exposure lights
9
a,
9
b,
9
c,
9
d,
respectively, corresponding to the yellow image, magenta image, cyan image and black image.
Underneath the photosensitive drum
2
a,
2
b,
2
c,
2
d,
an endless transfer belt
12
is provided, supported by rollers
10
and
1
. The belt circulates in a direction as indicated with an arrow A.
A pattern detection device
14
is provided facing the transfer belt
12
for detecting a location detection pattern generated by location detection pattern generating means
13
.
Transfer materials
17
stored in a paper dispenser cassette
16
are delivered via a paper feeding roller
18
to a transfer roller
19
, a fixer
20
, eventually to a paper tray (not shown).
In a color image generator of the above configuration, a black latent image is formed at the imaging station
1
d
on the photosensitive drum
2
d
by a known electro-photographic process. The latent image is developed at the developer
4
d
with a developer material containing black toner into visible black toner image. The black toner image is transferred at the transfer device
8
d
on the transfer belt
12
.
While the black toner image is being transferred on the transfer belt
12
, a cyan latent image is formed at the imaging station
1
c.
The latent image is developed at the developer
4
c
with a cyan toner into visible cyan toner image. The cyan toner image is transferred at the transfer device
8
c
to be overlaid on the black toner image.
Magenta toner image and yellow toner image formed through the same procedure are likewise transferred on the transfer belt
12
. When the toner images of four colors are overlaid into a single image on the transfer belt
12
, the complete toner image of four colors is transferred by the transfer roller
19
on paper or other such transfer material
17
delivered via feeding roller
18
from the paper dispenser cassette
16
. The transferred image is fixed by heating at the fixer
20
as a full-color image on the transfer material
17
.
After finishing the image transfer, the residual toner staying on the photosensitive drum
2
a,
2
b,
2
c,
2
d
is removed by a cleaner
5
a,
5
b,
5
c,
5
d,
and the photosensitive drum is ready for the next image formation.
The tandem color image generator of the above described configuration is advantageous in that it can provide color images at a high speed, since the image generator has independent imaging stations
1
a-
1
d,
each capable of forming a color image.
The above described tandem color image former, however, has a problem in how to precisely overlay respective images formed at independent imaging stations
1
a-
1
d
(viz. registration). The relative dislocation existing among the four color images transferred on the transfer material
17
eventually reveals itself as the dislocation or the color change in a finished picture.
There are five kinds of dislocations in the transferred image. FIG.
12
(
a
) illustrates a dislocation in the direction of transfer (the direction indicated with arrow symbol A) of transfer material (hereinafter referred to as “sub scanning dislocation”); FIG.
12
(
b
) illustrates a dislocation in the direction of scanning (direction perpendicular to the arrow symbol A) (hereinafter referred to as “main scanning dislocation”); FIG.
12
(
c
) illustrates a dislocation in an oblique direction (hereinafter referred to as “skew error”); FIG.
12
(
d
) illustrates a dislocation caused by an error in the magnification factor; and FIG.
12
(
e
) illustrates a dislocation due to curve error. In practical cases the dislocation appears as an integration of these causes.
The sub scanning dislocation shown in FIG.
12
(
a
) stems mainly from dislocated installations of imaging stations
1
a-
1
d,
optical scanning systems, and dislocation of constituent lenses and mirrors (not shown) within the scanning optical system or such other reasons that come from mechanical causes. The main scanning dislocation shown in FIG.
12
(
b
) also stems from the same reasons. The dislocation in an oblique direction shown in FIG.
12
(
c
) is due to a dislocated angle of a revolving shaft of a photosensitive drum in the imaging stations
2
a-
2
d,
or dislocated installation of the optical scanning system. The dislocation due to error in the magnification factor shown in FIG.
12
(
d
) stems from the variation in the length of scanning line caused as a result of an error in the length of light path from respective optical scanning system to the photosensitive drum
2
a-
2
d
at imaging station
1
a-
1
d.
The dislocation due to the curve error shown in FIG.
12
(
e
) is caused by a dislocated assembly of lenses, or the like within optical scanning system. Namely, in all of the above cases, the errors are due to mechanical factors.
SUMMARY OF THE INVENTION
A printer controller for delivering print data to a color image generator containing a plurality of image forming devices. The printer controller comprises
a receiving buffer region for receiving a certain print data delivered from a source of data input,
a display list region for storing, as a description list covering at least one print page, the print data stored in the receiving buffer region,
a raster data storage region for storing, as raster data, the print data kept in the display list region, and
a corrected raster data storage region for storing the raster data stored in the raster data storage region after being corrected by a skew.multi
Chau Minh H.
Hilten John S.
LandOfFree
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