JP2007028553A - Image reading apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus A which can easily detect an edge of a white sheet member 16 from the reading result of scanning an image reading sensor 5 and which can accurately determine the position of the image reading sensor 5, based on the detected edge position. <P>SOLUTION: In an image reading sensor 5, illumination elements 6 are arranged on the upstream side and a downstream side sandwiching a SELFOC lens 7, and both the illumination elements 6 on the upstream side and the downstream side are illuminated at skimming. However, before starting the skimming, the image reading sensor 5 is scanned with the illumination element 6 on the upstream side being turned on and the illumination element 6 on the downstream being turned off, so that edge shadow 17 of a white sheet member 16 is detected from the output variation of the image reading sensor 5. The image reading sensor 5 is further shifted by a predetermined distance from a detection position of the shadow 17, so that a position 2 mm, on the upstream side of a platen roller 12, is determined accurately. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention includes an image reading apparatus mounted on an image forming apparatus such as a printer, a fax machine, a copier, or a multifunction machine, an image reading apparatus that inputs image information to a computer or an office machine, and the image reading apparatus mounted thereon or The present invention relates to a connected image forming apparatus.

  2. Description of the Related Art Image reading devices that are mounted on image forming apparatuses such as printers, fax machines, copiers, and multifunction machines and read image images of originals and image reading devices (scanners) that input image information to computers and office machines have been put into practical use. In some cases, an image reading apparatus is mounted on a copying machine, a multifunction machine, or the like, or connected as a purchase option (so-called option).

  Patent Document 1 shows an image reading device mounted on an image forming apparatus. In this image reading apparatus, a reading unit that reads a line image is scanned along a document placed on a glass surface to scan a book image that reads an image on the document surface, and a document conveyed by a document conveying device (a so-called ADF) is fixed. It is possible to perform a continuous reading with a reading unit at the same position.

  In the image reading apparatus disclosed in Patent Document 1, a cylindrical roller is disposed above a glass plate that supports an image surface of a document, and the document is allowed to pass between the glass plate and the cylindrical roller. A reading unit arranged on the opposite side of the cylindrical roller across the glass plate reads the belt-like image reading range of the conveyed document surface through the glass plate.

  In the image reading apparatus disclosed in Patent Document 1, the reading unit and the cylindrical roller are displaced in the conveying direction by providing a belt-like reflecting member (white sheet member) on the upstream side in the conveying direction so as to partially overlap the cylindrical roller. The luminance change of the read image at the time is suppressed.

JP 2003-222959 A

  In the image reading apparatus disclosed in Patent Document 1, the original conveying device (ADF) is rotated up and down when the original is placed on the book reading glass surface. As a result, there is a possibility that the cylindrical roller on the document conveying device side and the reading unit below the glass plate are displaced in the conveying direction.

  In addition, the image reading apparatus disclosed in Patent Document 1 shares a reading unit used for flow reading with book reading, and moves the reading unit from the flow reading position to the book reading origin position to move under the book reading glass. By scanning, the image surface of the original is read. Therefore, when the reading unit is returned to the flow reading position after the book reading is completed, the cylindrical roller and the reading unit may be displaced.

  Therefore, the positional relationship between the reading unit and the cylindrical roller is determined by detecting the edge of the reflecting member by moving the reading unit below the glass plate for reading, and the reading unit is moved to a predetermined reading position based on the determination result. It has been proposed to start image reading by the flow reading method after precise positioning.

  However, in the reading unit shown in Patent Document 1, a pair of illumination members are arranged on the upstream side and the downstream side in the document conveyance direction with the optical system for reading interposed therebetween, and both the cylindrical roller and the reflecting member have reflectance. Is a white surface close to 100%, it is not easy to image-recognize the edge line of the reflecting member from the read image illuminated equally by the pair of illuminating members.

  Further, since the reading unit shown in Patent Document 1 has a shallow depth of focus of the reading optical system, in the optical system focused on the image surface of the document, the edge of the reflecting member deviates from the depth of focus and becomes a blurred image. If the edge contrast is not so strong, the edge cannot be detected accurately.

  According to the present invention, the edge of the reflecting member can be easily detected from the reading result of the reading unit, and the position of the reading unit is accurately determined based on the detected edge of the reflecting member. An object of the present invention is to provide an image reading apparatus that can be accurately positioned.

  The image reading apparatus according to the present invention includes a transparent member that supports an image surface of a conveyed document, a back surface supporting unit that supports the back surface of the document, and is capable of holding the document at a distance from the transparent member. A reading unit that is disposed on the opposite side of the back surface supporting unit with a transparent member interposed therebetween, and a reflecting member that is partially overlapped with the back surface supporting unit as viewed from the reading unit side; The image reading apparatus includes a plurality of illumination elements that can illuminate an image reading range, and when detecting the reflecting member that overlaps the back surface support unit, some of the illumination elements in the plurality of illumination elements are It is provided with a control means for turning on brighter than other illumination elements.

  In the image reading apparatus of the present invention, the document is passed through the space between the transparent member and the back surface supporting means, and the reading means at a fixed position reads and reads the image surface of the document. In addition, the control unit scans the reading unit in the absence of a document, and sets a special illumination condition that is different from that during the continuous reading when reading the back surface supporting unit and the reflecting member. This special illumination condition is an illumination condition in which some illumination elements in the plurality of illumination elements are brighter than other illumination elements, and the reflecting member is more easily detected than the illumination conditions during the flow reading.

  Therefore, it is possible to detect the reflecting member more advantageously than in the case of following the illumination condition at the time of flow reading as it is.

  And a control means can set the illumination conditions in which a dark shadow is formed in the edge of a reflection member, and can identify the edge of a reflection member based on the reading result on this illumination condition. At this time, since the contrast of the edge is increased by the dark shadow, the boundary can be identified reliably and precisely as compared with the case of using the reading result under the illumination condition in which a thin shadow is formed or the illumination condition in which no shadow is formed.

  In other words, a reading result in an illumination state in which a specific illumination element (or a specific group of illumination elements) that meets the above-described illumination condition is selected from a plurality of illumination elements and lighted brighter than other illumination elements. Therefore, it is possible to easily and accurately identify the edge of the reflecting member that overlaps the back surface support means, rather than using the reading result in an illumination state in which all the lighting elements are uniformly turned on.

  Therefore, even when the reading optical system has a shallow depth of focus and the edge of the reflecting member deviates from the depth of focus and the read image is blurred, the edge of the reflecting member can be easily identified from the reading result, and the identified reflection Since the position recognition accuracy of the reading unit based on the edge of the member is increased, the reading unit can be more accurately positioned with respect to the back surface supporting unit.

  FIG. 1 is an explanatory diagram of a configuration of a copying machine including an image reading apparatus according to the present embodiment.

  As shown in FIG. 1, the image reading apparatus A is arranged on the upper part of the image forming apparatus B to constitute a copying machine C. The image reading apparatus A reads an image of a document, converts the image into an electric signal, and forms image data based on the electric signal. The image forming apparatus B forms an image on a sheet based on an electrical signal or image data of the image.

<Image forming apparatus>
The image forming apparatus B operates the exposure unit 23 based on the electrical signal or image data of the image to form an electrostatic latent image on the surface of the rotating photosensitive drum 21. The electrostatic latent image is developed (toner is supplied) by the developing device 24 to become a toner image.

  Thereafter, the sheet P is supplied between the photosensitive drum 21 and the transfer charger 25 at the same timing by the conveying roller 31, and the sheet P comes into contact with the photosensitive drum 21 and passes through the separation charger 26, whereby the photosensitive drum 21 is exposed. A toner image is transferred from the body drum 21 to the sheet P.

  The cleaner 27 cleans the surface of the photosensitive drum 21 to which the toner image has been transferred, and the charger 22 charges the surface of the photosensitive drum 21 in preparation for the next exposure.

  On the other hand, the sheet P to which the toner image has been transferred is conveyed to the fixing device 29 by the conveying unit 28, and the toner image is fixed on the surface of the sheet P by being heated and pressurized by the fixing device 29. Then, the sheet P on which the toner image is fixed is discharged to the discharge tray 30.

  Under the image forming apparatus B, sheet storage portions 19a, 19b, 19c, and 19d loaded with sheets P of various sizes are arranged. The sheets P in the sheet storage portions 19 a, 19 b, 19 c, and 19 d are taken out one by one by the feeding rollers 20 a, 20 b, 20 c, and 20 d, and transferred to the conveyance roller 31.

<Image reading device>
FIG. 2 is an explanatory diagram of the configuration of the image reading device, FIG. 3 is a partially enlarged view of the image reading device, and FIG. 4 is an explanatory diagram of image reading by a flow reading method.

  The image reading apparatus according to this embodiment includes, for example, a flow-reading glass 4 that is a transparent member, a platen roller 12 that is a back surface supporting unit, an image reading sensor 5 that is a reading unit, and a white sheet member that is a reflecting member. 16, for example, an illumination element 6 that is an illumination unit or an illumination element, and a control unit 32 (in the image forming apparatus B) that is a control unit. Note that the image reading apparatus does not necessarily include a control unit, and may be configured such that, for example, an illumination element or the like is controlled by another external control unit.

  As shown in FIG. 2, the image reading apparatus A according to the present embodiment includes an ADF 2 that is an automatic document feeder on the upper part of the image reading unit 1, and the image reading unit 1 reads a document by a book reading method. A document reading unit R1 and a second document reading unit R2 that reads a document by a flow reading method are provided. The book reading method has an advantage that the degree of freedom of the form of the original is high and a book-like original or a three-dimensional object can be read. On the other hand, the flow reading method has an advantage that a large amount of sheet-like documents can be automatically processed in a short time.

  On the upper surface of the image reading unit 1, there is provided a book reading platen glass 3 on which a document of the maximum size can be placed, and a sink for supporting the document surface of the document for flow reading adjacent to the platen glass 3. A reading glass 4 is provided. The flow reading glass 4 is an elongated glass plate whose width in the depth direction is equal to that of the document table glass 3.

  An image reading sensor 5 having a bar-like appearance with a length corresponding to the width in the depth direction of the flow reading glass 4 and reading an image on the original surface of the original is disposed below the flow reading glass 4. Yes. The image reading sensor 5 can move in the left-right direction in the drawing, and can move below the platen glass 3 to scan and read a document placed on the platen glass 3.

  As shown in FIG. 3, the image reading sensor 5 is disposed at an imaging position of the illumination element 6 that illuminates the document surface through the flow-reading glass 4, the Selfoc lens 7 that projects the image of the document surface, and the Selfoc lens 7. The image sensor 8 and the like are integrally stored in the casing 9. The casing 9 is abutted against the flow reading glass 4 through a highly slidable abutting member (spacer: not shown), and the image reading sensor 5 is disposed at a predetermined distance from the document surface. . The illumination element 6 is a thin line-shaped xenon tube or the like, but may be composed of an LED that is a light source and a light guide.

  As shown in FIG. 2, the ADF 2 is attached to the upper part of the image reading unit 1 with a hinge or the like, and can be rotated up and down with respect to the image reading unit 1. The ADF 2 takes in the originals stacked on the original placement unit 10 one by one with the conveyance rollers 11a, conveys the originals with the conveyance rollers 11b, 11c, 11d, and 11e, and passes above the image reading sensor 5, thereby The document that has been read is discharged from the conveyance roller 11 f to the document discharge unit 13.

  As shown in FIG. 3, a platen roller 12 is disposed above the flow reading glass 4 to prevent the original from floating from the flow reading glass 4 during the flow reading. The platen roller 12 rotates at a constant speed from the upper surface of the flow reading glass 4 at a predetermined interval C1 (for example, 0.2 mm) to support the back surface of the document. The platen roller 12 limits the floating amount of the original surface from the flow reading glass 4 and positions the original surface of the original at the focal height of the SELFOC lens 7 so that high-quality image reading without blurring or blurring is possible. To.

  Adjacent to the platen roller 12, a band-shaped white sheet member 16 orthogonal to the conveying direction is disposed. As shown in Patent Document 1, the white sheet member 16 covers the inclined surface of the platen roller 12 and flattens the image reading range. The surface of the platen roller 12 and the white sheet member 16 are white with a reflectance of approximately 100%, and the brightness of the document surface is kept substantially constant even when the transparency of the document is different.

  As shown in FIG. 4, the image reading sensor 5 is positioned below the flow reading glass 4 so that the SELFOC lens 7 is positioned at a predetermined position upstream of the center position of the platen roller 12 by a distance X2. This stationary position is a position where there is little vibration due to the platen roller 12 applying tension to the document while avoiding dust downstream from directly under the platen roller 12.

  In the case of book reading, a document placed on the platen glass 3 is pressed against the platen glass 3 by a white pressure plate 14 attached to the ADF 2 (FIG. 2), and the image reading sensor 5 is moved at a predetermined speed in the sub-scanning direction. The original is read while being driven (left and right in FIG. 2). In the book reading method, the entire ADF 2 functions as a pressure plate for fixing the document on the platen glass 3.

  On the other hand, in the case of flow reading, the originals stacked on the original placement unit 10 of the ADF 2 in FIG. 2 are sequentially fed from the conveyance rollers 11a to the conveyance rollers 11b, 11c, and 11d, and the platen roller 12 at a predetermined speed. It is sent to below.

  As shown in FIG. 4, the image is read by the image reading sensor 5 that is stopped at the above-described reading position, with the amount of floating from the upper surface of the flow reading glass 4 limited by the platen roller 12 that rotates at a predetermined number of rotations. Read line image of surface. That is, a document conveyed at a distance between the platen roller 12 and the flow reading glass 4 is irradiated with light from the illumination element 6 to illuminate the image reading range, and the SELFOC lens 7 images an image in the image reading range. A large number of light receiving elements that are projected onto the sensor 8 and arranged linearly on the image sensor 8 read the line image. The leading edge of the document that has passed through the platen roller 12 is guided to the transport roller 11e of FIG. 2 by the jump table 15, and is discharged from the transport roller 11f to the document discharge unit 13.

  It should be noted that the document height can be set precisely below the center of the platen roller 12 and the platen roller 12 and the flow-reading glass 4 so that the document height can be set more precisely than the stationary position described above. There is a problem in that dust tends to adhere to the surface of the flow-reading glass 4 and streaks on the image when dust is attached at the reading position. Further, at a position away from the platen roller 12 upstream, floating or vibration from the upper surface of the flow reading glass 4 is likely to occur.

  Therefore, as described above, the reading position by the image reading sensor 5 is set slightly upstream from directly below the center of the platen roller 12 in order to perform stable reading while avoiding these effects.

  As shown in FIG. 4, in this embodiment, the reading position by the image reading sensor 5 is set upstream by X2 (for example, 2 mm) immediately below the center of the platen roller 12, and the stop position of the image reading sensor 5 is It is necessary to accurately position the optical axis of the SELFOC lens 7 so that it is within a range of ± 0.5 mm from this position.

  However, since the automatic document feeder 2 is configured to be rotated and opened up and down, the relative position between the platen roller 12 and the image reading sensor 5 is increased as described above due to the influence of the backlash of the hinge portion of the hinge. It is difficult to maintain with accuracy. Further, since the image reading sensor 5 is shared by the book reading method and the flow reading method, the image reading sensor 5 cannot be fixed at the flow reading position, and every time the book is read and returned to the flow reading position, the image reading sensor 5 is read. There is a possibility that the sensor 5 is displaced.

  Therefore, in the present embodiment, the control unit 32 shown in FIG. 1 scans the image reading sensor 5 to read an image with no document before starting the flow reading by the image reading apparatus A, and the reading result is displayed. The position of the image reading sensor 5 and the above-described reading position is determined to be used, and the image reading sensor 5 is moved to offset the amount of position shift, and the image reading sensor 5 is precisely positioned to the above-described reading position.

<First Embodiment>
FIG. 5 is an explanatory diagram of the illumination state when detecting the shadow of the white sheet member, and FIG. 6 is a diagram of the output level of the image reading sensor 5.

  As shown in FIG. 5, the white sheet member 16 is arranged so as to hide a part of the surface of the platen roller 12 from a position away from the predetermined amount, so that the light illuminated at the end of the white sheet member 16 As a result, a shadow 17 is generated on the platen roller 12 where the white sheet member 16 overlaps. The controller 32 moves the image reading sensor 5 in the absence of a document to detect the shadow 17 and moves the image reading sensor 5 by a predetermined distance from the position where the shadow 17 is detected, as shown in FIG. The image reading sensor 5 is stopped at a position upstream from the center position of the platen roller 12 by a distance X2.

  As shown in FIG. 6, the luminance level read by the image reading sensor 5 is minimized when the image reading sensor 5 passes the end of the white sheet member 16, and the position of the end of the white sheet member 16 is detected. The As shown in FIG. 4, the end of the white sheet member 16 is located at a distance X1 from the center position of the platen roller 12, so that the reading position separated from the shadow 17 at the end of the white sheet member 16 by a distance X2 is present. Desired.

  When viewed from above the reading position by the image reading sensor 5 (in the direction of the platen roller 12), the white sheet member 16 is arranged so as to hide a part of the platen roller 12 over substantially the entire reading area. The light irradiated at 6 and transmitted through the document is surely reflected by the white sheet member 16 or the platen roller 12 to prevent a decrease in luminance.

  By the way, the illumination element 6 is arrange | positioned so that the light quantity balance of the two illumination elements 6 may become substantially equal on both sides on both sides of the SELFOC lens 7. This is to prevent the generation of shadows due to the stepped portion of the document when reading a cardboard document such as a business card or a cut and pasted document such as scrap.

  However, when the brightness level of the white sheet member 16 and the surface of the platen roller 12 is measured while irradiating the platen roller 12 and moving the image reading sensor 5 under the platen roller 12 in the sub-scanning direction, the white sheet member 16 side The light emitted from the illumination element 6 causes a shadow 17 on the surface of the platen roller 12, but the light emitted from the illumination element 6 on the opposite side illuminates the shadow 17 and cancels it. For this reason, the luminance level read by the image reading sensor 5 is not minimized when the image reading sensor 5 passes the end of the white sheet member 16, and it is difficult to detect the center of the platen roller 12 with high accuracy.

  Therefore, as shown in FIG. 5, the image reading apparatus A of the present embodiment is characterized in that when determining the reading position, only the light source on the white sheet member 16 (upstream) side is lit to easily cause a shadow. 1, the image reading sensor 5 scans the shadow 17 of the joint between the white sheet member 16 and the platen roller 12, and detects the correct reading position from the position where the luminance level is lowered.

  When performing the flow reading, first, the detection operation of the center position of the platen roller 12 is performed. The image reading sensor 5 is driven in the sub-scanning direction up to the center of the platen roller 12 while illuminating the white sheet member 16 by lighting only the illumination element 6 on the white sheet member 16 side (upstream side in the document transport direction). . The control unit 32 continuously detects line images of the image reading sensor 5 and measures a change in luminance level from the white sheet member 16 to the surface of the platen roller 12.

  Since the white sheet member 16 is arranged so as to hide a part of the surface of the platen roller 12 from a position away from the predetermined amount, the white sheet member 16 has a shadow 17 on the platen roller 12 by the light illuminated at the end of the white sheet member 16. Occurs. At this time, since the light source on the side where the shadow 17 is diluted is turned off, the luminance level read by the image reading sensor 5 passes through the end of the white sheet member 16 as shown in FIG. Sometimes the position is minimized, and the position of the end of the white sheet member 16 is detected.

  In FIG. 6, the reading is performed by the image reading sensor 5 when the both-side light source is illuminated with the illumination elements 6 on both sides as shown in FIG. 3 and when the one-side light source is illuminated with the one-side illumination element 6 as shown in FIG. Indicates the difference in brightness level. As apparent from the diagram of FIG. 6, the luminance level of the shadow 17 is more greatly changed and the luminance level is lower when the light source is one side (lights only on the white sheet member 16 side) than when the light source is both sides. It can be seen that the range is small.

  Therefore, when the image reading sensor 5 passes the end of the white sheet member 16, the luminance level is surely minimized, and the range of decrease is small, so that the position of the end of the white sheet is accurately detected. Is done. As shown in FIG. 4, the edge of the white sheet member 16 is set at a position (for example, 5.2 mm) away from the center position of the platen roller 12 by a distance X1 (for example, 5.2 mm). 12 center positions are detected, and the image reading sensor 5 is positioned at a reading position at a distance X2 (2.0 mm upstream of the roller center) at which an optimum reading condition is obtained.

  Since the image reading sensor 5 is positioned at an optimum reading position with respect to the center position of the platen roller 12, the image reading sensor 5 is not affected by defocusing due to the floating of the document or dust adhering to the flow-reading glass 4. A quality image is read.

Second Embodiment
FIG. 7 is an explanatory diagram of an illumination state when detecting a shadow of a white sheet member in the second embodiment. The image reading apparatus according to the second embodiment includes, for example, a white pressure plate 14 that is a back surface supporting unit.

  As shown in FIG. 4, in the second embodiment, a white pressure plate 14 is disposed in place of the platen roller 12 described above. The white pressure plate 14 is formed of a white material having a small friction coefficient, and slides and supports the back surface of the document conveyed on the flow reading glass 4. Since the constituent members other than the white pressure plate 14 are the same as those in the first embodiment, the same reference symbols are attached and detailed description thereof is omitted. Further, an automatic initialization sequence in which the image reading sensor 5 is scanned to detect the brightness level, the edge of the white sheet member 16 is detected, and the image detecting sensor 5 is positioned before starting the flow reading is also the same as that of the first embodiment. Are the same.

  The second embodiment is different from the first embodiment in that, in the first embodiment, reading means capable of reading a document image by irradiating a document on the flow reading glass 4 from the illumination element 6, and the flow reading glass 4. The white sheet member 16 for reflecting the light is disposed in the vicinity of the platen roller 12 and the rotatable platen roller 12 provided at a position opposite to the illumination element 6 and the reading unit. In particular, in an inexpensive image forming apparatus or the like, a white pressure plate 14 that reflects light may be used instead of the platen roller 12. When the reading position is determined, only the light source on the white sheet member 16 side is turned on to easily cause a shadow on the edge of the white sheet member 16, and the image reading sensor 5 makes the shadow of the joint between the white sheet member 16 and the white pressure plate 14. 17 is scanned, and the reading position is detected from the position where the luminance level is lowered.

<Third Embodiment>
FIG. 8 is an explanatory diagram of an illumination state when detecting a shadow of a white sheet member in the third embodiment.

  As shown in FIG. 8, the third embodiment is different from the first embodiment in that only the illumination element 6 on the white sheet member 16 side (upstream side) is turned on when the reading position is determined in the first embodiment. Although the illumination element 6 on the platen roller 12 side (downstream side) is turned off, the third embodiment is characterized in that the light quantity of the illumination element 6 on the platen roller 12 side (downstream side) is kept low. Since other configurations and controls are the same as those in the first embodiment, the same reference symbols are attached and detailed descriptions are omitted.

  In the third embodiment, by suppressing the amount of light of the illumination element 6 on the platen roller 12 side (downstream side), the luminance level of the shadow 17 is greatly changed compared to the light sources on both sides, and the luminance level is reduced. Thus, the edge area of the white sheet member 16 is accurately detected. Therefore, the center position of the platen roller 12 is detected from the shadow 17 of the white sheet member 16, and the image reading sensor 5 is positioned 2.0 mm upstream from the center of the platen roller 12 where an optimum reading condition is obtained.

<Fourth embodiment>
In the first embodiment, the second embodiment, and the third embodiment, the image reading apparatus A mounted on the image forming apparatus B has been described as shown in FIG. The present invention can also be realized by an image forming apparatus such as a copying machine that is integrally stored in a housing of the forming apparatus and an ADF is attached to the upper part of the image forming apparatus so as to be opened and closed.

  In this way, by configuring the image forming apparatus in which the image reading apparatus is integrated, as in the above-described embodiments, it is possible to stably prevent image fluctuations by effectively preventing luminance fluctuations when the original is scanned and read. Based on this, high-quality image formation can be performed at a high speed.

<Fifth Embodiment>
In each of the above-described embodiments, an example in which the image sensor 8 is used as the image reading sensor 5 has been described. However, a reflection mirror and a CCD are used. Each embodiment can also be realized by an image forming apparatus of a type that is guided to the surface of the body drum and directly exposed.

  In the embodiment described above, in order to avoid the influence of dust on the flow reading glass 4, the reading position is set on the upstream side in the document conveying direction with respect to the position immediately below the rotation center of the platen roller 12, and the white sheet member 16 is provided on the upstream side. However, since the adhesion of dust to the flow reading glass 4 also changes depending on the shape of the original conveyance path, the reading position is set downstream of the platen roller 12 in the conveyance direction rather than just below the rotation center. Accordingly, the white sheet member 16 may be provided on the downstream side.

  Alternatively, the flow reading position may be set on both sides of the platen roller 12 directly below the rotation center, and the white sheet members 16 may be provided on the upstream side and the downstream side in the document conveyance direction.

  According to the image reading apparatus of each embodiment described above, the image reading apparatus that positions the reading position of the image reading sensor 5 at the time of flow reading with high accuracy and enables high-quality image reading by the flow reading method. Can be provided. That is, the white sheet member 16 and the vicinity of the platen roller 12 are scanned by the image reading sensor 5 and the light source balance between the upstream side and the downstream side is changed, so that the shadow 17 of the white sheet member 16 is easily generated. Therefore, the end of the white sheet member 16 can be accurately detected from the lowering of the level, and the reading position of the image reading sensor 5 in the flow reading method can be positioned with high accuracy. For this reason, blurring due to floating of the original is prevented, and high-quality images can be read without being affected by dust adhering to the flow-reading glass 4.

  In other words, the image reading apparatus A according to each embodiment allows the original to pass through the gap between the flow reading glass 4 and the platen roller 12, and the stopped image reading sensor 5 performs flow reading on the image surface of the original. 32 scans the image reading sensor 5 in the absence of a document, reads the platen roller 12 and the white sheet member 16 to detect the shadow 17, and positions the image reading sensor 5 to a predetermined position with respect to the platen roller 12.

  And since the control part 32 identifies a boundary based on the reading result on the illumination conditions in which the shadow 17 becomes dark, since the contrast of a boundary increases, it is an illumination condition in which a thin shadow is formed, or an illumination condition in which a shadow is not formed. As compared with the case of using the reading result of, the boundary can be identified reliably and precisely.

  That is, since the reading result in the illumination state in which the upstream side illumination element 6 is selected and lighted brighter than the downstream side illumination element 6 is used, the illumination state in which both illumination elements 6 are equally illuminated In addition, the boundary between the platen roller 12 and the white sheet member 16 can be identified more easily and accurately than using the reading result in the illumination state in which only the illumination element 6 on the downstream side is turned on.

  Therefore, even when the focal depth of the SELFOC lens 7 is shallow and the edge of the white sheet member 16 deviates from the focal depth and the read image is blurred, the edge of the white sheet member 16 can be easily identified from the read result. Since the position recognition accuracy of the image reading sensor 5 based on the edge of the white sheet member 16 is increased, the image reading sensor 5 can be more accurately positioned with respect to the platen roller 12, and the accurately positioned image reading sensor 5 Image reading with high reproducibility and reliability is possible.

  Since the image reading apparatus A that can perform image reading with high reproducibility and reliability is installed, the copying machine C reduces image defects due to image reading defects and performs image formation with high reproducibility and reliability. It is possible.

1 is an explanatory diagram of a configuration of a copying machine including an image reading apparatus according to an embodiment. It is explanatory drawing of a structure of an image reading apparatus. It is a partial enlarged view of an image reading apparatus. It is explanatory drawing of the image reading of a flow reading system. It is explanatory drawing of the illumination state at the time of detecting the shadow of a white sheet member. It is a diagram of the output level of the image reading sensor. It is explanatory drawing of the illumination state at the time of detecting the shadow of a white sheet member in 2nd Embodiment. It is explanatory drawing of the illumination state at the time of detecting the shadow of a white sheet member in 3rd Embodiment.

Explanation of symbols

A Image reading device (image reading means)
B Image forming apparatus (image forming means)
1 Image reading unit 2 ADF
3 Document glass 4 Flow-reading glass (transparent material)
5 Image reading sensor (reading means)
6 Lighting elements (lighting means, lighting elements)
7 Selfoc lens (reading means)
8 Image sensor (reading means)
9 Casing 12 Platen roller (Back support means)
14 White pressure plate 16 White sheet member (reflective member)
17 Shadow (Boundary)
21 Photosensitive drum (image forming means)
32 Control unit (control means)

Claims (13)

A transparent member that supports the image surface of the conveyed document;
Back surface supporting means for supporting the back surface of the document and holding the document at a distance from the transparent member;
A reading unit disposed on the opposite side of the back surface supporting unit across the transparent member, and reading the image surface;
A reflective member disposed so as to partially overlap the back surface supporting unit as viewed from the reading unit side,
Having a plurality of illumination elements capable of illuminating the image reading range;
An image comprising control means for lighting some of the lighting elements in the plurality of lighting elements brighter than other lighting elements when detecting the reflecting member overlapping the back surface supporting means. Reader.   The control means sets an illumination condition in which the shadow of the reflection member formed on the back surface support means becomes dark, and identifies an edge of the reflection member based on a reading result by the reading means under the illumination condition The image reading apparatus according to claim 1, wherein the image reading apparatus is a means.   The control means sets an illumination condition in which the shadow of the reflecting member formed on the back surface support means becomes dark by turning on some of the illumination elements and turning off the other illumination elements. The image reading apparatus according to claim 1, wherein the image reading apparatus is a unit that identifies an edge of the reflecting member based on a reading result by the reading unit under conditions. A pair of the illumination elements are arranged on the upstream side and the downstream side in the document conveying direction with the reading unit interposed therebetween,
4. The image reading apparatus according to claim 2, wherein the control means is means for realizing the illumination condition by making the illumination element on the upstream side brighter than the illumination element on the downstream side. The reading means and the illumination element are assembled so as to be integrally movable in the transport direction,
The image reading apparatus according to claim 1, wherein the control unit positions the reading unit at a predetermined position in the transport direction based on a detection result of the reflecting member.   The image reading apparatus according to claim 1, wherein the back surface support unit includes a cylindrical roller member that is rotatable in the transport direction.   The image reading apparatus according to claim 1, wherein the back surface support unit includes a planar member arranged orthogonal to the transport direction. A transparent member arranged so that the image surface of the conveyed document can pass through;
Back surface support means for supporting the back surface of the document passing over the transparent member;
A reflective member disposed partially overlapping the back surface support means from the upstream side in the document passing direction;
In an image reading apparatus comprising: a reading unit that can be moved and positioned in the passing direction or the opposite direction, and that reads the image surface through the transparent member;
The reading unit includes a pair of illuminating units that can illuminate the edge of the reflecting member overlapped with the back surface supporting unit with different brightness from the upstream side and the downstream side in the document passing direction. Image reading device.   9. The image reading apparatus according to claim 8, wherein the illumination unit on the downstream side in the passing direction can be turned off. A reading unit capable of reading a line image in a direction intersecting with a conveyance direction of a document to be conveyed;
Assembling a pair of illumination elements arranged on the upstream side and the downstream side in the transport direction with the reading unit interposed therebetween to illuminate the original so as to be movable integrally,
An image reading unit comprising: a control unit configured to read the line image while moving the reading unit by turning off the illumination element on the downstream side before reading the conveyed document by the reading unit. . Image reading means for reading an image on the image surface of the original;
In an image forming apparatus comprising: an image forming unit that forms the read image on a sheet;
An image forming apparatus according to claim 1, wherein the image reading unit is the image reading apparatus according to claim 1.   12. The image forming apparatus according to claim 11, wherein the control unit that controls the image forming unit also controls the image reading unit in common. A transparent member arranged so that the image surface of the conveyed document can pass through;
Back surface support means for supporting the back surface of the document passing over the transparent member;
A reflective member disposed partially overlapping the back surface support means from the upstream side in the document passing direction;
In an image forming apparatus comprising: a reading unit that can be positioned by moving in the passing direction or the opposite direction, and that reads the image surface through the transparent member;
The image reading apparatus includes an illuminating unit capable of illuminating the edge of the reflecting member overlapped with the back surface supporting unit brighter from the downstream side in the passing direction than from the upstream side in the passing direction. Forming equipment.

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