JP2021022908A - Image reading apparatus - Google Patents

Abstract

To provide an image reading apparatus which reduces streaks in a read image when reading a conveyed document.SOLUTION: An image reading apparatus in the present invention includes a document platen unit on which a document is mounted, a document conveyance unit that can be opened/closed to the document platen unit by a rotation shaft and conveys the document mounted on a tray, a reading sensor that is provided on the document conveyance unit so as to extend in a crossing direction crossing the rotation shaft and reads the document conveyed in the conveyance direction by the document conveyance unit at a first position, a white reference member that is provided on the document platen unit and faces the reading sensor in a state where the document conveyance unit is closed, and an adjustment mechanism for adjusting a position of the reading sensor in the conveyance direction, in which the adjustment mechanism adjusts the position of the reading sensor, then the reading sensor acquires the data of the white reference member and reads the document at a second position different from the first position.SELECTED DRAWING: Figure 4

Description

The present invention relates to an image reader that reads an image of a conveyed document.

Patent Document 1 discloses an image reading device including a reading sensor that reads an image of a document conveyed by a conveying roller and a moving mechanism that moves the reading sensor to a position facing the white reference member. In this image reading device, the reading sensor reads the document conveyed by the conveying roller at the same reading position. On the other hand, when performing shading correction for normalization of the reading sensor, the reading sensor is moved to a position facing the white reference member by a moving mechanism, and data of the white reference member is acquired.

Japanese Unexamined Patent Publication No. 2005-129896

In the configuration of Patent Document 1, the reading position for reading the original is the same position. As a result, if there is dust or dirt on the glass or the like, streaks will appear in the image in the transport direction. The present invention is to provide an image reading device that reduces streaks in a scanned image when scanning a conveyed document.

The image reading device of the present invention can be opened and closed by a rotation axis with respect to a document stand unit on which a document is placed, a document transfer unit for transporting a document placed on a tray, and a document transfer unit. A reading sensor that extends in the crossing direction that intersects the axis and reads the document conveyed in the transfer direction by the document transfer unit at the first position, and a document stand unit that is provided and the document transfer unit is closed. An image reading device including a white reference member facing the reading sensor in a state and an adjusting mechanism for adjusting the position of the reading sensor in the transport direction. After adjusting the position of the reading sensor with the adjusting mechanism, the reading sensor is first. It is characterized in that the data of the white reference member is acquired and the original is read at a second position different from the position of.

According to the present invention, it is possible to provide an image scanning device that reduces streaks in the scanned image when scanning a conveyed document.

It is a perspective view of the front side of an image reader. It is a perspective view of the rear side of an image reader. It is a figure which shows the state which the document transport unit is open. It is sectional drawing which shows the internal structure of the document transport unit. It is a perspective view of the platen unit. It is a schematic diagram for comparing the size of a white reference member. It is sectional drawing which shows the arrangement of a reading sensor. It is a figure which shows the structure of a reading unit. It is a perspective view which shows the state which the reading unit is installed in the frame. It is a figure which shows the state which the reading unit is in a different position with respect to a white reference member. It is a figure which shows the flowchart which determines the reading timing of a reading sensor.

(Image reader)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments do not limit the present invention. Further, the relative positions and shapes of the components described in the embodiments are merely examples, and the scope of the present invention is not limited to them.

The image reading device of this embodiment will be described. The image reading device includes a device for reading an image of a document such as a scanner device, a facsimile machine, a copying machine, and a digital multifunction device. FIG. 1 is a perspective view of the front side of the image reading device, FIG. 2 is a perspective view of the rear side of the image reading device, and FIG. 3 is a view showing a state in which the document transport unit 701 is open. Further, FIG. 4 is a cross-sectional view showing the internal configuration of the document transport unit 701.

The image reading device includes a document transporting unit 701 that reads an image with a scanning sensor while transporting the document S, and a document table unit that the scanning sensor moves to read the placed document. The document transport unit 701 can be opened and closed on the front side where the operation panel 901 is located by means of rotating shafts (801 and 802) provided on the rear side of the document base unit 301. The document transport unit 701 includes a document tray 202 on which a plurality of documents can be placed, various rollers for feeding and transporting the documents, a reading sensor 304 for reading the image of the document S, and a paper output tray for loading the ejected documents. It is equipped with 211. The platen unit 301 is provided with a document glass 303 on which the document is placed, a reading sensor 207 for reading the document, and a moving mechanism for moving the reading sensor 207.

The manuscript S placed on the manuscript tray 202 is sequentially fed to the manuscript transport path from the manuscript S on the uppermost surface by the separation roller 203. The document transport path has a shape in which a document is U-turned between the paper feed tray 202 and the paper output tray 211. The document transport path is provided with a separation roller 203, a first transport roller 205, a second transport roller 208, and a paper discharge roller 209 from the upstream side to the downstream side in order to feed, transport, and eject the original. .. These rollers can be rotated by a motor M (not shown). The transport distance of the document S can be obtained by counting the number of steps of the motor M. Further, the document tray 202 is provided with a document presence / absence sensor 213 for detecting the presence / absence of the document 101, and the document transport path is provided with a document edge sensor 214 for detecting the front end and the rear end of the document 201. The transport direction for transporting the original is the direction from the first transport roller 205 to the second transport roller 208.

The reading sensor 207 is provided on the platen unit 301 so as to extend in the intersecting direction intersecting the rotation axis (801, 802). The reading sensor 207 is a line sensor composed of a plurality of elements, and reads an image of the surface of a document in the main scanning direction, which is the width direction of the sheet. When reading the image of the conveyed document, the reading sensor 207 reads the image at a predetermined position facing the reading glass 313 in a state of being irradiated with light from the light source. When reading a document placed on the document glass 303, the scanning sensor 207 reads the document while moving the lower side of the document glass 303 in the sub-scanning direction intersecting the main scanning direction. On the other hand, the document reading sensor 314 is provided in the document transport unit 701 so as to extend in the intersecting direction intersecting the rotation axis (801, 802). The reading sensor 314 is a line sensor composed of a plurality of elements, and reads an image of the back surface of the document at a predetermined position in the main scanning direction, which is the width direction of the sheet. When reading the image of the original, light is emitted from the light source.

The image reading device has a control unit that performs various controls based on instructions from the user or an external device. Therefore, based on the command from the control unit, various operations such as transporting the document and reading the document are performed. It also has a storage unit that stores programs that perform various operations and setting information. The instruction from the user can be input by the operation unit 901. Further, the input from the external device can be performed via the interface controller. It should be noted that the facsimile machine, the copier, the digital multifunction device, and the like are further equipped with necessary devices such as a recording unit for recording an image on a sheet.

(Reading the original)
Here, the reading of the document conveyed by the document transfer unit 701 will be described in detail. The document is read with the document transport unit 701 closed. The closed state is detected by an open / close sensor (not shown). When the document fed from the document tray 202 passes through the first transport roller 205, the tip of the document S is detected by the document edge sensor 214. The document S whose tip is detected is conveyed in a predetermined number of steps A and reaches above the reading sensor 207. On the reading sensor 207, the document S is pressed against the glass 313 by an elastic member (not shown) of the transport guide member 215. Therefore, the distance between the reading sensor 207 and the document becomes constant. The surface image of the document S that has reached the reading sensor 207 is sequentially read in accordance with the transportation. The document S is conveyed from the reading sensor 207 along the reading sensor support portion 501 in a predetermined number of steps B and reaches the reading sensor 314. After that, the images on the back surface are sequentially read according to the transportation. When the rear end of the document S is detected by the document edge sensor 214, the document S is conveyed in a predetermined number of steps C. After that, the reading by the reading sensor 207 is finished. Further, it is conveyed in a predetermined number of steps D and the reading by the reading sensor 314 is completed. After that, the document S is ejected to the output tray 211 by the second transport roller 208 and the output roller 209.

By the way, the reading sensor (207, 314) needs a shading correction for correcting the variation in the amount of light or the sensitivity before reading the image of the original. The shading correction is performed by irradiating the white reference member (19, 20) with light from a light source and acquiring the data of the white reference member (19, 20) with the reading sensor (207, 314). Each pixel can be normalized by the white reference data which is the data of the white reference member.

FIG. 5 is a perspective view of the platen unit 301 provided with the white reference member 20. FIG. 6 is a schematic view for comparing the lengths of the white reference members 20. FIG. 7 is a cross-sectional view showing the arrangement of the reading sensor (207, 314).

When the reading sensor 314 of the document transport unit 201 acquires the white reference data, the white reference member 20 provided on the white reference member support portion 501 facing the white reference member support portion 501 via the reading glass 302 fixed by the glass fixing member 606 is used. read. The white reference member 20 is white in a region longer than the effective pixels in the width direction of the sheet. A black triangular black marking portion 20B having an edge inclined with respect to the main scanning direction is provided outside the reading range of the maximum sheet width in the effective pixel. The inclination is 45 degrees with respect to the main scanning direction so that the main scanning direction and the sub scanning direction change 1: 1. When the reading sensor 314 acquires the data of the white reference member, the reading position with respect to the transport direction can be calculated from the position of the edge. The angle may be other than 45 degrees.

On the other hand, the reading sensor 207 of the platen unit 301 moves to the position of the white reference member 19 arranged adjacent to the document placement area of the document glass 303 in the sub-scanning direction when acquiring the white reference data. At that position, the white reference member 19 is read through the original glass 303. The white reference member 19 is a white member whose surface is longer than the reading range in the main scanning direction. After acquiring the data of the white reference member, the reading sensor 207 moves to a predetermined position facing the reading glass 313 in order to read the conveyed document, and can read the image of the document.

(Adjustment mechanism)
Here, the adjustment mechanism of the reading unit will be described with reference to FIGS. 8 to 10. The reading unit has a configuration including a reading sensor 314 and a sensor holder 602. FIG. 8A is a perspective view of the reading unit, and FIG. 8B is a cross-sectional view of the reading unit. FIG. 9 is a perspective view showing a state in which the reading unit is installed on the frame 604. FIG. 10 is a cross-sectional view showing a state in which the reading unit is located at a different position with respect to the transport direction.

The reading sensor 314 is positioned in the width direction of the sheet and the transport direction of the sheet by the mounting portions 314a, 314b, and 314c corresponding to the positioning portions 602a, 602b, and 602c provided in the sensor holder 602, respectively. The reading sensor 314 is urged from the vertical direction to the reading glass 302 by an urging member (not shown). Therefore, the reading sensor 314 can move integrally with the sensor holder 602 with respect to the reading glass 302.

The reading glass 302 is fixed to the glass fixing member 606. The glass fixing member 606 is engaged with the frame 604 by inserting the shafts 606a provided at both ends in the width direction of the sheet into the frame fitting holes 604a. The shafts 606a provided at both ends of the glass fixing member 606 are inserted into the frame fitting holes 604a of the frame 604. Therefore, the reading glass 302 can move in the direction perpendicular to the white reference member 20 when the document transport unit 201 is closed. At this time, the reading sensor 314 urged by the reading glass 302 also moves in the vertical direction at the same time.

The sensor holder 602 is provided with a positioning guide portion 602e that positions the frame 604 in the vicinity of the central portion in the width direction of the sheet. The positioning guide portion 602e is inserted into the frame fitting portion 604e. Further, the protrusion 602d provided at one end of the sensor holder 602 is fitted to a side fitting portion (not shown) provided on the frame 604. The adjusting mechanism is composed of an adjusting screw 601 provided on the frame 604 and a fastening portion 602f provided on the sensor holder 602. The fastening portion 602f is provided with a screw hole so that the fastening portion 602f can be fastened to the adjusting screw 601. The adjusting screw 601 is rotatably connected to the adjusting fixing member 605 fixed to the frame 604 with a screw. As a result, the sensor holder 602 can be moved in the transport direction with respect to the white reference member 20 by turning the adjusting screw 601. The adjusting screw 601 is arranged on the lower side of the document tray 202. The user can turn the adjusting screw 601 through the opening 202a provided in the document tray 202.

FIG. 10 is a diagram showing a state before and after the movement when the reading unit 314 is moved in the transport direction by the adjusting screw 601. The reading sensor 314 supported by the sensor holder 602 reads an image at a first position on the downstream side in the transport direction with respect to the white reference member 20 (FIG. 10A). The position for reading the image can be moved to the second position on the upstream side by the adjusting screw 601 (FIG. 10 (b)). The moving range of the reading position is determined by the length of the guide portion 602e and the frame fitting portion 604e in the transport direction. Here, the moving range is, for example, 4 mm.

(Determining reading timing)
FIG. 11 shows a flowchart for determining the reading timing of the reading sensor. In this flowchart, it is determined whether or not a streak or the like is generated in the image. Next, the reading sensor 314 is moved to check whether the streaks in the image have been reduced. After that, the reading timing is determined.

In the S1 step, the user starts an operation of determining the reading timing by operating the operation panel 901.

In the step S2, the data of the white reference member 20 is acquired by the reading sensor 314. The document edge sensor 214 confirms in advance that the document S is not in the document transport path and the open / close sensor confirms in advance that the document transport unit 201 is closed.

In the S3 step, the control unit analyzes the data of the white reference member. It is desirable that the data of the white reference member 20 has a predetermined value for each pixel of the reading sensor 314. The value of the data when there is dust becomes smaller in the pixels corresponding to the width of the dust. The criterion for judging that it is small is that it is smaller than the threshold value. Further, the data in the black marking portion continuously becomes a value close to zero in the pixels outside the edge position. As a result, the position of the black marking portion on the line sensor can be specified. In the case of a reading sensor having a resolution of 600 dpi (dots per inch), the resolution is 0.042 mm per pixel.

In the step S4, the control unit determines the presence or absence of dust. If it is determined that there is dust, the process proceeds to step S5. If it is determined that there is no dust, the process proceeds to step S6.

In the step S5, the control unit causes the operation panel 901 to display a display prompting the user to move the reading sensor 314. The user who sees the display turns the adjusting screw 601 to change the position of the reading sensor 314 from the first position to the second position. After that, the user inputs that the position change is completed by the confirmation button on the operation panel 901. When input, the process returns to the S2 process, and the reading sensor 314 acquires the data of the white reference member.

If it is determined in the step S6 that there is no dust, the image reading timing is determined. As shown in FIG. 10, it is assumed that the reading position has moved from the first position to the second position. The reading timing is performed based on the first position calculated from the current edge position of the black marking portion and the second position calculated from the changed edge position of the black marking portion. That is, the current number of steps is corrected from the distance between the second position and the first position. Further, the timing of reading the image by the reading sensor 314 is determined from the number of steps after correction and the feeding speed of the document. The determined timing is stored in the storage unit. If the transport speed changes, this timing will also change. Therefore, a plurality of timings may be stored in the storage unit according to the transport speed. If the first position and the second position are the same, the reading timing is not changed. Further, the number of steps may be determined directly from the second position.

In the step S7, the adjustment mode is terminated. At the second position, the data of the white reference member and the image of the original are read until the adjustment is performed again by the adjusting screw 601.

As described above, the reading position of the reading sensor can be changed by the adjusting mechanism. As a result, it is possible to reduce the occurrence of streaks in the scanned image when scanning the conveyed document.

20 White reference member 202 Paper feed document tray 301 Document stand unit 314 Reading sensor 601 Adjustment screw 701 Document transfer unit

Claims (6)

A platen unit on which documents are placed and a platen unit
A document transport unit that can be opened and closed with respect to the platen unit by a rotating shaft to transport documents placed on a tray, and a document transfer unit.
A reading sensor provided in the document transport unit extending in an intersecting direction intersecting the rotation axis, and reading a document transported in the transport direction by the document transport unit at a first position.
A white reference member provided on the platen unit and facing the reading sensor with the document transport unit closed.
An image reading device including an adjustment mechanism for adjusting the position of the reading sensor in the transport direction.
After adjusting the position of the reading sensor by the adjusting mechanism, the reading sensor acquires data of the white reference member and reads a document at a second position different from the first position. Image reader. The image reading device according to claim 1, wherein the white reference member includes a marking portion having an edge inclined with respect to the transport direction in an outer region of a document to be read in the crossing direction. The image reading device according to claim 2, wherein the edge is detected by the reading sensor. The invention according to any one of claims 1 to 3, wherein the timing for reading the transported document is determined based on the distance between the first position and the second position in the transport direction. Image reader. The image reading device according to claim 4, wherein the timing differs depending on the transport speed of the original. Claims 1 to 5 are characterized in that the adjusting mechanism includes an adjusting screw rotatably provided on the frame and a fastening portion for fastening the adjusting screw provided on the sensor holder of the reading sensor. The image reading device according to any one of the above.

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