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Claims  |
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What is claimed is:
1. A copying machine comprising:
an original-carrying table for supporting thereon an original;
a photosensitive material rotatably mounted in the copying machine;
an original scanning means movable relative to the original-carrying table
for scanning the original thereon to obtain an original image;
a means for projecting the original image on the photosensitive material to
form an electrostatic latent image;
a control means for driving the original scanning means a plurality of
times to form plural electrostatic latent images on the photosensitive
material;
a means for successively developing the plural electrostatic latent images
on the photosensitive material with a toner to form plural toner images;
and
a means for transferring the plural toner images successively formed on the
photosensitive material onto a recording medium.
2. The copying machine as claimed in claim 1, wherein the original scanning
means includes a scanner movable forwardly and backwardly along the
original-carrying table.
3. The copying machine as claimed in claim 2, wherein the projection means
includes means for varying a copying magnification, and the control means
being capable of shifting a start position of the scanner depending upon
the copying magnification of the projecting means.
4. A copying machine comprising:
an original-carrying table for supporting thereon an original;
a photosensitive material rotatably mounted in the copying machine;
a scanner movable reciprocatingly relative to the original-carrying table
so as to scan the original thereon to obtain an original image;
a means for projecting the original image on the photosensitive material to
form an electrostatic latent image;
a means for developing the electrostatic latent image on the photosensitive
material with a toner to form a toner image;
a means for transferring the toner image to a recording paper;
a means for transporting the recording paper on which the toner image has
been transferred to the transferring means again; and
a means for controlling operation timing of the scanner such that the
original is scanned a plurality of times during a first copying cycle to
form a first plurality of toner images with a spacing L defined
therebetween whose spacing corresponds to a distance from a tip portion to
an end portion of the image, and the original is next scanned a plurality
of times during a second copying cycle to be repeated subsequent to the
first cycle to form a second plurality of toner images each of which is
shifted by the spacing L in a primary scanning direction of the original
relative to each of the toner images formed during the first copying
cycle.
5. The copying machine as claimed in clam 4, wherein the transferring means
includes a transfer charger for transferring the first and second
plurality of toner images to the recording paper and a transfer charger
control means for actuating the transfer charger only when the toner
images formed on the photosensitive material are disposed in an opposing
relationship to the transfer charger.
6. A process for copying an original image which is placed on an
original-carrying table, said process being adapted to scan the original
by means of a scanner which is movable forwardly and backwardly along the
original-carrying table so as to expose the image onto a photosensitive
material, comprising the steps of:
scanning the original on the original-carrying table at least twice during
a first copying cycle to form, on the photosensitive material, at least
two electrostatic latent images with a spacing therebetween;
developing the electrostatic latent images on the photosensitive material
with toners to form toner images;
transferring, as a first transfer step, the toner images to a sheet of
recording paper;
scanning the original placed on the original-carrying table at least once
by the scanner during a second copying cycle to form, on the
photosensitive material, an electrostatic latent image;
developing the electrostatic latent image formed on the photosensitive
material with toner to form a toner image; and
further transferring, as a second transfer step, the toner image on an area
of the recording paper, said area corresponding to the spacing formed
between the first-mentioned toner images.
7. A process for copying an original image which is placed on an
original-carrying table, said process being adapted to scan the original
by making use of a scanner which is movable reciprocatingly along the
original-carrying table for exposing the image onto a photosensitive
material, comprising the steps of:
scanning the original placed on the original-carrying table by means of the
scanner during a first copying cycle so as to form an electrostatic latent
image on a photosensitive material;
developing the electrostatic latent image formed on the photosensitive
material with a toner to form a toner image;
transferring, as a first transfer step, the toner image on a sheet of
recording paper;
scanning at least twice the original image placed on the original-carrying
table by means of the scanner during a second copying cycle so as to form
electrostatic latent images on the photosensitive material with a space
therebetween, said space being equal to or larger than the electrostatic
latent image formed in the first copying cycle;
developing at least two electrostatic latent images formed on the
photosensitive material with a toner to form toner images; and
further transferring, as a second transfer step, the toner images on areas
of the recording paper different from an area on which the first-mentioned
toner image has been transferred during the first transfer step.
8. A copying machine for producing a plurality of same images on a single
copying paper, said copying machine comprising:
first copying mode for scanning an original at least twice to form at least
two images, each of said image being spaced apart by a distance of at
least L where the distance L equal to a length of the each image from a
leading end to a trailing end; and
second copying mode for scanning the original to form an image having a
length corresponding to said distance L and occupying an area defined by
the distance L.
9. A copying machine for producing a plurality of same images on a single
copying paper, said copying machine comprising:
first copying mode for scanning an original to form an image having a
length L in a scanning direction; and
second copying mode for scanning the original at least twice to form at
least two images, each of said images being spaced apart by a distance of
at least L in the scanning direction so as to sandwich the image formed by
the first copying mode.
10. The process as claimed in claim 6, wherein said spacing produced
between the electrostatic latent images formed in a first copying cycle is
equal to or larger than a distance from tip portion to end portion of the
electrostatic latent image formed in a second copying cycle.
11. A copying machine comprising:
an original-carrying table for supporting thereon an original;
a photosensitive material rotatably mounted in the copying machine;
a scanner movable reciprocatingly relative to the original-carrying table
so as to scan the original thereon to obtain an original image;
a means for projecting the original image on the photosensitive material to
form an electrostatic latent image;
a means for developing the electrostatic latent image on the photosensitive
material with a toner to form a toner image;
a means for transferring the toner image to a recording paper;
a means for transporting the recording paper on which the toner image has
been transferred to the transferring means again; and
a means for controlling the scanner to execute a first plural scanning
operation and a second plural scanning operation in each of which the
original is scanned a plurality of times for forming a plurality of toner
images with a space therebetween, said space being equal to or larger than
a size of the toner images produced in the first and second plural
scanning operations, and said second scanning operation being executed
such that each toner image formed in the second plural scanning operation
is positioned between the toner images formed in the first plural scanning
operation.
12. The copying machine as claimed in claim 11, wherein said transferring
means includes a transfer charger for transferring the toner images
produced by the first and second plural scanning operations onto the
recording paper and an inhibiting means for inhibiting operation of the
transfer charger when said toner images are not opposite to the transfer
charger. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1) Field of the Invention
This invention relates to a copying machine of an electrophotographic type,
which is capable of copying a single original in the plural form in
succession on a copying paper having a size larger than that of the
original and a copying process thereof.
2) Description of the Related Art
Copying machines have been known, which can pulurally copy a single
original in succession on a copying paper having a size larger than that
of the single original. Such copying machines are actuated such that the
original is wound on a drum and its drum is then rotated, to project the
original image on a photosensitive drum in succession as shown in Japanese
Laid Open Patent Publication 63-14177. It is therefore necessary to
provide a specific mechanism. In the conventional-type copying machine,
i.e., the copying machine having a fixed original table and a scanning
optical system which is capable of moving forward and backward alternately
or in the copying machine provided with a reciprocating original table and
a fixed optical system, the image processing cannot be performed during
the return of the scanning optical system or during the return of the
movable original table. It is therefore impossible to form reproduced
images in the plural form in succession on a sheet of copying paper.
Assuming that an image memory having storage capacity corresponding to one
page of the original is provided in a digital-type copying machine, the
copying machine can provide that the contents stored in the image memory
are read repeatedly plural times successively so as to form consecutive
image signals, so that the consecutive plural images are formed. However,
the above-described construction needs an image memory having a large
storage capacity, so that such a machine becomes extremely high price,
thereby making it impossible to provide a practical copying machine.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a novel copying machine in
which the above-described drawbacks of the prior art have successfully
been solved.
It is another object of this invention to provide a copying machine which
is capable of forming plural reproduced images in succession from a single
original on the same copying paper by adjusting the scanning timing and
then scanning the original plural times during one image forming step.
The other object of the invention is to provide a copying process capable
of forming plural reproduced images in succession from a single original.
The other objects of the present invention will become apparent from the
following description and appended claims, taken in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view showing a structure of a digital-type
color copying machine in which the present invention is rendered suitable
for practice;
FIG. 2 is a block diagram of a controller circuit for the copying machine;
FIG. 3 is a diagram for describing the scanning speed of a scanner;
FIG. 4 is a timing chart for describing a process for copying a single
original in the plural form on a sheet of copying paper;
FIG. 5 is an illustrative example of a print obtained by copying a single
original in the plural form on a sheet of copying paper;
FIG. 6(a) is a diagram showing the time and scanning speed of a scanner
whose speed is associated with the copy magnification; and
FIG. 6(b) is a schematic view illustrating positional variations in the
home position of the scanner whose position is associated with the copy
magnification.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The embodiments of this invention will hereinafter be described with
reference to the accompanying drawings. FIG. 1 is a cross-sectional view
showing an overall construction of a digital-type color copying machine in
which the present invention is rendered suitable for practice. In such a
digital-type color copying machine, an original is first read by an image
sensor and the thus-read image signal causes a laser beam to be modulated,
to thereby form a pictorial latent image on a photosensitive drum. In
addition, the latent image formed on the drum is developed with a toner to
form a color image on a copying paper.
Referring to FIG. 1, designated at numeral 10 is a scanner, which is
equipped with an exposure lamp 12 for irradiating an original, a rod-like
lens array 13 which serves to collect the reflected light from the
original and then introduce the same into an image sensor 14, and a color
image sensor 14 to be described subsequently operative for converting the
reflected light from the original into electric signals having three
primary colors of red (R), green (G) and blue (B) with a picture area
corresponding to one line relative to the primary scanning direction of
the original.
The scanner 10 is actuated by a motor 11 and then transferred along the
lower part of a copying table 16 in the direction indicated by arrow f. As
a consequence, the original on the original table 16 is scanned along its
primary scanning direction by the image sensor 14 and also scanned along
the sub scanning direction perpendicular to its direction as the scanner
10 moves, whereby the original image is converted into an image signal by
the color image sensor 14.
Designated at numeral 20 is an image signal processing unit and numeral 31
indicates a printing head. Incorporated in the printing head 31 are a
semiconductor laser driver circuit 33, a semiconductor laser oscillator 34
and an unillustrated polygon mirror device. The image signal outputted
from the color image sensor 14 is processed by the image signal processing
unit 20 and thereafter inputted to the semiconductor laser driver circuit
33. A laser beam emitted from the semiconductor laser oscillator 34 is
caused to be modulated by the image signal and the thus-modulated signal
is scanned by the unillustrated polygon mirror along the primary scanning
direction, followed by reflection of a mirror 37, to thereby form a latent
image relative to the original image on a photosensitive drum 41 to be
described subsequently.
Numeral 41 is the photosensitive drum around which an eraser lamp 42, a
main charger 43, an interimage eraser 44 and developing devices 45a to 45d
are arranged in that order. Each of these developing devices 45a to 45d is
used to develop a latent image with a color toner. The developing devices
45a, 45b, 45c and 45d have been supplied with toners of yellow (Y),
magenta (M), cyan (C) and black (B) colors, respectively.
Designated at numeral 51 is a transfer drum. The transfer drum 51 is
disposed in an opposing relationship to the photosensitive drum 41 and
provided therein with a transfer charger 46. Provided at a part of the
transfer drum 51 is a chucking mechanism 52 for winding a copying paper to
be supplied from a paper feeding tray 50 on the transfer drum 51. In
addition, deelectrifying chargers 53, 54, a cleaner 55 operably provided
with a space in an opposing relationship to the transfer drum 51 and a
position sensor 56 for sensing rotational angular positions of the
transfer drum 51. The position sensor 56 is a reflection-type photosensor
and senses any one of marks applied inside the transfer drum 51 so as to
output a signal.
The signal outputted from the position sensor 56 is inputted to a control
CPU 25 in a controller circuit and is also used to control an operation
timing for image formation such as the scan start time of the scanner 10.
Numeral 47 indicates a scraper for scraping copying papers wound on the
transfer drum 51, 48 indicates a paper fixing device and 49 is a paper
discharge tray.
FIG. 2 is a block diagram of a controller circuit which is employed in a
copying machine. In the drawing, designated at numeral 25 is a control CPU
which controls the operation of the copying machine. Inputted to an input
port of the control CPU 25 are signals from various key switches on a
control panel, a sense signal TBASE from the position sensor 56 and other
signals. To the contrary, a signal for ON/OFF controlling the transfer
charger 46, a signal for controlling the motor 11 used to drive the
scanner and a signal for controlling other devices are outputted from an
output port.
Designated at numeral 20 is an image signal processing unit which operates
under control of the CPU 25.
The image signal processing unit 20 is composed of a logarithmic amplifier
21, an A/D converter 22, a shading correction circuit 23, a masking
processing circuit 24, an electrically
magnification-varying/image-position moving circuit 26, a half-tone
processing circuit 27 and an I/F circuit 28.
The logarithmic amplifier 21 is used to amplify the image signals of the
three primary colors composed of the red (R), green (G) and blue (B),
which have been photoelectrically-converted by the color image sensor 14,
into signals having the intensity associated with the image density.
The A/D converter 22 serves to convert an output signal from the
logarithmic amplifier 21 into a digital signal. An image signal having the
gradation is outputted from the A/D converter 22.
The shading correction circuit 23 operates to perform a shading correction
of the image signal.
The masking processing circuit 24 outputs a image signal corresponding to
one of the yellow (Y), magenta (M), cyan (C) and black (B) colors
associated with the color to be printed, from among the image signals of
the three primary colors composed of R, G and B in accordance with color
characteristics of toners which have been fed to the developing devices
45a to 45d.
The electrically magnification-varying/image position moving circuit 26
operates to perform a processing of the change in a copying magnification
in the primary scanning direction of the original and a processing for
moving the image position relative to the primary scanning direction. This
can be achieved by adjusting the reading timing of the image signals which
have temporarily been stored in a memory. In addition, it is also possible
to output two images side by side by shifting the position of the image
along the primary scanning direction or repeatedly reading image signals
from the memory.
The half-tone processing circuit 27 performs the binary-coded processing of
printing signals from the masking processing circuit 24 by, for example,
the dither method, to thereby produce binary false halftone signals.
The I/F circuit 28 is a line memory circuit for storing image signals
corresponding to one line traced along the primary scanning direction of
the original. This memory circuit has a storage capacity corresponding to
two lines so that the read/write operations can be executed in parallel
with each other.
A description will next be made of the operation for forming color images
in the digital-type color copying machine of the above-described
construction.
It is necessary to separate the original image into four images having four
colors composed of the three primary colors of the Red (R), Green (G) and
Blue (B) and the black color and hence to develop or create the same using
a toner of a predetermined color in order to form a color image. For that
purpose, the scanning for separating the original image into the images
having these colors is performed four times herein. The scanning for the
color separation and the operation for selecting one of the developing
devices associated with the colors are executed by the control CPU 25.
The digital-type color copying machine according to the present embodiment
is constructed such that the photosensitive drum 41 and the transfer drum
51 are caused to be rotated at a given speed and the starting of the scan
operation of the scanner 10 is controlled in unison with the operation of
the transfer drum 51, whereby the transfer drum 51 and the scanner 10 are
synchronized with each other. The number of rotations of the transfer drum
51 is detected by the position sensor 56 provided in the transfer drum 51.
The detected signal TBASE is inputted to the CPU 25. After a predetermined
time has elapsed from the negative edge of the signal TBASE, the CPU 25
serves to control the motor 11 and hence to drive the scanner 10 in such a
way that a tip portion of the original is read.
FIG. 3 is a diagram for describing the scanning speed of the scanner 10.
The scanner 10 makes a start in its movement from the home position at a
time to and its movement is accelerated upwardly. The scanner 10 then
reaches a predetermined scanning speed at a time t.sub.1, and its scanning
is thereafter executed at a given speed. Its scanning is brought to
completion at a time t.sub.2 and at the same time, deaccelerated
downwardly, followed by stoppage of its scanning of the scanner 10 at a
time t.sub.3. In order to return the scanner 10 to its home position, the
scanner 10 makes a start in its movement in the direction opposite to the
scanning direction at a time t.sub.4 and its moving speed is accelerated
and the scanner 10 travels at a given speed from a time t.sub.5.
Thereafter, its moving speed is reduced at a time t.sub.6 and the scanner
10 then reaches the home position at a time t.sub.7, thereby resulting in
stoppage of the scanner 10. Where the return step at the negative side is
compared with the scanning step at the positive side, the scanner 10
during the return step can move at a higher speed than that during the
scanning step as shown in FIG. 3.
The image signals composed of the three primary colors of the R, G and B
whose signals have been photoelectrically-converted by the color image
sensor 14 provided in the scanner 10 are processed by the image signal
processing unit 20. At this time, the control CPU 25 controls the masking
circuit 24. In addition, the control CPU 25 outputs an image signal of a
yellow color (Y) upon the first scanning of the scanner and controls such
that the developing device 45a which has been supplied with a yellow toner
associated with the image signal of the yellow color is rendered in an
operated state. Accordingly, the image signal of the yellow (Y) color
outputted from the image signal processing unit 20 causes a laser beam
emitted from the semiconductor laser oscillator 34 to be modulated, to
thereby form an electrostatic latent image on the photosensitive drum.
Thereafter, the electrostatic latent image is developed by the developing
device 45a which has been rendered in the state to be operated by the
signal outputted from the control CPU 25 and has been supplied with the
yellow toner.
On the other hand, a copying paper fed from the paper feeding tray 50 has
been wound on the transfer drum 51, so that the toner image of the yellow
(Y) color formed on the photosensitive drum 51 is transferred thereto.
An image of the magenta (M) color obtained after completion of processing
of the second scanning, development and transfer is superimposed on the
toner image of the yellow (Y) color formed on the copying paper, which has
been wound previously on the transfer drum, to thereby be transferred
thereto. Likewise, an image of the cyan (C) color upon the third scanning
and an image of the black (B) color upon the fourth scanning are
superimposed successively on the toner image formed on the copying paper,
whereby the transfer of these images is performed.
When the toner images composed of different four colors are superimposed on
the copying paper so as to form a complete image, the copying paper is
scraped from the transfer drum 51 by the scraper 47 and then fixed by the
paper fixing device 48. After that copying paper is discharged on the
paper discharge tray 49.
A description will next be made of the processing of copying a single
original on a sheet of copying paper in the plural form with reference to
a timing chart shown in FIG. 4.
When the portion of the negative edge of the signal TBASE outputted from
the position sensor 56 is brought about upon the first rotation of the
transfer drum 51, the scanner 10 set in the home position makes a start in
the operation of the first scanning and returns to the home position with
completion of its scanning operation. The first latent image a associated
with the original is formed on the photosensitive drum 41 by the first
scanning.
The scanner 10 further starts its second scanning operation and the second
latent image b associated with the original image is formed on the
photosensitive drum 41 after completion of its scanning. Needless to say,
a time at which the scanner 10 starts its second scanning operation occurs
in a point delayed from a time at which it makes start in the operation of
the first scanning. Where the equimultiple copying is performed, the
last-mentioned scanning start time is delayed by the time interval
required for the rotation of the transfer drum 51 or longer whose interval
corresponds to twice (2L) the length L which extends in the sub scanning
direction of the original over the outer peripheral face of the transfer
drum 51 after the signal TBASE has been outputted. When the scanning start
time is taken as 2L, the images can plurally be formed in succession.
The first and second latent images a,b formed on the photosensitive drum 41
are developed by the developing device 45a which have been supplied with
the toner of the yellow color to form toner images, and the resultant
toner images A and B are transferred to the copying paper wound on the
transfer drum 51.
When a signal TBASE is outputted from the position sensor 56 subsequent to
a start in the second rotation of the transfer drum 51, the scanner 10
makes a start in the operation of the third scanning after a predetermined
period of time has elapsed from the trailing edge of the signal TBASE, and
the third latent image c associated with the original is hence formed on
the photosensitive drum 41. Here, the term "the elapsed predetermined
time" referred to above corresponds to a period which has elapsed by a
time required for the rotation of the transfer drum 51 whose period is
equivalent to the length L which extends in the sub scanning direction of
the original over the outer peripheral face of the transfer drum 51 after
the signal TBASE has been outputted.
Furthermore, the scanner 10 makes a start in the operation of the fourth
scanning. Similarly to the above, the fourth latent image d associated
with the original image is formed on the photosensitive drum 41. Where the
equimultiple copying is performed, the fourth scanning start time is
delayed by a time interval required for the rotation of the transfer drum
51 whose interval corresponds to three times (3L) the length L which
extends in the sub scanning direction of the original over the outer
peripheral wall of the transfer drum 51 after the signal TBASE has been
outputted.
The third and fourth latent images c and d which have been formed on the
photosensitive drum 41 in the above-described manner are developed by the
developing device 45a which has been supplied with the toner of the yellow
color to form toner images, and the resultant toner images C an D are
transferred to the copying paper wound on the transfer drum 51.
As a consequence, said images A, C, B and D which have assumed the yellow a
the first developing color are formed in that order on the same copying
paper in succession.
In addition, where the magenta as the second developing color, the cyan as
the third developing color and the black as the fourth developing color
are used, exactly the same processing a described above is performed.
Consequently, said images A, B, C and D can be produced in full color on
the copying paper.
In this case, the transfer of the toner images to the copying paper has
been performed in order of A, B, C and D. However, the transfer of the
toner images may first be carried out in order of C and D, followed by A
and B.
Further, if one desires to produce three same images in succession in the
direction of the sub scanning, the front and rear images from among the
three images may be produced upon the first rotation of the transfer drum
51 and the remainder, i.e., the central image may be produced upon the
second rotation of the transfer drum 51. Otherwise, the central image may
first be produced upon the first rotation thereof, followed by production
of the remainder upon the second rotation thereof.
Incidentally, omitted for convenience' sake, from the above description is
a description about a delay corresponding to a rise time required from the
time that the signal TBASE is outputted until the time that the scanner
actually makes a start in the scanning operation, and a delay
corresponding to a slight time required from the time that the latent
image is formed on the photosensitive drum until the time that the toner
image is transferred to the copying paper on the transfer drum.
When the above-described copying process is used, the number of times the
toner image is to be transferred to the copying paper is increased. As a
consequence, the residual electric charges on the copying paper are
increased, so that the toner image is not transferred efficiently. A
potential problem therefore arises that satisfactory copied or reproduced
images cannot be obtained.
As shown in FIG. 4, the ON/OFF operation timing of the transfer charger is
controlled in the present invention. In other words, when the transfer
time of the toner image takes place subsequent to the output of the signal
TBASE, the transfer charger is brought to an ON state over the overall
area of the copying paper during the initial copying step, i.e., during
the first rotation of the transfer drum 51. The copying paper is then held
on the transfer drum 51 by electric charges and the toner image on the
photosensitive drum 41 is transferred to the copying paper. Subsequent to
the second rotation of the transfer drum 51, the period during which the
transfer charger is held an ON state is controlled only when the toner
image on the photosensitive drum 41 is put in the transfer position. Such
control is executed by the control CPU 25.
Owing to the control of the ON/OFF operation timing of the transfer charger
as described above, the transfer charger is brought to the ON state only
over the area where the toner image is transferred to the copying paper.
Therefore, the residual charges on the copying paper is not increased at
random eve when the toner image is transferred plural times to the copying
paper, thereby making it possible to form a satisfactory image.
In the above-described processing in which the plurality of reproduced
images can be formed on a sheet of copying paper from the single original,
the original is read by the image sensor and the thus-read image is stored
as an image signal in the memory. Therefore, the electrically
magnification-varying/image-position moving circuit 26 can control the
timing at the output of its signal and also perform the processing for
outputting the same signal plural times (e.g., two times). As shown in
FIG. 5, such a processing permits arrangement in parallel of images copied
in the plural form from the single original in the transverse direction
(in the direction indicated by arrow X) of the copying paper and the
consecutive formation of the images copied plurally from the single
original in the direction of the length (in the direction indicated by
arrow Y) of the copying paper. An example shown in FIG. 5 shows that the
eight reproduced images in amount which consist of 2 rows.times.4 columns
can be formed on a copying paper of size A.sub.3 where the original of
size A.sub.6 is used.
A description will next be made of change in copying magnification. In the
present embodiment, the change in copy magnification in the primary
scanning direction of the original image is performed by the electrically
magnification-varying/image-position moving circuit 26 in the image signal
processing unit 20 when one desires to change the copying magnification.
In other words, when one desires to enlarge the image, the image signals
corresponding to one line traced along the primary scanning direction
whose signals have been stored in the memory may be enlarged by inserting
an interpolation signal midway between signals associated with respective
picture elements in accordance with its expansion magnification, while
where one wants to reduce the size of image, the image signals may be
reduced by removing a part from signals associated with respective picture
elements.
The change in the copying magnification in the sub scanning direction is
performed by changing the scanning speed of the scanner 10 in accordance
with the copying magnification. In this case, the scanning start times up
to the time that the scanner 10 reaches a predetermined scanning speed
depending upon the copying magnification are different from one another
depending on the copying magnification. This will therefore cause a change
in the home position of the scanner 10 in accordance with the copying
magnification.
FIGS. 6(a) and 6(b) are diagrams for describing change in the copying
magnification. In FIG. 6(a), the axis of abscissas assumes time variations
from the scanning start time of the scanner, while the axis of ordinates
assumes the scanning speed of the scanner. Referring to FIG. 6(a), when
the equimultiple copying is performed, the scanner reaches a predetermined
scanning speed Ap at a time tp, while when the twofold copying
magnification is used, the scanner reaches a predetermined scanning speed
Aq at a time tq. In addition, the scanner reaches a predetermined scanning
speed Ar at a time tr upon use of the copying magnification by 0.5 times.
Accordingly, the home position of the scanner is set at a location spaced
from the tip portion of the image by a distance required for the scanner
10 to travel during the time until the time that the scanner reaches the
predetermined scanning speed depending upon the copying magnification.
FIG. 6(b) is a schematic view for describing the home position of the
scanner depending upon the copying magnification. When the equimultiple
copying is taken, the position H.sub.1 shows the home position of the
scanner, while the home position H.sub.2 is brought to a location adjacent
the tip portion of the image compared with the home position H.sub.1 when
the twofold copying magnification is chosen. When the copying
magnification is taken as 0.5 times, the home position H.sub.0.5 is
brought to a location away from its tip portion compared with the home
position H.sub.1.
In the above-described embodiment, after completion of the transfer of the
initial toner image to the copying paper which has been wound on the
transfer drum, the following toner image is transferred to the copying
paper without fixing the previous toner image after the paper to which the
initial toner image has been transferred has been fed again to the
transfer portion. In this manner, the toner images are superimposed on one
another successively and the thus-superimposed images are fixed as final.
As an alternative, its fixing may be carried out for each transfer of the
toner image, and the following toner image may thereafter be transferred
and then fixed thereon.
In addition, the copying machine according to the present embodiment is of
the type that the original table is fixed and the scanning optical system
is moved reciprocatingly during its operation. However, such machine may
be used as a type that the original table is movable forwardly and
backwardly so as to perform the necessary scanning.
The present invention can be applied even to an analog-type copying
machine. The present invention is not necessarily limited to the
digital-type copying machine which has been described in the
aforementioned embodiment.
According to the present invention, the toner image formed during a first
copying cycle is different in position to be transferred to the copying
paper from each toner image formed during each copying cycle subsequent to
the above cycle operation, whereby the reproduced images can be formed
consecutively without superimposing the same on o | | |
