JP2008104165A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader capable of attaining stable reading and coinciding the sub-scanning magnification of original image of the front surface of the original with that of the back surface of original image. <P>SOLUTION: The image reader gives a difference in carrying speed between an upstream side carrying roller and a downstream-side carrying roller to an original reading means. The reading sub-scanning magnifications of a first reading part and a second reading part are adjusted by changing the main-scanning reading times of the first reading part (CCD line sensor 126) and the second reading part (CIS line sensor 128) independently. This control is conducted by a CPU 309. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image reading apparatus having a double-sided simultaneous reading mechanism that simultaneously reads both sides of a document to be conveyed, such as a digital copying machine, a facsimile machine, and a scanner. In particular, the present invention relates to an image reading apparatus having a reading magnification adjustment function.

  2. Description of the Related Art Conventionally, in an image reading apparatus used for a copying machine or the like, a document is conveyed one page at a time on an original platen glass by an automatic document feeder, and is exposed by an exposure device fixed to the conveyance path to be an image of the document. Is known that performs so-called “flow-reading”. Further, there is known a technique in which two image reading means are provided to improve productivity and “double-sided simultaneous reading” is performed to read the front and back of a document by one conveyance (for example, see Patent Document 1).

  In such an image reading apparatus capable of “scanning reading”, an error occurs in the reading magnification of the document when the document conveyance speed changes. For this reason, when the original passes through the original reading unit of the image reading apparatus, it is necessary to always remove the original at an equal speed.

  For example, in a conventional general image reading apparatus, a flow reading glass included in a reading optical system is arranged along a path surface of an original, and a conveyance path is provided so that the original passes through the surface of the flow reading glass. Composed.

  The transport path is provided with a plurality of rollers for feeding the document. That is, a roller for stably transporting the original to the flow reading glass is provided on the entrance side (upstream side of conveyance) to the flow reading glass, and the original after reading is provided on the discharge side (downstream side of conveyance). A discharge roller is provided for discharging this by friction.

  Here, the influence of the difference in the conveyance speed of the lead roller 108 and the lead driven roller 109 and the speed of the lead discharge roller 111, the lead discharge driven roller 112, and the discharge roller 113 in the image reading apparatus of FIG.

  If the respective speeds are set to be the same and the conveyance speed difference is not set, an error may occur in the document reading magnification when a speed difference occurs due to finishing accuracy or wear of each roller. In addition, sagging may occur in the original, and the original may float at the original reading position, that is, the position of the flow reading glass 116 or the flow reading glass 130, which may affect the resolution (so-called out-of-focus).

  For example, Patent Document 2 proposes the following technique for this problem.

A difference in conveying speed is given between the conveying roller arranged on the upstream side in the document conveying direction and the conveying roller arranged on the downstream side with respect to the document reading unit. Specifically, the document transport speed of the document transport roller disposed on the downstream side is set higher than the document transport speed of the document transport roller disposed on the upstream side. By adopting such a mechanism, the original is always pulled to the conveyance side in the original reading unit, and the slack of the original is eliminated and stable and accurate reading is realized.
JP 2004-187144 A Japanese Patent Laid-Open No. 11-289420

  However, the technique disclosed in Patent Document 2 has the following problems in the case of an image reading apparatus having two image reading units as in the above-described “double-sided simultaneous reading”.

  The timing at which the original enters the rollers and the timing at which the trailing edge of the original passes through the rollers is the flow reading glass 116 (see FIG. 1 described later) for reading the front surface (first surface) and the flow for reading the back surface (second surface). It differs depending on the reading glass 130 (see FIG. 1 described later).

  Therefore, if the document conveyance speed of the document conveyance roller arranged on the downstream side is increased with respect to the document conveyance speed of the document conveyance roller arranged on the upstream side, the document image is sub-scanned. There arises a problem that the magnification is different between the front side and the back side of the document.

  Specifically, if the document transport speed of the document transport roller disposed on the downstream side is increased as described above, the sub-scan magnification of the read image on the back side becomes smaller than the sub-scan magnification of the front surface. Problems arise.

  An object of the present invention is to provide an image reading apparatus capable of stable reading and capable of matching the sub-scan magnification of a document image between the front surface and the back surface of the document.

  In order to achieve the above object, an image reading apparatus according to claim 1 is arranged upstream of the first reading means for reading a document and the first reading means with respect to the document transport direction, at a first transport speed. A first transport unit that transports the document; and a second transport that is disposed downstream of the first reading unit in the document transport direction and transports the document at a second transport speed that is faster than the first transport speed. And the main scanning time of the first reading unit after the original is held by the second conveying unit is shorter than that before the original is held by the second conveying unit. And a control means for controlling.

  According to the present invention, the first transport unit is disposed upstream of the first reading unit that reads the document in the document transport direction, transports the document at the first transport speed, and the second transport unit performs the document transport. The document is transported at a second transport speed that is arranged downstream of the first transport means in the transport direction and is faster than the first transport speed. The control means controls the scanning time of one main scanning of the first reading means after the original is held by the second conveying means to be shorter than that before the original is held by the second conveying means. To do.

  With such a configuration, stable reading is possible, and the sub-scanning magnification of the document image can be matched between the front surface and the back surface of the document.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram schematically showing a configuration of an image reading apparatus according to a first embodiment of the present invention.

  In FIG. 1, the image reading apparatus includes an automatic document feeder 100 and an image reading apparatus main body 115.

  FIG. 2 is a flowchart showing a procedure of double-sided document reading processing executed by the image reading apparatus of FIG.

  The configuration of the image reading apparatus in FIG. 1 will be described together with the operation of the flowchart in FIG.

  In the automatic document feeder 100, the document tray 101 stacks documents 102. A paper feed roller 103 is provided above the document tray 101. The paper feed roller 103 is connected to the same drive source as the separation conveyance roller 104, and rotates with the rotation to feed the original (step S201).

  The paper feed roller 103 is normally retracted to the upper position, which is the home position, so that the document setting operation is not hindered. When the paper feeding operation is started, the paper feeding roller 103 descends and comes into contact with the upper surface of the document 102. Since the paper feed roller 103 is pivotally supported by an arm (not shown), it moves up and down as the arm swings.

  The separation conveyance driven roller 105 is disposed on the side opposite to the separation conveyance roller 104 and is pressed toward the separation conveyance roller 104 side. The separation conveyance driven roller 105 is formed of a rubber material or the like that has slightly less friction than the separation conveyance roller 104, and cooperates with the separation conveyance roller 104 to copy one original 102 fed by the paper supply roller 103. Feed the paper one by one.

  The registration roller 106 and the registration driven roller 107 align the front end of the original 102 fed by the separation unit, and abut the front end of the original 102 separated toward the nip portion of the stationary registration roller pair. A loop (deflection) is generated in the document 102 to correct the skew of the original 102. The read roller 108 and the read driven roller 109 flow the original 102 toward the reading glass 116. A platen roller 110 is disposed on the opposite side of the flow reading glass 116.

  Image information on the surface (first surface) of the original 102 passing on the flow reading glass 116 (first reading unit) is read by the CCD line sensor 126 (step S202). When the reading of the surface image of the document 102 by the CCD line sensor 126 is completed, the lead discharge roller 111 and the lead discharge driven roller 112 convey the document to the CIS line sensor 128 side.

  The jump stand 117 scoops up the original 102 from the flow reading glass 116. A platen roller 127 is disposed on the opposite side of the CIS line sensor 128. Image information on the back surface (second surface) of the document 102 passing on the flow reading glass 130 (second reading unit) is read by the CIS line sensor 128 (step S203), and the back surface of the document 102 by the CIS line sensor 128 is read. When the image reading is completed, the paper discharge roller 113 discharges the original 102 to the paper discharge tray 114 (step S204).

  The image reading apparatus main body 115 includes a lamp 119 that irradiates light on the surface of the original to be read, and mirrors 120, 121, and 122 that guide reflected light from the original 102 to the lens 125 and the CCD line sensor 126. The lamp 119 and the mirror 120 are attached to the first mirror base 123. The mirrors 121 and 122 are attached to the second mirror base 124.

  The mirror tables 123 and 124 are coupled to a drive motor (not shown) by wires (not shown), and move parallel to the document table glass 118 by the rotation of the drive motor. The reflected light from the original 102 is guided to the lens 125 through the mirrors 120, 121, and 122, and is imaged on the light receiving portion of the CCD line sensor 126 by the lens 125.

  The CCD line sensor 126 photoelectrically converts the formed reflected light with a light receiving element, and outputs an electrical signal corresponding to the amount of incident light. Similarly, the CIS line sensor 128 photoelectrically converts the reflected light from the original 102 by the light receiving element, and outputs an electric signal corresponding to the amount of incident light.

  In the image reading apparatus having the above configuration, the original 102 is placed on the original platen glass 118, and the original is read while the first mirror base 123 and the second mirror base 124 are moved in the sub-scanning direction (arrow direction in the figure). A document fixed reading mode is provided.

  In addition, there is a flow reading mode in which the original 102 is conveyed by the automatic document feeder 100 while the first mirror table 123 and the second mirror table 124 are stopped and the document is read at the position of the flow reading glasses 116 and 130. . The original 102 can be read in these two modes.

  FIG. 3 is a functional block diagram of the image reading apparatus according to the present embodiment.

  In FIG. 3, an image reading apparatus includes a pulse generator circuit 305 that generates a pulse for driving a CCD line sensor 126 that reads the surface of a document, and an A / D conversion circuit 301 that converts an analog signal from the CCD line sensor 126 into a digital signal. Is provided.

  The image reading apparatus also includes a shading correction circuit 302 that performs shading correction on the image data converted into a digital value by the A / D conversion circuit 301. In addition, an image data output line 307 for outputting image data from the CCD line sensor 126 subjected to shading correction to an external device is provided.

  The image reading apparatus also includes a pulse generator circuit 306 that generates a pulse for driving the CIS line sensor 128 that reads the back side of the document, and an A / D conversion circuit 303 that converts an analog signal from the CIS line sensor 128 into a digital signal. .

  The image reading apparatus also includes a shading correction circuit 304 that performs shading correction on the image data digitally converted by the A / D conversion circuit 303. Further, an image data output line 308 for outputting image data from the CIS line sensor 128 subjected to shading correction to an external device is provided. The image reading apparatus also includes a CPU 309 that controls the whole.

  The pulse generator circuits 305 and 306 can change driving conditions such as the scanning time of one main scanning of the CCD line sensor 126 and the CIS line sensor 128 by setting from the CPU 309.

  FIG. 4 is a flowchart showing a procedure of document conveyance processing at the time of double-sided document reading executed by the image reading apparatus of FIG.

  In FIG. 4, the document 102 stacked on the document tray 101 is transported between the pair of separation and transport rollers from the uppermost document by the paper feed roller 103 (step S <b> 401). When a plurality of originals are conveyed while being overlapped, the separation conveyance roller 104 and the separation conveyance driven roller 105 separate and convey the original into one sheet (step S402).

  The originals separated into one sheet are transported to the first reading unit (surface reading unit) after the leading ends of the originals are aligned by a pair of registration rollers on the downstream side, passing through the pair of read rollers. (Step S403). Subsequently, the document 102 passes through the pair of lead discharge rollers and is guided to the second reading unit (back surface reading unit) (step S404), further conveyed to the discharge roller 113, and discharged to the discharge tray 114 (step S405). ), The process is terminated.

  FIG. 5 is a flowchart showing a data processing procedure at the time of double-sided document reading executed by the image reading apparatus of FIG.

  This process is executed by the CPU 309 in FIG.

  In FIG. 5, first, document feeding is started (step S501). When the document reaches the first reading unit, transfer of image data of the CCD line sensor 126 to the image data output line 307 is started (step S502). .

  When the original reaches the second reading unit, output of the image data from the CIS line sensor 128 to the image data output line 308 is started (step S503). When it is detected that the image data has been transferred from the CIS line sensor 128 to the image data output line 308 (YES in step S504), if there is a next original (YES in step S505), the process proceeds to the next original reading operation. If there is no next original (NO in step S504), the double-sided simultaneous reading operation of the original is terminated.

  Next, the document conveying speed and the driving speed of the CCD line sensor 126 will be described.

  Considering the driving speed of the image reading apparatus that reads 60 A4 originals per minute, only one original must be read per second. The A4 size sub-scanning length is 210 mm when the original is set so that the short side direction of the original is parallel to the conveyance direction. The CCD line sensor 126 must be driven at a speed at which 250 mm can be read in the sub-scanning direction per second.

Considering the case of reading an original with a resolution of 600 dpi, under the above conditions, the scanning time of one main scanning line (time spent reading one main scanning line; scanning time of one main scanning) is obtained by the following equation. .
1 main scanning line scanning time = 1 sec / (250 mm / (25.4 mm / 600))
It can be seen that the CCD line sensor 126 must be driven in one main scanning line scanning time = 169 μsec. The same applies to the CIS line sensor 128 that reads the back surface.

  Further, when the CCD line sensor 126 is driven under the above conditions, the conveyance speed of each roller for document conveyance is 100% when the document is conveyed at a conveyance speed of 250 mm per second. Therefore, it is necessary to drive each roller at a speed of 250 mm / sec.

  FIG. 6 is a diagram illustrating a first example of a transport image of a document transported by the image reading apparatus of FIG.

  Here, even when the lead roller 108, the lead discharge roller 111, and the discharge roller 113 have a speed difference due to finishing accuracy, wear, or the like, the following is performed so that the original does not sag. That is, the conveyance speed of the paper discharge roller 113 is increased by 1% with respect to the lead roller 108 and the lead discharge roller 111, and is pulled. That is, the speed difference between the transport speed (first transport speed) of the lead roller 108 and the lead discharge roller 111 and the transport speed (second transport speed) of the paper discharge roller 113 is the lead discharge roller 111 and the paper discharge roller 113. The speed difference is such that no sagging occurs in the document. Here, the document clamping force (holding force) of the discharge roller 113 is set to be larger than the document clamping force (holding force) of the lead roller 108 and the lead discharge roller 111. Further, while the document is being pulled by the paper discharge roller 113, one of the driving and driven rollers is separated from the other so that the frictional force or clamping force of the lead roller 108 and the lead discharge roller 111 is reduced. You may comprise so that it may move to a direction.

  In this case, when the original 102 enters the paper discharge roller 113, the conveyance speed of the original 102 is increased by 1%. Therefore, depending on the positional relationship between the paper discharge roller 113, the first reading unit, and the second reading unit. Therefore, the reading sub-scanning magnifications of the front and back documents are different.

  Here, the distance from the first reading unit to the paper discharge roller 113 is 100 mm, and the distance from the second reading unit to the paper discharge roller is 30 mm. Considering the case of reading an A4 document with this configuration, the first reading unit reads a document at a normal speed up to 100 mm, and reads the remaining 110 mm at a speed of 1%.

  In the second reading unit, the original 102 is read at a normal speed up to 30 mm, and the remaining 180 mm is read at a speed of 1%. FIGS. 7A and 7B show an example of an A4 document. FIG. 7A shows the front side of the document passing through the first reading unit, and FIG. 7B shows the back side of the document passing through the second reading unit.

  If the original is read in this state, the image data of the front side reading unit (first reading unit) is read in the following size.

Surface sub-scan reading size = 100 mm (normal speed area) +110 mm / 1.01 (speed up area)
Surface sub-scan reading size ≒ 208.9mm
The image data of the back side reading unit (second reading unit) is read in the following size.

Back side sub-scan reading size = 30 mm (normal speed area) +180 mm / 1.01 (speed up area)
Back side sub-scan reading size ≒ 208.2mm
Even when an A4 original having a sub-scan size of 210 mm is read, the size is actually reduced.

Here, in order to adjust the sub-scanning reading size of the surface to 210 mm, the driving speed of the lead roller 108 and the lead discharge roller 111 that determines the conveyance speed until the document reaches the discharge roller 113 is the normal conveyance speed. 250 mm / sec is the surface adjustment conveyance speed = 250 mm / sec × 208.9 mm / 210 mm
Surface adjustment transport speed ≒ 248.69mm / sec
By adjusting (reducing) so that the sub-scanning reading size on the front surface can be adjusted to 210 mm, the sub-scanning reading size on the back surface can be adjusted as follows even at this speed.

Back side sub-scanning reading size after surface adjustment = 210 mm / 208.9 mm × 208.2 mm
Back side sub-scanning reading size after surface adjustment = 209.29 mm
Therefore, in the present embodiment, by adjusting the normal conveyance speed, first, the sub-scanning magnification of the read image on the front surface is adjusted, and for the back-side read image, one main scanning line scanning time of the CIS line sensor 128 is adjusted. The control for adjusting the sub scanning magnification is performed.

For example, after adjusting the normal conveying speed, the remaining adjustment necessary magnification is 209.29 mm / 210 mm = 99.66%.
Therefore, the scanning time of one main scanning line of the CIS line sensor 128 may be shortened by this amount (the reading driving speed of the CIS line sensor 128 is increased by this amount).

Scanning time of one main scanning after back surface adjustment = 169 μsec × 0.9966
Scanning time of one main scan after back surface adjustment = 168.4254 μsec
Therefore, the CPU 309 sets to the pulse generator circuit 306 such that one main scanning line scanning time of the CIS line sensor 128 is 168.4254 μsec.

  The magnification adjustment for the front and back surfaces is an example of A4 size, and it is necessary to change the set value according to each document size. This is because the ratio of the area to be read at the normal speed and the area to be read at an increased speed changes.

  Therefore, the CPU 309 performs an operation of setting the conveyance speed according to the read original size set by the user and setting the back surface 1 main scanning line time in the pulse generator circuit 306.

  By controlling in this way, even when a configuration is employed in which the conveyance speed of the conveyance downstream roller is increased and the tension drive is adopted, it is possible to perform both-sided simultaneous reading with accurate sub-scanning magnification adjustment on both the front and back surfaces.

  In the second embodiment, an image reading operation when the reading magnification is adjusted by another control with the same configuration as that of the first embodiment will be described.

  In the first embodiment, by adjusting the normal conveyance speed, first, the sub-scan magnification of the read image on the front surface is adjusted, and the scan time of one main scan of the CIS line sensor 128 is adjusted for the back-side read image. The control for adjusting the sub-scanning magnification is performed.

  In this configuration, the sub-scanning magnification of the entire A4 document can be adjusted, but when viewed partially, the document transport speed is increased by 1% from the time when the document 102 enters the paper discharge roller 113. Therefore, the magnification is partially different in the read document image. For example, when a document in which lines are arranged at equal intervals as shown in FIG. 8 is read, the line width enters the discharge roller 113. (Part B in the figure), the part read before that (part A in the figure) is read with a reduction of 1%.

  Therefore, in this embodiment, the time after the document 102 is fed is counted so that the CPU 309 can detect the timing when the document enters the paper discharge roller 113. The scanning time of one main scanning line of the CCD line sensor 126 and the CIS line sensor 128 is shortened by 1% with respect to the pulse generator circuits 305 and 306 at the timing when the original 102 enters the paper discharge roller 113 (CCD line sensor 126). , The reading drive speed of the CIS line sensor 128 is increased by 1%). Specifically, the following formula is set.

Scanning time of 1 main scanning = 169 μsec / 1.01
1 main scan scan time = 167.327 μsec
Therefore, until the original 102 enters the paper discharge roller 113, the pulse generator circuits 305 and 306 are set to perform reading with a scanning time of one main scanning = 169 μsec. Then, at the timing when the document 102 enters the paper discharge roller 113, a setting is made so that reading is performed at a scanning time of 1 main scanning = 167.327 μsec.

By controlling in this way, even when a configuration is adopted in which the conveyance speed of the conveyance downstream roller is increased and pulled, both sides can be read simultaneously with accurate sub-scanning magnification adjustment on both the front and back surfaces. In addition, it is possible to adjust the sub-scanning magnification with a simple configuration that does not require the setting value to be changed depending on the document size.

1 is a schematic diagram of an image reading apparatus according to a first embodiment of the present invention. 3 is a flowchart of double-sided document reading processing executed by the image reading apparatus of FIG. 1 is a functional block diagram of an image reading apparatus according to an embodiment of the present invention. 6 is a flowchart of document conveyance processing at the time of double-sided document reading executed by the image reading device. 6 is a flowchart of data processing at the time of double-sided document reading executed by the image reading apparatus. FIG. 3 is a diagram illustrating a first example of a transport image of a document transported by the image reading apparatus of FIG. 1. FIG. 7A shows a second example of a transport image of a document transported by the image reading apparatus of FIG. 1, FIG. 7A shows the surface of the document passing through the first reading unit, and FIG. FIG. 6 is a diagram illustrating a back surface of a document passing through a section. FIG. 10 is a diagram illustrating a third example of a transport image of a document transported by the image reading apparatus of FIG. 1.

Explanation of symbols

126 CCD line image sensor (first reading means)
128 CIS line image sensor (second reading means)
301, 303 A / D conversion circuits 302, 304 Shading correction circuits 305, 306 Pulse generator circuits 307, 308 Image data output line 309 CPU (control means)

Claims (6)

First reading means for reading a document;
A first conveying unit disposed upstream of the first reading unit with respect to a document conveying direction and conveying a document at a first conveying speed;
A second transport unit disposed downstream of the first reading unit in the document transport direction and transporting the document at a second transport speed faster than the first transport speed;
The scanning time of one main scanning of the first reading unit after the document is held by the second transport unit is controlled to be shorter than that before the document is held by the second transport unit. An image reading apparatus comprising: a control unit.   2. The image reading apparatus according to claim 1, wherein the document holding force of the second conveying unit is larger than the document holding force of the first conveying unit.   The speed difference between the second transport speed and the first transport speed is a speed difference that does not cause a sag in the document between the first transport means and the second transport means. The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus. The first reading means reads a first surface of a document,
The image reading apparatus further includes a second reading unit that is provided upstream of the second conveying unit and reads a second surface of the document.
The control means makes the scanning time of one main scanning of the second reading means after the original is held by the second conveying means shorter than before the original is held by the second conveying means. The image reading apparatus according to claim 1, wherein the image reading apparatus is controlled to be   The first reading unit and the second reading unit respectively read the first surface and the second surface of the document while the first transport unit or the second transport unit transports the document. The image reading apparatus according to claim 4.   6. The image reading apparatus according to claim 1, wherein the control unit changes a scanning time of one main scanning while the first reading unit is reading a document. 6. .

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