JP3933810B2 - Image reading apparatus and control method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image reading apparatus that reads an image of a document continuously conveyed at a constant speed with an image sensor by a slit exposure method, and a control method therefor.
[0002]
[Prior art]
There is an image reading apparatus that reads a document such as a bill or check continuously at high speed, processes the image, and records the image on a magneto-optical disk or the like. For such bills and checks, both front and back sides are read and recorded.
[0003]
As such an image reading apparatus, there is a conventional one that reads an image with a CCD line sensor by a slit exposure method. This reading device guides an image of a document being conveyed to a CCD line sensor through an imaging lens, and reads (scans) the image in a direction substantially orthogonal to the document conveyance direction.
[0004]
In this way, when both the front and back sides of the document are read by the line sensor, if the illumination light on the opposite side of the document is transmitted through the document, the images on the opposite side are overlapped and read. That is, show-through occurs. Therefore, the image reading positions on the front and back sides are shifted in the document feeding direction to prevent the images on the opposite side from being seen through.
[0005]
FIG. 12 is a diagram showing the arrangement of the front and back images of the document guided to the line sensor via the optical system. In FIG. 12, reference numerals LS (LS _A , LS _B ) are line sensors, which are arranged on a single straight line in the vertical direction on the paper surface. In FIG. 12, the image G of the document moves from right to left at a constant speed. I.e. appears substantially symmetrical with respect to the dead zone area A _R of the table image G _A and the line sensor LS and the back image G _B of one document, the distance x here Table image G _A against the back image G _B Only the phase is advanced to prevent show-through. When a document having a size of 216 mm × 93 mm is reduced and printed on a microfilm having a width of 16 mm, the phase difference x is about 6 mm in actual dimensions.
[0006]
In FIG. 12, A _A indicates an image reading range for the front image G _A by the line sensor LS _A. Likewise A _B shows an image reading range with respect to the back image G _B by the line sensor LS _B. These image reading ranges A _A and A _B are set for each original based on the detection position (start position S _T ) of the start detection sensor for obtaining the reference position for starting image reading from the position of the original. It is desirable that the original images G _A and G _B enter the image reading ranges A _A and A _B with an appropriate margin around them. The image on the left side in FIG. 12 shows a case where the document is conveyed to the correct position without being tilted. In this state, a margin y of 10 mm is provided before and after the length (93 mm) in the document conveyance direction. Accordingly, the dimension in the transport direction of the image reading ranges G _A and G _B is (93 + 10 + 10) = 113 mm.
[0007]
When a check having this size is read at a speed of 240 sheets / minute, if the image reading speed of the line sensor LS is 20 MHZ, the time required for main scanning is 256 μsec, and the resolution is 200 dpi, the document conveyance speed V is V = 1 ÷ (256 μsec) × (25.4 mm ÷ 200) × 60 = 29.77 m / min = 596.09 mm / sec. Accordingly, the document transport pitch p in this case is p = 29.77 m ÷ 240 sheets = 124 mm / sheet. Here, the distance between the leading edges or the centers of two continuous documents is referred to as a conveyance pitch p or a conveyance interval, and a gap formed between the two documents is referred to as a document gap.
[0008]
[Problems to be solved by the invention]
In actual bills or checks, stamps, etc. are affixed at the same position on many documents, stamps or signatures are attached at the same position, and there are creases and rubbing marks near the same position. . For this reason, a large number of bills / checks may be conveyed while being inclined in the same direction with respect to the conveying direction. The images G _A and G _B on the right side of FIG. 12 show the image of the document tilted in this way.
[0009]
In the tilted images G _A and G _B , some of the images G _A and G _B may be out of the image reading ranges A _A and A _B. In this case, the line sensor LS cannot read the portions protruding from the image reading ranges A _A and A _B and records an image with a part missing. Further, if the inclination angle of the document is excessive, the images of two documents that are continuous in the transport direction are close to each other in the transport direction or overlapped in an extreme case. In particular, when reading the front and back images G _A and G _B while shifting them in the transport direction to prevent show-through, the back (or front) image of the preceding document and the front (or back) image of the subsequent document Image reading phases tend to overlap. In this case, the image processing becomes extremely troublesome or the processing becomes impossible to separate the images of the two originals.
[0010]
Also, during the time between the image reading ranges A _A , A _{A and} between A _B , A _B adjacent in the transport direction, image processing and transfer are usually performed in the image processing apparatus. Image processing becomes impossible. Such a problem may occur when the gap between successive originals becomes too small even if the originals are not inclined. On the other hand, if the gap between the documents becomes excessive, the number of documents processed per time, that is, the reading processing speed is reduced.
[0011]
The first object of the present invention is to provide a method for controlling an image reading apparatus capable of correctly reading an image of a document even when the document is conveyed while being inclined. To do. It is a second object of the present invention to provide an image reading apparatus that is directly used for carrying out this method. Furthermore, the present invention provides an image processing apparatus that prevents inconveniences such as an image not being correctly read or a reduction in processing speed when the gap between the documents becomes too small or too large even if the document is not inclined. It is a third object to provide
[0012]
[Structure of the invention]
According to a first object of the present invention, in a control method of an image reading apparatus that reads an image of a document conveyed continuously at a constant speed by a slit exposure method, the inclination of the document entering the document conveyance path is detected, The image reading is characterized in that the gap between the originals is controlled to be widened by slowing down the feeding speed of the original supplied to the conveyance path next to the original in a continuous or multi-stage manner with respect to the increase in the inclination of the original. Achieved by a control method of the device.
[0013]
The second object is to be separated by a document feeding unit capable of accommodating a plurality of rectangular documents, a multifeed preventing unit for separating the documents one by one from the document feeding unit, and the multifeed preventing unit. In a slit exposure type image reading apparatus comprising: a transport unit that transports a document at a constant speed; an image sensor that reads an image of the document in the transport unit; and a document discharge unit that collects a document that has passed through the transport unit. a skew sensor for detecting the inclination of the originals from the double feed preventing portion entering the transport section, of the document in which the double feed preventing portion following this document with respect to increase in the tilt of the document detected by the skew sensor is sent It is achieved by an image reading apparatus comprising a paper feed control unit that controls to widen a document gap by slowing the paper feed speed continuously or in multiple stages .
[0014]
The skew sensor is formed by two document sensors provided on a straight line orthogonal to the document transport direction and separated by a certain distance. In this case, the inclination of the document can be obtained based on the difference between the document detection timings of the two document sensors. This skew sensor is preferably provided as close as possible to the entrance of the transport unit. This is to ensure a sufficiently long time to change the timing at which the next document enters the conveyance path.
[0015]
The double feed prevention unit includes a feed roller and a reverse roller, and can change the gap between documents by controlling the rotational speed of a paper feed motor that drives the feed roller. If the paper feed motor is a stepping motor (pulse motor), its speed can be changed quickly, which is desirable.
[0016]
The third object can be achieved by detecting the document gap size together with the document inclination based on the output of the skew sensor and controlling the paper feed speed so that the gap size falls within a predetermined range.
[0017]
Embodiment
1 is an external view of an embodiment of the present invention, FIG. 2 is a left side view, FIG. 3 is a plan view showing the arrangement of mirror groups, FIG. 4 is a front view showing the mirror groups and the optical system, and FIG. FIG. 6 is a perspective view showing the optical system, and FIG. 7 is an enlarged left side view of the vicinity of the image reading unit. The outline of the image reading apparatus to which the present invention is applied will be described with reference to these drawings.
[0018]
[Outline of the device]
In FIG. 1, reference numeral 10 denotes an image reading device, which is placed on a table box 14 that houses a printer 12. The image reading apparatus 10 is provided with a document feeding unit 16 on the front surface, and a document discharge unit 18 near the center of the upper surface. The upper surface is formed in a mountain shape in a side view, and a liquid crystal display panel 20 is attached to the slope on the front side. The image reading apparatus 10 is accommodated in a substantially box-shaped main body case 22, and an upper portion of the main body case 22 is a mountain-shaped lid 26 that can be opened and closed upward around a fulcrum 24 (FIG. 2). The display board 20 can be opened and closed upward about a fulcrum 28 (FIG. 2). Therefore, the internal inspection and maintenance can be performed by opening the display plate 20 or the lid 26 upward.
[0019]
Documents 30 are input from the document feeder 16 and are separated one by one by the double feed prevention unit 32 and enter the conveyance unit 40. The double feed prevention unit 32 includes a feed roller 36 driven by a belt by a paper feed motor 34 and a reverse roller 38 driven to rotate in the reverse direction. The document 30 enters between the feed roller 36 and the reverse roller 38 to prevent double feeding, and only one document 30 is separated. The paper feed motor 34 is formed of a stepping motor, and its speed is controlled by the inclination and gap of the original 30 as will be described later.
[0020]
Reference numeral 40 denotes a transport unit. The transport unit 40 is driven by a speed reduction shaft 44 driven by a transport motor 42, a drive roller group 51 driven by a belt 46 wound around the speed reduction shaft 44, and an intermediate shaft 48 driven by the belt 46. Holding the conveyor belt 50, a number of driven roller groups 52 arranged sequentially in the vertical direction facing the belt 46, and a group of driven rollers placed on the conveyor belt 50 from above and sequentially arranged in an approximately L shape. And a detachable presser roller support 54.
[0021]
The conveyance belt 50 and the presser roller support 54 convey the document 30 sent from the double feed prevention unit 32 substantially horizontally with the upper and lower sides sandwiched from above and below, and further upwardly drive roller group 51 and driven roller group 52. Let go between. The document 30 is sandwiched between the driving roller group 51 and the driven roller group 52, is sent substantially vertically upward, and is discharged to the document discharge unit 18. The presser roller support 54 can be inserted and removed from above by opening the document feeding unit 31 forward (front side) with the fulcrum 35 as the center, and removes the document 30 jammed in the conveyance path 40. be able to.
[0022]
In the middle of the vertical conveyance path of the drive roller group 51, a pair of photographing glasses 56 (56a, 56b) that sandwich the document 30 from both sides are disposed. A long horizontal light source lamp 58 (58a, 58b) is disposed outside the photographing glass 56 (see FIGS. 2 and 7). Here, the lamps 58a and 58b have different heights. That is, the lamp 58a that illuminates the front surface of the document 30 is lower than the lamp 58b that illuminates the back surface, and therefore the image reading position 60a on the front surface is lower than the image reading position 60b on the back surface (FIG. 7).
[0023]
Further, a black light shielding film 62 (62a, 62b) is formed on each glass 56a, 56b in order to prevent the transmitted light from the opposite lamps 58b, 58a from entering. The lamps 58a and 58b are surrounded by a light shielding plate 64 (64a and 64b) and a light shielding plate 66, and shield unnecessary light. Reference numeral 68 denotes a reflecting plate that reflects part of the light from the lamp 58 a that illuminates the front side and guides it to the surface of the document 30 before entering between the glasses 56.
[0024]
The illuminance of the surface of the original 30 illuminated with the light reflected by the reflector 68 is detected by the phototransistor 70, and the illuminance of the lamp 58 is automatically controlled by the output of the phototransistor 70. That is, automatic exposure control is performed. Here, the incident angle θ ₂ of the reflected light of the reflecting plate 68 with respect to the original 30 is made equal to the incident angle θ ₁ with respect to the image reading position 60 a of the lamp 58 a, thereby aligning the illumination conditions of the image reading position 60 a and the illuminance detection position. ing.
[0025]
The images on the front and back surfaces of the document 30 are read by the slit exposure method at the respective image reading positions 60a and 60b when passing between the glasses 56a and 56b. That is, the images on the front and back surfaces pass through the slits 72 (72a, 72b) shown in FIG. 7 and are further guided to one imaging lens 74 via the mirror group shown in FIG. Imaged. Here, the mirror group includes a pair of first mirrors 78 (78a, 78b), a second mirror 80 (80a, 80b), and a third mirror 82 (82a, 82b).
[0026]
The first mirror 78 is horizontally disposed so as to form about 45 ° with the document 30 interposed therebetween, and guides the images of the front and back surfaces of the document 30 to the left side surface of the main body case 22 through the glass 56. The second mirror 80 (80a, 80b) is disposed along the upper left corner of the main body case 22, and guides the reflected image of the first mirror 78 downward. The third mirror 82 is disposed along the lower left corner of the main body case 22, receives the reflected light from the second mirror 80, and guides it to the imaging lens 78.
[0027]
Here, the first mirror 78a and the second mirror 80a with respect to the front surface are set to the same height as the image reading position 60a. Similarly, the first mirror 78b and the second mirror 80b with respect to the rear surface are the same height as the image reading position 60b. Is set to That is, the height difference A between the image reading positions 60a and 60b is equal to the height difference between the second mirrors 80a and 80b, as shown in FIG. The distances B ₁ and C ₁ between the document 30 and the first mirrors 78a and 78b (for example, the distance between the centers of the images of the document 30) are the first mirrors at which the distance B ₁ between the lower position and the first mirror 78a is higher. It is larger than the interval C ₁ with 78b.
[0028]
The distances B and C are set so that the conjugate lengths of the imaging lens 74 with respect to the image reading positions 60a and 60b are the same. Here, the conjugate length has the same meaning as the optical path length, and the distance between the first mirror 78 and the second mirror 80 is set as B ₂ and C _{2 and} is set to A + (C ₁ + C ₂ ) = B ₁ + B ₂ . Is done. Here, the third mirrors 82a and 82b are formed by one common mirror. In the drawing, 84 is a magneto-optical disk drive device, which opens to the right side when viewed from the front of the main body case 22. Image data read by the CCD line sensor 76 is processed by an image processing device (not shown) and recorded on a magneto-optical disk (MO) loaded in the disk drive device 84.
[0029]
In FIG. 5, 86 is a trailing edge sensor that detects the trailing edge of the document 30 being conveyed, 88 is a skew sensor that detects the inclination of the document 30, 90 is a start detection sensor that determines a reference position for starting image reading, and 92 is paper discharge. It is a sensor.
[0030]
[Feeding speed control]
Next, a paper feed speed control mechanism will be described with reference to FIGS. FIG. 8 is a diagram for explaining the principle of inclination detection by the skew sensor, FIG. 9 is a layout diagram of the skew sensor, FIG. 10 is a diagram showing the function of the paper feed control unit, and FIG. 11 is a flowchart of the operation.
[0031]
As shown in FIG. 8, the skew sensor 88 includes two document sensors 88 </ b> A and 88 </ b> B positioned at a predetermined interval a on a straight line LN orthogonal to the conveyance direction F of the document 30. These document sensors 88A and 88B are provided at positions that are symmetrical in the width direction around the center in the running width of the document 30, and the distance a is constant (see FIG. 9). These sensors 88A and 88B can be formed of, for example, a light emitting diode and a light receiving sensor that face each other with the document 30 interposed therebetween. The outputs of these sensors 88A and 88B are both input to the 0R circuit 94 and the AND circuit 96.
[0032]
When the original document 30 that has just tilted enters the skew sensor 88, both sensors 88A and 88B detect the leading edge and the trailing edge of the original document 30 with a time difference. Accordingly, the outputs of the OR circuit 94 and the AND circuit 96 change as indicated by A and B in FIG. In this figure, outputs A and B are shown to be on (H level) when a document is detected. These outputs A, by multiplying the document transportation speed V to the time difference T _b of the rise of the B waveform, both document sensor 88A, a displacement amount b of the document leading edge between 88B, calculated as b = T _b · V be able to. Similarly, by multiplying the conveyance speed V by the time T _c from the rise of the output signal B to the rise of the output signal A, the distance c at which one document sensor 88B detects the document 30 is expressed as c = T _c. Calculated as V.
[0033]
Therefore, the inclination θ of the document 30 can be obtained by θ = tan ⁻¹ (b / a) as shown in FIG. Similarly, the width (length) d of the document 30 can be obtained by d = c · cos θ. The output signals A and B are input to a paper feed control unit 98 formed by a microcomputer as shown in FIG. The paper feed control unit 98 has functions of a tilt (θ) detection unit 100, a document gap (D) detection unit 102, and a document length (d) detection unit 104. The inclination θ is obtained by the inclination (θ) detection unit 100.
[0034]
Similarly, the document gap (D) is obtained by multiplying the time T _D from the fall of the waveform of the output signal A to the rise of the output signal B by the conveyance speed V. That is, D = T _D · V. The document length (d) is obtained by d = c · cos θ as described above. The sheet feeding control unit 98 controls the sheet feeding motor 34 and the like according to the operation shown in FIG. 11 using the obtained inclination (θ), document gap (D), and document length (d).
[0035]
First, when paper feeding is started (step 200), the paper feeding control unit 98 stands by until the skew sensor 88 starts to detect the original (step 202), and when the leading edge of the original 30 comes to the position of the skew sensor 88, the present invention. The inclination θ, the gap D, and the length d are detected by interrupting the control software (step 204). The paper feed control unit 98 determines an error if the inclination θ is 21 ° or more (step 206). At this time, the paper feed motor 34 is stopped so that a new document 30 does not enter the transport unit 40, and the transport motor 42 operates until the document 30 is discharged and then stops. This is because if the inclination θ is greater than 21 °, the document protrudes from the image reading ranges A _A and A _B , or the document gap D becomes too small to cope with the change of the sheet feeding speed.
[0036]
If the inclination θ is 6 ° or less, the processing is continued as it is at a normal sheet feeding speed (steps 208 and 210). This is because the images G _A and G _B will not leave the image reading ranges A _A and A _B if θ is 6 ° or less. If the inclination θ exceeds 6 ° (and less than 21 °) (steps 206 and 208), the paper feed motor 34 is decelerated (step 212). Here, it is desirable that the paper feed motor 34 has a good speed response such as a stepping motor. In this case, by reducing the time interval (frequency) of the drive pulse, the rotation speed of the paper feed motor 34, that is, the paper feed speed can be lowered in real time in response to the change of the drive pulse.
[0037]
The speed of the paper feed motor 34 may be decreased continuously with respect to the increase or decrease of the inclination θ, but may be decreased discontinuously in steps. As a result of lowering the sheet feeding speed in this manner, the timing at which the next original 30 enters the transport unit 40 is slightly delayed, and the gap D between the preceding inclined original and the next original increases. For this reason, both documents can be read correctly.
[0038]
If the document gap D is smaller than the minimum allowable value D _m (step 214), the paper feed motor 34 is decelerated (step 212). When the gap D is greater than the maximum value D _M is thereby accelerated (steps 216), the paper feed motor 34 (step 218). As a result, it is possible to prevent the document gap D from becoming too small for accurate image reading, and the gap D from becoming too large to reduce the processing speed. If the gap D is within the range between D _m and D _M (steps 214 and 216), the paper feed motor 34 operates at a normal speed (step 220).
[0039]
In this embodiment, the length d of the document is also monitored. When the length d is equal to or greater than the maximum standard value d _M (step 222), an error is determined as a nonstandard document. That is, in this case, both the paper feed motor 34 and the transport motor 42 are stopped urgently and the operator waits for the original to be discharged and restarted. The length d is continued operation smaller than the allowable value d _m in standard (step 224).
[0040]
(Step with the length d is greater than the allowable value d _m, i.e. in the case of d _m <d <d _M (step 224), only to stop the paper feed motor 34 to stop the image reading of a new document 226), the document being conveyed is sent to the paper discharge unit 18 and the conveyance motor 42 is also stopped (step 228). Then wait for the operator to check.
[0041]
In the embodiment described above, images on both the front and back sides of a document are read. However, the present invention can be applied to a case where only one side is read and includes such a case. One line sensor is shared for the front image and the back image of the document, but separate line sensors may be used for the front and back surfaces.
[0042]
【The invention's effect】
According to the first aspect of the present invention, the inclination of the document conveyed on the conveyance path at a constant speed is detected, and the feeding speed of the document entering the conveyance path is decreased continuously or in multiple stages with respect to the increase in the inclination. This enlarges the gap between the originals, so that the image can be read correctly even when the original is inclined and conveyed.
[0043]
According to the second aspect of the present invention, an image reading apparatus which is directly used for carrying out the first aspect of the present invention can be obtained. The skew sensor can be formed by two document sensors arranged on a straight line perpendicular to the document transport direction and spaced apart by a certain distance. By providing this skew sensor as close as possible to the entrance of the transport unit, it is possible to ensure a long time for controlling the paper feed speed of the document that subsequently enters the transport unit. Of course, the skew sensor may be provided in the vicinity of the outlet of the double feed prevention unit.
[0044]
The double feed prevention unit includes a feed roller and a reverse roller, and can control the paper feed speed by changing the speed of the paper feed motor that drives the feed roller. In this case, the sheet feeding motor is formed of a stepping motor, so that the sheet feeding speed can be quickly controlled with good responsiveness.
[0045]
The gap size of the document can also be detected by using the output of the skew sensor, and a function of controlling the paper feed speed so that the gap size falls within a predetermined range is added to the one that controls the paper feed speed by the inclination. (Claim 7). In this case, for example, even if the inclination is within an allowable range, if the gap size becomes too small, it is possible to read a proper image by lowering the paper feed speed and increasing the gap size. When this happens, the paper feed speed can be increased to prevent a reduction in the document processing speed.
[Brief description of the drawings]
FIG. 1 is an external view of an embodiment of the present invention. FIG. 2 is a left side view of the same. FIG. 3 is a plan view showing the arrangement of mirror groups. FIG. 6 is a perspective view showing an optical system. FIG. 7 is an enlarged left side view of the vicinity of the image reading unit. FIG. 8 is a diagram for explaining the principle of inclination detection by a skew sensor. [Fig. 10] Block diagram showing the functions of the paper feed speed control unit. [Fig. 11] Flow chart of the operation. [Fig. 12] Arrangement of the original image guided to the line sensor.
DESCRIPTION OF SYMBOLS 10 Image reading device 16 Original paper feeding part 18 Original paper discharge part 30 Original document 32 Double feed prevention part 34 Paper feed motor 40 Carrying part 42 Carrying motor 74 Imaging lens 76 Line sensor 88 Skew sensor 98 Paper feed control part 100 Tilt (θ ) Detection unit 102 Document gap (D) detection unit

Claims (7)

In a control method of an image reading apparatus that reads an image of a document conveyed continuously at a constant speed by a slit exposure method,
Detecting the tilt of the document entering the transport path of the document, the document gap by slowing with increasing inclination of the originals in a continuous or multistage sheet feeding speed of the document to be supplied to the conveyance path following this document And a method for controlling the image reading apparatus. A document feeder that can store a plurality of rectangular documents, a multifeed prevention unit that separates documents one by one from the document feeder, and a document that is separated by the multifeed prevention unit is conveyed at a constant speed. In a slit exposure type image reading apparatus comprising: a transport unit that performs scanning, an image sensor that reads an image of a document in the transport unit, and a document discharge unit that collects a document that has passed through the transport unit.
A skew sensor that detects the inclination of the original that enters the conveyance section from the multifeed prevention section, and a document that is sent by the multifeed prevention section next to the original in response to an increase in the inclination of the original detected by the skew sensor An image reading apparatus comprising: a paper feed control unit that controls the paper feed speed to be widened by slowing the paper feed speed continuously or in multiple stages .   The skew sensor is formed by two document detection sensors arranged on a straight line perpendicular to the document transport direction and spaced apart by a certain distance, and the paper feed control unit determines the difference in document detection timing between the two document detection sensors. 3. The image reading apparatus according to claim 2, wherein an inclination of the original is obtained based on the original.   4. The image reading apparatus according to claim 2, wherein the skew sensor is disposed near the entrance of the conveyance unit.   The double feed prevention unit includes a feed roller driven by a paper feed motor and a reverse roller rotated in a direction opposite to the feed roller, and the paper feed control unit controls a rotation speed of the paper feed motor. Item 5. The image reading apparatus according to any one of Items 2 to 4.   6. The image reading apparatus according to claim 5, wherein the paper feed motor is formed of a stepping motor.   The paper feed control unit detects the gap between the originals along with the inclination of the original based on the output of the skew sensor, controls the paper feed speed based on the inclination of the original, and the gap between the originals is within a predetermined range. The image reading apparatus according to claim 2, wherein the sheet feeding speed is controlled as described above.

Images