Facsimile and static presentation processing – Static presentation processing – Emulation or plural modes
Reexamination Certificate
1997-09-15
2002-01-15
Mancuso, Joseph (Department: 2624)
Facsimile and static presentation processing
Static presentation processing
Emulation or plural modes
C358S001900
Reexamination Certificate
active
06339476
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image generating apparatus for generating an image on recording paper through an electrophotographic or xerographic process.
2. Description of the Related Art
As the processing speed of personal computers and workstations has increased on recent years, it has also been increasing demand to speed up the processing of an image generating apparatus based on a xerographic process. With such an image generating apparatus as mentioned above, when a polygon mirror included in an exposure optical system is increased in its rotational speed, it is possible to speed up its printing operation. In the prior art, however, the increased rotational speed of the polygon mirror has already reached its limit. For this reason, as another additional speeding-up measure, a plurality of semiconductor lasers for forming an electrostatic latent image on a photoconductor drum are provided to realize a simultaneous recording system.
An arrangement and operation of a prior art image generating apparatus having a plurality of semiconductor lasers will be explained in the following.
FIG. 11
is an arrangement of an exposure optical system having a plurality of semiconductor lasers therein in the prior art. The exposure optical system of
FIG. 11
includes first and second semiconductor lasers
21
and
22
, which are positioned so that laser beams emitted from the lasers
21
and
22
are crossed perpendicularly to each other. A collimator lens
23
for making the input light beams parallel is positioned in a beam exit direction of the first semiconductor laser
21
, and a collimator lens
24
is similarly positioned on a beam exit direction of the second semiconductor laser
22
. Disposed on light exit sides of the collimator lenses
23
and
24
is a beam splitter
25
which functions to deflect the laser beam of the first semiconductor laser
21
to a direction perpendicular thereto, transmit the laser beam of the second semiconductor laser
22
therethrough and guide the beams onto a surface of a polygon mirror
26
. The polygon mirror
26
, which is disposed on a rotatary axis of a polygon motor (not shown in the drawing) rotating at a high speed, acts to cause the laser beams received from the first and second semiconductor lasers
21
and
22
to be scanned on a photoconductor drum
1
. Disposed between the polygon mirror
26
and the photoconductor drum
1
are on f lens
27
for reducing the diameter of the laser beams reflected on the polygon mirror
26
to a predetermined value as well as on a reflecting mirror
28
.
With this image generating apparatus, image data corresponding to
2
lines can be recorded at a time in a main scanning direction B of the photoconductor drum
1
from the
2
laser beams received from the first and second semiconductor lasers
21
and
22
.
Further,
FIG. 12
shows a control block diagram of a prior art image generating apparatus having
2
semiconductor lasers.
FIG. 13
is a detailed circuit diagram of a first image data selective output means in the prior art image generating apparatus. In
FIG. 12
, an image data generating means
31
generates image data (bit map data) on the basis of image information received from a host computer (not shown). A memory means
32
stores therein the image data generated by the image data generating means
31
. Further, a first image data selective output means
37
and a second image data selective output means
38
act to extract the image data from the memory means
32
and output it to a first exposure energy control means
35
and a second exposure energy control means
36
, respectively. The first and second exposure energy control means
35
and
36
respectively control exposure energy (light emission time, light emission power) of the first and second semiconductor lasers
21
and
22
incorporated in first and second exposure means
33
and
34
(which will be explained later).
The first and second exposure means
33
and
34
, which include the first and second semiconductor lasers
21
and
22
, respectively, irradiate laser beams on the photoconductor drum
1
to form an electrostatic latent image on the photoconductor drum
1
.
An output control means
39
, on the basis of a printing operation reference signal, controls the operation of the sequential output of the image data stored in the memory means
32
to the first and second image data selective output means
37
and
38
. Further, a clock generating means
40
generates a clock (which will be referred to as the video clock) that is used as a reference to the output operation of the first and second semiconductor lasers
21
and
22
.
Explanation will now be made as to the operation of the image generating apparatus having the above arrangement. In
FIG. 11
, image data is optically modulated by the first and second semiconductor lasers
21
and
22
so that output laser beams of the respective semiconductor lasers are converted by the collimator lenses
23
and
24
to collimated or parallel light and then input to the beam splitter
25
. The beam splitter
25
in turn deflects by
90
degrees the laser beam received from the first semiconductor laser
21
and then guides it to the polygon mirror
26
; whereas the beam splitter
25
transmits the laser beam received from the second semiconductor laser
22
therethrough and then guides it to the polygon mirror
26
. The polygon mirror
26
, while rotated by the polygon motor (not shown), scans the laser beams received from the first and second semiconductor lasers
21
and
22
at a predetermined angle. The laser beams are further input to the f lens
27
where the laser beams are reduced in diameter to a predetermined diametered single beam, and then the single beam is scanned by the reflecting mirror
28
on the photoconductor drum
1
in the direction (main scanning direction) shown by an arrow B. In this case, the photoconductor drum
1
is rotating at a constant speed Vp (mm/sec.) in a direction shown by an arrow A.
FIG. 14
is a diagram for explaining how image data is generated in the prior art image generating apparatus. As shown in
FIG. 14
, picture elements (pixels)
30
each having an illustrated diameter are formed by the laser beam issued from the second semiconductor laser
22
on the first raster scan line, while picture elements (pixels)
29
each having the same diameter as that of the pixel
30
are formed by the laser beam issued from the first semiconductor laser
21
on the second raster scan line. The above operation is sequentially repeated in a direction shown by an arrow C so that the laser beam issued from the second semiconductor laser
22
forms pixels of the odd-numbered raster scan lines, whereas the laser beam issued from the first semiconductor laser
21
forms pixels of the even-numbered raster scan lines. As a result, printing can be realized at a speed of twice as fast as the case of using a single semiconductor laser.
Explanation will next be made as to specific control operation when image data having a main scan (horizontal scanning) resolution of 600 dpi and a feed scan (vertical scanning) or sub-scan resolution of 600 dpi is output to the photoconductor drum
1
.
FIG. 15
is a timing chart of the first image data selective output means of the prior art image generating apparatus, and
FIG. 16
is a diagram showing a relationship between pixel formation and laser emission time in the prior art image generating apparatus.
In
FIG. 12
, the image data generating means
31
, on the basis of image information received from the host computer (not shown), generates image data (bit map data) and stores it in the memory means
32
. On the basis of a printing operation reference signal (not shown), the output control means
39
controls the memory means
32
to cause the memory means
32
to output the first and second raster scan lines of the image data therefrom to the second and first image data selective output means
38
and
37
respectively. That is, as shown in
FIG. 13
, a se
Hayashi Yoshitsugu
Kajiwara Tadayuki
Nakamura Kazunori
Mancuso Joseph
Matsushita Electric - Industrial Co., Ltd.
Stevens Davis Miller & Mosher LLP
Tran Douglas
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