JP2011171992A - Document scanner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a document scanner for discriminating a vertical line on a document when skewing the document from a vertical streak due to dust on a scan surface in a short period of time with less erroneous detection, and also to provide an image forming apparatus. <P>SOLUTION: The document scanner automatically carries the original in a sub-scanning direction, photoelectrically converts reflection light from the document irradiated by a light source into image signals by a plurality of line sensors arranged in parallel with the sub-scanning direction, and corrects a position deviation in the sub-scanning direction among a plurality of line sensors after digital conversion. The document scanner has a dust detecting means for, when the document is inclined to a predetermined angle with respect to the line sensors so as to be automatically carried at a predetermined speed, comparing scanning data of the same main scanning pixel in the line sensors with those in the sub-scanning direction thereby to detect a difference in the scanning data of the line sensors, and determining whether the state of a difference in the scanning data continues for the portion of a prescribed number of lines, to determine whether the scanning data is the vertical line on the document or the vertical streak due to dust. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a document reading apparatus and an image forming apparatus having an automatic document feeding function.

Examples of technology related to the present invention include the following.
In the technique of Patent Document 1, when reading through a sheet through (automatic document feeding, flow reading), the document is read with a slight tilt (skewed). At this time, the vertical line on the original is inclined by the skewed amount, but the dust attached to the reading surface is always at the same position regardless of the original conveyance, so that the vertical line is straight. Thereby, dust and vertical lines on the original are discriminated.

  In the technique of Patent Document 2, in order to detect the presence of dust on the reading surface during sheet-through (automatic document feeding, flow reading) reading, sub-scanning in which the position of the main scanning pixel or the data size does not change. It is judged whether there is a straight line extending in the direction. In other words, no matter how straight the straight line on the document is, the position of the main scanning pixel or the size of the data does not change at all due to a slight skew during document transportation. It is.

  In the technique of Patent Document 1, a specific method for discriminating between a vertical line on the original when the original is read obliquely and a vertical streak due to dust on the reading surface is not presented, but the vertical line on the original is inclined. In order to detect this, it has to be determined by extracting a corresponding number of lines in the sub-scanning direction. Therefore, there is a problem that it takes time to determine. In addition, there is a problem that false detection is likely to occur when a vertical line is accidentally approached by skewing an oblique line originally on the document.

  In the technique of Patent Document 2, in order to detect whether there is dust on the reading surface, it is determined whether there is a straight line extending in the sub-scanning direction where the position of the main scanning pixel or the data size does not change. However, it must be determined by extracting a corresponding number of lines in the sub-scanning direction. Therefore, there is a problem that it takes time to determine.

  The present invention has been made in view of the above circumstances, and is a document that can distinguish between vertical lines on a document when the document is skewed and vertical stripes due to dust on the reading surface in a short time and with few false detections. An object is to provide a reading device and an image forming apparatus.

  In order to achieve such an object, an original reading apparatus according to the present invention includes an automatic document feeding mechanism that automatically conveys a document in the sub-scanning direction, a light source that irradiates a document conveyed by the automatic document feeding mechanism, and a light source that emits light. A photoelectric conversion member that photoelectrically converts reflected light from the original document into an image signal, and a converter that digitally converts the image signal converted by the photoelectric conversion member. And a line correction unit that corrects misalignment in the sub-scanning direction between the plurality of line sensors, and the document conveyed by the automatic document feeding mechanism is transferred to the plurality of line sensors. In contrast, when scanned at a preset angle and transported at a preset speed, read data of the same main scanning pixel in a plurality of line sensors is sub-scanned. Is detected as a vertical line on the document by detecting the difference between the reading data of multiple line sensors and determining whether the difference state of the reading data continues for a predetermined number of lines. Or dust detection means for determining whether the vertical streak is caused by dust.

  In the document reading apparatus of the present invention, the dust detection means determines that the read data is a vertical line on the document when the difference between the read data continues for a predetermined number of lines, and the difference between the read data is determined. When the state does not continue for a predetermined number of lines, it is determined that the read data is a vertical line due to dust.

  The document reading apparatus according to the present invention further includes a data deleting unit that deletes the read data by replacing the read data with white data or background data when the dust detection unit determines that the read data is vertical streaks due to dust. It is characterized by.

  Further, in the document reading apparatus of the present invention, a preset angle and a preset value are set for the read data of the document that is inclined at a preset angle by the automatic document feeding mechanism and conveyed at a preset speed. Image data moving means for performing correction to move the pixel based on the speed is provided.

  The document reading apparatus according to the present invention further includes a double-sided simultaneous reading mechanism that simultaneously reads the front and back surfaces of the document, and the dust detection unit, the data deletion unit, and the image data moving unit read the surface read by the double-sided simultaneous reading mechanism. A common process is performed for each of the data and the read data on the back surface.

  In the document reading apparatus of the present invention, at least one of a preset angle and a preset speed is variable.

  Further, in the document reading apparatus of the present invention, the plurality of line sensors are color line sensors of three lines or four lines including the same, and the read data of the same main scanning pixel is read data of a plurality of colors. Features.

  An image forming apparatus according to the present invention includes the document reading apparatus according to the present invention.

  According to the present invention, it is possible to discriminate between a vertical line on the original when the original is skewed and a vertical streak caused by dust on the reading surface in a short time and with few false detections.

1 is a side sectional view showing an example of the overall configuration of a general document reading apparatus with an automatic document feeder. 1 is a block diagram illustrating an example of a circuit configuration of a general document reading device with an automatic document feeder. FIG. FIG. 6 is a diagram illustrating an example of an image when the document is read obliquely by the document reading device. 1 is a block diagram illustrating a circuit configuration example of a document reading apparatus with an automatic document feeder according to an embodiment of the present invention. 6 is a flowchart showing an operation example of a document reading apparatus with an automatic document feeder according to an embodiment of the present invention. 1 is a side cross-sectional view illustrating an example of the overall configuration of a double-sided simultaneous document reading apparatus with an automatic document feeder according to an embodiment of the present invention. 1 is a block diagram illustrating an example of a circuit configuration of a document reading device that is equipped with an automatic document feeder and performs simultaneous duplex reading according to an embodiment of the present invention. FIG. 1 is a side sectional view showing an example of the overall configuration of an image forming apparatus according to an embodiment of the present invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments (embodiments) for carrying out the present invention will be described in detail with reference to the accompanying drawings.

  A document reading apparatus (image reading apparatus) according to an embodiment of the present invention described below is assumed to be a document reading apparatus using a color CCD (Charge Coupled Device) as a photoelectric conversion member. .

  FIG. 1 shows a configuration of a general document reading apparatus with an automatic document feeder. As shown in FIG. 1, the document reading device includes a contact glass, a xenon lamp (light source lamp), a first carriage, a second carriage, a lens, a CCD, a SDU (Sensor Board Unit), and the like. The document reading device reads the document on the contact glass, and the following two reading methods are possible. One is carriage reading (pressure plate reading). In this method, the first carriage and the second carriage are moved to the right in the drawing by a driving source (motor), and the entire surface of the document pressed against the contact glass by the pressure plate is read. The other is sheet-through reading. The first carriage and the second carriage are fixed at predetermined positions on the reading window formed on the contact glass, the xenon lamp is turned on with respect to the reading window, and the ADF (auto document feeder on the contact glass). This is a method of reading an image on a document conveyed by an automatic document feeding mechanism) from a reading window.

  When reading several to several tens of originals continuously, sheet-through reading is used, and when reading a book original or a thick paper original that cannot use the ADF, carriage reading is used. In the document reading apparatus, the optical image obtained by these reading methods is read by a CCD, which is a photoelectric conversion member, and subjected to photoelectric conversion to obtain an image signal.

  FIG. 2 shows a circuit block of a general document reading apparatus. Signals from three color line sensors (color line CCDs) of R (red), G (green), and B (blue) are subjected to image signal processing and analog / digital conversion processing by an AFE (analog front end). The three line sensors are arranged in parallel in the sub-scanning direction. In the present embodiment, three lines are taken as an example, but a color line sensor having four or more lines including the three lines may be used.

  The next interline correction unit corrects a positional deviation in the sub-scanning direction between the lines. The interval between the R, G, and B line sensors is 0.338 mm (8 line intervals between B and G and between G and R when reading 600 dip). That is, the position to be read at the same time is different for each color, which is in the order of B, G, and R, but this positional deviation is corrected by delaying the image data. Specifically, the read data for 8 lines for B and the read data for 16 lines for G are stored in the memory and then output to match the timing of the read data for R. The image on the original conveyed by the interline correction is adjusted in output timing for each of R, G, and B colors. The correction amount of the inter-line correction is changed according to the variable magnification when changing magnification for enlargement or reduction, that is, when changing the transport speed in the sub-scanning element direction. For example, at the time of 200% enlargement, there are 16 line intervals between BG and GR.

  The last shading correction circuit corrects CCD sensitivity unevenness and light source main scanning spectral distribution unevenness.

  In the document reading apparatus of the present embodiment, in addition to reading the document obliquely, the document conveyance speed is controlled. That is, in the document reading apparatus according to the present embodiment, the ADF conveys the document at a preset conveyance speed while tilting the document at an angle (oblique reading angle) set in advance with respect to each line sensor. Originally reading an original obliquely means that the original is read at a slower speed than the original because the sub-scanning direction has a cosine speed relative to the conveyance direction. Normally, it is considered to increase the conveyance speed so that the sub-scanning direction becomes the original reading speed, but in this embodiment, the fact that the speed is low in the sub-scanning direction is used.

  FIG. 3 shows an example of an image when it is read obliquely by the document reading device. Here, for ease of explanation, for example, the oblique angle is set to 8 in the sub-scanning direction with respect to the transport direction 9, that is, cos θ = 8/9, θ = 27.3 degrees, and the reading surface is exactly the main scanning direction. Four pixels of dust are 4 pixels of main scanning on the original and a straight line extending in the sub-scanning direction with a width of 4 pixels of main scanning, and an angle just opposite to the angle of oblique reading (that is, −27.3 degrees). It is assumed that a diagonal line of width is drawn. Regardless of whether the document is read obliquely, the image due to dust on the reading surface is a vertical black streak because the same pixels are always black for all of R, G, and B (a in the figure). On the other hand, the straight line on the document is inclined at the same angle as the document tilt angle (b in the figure). Even if it is slanting, it actually depends on the resolution and the number of gradations of the pixel, but it becomes a jagged line as shown in FIG. It should be noted that in this jagged line, at the leading edge, the trailing edge, and all the corners that are in the shape of a jagged line (the parts indicated by the arrows x and y in the figure. However, all of them correspond to each other), and a colored image generated because the correction cannot be completed by the inter-line correction appears. This is because the speed in the sub-scanning direction here is 8/9, so the correction value between lines B and G and G and R must be 9 lines, 100% Since each of the 8 lines is the same as at the time of reading, the correction is insufficient. For this reason, at the tip and the jagged corner indicated by the arrow y (the upper part of the jagged edges), only R is one line (R, G, B) and B and G are white. There is only one line where B and G are black and only R is white (the color combining RGB is red). Similarly, the rear edge and the jagged corner indicated by the arrow x (the jagged lower portion) have only one line where only B is white and G and R are black (the color combining RGB is blue). Subsequently, there is only one line where B and G are white and only R is black (the color obtained by combining RGB is cyan). C in the figure is an image of an oblique line having an angle just opposite to the tilt angle. At first glance, since it is a vertical line, it is indistinguishable from vertical streaks due to dust, but a colored image similar to the above b appears at the front end indicated by arrow y and the rear end indicated by arrow x.

  The document reading apparatus according to the present embodiment is characterized in that by detecting this colored image, a vertical line on the document is identified if there is a colored image, and a vertical stripe due to dust on the reading surface if there is a colored image. Although it can be detected only at the leading and trailing edges of black data, it can also be detected at the upper and lower jagged edges in addition to the slanted line.

  FIG. 4 shows a circuit block of the document reading apparatus according to the present embodiment. Compared with the circuit block of the general document reading apparatus shown in FIG. 2, the circuit of the document reading apparatus according to the present embodiment includes a dust detection block, a data deletion block, and an image data movement block in the subsequent stage of the shading correction circuit. Added. In the document reading apparatus of the present embodiment, dust detection is mainly performed. However, an image read at the time of dust detection can be used as it is as a read image. For this purpose, a data deletion block and an image data movement block are prepared. Since the original reading apparatus according to the present embodiment uses a memory originally for line-to-line correction, a storage device that stores image data on a large scale is not particularly required. That is, the technique disclosed in Patent Document 1 has a problem that a storage device capable of storing a considerable amount of image data for detecting whether the vertical line on the document is diagonal is necessary. However, there is a problem that a storage device capable of storing a considerable amount of image data for detecting whether or not the line on the document is straight is necessary. However, the document reading apparatus according to the present embodiment can solve this problem. In addition, in the document reading apparatus according to the present embodiment, it is significant that dust detection can be performed in real time.

  FIG. 5 shows a flow of operations in the case of detecting dust, deleting data detected as dust, and moving image data in the document reading apparatus of this embodiment.

  In the document reading apparatus of this embodiment, at least one of the oblique reading angle and the conveyance speed of the document conveyed by the ADF is variable. Here, it is assumed that the oblique reading angle θ and the conveyance speed V are first set in the original reading apparatus before starting reading the original (S1). The ADF conveys a document to be read at a conveyance speed V while being inclined at an oblique reading angle θ with respect to the R, G, B line sensors (CCD) arranged in parallel in the sub-scanning direction.

  In the original reading apparatus, reading of the conveyed original is started (S2). The document reading apparatus performs AFE processing (image signal processing and analog / digital conversion), line-to-line correction, and shading correction on the signal from each line sensor as shown in the block of FIG.

  Next, the document reading apparatus sequentially performs dust detection, data deletion, and image data movement as in the block shown in FIG. That is, the original reading device screens the data on the read image in real time according to the follow-up, determines vertical lines on the original and vertical streaks due to dust on the reading surface (S3 to S5; dust detection in FIG. 4). The image data detected as dust is deleted (S6; data deletion in FIG. 4) and the image data is moved (S7; image data movement in FIG. 4). These will be described in detail below.

  First, the document reading apparatus determines whether the data of the same pixel (read data of the same main scanning pixel) is black data in all of R, G, and B in the read image (S3). If the result of determination in S3 is not black data (S3 / NO), the process proceeds to S7.

  If the result of the determination in S3 is black data (S3 / YES), the document reading apparatus determines whether the read values of R, G, and B are characteristic data before and after the black data (S4). Whether the read values of R, G, and B are characteristic is a difference in read data of R, G, and B due to excessive or insufficient correction between lines. For example, as a result of comparing the read data of the same main scanning pixel in a plurality of line sensors in the sub-scanning direction, if the difference in the read data is detected by a predetermined threshold value or more, it is determined as characteristic data. If the result of determination in S4 is not characteristic data (S4 / NO), the process proceeds to S7.

  If the result of the determination in S4 is characteristic data (S4 / YES), the document reading apparatus determines whether the difference state of the read data continues for the number of lines determined by V and θ (S5). Whether or not the number of lines determined by V and θ continues is the number of lines that are excessive or insufficient for interline correction.

  If the result of the determination in S5 is not continuous (S5 / NO), the document reading apparatus determines that it is dust (a vertical streak), and deletes the image data (S6). This deletion of image data refers to replacing pixel data detected as dust with white data or surrounding data. This is done while reading the document.

  As a result of the determination in S5, if the document continues (S5 / YES), the document reading apparatus determines that the image is an image and moves the image data (S7). This movement of image data refers to restoring an image read obliquely and at a reduced speed. That is, the document reading apparatus moves each pixel data by image processing in accordance with the oblique reading angle θ and the conveyance speed V set in advance in S1, and thereby the inclination of the image and the expansion / contraction in the sub-scanning direction. Colored images due to excessive or insufficient line correction are corrected. As a result, the original read image is restored. The movement of the image data will be described with reference to the example of FIG. 3. The document reading apparatus restores the image inclined by 27.3 degrees, shrinks it by 8/9 in the sub-scanning direction, and performs line-to-line correction. Increase one line.

  The above S3 to S8 are repeated until the reading of the original is completed (S8).

  In the description of FIG. 5 described above, there are cases where it is difficult to distinguish between dust and vertical lines because the angle of inclination (angle of oblique reading) is small or the conveyance speed is not changed. In such a case, it is one method to greatly change the inclination angle and the conveyance speed. If the document conveyance speed is changed more dramatically while being read obliquely, the amount of over- and under-line correction increases, so the colored image increases or decreases according to the speed. Since the number of colored lines with respect to the set speed is determined, it can be used as a determination condition.

  The document reading apparatus of this embodiment can also be applied to double-sided simultaneous reading. FIG. 6 shows the configuration of a document reading apparatus for simultaneous reading on both sides. As shown in FIG. 6, a CIS (contact image sensor) in which a light source, an optical system, and a reading sensor are integrated is provided inside the ADF. Thus, it is possible to simultaneously read the front side with a scanner and the back side with a CIS in one document conveyance.

  FIG. 7 shows a block of a circuit when the document reading apparatus according to the present embodiment is applied by double-sided simultaneous reading. Although not shown in the figure, the CIS includes a sensor unit on the back surface, an AFE, and a shading correction circuit. As a result, the document reading apparatus reads the back surface with the CIS in parallel with reading the front surface with the scanner. Image data read by the scanner and the CIS is input to the front / back data sort block in FIG.

  The front / back data sort block is not a feature of the present embodiment, but is also mounted on a conventional document reading apparatus for simultaneous duplex reading. The front / back data sort block is used to alternately output front and back images that are input simultaneously in parallel in the surface sequence. From the back side or back side data storage memory and the front / back data switching gate Become.

  As shown in FIG. 7, when the document reading apparatus according to this embodiment is applied by double-sided simultaneous reading, the dust detection block, data deletion block, and image data movement block, which are the features of this embodiment, are the same as in FIG. It is placed after the front / back data sort block. With this configuration, dust detection, data deletion, and image data movement are performed on the front side image data, and dust detection, data deletion, and image data movement are performed in the same manner on the back side image data. That is, common processing (dust detection, data deletion, image data movement) is performed on the image data on the front surface and the image data on the back surface. However, since the back surface has an opposite inclination angle, the image data movement on the back surface is opposite to the front surface. In addition, since the line spacing may be different between the front surface and the back surface, the number of colored lines for the back surface is set.

  The document reading apparatus of the present embodiment configured as described above can be mounted on an image forming apparatus such as a multifunction peripheral or a digital copying machine. The image forming apparatus will be described below.

  FIG. 8 is a block diagram showing an example of an image forming apparatus according to an embodiment of the present invention. An image forming apparatus 1 shown in FIG. 8 includes an apparatus housing 2 formed in a vertically long rectangular shape, an automatic document feeder (ADF) 3 provided on the upper portion of the apparatus housing 2, and an upper side of the apparatus housing 2. An image reading device 4 provided on the apparatus housing 2, an image creating device 5 provided on the lower side of the device housing 2, an operating device 7 provided on the upper portion of the device housing 2, and a lower side in the device housing 2. And a paper feeding device 8. The automatic document feeder 3 and the image reading device 4 correspond to the document reading device of the present embodiment described above.

  The automatic document feeder 3 includes a feeder housing 9 that can be opened and closed by a hinge (not shown) with respect to an upper portion of the device housing 2, and a document table (document tray) 10 provided on the upper portion of the feeder housing 9. And. The document table 10 is a document table on which a document bundle composed of a plurality of documents can be placed. The automatic document feeder 3 also separates documents one by one from a document set detection sensor 11 that detects when a document is set on the document table 10 and a document bundle set on the document table 10. And a feeding roller 12 that is conveyed toward the contact glass 18. The automatic document feeder 3 includes a plurality of rollers 13, a feeding belt 14, and the like, and a feeding mechanism 15 that feeds a document taken in by the feeding roller 12 onto a contact glass 18 on the apparatus housing 2 side. Then, after the image is read on the contact glass 18, the original conveyed by the feeding mechanism 15 is taken in and discharged onto a paper discharge unit (paper discharge tray) 16 formed on the upper portion of the feeder housing 9. And a discharge roller 17. The automatic document feeder 3 also includes a control unit (not shown) that performs processing for controlling the document set detection sensor 11 to the discharge roller 17 and processing for counting the number of fed documents, and control of the control unit. And a conveying motor (not shown) for driving the feeding roller 12 to the discharging roller 17. The transport motor is driven by an output signal from the control unit. When a paper feed start signal (original feed instruction) is input from the image creating apparatus 5, the control unit drives the transport motor in the forward and reverse directions.

  In the automatic document feeder 3, for example, when a print key of the operation device 7 to be described later is pressed, the conveyance motor is driven to rotate forward by the control unit, and the feeding roller 12 rotates in the clockwise direction to move the uppermost position from the document bundle. Is fed to the contact glass 18. When the leading edge of the document is detected by the document set detection sensor 11, the control unit drives the transport motor in the reverse direction based on the output signal from the document set detection sensor 11. This prevents subsequent documents from entering and prevents separation. Further, when the document set detection sensor 11 detects the trailing edge of the document, the control unit counts the rotation pulses of the carry motor from this detection time point. When the rotation pulse reaches a predetermined value, the control unit stops driving the feeding belt 14. As a result, the document is stopped at the reading position on the contact glass 18.

  When the document stops at the reading position of the contact glass 18, the image reading device 4 performs image reading and exposure of the document. When these operations are completed, a signal from the image forming apparatus 1 is input to the control unit. The control unit drives the conveyance motor to rotate forward, and conveys the document from the contact glass 18 to the discharge roller 17 by the conveyance belt 14. The original is discharged onto the paper discharge unit 16 by the discharge roller 17. The above document conveying process is repeated. That is, when it is detected by the document set detection sensor 11 that the next document is present on the document table 10, the next document is fed again onto the contact glass 18 as described above.

  The image reading device 4 is incorporated in an opening formed in the upper portion of the apparatus housing 2 and is closed by the automatic document feeder 3 so as to be freely opened and closed, and a guide rail (inside the apparatus housing 2). The first carriage 19 is configured to be movable in the sub-scanning direction and is driven to run at a first speed corresponding to the magnification. Further, the image reading device 4 is disposed on the first carriage 19 and the light source (exposure lamp, xenon lamp) 20 that illuminates the document placed on the contact glass 18 and the first carriage 19. And a first mirror 21 that reflects light (optical image) from the document. Further, the image reading device 4 is configured to be movable in the sub-scanning direction by a guide rail (not shown) disposed in the device housing 2, and an optical path for reading a document even when the first carriage 19 moves. A second carriage 22 that is driven to travel at a half speed (second speed) of the first speed is provided so that the length is constant. In addition, the image reading device 4 is disposed on the second carriage 22 and second and third mirrors 23 and 24 that reflect the optical image reflected from the first mirror 21 and is movably disposed in the device housing 2. A lens 25 is provided that focuses the optical image emitted from the third mirror 24 by adjusting the position according to the focus, magnification, and the like. The image reading device 4 is movably disposed in the device housing 2, is adjusted in position according to the focus, magnification, and the like, receives the optical image collected by the lens 25, and receives an electric signal ( A CCD image sensor 26 for conversion into an image signal) is provided. Although not shown in FIG. 8, the CCD image sensor 26 is mounted on the SBU as shown in FIG.

  When the image reading command is output from the image creating device 5, the image reading device 4 moves the position of the lens 25 and the CCD image sensor 26 in the left-right direction (sub-scanning direction) according to the reading magnification, the reading range, and the like. Adjust the position. After that, the image reading device 4 travels the first carriage 19 and the second carriage 22 in the sub-scanning direction at the first and second speeds with the light source 20 of the first carriage 19 turned on, An image of a document placed on the contact glass 18 is captured and condensed on the CCD image sensor 26 by the lens 25 to generate an image signal, which is supplied to the image creation device 5.

  The operating device 7 includes an LCD display (liquid crystal display) disposed on the upper portion of the device housing 2 so as to be long in the left-right direction. The operation device 7 is arranged on the upper surface of the LCD display. When the operator touches the LCD display, a touch panel that detects the touch and generates touch position information, and a numeric keypad arranged on the right side of the LCD display. A keyboard including a mode clear key, a clear / stop key, a print key that is a copy operation start instruction key, and the like. The operation device 7 has a microprocessor and includes an operation unit arranged on the upper side in the device housing 2. The operation unit communicates with the system controller on the image creating apparatus 5 side via the I / O port, and captures a display instruction command, status information, and the like output from the system controller and displays them on the LCD display. In addition, processing for detecting touched key position information on the touch panel, processing for detecting a key operated, processing for detecting operation details of the keyboard, processing for transmitting these processing results to the system controller, and the like are performed.

  The paper feeding device 8 is housed in the device housing 2 so as to be able to move in and out, and includes first to third paper feeding trays 47 to 49 in which transfer paper 46 of a specified size is stored. The paper device 8 is connected to the first to third paper feed trays 47 to 49 by an intermittent operation of first to third paper feed clutches (not shown) provided for the first to third paper feed trays 47 to 49. Are provided with first to third sheet feeding units 50 to 52 for taking out the respective transfer sheets 46 stored therein, an intermediate clutch (not shown) for intermittent operation, a plurality of conveying rollers 53, and the like. Further, the sheet feeding device 8 includes a vertical conveyance unit 54 that conveys the transfer paper 46 taken out by the first to third sheet feeding units 50 to 52 upward by an intermittent operation of the intermediate clutch, and the vertical conveyance unit 54. A registration roller 55 is provided which takes in the transferred transfer paper 46 and supplies the transfer paper 46 to the image forming apparatus 5 at a timing. When the printing operation is performed, the paper feeding device 8 takes out the transfer paper 46 of the designated size from the transfer papers 46 of the respective sizes stored in the first to third paper feed trays 47 to 49, and uses this. While being conveyed upward, the transfer paper 46 is supplied to the image creating device 5 in accordance with the timing at which the leading edge of the toner image formed on the photoreceptor 66 reaches the paper transfer position.

  The image creating device 5 reverses the front and back of the transfer paper 46 on which the image is once formed on the writing optical unit 56 that writes an optical image based on the image signal output from the image reading device 4, and sends it to the vertical conveyance unit 54. A reversing / double-side unit 57 that refeeds or transfers the transfer paper 46 to the paper discharge tray 81 is provided. Further, the image creating apparatus 5 visualizes the optical unit generated by the writing optical unit 56 as a toner image, and the transfer paper 46 taken out by the paper feeder 8. And a paper transfer unit 59 for transferring the toner image visualized by the unit 58. The image creating apparatus 5 also includes a fixing unit 60 that melts and fixes the toner on the transfer paper 46 on which the image is transferred by the paper transfer unit 59, and a transfer paper 46 on which the toner image is fixed by the fixing unit 60. A conveyance path switching unit 61 that leads to either a post-processing device (not shown) or a reversing / double-side unit 57 attached to the left side of the body 2, and a control board 62 that controls the operation of the entire image forming apparatus 1. I have. The image creating apparatus 5 visualizes the image indicated by the image signal output from the image reading apparatus 4 as a toner image, transfers the toner image onto the transfer paper 46 having a specified size, and then converts the toner image into the toner image. The image is fixed and supplied to a post-processing device (not shown) outside the image forming apparatus 1.

  The writing optical unit 56 includes a laser diode that generates laser light based on image data output from the control board 62, a polygon mirror that scans the laser light emitted from the laser diode, and a drive motor that rotates the polygon mirror. A laser output unit 63 configured is provided. Further, the writing optical unit 56 reflects the laser light from the lens group 64 such as an f-θ lens for fθ conversion of the laser light output from the laser output unit 63 and the visualization unit. And a mirror 65 to be supplied to 58. The writing optical unit 56 converts the image data output from the control board 62 into an optical signal, writes an optical image corresponding to the image data on the photosensitive member 66 constituting the visualization unit 58, and outputs the electrostatic latent image. Form.

  The visualization unit 58 includes a photoreceptor 66 on which a latent image is formed by laser light emitted from the writing optical unit 56 while being driven to rotate by a main motor (not shown). Further, the visualization unit 58 is arranged near one end of the photosensitive member 66, and generates a main scanning synchronization signal (LSYNC) when it detects the laser light emitted from the writing optical unit 56 and supplies it to the system controller. A beam sensor (not shown) is provided. The visualization unit 58 is arranged around the photoconductor 66 and is arranged around the photoconductor 66 (not shown) for cleaning the photoconductor 66, and the photoconductor 66 is made uniform. A charging unit (not shown) for charging the photosensitive member 66, and a developing unit 67 that is disposed around the photosensitive member 66 and that develops an electrostatic latent image formed on the photosensitive member 66.

  When performing the printing operation, the image creating apparatus 5 performs the cleaning process by the cleaning unit and the charging process by the charging unit on the surface of the photosensitive member 66 that is rotationally driven by the driving force of the main motor, and the writing optical unit 56. An optical image is written by a laser beam emitted from the laser beam to form an electrostatic latent image. Thereafter, the image creating device 5 develops the electrostatic latent image formed on the photoreceptor 66 by the developing unit 67 to form a toner image.

  The paper transfer unit 59 is disposed so as to face the photoconductor 66, and includes a paper transfer bias roller 68 to which a bias voltage is applied when the toner image formed on the photoconductor 66 is transferred to the transfer paper 46. Yes. The paper transfer unit 59 is stretched around a drive roller 69 that is rotationally driven by a main motor and the drive roller 69 and the paper transfer bias roller 68, and the toner image on the photoconductor 66 is transferred by the paper transfer bias roller 68. And a transport belt 70 for transporting the transferred transfer paper 46.

  When performing the printing operation, the image creating apparatus 5 presses the conveyance belt 70 against the photosensitive member 66 with the transfer paper 46 supplied from the registration roller 55 interposed therebetween, and applies a predetermined bias voltage to the paper transfer bias roller 68. Apply. Then, the image creating device 5 transfers the toner image formed on the photoconductor 66 to the transfer paper 46. At the time of this transfer, the transfer paper 46 is transported by the transport belt 70 at the same speed as the rotation of the photoconductor 66. The transfer paper 46 onto which the toner image has been transferred is conveyed to the fixing unit 60.

  The fixing unit 60 includes a fixing roller 71 controlled to have a predetermined temperature, and a pressure roller 72 that presses the transfer paper 46 conveyed by the paper transfer unit 59 against the fixing roller 71. The fixing unit 60 heats the transfer paper 46 conveyed from the paper transfer unit 59 while applying pressure, melts and fixes the toner image formed on the transfer paper 46, and carries it out to the conveyance path switching unit 61. .

  The transport path switching unit 61 includes a take-in roller 73 that takes in the transfer paper 46 supplied from the fixing unit 60, and a switching claw (not shown) that switches the transport path of the transfer paper 46 taken in by the take-in roller 73. Yes. In addition, when the transfer paper 46 is guided to the left side (left side in FIG. 8) by the switching claw, the transport path switching unit 61 transports the transfer paper 46 to the left side and guides it to the discharge tray 81 outside the apparatus. When the transfer paper 46 is guided to the lower side (lower side in FIG. 8) by the paper discharge roller 75 and the switching claw, the reversing / double-sided paper feeding roller 76 guides this to the reversing / double-sided unit 57, and the reversing / double-sided unit. And a reverse paper discharge roller 78 for guiding the transfer paper 46 reversed by 57 to a paper discharge tray 81. The transport path switching unit 61 takes in the transfer paper 46 transported from the fixing unit 60 and switches the transport direction with a switching claw based on an instruction from the system controller to guide the paper discharge tray 81 as it is or the reversing / duplex unit 57. Or lead to. For example, when the stapling mode is not performed, the transfer paper 46 is discharged onto the paper discharge tray 81.

  The reversing / duplex unit 57 takes in the transfer paper 46 supplied from the transport path switching unit 61 and then transports it in the reverse direction to reverse the front and back of the transfer paper 46 and the reversed transfer paper 46. And a re-feed roller 79 for feeding to the vertical conveyance unit 54 of the paper feeder 8. The reversing / double-side unit 57 takes in the transfer paper 46 supplied from the transport path switching unit 61 when the reverse discharge instruction is output from the system controller, and then changes the transport direction of the transfer paper 46 by the reverse roller 77. The transfer sheet 46 that has been reversed by the reverse discharge roller 78 is discharged to the discharge tray 81. Further, the reversing / duplex unit 57 transports the transfer paper 46 by the reversing roller 77 after taking in the transfer paper 46 supplied from the transport path switching unit 61 when the duplex controller is output from the system controller. The direction is reversed, and the transfer sheet 46 that has been reversed by the refeed roller 79 is supplied to the vertical conveyance unit 54 of the sheet feeder 8.

  The control board 62 includes a system controller that controls the overall operation of the image forming apparatus 1, and controls the operation of each part of the apparatus based on a preset program to perform a document image reading process, a printing process, and the like. Make it.

  The actions and effects of the document reading apparatus and the image forming apparatus of the present embodiment described above are summarized as follows.

  According to the document reading apparatus of this embodiment, the read data of the same main scanning pixel in each line sensor is compared in the sub-scanning direction, and the number of lines in which the difference in the read data is equal to or greater than a certain threshold and the state continues. Detect if is a value. As a result, by detecting a slight number of lines in the sub-scanning direction, it is possible to discriminate between vertical lines on the document and vertical lines due to dust on the reading surface. That is, it is possible to discriminate between a vertical line on the original when the original is skewed and a vertical streak due to dust on the reading surface in a short time and with few false detections.

  Further, according to the document reading apparatus of the present embodiment, image data detected as dust is replaced with background data of the document during image reading. Thereby, it is possible to delete vertical stripes due to dust on the reading surface.

  Further, according to the document reading apparatus of the present embodiment, the document transport speed is variable. As a result, the number of lines in which the difference in the read data continues also changes according to the speed, so that it is possible to more accurately distinguish vertical streaks due to dust and vertical lines on the document.

  Further, according to the document reading apparatus of the present embodiment, the angle at which the document is read obliquely is variable. As a result, the number of pixels in which the difference in the read data changes according to the angle, so that it is possible to more accurately discriminate vertical streaks due to dust and vertical lines on the document.

  Further, according to the document reading apparatus of this embodiment, the data of each pixel is moved in position by image processing for an image formed by tilting the document or changing the conveyance speed. As a result, it is possible to restore the original image without the inclination of the image, the expansion / contraction in the sub-scanning direction, or the difference in the read data.

  Further, according to the document reading apparatus of the present embodiment, the plurality of line sensors are color line sensors, and the difference between the read data of each line sensor at the same main scanning position is the output value of each color. Thereby, particularly in the case of color, it is possible to more accurately determine vertical streaks due to dust and vertical lines on the original.

  Further, according to the document reading apparatus of the present embodiment, both sides of the document can be simultaneously read using the reading unit for reading the front side and the reading unit for reading the back side, and the image on each of the front and back sides of the document is caused by dust. The vertical stripes and vertical lines on the document can be discriminated, and the same comparison, detection, and processing are performed on both the front and back sides. Thereby, the handling of image data and the processing circuit can be made common, and the cost can be reduced.

  In addition, the image reading apparatus of this embodiment is mounted on the image forming apparatus. Thereby, also in the image forming apparatus, it is possible to obtain the same effect as the above-described document reading apparatus of the present embodiment.

  As mentioned above, although embodiment of this invention was described, it is not limited to the said embodiment, A various deformation | transformation is possible in the range which does not deviate from the summary.

  For example, the operation in the above-described embodiment can be executed by hardware, software, or a combined configuration of both.

  When executing processing by software, a program in which a processing sequence is recorded may be installed and executed in a memory in a computer incorporated in dedicated hardware. Or you may install and run a program in the general purpose computer which can perform various processes.

  For example, the program can be recorded in advance on a hard disk or a ROM (Read Only Memory) as a recording medium. Alternatively, the program is temporarily or permanently stored on a removable recording medium such as a CD-ROM (Compact Disc Read Only Memory), an MO (Magneto optical) disc, a DVD (Digital Versatile Disc), a magnetic disc, or a semiconductor memory. It can be stored (recorded). Such a removable recording medium can be provided as so-called package software.

  The program may be wirelessly transferred from the download site to the computer in addition to being installed on the computer from the removable recording medium as described above. Or you may wire-transfer to a computer via networks, such as LAN (Local Area Network) and the internet. The computer can receive the transferred program and install it on a recording medium such as a built-in hard disk.

  In addition to being executed in time series in accordance with the processing operations described in the above embodiment, the processing capability of the apparatus that executes the processing, or a configuration to execute in parallel or individually as necessary Is also possible.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Apparatus housing 3 Automatic document feeder 4 Image reading device 5 Image creation apparatus 7 Operation device 8 Paper feeder 9 Feeder housing 10 Document table 11 Document set detection sensor 12 Feed roller 13 Roller 14 Feed Belt 15 Feed mechanism 16 Paper discharge unit 17 Discharge roller 18 Contact glass 19 First carriage 20 Light source 21 First mirror 22 Second carriage 23 Second mirror 24 Third mirror 25 Lens 26 CCD image sensor 46 Transfer paper 47 First Paper feed tray 48 Second paper feed tray 49 Third paper feed tray 50 First paper feed unit 51 Second paper feed unit 52 Third paper feed unit 53 Transport roller 54 Vertical transport unit 55 Registration roller 56 Write optical unit 57 Reverse / Duplex unit 58 Visualization unit 59 Paper transfer unit 60 Fixing unit 61 Conveyance path switching unit 62 Control board 63 Laser output unit 64 Lens group 65 Mirror 66 Photoconductor 67 Development unit 68 Paper transfer bias roller 69 Drive roller 70 Conveying belt 71 Fixing roller 72 Pressure roller 73 Taking-in roller 75 Discharging roller 76 Reverse / Double-sided Input Roller 77 Reverse Roller 78 Reversed Discharge Roller 79 Refeed Roller 81 Discharge Tray

JP 2006-33530 A JP 2006-229719 A

Claims (8)

An automatic document feeding mechanism that automatically conveys a document in the sub-scanning direction, a light source that irradiates the document conveyed by the automatic document feeding mechanism, and a photoelectric that photoelectrically converts reflected light from the document irradiated by the light source into an image signal A conversion member; and a converter for digitally converting the image signal converted by the photoelectric conversion member, the photoelectric conversion member including a plurality of line sensors arranged in parallel in the sub-scanning direction, and between the plurality of line sensors. An original reading apparatus provided with a line correction means for correcting a positional deviation in the sub-scanning direction,
The same main scanning of the plurality of line sensors when the document conveyed by the automatic document feeding mechanism is conveyed at a preset speed inclined at a preset angle with respect to the plurality of line sensors. The pixel reading data is compared in the sub-scanning direction to detect a difference between the reading data of the plurality of line sensors, and it is determined whether the reading data difference state continues for a predetermined number of lines. An original reading apparatus comprising dust detection means for determining whether data is a vertical line on the original or a vertical streak due to dust. The dust detection means includes
When the difference state of the read data continues for a predetermined number of lines, it is determined that the read data is a vertical line on the document,
2. The document reading apparatus according to claim 1, wherein when the state of the difference in the read data is not continuous for a predetermined number of lines, the read data is determined to be a vertical stripe due to dust.   2. The apparatus according to claim 1, further comprising: a data deleting unit that deletes the read data by replacing the read data with white data or background data when the read data is determined to be vertical streaks due to dust. Or the document reading device according to 2.   Pixels are read out based on the preset angle and preset speed with respect to the read data of the document that is tilted to the preset angle by the automatic document feeding mechanism and conveyed at the preset speed. 4. The document reading apparatus according to claim 1, further comprising an image data moving unit that performs correction for movement. 5. Equipped with a double-sided simultaneous reading mechanism that simultaneously reads the front and back sides of the document,
The dust detection means, the data deletion means, and the image data movement means are:
5. The document reading apparatus according to claim 4, wherein a common process is performed on each of the reading data on the front surface and the reading data on the back surface read by the double-sided simultaneous reading mechanism.   6. The document reading apparatus according to claim 1, wherein at least one of the preset angle and the preset speed is variable. The plurality of line sensors are three or more color line sensors including four lines,
The document reading apparatus according to claim 1, wherein the read data of the same main scanning pixel is read data of a plurality of colors.   An image forming apparatus comprising the document reading device according to claim 1.

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