JP4905236B2 - Image reading apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image reading apparatus, and more particularly to a sheet-through type image reading apparatus used as an image input apparatus in a copying machine or a scanner, and an image forming apparatus including the image reading apparatus.

  Conventionally, as an image reading apparatus for optically reading an image of a document, a platen set method for reading an image of a document placed on a platen glass, and a document are conveyed one by one, and an image of the document is read during conveyance. The sheet-through method was used alone or in combination. The sheet-through method has advantages in downsizing, low cost, low noise, high-speed image reading, and high print productivity, and has become the mainstream of image reading devices in monochrome copiers and color copiers. .

  In the case of the sheet-through method, the image reading position is fixed, that is, fixed on a transparent member (long reading glass), and the reading optical system is focused on the image surface of the document conveyed through the reading glass. Due to the configuration, it is easily affected by foreign matter such as dust attached to the reading glass and residual dust, and the portion shielded by the foreign matter becomes streak image noise in the read image.

  The foreign matter adhering to the reading glass is mainly adhesive foreign matter stuck to the original, for example, adhesive tape or adhesive peel, correction liquid, ink pen of ballpoint pen, eraser scrap, etc. Easy to be transferred to the rubbing part. Further, such a sticky foreign matter does not easily peel off and has a problem of causing image noise. In addition, there is a problem that floating foreign matters such as paper dust and dust in the air scattered from the conveyed document stay on the reading glass and cause image noise. In the sheet-through method, since the document is conveyed while being held in contact with a guide plate by a roller or the like, stress is applied to the document mainly composed of paper, and paper powder falls from the document surface.

  Therefore, Patent Document 1 discloses a measure for conveying a document in a non-contact state with respect to a reading glass. In this non-contact conveyance method, the adhesive foreign matter can be prevented from adhering to the reading glass. Further, since the trailing edge of the conveyed document loses its support and comes into contact with the reading glass, it also has an effect of wiping off floating foreign matters on the document glass.

  However, the range of contact between the trailing edge of the document and the reading glass varies greatly depending on the curl state of the document itself and the document conveying speed, and the document trailing edge can reliably wipe off foreign matter remaining on the reading glass. Not exclusively.

As a measure for removing foreign matter from the reading glass, as described in Patent Document 2, a step-forming member that makes the document non-contact on the reading glass and a capturing member that captures the foreign matter are provided between the reading position. It has been proposed. However, with this measure, maintenance such as replacement and cleaning of the capture member is complicated.
JP-A-9-307695 Japanese Patent Laid-Open No. 2001-223832

  Accordingly, an object of the present invention is a sheet-through method in which a document is conveyed in a non-contact state with a transparent member for reading, and foreign matters remaining on the transparent member can be effectively eliminated. It is an object of the present invention to provide an image reading apparatus and an image forming apparatus that can prevent occurrence of noise.

In order to achieve the above object, an image reading apparatus according to the present invention comprises:
A document conveying means for sending out the documents one by one and passing the reading position;
Reading means for optically reading an image of a document conveyed at the reading position;
A transparent member disposed between the document conveyed at the reading position and the reading unit;
Than said reading position are disposed on the upstream side of the document feed direction, by conveying the document conveyed in a state with the transparent member and the gap does not contact the document conveyed the reading position on the transparent member orientation A step forming member to be held in ,
Drive means for reciprocating the transparent member along the document conveying direction;
After the leading edge of the document has passed the reading position, and control means for the trailing edge of the document is to start moving in the original conveying direction of the transparent member when in proximity to said reading position,
Equipped with a,
Foreign matter that has moved in the document transport direction due to the movement of the transparent member is removed from the reading position by the rear end of the document that is separated from the step forming member and contacts the transparent member as the document is transported.
It is characterized by.

  In the image reading apparatus according to the present invention, since the document transported to the reading position is transported while maintaining a posture not in contact with the transparent member, it is possible to prevent the sticky foreign matter peeled off from the document from adhering to the transparent member as much as possible. The Further, when the trailing edge of the document passes through the reading position, the trailing edge loses support and comes into contact with the transparent member. By moving the transparent member in the document transport direction until the trailing edge of the document passes through the reading position, the trailing edge of the document that has lost its support reliably contacts the transparent member and remains on the transparent member. Foreign matter is eliminated. Thereby, it is possible to prevent the occurrence of streak noise in the read image. Further, since the transparent member is cleaned with the document itself and no cleaning member or capturing member is provided in particular, there is no need for maintenance.

An image reading apparatus according to the present invention, the control means, the transparent member is moved before passing through the rear end reading position of originals, the original until it reaches the tip reading position of the next document It may be returned to the position.

  In addition, a document detection sensor arranged upstream of the reading position in the document conveyance direction may be provided, and the control unit may start the movement of the transparent member with reference to the document trailing edge detection timing by the document detection sensor.

By the way, the position where the trailing edge of the document contacts the transparent member varies depending on the state of the trailing edge of the document (difference in curl amount), the document conveyance speed, the thickness of the document (basis weight), and the like. Therefore, it is preferable to control the movement amount of the transparent member so that the transparent member is selectively moved to a plurality of positions in the document conveyance direction.

An image forming apparatus according to the present invention is
The image reading device;
An image forming unit that outputs an image read by the image reading device as a visible image on a recording medium in a state in which an image defect region that causes an image formed on an end of the read document to be lost is formed. ,
Wherein, between the rear end of the document corresponding to the image missing region is you pass the reading position, moving the transparent member in the original conveying direction,
It is characterized by.

  When the transparent member moves, there is a possibility that residual foreign matter on the transparent member moves to the reading position and is read as an image. In addition, since an image formed on the edge of the document may be read in a disorderly manner, it is usually an image defect area. Therefore, even if foreign matter remains on the transparent member that has moved to the reading position, it has been read by substantially overlapping the timing at which the transparent member moves with the timing for reading the image defect area (the trailing edge of the document). Appearing as noise in the image is prevented as much as possible.

  Embodiments of an image reading apparatus and an image forming apparatus according to the present invention will be described below with reference to the accompanying drawings. In each embodiment, the same parts and the same parts are denoted by the same reference numerals, and redundant description is omitted.

(Overall configuration of copier, see Fig. 1)
FIG. 1 shows an appearance of a copying machine 1 as an embodiment of an image forming apparatus according to the present invention. The copying machine 1 forms an image on a recording medium (usually plain paper is used) by a conventionally known electrophotographic method. The copying machine 1 includes an image reading device 10 in an upper stage portion. The read original image is printed on a sheet by the image forming unit 3 of the main body 2. The sheets are stacked and housed in the sheet feeding cassette 4, fed one by one, printed by a well-known image forming process, and then ejected to the sheet ejection unit 5 in the direction of arrow X.

(Overall configuration of image reading apparatus, see FIGS. 2 to 5)
FIG. 2 shows the image reading apparatus 10. The image reading device 10 includes a platen set method for reading an image of a document (not shown) placed on the platen glass 11 and a sheet-through method for reading the document D conveyed by the automatic document conveying device 20. In addition, a reading optical system (scanner) 50 is installed.

  Reading of an image by the platen set method is performed, for example, by irradiating a document placed on the platen glass 11 with a lamp 53 such as a rare gas fluorescent lamp, and reflecting light from the document surface via mirrors 54, 55 and 56. The light is incident on the imaging lens 57 and further imaged on the imaging unit (CCD color line sensor) 58. The lamp 53 and the mirror 54 are mounted on the first slider 51, and the mirrors 55 and 56 are mounted on the second slider 52, and are movable in the sub-scanning direction Y, respectively.

  On the other hand, the automatic document feeder 20 includes a plurality of roller pairs 21, 22, 23, and 24. The documents D are picked up one by one from the tray 25, fed from the roller pairs 21, 22, 23 onto the reading glass 12, and read by the reading optical system 50 set immediately below the reading position A. 24 is discharged onto the tray 26.

  The image data read by the imaging unit 58 is transferred to the image processing unit 60 shown in FIG. 5 and further transferred to the control unit 61 that controls the copying machine 1 and the image reading apparatus 10. The control unit 61 controls the laser scanning unit 62 and the image forming drive mechanism 63 of the main body unit 2 to form an image on a sheet by a known electrophotographic method. The control unit 61 further controls a drive mechanism 65 such as the reading optical system 50 of the image reading apparatus 10. The document image reading process by the platen set method or the sheet through method and the image forming process by the electrophotographic method are well known, and detailed description thereof is omitted.

  FIG. 3 shows an enlarged cross-section of a document reading unit using the sheet-through method. Around the reading glass 12, document guide plates 25a, 25b, 26a, and 26b and a guide 27 for scooping up the document that has passed the reading position A are arranged. A guide sheet 30 that functions as a step forming member is attached on the reading glass 12 upstream of the reading position A in the document conveying direction B so that the document being conveyed does not come into contact with the reading glass 12. It is affixed to the plate 35 and arranged in contact with the surface of the reading glass 12.

  In addition, a sensor SE1 for detecting a conveyed document is disposed on the upstream side of the guide sheet 30. The sensor SE1 is turned on when the leading edge of the document passes, and turned off when the trailing edge passes.

  Further, the reading glass 12 is held by a holding member, and as shown in FIG. 4, a clamp arm 15 connected to the shaft 14 of the holding member 13 rotates the eccentric cam 16 by a drive motor (stepping motor) 17. As a result, the paper moves back and forth in parallel with the document conveyance direction B. The amount of movement of the reading glass 12 can also be controlled by the number of drive pulses of the drive motor 17. The movement timing of the reading glass 12 will be described in detail later.

  In the image reading apparatus 10 having the above-described configuration, a document conveyed to the right while sliding on the upper surface of the guide sheet 30 by the conveying roller pairs 23 and 24 has a reading position A at a predetermined height depending on the thickness of the guide sheet 30. The reading glass 12 is conveyed in a non-contact state, and the document image is read by the reading optical system 50 through the reading glass 12.

  The guide sheet 30 is made of, for example, a material having a thickness (step) of 0.65 mm and a low sliding resistance (preferably a friction coefficient μ: 0.3 or less) such as ultrahigh molecular weight polyethylene. If a material having low sliding resistance is used, the load when the reading glass 12 is moved is reduced, and troubles such as generation of abnormal noise can be prevented.

  The document guide plate 25b regulates the posture of the document D being conveyed, and, for example, the clearance from the reading glass 12 is set to 1.2 mm in order to perform stable image reading. If the gap with the reading glass 12 is increased to 1.4 mm or more, the posture of the document D being conveyed is not stabilized and the linearity is deteriorated, and the density of the read image varies.

  Here, the behavior of the document passing through the reading position A will be briefly described. The document D is guided on the surface of the guide sheet 30 and sent onto the reading glass 12, and is conveyed in a state having a gap from the reading glass 12 by the thickness of the guide sheet 30. When the rear end portion of the document D leaves the end portion 30 a of the guide sheet 30, it loses its support and falls onto the reading glass 12 and comes into contact with the reading glass 12.

(Existence of residual foreign matter, see FIG. 6)
By the way, in the image reading apparatus 10, since the document is conveyed in a non-contact state with respect to the reading glass 12, it is prevented as much as possible that adhesive foreign matter from the document is transferred to the reading glass 12. It falls on the reading glass 12. On the other hand, foreign matters such as paper dust fall on the surface of the reading glass 12 from the original, and many of them are caught in the original being conveyed and discharged from the reading glass 12. However, some 10% of foreign matters such as paper dust and dust in the air remain on the reading glass 12.

  As shown in FIG. 6A, the trailing edge of the document D loses its support when it passes through the leading edge of the guide sheet 30, contacts the reading glass 12, and wipes off the remaining foreign matter in the contact area C1. However, the remaining foreign matter in the non-contact area C2 is not cleaned. The document D shown in FIG. 6A is in a normal state where the trailing edge is not curled, and if the reading position A is set to the contact area C1, there is a possibility that noise will occur in the read image. There is no. Further, as shown in FIG. 6B, when the trailing edge of the document D is curled downward (face curl), the contact area C1 becomes large and the non-contact area C2 becomes relatively small. Therefore, also in this case, if the reading position A is set in the contact area C1, there is no possibility that noise will occur in the read image.

  On the other hand, as shown in FIG. 6C, when the trailing edge of the document D is curled upward (back curl), the contact area C1 becomes smaller and the non-contact area C2 becomes relatively larger. In addition, although the curved part D1 contacts the reading glass 12, a foreign material cannot be wiped off by such an antinode. Contact / non-contact means whether or not the rear end of the document having a cleaning effect comes into contact. In the case shown in FIG. 6C, the non-contact area C2 spreads to the reading position A, and streak noise is generated by the imaging unit 58 reading the remaining foreign matter. Further, the non-contact area C2 changes not only according to the curled state of the trailing edge of the document but also according to the document conveyance speed, the thickness (basis weight) of the document, and the like. If the document conveyance speed is increased or the document is thin, the non-contact area C2 is enlarged so as to include the reading position A, and noise due to residual foreign matter is generated in the read image.

(Refer 1st Example and FIGS. 7-11)
Therefore, in the first embodiment, assuming that the state shown in FIG. 6C occurs, as shown in FIG. 7A, the contact area C1 in the back curl state (cleaned) is obtained. The reading glass 12 is moved in advance in the transport direction B by the dimension L1 so that the area) includes the reading position A. In this state, the document D is conveyed and an image is read. For example, when it is assumed that the back curl of the rear end portion of the document D is 4 mm, the moving amount L1 before the start of reading is set to 2 mm. As a result, the original image can be read without any foreign matter.

  Next, as shown in FIG. 7B, the reading glass 12 is moved in the transport direction B by the dimension L <b> 1 until the trailing edge of the document D passes the reading position A. In this case, the non-contact area C2 on the reading glass 12 partially enters the reading position A. However, when the rear end of the document D comes into contact with the reading glass 12, residual foreign matter is eliminated in the contact area C1. Then, the reading glass 12 is returned to the original position (see FIG. 7A) until the leading edge of the next original reaches the reading position A.

  Specifically, the distance L2 from the tip of the guide sheet 30 to the reading position A is 6 mm, and the distance L3 from the tip to the tip of the reading glass 12 is, for example, 13 mm. Assuming that the back curl of the document D is 4 mm, the non-contact area C2 is 6.5 mm, and a non-contact area corresponding to the distance L2 is also generated at the front end portion. According to this specific example, in a state where the document D is conveyed (see FIG. 7A), the contact area (cleaned area) C1 is set to the reading position A, and the document image is intervened with foreign matter. It is read without.

  That is, in the first embodiment, image noise is prevented from occurring by moving the reading glass 12 in the transport direction B during the reading operation of the original image. In this case, it is preferable to start the movement of the reading glass 12 when the trailing edge of the document approaches the reading position A. The trailing edge of the document is detected by the sensor SE1, and the control unit 61 drives the motor 17 based on this detection signal to move the reading glass 12 in the document transport direction B. Further, the reading glass 12 is returned to the original position until the leading edge of the next document reaches the reading position A. This control is also performed based on the detection signal of the sensor SE1 for the leading edge of the next document.

  Here, the timing of detecting the leading edge of the document and moving the reading glass 12 to the upstream side in the transport direction B by the distance L1 will be described. As shown in FIG. 8, the reading glass 12 is moved a distance while the leading edge of the document D is transported a distance L4 with respect to a distance L4 (40 mm) from the leading edge detection point of the document D to the reading position A by the sensor SE1. Move upstream by L1 (2 mm). If the document conveyance speed is v, the movement of the reading glass 12 2 mm upstream is completed after t1 = L4 / v seconds from the leading edge detection timing of the sensor SE1.

  Even when the interval m between continuously conveyed documents is narrowed to improve image reading productivity, the reading glass 12 is moved upstream after t1 ′ = (L4−m) / v seconds from the detection timing of the leading edge of the document. By doing so, the image reading of the preceding document is reliably completed, and the reading glass 12 moves after the timing when the cleaning of the reading glass 12 by the trailing edge of the document is completed. Can be removed. Assuming that the interval m between continuously conveyed documents is 20 mm and the document conveying speed v is 177 mm / s, the reading glass 12 is moved after t1 ′ = (L4−m) /v=0.113 s from the leading edge detection timing of the document. By moving it, the reading position A can be maintained in the cleaning completed state.

  Next, the timing for detecting the trailing edge of the document and moving the reading glass 12 to the downstream side in the conveyance direction B by the distance L1 will be described. As shown in FIG. 9, while the rear end of the document D is transported the distance L4 with respect to the distance L4 (40 mm) from the trailing edge detection point of the document D to the reading position A by the sensor SE1, the reading glass 12 is used. Is moved downstream by a distance L1 (2 mm). If the document conveyance speed is v, the movement of the reading glass 12 2 mm downstream is completed after t2 = L4 / v seconds from the trailing edge detection timing of the sensor SE1.

  As described above, by moving the reading glass 12 to the downstream side after t2 = L4 / v seconds from the detection timing of the trailing edge of the document, there is a possibility that the moving timing of the reading glass 12 is delayed as much as possible and foreign matter remains. The timing at which a certain non-contact area C2 moves to the reading position A can be delayed to prevent the remaining foreign matter from being read as noise as much as possible.

  In the copying machine 1, normally, as shown in FIG. 10, the four end portions of the recording medium M are image defect areas M1, M2, M3, and M4. In FIG. 10, the image forming area is indicated by hatching. The reason why the defect areas M1 to M4 are provided is that the image formed on the edge of the document may be read out of order. When the image defect area M2 at the trailing edge has a width of p (5 mm), the reading glass 12 is moved after t2 ′ = (L4−p) /v=0.198 s from the trailing edge detection timing of the document. Even if foreign matter remains in the non-contact area C2 on the reading glass 12 and is read as streak noise, the noise is generated in the image defect area M2, and thus appears as image noise on the recording medium M. Never do.

  FIG. 11 shows a main part of the control procedure of the image reading apparatus 10 according to the first embodiment. Here, when it is detected that a document is loaded on the tray 25 (YES in step S1), a document transport sequence is started (step S2), and when the leading edge of the document is detected by the sensor SE1 (in step S3). YES), the timer T1 is started (step S4). When the timer T1 counts the time t1 '(YES in step S5), the motor 17 is driven forward by the number of pulses P (step S6). The reading glass 12 moves to the upstream side in the conveyance direction B by a distance L1 (2 mm) by forward rotation driving with the number of pulses P. When the timer T1 counts the time t1 (YES in step S7), reading of the document image is started (step S8).

  Next, when the trailing edge of the document is detected by the sensor SE1 (YES in step S9), the timer T2 is started (step S10). When the timer T2 counts the time t2 '(YES in step S11), the motor 17 is driven in reverse by the number of pulses P (step S12). The reading glass 12 moves downstream in the transport direction B by a distance L1 (2 mm) by reverse rotation driving of the number of pulses P. When timer T2 counts time t2 (YES in step S13), reading of the document image is stopped (step S14).

(Refer 2nd Example and FIGS. 12-14)
Incidentally, the range in which the trailing edge of the document contacts the reading glass 12 varies depending on the curl amount at the trailing edge of the document. Therefore, it is desirable to change the movement amount of the reading glass 12 according to the curl amount. As shown in FIG. 12, when the length of the non-contact area on the upstream side from the front end of the guide sheet 30 is Y1, and the length from the non-contact area on the downstream side is Y2, the curl amount h at the rear end of the document is 3 mm. The lengths Y1 and Y2 corresponding to 4 mm and 5 mm and the required movement amount L1 are shown in Table 1 below. It is preferable that the required movement amount L1 is 1 mm or more away from the range that cannot be cleaned.

  As can be seen from Table 1, the length Y2 up to the downstream uncleanable range hardly changes depending on the curl amount h. Since the distance Y3 from the reading position A to the downstream non-contact area decreases as the movement amount L1 increases, there is a high possibility that foreign matter remains at the reading position A.

  In the second embodiment, the curl amount at the trailing edge of the document is measured, and the movement amount L1 of the reading glass 12 is controlled based on the measured curl amount h. Specifically, as shown in FIG. 13, actuator-type sensors SE2 and SE3 are provided in the U-turn conveyance path between the conveyance roller pairs 22 and 23 in order to measure the curl amount. The sensor SE2 is turned on when the curl amount is 3 mm or more, and the sensor SE3 is turned on when the curl amount is 5 mm or more. Since the original is conveyed along the outer guide plate 28a in the U-turn conveyance path, the curl amount can be measured by providing the sensors SE2 and SE3 on the inner guide plate 28b.

  The relationship between the curl amount h, the on / off of the sensors SE2 and SE3, and the movement amount L1 is as shown in Table 2 below. Based on the measured curl amount h, the movement amount L1 of the reading glass 12 is calculated with reference to Table 2, and the number of drive pulses of the motor 17 is controlled.

  FIG. 14 shows a main part of a control procedure for setting the movement amount L1 in the image reading apparatus 10 according to the second embodiment. Here, the on / off states of the sensors SE2 and SE3 are detected (steps S21 and S22), the curl amount h is calculated based on the table 2 (step S23), and the optimum movement amount L1 is selected (step S24). ). If the measured curl amount h is the same as that of the preceding document (YES in step S25), it is not necessary to change the movement amount L1 (step S26). If the movement amount L1 needs to be corrected (NO in step S25), the forward rotation drive pulse number P of the motor 17 is set to the corrected pulse number P '(step S27).

  Further, the position where the trailing edge of the document contacts the reading glass 12 differs depending on the document conveyance speed, the thickness (basis weight) of the document, and the like in addition to the curl amount at the trailing edge of the document. Therefore, the movement amount L1 of the reading glass 12 may be controlled using these as parameters.

For example, the non-contact area C2 is approximately 2 mm when a document having no curling at the trailing edge of the document and having a basis weight of 80 g / m ² is conveyed at a speed of 177 mm / s, and non-contact area C2 is not conveyed when the document is conveyed at a speed of 329 mm / s. It has been experimentally found that the contact area C2 is about 4 mm. Therefore, when the conveyance speed is changed from 177 mm / s to 329 mm / s, the movement amount L1 may be set longer. Further, when a document having a basis weight of 128 g / m ² is conveyed at a speed of 177 mm / s, the non-contact area C2 becomes 0.5 mm or less. In this case, the movement amount L1 may be set short.

(Refer to Fig. 15 for another method of non-document contact)
In order to convey the document to be conveyed in a non-contact state with respect to the reading glass 12, various configurations other than providing the guide sheet 30 may be employed to form a step. For example, as shown in FIG. 15, the document D being conveyed is curved by a guide 29 provided on the upstream side in the document conveyance direction B of the reading glass 12 and a guide 27 installed on the downstream side. Are conveyed while maintaining this curved posture. The first embodiment and the second embodiment can be applied to such a configuration.

(Other examples)
The image reading apparatus and the image forming apparatus according to the present invention are not limited to the above-described embodiments, and can be variously modified within the scope of the gist.

1 is a perspective view showing an appearance of a copying machine. It is a schematic block diagram which shows an image reading apparatus. It is a principal part expanded sectional view of the said image reading apparatus. It is sectional drawing which shows the drive means of reading glass. FIG. 2 is a block diagram illustrating a control unit of a copying machine and an image reading apparatus. It is explanatory drawing which shows presence of a residual foreign material. It is explanatory drawing of the moving amount L1 of the reading glass in 1st Example. It is explanatory drawing which shows the reading glass movement timing from original front-end | tip detection in 1st Example. It is explanatory drawing which shows the reading glass movement timing from a document trailing end detection in 1st Example. It is a top view which shows the image defect | deletion area | region on a recording medium. It is a flowchart figure which shows the control procedure of 1st Example. It is explanatory drawing which shows the contact area resulting from the curl amount of the document rear end in 2nd Example. It is principal part sectional drawing which shows 2nd Example. It is a flowchart figure which shows the control procedure of 2nd Example. It is sectional drawing which shows schematic structure of the other system of a document non-contact.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Copy machine 10 ... Image reader 12 ... Reading glass (transparent member)
DESCRIPTION OF SYMBOLS 17 ... Drive motor 20 ... Automatic document feeder 27, 29 ... Document guide 30 ... Guide sheet (step formation member)
DESCRIPTION OF SYMBOLS 50 ... Reading optical system 61 ... Control part A ... Reading position B ... Original conveyance direction D ... Original document SE1 ... Original detection sensor SE2, SE3 ... Curl amount measurement sensor

Claims (8)

A document conveying means for sending out the documents one by one and passing the reading position;
Reading means for optically reading an image of a document conveyed at the reading position;
A transparent member disposed between the document conveyed at the reading position and the reading unit;
Than said reading position are disposed on the upstream side of the document feed direction, by conveying the document conveyed in a state with the transparent member and the gap does not contact the document conveyed the reading position on the transparent member orientation A step forming member to be held in ,
Drive means for reciprocating the transparent member along the document conveying direction;
After the leading edge of the document has passed the reading position, and control means for the trailing edge of the document is to start moving in the original conveying direction of the transparent member when in proximity to said reading position,
Equipped with a,
Foreign matter that has moved in the document transport direction due to the movement of the transparent member is removed from the reading position by the rear end of the document that is separated from the step forming member and contacts the transparent member as the document is transported.
An image reading apparatus. The image reading apparatus according to claim 1, wherein the step forming member is a sheet having a predetermined thickness arranged on the transparent member . The control means returns the transparent member moved until the trailing edge of the document passes through the reading position to the original position until the leading edge of the next document reaches the reading position; The image reading apparatus according to claim 1 , wherein: A document detection sensor disposed upstream of the reading position in the document conveyance direction;
The control means starts the movement of the transparent member based on the document trailing edge detection timing by the document detection sensor;
Image reading apparatus according to any one of claims 1 to 3, characterized in. The control means according to any one of claims 1 to 4, characterized in that to control the amount of movement of said transparent member to move selectively into a plurality of positioning the transparent member in the original conveying direction Image reader. With measuring means for measuring the curl amount of the document,
The control means determines a moving amount of the transparent member based on a curl amount measured by the measuring means;
The image reading apparatus according to claim 5 . The image reading apparatus according to claim 5 , wherein the control unit determines a moving amount of the transparent member based on a document conveyance speed. An image reading apparatus according to any one of claims 1 to 7 ,
An image forming unit that outputs an image read by the image reading device as a visible image on a recording medium in a state in which an image defect region that causes an image formed on an end of the read document to be lost is formed. ,
Wherein, between the rear end of the document corresponding to the image missing region is you pass the reading position, moving the transparent member in the original conveying direction,
An image forming apparatus.

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