JP2008124853A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that can detect inclined feeding of an original document at low cost and reads an image of the original document with accuracy. <P>SOLUTION: The apparatus includes: reading means for reading out an image of an original document fed to an image reading area; sensing means for sensing a size of the original document; area allocation means for allocating the image reading area to a passage area through which the fed original document passes and a non-passage area through which the fed original document does not pass, depending upon the size of the original document sensed by the sensing means; image density detecting means for detecting whether or not a density of the image read in the non-passage area is constant; and reading halt means for halting image reading of the original document via the reading means based on the detection results of the image density detecting means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus including an automatic document feeder that feeds a plurality of documents to an image reading area.

  In recent years, so-called digital multifunction peripherals having functions such as copying, facsimile, printer, and scanner have been widely used. When a large number of original sheets are copied using a digital multi-function peripheral, it is convenient to use an automatic document feeder (ADF (Auto Document Feeder)) that automatically reads a document continuously. The user simply sets the document on the document tray of the automatic document feeder and presses the start switch for starting image reading. The document is sequentially conveyed to the image reading area of the image reading unit, and the image of the document is read. It will be.

  However, there are cases where the user mistakenly sets a document on the document tray. For example, this may be the case when the document is set obliquely or when the end of the document is bent. In such a case, the document does not pass through the image reading area in a normal state, that is, in a state parallel to the conveyance direction, and passes in an inclined state. As a result, there arises a disadvantage that the image of the original is read in a distorted state.

  Further, when the roller for conveying the document to the image reading area is worn, it is one of the factors that cause the document to be conveyed obliquely. In this case as well, the original image cannot be read accurately.

  Therefore, in order to eliminate such inconvenience, it is detected whether or not the document is conveyed obliquely, and if the document is conveyed obliquely, the fact is notified to the user or the reading of the image is interrupted. Such measures are taken.

Sensors and switches are often used to detect oblique conveyance. For example, Patent Document 1 below describes an automatic document feeder in which two sensors that detect that a document has been conveyed are provided in a direction orthogonal to the document conveyance direction. According to this automatic document feeder, it is expected that it is possible to detect whether or not the document is conveyed obliquely by measuring the time difference detected by the two sensors. That is, when there is no detection time difference, it indicates that the document has been normally conveyed, and as the detection time difference increases, it indicates that the document has been conveyed in an inclined state.
JP 7-154540 A

  However, separately providing detection components such as sensors and switches as described above only for detection of oblique conveyance results in an increase in cost. In particular, it is difficult to add and mount new parts for a complex machine such as a low-end machine that has a strict requirement for cost reduction.

  The present invention is proposed in order to solve the above-described conventional problems, and can detect an oblique conveyance of a document at a low cost, thereby preventing an image from being read in a distorted state. An object of the present invention is to provide an image forming apparatus capable of performing the above.

  An image forming apparatus of the present invention includes a reading unit that reads an image of a document conveyed to an image reading region, and a detection unit that detects the size of the document. This detection means detects the size of the document before the reading means starts reading the image.

  The image forming apparatus includes: an area setting unit configured to set the image reading area as a passing area through which a conveyed document passes and a non-passing area through which the conveyed document passes according to the size of the document detected by the detecting unit; Image density detecting means for detecting whether or not the density of the image read in the non-passing area is constant.

  When the original is conveyed to the image reading area in a normal state (that is, in a state parallel to the conveyance direction), the original passes only through the passing area and does not pass through the non-passing area. In this case, the image density read in the non-passing area does not change, and a constant image density is maintained. On the other hand, when the document is transported to the image reading area in an inclined state, the document passes through not only the passing area but also the non-passing area. In this case, the image density read in the non-passing area changes because the original passes. As described above, when the image density detecting unit detects whether the image density of the non-passing area is changed, the original is conveyed to the image reading area in a normal state or is inclined obliquely. It can be detected whether it is conveyed.

  Further, the image forming apparatus includes a reading stop unit that stops reading of the image of the document by the reading unit based on the detection result of the image density detecting unit. When the image density detecting unit detects a change in the image density in the non-passing area, that is, when the document is being conveyed obliquely, the image reading is stopped.

  Thereby, it is possible to prevent a useless reading operation of reading an image of a document conveyed in an inclined state. Further, the image density detecting means can also be used as a detecting means for detecting the image density read in the passage area. Since the image forming apparatus is provided with means for detecting the image density of the normal passing area, it is possible to prevent the installation of a new sensor or the like by using it as well.

  According to the image forming apparatus of the present invention, it is possible to detect an oblique conveyance without providing a new member, thereby reducing the cost and accurately reading an image of a document instead of a distorted state. Can be provided.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In this embodiment, the present invention is embodied as a digital multi-function peripheral having an automatic document feeder (ADF (Auto Document Feeder)).

  FIG. 1 is a diagram illustrating an example of the overall configuration of a digital multifunction peripheral according to the present embodiment. The multifunction machine 101 includes an image reading unit 102 and an image forming unit 103. The image reading unit 102 reads an image of a document and generates digital data of the image. The image reading unit 102 is provided with a document table 104 made of a transparent plate such as contact glass, and a document can be placed on the document table 104.

  A scanning optical system 105 including a first carriage 106, a second carriage 107, a condenser lens 108, and the like is disposed below the document table 104. The first carriage 106 is provided with a linear light source 109 and a mirror 110, and the second carriage 107 is provided with mirrors 111 and 112. When the light source 109 illuminates the document, the reflected light is guided to the lens 108 via the mirrors 110, 111, and 112. The lens 108 forms the optical image on the light receiving surface of the line image sensor 113. In the scanning optical system 105, the first carriage 106 and the second carriage 107 are provided so as to be able to reciprocate in the sub-scanning direction 114. By moving the first carriage 106 and the second carriage 107 in the sub-scanning direction 114, the image of the document placed on the document table 104 can be read by the image sensor 113. The image sensor 113 generates document image data from the light image incident on the light receiving surface.

  Further, a white reference plate 136 is provided on the upstream side in the movement direction of the first carriage 106 from the original reading start point of the original table 104. Based on the density data read from the white reference plate 136, for example, a shading correction reference can be set.

  The user can also set a document on the automatic document feeder 115. The automatic document feeder 115 is attached to the upper side of the image reading unit 102 so as to be openable and closable, and includes a document tray 116, a conveyance path 117, and a discharge tray 118. The automatic document feeder 115 automatically feeds the sheets set on the document tray 116 one by one to the conveyance path 117. On the conveyance path 117, there is an image reading area 119 which is an area for the image reading unit 102 to read a document image. When reading an image of a document set on the automatic document feeder 115, the image reading unit 102 temporarily fixes the first carriage 106 and the second carriage 107 in accordance with the image reading area 119. When the document passes through the image reading area 119, the document is illuminated and an image of the document is read. The document that has passed through the image reading area 119 is discharged to the discharge tray 118.

  The image forming unit 103 prints image data obtained by the image reading unit 102 or image data received from an external device on a sheet. The image forming unit 103 is provided with a photosensitive drum 120 that rotates in the arrow direction 121 at a constant speed. Around the photosensitive drum 120, a charger 122, an exposure unit 123, a developing unit 124, a transfer unit 125, and a cleaning unit 126 are arranged in this order from the upstream side in the rotation direction. An exposure unit 123 irradiates light on the surface of the photosensitive drum 120 uniformly charged by the charger 122 according to image data, thereby forming an electrostatic latent image on the photosensitive drum 120. The developing device 124 attaches toner to the electrostatic latent image and forms a toner image on the photosensitive drum 120. The transfer unit 125 transfers the toner image on the photosensitive drum 120 to a sheet. The cleaning unit 126 cleans the surface of the photosensitive drum 120 by removing waste toner remaining on the surface of the photosensitive drum 120 after the transfer from the photosensitive drum 120. These processes are performed in a series as the photosensitive drum 120 rotates.

  The image forming unit 103 feeds paper from the manual feed tray 127 and the paper feed cassette 128 to the transfer unit between the photosensitive drum 120 and the transfer unit 125. Various sizes of paper can be placed or stored in the manual feed tray 127 or each paper feed cassette 128. The image forming unit 103 selects a sheet specified by the user or a sheet corresponding to the automatically detected document size, and pulls out the selected sheet from the manual feed tray 127 or the cassette 128 by the feeding roller 129. The drawn paper is sent to the transfer unit by the conveyance roller 130 and the registration roller 131. The sheet on which the toner image is transferred is conveyed to the fixing device 132. The fixing device 132 includes a fixing roller 133 and a pressure roller 134, and fixes the toner image on the sheet by heat and pressing force. The image forming unit 103 discharges the sheet that has passed through the fixing device 132 to the discharge tray 135.

  FIG. 2 is a cross-sectional view showing an example of the mechanical configuration of the automatic document feeder in more detail. The automatic document feeder 115 includes a pickup roller 201, a feeding belt 202, and a separation roller 203 for separating the documents one by one from the document bundle placed on the document tray 116. The pickup roller 201 is pressed against the tip of the uppermost surface of the document bundle. By driving the pickup roller 201 in this state, the original is pulled out from the original bundle. Even if there are two or more drawn documents, the first document is separated from the documents by the feeding belt 202 and the separation roller 203 and conveyed to the downstream side of the conveying path 117. A registration roller 204 and a conveyance roller 205 are provided downstream thereof. The timing at which the registration roller 204 conveys the image to the image reading area 119 is adjusted, and the conveying roller 205 conveys the document to the image reading area 119. The image of the original is read in the image reading area 119. The document that has passed the image reading area 119 is discharged from the discharge portion to the discharge tray 118 by the discharge roller 207.

  The document tray 116 is provided with a document set detection sensor 208, a document trailing edge detection sensor 209, and a document width detection sensor 210. Document set detection sensor 208 detects the presence or absence of documents on document tray 116. When the document set detection sensor 208 detects a document, the automatic document feeder 115 raises the document tray 116 and presses the uppermost surface of the document bundle against the pickup roller 201. The detection result of the document set detection sensor 208 is also used to confirm completion of feeding of the document set on the document tray 116.

  The document trailing edge detection sensor 209 is provided in the middle of the document tray 116 and detects whether the size of the document set on the document tray 116 is a half size. The document trailing edge detection sensor 209 detects a document of the same size when the document is set in the vertical direction and does not detect when the document is set in the horizontal direction.

  Further, a document width detection sensor 210 is provided below the document tray 116. The document width detection sensor 210 detects the width of the document by detecting the position of the width direction regulating plate that arranges the document on the document tray 116 in the width direction. The document width detection sensor 210 can detect whether the size of the document is A type size (A4 size, A5 size, etc.) or B type size (B4 size, B5 size, etc.). Based on the detection results of the document trailing edge detection sensor 209 and the document width detection sensor 210, information on the size of the document can be obtained when the document is placed on the document tray 116.

  FIG. 3 is a hardware configuration diagram of a control system in the multifunction machine.

  The multifunction machine 101 includes a CPU (Central Processing Unit) 301, a RAM (Random Access Memory) 302, a ROM (Read Only Memory) 303, an HDD (Hard Disk Drive) 304, and a driver 305 corresponding to each drive unit in the printing process. Are connected via an internal bus 306. The CPU 501 uses, for example, the RAM 502 as a work area, executes programs stored in the ROM 303, the HDD 304, and the like, and exchanges data and commands with the driver 305 based on the execution results, thereby allowing each of the drive units to Control the behavior.

  The multifunction machine 101 also includes a touch panel display 307 that displays information set by the user and notifies the user of a message. For example, when a signal indicating that there is no paper in the paper cassette is transmitted to the CPU, the CPU displays a message “please store paper in the paper cassette” on the display 307.

  Further, in the multifunction machine 101, a document set detection sensor 208, a document trailing edge detection sensor 209, and a document width detection sensor 210 of the automatic document feeder 115 are connected via the internal bus 306. The CPU 301 inputs signals from these various sensors, and controls the operation of each means shown in FIG. 4 below by executing a program stored in, for example, the ROM 303 in accordance with the input signals.

  FIG. 4 is a functional block diagram of the MFP according to the present embodiment. FIG. 5 is a perspective view showing an upper appearance of the multifunction machine according to the present embodiment.

  The document size detection unit 401 receives the signals from the document trailing edge detection sensor 209 and the document width detection sensor 210 to detect the size of the document placed on the document tray. The document size information is notified to the area setting unit 402.

  When the area setting unit 402 receives information about the document size from the document size detection unit 401, the area setting unit 402 sets the image reading area 119 as a passing area where the document passes and a non-passing area where the document does not pass.

  As shown in FIG. 5, the passage area 501 is an area through which a reading surface (a surface on which an image is formed) of a document passes when the document is read. The image reading unit 102 reads an image of a document in the passage area 501. The passage area is set by receiving information on the size of the document from the document size detection unit 402 when the document is set on the document tray. Specifically, information that correlates the size of the document and the passage area on a one-to-one basis is described in, for example, a ROM, and the passage area corresponding to each size of the document is determined by referring to this information. Can be done. Note that the width 501A of the passage area 501 is at least longer than the length in the width direction of the document (direction perpendicular to the document conveyance direction) so that the image reading unit can read the image of the document that has passed through the passage area 501. Is set.

  The non-passing area 502 is set at a position near both sides of the passing area 501 in a direction orthogonal to the document transport direction. When the document is normally transported (that is, when transported in parallel with the transport direction (hereinafter referred to as parallel transport)), the document does not pass through the non-passing area 502 as shown in FIG. 6A. On the other hand, when the document is conveyed obliquely (hereinafter referred to as oblique conveyance), a portion of the document that is inclined passes through the non-passing area 502 as shown in FIG. 6B.

  Thus, when the pass region 501 and the non-pass region 502 are set by the region setting unit 402, the density detection unit 403 subsequently detects the image density in these regions. Here, the density detection unit 403 of the present embodiment measures the image density not only in the passing area 501 but also in the non-passing area 502. Hereinafter, a method in which the density detection unit 403 measures the image density of the passing area 501 and the non-passing area 502 when the document is conveyed to the image reading area will be described.

  In detecting the image density of the document, the density detection unit 403 first generates a white reference density necessary for shading correction or the like. The shading correction is a process for removing unevenness from an image with uneven density according to the position of the pixel, and color unevenness for each pixel can be corrected by referring to the white reference density. The white reference density data (white reference data) serving as the white reference value for each pixel is measured based on the intensity of the light reflected by irradiating the white reference plate with light.

  Then, the intensity of the reflected light is measured by irradiating the document conveyed to the image reading area with light. Based on the ratio between the intensity of the reflected light from the original image and the intensity of the reflected light from the white reference plate, the density of the original image is measured.

  As described above, the image density of the passing area 501 and the non-passing area 502 is measured. Here, as shown in FIG. 6A, when the document is conveyed in parallel in the image reading area 119, the document passes only through the passing area 501 and does not pass through the non-passing area 502. In this case, the image density of the non-passing area 502 remains constant without changing.

  On the other hand, as shown in FIG. 6B, when the document is transported obliquely in the image reading area 119, the document passes through the non-passing area 502 as well as the passing area 501. Become. In this case, the image density of the non-passing area 502 changes as the document passes.

  When the image density read in the non-passing area 502 is constant, the image reading unit 102 detects the image density of the passing area as usual, and continues reading the image. On the other hand, when the image density read in the non-passing area 502 is not constant, the reading stop unit 404 stops reading the image by the image reading unit 102.

  If the image density read in the non-passing area 502 is not constant, the display unit 405 can display a message on the display 307 indicating that the image reading is interrupted or that the document is conveyed obliquely. As a result, the user can be alerted to accurately set the original being conveyed obliquely on the original tray.

  FIG. 7 is a diagram illustrating an example of a control procedure executed by the control unit.

  First, the user sets a document on a document tray of the automatic document feeder. The automatic document feeder checks whether the document set detection sensor detects that a document is placed on the document tray (S1). When it is confirmed that the document is placed (when the determination in S1 is YES), the document size detection unit reads information on the size of the document detected by the document trailing edge detection sensor and the document width detection sensor (S2). . When information about which size paper such as A4 or A5 corresponds to the size of the original on the original tray is obtained, the area setting unit sets the image reading area as a passing area and a non-passing area based on the information (S3). ).

  When the user presses the start key for copying (S4), the density detection unit first generates white reference data that serves as a reference value for image density (S5).

  Subsequently, the document on the document tray is transported to the downstream side of the transport path (S6). When the document is conveyed to the image reading area, it is detected by the density detection unit whether the image density in the non-passing area is constant (S7).

  When the density detection unit detects that the image density has changed in the non-passing area, the document is regarded as being conveyed obliquely (when the determination in S7 is YES), and the display unit is displayed on the display. A message indicating that the document is being conveyed obliquely is displayed (S8). For example, a message “Original is being conveyed at an angle. Reading operation is interrupted.” Is displayed on the display. Further, the reading stop unit interrupts the reading operation of the image reading unit (S9).

  On the other hand, if no change in image density is detected in the non-passing area, the CPU determines that the document is being conveyed normally. In this case (when the determination in S7 is NO), the image reading unit continues the reading operation as usual (S10).

  As described above, it is possible to detect whether or not the document is conveyed obliquely based on whether or not the image density has changed in the non-passing area. If the document is being conveyed obliquely, the user is notified of the fact and the reading operation is stopped, thereby preventing unnecessary reading of the original image. In the present embodiment, detection of image density in a passing area, which has been conventionally used, is also applied to a non-passing area. For this reason, it is not necessary to separately install a sensor or the like for detecting the oblique conveyance of the document, and there is an advantage of suppressing an increase in cost.

  The embodiments described above do not limit the technical scope of the present invention, and various modifications and applications other than those already described are possible within the scope of the present invention. For example, in order to detect a document on the document tray of the main body, a document detection sensor such as a reflective optical sensor may be separately provided in the image reading unit.

  The image forming apparatus according to the present invention is useful for various devices such as a multifunction machine including an automatic document feeder, a printer, a facsimile machine, and a multifunction machine.

1 is an overall configuration diagram of a multifunction machine according to an embodiment. 1 is a cross-sectional view of a mechanical configuration of an automatic document feeder according to an embodiment. FIG. 2 is a hardware configuration diagram of the multifunction peripheral according to the present embodiment. FIG. 3 is a functional block diagram of the multifunction machine according to the present embodiment. FIG. 3 is a perspective view showing an upper appearance of the multifunction machine according to the embodiment. The figure which shows the reading position when a manuscript passes at the time of image reading. The figure which shows an example of the control procedure which the control part of this embodiment performs.

Explanation of symbols

101 MFP 102 Image Reading Unit 103 Image Forming Unit 115 Automatic Document Feeding Device 116 Document Tray 119 Image Reading Area 208 Document Set Detection Sensor 209 Document Trailing Edge Detection Sensor 210 Document Width Detection Sensor 401 Document Size Detection Unit 402 Area Setting Unit 403 Density detection unit 404 Reading stop unit 405 Display unit 501 Passing area 502 Non-passing area

Claims (2)

Reading means for reading an image of the document conveyed to the image reading area;
Detection means for detecting the size of the document;
Area setting means for setting the image reading area as a passing area through which the conveyed document passes and a non-passing area through which the conveyed document passes according to the size of the document detected by the detecting means;
Image density detecting means for detecting whether or not the density of the image read in the non-passing region is constant;
A reading stop means for stopping reading of an image of the original by the reading means based on a detection result of the image density detecting means;
An image forming apparatus comprising: The image forming apparatus according to claim 1, further comprising a notification unit configured to notify the user of a message when the image density detection unit detects that the image density is not constant in the non-passing region.

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