JP5145181B2 - Image reading apparatus and image forming apparatus having the same - Google Patents

Description

  The present invention relates to an image reading apparatus used for a digital copying machine, an image scanner, and the like to scan and read a document and an image forming apparatus including the image reading apparatus, and more particularly to creation of white reference data.

  2. Description of the Related Art Conventionally, in an image reading apparatus mounted on a copying machine using an electrophotographic process, a document is conveyed so that a sheet-like document is sequentially sent to a document placing table and discharged from the document placing table after reading. Some are equipped with devices. In such an image reading apparatus, a sheet-through method in which a document is automatically conveyed and read by a document conveying device while the document press is closed, and the document press is opened and closed each time reading is performed on a document placement table (contact glass). Two types of reading methods are possible: a document fixing method in which one document is replaced one by one.

  In the former sheet-through method, the optical system in the image reading apparatus is scanned and moved while the document is held at a predetermined image reading position. On the other hand, in the latter document fixing method, the optical system is used. The scanning operation is performed while scanning.

  In such an image reading apparatus, an image is read using a CCD sensor having four color sensors, a color sensor corresponding to red (R), green (G), and blue (B), and a monochrome sensor. There is a case. In order to read an appropriate image with each sensor, white reference data is created using a white reference plate and shading correction is performed. However, if the creation of white reference data is insufficient, it is difficult to ensure sufficient image quality.

Therefore, a method for appropriately performing shading correction has been proposed. For example, Patent Document 1 discloses a method for performing shading correction in an optimum region of a white reference plate by providing four black marks on the white reference plate. Is disclosed.
JP 2004-120599 A

  However, in the method of Patent Document 1, there is a risk of increasing the cost due to marking. Further, the position detection may be affected by the marking density, and the marking density management may be required to detect the optimum region. On the other hand, in recent years, the number of CCD sensors in which the R, G, B, and monochrome sensors are separated from each other is increasing, and the area necessary for reading the four-color CCD sensor on the white reference plate is increased in the sub-scanning direction. .

  In addition, the number of parts related to the optical positional relationship between the CCD sensor and the white reference plate is increasing. For this reason, the CCD sensor cannot read the reflected light at the reading position set in advance on the white reference member due to factors such as component tolerance, assembly variation, and adjustment of the imaging position of the CCD sensor. There is a possibility that the reading position of the sensor greatly varies. Therefore, in order to create an appropriate white reference, it is necessary to consider such variation in reading position.

  In view of the above problems, the present invention provides an image reading apparatus and an image forming apparatus that can appropriately detect the reading position of the photoelectric conversion member in the white reference member, create appropriate white reference data, and sufficiently ensure image quality. The purpose is to provide.

  To achieve the above object, the present invention has a light source that illuminates a document in the scanning direction and a mirror that guides reflected light from the document as image light, and can be moved in the sub-scanning direction, and the scanning unit A photoelectric conversion member that converts the image light guided by the light into an electrical signal, and a white reference member. The white reference member is irradiated with the light source, and reflected light from the white reference member is reflected by the photoelectric conversion member. In the image reading apparatus for creating reading white reference data, the white reference member has a substantially rectangular reflecting surface arranged along the scanning direction, and at least one end of the reflecting surface in the scanning direction. Is characterized in that an inclined portion having a shape in which at least one end portion in the sub-scanning direction is cut out obliquely is formed.

  In the invention, it is preferable that an inclination angle of the inclined portion with respect to the sub-scanning direction is approximately 45 °.

  In the present invention, the white reference member is fitted and held, and a holding member having an opening end disposed along the outer periphery of the reflecting surface is provided, and the whiteness of the holding member is a predetermined threshold value. It is characterized by being smaller than.

  Further, the present invention is characterized in that the reflected light from the white reference member is read by the photoelectric conversion member, and the reading position of the photoelectric conversion member in the white reference member is detected based on the detection value of the photoelectric conversion member. .

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

  According to the first configuration of the present invention, the white reference member has a substantially rectangular reflecting surface arranged along the scanning direction, and at least one end of the reflecting surface in the scanning direction is at least one end in the sub-scanning direction. By forming an inclined portion having a shape in which the portion is cut out obliquely, the reflected light from the white reference member is regularly arranged in the scanning direction according to the reading position in the sub-scanning direction by the photoelectric conversion member in the white reference member. Can be different.

  Thereby, the difference in the scanning direction of the reflected light can be detected by the photoelectric conversion member, and the reading position of the photoelectric conversion member in the sub-scanning direction on the white reference member can be detected based on the detected value. . Therefore, it is possible to appropriately detect the reading position of the white reference member by the photoelectric conversion member, and to create white reference data at the appropriate reading position, thereby ensuring sufficient image quality.

  Further, according to the second configuration of the present invention, in the image reading apparatus of the first configuration, the reflected light from the white reference member is obtained by setting the tilt angle of the tilt portion to the sub-scanning direction to be approximately 45 °. The difference in the scanning direction can be made substantially equal to the difference in the sub-scanning direction of the reading position by the photoelectric conversion member in the white reference member. Thereby, the reading position by the said photoelectric conversion member can be detected more efficiently.

  Further, according to the third configuration of the present invention, in the image reading apparatus having the first or second configuration, the white reference member is fitted and held, and the opening end extends along the outer periphery of the reflection surface. By providing a holding member to be arranged and making the whiteness of the holding member smaller than a predetermined threshold value, the boundary between the reflecting surface of the white reference member and the other part becomes clearer, and the reflection from the white reference member The difference in the scanning direction of light can be made clearer. Thereby, the detection accuracy of the difference by the photoelectric conversion member can be increased, and the reading position by the photoelectric conversion member can be detected with higher accuracy.

  According to the fourth configuration of the present invention, in the image reading apparatus having any one of the first to third configurations, the reflected light from the white reference member is read by the photoelectric conversion member, and the photoelectric conversion member is detected. By detecting the reading position of the photoelectric conversion member in the white reference member based on the value, the difference in the scanning direction of the reflected light from the photoelectric conversion member can be expressed as the difference in the detection value of the photoelectric conversion member. Based on the difference, the reading position by the photoelectric conversion member can be detected. As a result, the reading position can be appropriately detected and appropriate white reference data can be created, and image quality can be sufficiently ensured.

  In addition, according to the fifth configuration of the present invention, it is possible to create appropriate white reference data and ensure sufficient image quality by mounting the image reading device having any one of the first to fourth configurations. Image forming apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a front sectional view showing an internal configuration of an image forming apparatus equipped with an image reading apparatus according to an embodiment of the present invention, and FIG. 2 is a front view showing the internal configuration of the image reading apparatus of the present embodiment. It is sectional drawing.

  As shown in FIG. 1, the image forming apparatus 100 is a so-called in-cylinder discharge type digital copying machine, and roughly includes a main body housing 20 and an image reading device 21 disposed on the main body housing 20. ing. Various mechanisms, which will be described later, are provided in the image reading device 21 for reading an image of a document as an electrical signal. On the other hand, the main body housing 20 is based on an electrical signal of a document image read by the image reading device 21. Various mechanisms to be described later are provided for transferring the image onto the paper.

  The main body housing 20 includes a lower housing 20a and a connection housing 20b that is positioned along the left side and is connected to the image reading device 21. The lower housing 20a accommodates and feeds paper. A paper feeding unit for forming a toner image on the paper, a fixing unit for fixing the toner image on the paper, and the like. A paper discharge unit for conveying and discharging is provided.

  Further, an in-cylinder discharge space 22 is formed on the right side of the connecting housing 20b immediately below the image reading device 21 so as to be largely open toward the right side and the front surface. A paper discharge tray 23 for receiving and stacking paper discharged horizontally from the right side surface of the connecting housing 20b is provided.

  On the upper surface of the image reading device 21, a contact glass 25 and an operation panel (not shown) exposed on the front side are disposed. Further, above the image reading device 21, a document pressing unit 28 equipped with a document conveying device 27 that conveys a sheet-like document to the first image reading unit R <b> 1 in the contact glass 25 is a hinge unit on the back of the image reading device 21. It is supported so that it can be opened and closed freely.

The document presser 28 can take a closed state in which the document reading operation is performed by closing the contact glass 25 and an open state in which the document presser 28 is opened. In the document fixing method that does not use the document conveying device 27, each time the document is read, the document pressing 28 is opened and closed, and the document is replaced one by one in the second image reading unit R2 of the contact glass 25 to perform reading.

  The document transport device 27 includes a document feed tray 29 having a document guide 29a for aligning and stacking a plurality of documents, and a document feed tray 29 positioned above the first image reading unit R1 in the contact glass 25. A document cover 30 that protrudes, and a document discharge tray 31 that is formed directly on a part of the upper surface of the document presser 28 at the side of the document cover 30. A document transport path d that reaches the document discharge tray 31 is formed.

  In the document cover 30, document conveyance means including a pickup roller 32, a conveyance roller pair 33, a registration roller pair 34, and a discharge roller pair 35 is provided in order from the upstream side along the document conveyance path d. Among these, the conveyance roller pair 33 is composed of a drive roller 33a and a separation roller 33b. The separation roller 33b rotates in the opposite direction to the drive roller 33a only when the rotational load is lower than a predetermined torque, and the rotational load is reduced. When the torque exceeds a predetermined torque, the drive roller 33a is driven to rotate.

  A document pressing unit 36 is disposed between the registration roller pair 34 and the discharge roller pair 35 so as to face the first image reading unit R1 in the contact glass 25 and presses the document toward the first image reading unit R1. Is provided. Further, a white reference plate (white reference member) 55 is embedded between the first and second image reading units R1 and R2 of the contact glass 25. The document conveyance path d is curved so as to be reversed between the conveyance roller pair 33 and the first image reading unit R1. Details of the white reference plate 55 will be described later.

  The document transport path d is provided with a plurality of sensors for detecting whether or not a document exists. For example, a document detection sensor S 1 is provided at the center of the document feed tray 29, a paper feed sensor S 2 is provided downstream of the transport roller pair 33, and a discharge sensor S 3 is provided downstream of the discharge roller pair 35. ing. Documents set on the document feed tray 29 are sequentially conveyed one by one by the document conveying means through the document conveyance path d, and sequentially discharged onto the document discharge tray 31 after passing through the first image reading unit R1. . The document discharged on the document discharge tray 31 is taken out by the user's hand.

  Next, a sheet-through type document conveyance operation using the document conveyance unit 27 will be described. In the sheet-through type document conveying operation, first, a plurality of documents set with the image surface facing upward on the document feeding tray 29 is subjected to a predetermined pressure by a lifting plate 37 biased upward by a spring member 37a. Is pressed against the pickup roller 32. Here, when the copy start button on the operation panel is turned on, the pickup roller 32 and the conveyance roller pair 33 are rotationally driven by a primary paper feed driving means (not shown).

  The document set on the document feed tray 29 is normally fed by the pickup roller 32 to the upper pair of transport rollers 33. The plurality of originals sent to the conveyance roller pair 33 are separated by the separation roller 33b and are conveyed toward the registration roller pair 34 after being separated by the separation roller 33b.

  At that time, after the leading edge of the document is detected by the sheet feeding sensor S2, the document is conveyed by a predetermined distance, and then the driving roller 33a and the pickup roller 32 of the conveying roller pair 33 are stopped by the operation of the primary sheet feeding driving means. Is stopped and the primary paper feeding is completed. The document that has been primarily fed is stopped with its leading end pressed against the nip portion of the registration roller pair 34 and with its leading end being bent.

  Secondary feeding is started after a predetermined time has elapsed since the completion of primary feeding. That is, the registration roller pair 34 is rotationally driven by the operation of the secondary paper feed driving means (not shown). The original is conveyed by the registration roller pair 34 to the discharge roller pair 35 via the first image reading unit R1, and is finally discharged onto the original discharge tray 31 by the discharge roller pair 35. At this time, the completion of image reading of one original is detected by detecting the passage of the rear end of the original by the discharge sensor S3.

  Here, the discharge sensor S3 has a counting function that counts the number of documents every time the document feed and conveyance is completed. If the document detection sensor S1 detects a subsequent document, the second and subsequent document conveyance is performed. Will continue as above. When the document passes through the first image reading unit R1, it is conveyed while being lightly pressed against the contact glass 25 by the document pressing unit 36, and the image of the document is read through the first image reading unit R1. It has become.

  Next, the configuration of the image reading device 21 for reading an image of a document as an electrical signal will be described with reference to FIGS. In the frame 21a of the image reading device 21, a lamp (light source) 1 for irradiating light toward the image surface of the document, and a reflecting plate 2 for efficiently applying the light from the lamp 1 to the image surface of the document. The first mirror 3 that directly receives and reflects the reflected light of the original, the second mirror 4 that receives and reflects the reflected light from the first mirror 3, and receives and reflects the reflected light from the second mirror 4. A third mirror 5 is disposed.

  A lens barrel 6 holding a lens group (not shown) that collects the reflected light from the third mirror 5 and collects the original reflected light collected by the lens group of the lens barrel 6. A line-type CCD sensor (photoelectric conversion member) 7 including a photoelectric conversion element that converts an electric signal is disposed on the base plate 10. The optical path of the original reflected light is indicated by a one-dot chain line.

  Here, the lamp 1, the reflecting plate 2, and the first mirror 3 are integrally fixed on the first carriage (first scanning means) 8, and the second mirror 4 and the third mirror 5 are fixed to the second carriage (first carriage). The first and second carriages (scanning means) 8 and 9 are independent of each other, but are capable of reciprocating in cooperation with each other.

  That is, when the original image reading operation is performed by the above-described sheet through method, the first carriage 8 is moved and held immediately below the first image reading unit R1, and the second carriage 9 is held at a predetermined position. On the other hand, in the original fixing method, the first carriage 8 and the second carriage 9 reciprocate (scan) the second image reading unit R2 while maintaining the optical path length of the original reflected light constant. Further, the first carriage 8 and the second carriage 9 are driven by a carriage drive motor 53 (see FIG. 7) not shown here.

  Under such a configuration, the document reflected light irradiated from the lamp 1 and reflected by the image surface of the document is reflected by the first mirror 3 to the third mirror 5 and introduced into the lens group in the lens barrel 6. The light is condensed by the lens group and formed on the CCD sensor 7. The CCD sensor 7 performs photoelectric conversion processing, and the original image is read as an electric signal. Details of the CCD sensor 7 will be described later.

  Next, the configuration of various mechanisms provided in the main body housing 20 for transferring the image to the sheet based on the electric signal of the read document image will be described below with reference to FIG. First, the sheet feeding unit will be described. A sheet feeding cassette 40 that stores sheets of various sizes (mainly sheets) and can be taken in and out from the front is disposed at the lower portion of the lower housing 20a.

  The sheets P stored in the paper feed cassette 40 are sent out one by one by the feeding roller 40a. Further, an openable and closable manual feed tray 41 that is pulled down as necessary is provided on the left side surface of the lower portion of the lower housing 20a, and a sheet (paper or OHP sheet) P ′ set on the manual feed tray 41 is provided. Are fed one by one by the feeding roller 41a.

  Next, an image forming unit for forming a toner image on a sheet and a fixing unit for fixing the toner image on the sheet will be described. Above the paper feed cassette 40 in the lower housing 20a, a photosensitive drum 42 constituting a main image forming unit, a charging device 43, a laser exposure unit 44, a developing device 45, A transfer roller 46 and a cleaning device 47 are provided. A fixing device 48 is disposed in the lower housing 20a above the transfer roller 46 and directly below the connecting housing 20b.

  The photosensitive drum 42 is made of positively chargeable amorphous silicon, and rotates clockwise in FIG. 1 at a predetermined peripheral speed when driven. The surface of the photosensitive drum 42 is uniformly charged by corona discharge generated from the charging device 43 to which a high voltage is applied, and then the beam from the laser exposure unit 44 based on the electrical signal of the original image from the CCD sensor 7. By the light irradiation, an electrostatic latent image composed of a predetermined light potential and dark potential portion is formed.

  Further, the electrostatic latent image rotates to the developing position by the rotation of the photosensitive drum 42. The developing roller 45a, which is a constituent element of the developing device 45, is made of stainless steel and has a fixed magnet inside. The developing roller 45a is rotatably supported with a predetermined gap from the photosensitive drum 42, and in the same direction as the photosensitive drum 42 when driven. At a predetermined peripheral speed.

  The developing device 45 is filled with, for example, a positively charged magnetic toner having a volume average particle diameter of 9 μm (median diameter measured by a Coulter counter), and a toner thin film is formed on the surface of the developing roller 45a by a magnetic blade (not shown). A layer is formed. A predetermined developing bias voltage is applied to the developing roller 45a. The toner that has reached the developing region flies from the surface of the developing roller 45a by the developing bias voltage, and is attracted to the electrostatic latent image on the surface of the photosensitive drum 42, whereby a toner image is formed (developed).

  Here, the sheet P (or P ′) that is fed one by one from the paper feed cassette 40 (or the manual feed tray 41) and reaches the registration roller pair 49 has a toner image on the photosensitive drum 42 approaching the transfer roller 46. In synchronization with this, the registration roller pair 49 feeds the sheet upward while adjusting the conveyance timing, and is conveyed between the photosensitive drum 42 and the transfer roller 46 through the conveyance path T1. Then, most of the toner in the toner image is transferred onto the sheet P when the leading edge of the sheet P and the leading edge of the toner image pass through the transfer roller 46.

  The toner remaining on the surface of the photosensitive drum 42 without being transferred onto the sheet P is removed from the photosensitive drum 42 by the cleaning device 47. On the other hand, the sheet P on which the toner image is transferred is sent to the fixing device 48. The fixing device 48 has a pair of fixing rollers including a heating roller 48a and a pressure roller 48b, and the toner image on the sheet P passing through the nip is heated and pressed by the pair of fixing rollers to be fixed. As a result, a fixed transfer image is formed on the sheet P.

  The sheet P that has passed through the fixing device 48 is conveyed into the connecting housing 20b along the vertical conveyance path T2 that is directed vertically upward. In the connection housing 20b, a conveyance roller pair 50 connected to the vertical conveyance path T2 and a discharge roller pair 51 for discharging the sheet P to the paper discharge tray 23 are disposed. The sheet P sent out from the conveyance roller pair 50 reaches the discharge roller pair 51 through the conveyance path T3 and is discharged from the discharge roller pair 51 to the paper discharge tray 23.

  Next, the white reference data creation operation of the image reading device 21 and the details of the white reference plate 55 will be described. 3 is a top view showing the internal configuration of the image reading apparatus of the present embodiment, FIG. 4 is a top view showing the white reference plate and the holding member of FIG. 3, and FIG. 5 is a region S of FIG. It is an enlarged view showing the periphery of (dot-dash line). In FIG. 3, for convenience, the reflecting plate 2 and the base plate 10 are omitted. Moreover, the same code | symbol is attached | subjected to the part which is common in FIG.1 and FIG.2, and description is abbreviate | omitted.

  The CCD sensor 7 is provided with four line sensors (not shown) of R, G, and B color sensors and a monochrome sensor. Each sensor is not shown in the figure, but is R from above to below at a predetermined interval. , G, B, monochrome line sensors are arranged in this order. The CCD sensor 7 is configured to perform shading correction using a white reference plate 55 before reading a document image.

  As shown in FIGS. 2 and 3, the first carriage 8 is disposed at the home position when the apparatus is stopped. From this state, when the first carriage 8 moves leftward in the left-right direction (sub-scanning direction, Y direction) and the lamp 1 irradiates a predetermined area (reference reading position) of the white reference plate 55, the reflected light reflected at the reference reading position. The light is reflected by the first mirror 3 to the third mirror 5 and introduced into the lens group in the lens barrel 6, condensed by the lens group and imaged on the CCD sensor 7. As described above, the second carriage 9 also moves in cooperation with the first carriage 8 so that the optical path length of the reflected light is kept constant.

  The reference reading position on the white reference plate 55 is set in advance, and is formed from an area having a predetermined width in the sub-scanning direction on the white reference plate 55. The control unit 60 generates white reference data by transmitting an electrical signal (data) read and converted by the CCD sensor 7 to the control unit 60 described later.

  For this reason, in order to create appropriate white reference data and sufficiently ensure image quality, it is necessary to appropriately read the reference reading position on the white reference plate 55 by the CCD sensor 7. However, the reading position of the white reference plate 55 in the sub-scanning direction by the CCD sensor 7 may vary.

  There are various causes of such variations depending on the device configuration and the like. Mainly, (1) variation in mounting of the CCD sensor 7, (2) first to third mirrors 3, 4, 5, lens barrel 6, etc. Examples include variations in reflection and image formation due to misalignment of members disposed between the white reference plate 55 and the CCD sensor 7, and (3) variations in assembly of the frame 21a, the holding member 57, the contact glass 25, and the like.

  (4) When the R, G, B, and monochrome sensors are spaced apart from each other, the sub-scans occupied by the reference reading positions are necessary for all the color sensors to read the reference reading positions of the white reference plate 55. It is necessary to increase the width in the direction, and the variation in (1) to (3) can easily affect the reading position of each color sensor.

  If the reading position of the white reference plate 55 by the CCD sensor 7 varies due to the factors exemplified in the above (1) to (4), it is difficult to appropriately read the reference reading position by the CCD sensor 7. In such a case, it is difficult to create appropriate white reference data, and there is a risk that sufficient image quality cannot be ensured.

  At this time, if the reading position in the sub-scanning direction of the CCD sensor 7 on the white reference plate 55 can be detected, the reflected light at the reference reading position can be appropriately read by the CCD sensor 7 even if the above-described variation occurs. Become. Therefore, in the present embodiment, the substantially rectangular reflection surface 55a of the white reference plate 55 is at least one end (here, both ends) in the scanning direction of the reflection surface 55a and at least one end (here, the CCD) in the sub-scanning direction. The inclined portion 55e having a shape obtained by obliquely cutting out the end portion opposite to the sensor 7 is formed.

  As shown in FIGS. 3 and 4, the white reference plate 55 is formed by cutting out the upper left and lower left corners obliquely in a rectangular plate-like member that is elongated in the vertical direction (scanning direction, X direction). ing. That is, as shown in FIG. 4, the white reference plate 55 is formed in a shape in which the left and right end portions 55c are cut out in the left and right direction (sub-scanning direction, Y direction) at the upper and lower end portions 55b. Since the white reference plate 55 is cut out, the reflection surface 55a (see FIG. 2) is also formed in the same shape.

  Accordingly, the white reference plate 55 (that is, the reflection surface 55a) includes an upper and lower end portion 55b that are substantially parallel to each other, and a left end portion 55c that is substantially perpendicular to the upper and lower end portions 55b and substantially parallel to each other. And a right end portion 55d, an inclined portion 55e disposed between the upper end portion 55b and the left end portion 55c, and an inclined portion 55e disposed between the lower end portion 55b and the left end portion 55c. being surrounded.

  The length in the left-right direction of the white reference plate 55 is set to W. The vertical length of the left side edge of the left side edge 55c is set larger than the reading width of the document. As shown in FIG. 5, the inclination angle θ of the inclined portion 55e with respect to the sub-scanning direction is set to about 45 °, and the vertical and horizontal lengths of the inclined portion 55e are both set to L. Yes.

  The white reference plate 55 is fitted in a black holding member 57 having a rectangular box shape so that the side surface and the upper surface are covered (see FIG. 2). The inner surface of the holding member 57 is formed so as to contact all the side surfaces of the white reference plate 55. Further, the opening end of the holding member 57 is formed so as to be substantially flush with the reflection surface 55 a that is the lower surface of the white reference plate 55. That is, the opening end of the holding member 57 is disposed along the outer periphery of the reflection surface 55e. The holding member 57 can be made of resin, for example.

  Next, the detection operation of the reading position on the white reference plate 55 by the CCD sensor 7 will be described. The configuration of the two inclined portions 55e formed on the white reference plate 55 is exactly the same, so the periphery of the upper end portion 55b shown in the region S of FIG. 4 will be described with reference to FIGS.

  FIG. 6 is a diagram showing the relationship between the reading position of the CCD sensor in the sub-scanning direction on the white reference plate and the detection value of the CCD sensor. Here, the scanning line including the apex (the upper right apex in FIGS. 5 and 6) formed by the right end 55d and the upper end 55c of the white reference plate 55 is A1, the upper end 55b and the inclined portion 55e. A2 is included in the scanning line including the apex formed in step (center upper apex in FIGS. 5 and 6), and the apex formed in the inclined portion 55e and the left end 55c (lower left apex in FIGS. 5 and 6) is included. Let the scanning line be A3.

When the generation of the white reference data is started, the first carriage 8 moves toward the white reference plate 55 from the home position (position shown in FIG. 2) to the left. When the first carriage 8 reaches the white reference plate 55, it moves further to the left, irradiates the white reference plate 55 with the lamp 1 from the scanning lines A 1 to A 3 in FIG. 5, and reads the reflected light by the CCD sensor 7. .

  The detection value of the CCD sensor 7 is transmitted to the control unit 60 (see FIG. 7). In the pixel region where the detection value of the CCD sensor 7 is equal to or greater than a predetermined threshold I, it is “white”. Is transmitted to the control unit 60. On the other hand, in the pixel region where the detection value of the CCD sensor 7 is less than the threshold value I, a black signal indicating “not white” is transmitted to the control unit 60. Here, a case where “signal 255” is detected as a white signal from the white reference plate 55 and “signal 0” is detected as a black signal from the holding member 57 will be described.

When the first carriage 8 moves to the left (downstream in the Y ′ direction) and the CCD sensor 7 reads the scanning line A1, the reflected light from the black holding member 57 is acquired in the scanning direction (vertical direction, X direction). A signal 0 is detected in the pixel area, and a signal 255 is detected in the pixel area where the reflected light from the white reference plate 55 is acquired. Thereby, in the scanning line A1, the upper end 55b of the white reference plate 55 is detected, and waveform data as shown by the CCD detection value 1 in FIG. 6 is obtained. Further, since the vertical length of the white reference plate 55 is substantially equal between the scanning lines A1 and A2, the CCD detection value 1 is obtained as described above.

When the first carriage 8 is further moved to the left side, the CCD sensor 7 detects the inclined portion 55e between the scanning lines A2 and A3, and the white reference is advanced from A2 to A3 due to the presence of the inclined portion 55e. The vertical length of the plate 55 is shortened inward (the lower side in the figure). Therefore, as the scanning line advances from A2 to A3, the region where the signal 225 is obtained shifts inward, and the rising edge of the waveform of the signal 255 also shifts inward.

  For example, in a predetermined scanning line As between A2 and A3, the holding member 57 extends inward by a length a from the A2 in the scanning direction, and the white reference plate 55 is retracted inward by the length a. . Thereby, waveform data as shown by the CCD detection value 2 in FIG. 6 is obtained in the scanning line As. In the CCD detection value 2, the rise of the waveform indicated by the signal 255 is shifted inward in the scanning direction by the number of pixels dD corresponding to the length a from the CCD detection value 1, and the region of the signal 255 is narrowed inward by that amount. Yes.

  Based on the CCD detection value 1 and the CCD detection value 2, the pixel number difference dD at the rising position of the waveform indicating the signal 255 can be calculated. Further, based on the pixel number difference dD, the control unit 60 can calculate the vertical distance dX (here, a) of the white reference plate 55 between the scanning lines A2 and As.

Here, the inclination angle θ of the inclined portion 55e is set to approximately 45 °, and the vertical distance dX between the scanning lines A2 and As and the horizontal distance dY are substantially equal. The distance dY can be easily calculated (here, dY is a). However, the distance dY can also be calculated from the distance dX and the inclination angle θ by dY = dX / tan θ. The distance from the right end 55d of the scanning lines As the W-L + dY distance from, and the left end portion 55 c (W-L + a in this case) becomes L-dY (here L-a).

  In this way, the CCD detection value 1 is detected between the scanning lines A1 and A2 by the CCD sensor 7 and the CCD detection value 2 is detected between the scanning lines A2 and A3. Based on the pixel number difference dD with respect to the detection value 2, the vertical distance dX from the upper end 55b of the inclined portion 55e of the white reference plate 55 can be calculated. Then, the distance dY in the left-right direction from the scanning line A2 can be calculated from the distance dX and the inclination angle θ, and the reading position of the CCD sensor 7 in the sub-scanning direction can be detected.

  FIG. 7 is a block diagram illustrating an example of a control path of the image reading apparatus. It should be noted that since various controls of each part of the image forming apparatus 100 are performed when using the image reading apparatus 21, the entire control path becomes complicated. Therefore, here, only a portion of the control path that is necessary for implementing the present invention will be described.

  The control unit 60 is, for example, a CPU (Central Processing Unit), and controls the driving of the first carriage 8 and the second carriage 9 by transmitting a control signal to the carriage drive motor 53 in accordance with a set program. At the same time, the light emission timing of the lamp 1 in the first carriage 8 is controlled. Further, the electrical signal transmitted from the CCD sensor 7 is subjected to resolution processing, scaling processing or gradation processing as necessary to create image data. Further, white reference data is created based on an electrical signal transmitted from the CCD sensor 7 by reading at the reference reading position.

  The storage unit 61 includes an image memory 70, a ROM (Read Only Memory) 71, and a RAM (Random Access Memory) 72. The image memory 70 converts the image data created in the control unit 60 into a digital signal and stores it. To do. The ROM 71 and RAM 72 store basic programs and processing contents used in the control unit 60.

  In addition, the ROM 71 and the RAM 72 also detect the scanning direction position in which the threshold I, the reference reading position, the number of pixels in the scanning direction in the detection value of the CCD sensor 7 and the distance dX in the vertical direction on the white reference plate 55 are related. A parameter, a sub-scanning direction position detection parameter that associates the distance dX, the inclination angle θ, and the distance dY in the left-right direction are stored.

  Here, it is assumed that the reference reading position is set in advance on the scanning line As. When the white reference data creation mode is set, the first carriage 8 moves to the left from the home position (see FIG. 2), and the reflecting surface 55a of the white reference plate 55 is moved from the scanning line A1 to the scanning line A3. Scan and read by the CCD sensor 7.

  At this time, the control unit 60 reads the scanning direction position detection parameter and the sub-scanning direction position detection parameter from the ROM 72. When the CCD detection value 1 between the scanning lines A1 and A2 is transmitted from the CCD sensor 7 to the control unit 60 and then the CCD detection value 2 between the scanning lines A2 and A3 is transmitted as needed, the control unit 60 The pixel number difference dD and the distance dX are calculated, and the distance dY is calculated.

When the reading position of the CCD sensor 7 reaches the position where the distance dY is a, that is, the scanning line As, the control unit 60 converts the white reference data based on the detection value (CCD detection value 2) on the scanning line As. create. In addition, for example, after scanning the scanning lines A1 to A3 by pre-scanning or the like, the scanning line As where the distance dY is a (dY = a) is calculated, and then the first carriage 8 is moved again to scan the scanning line. White reference data can also be created by reading As.

  Thus, by providing the inclined portion 55e on the white reference plate 55 and detecting the distance dY in the sub-scanning direction, the CCD sensor on the white reference plate 55 can be used even if there are variations (1) to (4). 7 can be properly grasped, and reading by the CCD sensor 7 at the reference reading position becomes possible. As a result, appropriate white reference data can be created regardless of the above-described variations and the like, and the image quality can be improved. As described above, the upper inclined portion 55e has been described here, but the same applies to the lower inclined portion 55e.

  In the present embodiment, the vertical angle dX from the scanning line A2 at the inclined portion 55e (between the scanning lines A2 and A3) is set by setting the inclination angle θ to about 45 ° with respect to the sub-scanning direction. And the distance dY in the left-right direction can be made substantially equal. Thereby, the reading position in the sub-scanning direction on the white reference plate 55 can be easily calculated. Therefore, the reading position of the CCD sensor 7 can be detected efficiently. However, the inclination angle θ is not particularly limited to this.

  If the inclination angle θ is reduced, the difference dD in the number of pixels between the CCD detection value 1 and the CCD detection value 2 by the CCD sensor 7 at the inclination portion 55e becomes small, and the detection accuracy of the reading position may be lowered. On the other hand, if the inclination angle θ is increased, the length L in the left-right direction of the inclined portion 55e is reduced, the acquisition area of the CCD detection value 2 is reduced, and there is a possibility that a detection value sufficient for detecting the reading position cannot be obtained. is there. Therefore, the inclination angle θ can be appropriately set in consideration of such a viewpoint, for example.

  Further, when the length L in the left-right direction of the inclined portion 55e is increased, the area between the scanning lines A1 and A2 is shortened, and the acquisition area of the CCD detection value 1 serving as one reference for detecting the reading position is narrowed. The reading position detection accuracy may be reduced. On the other hand, if the length L in the left-right direction of the inclined portion 55e is reduced, the area between the scanning lines A2 and A3 is shortened, and the acquisition area of the CCD detection value 2 serving as the other reference for detecting the reading position is narrowed. The reading position detection accuracy may be reduced.

  Further, if the vertical length L of the inclined portion 55e is increased, the reading area of the document may be affected, or the white reference plate 55 may be increased in size and the apparatus main body may be increased in size. On the other hand, if the vertical length L of the inclined portion 55e is reduced, the pixel number difference dD between the CCD detection value 1 and the CCD detection value 2 is reduced, and the detection accuracy of the reading position may be reduced. . Therefore, for example, considering these, the vertical length L and the horizontal length L of the inclined portion 55e can be set as appropriate. Further, the width W of the white reference plate 55 in the sub-scanning direction can be appropriately set depending on the size of the inclined portion 55e, the device configuration, and the like.

  Here, the inclined portion 55e is formed between the upper and lower end portions 55b and the left end portion 55c, but the inclined portion 55e may be formed by cutting out from the left end portion 55c to the right end portion 55d. it can. In such a case, it is necessary to detect the CCD detection value 1 by the inclined portion 55e, and the detection accuracy may be reduced, or data processing such as calculation of the vertical distance dX and the horizontal distance dY may be complicated. There is. Therefore, considering this viewpoint, as shown in the present embodiment, it is preferable to form the inclined portion 55e between the upper and lower end portions 55b and the left end portion 55c.

  Further, by making the whiteness of the holding member 57 smaller than the threshold value I, the boundary between the reflective surface 55a of the white reference plate 55 and the other portions can be made clearer. Thereby, the rising edge of the waveform of the CCD detection value can be clarified, and the pixel number difference dD can be detected with higher accuracy, so that the reading position can be detected with higher accuracy. The threshold value I can be set as appropriate as long as the white color reference data can be created by the CCD sensor 7.

  However, the holding member 57 is not an essential component of the present invention, and may be configured without using the holding member 57. In the present embodiment, since the black holding member 57 is used, the difference in whiteness from the white reference plate 55 can be increased, and the reading position can be detected with higher accuracy. In addition, the holding member 57 is box-shaped here, but may be other cylinders, for example.

  In the present embodiment, the white reference plate 55 is used. However, for example, white reference paper can be used as long as white reference data can be created. Further, in this embodiment, the inclined portion 55e is formed on the reflecting surface 55a by cutting the white reference plate 55 obliquely, but in addition, the reflecting surface 55a is painted black or covered with a black tape or the like. The part 55e can also be formed.

  In the present embodiment, the left end 55c of the upper and lower end portions 55b of the white reference plate 55 is cut out, but the right end 55d (upper right and lower right corners in FIG. 4) is cut out to form the inclined portion 55e. You can also. In addition, the inclined portion 55e can be formed by cutting out both the left end portion 55c and the right end portion 55d in the upper and lower end side portions 55b.

  Further, in this embodiment, since the inclined portions 55e are formed on both the upper and lower end portions 55d, the CCD detection value having a pixel region indicating a white signal at the center in the vertical direction and a pixel region indicating a black signal at both ends. Thus, the reading position can be detected more reliably. However, the inclined portion 55e can be provided only in one of the upper and lower end portions 55d.

  In the present embodiment, the reflected light from the white reference plate 55 is read by the CCD sensor 7, and the reading position of the CCD sensor 7 on the white reference plate 55 is detected based on the detection value of the CCD sensor 7. The difference in the scanning direction of the reflected light can be expressed as a pixel number difference dD of the detection value of the CCD sensor 7, and the reading position by the CCD sensor 7 on the white reference plate 55 can be detected based on the detection value.

  Thereby, the reading position by the CCD sensor 7 can be detected appropriately. Further, based on the detection result, the reading position by the CCD sensor 7 is set as the reference reading position of the white reference plate 55, and by appropriately reading the reference reading position, appropriate white reference data can be created, and the image Sufficient quality can be secured.

  In this embodiment, as shown in FIG. 6, the reference reading position is set between the scanning lines A2 and A3 (inclined portion 55e), but the reference reading position is set between the scanning lines A1 and A2. You can also In such a case, for example, by first scanning the scanning lines A1 to A3, the position information of the reading position on the white reference plate 55 is acquired, and the reference set between the scanning lines A1 and A2 based on the position information. The reading position can be read by the CCD sensor 7.

  In this embodiment, the case where the signal 255 is detected as the white signal indicating the threshold value I or more and the signal 0 is detected as the black signal that is less than the threshold value I is described. It is not particularly limited to 255. Further, the black signal only needs to be less than the threshold value I, and is not particularly limited to the signal 0.

  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 embodiment, the dedicated control unit 60 for reading the electrical signal output from the CCD sensor 7 as image data is provided, but 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 multifunction peripheral is shown here, but the present invention is an image forming apparatus of another type such as an analog type copying machine or a color copying machine. Of course, the present invention can also be applied to an image scanner separate from the image forming apparatus.

  An image reading apparatus according to the present invention includes a light source that illuminates a document in a scanning direction, a mirror that guides reflected light from the document as image light, and a scanning unit that is movable in the sub-scanning direction, and is guided by the scanning unit. A photoelectric conversion member that converts the image light into an electrical signal, and a white reference member, irradiates the white reference member with the light source, and reads reflected light from the white reference member by the photoelectric conversion member. In the image reading apparatus for creating data, the white reference member has a substantially rectangular reflecting surface arranged along the scanning direction, and at least one end of the reflecting surface in the scanning direction has the An inclined portion having a shape in which at least one end portion in the sub-scanning direction is cut out obliquely is formed.

  As a result, the reflected light from the white reference member can be regularly different in the scanning direction according to the reading position of the photoelectric conversion member in the white reference member in the sub-scanning direction. Since it is possible to detect the reading position in the sub-scanning direction of the photoelectric conversion member in the white reference member by detecting by the photoelectric conversion member, the reading position by the photoelectric conversion member in the white reference member is appropriately detected and appropriate reading is performed. White reference data can be created at the position, and image quality can be sufficiently secured.

  Further, by setting the inclination angle of the inclined portion with respect to the sub-scanning direction to about 45 °, the difference in the scanning direction in the reflected light read by the photoelectric conversion member can be made substantially equal to the difference in the sub-scanning direction. The reading position by the photoelectric conversion member can be detected more efficiently.

  Further, the white reference member is fitted and held, and by providing a holding member whose opening end is arranged along the outer periphery of the reflecting surface, the whiteness of the holding member is made smaller than a predetermined threshold value, Since the boundary between the reflective surface of the white reference member and the other part can be clarified and the difference in the scanning direction of the reflected light from the white reference member can be clarified, the detection accuracy by the photoelectric conversion member is increased. The reading position by the photoelectric conversion member can be detected with higher accuracy.

  Further, the reflected light from the white reference member is read by the photoelectric conversion member, and the position of the reflected light read by the photoelectric conversion member is detected by detecting the reading position of the photoelectric conversion member in the white reference member based on the detection value of the photoelectric conversion member. Since the difference in the scanning direction can be expressed as the difference in the detection value of the photoelectric conversion member, the reading position in the sub-scanning direction can be properly detected, and appropriate white reference data can be created, ensuring sufficient image quality. it can. Further, by mounting the image reading device, an appropriate white reference data can be created, and an image forming device capable of sufficiently ensuring image quality can be obtained.

1 is a front sectional view showing an internal configuration of an image forming apparatus on which a document conveying device of the present invention is mounted. These are front sectional views showing the internal configuration of the image reading apparatus of the present embodiment. These are top views showing an internal configuration of the image reading apparatus of the present embodiment. FIG. 4 is a top view showing the white reference plate of FIG. 3. FIG. 5 is an enlarged view showing the periphery of a region S (dashed line) in FIG. 4. These are figures which show the relationship between the reading position of the CCD sensor in the sub-scanning direction on the white reference plate and the detection value of the CCD sensor. FIG. 3 is a block diagram illustrating an example of a control path of the image reading apparatus.

Explanation of symbols

1 lamp (light source)
7 CCD sensor (photoelectric conversion member)
8 First carriage (scanning means)
9 Second carriage (scanning means)
21 Image reader 55 White reference plate (white reference member)
55a Reflective surface 55b Upper end, lower end 55c Left end 55d Right end 55e Inclined portion 60 Control unit 61 Storage unit 100 Image forming apparatus R1 First image reading unit R2 Second image reading unit W White reference member Sub-scanning direction length L Scanning direction of sub-scanning direction and sub-scanning direction length A1 to A3, As scanning line

Claims (3)

Scanning means having a light source for illuminating the document in the scanning direction and a mirror for guiding reflected light from the document as image light, and movable in the sub-scanning direction;
A photoelectric conversion member that converts image light guided by the scanning means into an electrical signal;
A white reference member;
The white reference member is irradiated with the light source, reflected light from the white reference member is read by the photoelectric conversion member, white reference data is created, and shading correction is performed.
The white reference member has a substantially rectangular reflecting surface arranged along the scanning direction,
At least one end portion in the scanning direction of the reflecting surface is formed with an inclined portion having a shape in which at least one end portion in the sub-scanning direction is cut out obliquely,
The white reference member is fitted and held, and a holding member in which an open end is arranged along the outer periphery of the reflective surface is provided,
Whiteness of the holding member, rather smaller than a predetermined threshold value,
The reflected light from the inclined portion of the white reference member is read by the photoelectric conversion member, and the reading position of the photoelectric conversion member in the white reference member is detected based on the detection value of the photoelectric conversion member. Reader.   The image reading apparatus according to claim 1, wherein an inclination angle of the inclined portion with respect to the sub-scanning direction is approximately 45 °. An image forming apparatus comprising the image reading apparatus according to claim 1 .

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