JPH11289427A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of an intermittent operation in the case of double-side read processing for an original image. SOLUTION: A capacity of data stored in a front side image storage means 33, 34 and a rear side image storage means 42, 43 is recognized during read scanning, and the capacity of data which is smaller is extracted. Furthermore, a read speed in the subscanning direction of a double side read means is selected based on the extracted data capacity. Thus, in the case that a data transfer speed to an external device 37 is slower than the read speed depending on the performance of the external device 37 and image data are stored in the front side image storage means 33, 34 and the rear side image storage means 42, 43, it is possible to slow down the read speed more than the data transfer speed by selecting the read speed in the subscanning direction to be a prescribed speed depending on the extracted data capacity of either of the storage means whose remaining data are smaller. Thus, it is prevented that each storage means is fully occupied by image data and production of an intermittent in the case of double side read processing is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanner section in an image scanner, a digital copying machine or a facsimile machine, and relates to an image reading apparatus capable of reading both sides of a document image.

[0002]

2. Description of the Related Art Generally, when an image reading apparatus of this type is provided with a double-sided simultaneous reading function, a DRAM which is a dedicated storage means for each of the front and back reading surfaces of a document image is used.
And the like.

In this case, the amount of image data obtained by scanning the original is not increased beyond the memory capacity of the image memory.
A SIBC (Scanner Image Buffer Controller) detects an amount of image data during scanning of a document and causes the image reading apparatus to execute an intermittent operation for intermittently performing a reading process. For example, the memory capacity of the image memory is 2 Mby
In the case of te, the image data amount is 2 Mby during image reading.
If it exceeds te, the reading process is suspended. Here, generally, a stepping motor is used as a drive motor of this type of image reading apparatus, and it cannot be stopped instantaneously due to the nature of the motor. A control method of gradually lowering the speed and stopping the operation is adopted. for that reason,
Rather than temporarily stopping when the image data amount has completely reached 2 Mbytes, the image memory is temporarily stopped at a near full time with some margin in the memory capacity of the image memory. Further, after the suspension, when the memory capacity of the image memory has a margin due to the transfer processing of the image data to the external device (at the time of releasing the near full state), the suspension is released to resume the driving of the motor. Then, the intermittent operation of the reading process is executed. Since the motor cannot be moved instantaneously due to the nature of the motor, a control method called “through-up” is used to restart the reading process by gradually increasing the speed and restarting the reading process.

On the other hand, transfer of image data from an image reading apparatus to an external apparatus connected to the image reading apparatus by SCSI or the like is performed by temporarily storing image data in an image memory and transferring image data from the image memory. The transfer is being performed in parallel. In this case, if the transfer speed of the image data from the image memory is relatively faster than the storage speed of the image data in the image memory, the image data is transferred to the external device without delay. However, when the transfer speed of the image data from the image memory is relatively slower than the storage speed of the image data in the image memory, the image data is gradually accumulated in the image memory. That is, even in such a case, when the image data amount is about to exceed the memory capacity of the image memory, the reading process is temporarily stopped, and the intermittent operation of the reading process is executed.

At present, such intermittent operation in the reading process is repeated several times to several tens of times in one reading process.

[0006]

However, when the original is transported while the stepping motor is repeatedly paused and re-driven by releasing the pause, the vibration of the motor at the time of stopping and restarting is increased. Vibration occurs in the image reading device itself. When the apparatus itself vibrates in this way, the reading restart position of the original image is shifted during the reading processing of the original image, and the original image data that should be present is lost, or the image data is acquired twice. There is a problem that the image is deteriorated. In particular, when a double-sided simultaneous reading function using a contact type image sensor is provided, the document is brought into contact with the contact type image sensor and conveyed, so that loss of image data and deterioration of the image appear remarkably.

In order to reduce the number of intermittent operations during the double-sided reading process, which is the source of such vibrations, a large-capacity image memory may be obtained by increasing the number of memories. Since the image memory must be increased, the cost increases.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image reading apparatus capable of preventing the occurrence of an intermittent operation during a reading process and capable of reading both sides of a document image.

[0009]

According to the first aspect of the present invention,
Double-sided reading means for reading and scanning both the document front side image and the document back side image to obtain front side image data and back side image data; front side image storage means for temporarily storing front side image data obtained by the both side reading section; The back side image storage means for temporarily storing the back side image data obtained by the both side reading means, the data capacity storable in the front side image storage means and the data capacity storable in the back side image storage means are recognized during reading scanning. Capacity extracting means for extracting the smaller remaining data capacity; speed switching means for switching the reading speed in the sub-scanning direction of the duplex reading means based on the data capacity extracted by the capacity extracting means; And a data transfer unit for transferring the obtained front side image data and the back side image data stored in the back side image storage unit to an external device.

Therefore, the data capacity that can be stored in the front-side image storage unit and the back-side image storage unit in which the front-side image data and the back-side image data obtained by the reading scan by the double-side reading unit are temporarily stored, respectively, Recognized during the reading scan, the smaller remaining data capacity is extracted. Further, the reading speed in the sub-scanning direction of the double-sided reading means is switched based on the data capacity extracted by the capacity extracting means. Thereby, for example, the data transfer speed to the external device is lower than the reading speed due to the performance of the external device,
Even when each image data is stored in the front-side image storage unit and the back-side image storage unit, the reading speed in the sub-scanning direction is set to a predetermined speed in accordance with the smaller remaining data capacity extracted by the capacity extraction unit. By switching to, the reading speed can be set to a speed corresponding to the smaller remaining data capacity, and the reading speed can be made lower than the data transfer speed. Is prevented from being full of image data.

According to a second aspect of the present invention, in the image reading apparatus according to the first aspect, the capacity extracting means can store the data capacity which can be stored in the front side image storing means and the back side image storing means even before scanning. By recognizing the respective data capacities, the smaller remaining data capacity is extracted.

Therefore, the data capacity storable in the front side image storage means and the data capacity storable in the back side image storage means are recognized before the scanning for scanning, and the smaller remaining data capacity is extracted. Since the reading speed can be set to a speed corresponding to the smaller data capacity from the start of the reading scan, and the reading speed can be made lower than the data transfer speed, the front side image storage means and the back side image storage means Are prevented from becoming full of image data immediately after the start.

According to a third aspect of the present invention, in the image reading apparatus of the first aspect, the reading speed in the sub-scanning direction of the double-sided reading means by the speed switching means is a multi-step speed set in advance based on the data capacity. One speed can be selected and switched.

Therefore, the reading speed in the sub-scanning direction can be switched by selecting one speed from multi-step speeds set in advance based on the data capacity. Fine adjustment of the speed is made possible, and unnecessary extension of the scanning time is avoided.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. The image reading apparatus according to the present embodiment uses a SCSI (Small Computer Systems Interface).
Is applied to image scanners that are implemented as standard.

FIG. 1 is a schematic front view showing the structure of the image scanner 1. As shown in FIG. 1, the image scanner 1 is an ADF (Automatic Document Feeder).
The ADF 2 includes a front surface reading unit 3 on which the original 2 is placed and which can select the original fixing mode and the original conveying mode, and both sides can be simultaneously read in the original conveying mode. I have.

First, the configuration of the front side reading unit 3 will be described. The front surface reading unit 3 has a contact glass G on which a document to be read is placed, and a first traveling body on which a reflecting mirror 5 and a light source 6 are mounted is provided at a position facing the contact glass G from below. 7 is provided movably in the sub-scanning direction A. In the reflected light path of the first traveling body 7, a second traveling body 9 whose optical path is turned by two reflecting mirrors 8 is provided movably in the sub-scanning direction A. Is a CCD (Charge C) through the imaging lens 10.
oupled Device) 11 is provided.

A traveling body motor 12 composed of a stepping motor is connected to the first traveling body 7 and the second traveling body 9 by a pulley, a wire, or the like. It is movable. By moving the two traveling bodies 7 and 9 in this manner, the read image of the read original placed on the contact glass G is read and scanned by the CCD 11.

The scanning of the original to be read by the front surface reading unit 3 is executed under the setting of the book mode which is the original fixed mode. The ADF mode is also set as an operation mode so that it can be switched by an operation unit (not shown). Under the setting of the ADF mode, as shown by a broken line at the right end in the drawing, the two traveling bodies 7, 9 are moved to the front stop reading position 13 which is the home position.
The scanned image is read and scanned by the CCD 11 by sequentially transporting the read document by the ADF 2 in a state where the document is set in the ADF 2.

The ADF 2 includes a document tray 14, a pickup roller 15, a pair of registration rollers 16, a transport drum 17, a pair of transport rollers 18, a pair of discharge rollers 19, and the like. The read original is sequentially conveyed in the sub-scanning direction A so as to pass through, and is discharged to the discharge tray 20. The paper discharge tray 20 includes a document pressure plate 21.
The original pressure plate 21 is openable and closable with respect to the contact glass G. The pickup roller 15, the registration roller 16, the transport drum 17, the transport roller 18, and the paper discharge roller 19 of the ADF 2 have a paper feed motor 50 composed of a stepping motor (see FIG. 2).
Are connected by a gear train or the like.

Next, the configuration of the back surface reading section 4 will be described. The back surface reading unit 4 interposes the contact type image sensor 23 and the white roller 24 across the conveyance path at a back surface reading position 22 set downstream of the conveyance drum 17 of the ADF 2 in the document conveyance direction and in front of the conveyance roller 18. It is configured by disposing them facing each other. Here, the contact type image sensor 23 is for reading a document surface (back surface) on the opposite side to the CCD 11 side, is provided downward on the upper side of the transport path, and has a lamp for irradiating the document surface and a 1: 1 magnification. This is a unit-size photoelectric conversion element configured by integrating an imaging lens array and a sensor array. The white roller 24 located on the opposite side of the conveyance path is also used as a white member for shading correction at the time of reading by the contact image sensor 23.

Further, a unit substrate 25 constituting an electric system described below is built in the lower part of the inside of the image scanner 1. Next, the block structure of the electrical system of the image scanner 1 will be described below with reference to FIG.

First, an SDU (Scanner Driving Unit) 2
SBU (Sensor Board Unit) by driving the light source 6 and the traveling body motor 12 by the power supply from the
The reflected light from the front side reading document incident on the CCD 11 on the CCD 27 is converted into analog image data having a voltage value corresponding to the light intensity in the CCD 11, and is divided into odd bits and even bits and output. Is done. This analog signal is sequentially output to an MBU (Mother Board Unit) 28 and an AHP (Analog data Handling Peripheral) 29
After the dark potential portion is removed by O, the odd bit and the even bit are combined, and the gain is adjusted to a predetermined amplitude.
The digital signal is input to the D converter 30 and converted into a digital signal.
The image data digitized by the MBU 28 is stored in an NCU on an SCU (Scanner Control Unit) 31 on which a CPU 46, an EPROM 47, and a RAM 48 for controlling each unit are mounted.
Shading correction, gamma correction, M
After TF correction and the like are performed, binarization processing is performed. The binarized image data is output as a video signal together with a page synchronization signal, a line synchronization signal, and an image clock.

The video signal output from the NIPU 32 is a DRAM (Dynamic Random) which is a surface image storage means.
Access Memory 33 and SIMM (Single Inline Memo)
ry Module) 34 is input to SIBC 35 which is a memory controller for surface reading, and stored as image data in DRAM 33 or SIMM 34. DRAM
The image data stored in the SIMM 33 or the SIMM 34
The data is transferred from the BC 35 to the external device 37 via the SCSI controller 36 functioning as data transfer means.

Here, the SIBC 35 scans the DRAM 33 and the SIM before the scanning of the front side original image by the CCD 11.
It recognizes the remaining memory capacity, which is the data capacity that can be stored in M34, and transmits it to the memory amount detection unit 45 described later. Further, the SIBC 35 recognizes the remaining memory capacity of the DRAM 33 and the SIMM 34 even during reading scanning of the front side document image and transmits the same to the memory amount detection unit 45.

On the other hand, the analog image signal of the back-side read original that has been photoelectrically converted by the contact image sensor 23 is an RSBU.
The signal is converted into a digital image signal by the AHP 39 and the A / D converter 40 on 38. The image data digitized by the RSBU 38 is transmitted to the NIPU 4 on the SCU 31.
1 is binarized and output as a video signal.

The video signal output from the NIPU 41 is stored in a DRAM 42 or a SIMM 4
3 that is a back-side reading memory controller that manages
The image data is input to the BC 44 and stored in the DRAM 42 or the SIMM 43 as image data. DRAM 42 or SIM
The image data stored in M43 is transmitted from SIBC44 to S
The data is transferred to the external device 37 via the CSI controller 36.

Here, the SIBC 44 performs DRA before reading the back side document image by the contact type image sensor 23.
The remaining memory capacity of the M42 and the SIMM 43 is recognized and transmitted to the memory amount detection unit 45. In addition, SIBC44
Even during the scanning of the back side document image, the remaining memory capacity of the DRAM 42 and the SIMM 43 is recognized and transmitted to the memory amount detection unit 45.

The memory amount detector 45 detects the SI before the reading scan.
The remaining memory capacity transmitted from the BC 35 is compared with the remaining memory capacity transmitted from the SIBC 44, and only the memory remaining capacity M (see FIG. 3) having the smaller remaining capacity is extracted and the CP is extracted.
It has the function of transmitting to U46. Therefore, when double-sided simultaneous reading is selected, the memory remaining capacity transmitted from the SIBC 35 and the SIB
The remaining memory capacity transmitted from C44 is compared with the remaining memory capacity M by the memory capacity detection unit 45, and only the remaining memory capacity M having the smaller remaining capacity is extracted and transmitted to the CPU 46. When only front side reading is selected, the SIBC3
Only the remaining memory capacity M transmitted from 5 is transmitted to the CPU 46. In addition, the memory amount detection unit 45 determines the remaining memory capacity transmitted from the SIBC 35 during the reading scan and the SIBC
It has a function of outputting a signal (near-full detection signal S) when the remaining memory capacity M having the smaller remaining capacity of the remaining memory capacity transmitted from 44 becomes a predetermined remaining memory capacity (near full time point). ing. Here, FIG. 3 is a schematic diagram showing the relationship between the remaining memory capacity M and the near full detection signal S in the memory amount detection unit 45. That is, the memory amount detection unit 4
For example, the hardware configuration of No. 5 outputs near-full detection 1 when the remaining memory capacity M becomes M1, and outputs near-full detection 2 when the remaining memory capacity M becomes M2. I have. Therefore, during the reading scan, the SIBC
35. The remaining memory capacity transmitted from the SIBC 44 is compared with the remaining memory capacity transmitted from the SIBC 44, and only the memory remaining capacity M having the smaller remaining capacity is extracted. At the time when the remaining capacity becomes near full, the near full detection signal S is output to the memory amount detection unit 45.
To the CPU 46. That is, the memory amount detection unit 45 functions as a capacity extraction unit.

The data bus from the SIBC 35 or the SIBC 44 to the SCSI controller 36 is, for example, a device for transferring image data from the SIBC 35 to the SCSI controller 36.
During output, the other SIBC 44 is configured to have a high impedance, so that each image data does not interfere.

The CPU 46 controls the light source 6 via the SDU 26.
And the operation timing of the traveling body motor 12 is controlled by drive pulse control. Further, the AD connected to the MBU 28
A U (ADF Driving Unit) 49 has a function of relaying the power supply of electrical components used for the ADF 2, and the CPU 46 controls the operation timing of the sheet feeding motor 50 of the ADF 2 by drive pulse control via the ADU 49.

In addition, the EPROM 47 stores various data files. The contents of this data file are written to a table provided in the RAM 48 when the image scanner 1 is started.

FIG. 4 is a schematic diagram showing the file structure of the link file F of the remaining memory capacity / reading sub-scanning speed. As shown in FIG. 4, the memory remaining capacity / reading sub-scanning speed link file F indicates that “memory remaining capacity M”, “near-full detection signal S”, and “reading sub-scanning speed V” are N (N ≧ 2).
It is held in association with each other over the stages. For example,
“Memory remaining capacity M” is “M0 (memory capacity) ≧ M> M
In the case of "1" or "near full detection signal S" is "near full detection 1" in which the near full time point is "M1", "read sub-scanning speed V" becomes "V1" and "memory remaining capacity M"
Is “M1 ≧ M> M2” or “near-full detection signal S” is “near-full detection 2” in which the near-full time point is “M2”, the “read sub-scanning speed V” becomes “V2”. Here, the “reading sub-scanning speed V” is made variable by controlling the driving pulse of the traveling body motor 12 or the sheet feeding motor 50 by the CPU 46.

In such a configuration, for example, when the double-sided reading processing of the original in the ADF mode is selected, the remaining capacity is small among the remaining memory capacities transmitted from the SIBC 35 and the SIBC 44 to the memory capacity detection unit 45. Only the remaining memory capacity M is the memory amount detection unit 45
To the CPU 46.

The CPU 46 sends the transmitted memory remaining capacity M
A drive pulse corresponding to the reading sub-scanning speed V corresponding to
Transmit to U49. As a result, the document conveying speed by the paper feed motor 50 of the ADF 2 is determined as the reading sub-scanning speed V, and simultaneous double-sided reading of the document is started. Here, FIG. 5 is a time chart showing an example of the speed profile of the image scanner 1. For example, if the memory amount detection unit 45 determines that the remaining memory capacity transmitted from the SIBC 35 is smaller than the remaining memory capacity transmitted from the SIBC 44, the memory remaining capacity from the SIBC 35 is determined as the remaining memory capacity. To the CPU 46. When the remaining memory capacity M transmitted from the SIBC 35 corresponds to “M0 ≧ M> M1,” the reading sub-scanning speed V becomes “V
At a point a when the speed becomes 1 "constant, reading of the front and back sides of the document is started at the front stop reading position 13 and the back reading position 22.

The image data on the front side scanned and read at the reading sub-scanning speed of "V1" is stored as image data in the DRAM 33 or the SIMM 34, and the image data on the back side is DRA.
The image data is stored in M42 or SIMM43. Then, by storing the image data of the front surface (or the back surface) that has been read and scanned, the DRAM 3 is read during the scan.
3 and the remaining memory capacity M of the SIMM 34 becomes “M1” (or the remaining memory capacity M of the DRAM 42 and the SIMM 43 becomes “M1”), the SIBC 35 (or the SIBC 44) detects the “near full detection 2”. A signal is transmitted. At the near-full time point b where the "near-full detection 2" is transmitted in this way, the feed motor 50 is slewed down and the reading sub-scanning speed V is switched to "V2".

Further, by storing the image data of the front surface (or the back surface) read and scanned, the remaining memory capacity M of the DRAM 33 and the SIMM 34 becomes "M" during the read scan.
2 "(or the DRAM 42 and the SIMM 4
3 when the remaining memory capacity M becomes “M2”), SIB
"Near-full detection 3" from C35 (or SIBC44)
Is transmitted. Even at the near-full time point c when the “near-full detection 3” is transmitted in this way, the feed motor 50 is again through-down, and the reading sub-scanning speed V is switched to “V3”.

Here, the front side image data stored in the DRAM 33 or the SIMM 34 (or the back side image data stored in the DRAM 42 or the SIMM 43) is
Since the image data is transferred from the BC 35 (or the SIBC 44) to the external device 37 via the SCSI controller 36, the transfer speed of the image data is changed to the DRAM 33 or the SIMM3.
4 (or the reading sub-scanning speed V), the image data of the front surface stored in the DRAM 33 or the SIMM 34 (or the DRAM 42 or the SIMM 43). , The image data of the back surface stored in the memory is reduced, and the remaining memory capacity is increased. This allows
When the remaining memory capacity M of the DRAM 33 and the SIMM 34 becomes “M2” or more during the reading scan (or the DRAM 4
2 and the remaining memory capacity M of the SIMM 43 becomes “M2” or more), and the signal of “near full detection 2” is transmitted from the SIBC 35 (or the SIBC 44). At the near full time point d when the "near full detection 2" is transmitted in this way, the feed motor 50 is slewed up and the reading sub-scanning speed V is switched to "V2".

Further, when the remaining memory capacity increases and "near full detection 1" is transmitted at near full time point e, the feed motor 50 is slewed up and the reading sub-scanning speed V is switched to "V1". At the time point f when the document has passed the front stop reading position 13 and the back reading position 22, the reading of the front and back sides of the document is completed.

Here, for example, due to the performance of the external device 37, the data transfer speed to the external device 37 is lower than the reading sub-scanning speed V, and the DRAM 33 and the SIMM 34 and the DRAM 4
2 and the SIMM 43, the remaining memory capacity / reading sub-scanning is performed at a reading sub-scanning speed V corresponding to the smaller remaining memory capacity M extracted before and during the scanning. Select from the speed link file F and switch appropriately. As a result, the reading sub-scanning speed V can be set to a speed corresponding to the smaller remaining memory capacity M, and the reading sub-scanning speed V can be made lower than the data transfer speed.
33 and SIMM 34 and DRAM 42 and SIMM 4
3 is prevented from being full of image data, and the occurrence of an intermittent operation during double-sided reading processing is prevented, so that deterioration of image quality is prevented. Also, the reading sub-scanning speed V
Can be switched to N (N ≧ 2) stages based on the remaining memory capacity M, so that the fine adjustment of the speed can be made by finely setting the division of the remaining memory capacity M, and the reading scan by switching the speed can be performed. Unnecessary extension of time is avoided.

[0041]

According to the first aspect of the present invention, it is possible to store the front side image data and the back side image data obtained by the scanning by the double side reading means in the front side image storage section and the back side image storage section, respectively. During the scanning by the capacity extracting means, the smaller data capacity is extracted, and the reading speed in the sub-scanning direction of the double-sided reading means is determined based on the data capacity extracted by the capacity extracting means. By switching, for example, even if each image data is accumulated in the front image storage unit and the back image storage unit because the data transfer speed to the external device is lower than the reading speed due to the performance of the external device, By switching the reading speed in the sub-scanning direction to a predetermined speed according to the smaller remaining data capacity extracted by the extracting means, Can be set to a speed corresponding to the remaining smaller data capacity or lower than the data transfer speed, preventing the front side image storage means and the back side image storage means from being filled with image data, Since the occurrence of an intermittent operation during the double-sided reading process can be prevented, the image can be read without deteriorating the image quality.

According to the second aspect of the present invention, in the image reading apparatus according to the first aspect, the data capacity storable in the front side image storage means and the data capacity storable in the back side image storage means even before scanning. By recognizing each and extracting the smaller remaining data capacity, it becomes possible to set the reading speed to the speed corresponding to the smaller remaining data capacity from the start of the scanning and to make the reading speed lower than the data transfer speed. In addition, it is possible to prevent the front side image storage unit and the back side image storage unit from being full of image data immediately after the start of the reading scan.

According to the third aspect of the present invention, in the image reading apparatus according to the first aspect, the reading speed in the sub-scanning direction is increased by one from a preset multi-step speed based on the data capacity.
Since the two speeds can be selected and switched, the speed can be finely adjusted by finely setting the division of the data capacity, and unnecessary extension of the reading scanning time due to the speed switching can be avoided.

[Brief description of the drawings]

FIG. 1 is a schematic front view showing the structure of an image scanner according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating connection of an electrical system of the image scanner.

FIG. 3 is a schematic diagram illustrating a relationship between a remaining memory capacity and a near full detection signal in a memory capacity detection unit.

FIG. 4 is a schematic diagram showing a file structure of a memory remaining capacity / read sub-scanning speed link file.

FIG. 5 is a time chart illustrating an example of a speed profile of the image scanner.

[Explanation of symbols]

 33, 34 Front image storage means 36 Data transfer means 37 External device 42, 43 Back image storage means 45 Capacity extraction means M Data capacity V Reading speed in sub-scanning direction

Claims (3)

[Claims] 1. A double-sided reading means for reading and scanning both a front side image and a back side image of a document to obtain front side image data and back side image data, and a front side for temporarily storing front side image data obtained by the both side reading means. Image storage means, a backside image storage means for temporarily storing backside image data obtained by the double-sided reading means, a data capacity storable in the frontside image storage means and a data capacity storable in the backside image storage means. A capacity extracting means for recognizing a smaller remaining data capacity during reading scanning, and a speed switch for switching a reading speed in the sub-scanning direction of the double-sided reading means based on the data capacity extracted by the capacity extracting means. Means for transferring the front side image data stored in the front side image storage means and the back side image data stored in the back side image storage means to an external device. Image reading apparatus comprising: a data transfer means for the. 2. A capacity extracting means for recognizing a data capacity storable in a front-side image storing means and a data capacity storable in a back-side image storing means even before reading scanning, and extracting a smaller remaining data capacity. The image reading device according to claim 1. 3. The image according to claim 1, wherein the reading speed in the sub-scanning direction of the double-sided reading device by the speed switching device is switched by selecting one speed from multi-stage speeds set in advance based on the data capacity. Reader.