JP2000264499A - Image rearding device and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly read an image, even when a document is conveyed obliquely by executing the control for detecting the inclination of a document inserted into a document conveying passage, lowering paper feed speed for feeding the document to the conveying passage corresponding to the increase of the inclination, and expanding the clearance between the documents. SOLUTION: A paper feed control part keeps its standby state until a skew sensor 88 starts detection of a document, and a control soft is interrupted to detect the inclination, clearance and length when a front edge of the document 30 reaches a position of the skew sensor 88. The paper feed control part considers it as being an error when the inclination is larger than or equal to 21 deg.. Here, a paper feed motor 34 is stopped to prevent a new document 30 from entering the conveying part. When the inclination is 6 deg. or smaller, the document is fed at a normal paper feed speed to continue the processing. This can be made available because an image does not project from an image reacing range, when the inclination is 6 deg. or smaller. Furthermore, when the inclination is over 6 deg., the paper feed motor 34 is decelerated. For the paper feed motor 34, a stepping motor and the like superior in speed responsiveness is preferably used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus for reading an image of a document continuously conveyed at a constant speed by an image sensor by a slit exposure method and a control method thereof.

[0002]

2. Description of the Related Art There is an image reading apparatus which continuously reads a document such as a bill or a check at a high speed, processes the image, and records the image on a magneto-optical disk. With such bills and checks, both sides are read and recorded.

As such an image reading apparatus, there is an apparatus which reads an image with a CCD line sensor by a slit exposure method. The reading device guides an image of a document being conveyed to a CCD line sensor through an image forming lens, and reads (scans) the image in a direction substantially orthogonal to the direction in which the document is conveyed by the line sensor.

When reading both sides of a document with the line sensor, if the illumination light on the opposite side of the document passes through the document, the images on the opposite side are read in an overlapping manner. That is, show-through occurs. Therefore, the image reading positions of the front and back sides are shifted in the document feeding direction to prevent the image on the opposite side from being show-through.

FIG. 12 is a diagram showing an arrangement of front and back images of a document guided to a line sensor via an optical system. This figure 1
In FIG. 2, the symbol LS (LS _A , LS _B ) is a line sensor,
They are arranged on one straight line in the vertical direction on the paper. 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. In the case where a handprint having a size of 216 mm × 93 mm is printed as a document on a microfilm having a width of 16 mm, this phase difference x is about 6 mm in actual dimensions.

[0006] A A _A image reading range with respect to the table image G _A by the line sensor LS _A in FIG. 12. 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 document based on the detection position (start position _ST ) of the start detection sensor that determines the reference position for starting image reading from the position of the document. It is desirable that the original images G _A and G _B fall within the image reading ranges A _A and A _B with an appropriate margin around them. The left image in FIG. 12 shows a case where the document is conveyed to a correct position without tilting. In this state, a margin y of 10 mm is provided before and after the length (93 mm) in the conveyance direction of the document. Therefore, the size of the image reading ranges G _A and G _{B in} the transport direction is (93 + 10 + 10) = 113 mm.

When a check of this size is read at a speed of 240 sheets / minute, the image reading speed of the line sensor LS is set to 20 MHZ, and the time required for main scanning is set to 256 μsec.
c, if the resolution is 200 dpi, the document transport speed V
Is V = 1 ÷ (256 μsec) × (25.4 mm ÷ 20)
0) × 60 = 29.77 m / min = 596.09 mm / sec. Therefore, the transport pitch p of the document in this case is p = 2
9.77 m ÷ 240 sheets = 124 mm / sheet. Here, the distance between the leading edges or the centers of two consecutive documents is referred to as a transport pitch p or a transport interval, and a gap formed between the two documents is referred to as a document gap.

[0008]

In actual bills and checks, stamps or the like are stuck at the same position on many originals, stamps or signatures are attached at the same positions, or folds or signatures are placed near the same positions. There are traces of hand rubbing. For this reason, many bills and checks may be conveyed while being inclined in the same direction with respect to the conveyance direction. The images G _A and G _B on the right side of FIG. 12 show the images of the document tilted in this manner.

In the tilted images G _A and G _B , a part of the images G _A and G _B may deviate from the image reading ranges A _A and A _B. In this case, the line sensor LS
Cannot read portions protruding from the image reading ranges A _A and A _B , and records an image partially missing. If the inclination angle of the originals is too large, the images of two originals continuous in the transport direction are close to each other in the transport direction or overlap in extreme cases. Especially when read shifted in the conveying direction front and back of the image G _A, a G _B for anti-offset,
The image reading phases of the back (or front) image of the preceding document and the front (or back) image of the subsequent document tend to overlap. In this case, the image processing becomes extremely troublesome or impossible to separate the images of the two originals.

In the image reading ranges A _A and A _A adjacent to each other in the transport direction and the time between A _B and A _B , an image is usually processed or transferred in the image processing apparatus. If it is insufficient, proper image processing cannot be performed. Such a problem can occur when the gap between successive documents is too small, even if the documents are not tilted. Conversely, if the gap between the originals is too large, there is a problem that the number of processed originals per time, that is, the reading processing speed is reduced.

The present invention has been made in view of such circumstances, and a first object of the present invention is to provide a control method of an image reading apparatus capable of correctly reading an image of a document even when the document is conveyed at an angle. The purpose of. It is a second object of the present invention to provide an image reading apparatus directly used for carrying out this method. Further, the present invention is directed to an image processing apparatus which prevents inconveniences such as an inability to correctly read an image when a gap between documents becomes too small or too large even if the document is not inclined, and a reduction in processing speed. The third object is to provide

[0012]

According to the present invention, a first object of the present invention is to provide a method of controlling an image reading apparatus for reading an image of a document conveyed continuously at a constant speed by a slit exposure method. A control method for an image reading apparatus, characterized in that the inclination is detected, and in response to the increase of the inclination, the document feeding speed for supplying the original to the conveyance path is slowed to control the document gap to be widened. Is done.

A second object is to provide a document feeding section capable of accommodating a plurality of rectangular documents, a double feed preventing section for separating documents one by one from the document feeding section, and a double feed preventing section. A slit-exposure-type image reading device including a transport unit that transports separated documents 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 documents that have passed through the transport unit. A skew sensor for detecting the inclination of the document entering the transport unit from the double feed prevention unit; and feeding of the document sent by the double feed prevention unit in response to an increase in the inclination of the document detected by the skew sensor. The image reading apparatus is provided with a sheet feeding control unit that controls the document to be widened by reducing the speed.

The skew sensor is formed by two document sensors provided at a fixed distance on a straight line orthogonal to the document conveying direction. 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 at a position as close as possible to the entrance of the transport unit. This is to ensure a long enough time to change the timing at which the next document enters the transport path.

The double feed prevention unit includes a feed roller and a reverse roller. The gap between the originals can be changed by controlling the rotation speed of a paper feed motor that drives the feed roller. If the sheet feeding motor is a stepping motor (pulse motor), it is desirable that the speed can be changed quickly.

The third object can be achieved by detecting the inclination of the document and the gap size of the document based on the output of the skew sensor, and controlling the sheet feeding speed so that the gap size falls within a predetermined range.

[0017]

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 a mirror group, and FIG. 4 is a front view showing the mirror group and an optical system. ,
FIG. 5 is a diagram showing an outline of the arrangement of each unit, FIG. 6 is a perspective view showing an optical system, and FIG. 7 is a left side view in which the vicinity of an image reading unit is enlarged. 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 Apparatus] In FIG. 1, reference numeral 10 denotes an image reading apparatus.
It is mounted on a base box 14 that houses the printer 12. The image reading apparatus 10 is provided with a document feeder 16 at the front thereof and a document discharger 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 mounted on a slope on the front side thereof. The image reading device 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 which can be opened and closed upward around a fulcrum 24 (FIG. 2). The display panel 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 panel 20 or the lid 26 upward.

The original 30 is fed from the original feeder 16,
The sheet is divided for each sheet by the double feed prevention unit 32 and enters 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 a reverse direction. The document 30 enters between the feed roller 36 and the reverse roller 38, and the double feed is prevented, so that only one document 30 is separated. The paper feed motor 34 is formed by a stepping motor, and its speed is controlled by the inclination and gap of the document 30 as described later.

Reference numeral 40 denotes a transport unit. The transport section 40 is driven by a reduction shaft 44 driven by a belt by a transport motor 42, a drive roller group 51 driven by a belt 46 wound around the reduction shaft 44, and an intermediate shaft 48 driven by the belt 46. Holding a plurality of driven rollers 52 that are sequentially arranged in the vertical direction facing the belt 46, and a group of driven rollers that are placed on the conveyor belt 50 from above and are sequentially arranged in a substantially L-shape. And a detachable pressing roller support 54.

The transport belt 50 and the pressing roller support 54 transport the original 30 sent from the double feed prevention unit 32 substantially horizontally while sandwiching the original 30 from above and below, and further drive the drive roller group 51 and the driven roller 51 upward. The group 52 is entered. The document 30 is sandwiched between the driving roller group 51 and the driven roller group 52, is sent almost vertically upward, and is discharged to the document discharge unit 18. The holding roller support 54 is provided with the original feeding unit 31.
Is opened forward (front side) about the fulcrum 35, the hand can be put in and taken out from above, and the original 30 jammed in the transport path 40 can be removed.

In the middle of the vertical transport path of the drive roller group 51, a pair of photographing glass
(56a, 56b) are provided. Glass for photography 5
6, a horizontal and long light source lamp 58 (58a, 58a) is provided.
b) is provided (see FIGS. 2 and 7). Here, each of the lamps 58a and 58b has a different height. That is, the lamp 58a that illuminates the front side of the document 30 is lower than the lamp 58b that illuminates the back side, and therefore, the front image reading position 60a is lower than the back image reading position 60b (FIG. 7).

Further, a black light-shielding film 62 (62a, 62b) is formed on each of the glasses 56a, 56b in order to prevent the transmitted light of the opposite lamps 58b, 58a from entering. Each of the lamps 58a and 58b is provided with a light shielding plate 64 (64
a, 64b) and a light shielding plate 66 to block unnecessary light. Reference numeral 68 denotes a reflector, which is a lamp 5 for illuminating the front side.
A part of the light 8a is reflected and guided to the surface of the document 30 before entering the space between the glasses 56.

The illuminance on the surface of the document 30 illuminated by the light reflected by the reflector 68 is detected by a 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 determined by the image reading position 60 a
By equalizing the incident theta ₁ with respect to, and aligned illumination conditions to the image reading position 60a and the illuminance detection position.

The images on both sides of the original 30 are
When passing between a and b, the image is read by the slit exposure method at the respective image reading positions 60a and 60b. That is, the images on the front and back sides are the slits 7 shown in FIG.
2 (72a, 72b), and are further guided to one imaging lens 74 via a mirror group shown in FIG. 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).

The first mirror 78 has a distance of about 4
The wiring is horizontally arranged so as to form an angle of 5 °, and the images on the front and back surfaces of the document 30 are guided horizontally to the left side surface of the main body case 22 through the glass 56. Second mirror 80 (80a, 80b)
Is arranged along the upper left corner of the main body case 22,
The reflection image of the first mirror 78 is guided downward. Third mirror 8
2 is arranged along the lower left corner of the main body case 22,
The light reflected by the second mirror 80 is received and guided to the imaging lens 78.

Here, the first mirror 78a and the second mirror 80a with respect to the front surface are set at the same height as the image reading position 60a, and the first mirror 78b and the second mirror 80b with respect to the back surface are similarly positioned with the image reading position 60b. They are set at the same height. That is, the difference A between the heights of the image reading positions 60a and 60b is, as shown in FIG.
Equal to the height difference of 80b. The distances B ₁ and C ₁ between the original 30 and the first mirrors 78a and 78b (for example, the distance between the center of the image of the original 30) are lower than the distance B ₁ between the lower first mirror 78a and the higher first mirror 78a. It is larger than the interval C1 between the _first and second electrodes 78b.

The image reading position 6 of the imaging lens 74
The intervals B and C are set so that the conjugate lengths for 0a and 60b are the same. Here, the conjugate length is equivalent to the optical path length here, and the first mirror 78 and the second mirror 80
The distance as B _2, C _{2 and, A + (C 1 + C} 2) = B 1 +
B ₂ . Here, the third mirror 82a,
82b is formed by one common mirror. In the drawing, reference numeral 84 denotes a magneto-optical disk drive device, which is opened to the right as viewed from the front of the main body case 22. The image data read by the CCD line sensor 76 is processed by an image processing device (not shown),
4 is recorded on a magneto-optical disk (MO).

In FIG. 5, reference numeral 86 denotes a trailing edge sensor for detecting the trailing edge of the document 30 being conveyed; 88, a skew sensor for detecting the inclination of the document 30; 90, a start detection sensor for finding a reference position for starting image reading; Is a paper ejection sensor.

[0030]

[Feeding Speed Control] Next, a feeding speed control mechanism will be described with reference to FIGS. FIG. 8 is a diagram for explaining the principle of detecting the inclination 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.

As shown in FIG. 8, the skew sensor 88 has a straight line LN perpendicular to the conveying direction F of the original 30.
Two document sensors 88 positioned above at a predetermined interval a
A, 88B. These original sensors 88A, 88
B is provided at a position symmetrical in the width direction with the center near the center in the running width of the document 30 and the interval a is constant (see FIG. 9). Both of the sensors 88A and 88B can be formed of, for example, a light emitting diode and a light receiving sensor that face each other across the original 30. These sensors 88A, 88
Both outputs of B are input to the OR circuit 94 and the AND circuit 96.

The skew sensor 8 is attached to the original 30 which is now tilted.
In step 8, both sensors 88A and 88B detect the leading edge and trailing edge of the document 30 with a time difference. Therefore, the outputs of the OR circuit 94 and the AND circuit change as shown by A and B in FIG. In this figure, the outputs A and B are turned on (H level) when a document is detected. These outputs A, the rise time difference T _b on the document conveying speed V B in waveform
, The displacement b of the leading edge of the document between the two document sensors 88A and 88B can be obtained as b = _Tb · V. Similarly, by multiplying the time _Tc from the rise of the output signal B to the rise of the output signal A by the transport speed V, the distance c at which one document sensor 88B detects the document 30 is c = _Tc · Determined as V.

Therefore, the inclination θ of the original 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 supplied to a paper feed controller 98 formed by a microcomputer as shown in FIG.
Is input to The paper feed control unit 98 includes a tilt (θ) detection unit 1
00, a document gap (D) detection unit 102, and a document length (d) detection unit 104. The inclination θ is the inclination (θ)
It is determined by the detection unit 100.

Similarly, the document gap (D) is the time T _D from the fall of the waveform of the output signal A to the rise of the output signal B.
Is multiplied by the transport speed V. That is, D = T _D · V. The document length (d) is obtained by d = c · cos θ as described above. Paper feed control unit 98
Controls the feed motor 34 and the like in accordance with the operation shown in FIG. 11 using the obtained inclination (θ), document gap (D) and document length (d).

First, when paper feeding is started (step 20)
0), the paper feed control unit 98 stands by until the skew sensor 88 starts detecting the original (step 202), and interrupts the control software of the present invention when the leading edge of the original 30 comes to the position of the skew sensor 88. Then, the inclination θ, the gap D, and the length d are detected (step 204). Paper feed controller 9
8 is an error if the inclination θ is 21 ° or more (step 2
06). At this time, the paper feed motor 34 is stopped to prevent a new document 30 from entering the transport unit 40, and the transport motor 42 operates until the document 30 is discharged, and then stops. When the inclination θ is large than 21 °, the range A _A document read image, or protrude from the A _B, only the original distance D changes the paper feed speed becomes too low it can not be supported.

If the inclination θ is 6 ° or less, the processing is continued at the normal sheet feeding speed (steps 208 and 21).
0). image G _A If θ is 6 ° or less, G _B is the image reading range A
_A, because there is no possible exit from the A _B. The inclination θ is 6
° (and less than 21 °) (step 20)
6, 208), and decelerates the feed motor 34 (step 2).
12). Here, it is desirable that the sheet feeding 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 immediately reduced in real time in response to the change in the drive pulse.

The speed of the paper feed motor 34 may be continuously reduced in accordance with the increase or decrease of the inclination θ, or may be discontinuously reduced stepwise. As a result of reducing the paper feeding speed, the timing at which the next document 30 enters the transport unit 40 is slightly delayed, and the gap D between the preceding inclined document and the next document increases. Therefore, both documents can be read correctly.

The distance D of the document when the minimum value D _m is smaller than the tolerance decelerates the (step 214), the paper feed motor 34 (step 212). When the gap D is larger than the maximum value D _M (step 216), the speed of the sheet feeding motor 34 is increased (step 218). As a result, the document gap D becomes too small to allow accurate image reading or the gap D
Can be prevented from becoming too large and the processing speed dropping. If the gap D is within the range of D _m and D _M (steps 214 and 216), the paper feed motor 34 operates at the normal speed (step 220).

In this embodiment, the length d of the document is also monitored. When the length d is equal to or _larger than the maximum standard value d _M (step 222), it is determined that the original is out of the standard and an error is generated. That is, in this case, both the sheet feeding motor 34 and the conveying motor 42 are urgently stopped, and the operator waits for the document to be discharged and restarted. The length d is continued operation smaller than the allowable value d _m in standard (step 224).

If the length d is greater than this tolerance d _m ,
That is, if d _m <d <d _M (step 224),
The paper feed motor 34 is stopped to stop reading an image of a new document (step 226), and the document being transported is sent to the paper discharge unit 18 and the transport motor 42 is also stopped (step 228). Then wait for the operator to check.

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. Although one line sensor is commonly used for the front image and the back image of the document, separate line sensors may be used for the front and back surfaces.

[0042]

According to the first aspect of the present invention, the gap between the originals is enlarged by detecting the inclination of the original and decreasing the paper feeding speed in response to the increase in the inclination. The image can be read correctly even when the image is conveyed.

According to the second aspect of the present invention, there is provided an image reading apparatus directly used for implementing the first aspect of the present invention. The skew sensor can be formed by two document sensors arranged at a fixed distance on a straight line perpendicular to the document conveying direction. By providing the skew sensor at a position as close as possible to the entrance of the transport unit, it is possible to secure a long time for controlling the feeding speed of the next document entering the transport unit. Needless to say, the skew sensor may be provided near the exit of the double feed prevention unit.

The double feed prevention unit includes a feed roller and a reverse roller, and can control the sheet feeding speed by changing the speed of a sheet feeding motor for driving the feed roller. In this case, by forming the sheet feeding motor with a stepping motor, the sheet feeding speed can be promptly controlled with good responsiveness.

The gap between the originals can also be detected by using the output of the skew sensor. (Claim 7). In this case, for example, even if the inclination is within the allowable range, if the gap size becomes too small, it is possible to read the image properly by lowering the sheet feeding speed and increasing the gap size,
Conversely, when the gap size becomes excessive, the paper feeding speed can be increased to prevent the document processing speed from lowering.

The paper feeding speed is preferably controlled continuously by increasing or decreasing the inclination of the document or by changing the gap size, but may be controlled discontinuously in two or multiple steps. . In this case, an effect that the control system is simplified can be obtained.

[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. 4 is a front view showing a mirror group and an optical system.

FIG. 5 is a diagram showing an outline of an arrangement of each unit.

FIG. 6 is a perspective view showing an optical system.

FIG. 7 is a left side view in which the vicinity of an image reading unit is enlarged.

FIG. 8 is a view for explaining the principle of tilt detection by a skew sensor;

FIG. 9 is a layout diagram of a skew sensor.

FIG. 10 is a block diagram illustrating functions of a sheet feeding speed control unit.

FIG. 11 is a flowchart of the operation.

FIG. 12 is a layout diagram of a document image guided by a line sensor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 image reading device 16 document feeder 18 document discharger 30 document 32 double feed prevention unit 34 feeder motor 40 transfer unit 42 transfer motor 74 imaging lens 76 line sensor 88 skew sensor 98 feeder controller 100 tilt (θ ) Detector 102 Document gap (D) detector

Continued on the front page F term (reference) 3F102 AA14 AB03 CA03 CB06 EC02 FA05 3F343 FA04 FC11 MA15 MA57 MB04 MB15 MC09

Claims (8)

[Claims] In a control method of an image reading apparatus for reading an image of a document conveyed continuously at a constant speed by a slit exposure method, a tilt of a document entering a document conveying path is detected, and an increase in the tilt is detected. A method for controlling an image reading apparatus, characterized in that control is performed so as to widen a document gap by reducing a sheet feeding speed for feeding a document to a lever conveyance path. 2. A document feeding unit capable of accommodating a plurality of rectangular documents, a double feed preventing unit for separating documents one by one from the document feeding unit, and a document separated by the double feeding preventing unit. And a document discharge unit that collects the documents that have passed through the transport unit, and a document discharge unit that collects the documents passing through the transport unit. A skew sensor for detecting the inclination of the document entering the conveyance unit from the feeding prevention unit, and reducing a feeding speed of the document sent by the double feeding prevention unit in response to an increase in the inclination of the document detected by the skew sensor. An image reading apparatus comprising: a sheet feeding control unit that controls so as to widen a document gap. 3. A skew sensor is formed by two document detection sensors arranged at a predetermined distance on a straight line orthogonal to the document conveyance direction, and the paper feed control unit includes two document detection sensors. 3. The image reading apparatus according to claim 2, wherein the inclination of the document is obtained based on a difference in detection timing. 4. The image reading apparatus according to claim 2, wherein the skew sensor is disposed near an entrance of the transport unit. 5. The double feed prevention unit includes a feed roller driven by a paper feed motor and a reverse roller driven to rotate in a direction opposite to the feed roller, and the paper feed control unit rotates the paper feed motor. The speed is controlled.
Any one of the image reading devices. 6. The image reading device according to claim 5, wherein the sheet feeding motor is formed by a stepping motor. 7. A paper feed control unit detects a gap size of a continuous document along with the inclination of the document based on an output of the skew sensor, controls a feeding speed based on the inclination of the document, and adjusts a gap size of the document. 7. The image reading apparatus according to claim 2, wherein the sheet feeding speed is controlled so as to fall within a predetermined range. 8. The image reading apparatus according to claim 2, wherein the paper feed control unit changes the paper feed speed of the double feed prevention unit discontinuously in a plurality of steps.