JPS647373B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an image reproducing device such as a copying machine.

Conventionally, in copying machines, etc., in order to obtain images with appropriate density, operators must optimally set image reproduction conditions such as developing bias voltage, exposure amount, and charge amount each time a copy is made, depending on the type of document. Not necessarily,
This caused annoyance to the operator.

Therefore, in recent years, a method has been proposed that performs a preliminary scan before the main scan for copying the original, detects the image density during this preliminary scan, and automatically controls the image reproduction conditions according to this detected value. There is.

The present invention aims to improve an image reproducing device that performs such preliminary scanning and copying, and provides an image reproducing device that can quickly and appropriately reproduce images depending on the original. The purpose is to

That is, the present invention provides a photoelectric conversion means that has a plurality of light receiving elements and receives light according to the density of the original document and converts it into an electrical signal, and a photoelectric conversion means that relatively moves the original and the photoelectric conversion means back and forth. a moving means for slit-exposing a document by slit exposure; a taking-out means for taking out electrical signals in the arrangement direction of the plurality of light-receiving elements from the photoelectric conversion means; and after the moving means starts moving in one direction and moves in the one direction. 1st before the end
a first for allowing extraction of the electrical signal for a predetermined period of time;
a first signal output means for outputting a signal; a second signal for permitting extraction of the electric signal for a second predetermined period after the photoelectric conversion means starts scanning one line and before the end of scanning one line; a second signal output means for processing the electrical signals taken out from the first extraction means during generation of the first signal and the second signal, and a control means for optimizing the image reproduction conditions according to the processing results; and the moving means. an image reproducing means for reproducing the original image under image reproducing conditions optimized by the control means during the subsequent movement in the opposite direction to the one direction after the end of the movement in the one direction; The present invention provides an image reproducing device characterized by having the following features.

FIG. 1 is a side sectional view of a copying machine to which an exposure apparatus according to the present invention is applied.

In the figure, reference numeral 10 denotes a document table, which is moved in the direction of arrow A by means not shown. When the document table is moved to a predetermined position, it is returned to its original position by means not shown. A document exposure lamp 11 irradiates light onto the document placed on the document table 10 and sends an image of the document to an optical system.

The original image is first sent to a reflection mirror 12.
The light whose optical path is changed by the reflecting mirror 12 is projected onto a lens 13 and a reflecting mirror 14, and the above-mentioned image is formed on a photosensitive drum 15 by the reflecting mirror 14 and the lens 13.

In order to judge the content of the above document, photosensitive drum 1
A half mirror 16 placed at a predetermined position on the optical axis between the lens 13 and the reflection mirror 14 directs a portion of the reflected light to the reflection mirror 17 that sends it in a direction perpendicular to the direction of movement of the document table. The light obtained through the mirror 17 is focused on a photodetector 18, such as a blue photocell, which has photosensitive wavelength characteristics that match the emission spectrum of the original exposure light source and the photosensitive wavelength characteristics of the photosensitive drum.

The video signal of the original converted into an electrical signal by the photodetector 18 is judged by the circuit shown in FIG. Determine whether the original has low contrast and many halftones.

Referring to FIG. 2, IT1 is an input terminal that receives the output of the photodetector 18, and the output is input to the amplifier A _np . The signal amplified by amplifier A _np is sent to high pass filter HP and low pass filter
The high-frequency component and low-frequency component included in the signal are separated from each other, and the output of the high-pass filter HP is input to the waveform shaping circuit WF. The output of the low-pass filter LP is input to slice circuits S1 and S2 to which the density level signal is input, and the output of the slice circuit S2 is passed through an inverter I to a NAND gate.
It is applied to one input terminal of the NAND gate NG, and the output of the slice circuit S1 is directly applied to the other input terminal of the NAND gate NG.

The output of the waveform shaping circuit WF is input to a frequency-voltage converter (hereinafter referred to as an f-v converter) fvc1 via a gate G1 that is opened by a timing signal applied from an input terminal IT4. Meanwhile nand gate
The output of NG is applied to the fv converter fvc2 via the gate circuit G2 to which the timing signal applied from the input terminal IT4 and the output of the pulse generator PG are applied. Input terminal IT5 is an f-v converter fvc1,
This is a timing signal for inputting signals to fvc2 and sample hold SH. f-v converter fvc1,
The output of fvc2 is input to differential amplifier D. The output of the differential amplifier D is input to the sample hold SH by a timing signal input from the input terminal IT5. The output of the sample hold SH is sent via a control circuit DC to use the amount of developer attached to the photosensitive drum 15 as a control signal.

In FIG. 1, a cleaner 19 removes toner and the like on the photosensitive drum 15. As shown in FIG.

The photosensitive drum 15 has three layers: an insulating layer on the surface, a photoconductive layer, and a substrate (aluminum substrate) underneath.

A charger 20 positively charges the photosensitive drum 15. 21 is an AC charger, and reflection mirror 1
4. The image exposure of the photosensitive drum 15 by the lens 13 is slit exposure together with the AC discharge to the photosensitive drum 15 by the AC charger 21.

A developing plate 22 attaches toner in a developer to the electrostatic latent image formed on the photosensitive drum 15 to turn the latent image into a visible image.

Reference numeral 23 denotes an electrode roller which squeezes the liquid layer of developer on the surface of the drum after development, and a bias voltage of +200V is applied to it, which absorbs excess toner on the drum.

A charger 24 applies corona to the drum and electrically squeezes the developer on the drum surface that has been mechanically squeezed by an electrode roller.

A charger 25 transfers the toner on the photosensitive drum 15 onto the copy paper P by performing corona discharge while sandwiching the copy paper P.

The above-mentioned charger 20, AC charger 21, developing plate 2
2. Appropriately input the output of the aforementioned determination circuit J to the electrode roller 23, charger 24, and charger 25.

To explain the operation of the above-mentioned embodiment, when the copy command button (not shown) of the copying machine shown in FIG. The document table 10 starts moving at timing t ₁ and moves at timing t ₄ due to the position detection signal.
Stop at. Next, at _t5 , the document table begins to return to its original position, and then stops at _t6 due to the position detection signal.
In this embodiment, scanning is performed to determine the content of the document in the forward stroke from _t1 to _t4 , and the optical image of the document is exposed to the photosensitive drum in the return stroke from _t5 to _t6 . .

First, when the document table 10 starts moving in the direction of arrow A, the contents of the document are reflected by the reflection mirror 12, the lens 13,
An image is formed on a photodetector 18 via a reflecting mirror 14, a half mirror 16, and a reflecting mirror 17. Now the third
When detecting the content of a part of the manuscript as shown in the figure,
In the figure, the V direction is the direction of document movement, and the H
is the arrangement direction of the photodetectors. For example, in order to detect the shaded area surrounded by V ₁ V ₂ H ₁ H ₂ ,
The timing signals shown in D and E are generated as shown in FIG.

The rising signal at timing _t1 shown in FIG. 4A is inverted by the inverter Inv, and the one-shot OS1 is activated by this falling signal. The H level holding time of the one-shot OS1 is at timing _t1.
The information on the position of V1 on the document table 10 is transmitted to the photodetector 1 from
This is the time until the image is projected on 8. one shot
When OS1 falls, one-shot OS2 is activated as shown in FIG.

The exit from Oneshot OS2 is Oneshot OS3.
is applied to generate a signal as shown in FIG. 4D. Further, the output of the one-shot OS2 is input to the AND gate AG1. At the other end of the AND gate AG, there is a disk 17 provided on the vibration axis 17a of the reflection mirror 17, as shown in FIG.
Movement of the hole b is detected by a photocell 17c that detects light from a light source 17c through the hole. With such a detection signal, the time of one shot OS4 is the scanning time of one line.

At timing _t2 , the image content of the document on the document table 10 begins to be detected, and for example, between _t2 and _t3 , the image content of the document on the document table 10 starts to be detected.
It is assumed that the signal shown in F of the figure is obtained. Due to the vibration of the reflection mirror 17, data of the image of the original in a direction perpendicular to the moving direction of the document table enters the photodetector 18 in accordance with the inclination of the reflection mirror 17 when it vibrates. The data entering the photodetector 18 is converted into an electrical signal, the signal is amplified by the amplifier A _np , and then input to the high pass filter HP and low pass filter LP to separate the high and low frequencies of the image. Separate. The high frequency component obtained through the high pass filter HP is shaped into a pulse waveform as shown in Fig. 6 by the waveform shaping circuit WF, and is applied to the gate circuit G1, and is sent to the terminal
Only the signals included in the document content judgment area are extracted by the timing signal E inputted through IT4 and applied to the fV converter fvc1. f-V
The output of the converter fvc1 is set to 0 at the falling edge of the timing signal N applied to the terminal IT5. above f
-V converter fvc1 applies its output to differential amplifier D.

On the other hand, the output of the low pass filter LP is applied to slice circuits S1 and S2. slice circuit S1,
S2 compares the input signal with DC voltage levels wa, wo (shown in FIG. 6) corresponding to preset concentration levels applied to terminals IT2 and IT3, respectively. High level WO is applied to terminal IT3, and low level WO is applied to terminal IT2. The output of the slice circuit S1 is applied to the input terminal of the NAND gate NG, and the output of the slice circuit S2 is applied to the other input terminal of the NAND gate NG via the inverter I, so that a signal like H in FIG. 6 appears at the output of the NAND gate NG. , such output is the timing signal at terminal IT4 and the output of pulse generator PG (this frequency is the timing signal at terminal IT4)
(by changing this frequency, the standard for determining the document content can be selected) is applied to the gate circuit G2, and outputs a signal as shown in FIG. 6. This output is the f-V converter fvc
2, and a voltage proportional to the input pulse appears from its output as shown in FIG. The fV converter fvc1 is also reset at the falling edge of the signal N.

The outputs of the fV converters fvc1 and fvc2 are applied to a differential amplifier D, and the above-mentioned voltage difference is stored in a sample-and-hold circuit SH by a timing signal D applied from a terminal IT5. In response to the contents stored in the sample hold circuit SH, the bias voltage applied to the electrode roller 23 via the control circuit DC changes, thereby controlling the amount of toner attached to the photosensitive drum 15 on the developing plate 22.

Note that the amount of toner deposited on the photosensitive drum 15 can also be controlled by the charger 20, AC charger 21, developing plate 22, and chargers 24, 25, so the output of the sample hold circuit SH described above can be adjusted as appropriate by the device described above. It may be inserted into the control circuits DC-1 to DC-5.

At timing _t4 , the document table 10 reaches a predetermined position, and from timing _t5 , the document table 10 is moved back by a driving means (not shown), and during this return movement, the document table 10 is placed on the document table 10. The original copying operation is performed based on the above-described detection of the original content.

In controlling the content determination of the original, the half mirror 16 was used in the above example to send the original content to the photodetector 18, but a reflecting mirror may be used instead of the half mirror.

FIG. 7 shows the above example in which a reflecting mirror is used. Reference numeral 30 denotes a reflecting mirror, which is fixed with a support fitting 31 and is attached to a shaft 32 so that it can freely rotate.
It has 3,34. 34 is fixed to an ordinary bearing, while the other shaft 33 is fixed to a spring 35,
For example, it is fixed to a bearing 37 fixed to the central shaft of the rotary solenoid 36 via a spring such as a torsion spring. Rotating shaft 33 and bearing 3
7 is provided with a pawl that prevents the spring 35 from rotating, and absorbs the impact when the rotary solenoid is energized and when the return spring returns.
The load on the rotary solenoid 36 when the mirror support fitting 31 hits the holding members 38, 39 is reduced. Normally, the rotary solenoid 36 is not energized and the mirror 30 is biased toward the holding member 39 by the force of the return spring of the rotary solenoid.

The rotary solenoid 36 is activated by a predetermined timing signal (c in Fig.
When the mirror 30 is energized, it is fixed toward the holding member 38, and the document irradiation light is reflected by the mirror 30 in the direction B and focused on the reflecting mirror 17 or the photodetector array 18. When the scanning for determining the content of the document is completed, the rotary solenoid 36 is de-energized by the timing signal mentioned above, and the return spring causes the mirror 3 to close.
0 is fixed to a presser plate 39, and the document irradiation light is focused on the photosensitive drum 15 shown in FIG. 1 without being blocked by the mirror 28.

FIG. 8 shows a self-scanning linear image sensor 18a (one-dimensional) used as the photodetector 18 used in the embodiment shown in FIG. It has been removed. To explain further, in the embodiment shown in FIG. 8, the vertical scanning of the original is performed by mechanical movement of the original platen, and the horizontal scanning of the original is performed by electronic scanning of the image sensor. The reflecting mirror 17 can be omitted in the figure.

FIG. 9 is a block diagram of image sensor scanning and signal processing, which will be explained in accordance with the time chart of FIG. 14. 41 is a 1728-element linear image sensor (CCD121H manufactured by Fairchild),
Its block diagram is shown in FIG.

Reference numeral 42 denotes a control and output circuit, which has a timing generation circuit shown in FIG. 11 and an output circuit shown in FIG. 12. Control output circuit 42 receives a clock signal from clock signal generator 43. The generator 43 supplies the control output circuit 41 with a clock signal having a constant frequency set from a spatial frequency that satisfies the resolution necessary for document determination.

The timing generator shown in Fig. 11 consists of a 4-bit counter (hexadecimal counter) CC (9316PC manufactured by Fairchild) and a flip-flop FF (J
-K type), AND Gate AG, NAND Gate NG,
Timing signals φ _1A , φ _1B , φ _2A , φ _2B , φ _XA , φ _XB , F, φ _XB ,
Create SYNC, SWEEP SYNC.

The output shown in FIG. 12 consists of a transistor Q, resistors R1 to R16, diodes CR, capacitors C1 to C9, and an operational amplifier OA as shown in the figure.

The control output circuit 44 is connected to the linear image sensor 4
Various timing signals (shown in FIG. 13) necessary for one scan are generated from the clock signal and applied to the linear image sensor. The scanning synchronization signal (SWEEP SYNC) is linear during period _t7 to _t8 .
The light/excitation charge of each element of the image sensor 41 is
It is transferred to an internal shift register in parallel, and reading from the shift register is started from _t8 in synchronization with the signal high, and the output V- of the control output circuit 42 is transferred to the internal shift register.
The DC regenerated output signal is obtained at out. In order to extract and hold the amplitude component of the output signal, the signal H is delayed for a certain period of time using a monostable circuit, and then passed through the shaping circuit 4.
At step 5, the pulse signal is changed to a narrow pulse signal and is applied as a sampling signal to the sample and hold circuit 46, and the output signal is converted into a stepped signal signal. The output signal is filtered by a low-pass filter 47 to remove the weight of the sampling signal (O) to produce a smooth signal, and then is applied to the input terminal IT1 (FIG. 2) via a terminal (48).
The scanning synchronizing signal (U) is inverted by an inverting circuit 49 and then applied to the terminal IT4 in FIG. 2 as a horizontal scanning gate signal.

If a linear image sensor is used as described above, it is possible to eliminate a configuration that vibrates the reflecting mirror. Note that a planar (two-dimensional) element may be used as the image sensor.

FIG. 15 shows another embodiment of the determination circuit shown in FIG. 2, in which counters each count the number of pulses obtained from gate circuits G1 and G2.
Applied to CNT1 and CNT2, the counter
The contents of CNT1 and CNT2 are applied to the subtractor Sub,
The difference between counters CNT1 and CNT2 is obtained. The value of the difference is stored in the latch circuit L, and the D-A converter
It is converted into an analog value by CONV, and the bias voltage of the electrode roller 23 is controlled as described above.

Note that the counters CNT1 and CNT2 are initialized as follows. For example, if the content of the original contains only high-frequency components, 100 pulses are counted, and the content of the original contains only low-frequency components, and 100 pulses are stored. Counter CNT1 that counts pulses of area components
is initially set to a value of 100, and the other counter CNT2 is set to a value of 0. The above counters CNT1 and CNT2 count up from that value,
When both counters reach 50 up,
The subtractor Sub outputs the difference of 100, and the control circuit outputs a bias voltage intermediate between the high and low frequencies.

FIG. 16 is a block diagram showing another embodiment of the determination circuit shown in FIG. 2.

The output of the photodetector 18 applied to the terminal In-1 is amplified by the amplifier Am and then applied to the differentiating circuit Dif. The differentiating circuit extracts a high frequency component, that is, a component with a high spatial frequency of the original, from the input signal at a predetermined time constant, and applies it to the integrating circuit int. The integrating circuit is composed of a rectifying diode and a resistive capacitor, and generates a low frequency signal at a level corresponding to the height of the spatial frequency of the original. The low frequency signal is held by the timing signal D shown in FIG.
It is added to the bias circuit of the high-voltage power supply of the developing plate or charger to optimally adjust the image density.

As described above, according to the present invention, the process from the start of preliminary scanning to the end of main scanning for detecting the shading of the original can be performed in one reciprocation of the moving means, and the shading in the central area of the original can be detected two-dimensionally by the photoelectric conversion means. Since the image is read accurately, images can be reproduced quickly and appropriately depending on the document.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of an exposure apparatus according to the present invention, and FIG. 1A is a reflection mirror 1 shown in FIG.
FIG. 2 is a block diagram of the determination circuit J shown in FIG. 1, and FIG. 3 is a diagram showing the detection area of the document detected by the photodetector. , FIG. 4 is a timing waveform diagram, FIG. 5 is a timing signal generation circuit shown in FIG. 4, FIG. 6 is a signal waveform diagram of the block diagram shown in FIG. 2, and FIG. 7 is another implementation of the reflecting mirror 16. 8 is a sectional view showing another embodiment of the photodetector, FIG. 9 is a peripheral circuit diagram of the linear image sensor, FIG. 10 is a block diagram of the linear image sensor, and FIG. 11 is a sectional view showing another embodiment of the photodetector. Timing signal generation circuit diagram, Figure 12 is an output circuit diagram of the linear image sensor, Figure 13 is a timing waveform diagram, Figure 14 is a timing waveform diagram,
5 is a block diagram of another embodiment of the judgment circuit J, and FIG. 16 is a block diagram showing another embodiment of the judgment circuit J. 18...Photodetector, HP...High pass filter, LP...Low pass filter.

Claims (1)

[Scope of Claims] 1. Photoelectric conversion means having a plurality of light-receiving elements and receiving light according to the density of the document by the plurality of light-receiving elements and converting it into an electric signal, which relatively reciprocates between the document and the photoelectric conversion means. a moving means that slit-exposes a document by moving; an extraction means that extracts electrical signals in the arrangement direction of the plurality of light receiving elements from the photoelectric conversion means; after the moving means starts moving in one direction and in the one direction; a first signal output means for outputting a first signal for permitting the extraction of the electric signal for a first predetermined period before the end of the movement of the photoelectric conversion means; after the start of scanning one line by the photoelectric conversion means and before the end of scanning of one line; a second signal output means for outputting a second signal for permitting extraction of the electrical signal for a second predetermined period of time; a control means for processing and optimizing image reproduction conditions according to the processing results; 1. An image reproducing device comprising: image reproducing means for reproducing a document image under standardized image reproducing conditions.