JP2007081536A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus capable of easily detecting the presence or absence of positional deviation of a line used for starting reading an image of an original document placed on an original platen, and automatically correcting the positional deviation. <P>SOLUTION: In the image reading apparatus 100, a reading unit 11 for reading an image for each line of a main scanning direction reads the original document on the original document platen 10 while scanning it in a sub-scanning direction. In the apparatus 100, grouped line segments consisting of line segments in which the number of line segments crossing a virtual line in a main scanning direction along the sub-scanning direction gradually increases or decreases are drawn so as to be separated in the sub-scanning direction from a reading start line F at which the reading unit 11 starts image reading of the original document. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus that scans a document placed on a document placing plate and reads an image.

  Some image reading apparatuses such as copiers and facsimile machines scan an image of a document placed on a document placing plate by scanning it. For example, in the conventional image reading apparatus 900 shown in FIG. 7, a document placement plate 902 is disposed on the top surface of the reading placement table 901, and the document placed on the document placement plate 902 is pressed and fixed. A document holding cover 903 that can be opened and closed is provided, and a reading unit 904 that includes a CCD (Charge Coupled Device) line sensor or the like is provided. The reading unit 904 is fixed to a belt 906 that is wound around a pulley 905, and the belt 906 is rotated by a driving force of a stepping motor 907, so that the reading unit 904 is positioned below the original platen plate 902. Are reciprocated in the sub-scanning direction (horizontal direction in the figure). Further, an auto document feeder (hereinafter referred to as “ADF”) 908 for automatically transporting the document placed on the document tray is provided in the document pressing cover 903. Such an image reading apparatus 900 includes a flatbed method in which the reading unit 904 scans a document placed on the document placement plate 902 in the sub-scanning direction, and reading that stops the document automatically conveyed by the ADF 908. A document image can be read by a sheet-through method read by the unit 904.

  In the case of the flat bed system, the image of the document placed on the document placement plate 902 is read while moving the reading unit 904 stopped at the standby position where the standby line W is the reading line in the sub-scanning direction. At this time, when the stepping motor 907 is sent in the forward direction by a predetermined number of steps, the reading unit 904 starts reading the image, thereby starting reading the image from the reading start line F where the top side of the document is located. So that it is controlled. The standby position is generally a position where the reading unit 904 is positioned when a line for reading a document by a sheet through method is used as a reading line.

  However, misalignment may occur between the reading start line F and the line on which the top of the document is located due to assembly errors of various components. The standby position is determined by sending the stepping motor 907 a predetermined number of steps from when the reading unit passage detection sensor 909 disposed in the reading table 901 detects passage of the reading unit 904. However, when the detection accuracy of the reading unit passage detection sensor 909 is not good, a position shift occurs in the standby position, and accordingly, a position shift also occurs in the reading start line F. If the reading start line F is misaligned in this way, the leading edge of the document cannot be read and image loss occurs, or an image other than the original is read, and there is an extra margin in the image. There is a problem that occurs.

In order to eliminate such image reading defects, there is a case where a position shift of the reading start line F is detected and corrected using a special chart 910 as shown in FIG. 8A (see, for example, Patent Document 1). .) The special chart 910 has scales in the vertical direction and the horizontal direction. The special chart 910 placed at an accurate position on the document placing plate 902 is read by a sheet through method, and is shown in FIG. As shown, an image is formed on the recording paper 911 based on the read image data, and a reference line 912 is forcibly added to a predetermined position of the recording paper 911 and output. From the recording paper 911 formed in this way, the operator reads and detects the positional deviation of the reference line 912 in the vertical and horizontal directions from the scale, and corrects the positional deviation of the reading start line F.
Japanese Patent Laid-Open No. 4-127658

  However, the correction of the positional deviation using the conventional special chart 910 is performed at the time of shipment of the image reading apparatus 100, and the time-dependent expansion and contraction due to the heat of the belt 906 to which the reading unit 904 is fixed or the image is corrected. When the reading start line F is displaced in the sub-scanning direction after shipment due to impact, vibration, or the like on the reading apparatus 100, there is a problem that an image reading defect occurs. In particular, when a scanned image is transmitted by facsimile, defective image data is transmitted to the transmission destination without the user himself / herself recognizing the occurrence of a defective image reading. Further, even when the user recognizes the occurrence of such an image reading defect, a special chart 910 that is separate from the image reading apparatus 900 is required, and the positional deviation detected using the special chart 910 is used. Since the person himself cannot correct it, there is a problem that it is necessary to call a service person or the like to correct the positional deviation.

  Further, even when the misalignment is corrected using the special chart 910 at the time of shipment of the image reading apparatus 100, the correction is performed based on the misalignment visually detected from the recording paper 911. There was a problem that there was. In addition, since the correction is not automatically performed, there is a problem in that an extra process for correcting the misalignment by the operator occurs and the production cost increases. Further, even when the special chart 910 is placed at a position slightly deviated from an accurate position on the document placing plate 902, there is a problem that the position deviation cannot be detected accurately.

  The present invention has been made to solve such a problem, and can easily detect the presence or absence of a positional deviation of a line for starting reading an image of a document placed on a document placement plate. An object of the present invention is to provide an image reading apparatus capable of automatically correcting the positional deviation.

  In order to achieve the object, the image reading apparatus according to claim 1, wherein the image reading unit that reads an image for each line in the main scanning direction scans the document placed on the document placing plate in the sub-scanning direction. In the image reading apparatus, the image reading unit starts reading an image of a document with a group of line segments in which the number of line segments intersecting with a virtual line in the main scanning direction gradually increases or decreases along the sub-scanning direction. It is characterized in that it is written away from the reading start line in the sub-scanning direction.

  The image reading apparatus according to claim 2 is the image reading apparatus according to claim 1, wherein the line segment group includes a plurality of parallel line segments spaced at equal intervals in the main scanning direction, and the overall outer shape is a right trapezoidal shape. It is characterized by that.

  The image reading device according to claim 3 is the image reading device according to claim 1 or 2, wherein the image reading means reads the image from image data obtained by reading the line segment group for one line in the main scanning direction. It is characterized by comprising a misregistration detecting means for detecting the number of line segments of the line segment group included in the data and detecting the presence / absence of misalignment of the line read by the image reading means based on the detected number of line segments. .

  According to a fourth aspect of the present invention, in the image reading apparatus according to the third aspect, when the positional deviation detecting means detects that there is a positional deviation, the image reading apparatus is based on the number of line segments detected by the positional deviation detecting means. Further, it is characterized in that a misregistration correcting means for correcting the position of the reading start line is provided.

  An image reading apparatus according to a fifth aspect is the image reading apparatus according to any one of the first to fourth aspects, wherein the line segment group is arranged on a shading plate from which the image reading means reads an image as a white reference image. It is characterized by being described.

  An image reading apparatus according to a sixth aspect is the image reading apparatus according to any one of the first to fifth aspects, wherein a plurality of the line segment groups are separated from each other in the main scanning direction. .

  According to the image reading apparatus of the first aspect, the number of line segments in which the line segment group written away from the reading start line in the sub scanning direction intersects with the virtual line in the main scanning direction along the sub scanning direction is the same. Since it consists of line segments that gradually increase or decrease, the reading start line and the sub-scanning direction of the line segment group are uniquely determined from the number of line segments detected from the image data obtained by the image reading unit reading the image of the line segment group with the line in the main scanning direction. It is possible to detect the distance. Accordingly, by causing the image reading unit to read the image of the line segment group, it is possible to easily detect the positional deviation of the reading start line in the sub-scanning direction. Further, since the line segment group is written on the image reading apparatus, a separate member is not required as compared with the case where the position shift of the reading start line is detected using the conventional special chart 910, and at the time of detection. Since it is not necessary to place the special chart 910 at an accurate position on the document placing plate every time, it is possible to accurately and reliably detect the positional deviation of the reading start line.

  According to the image reading apparatus of the second aspect, since the line segment group is composed of a plurality of parallel line segments that are equally spaced in the main scanning direction, the image reading unit displays the image of the line segment group on the line in the main scanning direction. By multiplying the number of line segments detected from the read image data by the interval, it is possible to detect the distance in the sub-scanning direction between the reading start line and the line segment group. Can be detected more easily.

  According to the image reading apparatus of claim 3, even if the reading start line is displaced in the sub-scanning direction due to a change over time, impact, vibration, or the like after shipment, the presence or absence of the displacement is detected. Since the deviation detecting means automatically detects it, it is possible to eliminate problems such as defective image data being transmitted to the transmission destination without the user himself / herself recognizing the occurrence of an image reading defect.

  According to the image reading apparatus of claim 4, when there is a misalignment, the misalignment correction unit automatically corrects the position of the reading start line, and thus when the misalignment occurs and an image reading failure occurs. Even so, it is possible to eliminate defective image reading without calling a service person or the like, so that the work efficiency can be improved. Compared with the case where the operator corrects misalignment using the conventional special chart 910, the misalignment correcting means automatically corrects the misregistration based on the detected number of line segments, so that the misalignment is corrected reliably and accurately. be able to. In addition, since the operator does not need a process of correcting the positional deviation in the sub-scanning direction of the reading start line when the image reading apparatus is shipped, the production cost can be reduced.

  According to the image reading apparatus of the fifth aspect, since the line segment group is written on the shading plate, it is not necessary to provide a separate member on which the line segment group is written, so that the number of members and the assembly process can be reduced. , Increase in production cost can be suppressed. Further, even when there is no space for providing a separate member on which a line segment group is written, the line segment group can be written.

  According to the image reading apparatus of the sixth aspect, since a plurality of line segment groups are described separately in the main scanning direction, a plurality of line segment numbers are detected from image data obtained by reading the plurality of line segment groups. Can do. For this reason, since the positional deviation is detected from a plurality of line segments, the positional deviation can be detected more accurately. Further, even when a part of the line segment group is dirty, it is possible to detect the displacement. Further, by comparing the positional shifts detected from a plurality of line segments, it is possible to detect whether the reading start line is inclined from the main scanning direction.

  An image reading apparatus 100 according to an embodiment of the present invention is a multifunction machine having both a copy function and a facsimile function, and a transparent document placement plate on which a document is placed as shown in FIG. A (platen glass) 10 is provided on the top surface, and a reading unit (image reading means) 11 for reading an image of a document can be moved in the sub-scanning direction (horizontal direction in the figure in the horizontal direction) below the document placing plate 10. An equipped reading table 101 and a document pressing cover 102 for pressing and fixing the document on the document mounting plate 10 are provided. Although not shown, the reading table 101 includes an operation unit (see FIG. 4) for inputting reading start of a document, an image recording unit for recording an image on recording paper, a transmission unit for transmitting an image, And a paper feed cassette for supplying recording paper for recording the read image. Further, an auto document feeder (hereinafter referred to as “ADF”) 1 that automatically feeds and feeds a document is provided in the document pressing cover 102. The image reading apparatus 100 includes a flat bed system in which a reading unit 11 scans an original placed on the original placing plate 10 and reads an image, and a transparent platen placed in parallel on the original placing plate 10 by the ADF 1. The image of the document can be read by a sheet-through method in which the reading unit 11 that stops the document automatically conveyed immediately above the glass 12 reads the image.

  The reading unit 11 is mounted in a substantially rectangular parallelepiped frame 13 that forms the outer shape of the reading table 101, and irradiates light to a reading line in the main scanning direction of the document (a direction perpendicular to the paper surface of FIG. 1). A reduction optical system CCD (Charge Coupled Device) reading unit that converts reflected light from the reading line of the document into an electrical signal and reads an image for each reading line in the main scanning direction. As shown in FIG. 2, a light source 15, a reflection mirror 16, a condenser lens 17, and a CCD line sensor 18 are disposed in a substantially rectangular parallelepiped casing 14. The light source 15 is provided on the upper surface of the housing 14 in the main scanning direction (a direction orthogonal to the paper surface of FIG. 2), and an opening 14 a is formed in the housing 14 along the light source 15. The reflected light of the document enters the housing 14 from 14a. The reflected light R that has entered the housing 14 is sequentially reflected by the appropriately disposed reflecting mirror 16 and guided to the condenser lens 17. Such an arrangement of the reflection mirror 16 is appropriately set according to the optical path length necessary for imaging the reflected light R on the CCD line sensor 18. The reflected light R guided to the condenser lens 17 is imaged on a CCD line sensor 18 in which CCDs are arranged in a line, and the CCD line sensor 18 converts this into an electric signal as image data for one line. Output. Based on this electrical signal, an image of the original is recorded on a recording sheet by the image recording unit, or transmitted by the transmission unit. Since these image recording unit and transmission unit are well-known and arbitrary configurations, detailed description is omitted. To do.

  As shown in FIG. 1, the original platen plate 10, the platen glass 12, and a misregistration detection plate 19 are disposed on the top surface of the reading table 101. As shown in FIG. 3, the document placing plate 10 has an end fixed to the vicinity of a rectangular opening 13 a drilled in the top surface of the frame 13 of the reading placement table 101. The reading unit 11 can read an image of the document placed on the document placement plate 10 from below the plate 10 through the opening 13a. An end of the platen glass 12 is fitted into an opening 13b that is elongated in the main scanning direction and is formed in the top surface of the frame 13 of the reading table 101 so as to be aligned with the opening 13a in the sub-scanning direction. The reading unit 11 can read an image of a document passing directly above the platen glass 12 through the opening 13b from below the platen glass 12.

  The misregistration detection plate 19 has black line segments printed on the surface of a rectangular white sheet made of synthetic resin such as a polyester sheet or synthetic paper, and the top of the frame 13 of the reading table 101. It is fixed to a rectangular recess 13c formed between the openings 13a and 13b on the surface by sticking or the like, so that the reading unit 11 can read the image of the displacement detection plate 19 from below. Yes. The misregistration detection plate 19 is not limited to those made of synthetic resin or synthetic paper. However, if it is made of these, it is excellent in resistance to dirt such as dust and heat, is difficult to peel off, This is preferable because there is an advantage such that there is little expansion / contraction due to the above, and even when it is dirty, it is easy to clean and the line segment group is less likely to be defective. The misregistration detection plate 19 has a black line segment group written on a white plate substrate. If there is a large density difference between the plate substrate and the line segment group, the plate substrate The color of the line segment group is not limited. Further, instead of providing the misregistration detection plate 19 indicating the line segment group, the line segment group may be directly described on the top surface of the frame 13 which is white or milky white or the lower surface of the document placing plate 10.

  The line segment group of the misregistration detection plate 19 includes line segments in which the number of line segments intersecting with the virtual line in the main scanning direction gradually increases or decreases along the sub scanning direction. As shown in FIG. 3, the line segment group in the present embodiment is composed of a plurality of parallel line segments spaced at equal intervals in the main scanning direction, and the entire outer shape is a right trapezoidal shape. More specifically, the line segment group consists of 41 line segments extending straight in the sub-scanning direction with an interval of 0.1 mm in the main scanning direction, and each line segment has the same starting point in the sub-scanning direction. The length becomes longer by a predetermined length sequentially. If the line segment group is composed of line segments that can specify the position of the virtual line in the main scanning direction in the sub-scanning direction from the number of line segments that intersect the virtual line in the main scanning direction along the sub-scanning direction. The line segment group is not limited to the line segment group extending in the direction, and may be a line segment group extending in a direction inclined from the sub-scanning direction, a line segment group extending radially, a line segment group including a curve, or the like.

Then, positional deviation detecting plate 19, the main scanning extending in a direction not actually marked reference line S from the reading start line F in the sub-scanning direction mounting read so as to be positioned apart by a predetermined distance L _SF table 101 It is arranged on the top surface of. The reading start line F is a line where the reading unit 11 starts reading a document by a flat bed method. In the present embodiment, the document is placed on the document placing plate 10 so that the top side comes into contact with the inner wall surface of the opening portion 13a of the frame 13, so that the line on the inner wall surface of the opening portion 13a of the frame 13 is positioned. Is the reading start line F.

Furthermore, a positional deviation detecting plate 19, the reference line S is located apart by a predetermined distance L _WS in the sub-scanning direction from the waiting line W. The standby line W is a line that becomes a reading line of the reading unit 11 when the reading unit 11 is put on standby for the next operation when the original is not read. In this embodiment, a line on which the reading unit 11 reads an original by the sheet-through method is a standby line W. Thereby, when the document reading by the sheet through method is selected, it is not necessary to move the reading unit 11 prior to the start of the reading operation, so that the reading operation can be started quickly. Since this standby line W is a line from which the reading unit 11 reads an image of a document passing directly above the platen glass 12 through the opening 13b from below the platen glass 12, the waiting line W of the platen glass 12 opened at the opening 13b. It is located near the center in the sub-scanning direction.

The frame 13 constituting the top surface of the reading table 101 is formed by integrally molding synthetic resin or the like by molding, and the recess 13c is very accurate and has no variation with respect to the openings 13a and 13b. Can be formed. Accordingly, the positional deviation detection plate 19 is fixed to one inner wall surface of the recess 13c with its end abutting against the reading start line F or the standby line W in the sub-scanning direction by a predetermined distance L _SF. , L _WS can be accurately positioned at a position separated by _WS .

  Further, as shown in FIG. 1, a guide rod 20, a guide rail (not shown), and a belt drive mechanism 21 are disposed on the reading table 101. The guide rod 20 is inserted into a pair of bushes (not shown) provided in the reading unit 11 and is installed in the sub-scanning direction so as to regulate the scanning direction of the reading unit 11. The guide rail is provided in parallel with the guide rod 20 so as to keep the reading unit 11 horizontal by sliding the bottom portion of the reading unit 11 on the upper surface thereof. The belt driving mechanism 21 applies a driving force for moving the reading unit 11, a part of which is a belt 21 a fixed to the reading unit 11, a driving pulley 21 b around which the belt 21 a is wound, and a driven pulley 21 c. And a stepping motor 21d that rotationally drives the drive pulley 21b. By rotating the driving pulley 21b by the driving force of the stepping motor 21d, the belt 21a moves circumferentially, and the reading unit 11 fixed to the belt 21a is guided by the guide rod 20 and the guide rail along with the movement of the belt 21a. To reciprocate in the sub-scanning direction. By controlling the rotation direction and the number of steps of the stepping motor 21d, the moving direction and moving distance of the reading unit 11 can be accurately controlled. The reading unit 11 is composed of one carriage, but may be composed of two carriages, for example, a full rate carriage and a half rate carriage.

  On the other hand, the ADF 1 provided in the document pressing cover 102 sequentially feeds the documents placed on the document tray 2 to the conveyance path 3 and rotates the conveyance roller 5 by the conveyance roller drive motor 4 (see FIG. 4). The document is conveyed and discharged to the discharge tray 6. A document leading edge detection sensor 7 that detects the leading edge of the document being conveyed and outputs a detection signal is disposed in the conveyance path 3.

  FIG. 4 is a block diagram showing an electrical configuration of the image reading apparatus 100 whose upper part is shown in FIG. The image reading apparatus 100 includes the reading unit 11, the stepping motor 21d, the transport roller drive motor 4, the document leading edge detection sensor 7, a control unit (MPU: Microprocessing Unit) 30, an analog / digital converter 31, and an image processing unit. 32, an operation unit 33, a notification unit 34, a ROM (Read Only Memory) 35, and a RAM (Random Access Memory) 36, and each unit constituting the image reading apparatus 100 is communicably connected by a bus 37. ing.

  The control unit 30 is connected to each unit constituting the image reading apparatus 100 via the bus 37, and controls processing operations of these units. The reading unit 11 reads the image data of the document for each main scanning line based on the control signal from the control unit 30 and outputs it as analog image data. Further, the reading unit 11 reads one line of image data of the misregistration detection plate 19 based on a control signal from the control unit 30 and outputs it as analog image data.

  The analog / digital converter 31 performs A / D conversion on the analog image data output from the reading unit 11. The image processing unit 32 performs image processing such as shading correction, shift / line correction, and binarization on the image data A / D converted by the analog / digital converter 31.

  The operation unit 33 includes various operation keys linked to the notification unit 34, such as a start key for instructing the start of reading of a document, a numeric keypad for inputting the number of copies, a cursor key for accepting input of selection of various settings, and the like. It has. The notification unit 34 emits various information such as the operation state and setting state of the image reading apparatus 100, a liquid crystal display panel that displays characters, figures, and the like, an LED lamp that is displayed by turning on or off, a predetermined warning sound, and the like. A speaker for notifying the user is provided.

The ROM 35 is a memory that stores various programs for controlling the processing operations of the respective units constituting the image reading apparatus 100 by the control unit 30. For example, the ROM 35 stores a misregistration detection program 38 and a misregistration correction program 39. Yes. The RAM 36 is a memory that stores various data such as setting information and operation information used for processing operations of the image reading apparatus 100 in a readable and writable state. For example, a reference line segment number N _S , a step number ST _WS , which will be described later, ST _WF and correspondence table T are stored.

  The misregistration detection program 38 stored in the ROM 35 is based on image data obtained by reading the misregistration detection plate 19 by the reading unit 11 located at the misregistration detection position where the detection line D is a reading line. This is a program for the control unit 30 to perform processing for determining whether or not there is a positional deviation with respect to the reference line S. In the present invention, the control unit 30 and the misregistration detection program 38 function as misregistration detection means.

Based on the image data for one line obtained by the reading unit 11 reading the misregistration detection plate 19 with the detection line D, the control unit 30 performs line segments of the line segment group described on the detection line D and the misregistration detection plate 19. detecting a line number N _D which intersect found by comparing the該線fractional N _D to the reference line fractional N _S, determines whether the positional deviation relative to the reference line S of the detection line D. Here, the reference line fractional N _S, the reference line S is the number of line segments intersecting the segment of the line segment group. For example, when the density difference between adjacent pixel data of the image data exceeds a predetermined value, the control unit 30 determines that there is a boundary between the background of the misregistration detection plate 19 and the line segment, and totals the boundaries. based on the number, to detect the number of segments N _D line segments of the detection line D and the line segment groups intersect. When the line number N _D of the detected coincides with the reference line fractional N _S, the position deviation between the detection line D and the reference line S is determined that there is no. On the other hand, if the detected line segment number N _D does not match the reference line segment number N _S , it is determined that there is a displacement between the detection line D and the reference line S.

  The misregistration correction program 39 is a program for the control unit 30 to perform processing for correcting misregistration when the misregistration detection unit determines that there is misregistration. In the present invention, the control unit 30 and the misregistration correction program 39 function as misregistration correction means.

When the control section 30 is position error detection means determines that the positional deviation between the detection line D and the reference line S there, based on the number of line segments N _D where the positional deviation detecting means detects the reading unit 11 The standby position of the reading unit 11 is corrected by correcting the step number ST _WS for sending the stepping motor 21d when moving between the standby position and the position deviation detection position. For example, when the positional deviation detection unit determines that there is a positional deviation between the detection line D and the reference line S, the control unit 30 detects the line segment number N _D and the reference line segment number N _S detected by the positional deviation detection unit. The amount of positional deviation between the detection line D and the reference line S is obtained by multiplying the difference between the two by the interval between line segments. Then, the positional deviation amount, by dividing by the movement distance of the reading unit 11 corresponding to one step of sending a stepping motor 21d, determined number of steps of correction ST _A, the number of steps based on the number of steps of correction ST _A Correct ST _WS . Alternatively, the number of line segments N _D where the positional deviation detecting means detects, by referring to the correspondence table T stored in the RAM 36, and select the number of steps of correction ST _A, may be corrected number of steps ST _WS. Since the moving distance of the reading unit 11 fixed to the belt 21a corresponds to one sending a stepping motor 21d is constant, by correcting the number of steps ST _WS, correcting the positional deviation of the standby position of the reading unit 11 can do.

In the image reading apparatus 100 configured as described above, when reading an image of a document by the flat bed method, the reading unit 11 stopped at the standby position with the standby line W as the reading line is moved in the sub-scanning direction. The image reading is started from the reading start line F. This reading is started when the stepping motor 21d is sent in the forward direction by the predetermined number of steps _STWF , that is, the image is read from the position where the reading unit 11 is separated from the standby position by the distance _LWF (= _LWS + _LSF ) in the sub-scanning direction. The control unit 30 controls the reading unit 11 so as to start reading.

  On the other hand, when reading an image of a document by the sheet-through method, the reading unit 11 stopped at the standby position reads the image of the document that is automatically conveyed by the ADF 1. This reading is performed when the document leading edge detection sensor 7 detects the leading edge of the document and sends a detection signal, and then the document whose reading unit 11 passes the standby line W from when the conveying rotor drive motor 4 is sent a predetermined number of steps. The control unit 30 controls the reading unit 11 so as to start the image reading.

When reading the image on the misregistration detection plate 19, the reading unit 11 stopped at the standby position is moved from the standby position to a misregistration detection position separated in the sub-scanning direction by the distance _LWS. Do. This reading, after sending the stepping motor 21d in the forward direction by a predetermined number of steps ST _WS, the reading unit 11 is performed by controlling the way, the control unit 30 reading unit 11 reads an image only one line .

Hereinafter, the operation control of the image reading apparatus 100 will be described mainly based on the flowchart of FIG.
First, when the image reading apparatus 100 is powered on, the reading unit 11 is stopped at the standby position. The control unit 30 stops the step motor 21d after sending the stepping motor 21d by the number of steps ST _WS, moves the reading unit 11 by a predetermined distance L _WS in the sub-scanning direction, and stops at the position detection position. (S1).

Next, the control unit 30 causes the reading unit 11 to read the image of the misregistration detection plate 19 for one line (S2). Next, based on the line segment number N _D detected from the image data from which the reading unit 11 has read the misregistration detection plate 19, the control unit 30 determines between the detection line D that has read the image data and the reference line S. The presence / absence of a positional deviation is detected (S3).

If the positional deviation is determined that there (S3: Yes), the control unit 30 based on the detected number of line segments _{N D} determined number of steps of correction ST _A (S4), and corrected based on the corrected number of steps ST _A The number of steps ST _WS is stored in the RAM 36 (S5). Note that the notification unit 34 may notify the user that the standby position has been corrected because there is a positional deviation, and may prompt the user to pay attention.

Next, the control unit 30 sends the step number ST _WS after the correction of the stepping motor 21d in the reverse direction, stops the step motor 21d, moves the reading unit 11, and the standby position in which the positional deviation is corrected. (S6), and waits until an image reading start or the like is input from the operation unit 33.

On the other hand, if it is determined that there is no positional deviation (S3: No), the control unit 30, the stepping motor 21d to the step motor 21d is stopped after sending the number of steps _{ST WS} in the opposite direction, moving the reading unit 11 Then, it is stopped at the standby position (S6), and waits until an image reading start or the like is input from the operation unit 33.

  As described above, the position deviation detection plate 19 is provided, and the standby line W is automatically detected by detecting the position deviation between the detection line D and the reference line S obtained by reading the image of the position deviation detection plate 19 by the reading unit 11. The positional deviation of the reading start line F is automatically corrected through the correction of the positional deviation. As a result, when the reading start line F is displaced in the sub-scanning direction after shipment due to temporal expansion / contraction due to heat of the belt 21a to which the reading unit 11 is fixed, impact, vibration, or the like on the image reading apparatus 100. Thus, it is possible to automatically eliminate the image reading defect that occurs in the above. In addition, since the positional deviation of the standby line W, which is a reading line for reading an image by the sheet-through method, is also corrected at the same time, an image reading defect that occurs when the reading line is displaced in the sub-scanning direction is corrected. It can be resolved automatically. Further, when the image reading apparatus 100 is shipped, it is not necessary for the operator to detect and correct the positional deviation in the sub-scanning direction, so that the production cost can be reduced.

Further, since the line segment group of the misregistration detection plate 19 is composed of line segments in which the number of line segments intersecting the virtual line in the main scanning direction along the sub scanning direction gradually increases or decreases, the reading unit 11 detects the detection line. D can be detected uniquely positional deviation amount from the line segment number N _D detected from the read image data, and can be corrected reliably positional deviation. It should be noted that the interval between the line segments constituting the line segment group may be determined by the accuracy of the positional deviation correction. For example, when the allowable accuracy of the reading start line F is 0.2 mm, the interval between the line segments may be set to 0.1 mm or less. The width of the line segment may be at least as long as it exceeds the reading interval of each CCD constituting the CCD line sensor 18.

Further, since the misregistration detection plate 19 is disposed in the recess 13c of the frame 13 in which the opening 13a that defines the position of the reading start line F is formed, a virtual reference line of the misregistration detection plate 19 is provided. S can be positioned at an accurate position away from the reading start line F by a distance L _SF . Thereby, it is possible to always detect the positional deviation accurately.

  Note that the misregistration detection plate 19 may be shared with a shading plate from which the reading unit 11 reads an image as a white reference image. The shading plate is used by the reading unit 11 to read the image and obtain shading correction data. Generally, a white sheet or white tape is used for the openings 13 a and 13 b on the top surface of the frame 13 of the reading table 101. It is fixed and provided between. The image reading position of the reading unit 11 with respect to the shading plate is also determined by the number of steps sent by the stepping motor 21d. According to the present invention, it is possible to correct the displacement of the reading line of the shading plate. As a result, the width of the white portion of the shading plate in the sub-scanning direction can be made narrower than that of the conventional shading plate, and the line segment group of the misregistration detection plate 19 can be described together with the conventional shading plate. For example, as shown in FIG. 6, a white region is provided adjacent to the region where the line group of the displacement detection plate 19 ′ is written in the sub-scanning direction, and the reading unit 11 in which the reading line is positioned on the shading line E is white. The image of the area can be read to obtain shading correction data.

Further, a plurality of line segment groups of the misregistration detection plate 19 may be described separately in the main scanning direction. Thus, it is possible to detect a plurality of line segments number N _D from the image data obtained by reading a plurality of segments groups. Therefore, since detecting the positional deviation of a plurality of line segments number N _D, it is possible to detect the positional deviation more accurately. Further, even when some line segment groups are dirty, the image data obtained by reading the line segment groups is discarded, and the positional deviation is detected from the image data obtained by reading other line segment groups. It becomes possible to detect the positional deviation more reliably. Further, the comparison of the position deviation detected from a plurality of segments number N _D, it is possible to detect whether the read start line F is inclined from the main scanning direction. Then, when it is detected that the reading start line F is inclined from the main scanning direction, the notification unit 34 may notify the user and caution the user.

  The image reading apparatus according to the present invention is not limited to the image reading apparatus 100 shown as the embodiment of the present invention, and it is needless to say that the design can be changed as appropriate without departing from the gist of the present invention. . For example, a single copy machine, a single facsimile machine, or a multifunction machine having a printer function and a scanner function in addition to a copy function and a facsimile function may be used.

  In the image reading apparatus 100, when it is determined that there is a positional deviation between the detection line D and the reference line S, the positional deviation is automatically corrected. However, the present invention is not limited to this. For example, if it is determined that there is a positional shift, this fact and the detected positional shift may be displayed on the liquid crystal display panel or the like of the notification unit 34 and notified by a speaker to alert the user. Further, in the image reading apparatus 100, the presence / absence of a positional deviation between the detection line D and the reference line S is automatically determined, but the present invention is not limited to this. For example, image data obtained by the reading unit 11 reading the misregistration detection plate 19 is formed on a recording sheet by the image recording unit, and an operator counts the number of line segments formed on the recording sheet. The presence or absence of deviation may be determined.

  In the image reading apparatus 100, when the power is turned on, it is determined whether or not there is a positional deviation between the detection line D and the reference line S, but the present invention is not limited to this. For example, every time a predetermined number of documents are read, when a user inputs an instruction to detect misalignment from the operation unit 33 at every predetermined time interval, misalignment or the like is detected when image data read from the manuscript is detected. The presence or absence of may be determined.

In the image reading apparatus 100, the reading unit 11 stands by at a position where the reading line W is read in the sheet-through method, but the present invention is not limited to this. For example, the reading unit 11 may stand by at a position where the reading start line F is read. In this case, when it is determined that there is a positional deviation between the detection line D and the reference line S, the step number ST _SF may be corrected based on the detected line segment number N _D. Furthermore, the image reading apparatus 100 may be a flatbed type dedicated machine not equipped with the ADF 1.

2 is a cross-sectional view showing an internal configuration of an upper part of the image reading apparatus 100 according to the present embodiment. FIG. 3 is a cross-sectional view showing an internal configuration of a reading unit 11. FIG. FIG. 6 is an explanatory diagram showing a misalignment detection plate 19 and the like disposed on the top surface of the reading table 101. 2 is a block diagram showing an electrical configuration of the image reading apparatus 100. FIG. 3 is a flowchart showing a processing operation of the image reading apparatus 100. It is explanatory drawing which shows position shift detection plate 19 'etc. which were arrange | positioned at the top | upper surface of reading mounting base 101'. FIG. 10 is a cross-sectional view showing an internal configuration of an upper part of a conventional image reading apparatus 900. (A) is a plan view showing a conventional special chart 910, and (b) is a plan view showing a recording sheet 911 formed by reading the special chart 910, respectively.

Explanation of symbols

10 Document Placement Plate 11 Reading Unit (Image Reading Unit)
12 Platen glass 19 Misalignment detection plate 19 ′ Misalignment detection plate (shading plate)
30 control unit (position deviation detecting means, position deviation correcting means)
38 Position shift detection program (position shift detection means)
39 Position shift correction program (position shift correction means)
100 Image reader F Reading start line D Detection line S Reference line W Standby line

Claims (6)

In the image reading device, the image reading means for reading an image for each line in the main scanning direction scans and reads the document placed on the document placing plate in the sub-scanning direction.
A line segment group consisting of line segments in which the number of line segments intersecting with virtual lines in the main scanning direction along the sub scanning direction gradually increases or decreases is the sub scanning direction from the reading start line at which the image reading unit starts image reading of the document. An image reading apparatus characterized in that the image reading apparatus is written apart.   2. The image reading apparatus according to claim 1, wherein the line segment group includes a plurality of parallel line segments spaced at equal intervals in the main scanning direction, and the entire outer shape has a right trapezoidal shape.   The image reading unit detects the number of line segments of the line group included in the image data from image data obtained by reading the line group for one line in the main scanning direction, and based on the detected number of line segments, The image reading apparatus according to claim 1, further comprising a position deviation detection unit that detects the presence or absence of a position deviation of the line read by the image reading unit.   When the positional deviation detecting unit detects that there is a positional deviation, the positional deviation detecting unit includes a positional deviation correcting unit that corrects the position of the reading start line based on the number of line segments detected by the positional deviation detecting unit. Item 4. The image reading apparatus according to Item 3.   5. The image reading apparatus according to claim 1, wherein the line segment group is written on a shading plate that reads an image as a white reference image by the image reading unit.   6. The image reading apparatus according to claim 1, wherein a plurality of the line segment groups are written apart from each other in the main scanning direction.

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