JP2009200599A - Image processing apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently execute processings by controlling detection of dust and a processing time and maintaining compatibility with productivity. <P>SOLUTION: The image processing apparatus includes an image processing means for receiving image data to be outputted from a reading means for reading an original document in a sheet-through method, and applying predetermined processing to the received image data. In the image processing apparatus, if the time t1 between an original document transferred to an original reading position and a subsequent original document to be transferred for reading is enough, the processing time t2 for dust detection and dust correction is ensured much; and if the time t1 is short or the other processings increase, the processing time t2 for the dust detection processing and dust correction processing is reduced, thereby ensuring reading productivity. The processing time t2 is determined by managing the time t1 with a system controller. The processing time of each of the dust detection and dust correction may be independently set. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image processing apparatus that reads an image of a document and obtains an image from which noise such as dust is removed, and an image forming apparatus including the image processing apparatus.

Image forming apparatuses such as scanners, copiers, and facsimiles include an image processing apparatus that reads an original image and obtains an image from which noise such as dust is removed. When reading a document, an automatic document feeder (hereinafter referred to as ADF) that sequentially feeds the document to the image reading position is widely used. Since the ADF conveys the original and performs reading, when reading, noise such as dust adhering to the original is also read. Therefore, for example, Japanese Patent Application Laid-Open No. 2004-151620 describes that when a dust is detected, a user is notified. Patent Document 2 describes that when dust is detected, the distance between the papers, which is the interval between the documents to be fed next, is adjusted so that dust detection and image data correction are appropriately performed. Yes.
JP 2003-324590 A JP 2007-13399 A

  However, the processing performed between sheets includes, for example, replacement of various setting data and reading of white reference data for shading correction in addition to processing such as dust, and the content to be processed often increases or decreases each time. If time is spent on garbage processing, other processing may not be possible.

  Therefore, the problem to be solved by the present invention is to adjust the detection and processing time of dust and adjust the productivity to enable efficient processing.

  In order to achieve the object, the first means receives image data output from a reading means for reading a document by a sheet-through method, and includes an image processing means for performing a predetermined process on the received image data. In the processing device, processing for detecting dust at the reading position to be processed in the inter-paper time based on the inter-paper time between the original conveyed to the original reading position and the original conveyed for the next reading; and Control means for changing the processing time of at least one of the processing for correcting the pixel in which dust is detected is provided.

The second means gives priority to the dust processing for performing at least one of the processing for detecting dust detection and the processing for correcting the pixel for detecting dust detection, and the productivity of document reading in the first means. It further has a selection means for selecting one of the productivity priority processes.
The third means is characterized in that, in the first or second means, setting means is provided for setting the number of dust detection acquisition lines at the reading position.

  According to a fourth means, in any one of the first to third means, the control means performs dust determination based on the acquired dust candidate data for each line.

  A fifth means is characterized in that, in the fourth means, the dust determination of the acquired dust candidate data for each line is performed under a condition that the dust candidate regions are continuous each time in the same main scanning region.

  A sixth means includes the storage means for storing the dust candidates for each line in the fifth means, and the dust determination is performed based on a storage result stored in the storage means.

  A seventh means is characterized in that, in the fifth means, the dust candidate data for each line is logically summed and dust judgment is performed based on the line data subjected to the logical sum processing.

  According to an eighth means, in the first or second means, the threshold value of the detection output for dust detection is changed in accordance with a change in the light amount of the illumination means provided in the reading means due to a change in processing time between sheets. It is characterized by doing.

  A ninth means is characterized in that, in the fifth means, when the white reference data for shading correction is newly acquired, the threshold value setting of the dust detection output is returned to the initial value.

  A tenth means is characterized by an image forming apparatus including the image processing apparatus according to any one of the first to ninth aspects.

  In the embodiment described later, the reading means includes an exposure lamp 51, first to third mirrors 51, 55, and 56, a lens 53, a CCD image sensor 54, a first traveling body 61 on which the exposure lamp 51 and the first mirror 51 are mounted, The second traveling body on which the second and third mirrors 55 and 56 are mounted, the control means is the system controller 24, the selection means is the operation display section 22, the image processing means is the image processing section 25, and the storage means is the storage. Each corresponds to the unit 27.

  According to the present invention, when one or both of the processing for detecting dust and the processing for correcting a pixel in which dust is detected is secured when there is sufficient time between papers, and the time between papers is shortened When the number of processes increases, the reading productivity can be ensured by shortening the processing time.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited to the following embodiment, All the technical matters for embodying the technical idea defined by the claim are included.

  FIG. 1 is a diagram showing an outline of the system configuration of the entire image forming apparatus according to an embodiment of the present invention. The image forming apparatus according to the present embodiment is a so-called digital copying machine that can also function as a digital multifunction peripheral, and includes an ADF that automatically feeds a document to be read. The image forming apparatus is for forming a monochrome image. The main body 100, a writing unit 57 installed on the upper part of the main body 100, a reading unit 50 installed on the writing unit 57, and further installed thereon. The automatic document feeder (hereinafter referred to as “ADF”) 1 is basically configured.

  The ADF 1 includes a document table 2, feed rollers 3 and 4, a discharge roller 5, a document set detection sensor 7, a paper discharge table 8, and the like. The main body 100 includes a first tray 8, a second tray 9, a third tray 10, a first paper feeding unit 11, a second paper feeding unit 12, a third paper feeding unit 13, a vertical conveyance unit 14, a photoconductor 15, and a conveyance. The belt 16, the fixing unit 17, the paper discharge unit 18, the paper discharge tray 19, the developing unit 28, the double-sided conveyance unit 111, the reversing unit 112, the double-sided paper conveyance path 113, the reverse paper ejection conveyance path 114, and the like. The writing unit 57 includes a laser output unit 58, an imaging lens 59, a mirror 60, and the like. The reading unit 50 includes a contact glass 6, a white reference plate 62, an exposure lamp 51, first to third mirrors 51, 55, 56, a lens 53, a CCD image sensor 54, an exposure lamp 51 and a first mirror 51. The first traveling body 61 and the second traveling body on which the second and third mirrors 55 and 56 are mounted.

  Explaining the operation of these configurations, when a document bundle placed on the document table 2 of the ADF 1 with the image surface of the document facing up is pressed down on a start key (not shown) on an operation unit (not shown), The lowermost document is fed one by one to the reading position by the feeding roller 4. Note that the image forming apparatus according to the present embodiment has a counting function for counting up the number of originals upon completion of feeding one original. The fed original is conveyed to a reading position, and image data on the original is read by the reading unit 50. The image reading apparatus according to the present embodiment can correct a decrease in image quality that occurs when dust adheres to the reading position of the reading unit 50 and the reading position is changed. Details will be described later.

  The document that has been read is discharged to a paper discharge tray 8 by a feed roller 4 and a discharge roller 5. Further, when the document set detection sensor 7 detects that the next document is on the document table 2, it is fed to the reading position in the same manner as the previous document. The feed rollers 3 and 4 and the discharge roller 5 are driven by a transport motor (not shown).

  The transfer sheets stacked on the first tray 8, the second tray 9, and the third tray 10 are fed by the first sheet feeding unit 11, the second sheet feeding unit 12, and the third sheet feeding unit 13, respectively, and are vertically conveyed. The image is conveyed to the registration roller position by the unit 14, aligned with the image of the photoconductor 15 as an image carrier, and is unloaded from the registration roller. The image data read by the reading unit 50 is written onto the photoconductor 15 by the laser from the writing unit 57 to become a latent image, and the toner is developed by the developing unit 28 to form a toner image.

  On the other hand, the transfer paper carried out of the registration roller is conveyed by the conveyance belt 16 at the same speed as the rotation of the photoconductor 15, and the toner image on the photoconductor 15 is transferred. Thereafter, the image is fixed on the transfer paper by the fixing unit 17, and is discharged to the paper discharge tray 19 by the paper discharge unit 18.

  When forming an image on both sides of the transfer paper, the formed transfer paper is transported not to the paper discharge tray 19 but to the double-sided paper feed transport path 113 and switched back by the reversing unit 112 so as to be reversed. Send to. The sheet sent to the duplex conveyance unit 111 is sent again to the vertical conveyance unit 14 and is discharged after an image is printed on the back side. Further, when the transfer paper is reversed and discharged, the paper switchback reversed by the reversing unit 112 is sent to the reverse discharge conveyance path 114 instead of the duplex conveyance unit 111 and discharged.

  The photoconductor 15, the transport belt 16, the fixing unit 17, the paper discharge unit 18, and the development unit 28 are driven by a main motor (not shown). Each of the paper feeding devices 11, 12, and 13 is driven by the driving force of the main motor being transmitted through a paper feeding clutch (not shown). The vertical conveying unit 14 is driven by the driving force of the main motor transmitted by an intermediate clutch (not shown).

  The reading unit 50 includes a contact glass 6 on which an original is placed and an optical scanning system. The optical scanning system includes an exposure lamp 51, a first mirror 52, a lens 53, a CCD image sensor 54, and the like. The exposure lamp 51 and the first mirror 52 are mounted on the first traveling body 61. The second mirror 55 and the third mirror 56 are mounted on a second traveling body (not shown). When reading a document image, the first traveling body 61 and the second traveling body move in the sub-scanning direction at a speed ratio of 2: 1 so that the optical path length does not change. This optical scanning system is driven by a scanner drive motor. The document image is read by the CCD image sensor 54, converted into an electrical signal, and processed.

  The writing unit 57 includes a laser output unit 58, an imaging lens 59, and a mirror 60. Inside the laser output unit 58, although not shown, a laser diode that is a laser light source and a polygon mirror that is rotated at a constant speed by a motor are provided. The laser beam output from the writing unit 57 is applied to the image forming photoconductor 15. A beam sensor (not shown) for generating a main scanning synchronization signal is disposed at a position where a laser beam near one end of the photosensitive member 15 is irradiated.

  FIG. 2 is a block diagram showing an electrical system configuration for image reading.

  As an electrical configuration, it has an operation unit 21, an operation display unit 22, a reading unit 23, a system controller 24, an image processing unit 25, a ROM 26, and a storage unit 27, which are communicably connected via a bus. Yes.

  The operation unit 21 is provided with various operation keys for operating the image reading apparatus, such as a numeric keypad, a reading start key, and various other keys. The operation display unit 22 includes a display operation unit such as a liquid crystal touch panel that forms part of the operation unit 21 and a liquid crystal display, and displays an operation state of the apparatus to be notified to the user and various messages.

  The reading unit 23 reads an original image at a predetermined reading density to obtain an image signal. The system controller 24 controls each part of the apparatus according to a control program stored in the ROM 26 while using the storage unit 27 as a work area. The image processing unit 25 performs analog / digital conversion on the image signal from the reading unit 23, performs predetermined processing, and outputs the result. The ROM 26 is a read-only memory in which a control program for the system controller 24 to control each part of the device is stored. The storage unit 27 includes, for example, an HDD, an SRAM, and the like, and stores image data that has been subjected to predetermined processing by the image processing unit 25. Further, the RAM included in the storage unit 27 is a random access memory used as a work area of the system controller 24 as described above.

  FIG. 3 is a diagram for explaining a reading process for reading a document by sheet through, and shows the main part of the reading unit extracted from FIG. When reading a document through sheet-through, the document set on the ADF 1 is conveyed (sub-scanned) one by one in the direction of the reading position 32 by the feeding roller 3, and is at the main scanning line unit at the reading position 32. And is discharged by the paper discharge roller 5. The document set detection sensor 7 disposed in front of the reading position 32 detects the leading edge of the conveyed document and also detects the trailing edge. The background plate 33 is positioned on the upper surface (back surface as viewed from the reading side) of the reading position 32 of the conveyed document, and is read when dust is detected.

  In order to obtain white reference image data for shading correction or the like prior to the start of document reading, the first traveling body 61 is moved and the white reference plate 62 located on the back surface of the contact glass 6 is read. At the reading position 32, an image corresponding to one main scanning line located on the scanning line Ls is read from the image of the document. Note that the exposure lamp 51 is lit when the original image is read at the reading position 32 and when the white reference plate 62 is read.

  FIG. 4 is a block diagram showing a specific configuration of the image processing unit 25 of FIG. The image processing unit 25 includes an A / D converter 40, a dark correction data holding unit 41, a subtractor 42, a shading correction data holding unit 43, a multiplier 44, a correction processing unit 45, a quantization processing unit 46, and a dust detection unit 47. I have.

  The image signal output in units of main scanning lines from the reading unit 23 in FIG. 2 is quantized by analog / digital conversion by the A / D converter 40 of the image processing unit 25 at the time of reading the document. The dark output data obtained by reading the light source extinction state is held in the dark correction data holding unit 41 as dark correction data, and the subtracter 42 is subtracted from the image information level for each pixel constituting the image data for one main scanning line. The dark output correction is performed by reducing the dark output level of the corresponding pixel.

  Further, the shading correction data obtained from the white output level obtained by reading the reference plate 62 in advance with the light source turned on is stored in the shading correction data holding unit 43 for the image data after dark output correction, and one main scanning line. Is multiplied by the shading correction data of the corresponding pixel by the multiplier 44 to obtain the intensity unevenness of the light source and the sensitivity unevenness of each light receiving element of each pixel constituting the image sensor. to correct.

  The multi-valued image data subjected to dark correction and shading correction in this way is subjected to correction related to image quality, such as γ correction and MTF correction, by the correction processing unit 45, and then subjected to various modulation processes. 46, binarization or multi-value processing is performed and output as image data for various uses.

  In the present embodiment, multi-valued image data that has undergone dark correction and shading correction is also input to the dust detection unit 47.

  In the reading unit 3 having the configuration illustrated in FIG. 2, dust may adhere to the background plate 33 and the reading position 32. The dust does not affect the image data (read image data) obtained by reading the original if the attachment position is not on the scan line Ls, but if it adheres to the scan line Ls, the read image data is adversely affected. . Specifically, the dust adhering to the surface of the reading position 32 on the scan line Ls creates a shadow on the pixel corresponding to the attachment position and causes black stripes.

  FIG. 5 is a diagram showing an image signal waveform obtained by reading the background plate 33 for one main scanning line at the reading position. FIG. 5A shows at least the scan line Ls on the surface of the reading position 32 and the background plate 33. FIG. 5B shows the case where dust is attached on the scan line Ls. FIG. When dust is attached as shown in FIG. 5B, the printed recording paper obtained by printing the read image data on the recording paper becomes an abnormal image in which vertical black lines overlap the original image. End up. In FIG. 5B, since the signal level from the light receiving element of the pixel corresponding to the dust adhesion position is significantly lower than the signal level from the other light receiving elements, the threshold level Lth is set to the white reference. The image is set to an appropriate level equal to or lower than a level at which it can be determined as a normal level, and pixels having a level lower than the threshold level Lth are detected, so that the attachment of dust and the attachment position in the main scanning direction are determined. Can be detected. In this way, the dust detection unit 47 detects the presence / absence of dust and the position of attachment.

  In the example of FIG. 5, the data before the shading correction is shown. However, the same detection can be performed when the shading correction is performed. Note that dust detection processing at the reading position 32 is performed before and after reading a document and between jobs.

  The productivity at the time of reading the document in the reading unit 23 is based on a time obtained by combining the time for actually reading the document, the time for feeding the document, and the time for discharging the document. The time for paper supply and paper discharge is called the inter-document time, where various setting data are exchanged, dust detection processing, reading of white reference data for shading correction, and the like are performed. The processing performed between the sheets often involves an increase / decrease in the contents to be processed. In order to absorb the increase / decrease, the processing time change processing in the dust detection processing and dust correction processing is performed by the system controller 24. .

  FIG. 6 is a diagram showing an example of document reading time, paper interval time, and dust detection and dust correction processing time during the paper interval time. FIG. 6A shows a case where the paper interval time t1 is long. Indicates a short case. As shown in FIG. 6A, when the paper interval time t1 is sufficient, a large processing time t2 for dust detection and dust correction processing is secured. On the other hand, as shown in FIG. 6B, when the inter-paper time t1 is shortened or when other processes are increased, the processing time t2 of the dust detection processing and dust correction processing is shortened to improve the reading productivity. Secure. The paper interval time t1 and the dust detection processing and dust correction processing time t2 are controlled by managing the processing time t2 by the system controller 24. As a result, the dust detection process at the reading position to be processed at the inter-paper time t1 and the processing time t2 for correcting the dust-detected pixels are changed based on the inter-paper time between the original conveyed at the time of reading and the next original. be able to. In the present embodiment, the processing time for the dust detection process and the dust correction process is referred to as a processing time t2, but the dust detection process and the dust correction process are performed independently. Therefore, each processing time is available, and both processing times can be set or controlled independently.

  In the present embodiment, the processing time t2 of dust detection processing and dust correction processing for ensuring productivity is changed by the system controller 24. However, in order to perform setting again, the operation unit 21 of FIG. A switch for setting may be provided on the display unit 22. FIG. 7 is a diagram illustrating an example of a setting switch.

As the setting switch, the operation unit 21 is provided with a switch for instructing priority of either dust detection processing or dust correction processing, or the liquid crystal touch panel of the operation display unit 22 has a “dust detection processing / The message “Do you want to prioritize dust correction?” Is displayed, “YES” and “NO” are displayed, and the corresponding part is touched to input an instruction. This switches between giving priority to dust detection and correction processing or giving priority to predetermined reading productivity. Dust detection processing does not detect the presence or absence of dust in one line of image data, but samples multiple lines. There are many cases to do. This is because not only dust stuck to the reading position 32 to be detected in the sampled image data but also easily moving dust may accidentally cross during detection, so that the dust is not detected. Detect multiple lines. The number of lines is set by the system controller 24.

  In this embodiment, the background portion of the reading position 32 is shown as the background plate 33. However, when the background has the form of an endless belt or a roller, the background is switched. For this reason, it is useful to capture a plurality of lines in order to prevent accidental detection of background scratches and specific portion dust. By changing the number of sampling lines of a plurality of lines, the processing time can be changed.

  The dust determination is performed in accordance with the number of acquired lines for dust detection, and the system controller 24 processes the acquired number of lines as the number of lines for dust detection. With this processing, it is possible to correctly determine dust even if the number of acquired lines increases or decreases.

  The dust detection detection process by acquiring a plurality of lines will be described with reference to FIG. Here, the data is from the (n−1) th line data to the (n + 2) th line data.

  8A and 8B are diagrams showing the relationship between the main scanning position and output of acquired data for one line. FIG. 8A shows an example when dust is not detected, and FIG. 8B shows an example when dust is detected. In FIG. 8A, there is dust data detected by the dust detection threshold in the (n-1) th line data. In the next n-th line data, dust data does not exist at the same position, and dust data exists at another main scanning position. Further, dust data exists at a main scanning position different from the dust position of the (n-1) th line and the dust position of the nth line at the (n + 1) th line. Furthermore, there is no dust data detected by the threshold in the (n + 2) th line. In this way, when the dust data is not specified by the line, it is determined that the dust is transiently present at the reading position 32 and is not subjected to dust detection.

In FIG. 8B, dust data exists at the same position from the (n-1) th line to the nth line, the (n + 1) th line, and the (n + 2) th line. Since there is dust at the same position, it can be determined that the dust is stuck to the reading position 32. By performing dust detection in this manner, dust detection accuracy can be ensured.
The dust candidate data acquired in this way is recorded in the storage unit 27 line by line, and if there is dust at the same position in the main scanning by the dust detection unit 47 of the image processing unit 25 based on the recording at the time of dust determination, Detect that. Further, by performing the logical sum processing of the acquired dust detection line data in the dust detection unit 47, it can be determined that there is dust data in a specific pixel area of main scanning, and it can be determined that there is dust.

  As described above, when the processing time between the sheets is changed, the lighting time of the exposure lamp 51 becomes longer or shorter. The light amount of the exposure lamp 51 decreases due to the continuous lighting time. Therefore, the threshold for dust detection is switched according to the lighting time. Thereby, dust detection processing can be performed at a certain level. The system controller 24 controls the threshold for continuous lighting and dust detection.

  When white reference data for shading correction is newly acquired, the change in the amount of light of the exposure lamp 51 is canceled out by the shading correction process, so that it is necessary to return the threshold setting to the initial setting. Thereby, dust detection processing can be performed at a certain level. Acquisition of white reference data for shading correction and control of dust detection threshold are also performed by the system controller 24.

1 is a diagram illustrating an outline of a system configuration of an entire image forming apparatus according to an embodiment of the present invention. It is a block diagram which shows the electrical system structure for an image reading. FIG. 2 is a diagram illustrating a main part of a reading unit extracted from FIG. 1 in order to explain reading processing by document conveyance. FIG. 3 is a block diagram illustrating a specific configuration of an image processing unit in FIG. 2. FIGS. 4A and 4B are diagrams showing image signal waveforms obtained when a background plate is read for one main scanning line at a reading position. FIG. 5A shows a case where no dust is attached, and FIG. Is shown. 6A and 6B are diagrams illustrating an example of document reading time, paper interval time, and dust detection and dust correction processing time during the paper interval time, where (A) shows a case where the paper interval time is long and (B) a case where the paper interval time is short. ing. It is a figure which shows an example of a setting switch. It is a figure which shows the relationship between the main scanning position of the acquisition data for 1 line, and an output, (A) is an example when not detecting dust, (B) is an example when detecting dust.

Explanation of symbols

1 Automatic document feeder (ADF)
2 Document platen 8 Paper discharge table 15 Photoconductor 17 Fixing unit 28 Developing unit 22 Operation display unit 23 Reading unit 24 System controller 25 Image processing unit 27 Storage unit 32 Reading position 33 Background plate 43 Shading correction data unit 47 Dust detection unit 50 Reading Unit 51 Exposure lamp 57 Writing unit 61 Traveling object t1 Paper interval t2 Processing time

Claims (10)

In an image processing apparatus comprising image processing means for receiving image data output from a reading means for reading a document by a sheet-through method and performing predetermined processing on the received image data,
Processing for detecting dust at the reading position to be processed in the inter-paper time based on the time between original papers of the original transported to the original reading position and the original transported for the next reading, and dust detection An image processing apparatus comprising control means for changing a processing time of at least one of the processes for correcting pixels. The image processing apparatus according to claim 1.
Selection means for selecting one of dust processing for performing at least one of processing for detecting dust detection and processing for correcting pixels in which dust is detected, and productivity priority processing for giving priority to document reading productivity An image processing apparatus further comprising: The image processing apparatus according to claim 1 or 2,
An image processing apparatus comprising setting means for setting the number of dust detection acquisition lines at the reading position. The image processing apparatus according to any one of claims 1 to 3,
The image processing apparatus according to claim 1, wherein the control unit performs dust determination based on the acquired dust candidate data for each line. The image processing apparatus according to claim 4.
The image processing apparatus according to claim 1, wherein the dust determination of the acquired dust candidate data for each line is performed under a condition that the dust candidate regions continue in the same main scanning region every time. The image processing apparatus according to claim 5.
An image processing apparatus comprising storage means for storing dust candidates for each line, wherein the dust determination is performed based on a storage result stored in the storage means. The image processing apparatus according to claim 5.
2. An image processing apparatus according to claim 1, wherein a logical sum of the dust candidate data for each line is taken, and dust determination is performed based on the line data subjected to the logical sum processing. The image processing apparatus according to claim 1 or 2,
An image processing apparatus, wherein a threshold value of detection output for dust detection is changed in accordance with a change in light amount of an illumination unit provided in the reading unit due to a change in processing time between sheets. The image processing apparatus according to claim 5.
An image processing apparatus that returns a threshold setting of dust detection output to an initial value when white reference data for shading correction is newly acquired.   An image forming apparatus comprising the image processing apparatus according to claim 1.

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