JP2012005065A - Document reading apparatus, document reading method and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a document reading apparatus in which a white reference plate for shading correction of a reading sensor is prevented from getting dirty, a document is brought into close contact with a document platen and provided with a white reference unit for making a distance from the document platen to the white reference plate to be constant.SOLUTION: At both ends of a white reference plate, rollers are provided, and the rollers are supported by the white reference plate so as to be movable vertically. When there is no document and the white reference plate is read, the white reference plate is at the lowest position. When there is a document, the hight varies by the roller according to the thickness of the document. In order to prevent floating of the document at the position corresponding to an overlapping portion of a reading sensor, the roller used at the portion is slightly larger than that of the other positions so as to increase a load imposed on the overlapping portion of the document. Thus, variation in reading sensors with respect to reading data in the overlapping portion is able to be reduced.

Description

  The present invention relates to a document reading apparatus, a document reading method, and an image forming apparatus.

  In a conventional document reading apparatus, a line-shaped reading sensor is arranged in a direction orthogonal to the document transport direction, and the document transported is scanned while being scanned row by row.

  However, there is a problem that the reading sensor has a variation in sensitivity individually, and if it is used as it is, the read image data is affected by the variation, and the image cannot be accurately reproduced. In order to solve this problem, individual sensitivity variations of the reading sensor are corrected by shading correction.

  A white reference plate is used as a white reference when performing shading correction. There is an apparatus in which the white reference plate is disposed at a position facing the reading sensor. There is a gap between the white reference plate and the document table, and the document passes through the gap. In this type of apparatus, the original cannot be pressed against the original platen at the position of the reading sensor, so that if there is a wrinkle on the original, a gap is formed between the original and the original platen, and the reading accuracy is lowered. It was.

  Some use a white roller instead of a white reference plate. This is a configuration in which a white roller is arranged at a position facing the reading sensor, this white roller is used in place of the white reference plate, and the original is brought into contact with the original table by urging the original in the direction of the original table. . According to this, since the document is pressed against the document table at the reading position, the reading accuracy is improved. However, since the white roller is in contact with the document, it may be soiled or damaged. Therefore, there is a problem that the white color of the white roller changes and the white reference changes.

  In order to solve these problems, the prior art described in Japanese Patent Laid-Open No. 10-98580 discloses a technique in which a white reference plate supported so as to be movable up and down is provided at a position facing the reading sensor. In this prior art, there is further a first protrusion that makes the distance between the white reference plate and the document table constant, and the distance between the white reference plate and the document table is made constant. Further, a second protrusion lower than the first protrusion is provided to prevent the original from flapping. This second protrusion is located between the pair of transport rollers and is arranged so as not to block the reading unit. The original is fed by the second protrusion.

Japanese Patent Laid-Open No. 10-98580

  However, in the prior art, the protrusions move only up and down with respect to the document, and it is considered that the frictional resistance between the protrusions and the document is large. If the contact area is reduced in order to reduce the frictional resistance, the leading edge becomes sharp and the document is damaged. In addition, there may be a protrusion that fits in the ridge part of the document. At this time, the friction between the protrusion and the document increases, and the conveyance of the document temporarily stops or the document snakes along the ridge part. This may cause an abnormal conveyance.

  Further, the prior art has a structure in which the protruding portion presses the document after the document is read by the reading sensor. In this structure, since the document is not pressed against the reading glass at the reading position by the reading sensor, the document may float. When the document floats, there arises a problem that reading accuracy is lowered. In particular, when the distance between the conveyance rollers is long, for example, when the reading sensor units are arranged in a plurality of rows in the document conveyance direction, the distance between the conveyance rollers becomes long, and the problem of the document floating becomes remarkable.

  There is also an image reading apparatus that uses a plurality of reading sensor units arranged in a staggered manner in a direction perpendicular to the transport direction. In this type of image reading apparatus, reading sensor units are partially overlapped in the transport direction, and data read by adjacent reading sensor units are connected to form one image data. Therefore, it is necessary to read the joint portion accurately. There is a problem that when the document floats at the joint portion, reading is not performed accurately, image data at the joint portion is different, and a streak pattern appears.

  In response to such a problem, the present invention reads the original without smearing the white reference plate at the time of reading the original, and further prevents the original from floating at the joint position of the read image data. Provided are an image reading apparatus, an image reading method, and an image forming apparatus capable of acquiring high-quality read data in which no difference occurs in image data.

  The document reading apparatus according to the present invention includes a transport roller that transports a document, a pinch roller that is disposed facing the transport roller and biased in the direction of the transport roller, and transports by the transport roller and the pinch roller. A document table that supports the document, a plurality of line sensors that are arranged to face the document table and are arranged in a staggered manner so that a part of the reading range overlaps, and each of the line sensors A white reference plate disposed oppositely, a support portion that supports the white reference plate, a lid portion that supports the pinch roller and to which the support portion is fixed, and supports the transport roller and the lid portion. In the document reading apparatus that is supported so as to be opened and closed, and further includes the document table and a table part that accommodates the line sensor, the white reference plate is disposed before and after the document conveyance direction, A plurality of rollers for urging a document in the direction of the document table, the first roller disposed at a position corresponding to the overlapping portion of the reading range, and a position corresponding to a portion not overlapping the reading data; The distance from the outer periphery of the first roller to the document table is shorter than the distance from the outer periphery of the second roller to the document table.

  An image forming apparatus according to the present invention records an image based on image data acquired by the document reading device on the recording medium transported by the transport unit, and a transport unit that transports the recording medium. Recording means.

  The document reading method of the present invention includes a transport roller that transports a document, a pinch roller that is disposed facing the transport roller and biased in the direction of the transport roller, and transports by the transport roller and the pinch roller. A document table that supports the document, a plurality of line sensors that are arranged to face the document table and are arranged in a staggered manner so that a part of the reading range overlaps, and each of the line sensors A white reference plate disposed oppositely, a support portion that supports the white reference plate, a lid portion that supports the pinch roller and to which the support portion is fixed, and supports the transport roller and the lid portion. In the document reading apparatus that is supported so as to be opened and closed, and further includes the document table and a table part that accommodates the line sensor, the white reference plate is disposed before and after the document conveyance direction, A plurality of rollers for urging a document in the direction of the document table, the first roller disposed at a position corresponding to the overlapping portion of the reading range, and a position corresponding to a portion not overlapping the reading data; A document reading device, wherein a distance from the outer periphery of the first roller to the document table is shorter than a distance from the outer periphery of the second roller to the document table. The document reading apparatus further includes a document position detection sensor for detecting the position of the document, a storage unit, and a shading correction unit, and the document table is provided with another white reference different from the white reference plate. A step of reading the other white reference plate as a first white reference value with the plate placed thereon and storing it in the storage means; and a second white reference value for the white reference plate without the other white reference plate Read as said memory hand And a step of detecting the presence or absence of the document on the document table based on an output of the document position detection sensor, and a third white reference plate when the document table is absent on the document table. A value obtained by adding a difference between the first white reference value and the second white reference value to the third white reference value as a white reference value, and the original based on the shading correction result. And obtaining image data obtained by reading the original document conveyed to a table.

  According to the present invention, the white reference plate is not soiled, and the document can be prevented from being lifted at the reading position where the read data is connected. It is possible to acquire high-quality read data in which there is no difference in image data at the joint portion.

FIG. 1 is a perspective view of the white reference plate unit of the present invention from the direction of the white reference plate. FIG. 2 is a side view of the white reference plate unit of the present invention. FIG. 3 is a schematic diagram of the entire image forming apparatus of the present invention. FIG. 4 is a schematic diagram of the image reading unit of the present invention. FIG. 5 is a cross-sectional view of the lid portion of the image reading unit of the present invention. FIG. 6 is a bottom view of the lid of the image reading unit of the present invention. FIG. 7 is a block diagram of the image forming apparatus of the present invention. FIG. 8 is a flowchart showing an example of the shading correction procedure of the present invention. FIG. 9A is a schematic view of the first pressing roller. FIG. 9B is a schematic view of the second restraining roller.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view of the white reference plate unit of the present invention from the direction of the white reference plate. The white reference plate unit 1 includes a white reference plate 2, a pressing roller support portion 3, a first pressing roller 4, a second pressing roller 5, a light shielding portion 6, and a roller shaft 7.

  The white reference plate unit 1 constitutes a roller support section 3 by bending both ends of a metal plate. A white reference plate 2 is formed on the flat portion of the metal plate. The roller support portion 3 supports the roller shaft 7. A plurality of first press rollers 4 and second press rollers 5 are rotatably attached to the roller shaft 7 on both sides of the white reference plate 2. In order to block light leaking from the gap, the tip of the metal plate is convex and bent to form the light shielding portion 6. The light shielding portion 6 is configured to enter between the first presser roller 4 and the second presser roller 5. The light shielding portion 6 also has an effect of preventing the end of the conveyed document from being caught by the first pressing roller 4 and the second pressing roller 5.

  The portion of the white reference plate 2 serves as a white reference for shading correction. The white reference plate 2 has a white surface and may be configured by applying paint or a white reference film may be attached.

  The first presser roller 4 and the second presser roller 5 may be provided with a slight gap so that they can move in the axial direction of the roller shaft 7. Further, the first presser roller 4 and the second presser roller 5 preferably rotate independently of each other. However, even if the first presser roller 4 and the second presser roller 5 are configured as one roller, the mechanism is configured to rotate in conjunction with each other as if they were one roller. May be provided. The first presser roller 4 is formed in a size larger than the second presser roller 5.

  FIG. 2 is a side view of the white reference plate unit of the present invention. A first shaft hole 9 and a second shaft hole 10 are formed in the presser roller support portion 3. The roller shaft 7 is passed through the first shaft hole 9 and the second shaft hole 10, and the roller shaft 7 is stopped by the system stopping member 8. The first shaft hole 9 is a circular through hole. The second shaft hole 10 is a substantially rectangular through hole. A square corner is formed in an arc shape. The moving direction of the roller shaft 7 passed through the first shaft hole 9 is different from the moving direction of the roller shaft 7 passed through the second shaft hole 10. This is because even if the first shaft hole 9 and the second shaft hole 10 cannot be formed in exactly the same shape at predetermined positions due to manufacturing variations, the first shaft hole 9 and the second shaft hole 10 are deformed. By doing so, the degree of freedom of movement of the shafts can be improved even if problems due to the formation of such holes occur. Therefore, the white reference plate 2 can be moved up and down accurately.

  Further, the first presser roller 4 is formed in a size larger than the second presser roller 5. The contour of the outer periphery of the second presser roller 4 is hidden by the contour of the outer periphery of the first presser roller 4.

  FIG. 3 is a schematic diagram of the entire image forming apparatus of the present invention. The image forming apparatus 20 includes an image reading unit 11 and a recording unit 12. The image reading unit 11 is divided into a base portion 14 and a lid portion 13, and the lid portion 13 is supported on the base portion 14 so as to be openable and closable. The platform 14 is provided with a conveyance roller 16 for conveying the document 17. The conveyance roller 16 is disposed in the vicinity of inserting the document 17 and in the vicinity of discharging. A pinch roller 15 that is paired with the conveying roller 16 is supported by the lid portion 13. The conveying roller 16 is driven to rotate, and the pinch roller 15 is urged so as to be rotatable in accordance with the conveying roller 16. Therefore, when the transport roller 16 rotates, the pinch roller 15 is rotated along with it. The document 17 is conveyed while being sandwiched between the conveying roller 16 and the pinch roller 15.

  The table portion 14 includes a document table 18 that supports the document 17. The surface of the document table 18 is arranged at the same height as the top of the outer periphery of the conveying roller 16. The document table 18 is a transparent and flat glass plate. The document 17 passes over the document table 18. A line sensor 19 is arranged so as to be in contact with the surface of the document table 18 that is not the conveyance surface of the document 17. Two line sensors 19 are arranged in a zigzag pattern in the document insertion direction and two in the document ejection direction. Each line sensor 19 is arranged so that a part of the reading portion overlaps when reading the document 17. The white reference plate unit 1 is disposed on the lid portion 13. The white reference plate unit 1 is disposed at a position facing each line sensor 19.

  The recording unit 12 stores a recording medium 22 to be used. The recording medium 22 is a roll of paper or plastic film. The recording medium 22 is conveyed by a conveying means having a recording medium conveying roller 23. An image is recorded on the recording medium 22 conveyed by the recording means 21. The image to be recorded can also be recorded based on the image data read by the image reading unit 11. It is also possible to receive image data from an external computer and record the image on a recording medium based on the image data.

  FIG. 4 is a schematic diagram of the image reading unit of the present invention. The image reading unit 11 includes a base portion 14 and a lid portion 13. A motor 26 is provided on the base 14 to rotate the belt 25 that is wound around the pulley 24. There is a shaft at the center of the pulley 24, and the conveying roller 16 is attached to the shaft. When the pulley 24 rotates, the shaft rotates, and the transport roller 16 further rotates. A conveyance roller 16 is provided in a direction perpendicular to the conveyance direction of the document 17 so as to sandwich the document table 18. These conveyance rollers 16 rotate in conjunction with each other, and convey the document 17 with the pinch roller 15 provided in the lid portion 13 therebetween. A plurality of conveying rollers 16 are arranged in parallel along the longitudinal direction of the document table 18 so that documents of various widths can be conveyed.

  A plurality of first document position detection sensors 28 are arranged along the longitudinal direction of the document table 18, and a plurality of second document position detection sensors 27 are arranged so as to sandwich the document table 18. The second document position detection sensor 27 detects whether or not the conveyed document 17 has reached the front of the document table 18 and whether or not it has reached the downstream of the document table 18. The plurality of first document position detection sensors 28 detect the document width. The second document position detection sensor 27 is disposed substantially at the center of the document table 18. The position of the document 17 relative to the document table 18 is detected by arranging the second document position detection sensor 27 on the insertion side and the discharge side of the document 17 and inserting the center of the document 17 and the center of the document table 18 together. be able to. It is designed to handle documents of various widths.

  The periphery of the conveying roller 16 is set lower than the document table 18 so that the vertex of the outer periphery of the conveying roller 16 is exposed. This is because the transport roller 16 can sufficiently hold the document 17.

  The line sensors 19 are arranged in a staggered pattern on the lower surface of the document table 18. The white reference plate unit 1 is arranged on the lid 13 so that each white reference plate 2 faces each line sensor 19. Since the line sensors 19 are arranged in a plurality of rows, here two rows, the distance between the transport rollers 16 becomes longer. In order for the document 17 to be conveyed without floating from the document table 18, and particularly for conveying the document 17 without floating on the line sensor 19, the first presser roller 4 and the second presser roller in front and rear in the conveyance direction of the line sensor 19. 5 is holding down. The first presser roller 4 and the second presser roller 5 are pressed by the weight of the white reference plate 2 or the like. Moreover, you may bias with a spring etc. Preferably, the first pressing roller 4 and the second pressing roller 5 are arranged along the entire length of the line sensor 19 in the longitudinal direction. By doing so, the document 17 is prevented from being lifted.

  Since the line sensors 19 are arranged in a zigzag pattern, there is an overlapping range 35 in which the line sensors 19 overlap and read. The overlapping range 35 is a range between alternate long and short dash lines. The conveyance roller 16 is disposed on an extension line of the overlapping range 35.

  Two line sensors 19 are arranged on the upstream side in the conveyance direction of the document 17 and three on the downstream side. When the document 17 is inserted, the first presser roller 4 and the second presser roller 5 come into contact with each other, but this is to reduce the load when the first contact is made at that time.

  FIG. 5 is a cross-sectional view of the lid portion of the image reading unit of the present invention. The lid portion 13 has a frame 29 inside, the first arm portion 30 is connected to the frame 29, and the document discharge side pinch roller 15 is supported at the tip thereof. The second arm portion 31 is connected to the frame 29, and the pinch roller 15 on the document insertion side is supported at the tip thereof. A white reference plate unit support portion 32 is connected to the frame 29. The white reference plate unit support portion 32 supports the roller shaft 7 of the white reference plate unit 1. Since the roller shaft 7 is passed through the first shaft hole 9 and the second shaft hole 10, the white reference plate 2, the light shielding portion 6, and the pressing roller support portion 3 are formed in the first shaft hole 9 and the second shaft hole 10. It is supported so as to be movable within the range of. A document pressing plate 33 is disposed at the bottom of the lid portion 13. The document pressing plate 33 is provided with a through hole for allowing the pinch roller 15 and the white reference plate unit 1 to protrude from the document pressing plate 33. The pinch roller 15 and the conveying roller 16 can be opposed to and in contact with each other. The first presser roller 4, the second presser roller 5 and the white reference plate 2 of the white reference plate unit 1 are opposed to the document table 18. The document pressing plate 33 is provided with a light shielding piece 34 that is paired with the light shielding portion 6 of the white reference plate unit 1. The light shielding piece 34 is also disposed between the first pressing roller 4 and the second pressing roller 5 in the same manner as the light shielding portion 6. Similarly to the light-shielding portion 6, the light-shielding piece 34 prevents the document 17 conveyed by bending from being caught.

  The first shaft hole 9 and the second shaft hole 10 are arranged so that the second pressing roller 5 and the white reference plate 2 do not contact the document table 18 even if the outer periphery of the first pressing roller 4 contacts the document table 18. The size and position of the opening and the sizes of the first presser roller 4 and the second presser roller 5 are determined.

  FIG. 6 is a bottom view of the lid of the image reading unit of the present invention. A document pressing plate 33 is disposed at the bottom of the lid portion 13. The document pressing plate 33 has an opening from which five white reference plate units 1 protrude. The white reference plate units 1 are arranged in a staggered manner facing the line sensor 19. In the white reference plate unit 1, the first pressing roller 4 is disposed within the overlapping range 35, and the second pressing roller 5 is disposed outside the overlapping range 35. A pinch roller 15 corresponding to the conveying roller 16 is disposed within the overlapping range 35. The white reference plate unit 1 arranged on the outermost side is not in the overlapping range 35, but the first pressing roller 4 is arranged in a portion corresponding to the end of the line sensor 19.

  Within the overlapping range 35, the document 17 contacts the first presser roller 4 four times. Therefore, the conveyance load becomes larger than other parts. For this reason, the document 17 is likely to be distorted. If the line sensor 19 reads the document 17 in a state where the document 17 has a conveyance abnormality, the two line sensors 19 produce different image data. Misalignment occurs when image data are connected. Therefore, the conveying roller 16 and the pinch roller 15 are arranged on the extended line of the overlapping range 35 so that the document 17 is firmly pressed before and after the line sensor 19. Further, the document 17 is pressed against the document table 18 by the first pressing roller 4. Since the first presser roller 4 is larger than the second presser roller 5, the weight of the white reference plate 2 or the like is mainly applied to the first presser roller 4. Therefore, the document 17 is mainly pressed by the first pressing roller 4 as long as the document 17 is not greatly bent. And it is the structure which the 2nd press roller 5 presses the part bent largely convexly. Further, the first presser roller 4 is arranged so that the document 17 does not float at the position corresponding to the end of the outermost line sensor 19.

  The first pressing roller 4 is configured with a smaller number than the second pressing roller 5. This is because more weight is applied to the first presser roller 4. Since a larger load can be applied to the hard document in the overlapping range 35, more bending of the document 17 at the connection portion of the image data can be prevented.

  FIG. 7 is a block diagram of the image forming apparatus of the present invention. The ROM 37 stores data such as a program for controlling the overall operation of the image forming apparatus 20 and initial setting values. The control circuit 36 is a control circuit that performs processing such as comparison, calculation, and control in accordance with a program stored in the ROM 37, and includes, for example, a CPU. The RAM 38 is a memory used in a work area that is used for temporary storage of various data, calculation of the control circuit 36, and the like. The conveyance unit 39 includes the motor 26, the belt 25, the pulley 24, the conveyance roller 16, and the pinch roller 15, and is a unit that conveys the document 17. The transport means 39 operates under the control of the control circuit 36. The line sensor 19 is a sensor that reads the document 17 under the control of the control circuit 36. The first document position detection sensor 28 is a sensor that is controlled by the control circuit 36 and detects the width of the conveyed document 17. The second document position detection sensor 27 is a sensor that is controlled by the control circuit 36 and detects whether or not the document 17 is on the document table 18.

  The recording medium conveying unit 40 conveys the recording medium 22 stored in the image forming apparatus 20 to the recording unit 21, and after recording an image with the recording unit 21, the recording medium 22 is discharged out of the image forming apparatus 20. The recording medium conveyance roller 23 is driven to convey the recording medium 22. The recording medium transport means 40 operates under the control of the control circuit 36. The recording unit 21 records an image on the recording medium 22. The recording means 21 operates under the control of the control circuit 36.

  Next, the shading correction operation of the present invention will be described. FIG. 8 is a flowchart showing an example of the shading correction procedure of the present invention.

  Prior to this processing, a white reference plate similar to the white reference plate 2 is placed on the document table 18, read as the first white reference value, and the value is stored in the RAM 38. Further, the white reference plate 2 is read and stored in the RAM 38 as the second white reference value. Preferably, the difference between the first white reference value and the second white reference value is calculated, and the value is stored in the RAM 38 in advance.

  First, the process is started (step S1). Whether the lid 13 is open or closed with respect to the base 14 is determined based on the output of an open / close sensor (not shown). If the lid 13 is open, no processing is performed. If the lid 13 is closed, the process proceeds to step S3 (step S2).

  Next, it is determined whether or not the document 17 is on the document table 18. Based on the output of the first document position detection sensor 28, the width of the document 17 is calculated. The range of the original 17 is determined based on whether or not the output of the first original position detection sensor 28 is present, and a calculation for estimating the width of the original 17 is performed. If there is an output in which the second document position detection sensor 27 on both outer sides of the center of the document table 18 detects the document 17, it is determined that the document 17 is on the document table 18. If there is no output in either one, it is determined that the document 17 is not on the document table 18. If the document 17 is not on the document table 18, the process proceeds to step S4. If so, the process proceeds to step S9 (step S3).

In step S9, the conveyance roller 16 is driven to discharge the document 17.
In step S4, the white reference plate 2 is read and stored in the RAM 38 as a third white reference value.
Next, the black reference value is read and stored in the RAM 38 (step S5). The black reference value is a value obtained by reading the line sensor 19 with the line sensor 19 turned off.

  Next, as a first correction process, a fourth white reference value is calculated by adding a difference between the first white reference value and the second white reference value to the third white reference value. At this time, the first white reference value and the second white reference value or the difference value are stored in advance in the RAM 38 (step S6).

Next, shading correction processing of the line sensor 19 is performed using the fourth white reference value (step S7).
When the shading correction process is finished using the fourth white reference value, the process is finished (step S8). After the shading correction, the document 17 is conveyed and image data is read.

  Next, the shape of the holding roller will be described. FIG. 9A is a schematic view of the first pressing roller. FIG. 9B is a schematic view of the second restraining roller. The first presser roller 4 includes a flat portion 41 at a part of the outer periphery. In order to increase the contact area with the original 17, the first presser roller 4 is partially flattened at the outer periphery. The first presser roller 4 presses a portion of the document 17 corresponding to the joint portion of the read image data against the document table 3. It is preferable that the document 17 and the first pressing roller 4 are not in point contact but have a large contact area. On the other hand, since the second presser roller 5 only suppresses the floating of the document 17, it is desirable to make point contact as much as possible in order to reduce the load of conveyance by contact as much as possible. Therefore, the outer peripheral tip 42 of the second presser roller 5 is curved and formed in a semicircular shape.

  The present invention can be applied to a reading device that conveys a document and reads the document, and an image forming apparatus including the reading device.

DESCRIPTION OF SYMBOLS 1 White reference board unit 2 White reference board 3 Pressing roller support part 4 1st pressing roller 5 2nd pressing roller 6 Light-shielding part 7 Roller shaft 8 System stop member 9 1st shaft hole 10 2nd shaft hole 11 Reading part 12 Recording part 13 Lid 14 Base 15 Pinch roller 16 Transport roller 17 Document 18 Document base 19 Line sensor 20 Image forming device 21 Recording means 22 Recording medium 23 Recording medium transport roller 24 Pulley 25 Belt 26 Motor 27 Second document position detection sensor 28 1 document position detection sensor 29 frame 30 first arm portion 31 second arm portion 32 white reference plate unit support portion 33 document pressing plate 34 light shielding piece 35 overlapping range

Claims (7)

A transport roller for transporting the document;
A pinch roller disposed opposite to the transport roller and biased in the direction of the transport roller;
A document table for supporting the document conveyed by the conveyance roller and the pinch roller;
A plurality of line sensors arranged in a staggered manner so as to be opposed to the document table and to partially overlap the reading range;
A white reference plate disposed opposite to each of the line sensors;
A support for supporting the white reference plate;
A lid that supports the pinch roller and to which the support is fixed;
In the document reading apparatus, which supports the transport roller and supports the lid portion so as to be openable and closable, and further includes the document table and a table portion that houses the line sensor.
A plurality of rollers that are arranged before and after the white reference plate in the document conveyance direction and urge the document in the document table direction, and are arranged at positions corresponding to overlapping portions of the reading range. A roller and a second roller disposed at a position corresponding to a portion that does not overlap the read data, and the distance from the outer periphery of the first roller to the document table is from the outer periphery of the second roller to the document. An original reading apparatus characterized by being shorter than a distance to a table.   The first roller is composed of a plurality of rollers, the second roller is composed of a plurality of rollers, and the number of rollers of the first roller is smaller than the number of rollers of the second roller. The document reading apparatus described.   The document reading apparatus according to claim 2, wherein the conveyance roller and the pinch roller are arranged on an extension line of an overlapping portion of the reading range.   The number of the line sensors is an odd number, arranged in two rows in the transport direction, and the number of the line sensors in the upstream row in the transport direction is smaller than that in the downstream row in the transport direction. The document reading apparatus according to claim 1.   The document reading apparatus according to claim 2, wherein each of the rollers rotates independently. The document reading device according to any one of claims 1 to 5,
Conveying means for conveying the recording medium;
Recording means for recording an image on the recording medium conveyed by the conveying means based on the image data acquired by the document reading device;
An image forming apparatus comprising: A transport roller for transporting a document; a pinch roller disposed opposite to the transport roller and biased in the direction of the transport roller; and a document for supporting the document transported by the transport roller and the pinch roller And a plurality of line sensors arranged in a staggered manner so as to be opposed to the document table and partially overlap the reading range, and a white reference plate arranged to face each of the line sensors A support part that supports the white reference plate, a lid part that supports the pinch roller and to which the support part is fixed, and supports the transport roller and supports the lid part so that it can be opened and closed. In a document reading apparatus having a document table and a table unit that accommodates the line sensor, the white reference plate is arranged before and after the document conveyance direction, and the document is attached in the document table direction. A first roller disposed at a position corresponding to an overlapping portion of the reading range, and a second roller disposed at a position corresponding to a portion not corresponding to the overlapping portion of the read data. An original reading method of an original reading apparatus, wherein a distance from an outer periphery of the first roller to the original table is shorter than a distance from an outer periphery of the second roller to the original table,
The document reading apparatus further includes a document position detection sensor that detects the position of the document, a storage unit, and a shading correction unit.
Reading another white reference plate as a first white reference value and storing it in the storage means in a state where another white reference plate different from the white reference plate is placed on the document table;
Reading the white reference plate as a second white reference value and storing it in the storage means in the absence of the other white reference plate;
Detecting the presence or absence of the document on the document table based on the output of the document position detection sensor;
When the document is not on the document table, the white reference plate is read as a third white reference value, and a value obtained by adding a difference between the first white reference value and the second white reference value to the third white reference value is obtained. A process of correcting shading as a white reference value;
A document reading method comprising: obtaining image data obtained by reading the document conveyed to the document table based on the shading correction result.

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