JP2009118377A - Image reading device and image forming apparatus equipped with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading device and an image forming apparatus equipped with it capable of accurately detecting a document width even though the document is dark or thick. <P>SOLUTION: A control part 70 performs first detection that detects an output signal from a CCD 58 when an opening/closing detection switch 43 is turned OFF from ON so as to obtain information of a document area, and further performs second detection when the opening/closing detection switch 43 is continuously OFF after the predetermined time has elapsed. When there is an area in which an output signal difference transmitted from the CCD 58 at the first detection and the second detection is a predetermined value or more, the area in which the output signal difference is the predetermined value or more is determined as an area outside of the document, and the area in which the difference is smaller than the predetermined value is determined as the manuscript area so as to determine a document width size. When the output signal difference is smaller than the predetermined value in the entire area, a boundary line in which the output signal difference (light intensity difference) from the information of the document area at the first detection is the threshold or less is determined so as to determine the width size of the document. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image reading apparatus used for a digital copying machine, an image scanner, and the like, for scanning and reading a document, and an image forming apparatus including the image reading apparatus.

  2. Description of the Related Art Conventionally, in a mirror scanning type copying machine or the like, a document is placed on a contact glass of a document reading unit, and a scanning unit composed of an illumination unit and a mirror unit provided below the contact glass is scanned by a predetermined driving device. 2. Description of the Related Art Image reading apparatuses that read a document image by moving (scanning) parallel to a surface are widely used.

  A copying machine equipped with such an image reading apparatus has an automatic document size detection function using the image reading apparatus. This function is executed by the following procedure, for example. First, after placing the document at a predetermined position on the contact glass and closing the document pressing plate, or before closing the document, the light source of the illumination unit is emitted to irradiate the document image. Reflected light from the original enters a photoelectric conversion element (hereinafter referred to as CCD) via a mirror unit and is converted into an electrical signal. Then, a portion where the output signal from the CCD changes greatly is determined as the boundary between the document area and the document outside area, and the document width is determined by comparing with the document width data stored in advance.

  However, in the automatic document size detection function as described above, in order to improve the size detection speed and reduce the amount of processing information, the size detection operation is usually performed only in a part of the document scanning direction (length direction). . For this reason, for example, when a black (dark color) area and a white area coexist at the edge of the document, there is a possibility that the boundary between the document area and the document outside area may not be accurately determined depending on the size detection location.

Therefore, a method for accurately detecting the size of the document regardless of the color or pattern of the document has been proposed. In Patent Document 1, the first scan is performed in a state where the platen cover (document pressing plate) is not closed. Next, the second scanning is performed with the platen cover completely closed, and the outermost candidate among the document edge candidates obtained by the first and second scanning is adopted to adopt the document width size. An image reading apparatus is disclosed that determines the above.
Japanese Patent No. 3592046

  However, in the method of Patent Document 1, for example, when a thick original such as a book is placed on the contact glass, the platen cover cannot be completely closed, and the second scan cannot be executed. It was. Further, it is described that when the copy operation is started with the platen cover opened, the document size may be detected only by the first scan. However, if the platen cover is opened even a little, the second is detected. Since scanning is not executed, there is a problem that it is difficult to detect an accurate document size when, for example, the edge of the document is dark.

  In view of the above problems, an object of the present invention is to provide an image reading apparatus capable of accurately detecting the original width even for a thick original and an image forming apparatus including the same.

  In order to achieve the above object, the present invention provides a document table having a contact glass fixed on the upper surface, a document holding plate supported at one end of the document table so as to be openable and closable, a light source for illuminating the document, and a document. And a mirror unit that includes a mirror that changes the optical path of the image light, and moves inside the document table at a constant scanning speed. In an image reading apparatus comprising: a scanning unit; a photoelectric conversion element that converts image light guided by the scanning unit into an electrical signal; and a control unit that reads an electrical signal output from the photoelectric conversion element as image data. The control means moves the illumination unit and the mirror unit to a predetermined detection position, and then when the opening angle of the document pressing plate becomes a predetermined angle or less, And sequentially executing a first detection for detecting an output signal from the photoelectric conversion element and a second detection for detecting an output signal from the photoelectric conversion element after a predetermined time from the first detection. When there is an area where the difference between the output signals in the first and second detections is greater than or equal to a predetermined value, the area is determined as an area outside the original, the original width is determined, and the output signal difference exceeds the predetermined value over the entire area. Is smaller, the document width is determined by determining the boundary between the document area and the document outside area from the output signal detected by the first detection.

  According to the present invention, in the image reading apparatus having the above-described configuration, the document pressing plate is in a predetermined opening detection position or a first position in a closing direction with respect to the opening detection position in a full opening range, or the opening detection position. An open / close detection switch is provided for detecting whether the document holding plate is in the second position in the opening direction, and the first detection is performed when the document pressing plate is moved from the second position to the first position. It is characterized by doing.

  According to the present invention, in the image reading apparatus configured as described above, the scanning unit moves from the reference position to the detection position when the document pressing plate moves from the first position to the second position. It moves from the detection position to the reference position immediately after the second detection is executed.

  According to the present invention, in the image reading apparatus configured as described above, when the control unit moves the first pressing plate to the second position before executing the second detection after executing the first detection. Is characterized in that the document width is not determined.

  According to the present invention, in the image reading apparatus having the above-described configuration, the open / close detection switch includes a detection auxiliary member that reciprocates in conjunction with opening and closing of the document pressing plate, and an optical path is blocked by the reciprocation of the detection auxiliary member. Or it is characterized by comprising a photo interrupter that is opened.

  According to the present invention, in the image reading apparatus configured as described above, the opening detection position is set such that an angle of the document pressing plate with respect to the document table is in a range of 20 ° to 30 °.

  The present invention also provides an image forming apparatus equipped with the image reading apparatus having the above-described configuration.

  According to the first configuration of the present invention, when reading a sheet-like document, document region information can be detected in two stages of first detection and second detection to determine the width size of the document. The size detection accuracy is higher even for the original. When reading a thick document, even if the document pressing plate is not completely closed, if there is a region where the output signal difference between the first detection and the second detection is greater than or equal to a predetermined value, both detection results are displayed. By using this, the width size of the document can be accurately determined.

  According to the second configuration of the present invention, in the image reading apparatus having the first configuration, the document pressing plate is a predetermined opening detection position in the full opening range or a first direction closer to the opening detection position than the opening detection position. An open / close detection switch is provided for detecting whether the document holding plate is in the position or in the second position in the opening direction relative to the opening detection position, and the first detection is performed when the document pressing plate moves from the second position to the first position. By executing, the first detection can be executed when the document pressing plate is always at a constant opening angle, and the detection accuracy can be improved.

  According to the third configuration of the present invention, in the image reading apparatus having the second configuration, the scanning unit moves to the detection position when the document pressing plate moves from the first position to the second position. By returning to the reference position immediately after the second detection is performed, the user automatically moves to the detection position when the user releases the document pressing plate to place the document, and automatically after the second detection is completed. Since reading can be started immediately after returning to the position, the waiting time of the user accompanying detection of the document width size can be reduced as much as possible.

  According to the fourth configuration of the present invention, in the image reading apparatus having the second or third configuration, the document pressing plate is in the second position after the first detection is performed and before the second detection is performed. Since the document width is not determined when the position is moved, useless size detection can be omitted when reading is stopped and the document pressing plate is opened.

  According to the fifth configuration of the present invention, in the image reading apparatus having any one of the second to fourth configurations, the detection auxiliary member that reciprocates in conjunction with opening and closing of the document pressing plate, and the detection By configuring an open / close detection switch with a photo interrupter whose optical path is blocked or opened by the reciprocating movement of the auxiliary member for use, the position of the document pressing plate can be detected with a simple configuration.

  According to the sixth configuration of the present invention, in the image reading apparatus having any one of the second to fifth configurations, the angle of the document pressing plate with respect to the document table is opened in the range of 20 ° to 30 °. By setting the detection position, even in the case of a dark original, the output signal difference between the original area and the original outside area can be detected in the first detection. In addition, since the difference in the amount of reflected light from the outside area of the document when the second detection is performed increases, it is possible to prevent erroneous size detection, and the amount of lifting of the document pressing plate from the document mounting table is large. However, the area outside the document can be determined. Furthermore, dazzling due to leakage of light from the light source and reduction in detection accuracy due to incidence of room light can be suppressed.

  Further, according to the seventh configuration of the present invention, by mounting the image reading apparatus having any one of the first to sixth configurations on the image forming apparatus, the width size of a dark or thick document can be accurately adjusted. Provided is an image forming apparatus capable of accurately selecting an optimal sheet by reading.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing the internal configuration of an image forming apparatus equipped with the image reading apparatus of the present invention. In FIG. 1, in an image forming apparatus 100 (here, a digital multi-function peripheral is shown as an example), when performing a copying operation, an image reading apparatus 6 converts image data of a document into a read image signal. On the other hand, in the image forming unit 3 in the multifunction machine main body 2, the charging unit 4 uniformly charges the small-diameter photosensitive drum 5 rotating in the direction A in the drawing, and the original image data read by the image reading device 6. An electrostatic latent image is formed on the photosensitive drum 5 by a laser beam from an exposure unit (laser scanning unit or the like) 7 based on the above, and a developer (hereinafter referred to as toner) is attached to the electrostatic latent image by the developing unit 8. Thus, a toner image is formed. The toner is supplied to the developing unit 8 from the toner container 9.

  The sheet is conveyed from the sheet feeding mechanism 10 to the image forming unit 3 via the sheet conveying path 11 and the registration roller pair 12 toward the photosensitive drum 5 on which the toner image is formed as described above. 3, the toner image on the surface of the photosensitive drum 5 is transferred to the sheet by the transfer roller 13 (image transfer unit). The sheet on which the toner image has been transferred is separated from the photosensitive drum 5 and conveyed to a fixing unit 14 having a fixing roller pair 14a to fix the toner image. The sheet that has passed through the fixing unit 14 is sent to a sheet conveyance path 15 branched in a plurality of directions, and is conveyed in a conveyance direction by path switching mechanisms 21 and 22 having a plurality of path switching guides provided at branch points of the sheet conveyance path 15. Are distributed as they are (or after being sent to the paper conveyance path 16 and double-sided copying), and discharged to the paper discharge section including the first discharge tray 17a and the second discharge tray 17b.

  Although not shown, a static elimination device that removes residual charges on the surface of the photosensitive drum 5 is provided on the downstream side of the cleaning device 18. Further, the paper feed mechanism 10 is detachably attached to the multifunction machine main body 2 and includes a plurality of paper feed cassettes 10a and 10b for storing paper and a stack bypass (manual feed tray) 10c provided above the paper feed cassettes 10a and 10b. These are connected to the image forming unit 3 including the photosensitive drum 5 and the developing unit 8 by the paper transport path 11. Reference numeral 24 denotes a platen (original presser) that presses and holds an original placed on the image reading unit 6.

  Specifically, the sheet conveyance path 15 first branches into a left and right fork on the downstream side of the fixing roller pair 14a, and one path (a path branching rightward in FIG. 1) communicates with the first discharge tray 17a. It is configured as follows. The other path (the path that branches in the left direction in FIG. 1) branches into the upper and lower forks via the conveying roller pair 19, and the other path (the path that branches in the upper direction in FIG. 1) is the second discharge tray. It is comprised so that it may communicate with 17b. On the other hand, the other path (the path that branches downward in FIG. 1) is configured to communicate with the sheet conveyance path 16.

  FIG. 2 is a side view of the image reading apparatus of the present invention. The image reading device 6 includes a contact glass 35 provided on the upper surface (document placement table) of the apparatus body, and a platen 24 that presses and holds the document D placed on the contact glass 35. The platen support portion 37 provided on the side of the apparatus main body is supported so as to be opened and closed in the vertical direction. In addition, a white mat 39 that directly presses the document D is provided on the back surface of the platen 24. When the platen 24 is closed, the white mat 39 can press the document D uniformly against the contact glass 35. It is like that.

  Further, the platen support portion 37 is provided with a PI (photo interrupter) sensor 40 made of a light emitting photodiode for detecting the open / closed state of the platen 24, and is provided between the apparatus main body and the platen support portion 37. The auxiliary member for detection 41 and the PI sensor 40 constitute an open / close detection switch 43. That is, as shown in FIG. 2, the upper end portion 41 a of the detection auxiliary member 41 has a platen 24 in a state where the platen 24 is completely covered with the contact glass 35 and opened more than a predetermined angle (angle θ in the figure). However, when it is closed to a position opened by an angle θ (hereinafter referred to as an open detection position), it contacts the platen 24 and moves downward. The auxiliary member 41 moves up and down.

  When the platen 24 is more open than the angle θ, the protrusion 41b formed on the auxiliary detection member 41 shields the PI sensor 40 and generates a signal. That is, the switch by the PI sensor 40 is in the OFF state from the state in which the platen 24 completely covers the contact glass 24 to the open detection position (hereinafter referred to as the first position), and is in the open state (hereinafter referred to as the open detection position). , Referred to as the second position).

  FIG. 3 is a schematic plan view showing the internal structure of the image reading apparatus of the present invention. In FIG. 3, between the left and right side surfaces 6a and 6b of the image reading device 6, a pair of guide rails 45 are installed in parallel with the contact glass 35 (see FIG. 2) on the upper surface of the device. An illumination unit 47 and a mirror unit 49 are placed on the pair of guide rails 45. In the vicinity of the right side surface 6a, a drive shaft 50 that can be rotated forward and reversely by a unit drive motor (not shown) is disposed so as to be orthogonal to the guide rail 45, and is positioned outside the guide rail 45. A drive pulley 51 having a large diameter portion and a small diameter portion is attached to both ends of the drive shaft 50. Further, in the vicinity of the left side surface 6b, a support shaft 53 having a driven pulley 52 having the same diameter as that of the drive pulley 51 is disposed at both ends.

  A driving wire 54 a is stretched over the large diameter portions of the driving pulley 51 and the driven pulley 52, and similarly, a driving wire 54 b is stretched over the small diameter portion of the driving pulley 51 and the driven pulley 53. Yes. A part of the illumination unit 47 is fixed to the drive wire 54a, and a part of the mirror unit 49 is fixed to the drive wire 54b. Two contactors 55 are provided at the portion where the illumination unit 47 and the mirror unit 49 are in contact with the upper surface of the guide rail 45, and the contact surface of each contactor 55 with the guide rail 45 is a spherical surface. .

  When the drive shaft 50 is rotated by the unit drive motor and the drive wires 54a and 54b are rotated, the illumination unit 47 and the mirror unit 49 are moved along the guide rail 45 in the scanning direction (left-right direction in the figure). Here, since the diameter ratio of the large diameter portion and the small diameter portion of the drive pulley 51 and the driven pulley 52 is 2: 1, the ratio of the moving distance between the illumination unit 47 and the mirror unit 49 is also 2: 1.

  Further, a plate-like support member (hereinafter referred to as ISU base) 56 is attached between the front and rear frames of the image reading device 6, and a condensing lens 57 and a photoelectric as reading means are provided on the upper surface of the ISU base 56. A conversion element (hereinafter referred to as CCD) 58 is mounted. The image reading device 6 includes control clock means (not shown) that generates a control clock based on the reference clock input from the oscillating means, and controls the driving of the CCD 58 by this control clock.

  The condenser lens 57 is installed on a lens support base 59, and the lens support base 59 is fixed to the ISU base 56. Reference numeral 60 denotes a guide member that is movably supported by the lens support base 59, and a CCD substrate 61 that controls the driving of the CCD 58 is fixed to the back surface of the guide member 60. An opening window 60 a through which the image light condensed by the condenser lens 57 passes is provided near the center of the guide member 60. The CCD 58 is mounted on the CCD substrate 61, and the optical axis incident on the CCD 58 can be corrected by finely adjusting the position of the guide member 60. Further, an optical sensor 62 is provided at a predetermined position inside the apparatus, and the longitudinal direction of the document (left-right direction in FIG. 3) depends on whether or not the reflected light from the document placed on the contact glass 35 is received. Detect the size of.

  When reading a document image, the illumination unit 47 illuminates the document with the light source of the illumination unit 47, the illumination unit 47 moves in the direction of arrow A at a predetermined speed, and the mirror unit 49 has the same speed as the half of the illumination unit 47. Move in the direction. As a result, the image light formed by the illumination of the illumination unit 47 is guided to the condenser lens 57 by the mirror unit 49, and after being condensed, passes through the opening window 60a of the guide member 60 and forms an image on the CCD 58. The The imaged image light is subjected to pixel decomposition in the CCD 58, converted into an electrical signal corresponding to the density of each pixel, and an image is read.

  4 is a view of the image reading apparatus of FIG. 3 as viewed from the front side (lower side of FIG. 4). For convenience of explanation, the guide rail 45, the driving pulley 51, the driven pulley 52, and the driving wires 54a and 54b are not shown. In FIG. 4, a contact glass 35 is provided on the upper surface of the image reading device 6, and a document (not shown) scanned by the illumination unit 47 and the mirror unit 49 is placed face down on the contact glass 35. Is done. When scanning an original, first, the illumination unit 47 and the mirror unit 49 are moved from the home position (left end in FIG. 4) to the scanner return side (right side in FIG. 4). At the same time, the original is irradiated with light from the light source 47 a of the illumination unit 47.

  The reflected light from the original is changed in its optical path by the mirror 47b and the mirrors 49a and 49b of the mirror unit 49, and then passes through the condenser lens 57 and the opening window 60a to form an image on the CCD 58 (the one-dot chain line in the figure). . The moving distance of the mirror unit 49 in this scanning is ½ of the moving distance of the illumination unit 47 as described above, and the optical path length from the document surface to the CCD 58 is kept constant.

  FIG. 5 is a block diagram illustrating an example of a control path of the image reading apparatus. The control unit 70 controls the driving of the illumination unit 47 and the mirror unit 49 by transmitting a control signal to the unit drive motor 71 according to the set program. Further, as will be described later, it also serves as means for discriminating between the document area and the document outside area based on the electrical signal transmitted from the CCD 58 and automatically detecting the document width size. The storage unit 73 stores a basic program used in the control unit 70, and also stores a threshold value of an output signal difference from the CCD 58 when discriminating a document area and a document outside area.

  FIG. 6 is a flowchart showing a procedure for determining the document width size. The automatic determination control of the document width size by the image reading apparatus will be described in detail along the steps of FIG. 6 with reference to FIGS. First, when the platen 24 is opened to the second position by the user (step S1), the open / close detection switch 43 including the PI sensor 40 and the auxiliary detection member 41a is turned on (step S2). The controller 70 moves the illumination unit 47 and the mirror unit 49 from the home position (reference position) to the size detection position at the timing when the ON signal of the open / close detection switch 43 is received (step S3). This size detection position is set in a range that overlaps the minimum size document (for example, A5 size) placed on the contact glass 35.

  Then, when a document is set on the contact glass 35 by the user (step S4) and the platen 24 is gradually closed from the open state (step S5), the open / close detection switch 43 is turned off when the open / close detection position is closed. (Step S6). The control unit 70 turns on the light source 47a of the illumination unit 47 at the timing when the OFF signal of the open / close detection switch 43 is received (step S7). Light emitted from the light source 47 a is reflected by the document to become image light, and enters the CCD 58 through the mirror unit 49. The control unit 70 detects the output signal from the CCD 58 and performs first detection for acquiring document area information (step S8).

  FIG. 7 shows a state where the document D is set on the contact glass 35 and the illumination unit 47 and the mirror unit 49 are moved to the size detection position. In the region where the document D exists (document region), the light emitted from the light source 47a of the illumination unit 47 is reflected by the document D, so that the amount of light incident on the CCD 58 increases, and the output signal detected by the control unit 70 is also large. (Detected as low concentration). On the other hand, in the area where the document D does not exist (outside the document, hatched portion in FIG. 7), the light emitted from the light source 47a is radiated to the outside through the contact glass 35. Therefore, the output detected by the control unit 70 The signal is small (detected as high concentration). In the first detection, document area information is acquired using this output signal difference. The acquired document area information is stored in the storage unit 73.

  Next, it is determined whether or not the open / close detection switch 43 continues in the OFF state after a predetermined time (here, 2 seconds after the start of switch OFF) (step S9). 2 is opened, the image reading operation is determined to have been interrupted, the light source 47a is turned off (step S10), and the determination of the document width size is stopped (step S11). When the OFF state continues, since the platen 24 is in the first position, the control unit 70 performs the second detection for detecting the output signal from the CCD 58 (step S12). Thereafter, the light source 47a is turned off (step S13), and the illumination unit 47 and the mirror unit 49 are returned to the home position in preparation for the subsequent reading operation.

  After execution of the second detection, the control unit 70 reads out the document region information acquired by the first detection from the storage unit 73, and the region where the light amount difference (output signal difference) between the first detection and the second detection is equal to or greater than a predetermined value. It is determined whether or not there is (step S14). When the original is a thin sheet, the platen 24 completely covers the contact glass 35 when the second detection is performed, so that the light emitted from the light source 47a is reflected by the white mat 39 even in the area outside the original. And enters the CCD 58. Therefore, the output signal from the CCD 58 becomes larger than that in the first detection when the white mat 39 is not present in the area outside the document. On the other hand, in the original area, there is no difference in the amount of reflected light from the original at the time of the first and second detections, so the output signal from the CCD 58 does not change.

  Accordingly, if there is an area where the difference between the output signals transmitted from the CCD 58 between the first detection and the second detection is greater than or equal to a predetermined value, the area is determined as an area outside the original, and an area smaller than the predetermined value is determined as the original area Is determined (step S15). Then, the document width size is determined based on the document area information (step S16).

  Further, for example, in the case of a document having a thickness such as a book, since the platen 24 is lifted from the contact glass 35 when the second detection is performed, a part of the light emitted from the light source 47a and passing through the contact glass 35 is The ratio of the light emitted to the outside in the area outside the original and reflected by the white mat 39 is lowered. As a result, the reflected light incident on the CCD 58 decreases and the output signal from the CCD 58 also decreases. In other words, when the opening angle of the platen 24 exceeds a predetermined angle due to the thickness of the document, the difference between the output signals transmitted from the CCD 58 during the first detection and the second detection over the entire region in the document width direction is greater than the predetermined value. Get smaller.

  In this case, a boundary line (a portion in which data from white to black continues continuously) having an output signal difference (light amount difference) equal to or less than a threshold is determined from the first detection document area information stored in the storage unit 73 (step). S17), based on this, the width size of the document is determined (step S16).

  By determining the document width size by the above-described control, when reading a sheet-like document, document region information can be detected in two stages of first detection and second detection to determine the document width size. Even if the edge portion is a dark original, the size detection accuracy becomes higher. Even if the platen 24 is not completely closed, if there is a region where the output signal difference from the CCD 58 exceeds a predetermined value between the first detection and the second detection, both the first and second detection results are detected. Can be used to determine the width size of the document, so that the width size can be accurately determined by two-step detection for documents other than extremely thick documents.

  Further, since the first detection is performed when the open / close detection switch 43 is turned from ON to OFF, that is, when the platen 24 is closed to a predetermined opening detection angle, the amount of light incident on the CCD 58 is always constant in the area outside the document. Thus, the document area information can be obtained with high accuracy in the first detection.

  In addition, since the illumination unit 47 and the mirror unit 49 automatically move to the size detection position when the open / close detection switch 43 is turned from OFF to ON, the first detection is performed when the open / close detection switch 43 is turned OFF next time. Can be executed immediately. Further, since the illumination unit 47 and the mirror unit 49 automatically return to the home position immediately after the end of the second detection, the subsequent reading operation can be immediately executed.

  The document density at which the boundary line of the document can be detected only by the first detection is determined by the opening angle (opening detection position) of the platen 24 when performing the first detection. If the opening angle is increased, the light reflected by the white mat 39 at the time of the first detection is reduced, so that it is possible to detect the output signal difference between the document area and the document outside area even for a dark document. it can. In addition, since the difference in the amount of reflected light from the area outside the original when the second detection is performed after the platen 24 is moved in the closing direction, the output signal difference threshold value can be widened. False detection can be prevented. Further, even when the platen 24 floats from the contact glass 35 is large, the area outside the document can be determined.

  However, if the opening angle of the platen 24 when performing the first detection is increased, the amount of light transmitted through the contact glass 35 and emitted to the outside increases, so that the user feels dazzling. In addition, indoor illumination light may pass through the contact glass 35 and enter the image reading device 6, which may affect detection accuracy. Therefore, it is preferable that the opening angle (angle θ in FIG. 2) of the platen 24 at the opening detection position is 20 ° or more and 30 ° or less.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, in the above-described embodiment, the image reading apparatus that aligns the document on the upper left of the contact glass has been described. However, an image reading apparatus that aligns the lower left or the left center may be used. In addition, although the dedicated control unit 70 for reading the electrical signal output from the CCD 58 as image data is provided, it can also be used as the control unit of the image forming apparatus main body.

  In addition, as an image forming apparatus on which the image reading apparatus of the present invention is mounted, only a digital multi-function peripheral is shown here. Of course, it can also be applied to an image scanner.

  In the image reading apparatus of the present invention, after the illumination unit and the mirror unit are moved to a predetermined detection position, the light source emits light when the opening angle of the document pressing plate is equal to or smaller than the predetermined angle, and an output signal from the photoelectric conversion element And a second detection for detecting an output signal from the photoelectric conversion element after a predetermined time from the first detection, and an output signal difference between the first and second detections is a predetermined value. When there is an area above, the area is determined as an area outside the original to determine the original width, and when the output signal difference is smaller than a predetermined value over the entire area, the original is determined from the output signal detected by the first detection. The document width is determined by determining the boundary between the area and the document outside area.

  As a result, the document width information can be determined by detecting the document area information in two stages of the first detection and the second detection, except for extremely thick documents. However, it is possible to provide an image reading apparatus capable of accurately detecting the width size. Further, since the document width can be determined from the result of the first detection even for an extremely thick document, the image reading apparatus can always detect an accurate width size except for an extremely thick document having a dark color.

  Also, by providing an open / close detection switch that switches between ON and OFF at a predetermined opening detection position, the first detection can be performed when the document pressing plate is at a certain opening angle, and the detection accuracy is improved. Further, if the opening detection position is set in a range where the angle of the document pressing plate with respect to the document placement table is 20 ° or more and 30 ° or less, even in the case of a dark document, the document area and the document outside area are detected in the first detection. The image reading apparatus can detect an output signal difference and can determine an area outside the original document in the second detection even for a thick original document. Furthermore, dazzling due to leakage of light from the light source and reduction in detection accuracy due to incidence of room light can be suppressed.

  In addition, by mounting the image reading apparatus of the present invention, it is possible to provide an excellent image forming apparatus that can reduce the occurrence of document width size detection failure and select an optimal size paper.

FIG. 1 is a schematic diagram illustrating an overall configuration of an image forming apparatus in which an image reading apparatus of the present invention is mounted. These are side views of the image reading apparatus of the present invention. These are the schematic plan views which looked at the drive mechanism of an image reading device from the upper part. These are the schematic side views which looked at the drive mechanism of the image reading apparatus from the side. FIG. 3 is a block diagram illustrating an example of a control path of the image reading apparatus. FIG. 5 is a flowchart showing a procedure for determining the width size of a document. FIG. 6 is a plan view showing a state in which an original is set on a contact glass of an image reading apparatus, and an illumination unit and a mirror unit are moved to a size detection position.

Explanation of symbols

2 MFP body 3 Image forming unit 6 Image reading device 24 Platen (document holding plate)
35 Contact glass 39 White mat 40 PI sensor 41 Detection auxiliary member 43 Open / close detection switch 47 Illumination unit (scanning means)
47a Light source 49 Mirror unit (scanning means)
58 CCD (photoelectric conversion device)
70 Control unit (control means)
73 Storage Unit 100 Image Forming Device D Document

Claims (7)

A document table with a contact glass fixed on the upper surface;
A document holding plate supported at one end of the document table so as to be openable and closable;
An illumination unit including a light source that illuminates the document and a mirror that guides reflected light from the document as image light, and a mirror unit that includes a mirror that changes the optical path of the image light. Scanning means for moving at a constant scanning speed;
A photoelectric conversion element that converts image light guided by the scanning means into an electrical signal;
In an image reading apparatus comprising a control means for reading an electrical signal output from the photoelectric conversion element as image data,
The control unit moves the illumination unit and the mirror unit from a reference position to a predetermined detection position, and then causes the light source to emit light when the opening angle of the document pressing plate becomes a predetermined angle or less, and the photoelectric conversion A first detection for detecting an output signal from the element and a second detection for detecting an output signal from the photoelectric conversion element after a predetermined time from the first detection are sequentially performed, and in the first and second detections, When there is an area where the output signal difference is greater than or equal to a predetermined value, the area is determined as an area outside the original to determine the original width, and when the output signal difference is smaller than the predetermined value over the entire area, the first detection is performed. An image reading apparatus that determines a document width by discriminating a boundary between a document region and a document outside region from the output signal detected in step (b).   Whether the document pressing plate is in a predetermined opening detection position or a first position in the closing direction with respect to the opening detection position or a second position in the opening direction with respect to the opening detection position in the entire opening range. 2. The image according to claim 1, wherein an open / close detection switch for detecting is provided, and the first detection is performed when the document pressing plate moves from the second position to the first position. Reader.   The scanning unit moves from the reference position to the detection position when the document pressing plate moves from the first position to the second position, and immediately after the second detection is performed, the detection position. The image reading apparatus according to claim 2, wherein the image reading apparatus moves from a reference position to the reference position.   The control means does not determine the document width when the document pressing plate is moved to the second position after the first detection and before the second detection is performed. The image reading apparatus according to claim 2 or 3.   The open / close detection switch includes a detection auxiliary member that reciprocates in conjunction with opening and closing of the document pressing plate, and a photo interrupter whose optical path is blocked or opened by the reciprocation of the detection auxiliary member. The image reading apparatus according to claim 2, wherein the image reading apparatus is an image reading apparatus.   6. The image reading according to claim 2, wherein the opening detection position is set such that an angle of the document pressing plate with respect to the document placing table is in a range of 20 ° to 30 °. apparatus.   An image forming apparatus on which the image reading apparatus according to claim 1 is mounted.

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