JPH09139844A - Digital copying machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a dust or the like as an image noise and to eliminate the noise from the image. SOLUTION: The copying machine has plural image read means to read an original while being carried and output signals from the image read means are converted into digital image signals. Output signals DA1 from a 1st read image sensor reading the original image while carrying the original are delayed (730) and the delayed signals are compared (740) with outputs DB1 of 2nd (plural read image sensors and the image noise is detected from the result to detect the dust on the original as the image noise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital copying machine, and more particularly to a copying machine and a facsimile using an original reading device for reading an original as a digital image signal while conveying the original.

[0002]

2. Description of the Related Art Conventionally, in a copying machine or a facsimile machine in which a manuscript reading element is fixed and a manuscript sheet is moved, dust adhering to the manuscript stains the contact glass of the manuscript table or re-adheres to read the dirt. Since it was copied as it was, the received image contained vertical lines that were not in the original, causing complaints. This eliminates the floating of the original, and since the conveyance gap at the position where the original is just read on the contact glass is the narrowest, dust and eraser debris adhering to the original at that position catches on the contact glass during conveyance. Becomes easier,
As a result, when the contact glass is stained or when a digital image is read by using a one-dimensional image sensor to read an image as minute pixels, the contact glass stays at the reading position temporarily even if it is not dirty. This is because even if it is used alone, it becomes a vertical streak.

For this reason, in a machine that handles a relatively small size (up to about A3), most of the copying machines are of a document bed type in which the document is fixed and the reading device moves (in this case, dust is assumed. But even if it is on the manuscript, dust is simply read as spots at that location and does not appear as vertical stripes like the manuscript sheet moving type). For high-end machines, fixed-type manuscripts are also increasing in the case of facsimiles, but some machines aiming for small size and low cost still have moving manuscripts and fixed reading devices.

On the other hand, in the case of a wide-width machine that handles large-sized originals A0 and A1, it was not possible to install a full-size original table in terms of machine size and cost. Also, because of the advantage of being able to make a long copy, it was unavoidable to use a moving document type.

Further, in such an original moving type machine,
In order to make multiple copies from one original, it has an image memory so that the original can be read once, stored in the memory, and then read many times. Dust appears as vertical stripes on all copies, and, worse, most large-sized originals have many vertical or horizontal straight lines in the drawings, and vertical stripes due to dust and vertical stripes due to dust. It was often indistinguishable from

In Japanese Utility Model Application Laid-Open No. 59-38451, it is proposed to carry out an antistatic treatment in order to prevent dust and smoke particles from adhering to the contact glass. Further, Japanese Utility Model Application Laid-Open No. 60-193747 proposes to provide a cleaner for cleaning the surface of the document conveying roller facing the image reading head.

[0007]

[Problems to be Solved by the Invention]
No. 9-38451 and Japanese Utility Model Laid-Open No. 60-193747, a contact glass is provided with a cleaning member for preventing the contact glass from becoming dirty and for cleaning a dirty conveying roller. There is no mention of defects or measures.

[0008]

According to a first aspect of the invention, means for converting an image of a document into a density signal by using an image reading means, and a density signal converted by the converting means into a digital image signal. In a digital copying machine including a conversion unit and an image creation unit that writes the digital image signal converted by the conversion unit onto a photoconductor, a conveyance unit that conveys a sheet-shaped document and a plurality of document reading units that convey the document being conveyed. Image reading means, converting means for converting an output signal from the image reading means into a digital image signal, and delay means for delaying an output signal from the converting means,
A comparison means for comparing a plurality of digital image signals, and a detection means for detecting image noise,
Therefore, the output signal of the first image sensor for reading, which reads the image of the original while conveying the original, is delayed,
The image noise is detected based on the result of comparison with the outputs of a plurality of image sensors for reading, and dust on the document is detected as image noise.

According to a second aspect of the present invention, means for converting an image of a document into a density signal by using image reading means, conversion means for converting the density signal converted by the conversion means into a digital image signal, and the conversion means. In a digital copying machine comprising an image creating means for writing the digital image signal converted by the means on a photoconductor, a conveying means for conveying a sheet-like document, a plurality of image reading means for reading the document being conveyed, and Conversion means for converting the output signal from the image reading means into a digital image signal, delay means for delaying the output signal from the conversion means, comparison means for comparing a plurality of digital image signals, and detection for detecting image noise Means and a display means for displaying the detected noise. A device for displaying as "contamination detection" on sharpened, the operator is obtained as seen vertical streak stains without each time checked later copied image.

According to the invention of claim 3, in the invention of claim 2, when the image noise is detected from the original image read by the means for detecting the image noise, the detected noise is displayed by the means for displaying. As a feature, when image noise is detected during copying, the operator can interrupt the copy at any time to remove dust or dirt on the original or contact glass (in the case of multiple copies, the image once read is stored in the memory. Since all copies have vertical stripes because they are stored in and read many times), or in particular, it is possible to judge whether to check the image noise on the ejected copy paper without interruption.

According to a fourth aspect of the invention, means for converting an image of an original into a density signal by using an image reading means, means for converting the density signal converted by the means into a digital image signal, and conversion by the means. In a digital copying machine including an image creating unit that writes the generated digital image signal on a photoconductor, a conveying unit that conveys a sheet-shaped document, a plurality of image reading units that read the document being conveyed, and the image reading unit A conversion means for converting the output signal of the above into a digital image signal, a delay means for delaying the output signal from the preceding conversion stage, a comparison means for comparing a plurality of digital image signals, and a detection means for detecting image noise, And a noise removing unit for removing the detected image noise from the original image. By providing, in which to be able to remove dust on the original document as image noise.

According to a fifth aspect of the invention, means for converting an image of an original into a density signal by using an image reading means, means for converting the density signal converted by the means into a digital image signal, and conversion by the means. In a digital copying machine including an image creating unit that writes the generated digital image signal on a photoconductor, a conveying unit that conveys a sheet-shaped document, a plurality of image reading units that read the document being conveyed, and the image reading unit A conversion means for converting the output signal of the above into a digital image signal, a delay means for delaying the output signal from the preceding conversion stage, a comparison means for comparing a plurality of digital image signals, and a detection means for detecting image noise, The invention according to claim 4 is characterized in that a removing means for removing image noise and a switching means for switching the image signal are provided. By further providing an image signal switching circuit and providing a circuit for switching between the output signal of the first image sensor and the output signal from the noise removing circuit, either one or both can be selectively used, and either one is abnormal. Even if there is such a problem, one of the image sensors can read the original image without any trouble.

[0013]

1 is a diagram showing an outline of a digital copying machine to which the invention described in claims 1 to 3 is applied. This copying machine is a document reading device 100 as a reading means for reading a document. An image information storage device 300 as a storage unit for storing the read document information, a copying device 200 for executing a series of processes for copying the stored information on a transfer paper, and a system control device 302 for controlling these.
This system control device is composed of an operating device 600 as an operating means for performing a key input.

FIG. 2 is a schematic view of the document reading apparatus 100.
In the figure, 2 is a document conveyance roller, 3 is a paper feed drive roller, 4 is a paper ejection drive roller, 5 is contact glass, 6 is a paper ejection tray,
Reference numeral 7 is a fluorescent lamp, 8 is a lens, and 9 is a CCD. These operations will be described in detail in FIG. 5 described later.

FIG. 3 is a diagram for explaining the configuration of the copying apparatus 200. In the figure, 10 is a charging device, which is the photosensitive drum 1.
7 is a scorotron charger with a grid for uniformly charging 7 to -850V. 11 is a polygon mirror that scans the laser light emitted from the laser diode, 12 is a surface tilt correction lens for the polygon mirror,
Reference numeral 13 is an fθ lens, and 14 to 16 are first to third mirrors. Laser light emitted from a laser diode (not shown) rotates in a direction perpendicular to the rotation direction of the photosensitive drum 17, that is, a direction along the drum axis, by the rotation of the polygon mirror fixed to the polygon motor 18 and the rotation shaft 19. To be scanned.

When the photosensitive drum is irradiated with laser light based on digital image information, the charges on the surface of the photosensitive drum flow to the ground of the drum 17 and disappear due to a photoconductive phenomenon. Here, the part where the original density is low (the binarized signal is the non-recording level)
Turns on the laser. As a result, the laser beam non-irradiated portion of the photosensitive drum is set to a potential of −850V and the irradiated portion is set to −10V.
The potential becomes about 0 V, and an electrostatic latent image corresponding to the shade of the image is formed. This electrostatic latent image is developed by the developing unit 20. The toner in the developing unit is negatively charged by agitation and a bias of −600 V is applied, so that the toner adheres only to the laser light irradiation portion.

On the other hand, the recording paper is selected from the three paper feed trays 21 and fed by the feed roller 22,
It is cut into a predetermined length by the cutter 23, conveyed by the paper feed roller 24, passes below the photosensitive drum 17, and at this time, the transfer charger 25 transfers the toner image onto the recording paper. Next, the recording paper is separated from the photosensitive drum 17 by the separation charger 26, conveyed by the conveyor belt 27 and placed in the fixing unit 28, where the toner is fixed on the recording paper. The recording paper on which the toner has been fixed is ejected to the outside of the apparatus by the conveyance roller 29.

The operation device 600 comprises an operation panel 602 and a control circuit 601. On the operation panel 602, as shown in FIG. 4, keys for designating various functions, for example, a paper size key 611, a ten key 612, Start key 6
13, stop key 614, density adjustment key 615, image quality adjustment key 616, scaling key 617, mode clear key 6
18, number of copies 619, magnification 620, number of sets 6
21 and the like, a document insertable display 62
2. A dirt check display 623 and the like are provided. Control circuit 60
1 receives the key input signal of the operation panel 602 and controls the display, but its detailed circuit is omitted.

Next, referring to FIG. 5, the document reading device 100
The document feeding mechanism will be described. When the original 50 is inserted from the original table 51 and the original size is detected by the size detection sensor 52, the pinch solenoid 61 is turned off.
As a result of N, the lifter 59 rotates and rises around the support shaft 60, lifts the inlet driven roller shaft 58, releases the pressure of the inlet driven roller 55, and the original 50 can be inserted further into the back. At this time, the fluorescent lamp 7 is turned on at the same time to prepare for reading the original.

When the original 50 is further inserted, the original 50
The tip is abutted against the entrance gate claw 63, and the insertion sensor 5
When 3 is turned on, the registration drive roller 3 and the paper discharge drive roller 4 are driven by a drive mote and drive system (not shown), the pinch solenoid 61 is turned off again, pressure is applied to the inlet driven roller 55, and the inlet gate solenoid 64 is turned on.
N, the entrance gate claw 63 is opened, the insertion clutch (not shown) is turned on, the entrance drive roller 2 is driven, and the conveyance of the document is started.

The original 50 is conveyed by the registration driving roller 3 and the registration driven roller 56, and the registration sensor 54.
Through the contact glass 5 which is flush with the original table 51, is brought into close contact with the glass surface by the backup roller 62 arranged at a position facing the contact glass 5, and is illuminated by the fluorescent lamp 7. The reflected light is imaged and read by the lens 8 on an image pickup device including a CCD 9. Here, the registration sensor 54 is
The timing for starting and ending the image reading, the length of the original and the jam of the original are detected, and the timing for turning off the drive motor and the fluorescent lamp is set. In addition, the backup roller 62
Has a minute gap (0.1 to 0.2 mm) from the surface of the contact glass 5 and is driven by the registration driven roller 56 through a timing belt (not shown) so that it does not become a load of document conveyance. ing. The read original 50 is ejected to the paper ejection tray 6 by the paper ejection drive roller 4 and the paper ejection driven roller 57.

Next, the reading element (CCD) 9 will be described with reference to FIG.
Will be described. CCD 9 used in this embodiment
In this package, the one-dimensional array of 14 μm × 14 μm photodiodes from 1 pixel to n pixels is
Three rows are arranged at intervals of 68 μm (for 12 lines).

Here, two one-dimensional CCs located at both ends
If D is used as the first CCD 9a and the second CCD 9b, there is a distance of 336 μm (24 lines) between the two CCDs, which is 1524 μm at the original position before being condensed by the lens 8. This corresponds to a distance of (about 1.5 mm). That is, the first CCD 9a and the second CCD 9
In the case of b, the position of 1524 μm away from the original is read at the same time. When the first CCD 9a precedes the reading in the document conveying direction, the data read by the second CCD 9b is the data read by the first CCD 9a before the document is conveyed by 1524 μm. It is configured to match.

Although the two one-dimensional CCDs located at both ends are used here, either one of the CCDs may be used, or the central CCD 9n may be used to convey the original document and the image to be detected. It is also possible to switch between the use of the first CCD 9a and the middle CCD or the use of the first CCD 9a and the second CCD 9b according to the magnitude of noise.

Next, the principle of image noise detection will be described with reference to FIG. FIG. 7 is a side view showing how the document is conveyed. Focusing on the point A on the document being conveyed by the registration drive roller 3 and the paper ejection drive roller 4, the point A is the contact glass 5 and the backup. When it is conveyed to the reading position sandwiched by the rollers 62, the first
Reading is performed by the CCD 9a. However, if there is dust or dirt on the optical path connecting the document, the lens 8 and the first CCD 9a, the optical path will be blocked. If the reading element is only the first CCD 9a, dust and dirt are always shielded from light during document transportation, so image noise such as black lines appearing in the transport direction regardless of the presence or absence of image information. To do.

Next, when the point A is transported by 1524 μm,
Reading is performed by the second CCD 9b. This time, since there is no light-shielding object such as dust or dirt between the document, the lens 8 and the second CCD 9b, the image information of the document can be read correctly. 1524 data read by the first CCD 9a
When compared with the read data of the second CCD 9b by delaying the data only by the amount corresponding to the conveyance of μm, the data is at the same position on the document, so the regular image information is the same, but the image noise such as dust, dirt, etc. It often appears only in one or the other data. The present invention intends to detect image noise by utilizing this characteristic. In this embodiment, the reading positions of the first CCD 9a and the second CCD 9b are provided at a distance of 1524 μm on the document surface, so that dust and dirt less than that can be detected.

Next, the signal processing after being read by the CCD 9 will be described with reference to FIG. The original images formed on the first CCD 9a and the second CCD 9b are converted into analog electric signals, which are output in synchronization with the clocks output from the synchronization control circuit 105, respectively, and image amplification circuits (AMP) 101a and 101b. Is amplified by. The amplified analog electric signal is converted into a multilevel digital image signal by A / D conversion (analog / digital conversion) circuits 102a and 102b and sent to the image noise detection circuit. In the image noise detection circuit 110, the first C read previously
After the data of the CD 9a is delayed so that the data read by the second CCD 9b and the data at the same position on the original document are compared, dust and dirt on the conveyed original document are detected by comparing the data.

This data is used by the shading correction circuit 10.
3 has a variation in sensitivity of CCD 9 and a fluorescent lamp 7 as a light source.
The unevenness of the light amount and the error of the light amount distribution of the lens 8 are corrected, and then the image processing circuit 104 performs various image processing such as MTF correction and binarization. The synchronization control circuit 105 has a control signal as shown in FIG. 9 and is synchronized with the original. A signal LSYNC for synchronizing in the main scanning direction,
Signal LGAT indicating the maximum effective reading area in the main scanning direction
E, a synchronous clock for each pixel, and a signal FGATE indicating a reading effective area in the sub-scanning direction that is output upon receiving a signal from the reading control circuit 106 that controls the sequence of the entire reading device are generated.

Next, the image noise detection circuit 110 will be described. As shown in FIG. 10, the image noise detection circuit 100 performs the binarization processing A710 and B720 for binarizing the outputs of the CCDs 9a and 9b, respectively, and the binarization processing A710 for binarizing the phase difference between the CCDs 9a and 9b. Data delay 730 for delaying binarized image data
And the image data delayed by the data delay 730 and 2
It is composed of a noise detector 740 which compares the image data binarized by the binarization process B720 and detects noise on the read image data. Hereinafter, each part will be described in more detail.

First, the binarization processing A710 and B720 will be described. Binarization processing A710 and B720
11 are comparators 711 and 721, respectively, as shown in FIG.
It consists of. The operation will be described below with reference to FIG. At the input terminals A of the comparators 711 and 721,
The image data DA1 and DB1 converted into multi-values by the A / D converters 102a and 102b are input. Then, when threshold data for binarization is set and input to the input terminal B by the read control circuit 106, the image data D is output to the output terminals A> B of the comparators 711 and 721.
Depending on the magnitude relation between A1 and DB1 and the threshold data, if image data> threshold data, high level image data ≦ threshold data, low level signals DA2 and DB2 are output.

Here, the binarization is performed by delaying one of the outputs of the two CCDs 9a and 9b in order to detect image noise due to dust or the like adhering to the original and selected. This is to reduce the scale of the delay circuit because the timing is compared with the other output. The threshold data is set relatively low, and is set to 32/256 in this embodiment. This is generally output to an image and the problem is
This is because black streaks are often output due to dust on the white part of the document.

FIG. 13 is a diagram for explaining an example of the processing when it is recognized as dust, and when it is recognized as dust,
As shown in FIG. 13, in noise removal 750 (described later), a process of masking black data and replacing it with white data is performed. Therefore, if binarization is performed at a high density, and if the image density is close to the threshold data level, even if the same image is read, at the multi-value reading level, the lower 1 to 2 bits of the lower 8 bits are read. May cause variations in reading and the data may not match, so that the binarization results in the binarization processing A710 and B720 may be different. At this time, since it is determined that the density difference is caused by dust and the data is masked and replaced with white, conversely, a defect that white spots occur occurs. However, if the image is binarized at a low image density, even if the data is mistakenly recognized and the data is masked by mistake, the original image density is low and the white spots are inconspicuous.

Next, the data delay 730 will be described. The data delay 730, as shown in FIG. 14, includes a first-in-first-out (FIFO) memory 7
31 to 733. The operation will be described below with reference to FIG. Input terminal 10 of FIFO memory 731
Is input with the image data DA2 binarized by the binarization processing A710. FIFO memory 731-733
Since the inversion signal * LSYNC of LSYNC is input to the write / reset terminal RSTW and the read / reset terminal RSTR, and CLK is input to the line clock terminal WCK and the read clock terminal RCK, * L
FIFO memory 731-when SYNC is at low level
The write / read address inside 733 is reset, and read / write is performed from the beginning in synchronization with CLK.

Therefore, LSYNC is output to the output terminal 00.
The image data DA2 input to the input terminal 10 is output with a delay of one synchronization. Then, since this output is further input to the next input terminal 11, the image data DA2 appears at the output terminal 02 with a delay of two times of LSYNC synchronization, and thereafter by the same delay, the 07 output of the FIFO memory 733 outputs the LSYNC DA2 appears with a delay of 24 synchronizations.
Since the timing shift of the CCDs 9a and 9b is 24 lines (24 synchronizations of LSYNC), the image data DA
3 is the image data D binarized by the binarization process B720
This means that the phase is matched with B2.

Next, the noise detection 740 will be described. As shown in FIG. 16, the noise detection 740 includes an exclusive OR gate (EX-OR) 741 and an inverter gate (INV) 742. Hereinafter, description will be made with reference to FIG. The noise detection 740 determines the presence / absence of noise due to dust or the like on the image depending on whether the image data read by the two CCDs 9a and 9b match. The image data DB2 binarized by the binarization process B720 is input to one input of the EX-OR 741 and the image data binarized by the binarization process A710 in the data delay 730 is input to the other input. Image data DA3, which is delayed from DA2 and is in phase with DB2, is input.

Therefore, unless dust or the like attached to the original is conveyed and stays on the contact glass 66 again and the dust is read, the outputs of the two CCDs 9a and 9b are different from each other. Since they should match, a high level signal is output to the output terminal if normal. On the contrary, when there is dust or the like, since the outputs are different, DA3 and DB2 do not match and a low level is output, so that the presence or absence of dust can be detected by this output signal. Further, since this signal is input to the INV 742 and inverted, the noise detection signal Dn becomes a high level signal if normal, and a low level signal if abnormal. In this way, the image noise detection circuit 11
The noise detection signal Dn obtained at 0 is the read control circuit 10
6. Operation device 600 via system control device 302
The dirt detection display 623 on the operation panel is turned on.

Next, the noise removal 750 will be described with reference to FIG. The noise removal 750 is composed of AND gates 751 to 758 as shown in FIG. The operation will be described below with reference to FIG. In the noise removal 750, the image data DB1 is masked based on the noise signal Dn detected by the noise detection 740, and noise due to dust or the like appearing on the image is removed. That is, when the noise signal 740 determines that the noise signal is normal, the noise signal Dn becomes a false level, and this signal is AND7.
51 to 758, the image data DB1 input to the other input terminal is A
It is output to the output terminals of the ND gates 751 to 758. On the contrary, when the noise detection 740 determines that the noise is abnormal due to dust or the like, the noise signal Dn becomes low kevel.
The outputs of the AND gates 751 to 758 are at a low level (= 0: white) regardless of the inputs. Therefore, the black stripes due to dust or the like are erased and the image data DB3 is output.

Finally, referring to FIG. 20, the image switching 76
0 will be described. The image switching 760 is composed of a selector 761 as shown in FIG. The image data DA1 read by the CCD 9a is input to the input A of the selector 761, and the noise removal 75 is input to the input B.
The image data DB3 from which noise has been removed by 0 is input. The read control circuit 106 is connected to the selection terminal S.
Since the image switching IM-SEL is set and input by, the image data DA is set according to the level of IM-SEL.
Either 1 or DB3 is selected. And usually,
IM-SEL is set to the low level, and the noise-removed image data DB3 is selected and output to the output terminal. However, the CCD 9b fails, or part of the image noise removal circuit 110 If the output is abnormal due to failure due to noise removal processing, the image data DA1 read by the CCD 9a
It is possible to improve the reliability of the system by outputting using. Then, the printer 200 forms an image based on the image data D.

[0039]

According to the invention of claim 1, means for converting an image of an original into a density signal using the image reading means, and conversion means for converting the density signal converted by the converting means into a digital image signal, In a digital copying machine comprising an image creating means for writing a digital image signal converted by the converting means on a photoconductor, a conveying means for conveying a sheet-like document, and a plurality of image reading means for reading the document being conveyed. A conversion means for converting the output signal from the image reading means into a digital image signal, a delay means for delaying the output signal from the conversion means, a comparison means for comparing a plurality of digital image signals, and image noise detection And a detection unit for detecting the output signal of the first image sensor for reading the original image while conveying the original. Cast, as compared to the output of the image sensor for reading the second (s), the result, it is possible to detect the dust on a document as image noise.

According to a second aspect of the invention, means for converting the image of the original into a density signal by using the image reading means, conversion means for converting the density signal converted by the conversion means into a digital image signal, and the conversion means. In a digital copying machine comprising an image creating means for writing the digital image signal converted by the means on a photoconductor, a conveying means for conveying a sheet-like document, a plurality of image reading means for reading the document being conveyed, and Conversion means for converting the output signal from the image reading means into a digital image signal, delay means for delaying the output signal from the conversion means, comparison means for comparing a plurality of digital image signals, and detection for detecting image noise Means and a display means for displaying the detected noise are provided. Can be displayed as a "dirt detection" of the above operator is vertical streak of dirt can be seen without one by one check at a later copied image.

According to the invention of claim 3, in the invention of claim 2, when the image noise is detected from the original image read by the means for detecting the image noise, the detected noise is displayed by the means for displaying. Therefore, when image noise is detected during copying, the operator can interrupt copying at any time to remove dust or dirt on the original or contact glass (in the case of multiple copies, the image once read is stored in the memory. Because I read it again,
All copies can have vertical streaks), or
In particular, it is possible to judge whether to check the image noise on the ejected copy paper without interruption.

According to a fourth aspect of the invention, means for converting an image of an original into a density signal by using an image reading means, means for converting the density signal converted by the means into a digital image signal, and conversion by the means. In a digital copying machine including an image creating unit that writes the generated digital image signal on a photoconductor, a conveying unit that conveys a sheet-shaped document, a plurality of image reading units that read the document being conveyed, and the image reading unit A conversion means for converting the output signal of the above into a digital image signal, a delay means for delaying the output signal from the preceding conversion stage, a comparison means for comparing a plurality of digital image signals, and a detection means for detecting image noise, Since it is provided with a removing means for removing image noise, a noise removing circuit for removing the detected image noise from the original image is provided. It allows removal of dust on the original as image noise.

According to a fifth aspect of the invention, means for converting an image of an original into a density signal by using an image reading means, means for converting the density signal converted by the means into a digital image signal, and conversion by the means. In a digital copying machine including an image creating unit that writes the generated digital image signal on a photoconductor, a conveying unit that conveys a sheet-shaped document, a plurality of image reading units that read the document being conveyed, and the image reading unit A conversion means for converting the output signal of the above into a digital image signal, a delay means for delaying the output signal from the preceding conversion stage, a comparison means for comparing a plurality of digital image signals, and a detection means for detecting image noise, Since the removing means for removing the image noise and the switching means for switching the image signal are provided, in addition to the invention of claim 4, An image signal switching circuit is provided,
By providing a circuit that switches between the output signal of the first image sensor and the output signal from the noise removal circuit, either one or both can be selectively used, and even if there is an abnormality in either one, one of the image sensors will not interfere. The original image can be read without it.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an outline of a digital copying machine to which the present invention is applied.

FIG. 2 is a diagram for explaining the outline of the document reading apparatus shown in FIG.

FIG. 3 is a diagram for explaining the outline of the copying apparatus shown in FIG.

FIG. 4 is a diagram showing details of an operation panel shown in FIG.

FIG. 5 is a diagram for explaining details of the document reading apparatus shown in FIG.

FIG. 6 is a diagram illustrating details of a document reading element (CCD).

FIG. 7 is a diagram for explaining the principle of image noise detection.

FIG. 8 is a diagram for explaining signal processing after being read by a document reading element.

FIG. 9 is a diagram showing control signals of a synchronization control circuit.

FIG. 10 is a diagram for explaining an example of an image noise detection circuit.

FIG. 11 is a diagram for explaining an example of a binarization processing circuit.

FIG. 12 is a time chart for explaining the operation of the binarization processing circuit.

FIG. 13 is a diagram for explaining an example of an image noise removing circuit.

FIG. 14 is a diagram for explaining an example of a data delay circuit.

FIG. 15 is a time chart for explaining the operation of the data delay circuit.

FIG. 16 is a diagram for explaining details of a noise detection circuit.

FIG. 17 is a time chart for explaining the operation of the noise detection circuit shown in FIG.

FIG. 18 is a diagram for explaining details of a noise removal circuit.

FIG. 19 is a time chart for explaining the operation of the noise removal circuit shown in FIG.

FIG. 20 is a diagram illustrating an example of an image switching circuit.

[Explanation of symbols]

9 ... CCD, 100 ... Original reading device, 104 ... Image processing circuit, 105 ... Synchronous control circuit, 106 ... Reading control circuit,
110 ... Image noise detection circuit, 200 ... Copier, 30
0 ... Image information storage device, 201 ... Image memory, 302 ...
System control device, 500 ... Writing device, 600 ... Operating device, 602 ... Operating panel, 710, 720 ... Binary processing circuit, 730 ... Data delay circuit, 740 ... Noise detection circuit, 750 ... Noise removal circuit, 760 ... Image Switching circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuhiko Okada 713 Tsuruga Sone, Yashio City, Saitama Prefecture Ricoh Unitechno Co., Ltd.

Claims (5)

[Claims] 1. A means for converting an image of a document into a density signal using an image reading means, a converting means for converting the density signal converted by the converting means into a digital image signal, and a converting means for converting the density signal. In a digital copying machine comprising an image creating means for writing a digital image signal on a photoconductor, a conveying means for conveying a sheet-like original, a plurality of image reading means for reading the original being conveyed, and a plurality of image reading means The image forming apparatus includes: a converting unit that converts the output signal into a digital image signal; a delay unit that delays the output signal from the converting unit; a comparing unit that compares a plurality of digital image signals; and a detecting unit that detects image noise. A digital copying machine characterized in that 2. A means for converting an image of a document into a density signal by using an image reading means, a conversion means for converting the density signal converted by the conversion means into a digital image signal, and a conversion means for converting the density signal. In a digital copying machine comprising an image creating means for writing a digital image signal on a photoconductor, a conveying means for conveying a sheet-like original, a plurality of image reading means for reading the original being conveyed, and a plurality of image reading means Conversion means for converting the output signal into a digital image signal; delay means for delaying the output signal from the conversion means; comparison means for comparing a plurality of digital image signals; detection means for detecting image noise; And a display means for displaying noise. 3. The digital according to claim 2, wherein when the image noise is detected from the original image read by the image noise detecting means, the detected noise is displayed by the display means. Copier. 4. A means for converting an image of a document into a density signal by using an image reading means, a means for converting the density signal converted by the means into a digital image signal, and a digital image signal converted by the means. In a digital copying machine including image forming means for writing a sheet on a photoconductor, a conveying means for conveying a sheet-like document, a plurality of image reading means for reading the document being conveyed, and a digital output signal from the image reading means. Conversion means for converting into an image signal, delay means for delaying the output signal from the previous conversion stage, comparison means for comparing a plurality of digital image signals, detection means for detecting image noise, and image noise removal A digital copying machine comprising a removing means. 5. A means for converting an image of a document into a density signal using an image reading means, a means for converting the density signal converted by the means into a digital image signal, and a digital image signal converted by the means. In a digital copying machine including image forming means for writing a sheet on a photoconductor, a conveying means for conveying a sheet-like document, a plurality of image reading means for reading the document being conveyed, and a digital output signal from the image reading means. Conversion means for converting into an image signal, delay means for delaying the output signal from the previous conversion stage, comparison means for comparing a plurality of digital image signals, detection means for detecting image noise, and image noise removal A digital copying machine comprising a removing means and a switching means for switching an image signal.