JPS6079372A - Image playback device - Google Patents

Abstract

PURPOSE:To obtain an always adequate image by providing a measuring means which measures optically the characteristics of an original, a moving means which moves relatively the measuring means and the original and a control means which controls the moving means so as to move the same for the purpose of the measuring stage prior to the exposing stage. CONSTITUTION:The image of an original is fed to a reflecting mirror 12 and is projected to a lens 13 and a reflecting mirror 14 by which the image is formed on a photosensitive drum 15. A part of the quantity of the light reflected by a half mirror 16 is conducted to a reflecting mirror 17 to be fed in the direction perpendicular to the moving direction of an original base and the light obtd. via the mirror 17 is condensed a photodetector 18 having the photosensitive wavelength characteristic coinciding with the emission spectrum of a light source for exposing the original and the photosensitive wavelength characteristic of the photosensitive drum. The video signal of the original converted to an electrical signal by the photodetector 18 decides whether the original has many fine characters and lines or has much medium constract in a decision circuit. The copying operation of the original placed on an original plate 10 is accomplished according to the detection of such original content.

Description

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

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, and when the document table moves to a predetermined position,
It is returned to its original position again by means not shown. 1
A document exposure lamp 1 irradiates light onto a document placed on a document table 10 and sends an image of the document to an optical system.

The image of the original is first sent to the reflection mirror 12.

The light whose optical path has been changed by the reflecting mirror 12 passes through the lens 1
3. The image is projected onto the reflecting mirror 14, and is formed onto the photosensitive drum 15 by the reflecting mirror 14 and lens 13.

In order to judge the content of the document, a half mirror 16 placed at a predetermined position on the optical axis between the photosensitive drum 15, the lens 131 and the reflection mirror 14 converts a portion of the amount of reflected light into the direction of movement of the document table. The reflected light sent in the vertical direction is guided to 5-17,
The light obtained through the reflection 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 light source for exposing the original 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 judgment circuit shown in FIG. Determine whether the original has low contrast and many halftones.

Referring to FIG. 2, ITI is an input terminal that receives the output of the photodetector 18, and the output is input to the amplifier A1np. The signal amplified by the amplifier Amp is applied to a bypass filter HP and a low-pass filter LP to separate high-frequency components and low-frequency components included in the signal, and the output of the bypass filter HP is sent to a waveform shaping circuit WF. is input.

The output of the low-pass filter LP is input to the slice circuits 81 and 82 to which the density level signal is input, the output of the slice circuit S2 is applied to one input terminal of the NAND game) NG via the inverter I, and the output of the slice circuit S1 is applied directly to the input terminal of the Nandt 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) fvcl via a gate G1 that is opened by a timing signal applied from an input terminal ITJ. On the other hand, the output of NG (Nando game) is input terminal I
Timing signal applied from T4 and pulse generator PG
is applied to the fv converter fvc2 via the gate circuit G2 to which the output of is applied. Input terminal IT5 has f-v converters fvcl, fvc2 and sample hold SH
This is a timing signal for inputting a signal to.

The outputs of the fv converters fvcl and 1vc2 are input to a differential amplifier. The output of the differential amplifier is input terminal IT5.
A timing signal is input to the sample hold SH. The output of the sample hold SH is passed through a control circuit DC and is used as a control signal indicating the amount of developer attached to the photosensitive drum 15.

In FIG. 1, 19 is a cleaner, and the photosensitive drum 15
Remove toner etc. on top.

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, a reflecting mirror 14, a lens 13
The image exposure on the photosensitive drum 15 is performed by slit exposure together with the AC discharge on the photosensitive drum 15 due to the AC charge bleeding 21.

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

Reference numeral 23 denotes an electrode roller which squeezes the liquid layer of developer on the surface of the drum after development, and is also applied with a bias 'i of +200 cm, which absorbs excess toner on the drum.

24 is a charger that applies corona to the drum and mechanically 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 to the copy paper P by pinching the copy paper P and generating a discharge, thereby transferring the toner on the drum to the copy paper PK.

The output of the determination circuit J is appropriately inputted to the 20% AC charger 21, the developing plate 22, the electrode roller 23, the charger 24, and the charger 25 described above.

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 t1 and stops at timing t4 in response to a position detection signal. Next, at t5, the document table begins to return, and when it returns to its original position, the position detection signal
Stop at 6. In this embodiment, during the forward stroke of s'l-''4, scanning is performed to determine the content of the document, and in the return stroke from t5 to t6, the optical image of the document is exposed to the photosensitive drum.

First, when the document table 10 starts to move in the direction of the arrow A, the contents of the document are reflected by the reflection mirror 12, the lens 13, the reflection mirror 14,
Photodetector 1 via half mirror 16 and reflective mirror 17
8. When detecting the content of a part of a manuscript as shown in Figure 3, in the figure, the ■ direction is the direction of movement of the document, and H is the direction in which the photodetectors are arranged. For example, ■, ■H,
In order to detect the shaded area surrounded by H2, timing signals as shown in B, C, 2, and H in FIG. 4 are generated as shown in FIG.

The rising signal at timing t1 shown in FIG. 4(A) is inverted by an inverter inv, and the one-shot OS 1 is activated by this falling signal. One shot cost 0
81 of 1 (the level holding time is the time from timing t4 until the information on the position of V of the document table 10 is projected on the photodetector 18. When the one shot 081 falls, the one shot 082 is the fourth one) It is activated as shown in FIG.
(It is set to hold the level.

The output of one shot 082 is applied to one shot 083, producing a signal as shown in FIG. 4). Further, the output of one shot 082 is input to AND gate AGI. At the other end of the AND gate AG, the vibration axis 17a of the reflection mirror 17 is connected to the vibration axis 17a of the reflection mirror 17 as shown in FIG.
The movement of the hole in the disc 17b provided in the disk is detected by the photocell 17C which detects the light from the light source 1'7c through the hole.

The time of 084 is the scanning time of one line.

It is assumed that at timing t2, the image content of the original on the original table lO begins to be detected, and for example, a signal shown in (f) of FIG. 6 is obtained between t2 and t3.

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 photodetector 18 converts the incoming data into an electrical signal, amplifies the signal with an amplifier Amp, and inputs it to a bypass filter HP and a low-pass filter LP to distinguish the high and low frequencies of the image. Separate the area. The multi-frequency component obtained through the bypass filter HPi is shaped into a pulse waveform as shown in [F] in Fig. 6 by the waveform shaping circuit WF, and is applied to the gate circuit G1, and input through the terminal IT4 at 1-. Only the signals included in the document content judgment area are extracted according to the timing signal sent to f-
V converter fvcl. f-V converter fvcl
The output is set to O at the falling edge of the timing signal ■ applied to the terminal IT5. The above fV converter fvcl is
The output is applied to a differential amplifier.

On the other hand, the output of the low bass filter LP is the slice circuit S1,
Added to S2. Slice circuits 81 and 82 each have terminals IT2. The input signal is compared with the DC voltage levels ■, ■ (shown in FIG. 6) corresponding to the preset concentration level applied to I'r3. High level ■ is terminal IT
3, and a low level ■ is applied to the terminal IT2. The output of the slice circuit S1 is connected to the input terminal of the NAND game) NG.
The output of the slice circuit S2 is passed through the input circuit I/
It is applied to the other inputs M and H of the gate NG, and the
A signal like NG appears at the output of the NAND game), and this output is connected to the timing signal of the terminal IT4 and the pulse generator P.
G (this frequency is higher than the signal applied to the terminal IT4, and by changing this frequency, the standard for determining the content of the document can be selected) is applied to the gate circuit G2, and a signal as shown in ■ in Fig. 6 is applied to the gate circuit G2. Output. This output is applied to the fV converter fvc2, and a voltage proportional to the input pulse appears on the output as shown in (2) in FIG. The fV converter fvcl is also reset at the falling edge of the signal 0.

The outputs of the f-V converters fvcl and fvC2 are applied to a differential amplifier, and the above-mentioned voltage difference is stored in the sample-and-hold circuit SH by the timing signal [phase] applied from the terminal IT5. In response to the contents stored in the sample and hold circuit 8H, the bias voltage applied to the polarization roller 23 via the control circuit DC changes, and the developing plate 2
2, the amount of toner attached to the photosensitive drum 15 is controlled.

Note that the charger 20 is used to sew the toner to adhere to the photosensitive drum 15.
．． AC charger 21, developing plate 22, charger 24.25. Since the output of the sample hold circuit SH described above can be controlled by the control circuit DC-
It may be placed in 1-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 drive means (not shown), and during this return movement, the original document is placed on the JfA table 10. The copying operation is performed based on the above-mentioned detection of document contents.

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 reflective mirror is used, where 30 is a reflective mirror fixed with a support fitting 31, and a shaft 32.
It has shafts 33 and 34 so that it can rotate freely.

34 is fixed to an ordinary bearing, but the other shaft 33 is
A spring 35 is fixed to a bearing 37 fixed to a central shaft of a rotary solenoid 36 via a spring such as a torsion spring. Rotating shaft 33 and bearing 37
A spring 35 is provided with a pawl to prevent it from rotating, which reduces the load on the rotary lean solenoid 36 when the rotary solenoid is energized and when it hits the return members 38 and 39 caused by the return spring. 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.

When the rotary solenoid 36 is energized by a predetermined timing signal (θ in FIG. 4) for determining the content of the document, it is fixed to the holding member 38, and the document irradiation light is directed to the mirror 3o.
The light is reflected in the B direction by the light beam, and is focused on the reflecting mirror 17 or the photodetecting element 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 mirror 30 is stopped by the return spring.
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 the photodetector 1 used in the embodiment shown in FIG.
8 as a self-scanning linear image sensor 18a.
(one-dimensional), and mechanically vibrating parts such as the reflecting mirror 17 are removed. To further explain, the 8th
In the illustrated embodiment, the vertical scanning of the original is performed by mechanical movement of the original table, and the horizontal scanning of the original is performed by the incremental scanning of the image sensor.
7 can be omitted.

FIG. 9 is a block diagram of scanning and signal processing of the image sensor, which will be explained according to the time chart of FIG. 14. 41 is a 1728-element linear image sensor ('C0D121H manufactured by Fairchild), a block diagram of which 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 (2) of a constant frequency set from a spatial frequency that satisfies the resolution required for document determination.

The timing generator shown in Fig. 11 is a 4-bit counter (hexadecimal counter) Cc (Fairchild #9316PC) and a flip 70-tube FF (J-type) as shown in the figure.
, ANDGATE AG.

Timing signal GIA I j'19 * 912 M, G2 by combining NG) NG and inverter INV
B, GuXk.

szB, F, #XB, 8YNC%8WgF
Make SP 8YNC.

The output shown in FIG. 12 includes a transistor Q, resistors 1 to R16, and a diode C as shown in the figure.

It consists of capacitors 01 to C9 and an operational amplifier OA.

The control output circuit 44 generates various timing signals (shown in FIG. 13) necessary for scanning the linear image sensor 41 from the clock signal and applies them to the linear image sensor. Scan synchronization signal (5WEEP 5YNC) @t
This is the period from b'7 to t8.The light and excitation'-load of each element of the near image sensor 41 is transferred in parallel to the internal shift register, and reading from the shift register is started from b'8 in synchronization with the signal O. , a DC-regenerated output signal (2) is obtained at the output V-out of the control output circuit 42.

In order to extract and hold the amplitude component of the output signal, the signal (2) is delayed for a certain period of time by a monostable circuit, converted into a narrow pulse (2) by the shaping circuit 45, and then added to the sample and hold circuit 46 as a sampling signal, and the output signal is ■A stepped signal■
Convert to The output (2) is smoothed by a low-pass filter 47 by removing the weight of the sampling signal (2), and is then applied to the input terminal ITI in FIG. 2 via a terminal 48. The scanning synchronizing signal is inverted by an inverting circuit 49 and then sent to the terminal IT in FIG. 2 as a horizontal scanning gate signal.
Added to J.

If a linear image sensor is used as described above, it is possible to eliminate a configuration that vibrates the reflection mirror. Note that a two-dimensional (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 the gate circuit ()1. The counters CNT1 . The contents of CNT2 are applied to the subtractor Sub, and the contents of counters C, NT1 . The difference in CNT2 is obtained. The value of the difference is stored in a latch circuit, and D-
It is converted into an analog value by the A converter C0NV, and controls the bias voltage of the electrode roller 23 as described above.

Note that the counters CNTl and CNT2 are initialized as follows. For example, if the content of the original is only high-frequency components, 100 pulses are counted, and the content of the original is only low-frequency components, and 100 pulses are stored. The counter CNT1 that counts the pulses of the frequency component is initially set to a value of 100, and the other counter CNT2 is set to a value of 0. The counters CNTl and 2 count up from that value, and when both counters stop at 50 up, the subtracter 8ub outputs the difference 100, and the control circuit uses a bias voltage between the high and low ranges. to appear.

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 A m and then applied to the differentiating circuit Dif. The differentiating circuit extracts a high frequency component, that is, a component having 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 whose level corresponds to the height of the spatial frequency of the original. Low frequency No. 3 is the timing signal applied to the terminals Ir1-2K by the sample and hold circuit SHC, and after being held by 0 in FIG. 4, the control circuit D
The signal is amplified by C and applied to the bias circuit of the high-voltage power source of the electrode roller 23, developing plate, or charger to optimally adjust the image density.

[Brief explanation of the drawing]

&(Figure 1 is a sectional view showing an embodiment of the exposure apparatus according to the present invention, Figure 1 is a layout diagram showing the relationship between the reflecting mirror 17 and the photodetector 18 shown in Figure 1, and Figure 2 is a cross-sectional view showing an embodiment of the exposure apparatus according to the present invention. 1 is a block diagram of the judgment circuit J, FIG. 3 is a diagram showing the detection area of a document detected by a photodetector, FIG. 4 is a timing waveform diagram, and FIG. 5 is a diagram showing the timing signal generation shown in FIG. 4. 6 is a signal waveform diagram of the block diagram shown in FIG. 2, FIG. 7 is a perspective view showing another embodiment of the reflecting mirror 16, and FIG. 8 is a cross section showing another embodiment of the photodetector. Figure 9 is a peripheral circuit diagram of the linear image sensor, Figure 10 is a block diagram of the linear image sensor, Figure 11 is a timing signal generation circuit diagram, Figure 12 is an output circuit diagram of the linear image sensor,
13 is a timing waveform diagram, FIG. 14 is a timing waveform diagram, FIG. 15 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......Bypass filter LP...
Old... Low-pass filter Figure 4. -Sara Tsui 111111 Procedure Neichi Seishi (self-motivated) May 28, 1980 1. Indication of the case Patent application filed on April 28, 1989 (1) 2. Invention Name: Image forming device P3, relation to Nagisa matter Patent applicant address: 3-30-2 Shimomaruko, Ota-ku, Tokyo Name (100
) Canon Co., Ltd. Representative Name Ryu Kaku 3 Division 4, Agent Address 3-30-25 Shimomaruko, Ota-ku, Tokyo 1413,
Specification subject to amendment 6, Contents of amendment (1) The following is inserted after '' in the 12th line of the first page of the specification. Conventionally, in copying machines, etc., in order to obtain a proper image, the operator must set the image forming conditions such as the developing bias voltage, exposure amount, and charge amount optimally each time the document is copied, depending on the type of document. This caused trouble for the operator. The present invention has been made in view of the above points, and an object of the present invention is to provide an image forming apparatus & which has a simple configuration and is capable of always obtaining a proper image regardless of the type of document. That is, the present invention provides a measuring means for optically measuring the characteristics of an original; a moving means for moving the measuring means and the original in a harmonious manner; The present invention provides an image forming apparatus having a control means for controlling the moving means to move the moving means for a measurement process. (2) Insert the following after the 7th line of page 23. As described above, according to the present invention, it is possible to automatically obtain an image with the optimum density according to the content of the original, whereas in the past, the image density was adjusted by looking at the completed copy images one by one according to the content of the original. It becomes possible. Written amendment (method) % formula % 2. Name of the invention Image forming device 3. Relationship with the person making the amendment Patent applicant address 3-30-2 Shimomaruko, Ota-ku, Tokyo Name (100
)Representative of Canon Co., Ltd. Ryu Kaku 3 Part 4, Agent address: 3-30725 Shimomaruko, Ota-ku, Tokyo 148, Date of amendment order: September 25, 1980 (shipment date) 6. Specification subject to amendment and Drawing 7, contents of correction

Claims (1)

[Claims] a measuring means for optically measuring characteristics of a document; a moving means for relatively moving the measuring means and the document; and a movement for the measuring step by the measuring means before the document is moved for the exposure step. and a control means for controlling the moving means to perform the following.