Multiple image forming system

A multiple image forming system for synthesizing images having different kinds of gradation characteristics of an original comprises: a latent image forming circuit for projecting a reflected light from the original onto a photo sensitive drum and forming an electrostatic latent image onto this drum; a developing unit to develop the latent image; and a control circuit to make the latent image forming circuit and the developing unit operative every gradation characteristic for the different gradation characteristic areas in the original, wherein the control circuit changes the latent image forming conditions such as an amount of exposing light to the original of the latent image forming circuit and the developing conditions such as a developing bias of the developing unit in accordance with the kind of gradation characteristic. With this system, the image areas having different kinds of gradation characteristics which mixedly exist in one original are automatically detected and the latent image forming circuit is automatically properly controlled, so that the proper image is reproduced.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a multiple image forming system for 
synthesizing and forming a plurality of images having different 
characteristics. 
2. Related Background Art 
Hitherto, in the case where the portions having different gradations, for 
example, the character portion and the photograph portion or low contrast 
portion mixedly exist on the same original, a density reducing dial or 
photograph mode selection key or the like is operated in accordance with 
the portion whose occupying rate is larger or with the portion to be 
emphasized and the images are then copied. However, according to such a 
method, the image in the other portion is frequently certainly sacrificed. 
For example, when the images were copied in accordance with the character 
portion, the gradations in the photograph portion become poor, so that the 
images in the photograph portion become hard. On the contrary, when the 
images were copied in accordance with the photograph portion, the density 
of the images in the character portion is reduced or the images in the 
character portion easily become fogging. 
For example, when copying an original in which cut-out photograph originals 
and newspaper originals mixedly exist in one original proper image forming 
means does not exist for all of the originals such as photograph original 
which needs gradations and newspaper original which requires that the 
fogging does not occur. Therefore, in most cases, the user usually selects 
image forming means such that a reference original can be properly copied. 
Thus, even if a proper image was derived for a reference original as a 
base, the image of a cut-out photograph original has the poor gradations. 
On the other hand, in the case of a newspaper original, an image such that 
the background portion is fogging is obtained. It is difficult to obtain 
an image suitable for all of the mixed originals. 
The applicant of this invention has proposed a multiple copying system in 
which areas of an original are designated and each area is reproduced in 
different color in U.S. patent application Ser. No. 830,745 (Feb. 19, 
1986). 
The applicant of this invention has also proposed various kinds of systems 
in which an image of an original is read as a form of an electric signal 
and a different process is performed every area having different gradation 
characteristic in U.S. Pat. No. 4,414,581, U.S. patent applications Ser. 
No. 640,539 (Aug. 14, 1984), Ser. No. 580,821 (Feb. 16, 1984), Ser. No. 
022,513 (Mar. 9, 1987), Ser. No. 058,625 (Jun. 4, 1987), Ser. No. 644,558 
(Aug. 27, 1984), Ser. No. 650,267 (Sep. 13, 1984), Ser. No. 022,606 (Mar. 
5, 1987), etc. 
However, in a copying apparatus of the type in which the light of an image 
is directly irradiated onto a photo sensitive material, a system for 
executing the process every area having a different gradation 
characteristic does not exist yet. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a multiple image 
forming system which can eliminate the foregoing drawbacks in the 
conventional techniques. 
Another object of the invention is to provide a multiple image forming 
system for forming a multiple image by changing the gradations of 
respective images in a plurality of areas of an original. 
Still another object of the invention is to provide a multiple image 
forming system in which even if the original portions having different 
kinds of gradation characteristics mixedly exist in one original, the 
original areas having the different kinds of characteristics are 
automatically detected and proper image forming means is automatically 
controlled for each original, thereby enabling a proper image to be 
reproduced. 
The above an other objects and features of the present invention will 
become apparent from the following detailed description and the appended 
claims with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A method of changing the gradation will be first described. 
It is well known that the degree of fidelity in the reproduction when an 
original was copied can be expressed as a sensitometry. FIG. 9 shows such 
a sensitometry. The reflecting density (D.sub.c) of the copy to the 
reflecting density (D.sub.o) of an original is shown in the first quadrant 
in FIG. 9. This curve can be obtained by the following three 
characteristics: namely, the relation between the original reflecting 
density (D.sub.o) and the amount (E) of exposing light which is irradiated 
onto the surface of a photo sensitive material (this relation is shown in 
the fourth quadrant); the relation between the amount (E) of exposing 
light and the potential (V) on the surface of the photo sensitive material 
(this relation is shown in the third quadrant); and the relation between 
the potential (V) and the copy reflecting density (D.sub.c) (this relation 
is shown in the second quadrant). Therefore, by changing the 
characteristic curve of D.sub.o -D.sub.c in the first quadrant, the 
gradation changes. This means that a desired D.sub.o -D.sub.c curve can be 
obtained by changing one of or a combination of the characteristic curves 
in the respective quadrants. 
For example, the case where the development characteristic (V - D.sub.c) in 
the second quadrant was changed is shown. In general, the characteristic 
as shown by a solid line is obtained in each quadrant. However, in the 
first quadrant, this characteristic corresponds to the case where .gamma. 
is large, and it is suitable to reproduce a line. However, if an image was 
photographed under this condition, the copy image becomes hard and the 
details of the photograph are not reproduced. As a reproducibility of the 
gradation, it is ideal that the characteristic curve in the first quadrant 
has a gradient of 45.degree.. However, as compared with the ideal curve, 
in the case of the curve shown by a solid line, .gamma. is large, 
particularly, in the low density portion and the low density portion of 
the photograph cannot be reproduced with a high fidelity. 
Therefore, the development characteristic (V - D.sub.c) expressed in the 
second quadrant is changed. In this case, a system which is known as a 
jumping development disclosed in U.S. Pat. Nos. 4,292,387, 4,395,476, etc. 
was used as a developing system. According to this developing system, the 
alternate current component AC which is derived by adding the direct 
current component DC to the development bias is used. The bias conditions 
in the case of the characteristic curve shown by the solid line are as 
follows. The peak to peak voltage of the AC was 1200V.sub.pp, the 
frequency was 1500 Hz, and the DC component was 200V. When the AC 
component was set to 1000V.sub.pp and 800 Hz, the V - D.sub.c 
characteristic shown by a broken line was derived. At this time, the 
D.sub.o -D.sub.c characteristic becomes as shown by the broken line. It 
will be understood that the Y characteristic was improved. Further, when 
the DC component of the bias was changed from 200V to 100V, the V - 
D.sub.c characteristic changes as indicated by an arrow (.fwdarw.), 
namely, becomes the characteristic as indicated by an alternate long and 
short dash line. The D.sub.o -D.sub.c characteristic corresponding to that 
characteristic also becomes as shown by an alternate long and short dash 
line in the first quadrant. It will be understood that this characteristic 
curve approached the ideal straight line of 45.degree.. In the actual 
image, it has been confirmed that the reproducibility of the middle 
density was fairly improved. Namely, .gamma. of the D.sub.o -D.sub.c 
characteristic can be reduced by reducing the frequency of the AC 
component, reducing the peak to peak voltage V.sub.pp of the AC component, 
or reducing the voltage of the DC component. 
The case where the development characteristic was changed has been shown in 
this example. Similarly, the latent image characteristic (E - V) shown in 
the third quadrant or the exposure characteristic (E - D.sub.o) shown in 
the fourth quadrant can be also changed. 
On the other hand, the gradation reproducibility can be further improved by 
a combination of the changes in those development, latent image, and 
exposure characteristics. 
To further improve the development characteristic, not only the developing 
unit but also the characteristic of the toner can be also changed. For 
example, if a toner of particles which are finer than those in the 
ordinary toner is used to improve the reproducibility of a photograph, a 
fine image suitable for a photograph can be obtained. 
The developing conditions of a single developing unit can be changed. A 
plurality of developing unit having different development characteristics 
can be used. Or, a combination of these methods can be also used. 
As a method of changing the latent image characteristic, a method whereby a 
charging amount to the photo sensitive material (corresponding to the 
potential V on the surface of the photo sensitive material) in the E - V 
characteristic is changed is effective. 
For example, as shown in the third quadrant in FIG. 9, .gamma. of the E - V 
characteristic decreases by changing the E - V characteristic (V=650V) 
indicated by a solid line to that shown by an alternate long and two short 
dashes line (V=340V), namely, by reducing the charging amount to the dark 
portion of the original from 650V to 340V. Thus, .gamma. of the D.sub.o 
-D.sub.c characteristic (indicated by an alternate long and two short 
dashes line in the first quadrant) also decreases and the image having a 
good gradation can be obtained. To reduce the surface potential V, it is 
sufficient to reduce the charging voltage of a charging device 2. 
As another method of changing the latent image characteristic, .gamma. of 
the E - V characteristic in the fourth quadrant in FIG. 9 is changed. 
In the case of the E - V characteristic shown by the solid line in FIG. 9, 
the value of .gamma. is small in the portion where the amount of exposing 
light is relatively small, while .gamma. is large in the portion where the 
amount of exposing light is large. Accordingly, if the operator desires to 
emphasize the gradation than the present gradation, it is sufficient to 
reduce the amount of exposing light of an exposing lamp (not shown). 
However, in this case, since the amount of light is small, the blank 
portion of the image sometimes becomes fogging. However, by changing the 
developing bias (the DC component in the case of the jumping development) 
as necessary, the density can be adjusted to a proper value. In the 
following first embodiment, a system using two developing units having 
different .gamma. characteristics will be described. 
FIG. 1 is a cross sectional view showing the first embodiment of the 
invention. 
In the diagram, reference numeral 1 denotes a photo sensitive drum. After 
the drum 1 was uniformly charged by the charging device 2, an 
electrostatic latent image is formed on the drum surface in accordance 
with a light image 3 from an original. An LED array 4 is ordinarily used 
to erase the charges in the non-image portion (where no image is formed). 
The LED array 4 is also used to erase the charges in an arbitrary area of 
the original in this embodiment. 
To designate an arbitrary area of the original, as shown in FIG. 2, an 
original 21 is set upside-up onto an original pressing plate 20. A lattice 
pattern sheet 22 is put on the original 21 set, thereby allowing the 
position of the original to be accurately known (FIG. 3). The original is 
set so that the left upper edge portion of the original coincides with the 
left upper edge portion of the sheet 22. In the diagram, the lattice 
pattern of the sheet 22 is displayed so that the left end is used as a 
reference position. A digitizer is embedded in the upper surface of the 
original pressing plate 20. By pressing two points (X.sub.i, Y.sub.i) and 
(X.sub.j, Y.sub.j) on a diagonal line in the portion which was area 
designated, the area having the diagonal line specified by these two 
points can be designated. 
Although the area designated original 21 is then set onto an original base 
glass plate 23 as shown in FIG. 4, the front and back sides are reversed. 
As shown in FIG. 5, the original 21 is set onto the glass plate 23 in a 
manner such that the left upper edge of the original coincides with the 
left upper edge portion of the glass plate 23. In this diagram, the 
original is displayed so that the left end is used as a reference 
position. Therefore, the top and bottom of the original in the Y direction 
are reversed. 
In this manner, the original 21 which was put on the original pressing 
plate 20 is set upside-down onto the original base glass plate 23 so that 
the left end of the original 21 is used as a reference position. Thus, the 
values which were read by the digitizer are the same as the position in 
the X direction of the actual original 21 on the glass plate 23 but are 
opposite to the position in the Y direction of the original 21. 
The coordinates designated by the digitizer are A/D converted into the 
digital values as shown in FIG. 6. The digital values are input to a CPU 
and arithmetically operated and stored into a memory (RAM). An output 
signal processed by the CPU is input to a drive circuit, thereby 
controlling the light-on and light-off of the LED array. 
The light-on/off operations of the LED array in the original scanning 
direction (X direction) are controlled by the timing of the position of 
X.sub.i and by the time interval from X.sub.i to X.sub.j. The light-on/off 
operations of the LED array in the direction (Y direction) perpendicular 
to the original scanning direction are controlled on the basis of the 
number of LEDs which are lit on. Since the position of the original on the 
digitizer is opposite to the position on the original on the original base 
glass plate with respect to the Y direction, this correcting process is 
also executed by the CPU. 
The electrostatic latent image which was obtained by erasing an arbitrary 
area of the original functions to develop the non-erased area by a first 
developing unit (developing unit for a photograph) 5. Next, at the 
position of a second developing unit 6, the second developing unit 6 is 
moved away from the photo sensitive drum 1 to prevent that the development 
is performed by the second developing unit 6. Or, means for applying such 
a bias as to prevent the development with the second developing device 6 
kept in contact with the drum 1 or other means is used. The image which 
was visually formed by the developing apparatus in which the value of 
.gamma. is small for use as a photograph is electrostatically transferred 
by a transfer charging device 7 onto a paper 9 which was conveyed via a 
paper feed guide 10. Further, the paper is separated from the drum 1 by a 
separate discharging device 8 and conveyed by conveying means 11 and the 
image on the paper is fixed by a fixing device 12. The paper having the 
fixed image is returned to a position near the paper feed guide 10 through 
a conveying path 14 for a multi-copy by switching means 13. 
The residual toner on the photo sensitive drum 1 after the image was 
transferred and separated is eliminated by cleaning means 15. The 
potential on the drum is made uniform by discharging lamp 16 and 
thereafter, the next operating cycle follows. An electrostatic latent 
image according to the light image 3 from the original is formed on the 
drum 1 which was uniformly charged by the charging device 2 in a manner 
similar to the preceding cycle. However, in this case, the area which was 
erased by the LED array 4 in the preceding cycle is not erased. On the 
contrary, the area which was not erased in the preceding cycle (in this 
case, the area to be erased and the area which is not erased can be newly 
designated) is erased. 
The area which was designated in the preceding cycle is stored in the 
memory (RAM). In the present cycle, the designated area is accessed from 
the memory (RAM) by the CPU and arithmetically operated. The light-on t 
imings of the LEDs and the number of LEDs which are lit on are controlled 
in a manner such that the original scanning direction and the LEDs which 
are lit on are completely opposite to those in the preceding cycle. 
The image in the area which was not erased in the present cycle is 
developed by the second developing unit (for a line) 6. However, since it 
is not developed at the position of the first developing unit 5, the first 
developing unit 5 is moved away from the drum 1 or such a bias that the 
development is not performed with the first developing unit 5 held in 
contact with the drum 1 is applied in a manner similar to the case of the 
second developing unit 6 in the preceding cycle. The paper having the 
image which was visually formed by the developing appaaatus in which the 
value of .gamma. is large for use of a line is electrostatically 
transferred by the transfer charging device 7 onto the copy paper which 
was developed by the first developing unit 5 in the preceding cycle and 
was conveyed at the timing by a resist roller 17 in accordance with the 
position of the image on the drum. The paper having the transferred image 
is separated from the drum 1 by the separate discharging device 8. 
Thereafter, the paper is conveyed by the conveying means 11 and is fixed 
by the fixing device 12 and then ejected out of the copying machine by the 
switching means 13. Thus, the copy in which the line portion and the 
photograph portion are synthesized is completed. 
The operation of the developing unit in the automatic synthesis copying 
mode will now be explained with reference to FIG. 7. 
In general, when using the overlap development, the developing unit in the 
inoperative mode is moved away from the photo sensitive drum by a plunger, 
eccentric cam, or the like. Or, spikes of a developing agent on a 
developing cylinder are mechanically cut or other mechanical method is 
used. 
On the other hand, in the jumping development, as compared with the 
magnetic brushes of two components, since the developing agent is not come 
into contact with the photo sensitive drum, there is also a case where it 
is sufficient to apply only a developing bias. 
After the area designation mode, .gamma. selection mode, and .gamma. mode 
were selected by the operation buttons, when a copy button is pressed, the 
copying machine operates in the automatic synthesis copying mode by the 
CPU. 
An explanation will now be made with respect to the operation when an 
output of a high voltage transformer for the first development is applied 
to the first developing unit 5 in the case where an arbitrary area of a 
photograph is copied by the first developing unit 5. 
When a set value of a density adjusting volume (not shown) is input to the 
CPU and arithmetically operated, a DC bias control signal is input to the 
high voltage transformer for the first development through a D/A 
converter. This control signal is input to a differential amplifier. An 
output of the differential amplifier is input to a DC-DC inverter to which 
an output from a frequency variable oscillating circuit is supplied. 
Pulses generated from a pulse oscillating circuit are current amplified 
and boosted by a boosting transformer, so that the boosted AC component is 
obtained. An output of the DC-DC inverter is added to the boosted AC 
component in the boosting transformer. An output of the boosting 
transformer is applied to first developing unit. At this time, a DC bias 
SW circuit and an AC bias SW circuit of the high voltage transformer for 
the first development are switched so as to generate the DC and AC high 
voltages. In response to the signal of the CPU, the AC output of the high 
voltage transformer for the second development is turned off and only the 
DC high voltage output is turned on by the DC bias SW circuit. The voltage 
of the high voltage transformer for the second development is set to such 
a value that the toner for the first development is not developed from the 
developing unit onto the drum. 
For the AC bias of the first developing unit, the peak to peak voltage 
V.sub.pp is set to 1000V and the frequency is set to 800 Hz. The DC 
component is set to 100V at the reference density. Therefore, the 
characteristics in which the value of .gamma. is small as shown by the 
alternate long and short dash lines in the first and second quadrants in 
FIG. 9 are derived. Thus, the image such as a photograph image having 
gradations is reproduced with a high fidelity. Further, by changing the DC 
component of the developing bias by use of the density adjusting volume, 
the density can be also varied. 
Next, in the second-time copy for a diagram which was stored in the ROM, in 
a manner which is completely opposite to the case of the photograph copy, 
the high voltage transformer for the second development is controlled so 
that the DC and AC components are turned on in a manner similar to the 
foregoing case of the first development. On the contrary, the high voltage 
transformer for the first development is controlled such that the AC high 
voltage component is turned off and the DC high voltage component is set 
to such a voltage that the first developing toner is not developed onto 
the drum from the developing unit. 
For the AC bias of the second developing unit, the V.sub.pp is set to 1200V 
and the frequency is set to 1500 Hz. The DC component is set to 200V at 
the reference density. Therefore, the characteristics in which the value 
of .gamma. is large as shown by the solid lines in the first and second 
quadrants in FIG. 9 are derived. Thus, the diagram is reproduced with a 
high fidelity. On the other hand, similarly to the first developing unit, 
by changing the DC component of the developing bias by use of the density 
adjusting volume, the density can be varied. 
An area has been designated by the digitizer in this embodiment. However, 
the invention is not limited to this method. An area can be also key-input 
by reading the coordinates of the original. 
An operating method for the area designation automatic synthesis copy by 
the key-input will now be explained with reference to FIG. 8. 
First, an inside 31 or an outside 32 of the designated area is designated 
by pressing an area designation button 30. Numerals 33 and 34 denote LEDs. 
When either the inside 31 or the outside 32 is selected by the area 
designation button 30, the LED 33 or 34 is lit on to thereby indicate that 
the inside or the outside has been designated. Next, by pressing a .gamma. 
selection button 40, .gamma. of the designated area is selected. For 
example, when the inside of the designated area is set into the copy for a 
photograph, the inside 31 is selected by the area designation button 30 
and a photograph 41 is selected by the .gamma. selection button 40. Next, 
the coordinates of the designated area are designated by inputting two 
points on the diagonal line of a rectangular area by a keyboard 70. In 
this case, after an input key 71 was pressed, the coordinates (X.sub.1, 
Y.sub.1) and (X.sub.2, Y.sub.2) are input. Each time one coordinate has 
been input and after all of the coordinates were input, the input key 71 
is pressed, thereby distinguishing the coordinates input operation from 
the display of the number of copy sheets. For example, assuming that 
X.sub.1 =10, Y.sub.1 =5, X.sub.2 =20, and Y.sub.2 =15, the keyboard 70 is 
operated by pressing the keys as follows. 
##STR1## 
Next, either one of the two methods is selected: namely, a method whereby 
only the designated area is copied (61) by the selected .gamma. by 
pressing a Y mode selection button 60; and a method for an automatic 
synthesis copy (62) whereby the designated area is copied by the selected 
.gamma. and the other area is copied by the other non-selected .gamma. 
(e.g., line mode). 
After the area designation, .gamma. selection, coordinate designation, and 
.gamma. mode were selected as described above, a copy button 80 is pressed 
to start the copying operation. 
There is another method whereby the respective display panels 61 and 62 are 
also directly used as copy buttons without providing the .gamma. mode 
selection button 60. 
Although one rectangular area has been designated in this embodiment, it is 
also possible to designate two or more areas or an area of a complicated 
shape if the capabilities of the digitizer and CPU and the memory capacity 
are sufficient. On the other hand, by use of a CCD, an area written on an 
original can be also designated. 
On the other hand, the developing units have been used to copy for line and 
photograph in the foregoing embodiment. However, variable adjusting means 
for continuously changing .gamma. can be also provided. The invention can 
be also applied to the case where three or more developing units are used. 
Further, if the development characteristics are switched every time, it is 
sufficient to use one developing unit. For the development 
characteristics, there is no need to change all of the voltage and 
frequency of the AC component and the voltage of the DC component but only 
a part of them can be also changed. 
In addition, although the LED array has been used as the charge erasing 
means, other means such as a liquid crystal shutter array or the like can 
be also used. 
An area can be also determined by previously discriminating whether the 
copy mode is the photograph mode or the line mode. This discrimination can 
be performed from a level distribution of a histogram of an output of the 
CCD corresponding to one page of an original. 
As described above, for an original such that photographs and characters 
mixedly exist, a copy image which satisfies both of the photographs and 
the characters can be obtained by simple operations. 
The foregoing first embodiment relates to the example in which areas having 
different kinds of characteristics of an original are manually set. 
The second embodiment will now be explained with regard to an example in 
which areas of different kinds of characteristics are automatically 
discriminated and processed. 
FIG. 10 is a schematic diagram of the second embodiment of the invention. A 
reference original 101.sub.1 having a low background density (reflecting 
density of the background portion is 0.07) as shown in FIG. 11 is used as 
a reference. A newspaper original 101.sub.2 having a high background 
density (reflecting density of the background portion is 0.25) and a 
photograph original 101.sub.3 having a wide gradation range (an image 
having continuous gradations such that the reflecting density lies within 
a range from 0.2 to 1.3) mixedly exist in an original 101. The user puts 
on the original 101 onto an original setting base 102 and presses a copy 
button on an operation unit (not shown). Thus, prior to executing the 
copying operation, a halogen lamp 103 and a first mirror 104 scan the 
original 101 at a speed of v.sub.1 mm/sec. A second mirror 105 and a third 
mirror 106 scan the original 101 at a speed of v.sub.1 /2 mm/sec. In this 
manner, the original is detected and areas are discriminated. The lamp 103 
and the first to third mirrors 104 to 106 are forwardly moved from a 
position HP and then returned to the position HP, thereby finishing a 
single scanning operation. The rated values of the halogen lamp 103 are 
80V and 200 W. When the original is detected and areas are discriminated, 
the lamp 103 is lit on at a voltage of about 60V and the original 
information is input to a CCD 156 through a reducing lens 155. The CCD 156 
is disposed at the position such as not to disturb the image exposing 
light which is input to a lens 107. The original information which was 
input to the CCD 156 is supplied to a DC controller 109 through the A/D 
converter 158. The original information is sampled every 1 mm in the 
direction perpendicular to the scanning direction of the lighting system. 
In the A scan in FIG. 12, a histogram as shown in FIG. 13 is formed by the 
DC controller 109. In the B scan in FIG. 12, a histogram as shown in FIG. 
14 is formed by the DC controller 109. As shown in FIG. 13, the output 
value of the CCD is 32 in the case of the reflecting density of 0.07 of 
the background portion of the reference original 101.sub.1, while the 
output value of the CCD is 20 in the case of the reflecting density of 
0.25 of the background portion of the newspaper original 101.sub.2. There 
is a large difference between them. Therefore, it is possible to decide 
that the area between Y.sub.1 and Y.sub.2 of the Y coordinates is the 
original in which the background portion is dark. 
The CCD output value is the digital value which is obtained by dividing the 
reflecting density range from 0.07 to 1.4 into 32 levels. For example, 
there are the following corresponding relations between the reflecting 
density and the CCD output value. 
______________________________________ 
&lt;Reflecting density&gt; 
&lt;CCD output value&gt; 
______________________________________ 
0.07 32 
0.25 20 
1.3 5 
______________________________________ 
The original information is also sampled every 1 mm in the scanning 
direction of the lighting system. In the X direction of the original, 
histograms are also formed similarly to the case of the Y direction in 
FIG. 13. Thus, the area between X.sub.1 and X.sub.2 of the X coordinates 
can be detected as the original having the dark background portion. 
The areas of the photograph original 101.sub.3 and reference original 
101.sub.1 are detected in the following manner. Namely, in the Y 
direction, as shown in FIG. 14, the reflecting density lies within a wide 
range from 0.2 to 1.3 in the case of the photograph original, so that the 
CCD output value also has dispersive values. Therefore, the function such 
that when the CCD output value has dispersive values in a certain area, it 
is determined that the original is the photograph original is provided for 
the DC controller 109. Due to this, the area between Y.sub.3 and Y.sub.4 
of the Y coordinates can be detected as a photograph original. 
In the X dieection, the area between X.sub.3 and X.sub.4 of the X 
coordinates can be also similarly detected as a photograph original. 
After completion of the foregoing detecting process, the optical system is 
returned. When the position of the HP is detected, the exposure and scan 
are restarted and the copying process is executed three times in the 
multi-copy mode. In the first copying process, an OPC photo sensitive 
material 110 having a diameter .phi. of 108 mm which is rotating in the a 
direction at a peripheral speed of v.sub.1 mm/sec is primary charged by a 
primary charging device 111 so that the dark portion potential V.sub.D of 
-650V is held on the photo sensitive material 110. The halogen lamp 103 
and the first to third mirrors 104 to 106 operate under the same 
conditions as those in the original detecting process. The lamp voltage is 
set to 60V. An image exposing light 115 is irradiated onto the OPC photo 
sensitive material 110 through a fourth mirror 112, a fifth mirror 113, 
and a sixth mirror 114 which are fixed. Thus, an electrostatic latent 
image of the light portion potential V.sub.L =-170V is formed. However, 
the electrostatic latent images formed in the area 101.sub.2 corresponding 
to the newspaper original which is surrounded by the coordinates (X.sub.1, 
Y.sub.1), (X.sub.1, Y.sub.2), (X.sub.2, Y.sub.1), and (X.sub.2, Y.sub.2) 
and in the area 101.sub.3 corresponding to the photograph original which 
is surrounded by the coordinates (X.sub.3, Y.sub.3), (X.sub.3, Y.sub.4), 
(X.sub.4, Y.sub.3), and (X.sub.4, Y.sub.4) are erased by controlling the 
timings to light on the LEDs of a blank exposing light (LED array) 117 by 
a blank exposure control circuit 116. Next, the area consisting of only 
the reference original 101.sub.1 excluding the areas corresponding to the 
newspaper original 101.sub.2 and photograph original 101.sub.3 is 
developed as a visible image by a developing sleeve 118. The sleeve 118 
rotates in the b direction at a peripheral speed of v.sub.1 mm/sec and is 
applied with the peak to peak voltage of 1400V.sub.pp at 2000 Hz as a sine 
wave to which the DC component of -220V was applied. A transfer sheet 125 
is then fed by a first resist roller 119 at the transfer timing controlled 
thereby and passes through a transfer guide 120. The toner image on the 
photo sensitive material 110 is transferred onto the transfer sheet 125 by 
a transfer charging device 121. Thereafter, the transfer sheet 125 is 
separated from the photo sensitive material 110 by a separate discharging 
device 122 and conveyed to a fixing device 124 by a conveying belt 123. 
The residual transfer toner on the photo sensitive material 110 is 
collected by a cleaner 126. Then, the copy memory on the photo sensitive 
material 110 is erased by a pre-exposing lamp 127. In the case of a 
single-copy mode, the transfer sheet 125 conveyed by the fixing device 124 
passes through over a flapper 128 and is ejected out of the copying 
machine by discharging rollers 129. In the multi-copy mode, the flapper 
128 is lifted up in the direction indicated by an arrow C and the transfer 
sheet 125 passes along a path as indicated by a broken line 151 and is 
enclosed onto a middle tray 130. 
After the first exposing scan had been finished, when the optical system 
was returned and the HP position was detected, the scan in the second 
copying process is started and only the area corresponding to the 
newspaper original is copied. The optimum voltage to light on the lamp 103 
is determined in accordance with the relation shown in FIG. 15 on the 
basis of the CCD output value corresponding to the background portion of 
the newspaper which was obtained by the original detecting process which 
had been first performed. Namely, in the case of the background reflecting 
density of 0.07 of the reference original, the CCD output value is 32. The 
light-on voltage of the lamp 103 is 60V at this time and the image without 
fogging is derived. In the case of the background reflecting density of 
0.25 such as in a newspaper original, the CCD output value is 20. At this 
time, by setting the light-on voltage of the lamp 103 to 70V, the image 
without fogging is derived. Therefore, the light-on voltage of the lamp 
103 in the second copying operation is set to 70V by the DC controller 109 
through a constant voltage regulator (CVR) 131. After the electrostatic 
latent image was formed at this voltage, by lighting on the blank exposing 
LED array 117, the electrostatic latent images in the areas other than the 
newspaper original area are erased. 
The electrostatic latent image of only the newspaper original area is 
developed by the developing sleeve 118 under the same conditions as those 
in the first copying mode. The transfer sheet 125 enclosed on the middle 
tray 130 is picked up and fed by paper feed rollers 131 and passes through 
separate rollers 132. The transfer sheet 125 is then conveyed to the first 
resist rollers 119 by second resist rollers 133 at the timing controlled 
thereby. In the first copying process, the newspaper original area and 
photograph original area on the transfer sheet 125 are the blank areas as 
shown in FIG. 16(i). However, in the second transfer process, the toner 
image is transferred to the area corresponding to the newspaper original. 
Thereafter, the transfer sheet is enclosed onto the middle tray 130 in the 
state as shown in FIG. 16(ii) under the same conditions as those in the 
first copying process. 
Next, in the third copying process, the image in only the area 
corresponding to the photograph original is copied. After the 
electrostatic latent image was formed under to same conditions (the 
light-on voltage of the lamp 103 is set to 60V) as those in the first 
copying process, by lighting on the blank exposure LED array 117, the 
electrostatic latent images other than the portion corresponding to the 
photograph original area are erased. To improve the reproducibility of the 
half tone, the development conditions are set as follows. Namely, the 
developing bias conditions are set such that the AC sine wave of V.sub.pp 
=1000V and V.sub.f =400 Hz is used and the DC component of -320V is 
applied to the developing sleeve 118 through a high voltage transformer 
134. 
FIG. 17 shows D.sub.o -D.sub.c characteristic curves. C denotes the curve 
under the developing bias conditions in the case of the reference 
original. D indicates the curve under the developing bias conditions in 
the case of the photograph original. It will be understood that the 
gradation reproducibility is fairly improved in the case of the photograph 
original. The electrostatic latent image corresponding to the photograph 
original developed under the developing bias conditions is developed as a 
visible image and transferred onto the transfer sheet 125 in the state as 
shown in FIG. 16(iii). Thereafter, the flapper 128 is put down in the 
direction opposite to the arrow C. The transfer sheet 125 then passes 
through the discharging rollers 129. The copying operation is completed in 
this manner. The operation of the flapper 128 is controlled by the DC 
controller 109 and a flapper drive circuit 160. 
FIGS. 18A and 18B show control flowcharts for the DC controller 109 to 
explain the area discriminating operation and the image forming operation. 
Step 1 relates to a flowchart for area discrimination. The pre-scan is 
performed. If a reference original area exists, a flag F.sub.1 is set to 
1. If a newspaper original area exists, a flag F.sub.2 is set to 1. If a 
photograph original area exists, a flag F.sub.3 is set to 1. 
If all of the flags F.sub.1, F.sub.2, and F.sub.3 have been set to 1, the 
foregoing three image forming processes are executed in steps 2 to 4 and 
the recorded paper is ejected out of the copying machine by the flapper 
128 in step 5. 
On the other hand, if the original consists of only the reference original 
areas, only the flag F.sub.1 is set to 1. Therefore, the processes in only 
step 2 are executed and the recorded paper is then ejected out. 
Similarly, if the original consists of only the newspaper original areas or 
photograph original areas, only the flag F.sub.2 or F.sub.3 is set to 1. 
The processes in only step 3 or 4 are executed and thereafter, the 
recorded paper is ejected out. 
In the case of the original in which two of the foregoing three kinds of 
original areas exist, the corresponding two of the three flags F.sub.1 to 
F.sub.3 are set and the processes in the corresponding two of the steps 2 
to 4 are executed. Thereafter, the recorded paper is ejected out. In this 
way, only the necessary processes are executed and the multiple copy image 
can be derived. 
In this embodiment, the means for varying the lamp light-on voltage has 
been used as image forming means for the original having a dark background 
portion. However, means for varying the DC component of the developing 
bias can be also used. Or, a combination of these two types can be also 
used. 
On the other hand, means for varying the developing bias has been used as 
image forming means for the photograph original in the foregoing 
embodiment. However, as described in FIG. 9, it is also possible to use 
means for reducing the value of the dark portion potential, V.sub.D, for 
example, means for reducing the charging voltage of the charging device 
111 or means for decreasing an amount of exposing light. Not only the V - 
C.sub.o characteristic but also the E - V characteristic or the D.sub.o - 
E characteristic can be changed, or these three kinds of characteristics 
can be also changed. 
As described above, the original areas of different kinds of 
characteristics are automatically detected without designating the 
original areas and without selecting the image forming means by the user 
before the copying operation is performed. Even if various kinds of 
originals mixedly exist in one original, the optimum copy image can be 
obtained. 
The present invention is not limited to the foregoing embodiments but many 
modifications and variations are possible within the spirit and scope of 
the appended claims of the invention.