JPH0614211B2 - Copier with double-sided original mode and automatic exposure controller - Google Patents

Description

Description: TECHNICAL FIELD The present invention includes a copy mode for copying a double-sided original, and further includes an automatic exposure controller for automatically controlling the exposure amount according to the image density of the original. Related to copiers.

<Prior Art> An electrophotographic copying machine forms a latent image by optically projecting a document image on a recording medium, and develops the latent image.
The developed image is transferred to the paper. The sheet on which the developed image is transferred passes through the fixing unit and is ejected to the outside of the machine. With such a copying machine, the original is placed on a transparent original table,
The placed document is projected on a recording medium by illuminating and optically scanning. When a document is placed on a document table, it is generally performed manually or automatically. Some originals have an image formed on one side only, or have an image formed on both sides.
In particular, when copying a double-sided document with images formed on both sides, it is extremely troublesome to manually place the document on the platen each time, and an automatic document feeder that automatically performs this is required. It was proposed and put into practice.

On the other hand, the copying machine is provided with a device for automatically controlling the exposure amount in order to always obtain a proper image when copying a document having a dark background such as a document such as a newspaper, a blueprint document, and a color document. It became so. The automatic exposure control device of this copying machine detects a part of the reflected light of the document by the exposure light source or the like, and controls the exposure light source or the like according to the reflected light corresponding to the light and shade of the document, This is to obtain an appropriate copy density automatically. As a result, the contribution is extremely great in eliminating the trouble of manually adjusting the exposure amount. Further, the exposure control apparatus described above can perform optimum exposure control corresponding to various originals.

However, it is not always preferable to apply the optimum exposure control to some originals. For example, in the case of a double-sided original, if an attempt is made to control the optimum reference density by automatic exposure control, one side of the sheet original will be exposed (during optical scanning), and the image on the other side of the original will be formed by the light transmitted through the original by the exposure light source. Even exposure and copying can occur. Therefore, if image exposure is performed in such a state, image exposure is also performed on an image on a surface other than the exposed surface, often causing a problem that the copied image becomes difficult to read. In such a case, a copying machine having an automatic exposure control device can usually release the automatic exposure control and manually perform an exposure adjustment operation. However, this does not take advantage of the automatic exposure control in the first place.

<Purpose> The present invention, in a copy mode for copying from a two-sided original,
An object of the present invention is to provide a copying machine in which an automatic exposure control device can control an exposure amount according to a document image so that an image on a surface (back surface) opposite to a copying surface (front surface) is not formed.

<Example> An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of automatic exposure control according to the present invention, and FIG. 2 is a schematic diagram of a copying machine according to the present invention.

First, the structure of the copying machine according to the present invention will be described with reference to FIG. The document is placed on the transparent document table 1 via, for example, the automatic document feeder 2 or manually. The document on the platen 1 is illuminated by the illumination device 3, and a part of the optical unit 4 including the illumination device 3 is optically scanned by running along the platen 1. As a result, the reflected light from the document is projected onto the surface of the photoconductor 5 having a photoconductive layer which is a recording medium via the optical means 4 including a mirror and a lens.

The photoconductor 5 is rotated in the direction of arrow 6 in synchronism with the means for optically scanning the original document, is uniformly charged in advance by the corona discharger 7, and the light and shade information of the original document is exposed.
An electrostatic latent image is formed on the surface. The developing device 8 arranged immediately after the position where the image of the original is exposed is for developing the latent image on the surface of the photoconductor 5. The developed image on the surface of the photoconductor 5 is transferred by the action of the transfer corona discharger 10 to one surface of the paper which is sent through the synchronous roller 9 which conveys the paper in synchronization with the rotation of the photoconductor 5. It Further, the transferred sheet is electrostatically peeled from the photoconductor 5 by the peeling corona discharger 11, and is conveyed to the fixing roller 13 via the conveyance belt 12. An image on the upper surface of the sheet that has passed through the fixing roller 13 is fixed, and the sheet processing apparatus 15 mounted on the sheet discharge port of the copying machine main body through the sheet discharge roller 14.
And processed.

The sheet processing device 15 determines whether the discharged sheets are discharged onto each tray to perform page alignment or to discharge all sheets to a specific tray. In the case of double-sided copying, the copy sheet (one side of which has been copied) is conveyed again to the intermediate tray 16 on the main body side of the copying machine. This intermediate tray 16
The sheet is fed to the sheet in response to the operation of the double-sided copy mode setting key 17 arranged on the operation panel. Therefore, the switching gate 18 for switching the conveying path is provided with the fixing roller 1.
3 is provided between the sheet discharging roller 14 and the sheet discharging roller 14, and the gate 18 is switched so that the sheet is discharged to the sheet processing device 15 after the double side copying in the single side copying mode or the double side copying mode is completed. The double-sided copy mode setting key 17 switches to the double-sided copy mode when operated in the single-sided mode, and switches to the single-sided copy mode when operated in the double-sided copy mode. Further, the switching gate 18 is the first gate in the double-sided copy mode.
It is possible to switch to the position where the paper discharge path is closed when copying to the surface. In this way, in the double-sided copy mode, the sheet copied on one side is guided to the conveyance path 19 via the switching gate 18 and sent to the intermediate tray 16 via the conveyance roller 20 in the main body of the copying machine. At this time, the image surface faces upward, and the lower surface is stored in the intermediate tray 16 in a blank state.

The paper is fed from the paper feed cassette 21 or the intermediate tray 16 to the synchronization roller 9. The feeding from the sheet feeding cassette 21 is performed when copying to the first side of the sheet regardless of one side or both sides. Further, the feeding of the paper from the intermediate tray 16 is performed when the image is formed on the second surface (back surface) of the paper after the copying on the first surface of the paper.

On the other hand, the automatic document feeder 2 feeds the originals placed on the paper feed tray 201, for example, one by one from the lowermost original, feeds the originals to the specified position of the conveyance path 1, and after the scanning is completed, the paper ejection tray 202.
It's discharging above. Here, if the original is a single-sided original,
After the end of the optical scanning carried to the original table 1 via the carrying path 203, the paper discharge table 2 is carried via the carrying paths 204 and 205.
It is discharged to 02. In this case, the image side of the one-sided original is placed on the paper feed table 201 with the image side facing upward.

If the original is a double-sided original, it is necessary to make a copy from the lower surface of the original placed on the paper feed tray 201. Therefore, the original is first sent to the original table 1 via the conveying path 203, the feeding is reversed and guided to the conveying paths 204 and 205, and the feeding direction is reversed again in the conveying path 205. Then, it is conveyed to the reflected light 206, and the feeding direction is reversed, and is conveyed to the document table 1 via the conveyance path 207. As a result, the lower surface of the original facing the paper feed table 201 faces the original table 1 and optical scanning is performed. When this scanning is completed, the original is conveyed in the same conveying procedure as described above, and the document is conveyed in the conveying path 2.
It is inverted at 06 and is conveyed to the document table 1 through the conveyance path 207. At this time, the document surface faces the document table 1 on the side opposite to the surface on which the document was previously exposed. When the image exposure of this original is completed, the original is ejected onto the ejection tray 202 via the conveyance paths 204 and 205. The above is an example of conveyance control for automatically conveying a double-sided original to the original table 1. As described above, it is the double-sided original mode setting key 23 arranged on the operation unit of the copying machine that sets each copy mode of the single-sided original or the double-sided original. This setting key 2
Reference numeral 3 switches to the double-sided original copy mode by operating in the single-sided original copy mode, and switches to the single-sided original copy mode by operating in the double-sided original copy mode.

According to the present invention, in the copying machine having the above-described structure, the photoelectric conversion element 22 is provided in order to automatically adjust the exposure amount and obtain a clear image when a single-sided or double-sided original is exposed and copied. . The photoelectric conversion element 22 is arranged at a position where a part of the reflected light from the document illuminated by the illumination device 3 is incident, and particularly, the illumination device 3 traveling along the document table 1.
Mounted on a support that supports the.

FIG. 3 is a control block diagram for explaining the outline of the exposure control apparatus according to the present invention. Although not shown, the exposure adjustment is performed by operating the exposure adjustment dial provided on the operation unit of the copying machine, for example. Explaining this operation, the exposure lamp _3-1 which constitutes the illumination device 3
An AC power supply 24 and a bidirectional thyristor 25 are connected in series with each other. In addition, the AC power supply 24 is a voltage generation circuit 26.
Is connected and the bidirectional thyristor 25 is turned on,
The voltage corresponding to the voltage across the exposure lamp _3-1 is extracted, and the voltage corresponding to the effective value voltage of the output voltage is output. This output voltage and the reference voltage 27 generated by the variable resistor connected to the exposure adjustment dial are compared by the comparator 28. If there is a voltage difference between the two voltages, it is determined according to the magnitude of the difference. Output a signal. The output signal of the comparator 28 is input to the trigger pulse generation circuit 29. The trigger pulse generation circuit 29 uses the AC power supply 24.
The trigger pulse synchronized with the frequency is output, and the generation phase of the trigger pulse is controlled according to the output signal of the comparator 28. The controlled trigger pulse is
It is supplied to the gate of the interactive bilith 25. Thus a variable resistor for setting a reference voltage amount of the exposure lamp 3 _-1 by varying increases or decreases, it is possible to select the amount of light in accordance with an original.

In view of these, the automatic exposure control apparatus of the present invention was devised so that the reference voltage can be automatically changed according to the type of original, that is, the single-sided or double-sided copying mode. Will be described in detail. FIG. 1 is a block diagram showing an example of an automatic exposure control apparatus according to the present invention. The reference voltage 27 shown in FIG. 3 is generated by a variable resistor.
It is output as a collector voltage of 0. This transistor 3
0 is controlled according to the intensity of the reflected light from the document surface. To explain this configuration and operation, a part of the reflected light from the document illuminated by the exposure lamp _3-1 is detected by the photodetector circuit 31 including the photoelectric conversion element 22, and the output voltage thereof is sent to the differential integrator 32. Is entered.

On the other hand, the fixed voltage 33 is also input to the difference integrator 32, and the voltage difference between the output voltage of the photodetection circuit 31 and the fixed voltage 33 is integrated by the difference integrator. Therefore, the difference integrator 32
Output voltage increases and decreases depending on the magnitude of the output voltage of the photodetector circuit 31 and the fixed voltage. The output signal of the differential integrator 32 is input to the base of the transistor 30 and controls the collector voltage. In this operation, when there is no voltage difference between the output voltage of the light detection circuit 31 and the fixed voltage 33, the output voltage of the difference integration circuit 32 is held. Therefore, the base voltage of the transistor 30 is constant, and the collector voltage input to the comparator is constant. Therefore, the light quantity of the exposure lamp is kept constant by the operation described in FIG.

Next, when the output voltage of the light detection circuit 31 rises in response to the reflected light of the original, a positive voltage difference is generated between the output voltage of the fixed voltage 33 and the fixed voltage 33. The voltage increases. Then, the base voltage of the transistor 30 increases and the internal resistance of the transistor 30 decreases, so that the collector voltage decreases. The collector voltage is comparator 2
8 is the input voltage, the trigger pulse generation circuit 29 is controlled by the output voltage of the comparator 28 as described with reference to FIG.
Is controlled, the exposure lamp 3 _-1 voltage (effective value) decreases. Therefore, the output voltage of the photodetector circuit 31 decreases, and the voltage difference from the fixed voltage 33 decreases. By repeating these operations, the output voltage of the photodetector circuit and the fixed voltage 3
It becomes stable when the voltage difference from 3 is zero.

When the output voltage of the photodetector circuit 31 falls below the fixed voltage 33, a negative voltage difference occurs, so that the base voltage of the transistor 30 decreases and the collector voltage increases. Thus as the description of FIG. 3, the input voltage of the exposure lamp 3 _-1 increases and the output voltage of the light detection circuit 31 is also increased. Also in this case, the output voltage of the photodetector circuit 31 and the fixed voltage 33 are stable in a state where there is no voltage difference.

The fixed voltage 33 for adjusting the exposure amount according to the present invention is
It is constructed as shown in FIG. That is, the fixed voltage serving as a reference for the exposure amount includes a fixed voltage (first reference voltage) 41 for a single-sided original and a fixed voltage (second reference voltage) 42 for a double-sided original, and each switch 43. One of the fixed voltages is supplied to one terminal of the difference integrator 32 via the terminals 44 and 44. The switch 43 has contacts S1 and S2,
Normally, the connection piece S3 is tilted to the contact S2 side, and in the case described later, the connection piece S3 is manually switched to the contact S1 side. The switch 44 also has contacts S1 and S2,
When the double-sided original copy mode is set by the double-sided original copy mode setting key 23, the connecting piece S3 is switched to the contact S2 side. In the single-sided original copy mode, the connecting piece S3 is connected to the contact S1.
Switches. The contact S1 side of the switch 44 is connected to the single-sided original fixed voltage 41 together with the contact S1 of the switch 43, and the contact S2 side is connected to the double-sided original fixed voltage 42. The fixed voltage 42 for the double-sided original is set to be smaller than the fixed voltage 41 for the single-sided original, and is set to be smaller than the exposure amount of the single-sided original when copying the double-sided original. The single-sided fixed voltage 41 is set to a value that provides the optimum image density as in the conventional case.

When the copying machine is set to the double-sided original copy mode by the double-sided original mode setting key 23, the fixed voltage 42 for the double-sided original is selected. This means that the fixed voltage 42 is preferentially selected, and if it is desired to select the single-sided original fixed voltage 41 in the double-sided original copy mode,
It can be selected by manually operating the switch 43.

In order to better understand the structure of the present invention, first
The operation of the figure will be described.

When the single-sided copy mode is set by operating the double-sided original copy mode setting key 23, the connection piece S3 of the switch 44 is switched to the contact S1. Further, in the switch 43, the connecting piece S3 is tilted toward the normal contact S2 side. Therefore, the one-sided fixed voltage 41 is supplied to one terminal of the difference integrator 32. This single-sided fixed voltage 41 is a voltage set to obtain a copy which is generally considered to be the optimum density at present. Therefore, the copy in the single-sided copy mode is copied at the optimum density by the automatic exposure control device having the single-sided original fixed voltage 41.

Subsequently, when the double-sided copy mode is set by the double-sided original copy mode setting key 23, the switch 44 is interlocked with this.
The connecting piece S3 of is preferentially connected to the contact S2 side. Along with this, the fixed voltage 42 for double-sided original is input to one terminal of the difference integrator 32. Since this fixed voltage 42 is lower than the fixed voltage 41 for single-sided originals, the difference integral value between the output voltage of the photodetector circuit 31 and the fixed voltage is the fixed voltage 42 for double-sided originals in the case of reflected light of the same original. It becomes larger in the double-sided document copy mode used. Therefore, the force from the differential integrator 32 also increases, and the input voltage input from the transistor 30 to one end of the comparator 28 decreases. As a result, the output of the exposure lamp _3-1 is
In the double-sided original copy mode, the amount becomes smaller than in the single-sided original copy mode, and the amount of light emitted by the exposure lamp _3-1 decreases. In addition, the image density becomes high. In this way, since the output of the exposure lamp _3-1 is set low in the double-sided original copy mode, when the one side of the double-sided original is exposed,
The problem that the image on the other surface is exposed by transmission can be reduced.

It should be noted that the output of the exposure lamp _3-1 is set to the fixed voltage 42 for the double-sided original so that the output can be reduced to the highest output that can be reduced.
Is preferably set. Furthermore, the exposure lamp 3
The output of _-1 is preferably set to a value such that the corresponding image density does not deviate from the appropriate image density range. Here, the appropriate density range refers to a density range that allows easy visual image identification.

In the above description, the switch 43 is connected only to the connection piece S3 contact S2 side, but it can be connected to the contact S1 side by the manual operation, that is, the signal 45 of the manual set key. By this operation, it becomes possible to prohibit the selection of the fixed voltage 42 for the double-sided original that was linked with the double-sided original copy mode. In other words, even when copying double-sided originals,
When it is desired to give priority to the optimum density copy, the fixed voltage 41 for a single-sided original can be selected by switching the switch 43.
The switch 43 may cause the connection piece S3 to automatically return to the contact S2 side by the copy completion signal 46 after completion of copying corresponding to a certain copy condition, for example, the set copy condition.

Further, the method of inputting the fixed voltage to one end of the difference integrator 22 may be the method of FIG. 4 apart from the above. This is because the double-sided original or single-sided original fixed voltage is not selected in conjunction with the double-sided original or single-sided original copy mode, but normally, the connecting piece S3 of the switch 47 is always connected to the contact S1 side and the differential integrator is connected. A first fixed voltage 410 corresponding to the single-sided original fixed voltage 41 is input to one end of 32. Therefore, the first fixed voltage 410 is selected regardless of whether the double-sided original mode or the single-sided original copy mode is selected.

In the case of double-sided document copying, if it is desired to prevent the image on the non-exposed surface from being transmitted and exposed, if the connecting piece S3 of the switch 47 is connected to the contact S2 by manual operation, one side of the differential integrator 32 will be double-sided. A second fixed voltage 420 corresponding to the original fixed voltage 42 and lower than the first fixed voltage 410 is input. In the example of FIG. 4, the first fixed voltage 410 is preferentially set regardless of the single-sided original or double-sided original copy mode. When the first fixed voltage 410 is set, the optimum image density can be obtained. For example, if the original itself is a thick one that is not transparent, it is desirable to set the optimum first fixed voltage 410 when copying a single-sided or double-sided original. Here, if the original is transparent,
It is desirable to set the second fixed voltage 420 at the time of copying the two-sided original, and in FIG. 4, the second fixed voltage 420 is set by manually switching the switch 47 to the contact S2 side. In this case, in the embodiment of FIG. 1, the second fixed voltage 420, that is, the double-sided document fixed voltage 42 is preferentially set when the double-sided document copy mode is set. In this way, the fixed voltage serving as the concentration reference may be set preferentially as necessary.

As described above in detail, in the present invention, when copying a double-sided original, the output of the exposure lamp is automatically set low so that the image density corresponding to the output becomes a high level within the proper image density. Therefore, it is possible to prevent or reduce the transmissive exposure of the image on the other surface that accompanies the first surface exposure in copying the double-sided original.

According to the present invention, when scanning a document, the document table 1 is fixed and a part of the illuminating device 3 and the optical means 4 is run. However, the invention is not limited to this, and the document table 1 itself may be moved. Even if the original is scanned, the same operation can be performed. Further, in the present invention, the document is automatically conveyed by using the document automatic feeder 2. However, it is needless to say that the document may be manually handled without being limited to this device.

<Effect> According to the present invention, the exposure amount is controlled in order to change the image density, and it is possible to easily obtain an appropriate image density according to each copy mode. For example, when copying a two-sided original,
Since the exposure amount is controlled so that the light amount is reduced compared to when copying a normal single-sided original, the one side of the original (the surface facing the platen) to the other side (the surface opposite to the side facing the platen)
The image formed on the second side is not transmitted and exposed, and the image on the back side of the original is not thinly formed by overlapping with the image on the front side of the original by the double-sided original.

Therefore, it is not necessary to perform a very troublesome operation for manually adjusting the density level so that the image on the back side is not formed, and good copying can be performed only by designating the double-sided original mode.

[Brief description of drawings]

1 is a block diagram showing an automatic exposure control device according to the present invention, FIG. 2 is a sectional view showing an example of a copying machine according to the present invention, and FIG. 3 is a block diagram showing an outline of the automatic exposure control device according to the present invention. FIG. 4 is a block diagram of the essential parts showing another embodiment of the present invention. 1: Original plate, 3: Illumination device, 3 ₋₁ : Exposure lamp, 2
2: photoelectric conversion element, 23: double-sided original mode setting key, 3
1: Photodetector circuit, 32: Difference integrator, 33: Fixed voltage,
41: fixed voltage for single-sided original, 42: fixed voltage for double-sided original, 42, 43: changeover switch, 47: changeover switch,
410: first fixed voltage, 420: second fixed voltage.

Continuation of the front page (56) Reference JP 61-73966 (JP, A) JP 61-160769 (JP, A) JP 61-212862 (JP, A) JP 57-155557 (JP , A) JP 59-31973 (JP, A) JP 55-165065 (JP, A) JP 59-28138 (JP, A) JP 58-142363 (JP, A)

Claims (1)

[Claims] 1. A document exposure unit for illuminating a document placed on a document table and exposing the reflected light from the document on a photoconductor to expose it, and a detection unit for detecting the amount of reflected light from the document. Means for comparing the output value of the detecting means with a first reference value capable of obtaining an image of proper density; and automatic exposure amount control means for controlling the light quantity of the document exposing means based on the result of the comparing means. In a copying machine equipped with an automatic exposure control device provided, a double-sided document mode designating means for designating that a document is a double-sided document having images on both sides, and an exposure amount by the document exposing means above the first reference value. A second reference value set to a value that provides an exposure amount that reduces
The automatic exposure control device controls the exposure amount based on the comparison result with the first reference value by the comparison means in a state where the double-sided original mode is not designated by the double-sided original mode designating means, The exposure amount control is performed on the basis of the comparison result of the second reference value by the comparison means and the detection value of the detection means in a state where the double-sided original mode is designated by the double-sided document mode designation means. Copier equipped with double-sided original mode and automatic exposure controller.