Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
1999-11-15
2001-05-22
Brase, Sandra L. (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C347S250000, C399S196000
Reexamination Certificate
active
06236418
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims benefit of priority under 35 USC §119 to Japanese Patent Application No. 10-325032 filed in the Japanese Patent Office on Nov. 16, 1998, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus such as a digital copying machine, a digital printer, or a digital facsimile, and more particularly to a writing device to write image information on a photoconductive body to form an electrostatic latent image of an image thereupon by scanning luminous flux, emitted by a light source in response to an image signal of the image information, in a main scanning direction on the photoconductive body using a scanning device.
2. Discussion of the Background
A digital image forming apparatus includes a writing device to write image information on a surface of a photoconductive body traveling in a sub-scanning direction to form an electrostatic latent image of an image thereupon by driving a laser light source to emit luminous flux in response to an image signal corresponding to the image information using a write clock and scanning the luminous flux from the light source in a main scanning direction on the photoconductive body using a scanning device such as a rotary polygon mirror. The apparatus includes a developing device to develop the electrostatic latent image on the photoconductive body to a toner image and a transfer device to transfer the toner image on the photoconductive body onto a selected transfer paper.
In such a digital image forming apparatus, a magnification error in the main scanning direction is generally caused by an optical error in the writing device, a write clock error, an expansion or contraction of a transfer paper or other various causes. In order to correct such a magnification error in the main scanning direction caused by the optical characteristic of the writing device, some apparatuses use a variable write clock for driving a light source to emit luminous flux in response to an image signal. In such apparatuses, an expansion or contraction of an image due to an optical error of the writing device is measured and the write clock is adjusted according to a result of the measurement of the error such that the formed image has a predetermined length in the main scanning direction. The write clock adjusted and determined as described above is fixed other than when a further adjustment by a serviceman or other personnel is required.
An exemplary example of a digital image forming apparatus of a digital copying machine is described below. A digital copying machine shown in
FIG. 4
has an image reader
11
as an image reading device, a printer section
12
as an image forming section, and an automatic document feeder
13
. The automatic document feeder
13
conveys documents which have been set therein one by one onto a contact glass
14
and then discharges the document on the contact glass
14
after reading an image of the document.
The image reader
11
has a first carriage equipped with a light source including a lighting lamp
15
and a reflecting mirror
16
and a first mirror
17
, a second carriage equipped with a second mirror
18
and a third mirror
19
, a filter
20
, a lens
21
, and a line sensor
22
including a CCD as an imaging element.
When the image reader
11
reads an image of a document, the image of the document on the contact glass
14
is optically scanned by a travel of the first carriage at a fixed speed and a travel of the second carriage following the first carriage at a half speed thereof while the contact glass
14
is lighted by the lighting lamp
15
and the reflecting mirror
16
, by which a reflected light image is formed on the line sensor
22
by the lens
21
via the first mirror
17
, the second mirror
18
, the third mirror
19
, and the filter
20
.
The line sensor
22
photo-electrically converts the formed reflected light image of the document into electrical signals and outputs analog image signals, so that the image of the document is read. An ND filter is used as the filter
20
to read a single-color image. After a completion of reading the image of one sheet of the document, the first and second carriages return to a home position.
As the filter
20
, it is also possible to use red, green and blue color filters and sequentially change these three color filters in successive image readings so as to obtain red, green, and blue analog image signals sequentially from the line sensor
22
. Furthermore, it is possible to use a 3-line CCD having red, green, and blue color filters as the line sensor
22
.
The analog image signals from the line sensor
22
are converted to digital image signals by an analog-to-digital converter (not shown), subjected to various image processing, such as conversion processing from multi-level values to bi-level values, gradation processing, magnification processing, editing processing, etc., with an image processing board
23
as an image processing device, and sent to a semiconductor driving board (not shown).
While a photoconductive drum, for example, is used for an image carrier
25
as a photoconductive body in the printer section
12
, a photoconductive belt or the like can be used. In a copying operation, the photoconductive drum
25
is driven to rotate by a driving section (not shown), charged uniformly by a charging device
26
, and exposed to laser beams by a laser beam scanner
27
, by which a latent image is formed on the surface of the photoconductive drum
25
. In this operation, the laser beam scanner
27
exposes the photoconductive drum
25
to laser beams from a semiconductor laser (not shown) driven by the foregoing semiconductor driving board in response to the digital image signals from the image processing board
23
, and the photoconductive drum
25
travels in the sub-scanning direction in a position where the latent image is written by the laser beam scanner
27
, by which the latent image of each single line of the image is formed on the photoconductive drum
25
at an equal interval from each other in the sub-scanning direction. The electrostatic latent image on the photoconductive drum
25
is developed by a developing device
28
so as to be a toner image.
A transfer paper is fed to a registration roller
36
as a selected transfer paper from a feeder selected out of feeders
33
to
35
by a selecting device such as an operating section (not shown), or a transfer paper having a size selected by the selecting device or an automatic paper selecting device (not shown) is fed to the registration roller
36
as a selected transfer paper from a feeder out of the feeders
33
to
35
. The transfer paper is sent out by the registration roller
36
at such a timing to register with the toner image on the photoconductive drum
25
.
The toner image on the photoconductive drum
25
is transferred to the transfer paper sent out from the registration roller
36
by a transfer device
30
and the transfer paper is separated from the photoconductive drum
25
by a separating device
31
. The separated transfer paper is then conveyed by a conveying device
37
toward a fixing device
38
. The image on the transfer paper conveyed by the conveying device
37
is fixed by the fixing device
38
and the transfer paper is then ejected onto a tray
39
as a copy. The photoconductive drum
25
is cleaned by a cleaning device
32
to remove residual toner therefrom after the transfer paper is separated from the photoconductive drum
25
.
The laser beam scanner
27
includes, as illustrated in
FIG. 5
, a beam emitting unit
40
including a light source having a semiconductor laser, a collimating lens and an aperture, which are not shown. The semiconductor laser in the beam emitting unit
40
is driven by the foregoing semiconductor driving board in response to digital image signals from the image processing board
23
to emit luminous flux of a laser beam modulated by the digital image signals.
The laser
Brase Sandra L.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
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