JP3378749B2 - Image scanner - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image scanner, and more particularly to an image scanner which simultaneously reads front side image data and rear side image data of a double-sided original and transfers the image data to a host computer at high speed.

[0002]

2. Description of the Related Art One of image input devices for inputting image data to a computer is an image scanner used for data input in an electronic filing device. For example, in a financial industry such as a bank or an insurance company, it is necessary to input to a computer the items described in a huge number of contracts and other forms generated in business. Therefore, in order to perform this input accurately and at high speed and to realize the search function etc.,
An electronic filing system is constructed by directly inputting the description items on a form as image data into a computer by an electronic filing device. The image scanner is an indispensable device for inputting the description items on the form as image data.

The image scanner takes in image data as follows. For example, an operator places a plurality of forms on the paper feed unit of the image scanner. The image scanner supplies (feeds) one sheet from the paper feeding unit to the reading unit. A line sensor (CCD) of the reading unit reads image data such as characters on a form and transfers it to a host computer in the form of image data (digital data) that can be processed by a computer. The scanned form is ejected to the paper ejection section of the image scanner.

[0004]

By the way, due to various social demands such as paper saving, there is a growing demand for contract matters to be stated on both the front and back sides of a contract document. ing. Moreover, it has become common to construct an electronic filing system because of its excellent functions. Therefore, it is easily expected that the amount of data to be input to the computer by using the image scanner will only increase. Therefore, the image scanner is required to speed up data input.

However, the conventional image scanner is of a type in which image data of a document such as a form is read on only one side. That is, it is a single-sided scanner. Therefore, using a conventional image scanner, a form (double-sided document) in which data (image data) such as characters is written on both the front and back sides of the document
It is considered that two reading operations are required when inputting the image data of. Specifically, after the image scanner finishes the operation of reading the image data on the front side of the form, the operator reverses the ejected original document, sets it in the paper feed section, and then re-images it on the image scanner. Data read operation must be performed. Therefore, according to this method, when the form is a double-sided original, the operator must always intervene to read it, which is troublesome. Further, it takes time for the two reading operations and the procedure of the operator, which is an obstacle to speeding up the input of image data.

Further, the connection interface of the image scanner in the existing computer (or electronic filing apparatus) is a conventional image scanner (single-sided scanner).
However, it is not preferable to change this because it is established to some extent. That is, if a new interface for transferring image data of a double-sided original is newly set, it is necessary to newly set the interface in an existing computer, which imposes a heavy burden on the user and is not realistic. Therefore, an image scanner that outputs image data of a double-sided original is required to be connectable to a computer without changing the operating environment of the conventional single-sided scanner. That is, it is necessary to increase the speed while maintaining the compatibility with the conventional image data interface both logically and physically.

Further, if the image data of the read double-sided original is transferred to the computer at the same data transfer speed as in the conventional case, the speed of inputting the image data cannot be increased. That is, the amount of data to be transferred is doubled per unit time by simultaneous reading of double-sided originals, but if the data transfer speed remains the same, there is a possibility that sheets will not be continuously supplied. Specifically, the speed of image data input processing is limited by the data transfer speed to the computer rather than the reading capability (driving frequency) of the line sensor (CCD). This means that even if two-sided originals are simultaneously read, the input processing amount (throughput) of a form or the like per unit time in the computer is almost the same (about 1/2 in the number of sheets). Therefore, also from this point, it is necessary to increase the data transfer rate.

An object of the present invention is to provide an image scanner for simultaneously reading the image data of the front side and the image data of the back side of a double-sided original. Another object of the present invention is to provide an image scanner that simultaneously reads the image data of the front and back sides of a double-sided original and transfers the data to a host computer at high speed.

Another object of the present invention is to provide an image scanner in which the data transfer speed of the image data of the front and back sides of a double-sided original is variable.

[0010]

FIG. 1 is a block diagram of the principle of the present invention, showing the configuration of an image scanner 100 according to the present invention. The image scanner 100 is connected to the host computer 200 and performs data transfer with the host computer 200 according to a predetermined interface.

The image scanner 100 includes a sheet 30.
The first reading means 1 for the double-sided reading mode for reading the image data on the front side of 0, the second reading means 2 for the double-sided reading mode for reading the image data on the back side of sheet 300, and the image data on the front side of sheet 300 And a third reading unit 3 for a single-sided reading mode that reads the image at a position different from the first reading unit, and a first reading unit that simultaneously reads the image data written on the front surface and the back surface of the paper 300.
And a reading control unit 4 that controls the second reading unit and controls the third reading unit so as to read the image data written on the surface of the sheet 300, and the images read by the first to third reading units. Predetermined calculation is performed on the data to form image data of the front and back sides of the paper 300.
Then, the signal processing means 5 to be written in the image memory (66) and the image data written in the image memory
Is read at a predetermined speed and data is transferred to the host computer 200 according to a predetermined interface.

In the double-sided reading mode, under the control of the reading control means 4, the first and second reading means 1 and 2 simultaneously read the image data of the front surface and the back surface of the paper 300, and the signal processing means 5 makes the image data. To form
The image memory is written in the image memory (66), and the data transfer means 6 is an image memory according to a predetermined interface.
The image data written in (66) is transferred at the first speed (high speed). At this time, the image memory
When writing and reading (66), the image
A table that is the image data of the front side of the paper 300.
For use with the table writing unit (661) that writes write data
The back writing data, which is the image data on the back of the paper 300,
The back writing section (662) to be written is divided into two, and the first
The front writing data for the paper 300 is the front writing portion.
When the data has been written to the specified position of
Readout of data and endorsement on first paper 300
Start writing the embedded data, and
The back writing data of the
When the data is written in
And writing the table writing data for the next paper 300
Start to include. In the single-sided reading mode, the third reading unit 3 controls the sheet 3 under the control of the reading control unit 4.
00 image data on the surface is read, and data transfer means 6
Transmits the image data on the surface of the sheet 300 at a second speed (speed depending on the driving frequency of the CCD, for example, conventional speed) slower than the first speed according to a predetermined interface.

As will be described in the example below,
Actually, the first reading means 1 and the third reading means 3 are the same, and their positions are moved and used in different reading modes.

According to the image scanner 100 of the present invention, the image data on the front surface and the back surface of the sheet 300 such as a form can be simultaneously read on both sides by the double-sided reading mode using the first and second reading means 1 and 2. You can That is, the image scanner 100 of the present invention is a double-sided scanner. Therefore, when inputting image data of a form (double-sided original) in which data such as characters (image data) are drawn on both the front surface and the back surface, the image scanner 100 of the present invention can perform an image by substantially one reading operation. You can read the data. As a result, even when the paper 300 is a double-sided original, the image data can be formed without the intervention of the operator, and the speed of inputting the image data can be increased.

Further, according to the image scanner 100 of the present invention, data transfer can be performed according to a predetermined interface in both the double-sided reading mode and the single-sided reading mode. By making this interface similar to the traditional interface,
The image scanner 100 of the present invention may be compatible with a conventional image data connection interface. Therefore, the conventional image scanner (single-sided scanner)
The image scanner 100 of the present invention can be connected to the host computer 200 having an interface corresponding to the above without changing the interface (without changing the operating environment of the single-sided scanner at all).

Further, according to the image scanner 100 of the present invention, the data transfer rate in the double-sided reading mode is set to be higher than the data transfer rate in the single-sided reading mode (for example, 2 in accordance with a predetermined interface).
Can be doubled. Therefore, the data transfer time of image data in the double-sided reading mode in which there is twice the data amount per unit time can be made equal to the data transfer time of image data in the single-sided reading mode. As a result, the input processing amount (throughput) of a form or the like in the host computer 200 per unit time can be doubled.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, for convenience of explanation, a double-sided reading mode and a single-sided reading mode in the image scanner 100 of the present invention will be described.

2 and 3 show the structure of the image scanner 100. The image scanner 100 has a housing 80.
A front surface optical unit (carrier) 10 which is a main part of the first reading means 1 and a back surface optical unit 20 which is a main part of the second reading means 2 are provided therein. The front surface optical unit 10 and the back surface optical unit 20 each include a known light source for reading image data, a lens system, and a line sensor (CCD).

The optical unit 20 for the back side is used only in the double-sided reading mode, and thus is fixedly provided to the housing 80. Since the front surface optical unit 10 is used in both the double-sided reading mode and the single-sided reading mode, it is provided so as to be movable in a predetermined direction (as a carrier type). That is, the surface optical unit 10 is
In the double-sided reading mode, it is used as a main part of the first reading means 1 at the position shown in FIG. 2, and in the single-sided reading mode, it is moved in the arrow direction shown in FIG. Used as the main part of the means 3. Therefore, as mentioned above, in practice, the first
The reading means 1 and the third reading means 3 are the same and are used by moving their positions in different reading modes.

In the double-sided reading mode, as shown in FIGS. 2 and 3, a plurality of sheets 300 are placed on the sheet stacker 81 and are automatically transferred to the first and second reading units 1 and 2 one by one. Supplied. Therefore, the double-sided reading mode is also the ADF (Auto Document Feeder) mode.
The sheet of paper 300 is first fed by the sheet feeding means 7 mainly composed of a pick roller 47, feed rollers 48 and 49.
And the second reading means 1 and 2. That is,
The sheet feeding means 7 feeds the sheet 300 by feeding the sheet in a predetermined direction at a predetermined speed. Specifically, the paper 300 is the pick roller 47.
Are picked up one by one by the feed roller 48, fed to the feed roller 49 through a predetermined reading position by the feed roller 48, and discharged onto the paper discharge table 82 when the reading is completed. Therefore, the sheet 300 is moved in the predetermined direction during this period, and the first and second reading units 1 and 2 are fixed. The speed of movement of the paper 300 is a predetermined constant speed. This speed mainly depends on the drive frequency of the line sensor.

The first and second reading means 1 and 2 are
The image data of the sheet 300 is read at each of predetermined reading positions. Here, as shown in FIG. 3 (and FIG. 1), the reading positions of the first and second reading units 1 and 2 are set to be slightly different from each other in the feeding direction of the sheet 300. Specifically, the reading position of the first reading unit 1 is slightly upstream of the reading position of the second reading unit 2 in the sheet feeding direction.

As a result, when reading, the first and second
The reading means 1 and 2 can be prevented from interfering with each other. That is, when the paper 300 is irradiated with light from the light sources of the front optical unit 10 and the back optical unit 20 and the reflected light is detected by the line sensor, the paper 300 is transparent at the same reading position, and Image data is mistakenly read for the back side and image data for the back side is mistaken for the front side. Therefore, the amount of deviation between the reading positions of the first and second reading means 1 and 2 is such that they do not interfere with each other, and is determined in terms of structural design.

In the single-sided reading mode, as shown in FIG. 2, one sheet of paper 300 is placed on the plate-shaped platen (platen glass) 83 by the operator. At this time, the surface of the paper 300 is on the lower side (the platen 83 side). The front surface optical unit 10 is moved to the start position under the platen 83 prior to the start of the single-sided reading mode, and during the single-sided reading mode, a predetermined speed is set in the same direction as the arrow in FIG. 2 (sub-scanning direction). Can be moved with. The movement of the surface optical unit 10 is performed by a (stepping) motor 45 and a belt 46. During this time, the paper 30
0 is fixed on the platen 83.

FIG. 4 shows the structure of the image scanner 100. The microprocessor 8 controls the reading control unit 4, the signal processing unit 5, and the data transfer unit 6 (and the sheet supply unit 7) to control the entire image scanner 100. Further, the microprocessor 8 switches between the double-sided reading mode and the single-sided reading mode in response to a predetermined instruction input from the outside of the image scanner 100 by the operator. That is, the control signals necessary for executing these modes are formed and input to the reading control means 4, the signal processing means 5, the data transfer means 6 (and the paper supply means 7). Further, the microprocessor 8
The data transfer rate in the data transfer means 6 is controlled to a specified value in response to an operator's input of a predetermined instruction from outside the image scanner 100. Here, in the double-sided reading mode, the operator (first)
The data transfer rate is in the single-sided reading mode (second
The data transfer rate is about twice as fast. The first and second data transfer rates are variable within a predetermined range.
This range covers the data transfer means 6 and the host computer 2.
00 depends on the hardware of 00.

The first reading means 1 is composed of a line sensor (sensor) 11, an amplifier (amplifier) 12 and an analog / digital converter (A / D) 13. Line sensor 11
Is a CCD and outputs an image signal corresponding to the image data on the paper 300. This image signal is an analog signal. The analog output of the line sensor 11 is the amplifier 12
Then, the signal is amplified to a predetermined level by the analog-to-digital converter 13 and converted into a digital signal, which is then input to the signal processing means 5. This digital signal is, for example, a signal of 8 bits (256 gradations) per pixel. In addition,
In order to perform optimum AD conversion, known signal level correction processing using white level values and black level values is performed.

The second reading means 2 has the same structure as the first reading means 1. Therefore, in the double-sided reading mode, the signal processing unit 5 substantially parallels the digital signal of the front side of the sheet 300 from the first reading unit 1 and the digital signal of the back side of the sheet 300 from the second reading unit 2. Further, in the single-sided reading mode, the digital signal (only) of the surface of the sheet 300 from the first reading means 1 is input.

The reading control means 4 includes a sensor control section 4
1, a motor controller 42, a frequency voltage converter 43, a motor driver 44, and a motor 45. Sensor control unit 4
Reference numeral 1 is a line sensor 11, an amplifier 12 and an analog-digital converter 1 of the first and second reading means 1 and 2.
It forms the control signals necessary to control 3 and controls them. The motor control unit 42 controls the motor 45 by forming a control signal necessary for controlling the motor 45 and supplying the control signal to the frequency-voltage conversion unit 43 and the motor driver 44. Note that the reading control means 4 is actually provided corresponding to the line sensors 11 and 21 and the like. As the motor 45, an ADF (stepping) motor that supplies the paper 300 in the double-sided reading mode, a motor (stepping) that drives the first reading unit 1 in the sub-scanning direction in the single-sided reading mode, and the like are provided. These motors 45 are controlled by a motor control unit 42 provided corresponding to each of them.

The signal processing means 5 performs well-known signal processing on the digital signals input from the first and second reading means 1 and 2 to form optimized image data. For example, the signal processing means 5 performs well-known white level control processing, shading correction processing, MTF correction (image enhancement) processing, gradation correction processing by gamma conversion, enlargement / reduction processing, fixed slice or floating slice on the input digital signal. Optimized image data of 8 bits per pixel or 1 bit per pixel (8 bits for 8 pixels) by performing line diagram binarization process by JPEG, photo binarization process by dither method or error diffusion method, etc. To form. Actually, the signal processing means 5 is provided in two systems corresponding to each of the first and second reading means 1 and 2, but the two systems are configured to share a part of their processing circuits.

The data transfer means 6 receives the optimized image data input from the signal processing means 5 from the host computer 2
Data transfer to 00. Here, the image data to be transferred is the first and second image data in the double-sided reading mode.
Image data of the front surface and the back surface of the paper 300 from the reading means 1 and 2, and in the single-sided reading mode, it is (only) the image data of the front surface of the paper 300 from the first reading means 1.

FIG. 5 shows the configuration of the data transfer means 6 of the image scanner 100. In FIG. 5, the data transfer means 6 includes a front buffer control unit 61, a back buffer control unit 63, and D.
It includes an MA control unit 65, an image memory 66, an interface buffer control unit 67, and a transfer speed timer 69. The front buffer control unit 61, the back buffer control unit 63, and the interface buffer control unit 67 each include a front write buffer register 62, a back write buffer register 64, and a read buffer register 68.

The table buffer control unit 61 comprises the signal processing means 5
Paper 300 of the optimized image data input from
The image data (table image data) of the surface of the is temporarily stored in the table write buffer register 62. That is, buffering is performed. The back buffer control unit 63 temporarily stores the image data of the back surface of the paper 300 (back image data) in the optimized image data in the back writing buffer register 64. The front write buffer register 62 and the back write buffer register 64 constitute a write buffer register. The front image data and the back image data are 8-bit parallel data. That is, image data of 8 bits per pixel or 8 pixels is input from the signal processing means 5 for each byte.

The table buffer control unit 61 stores the table image data in the table write buffer register 62 and then D
A request for writing table image data to the image memory 66 (table writing request) is sent to the MA control unit 65. In response to this, the DMA control unit 65 sends (returns) the write permission (table write response) of the table image data to the table buffer control unit 61. Upon receiving the table write response, the table buffer control unit 61 forms an address signal (table write address) for the write, and outputs D together with the table image data to be written (table write data).
It is sent to the MA control unit 65. Since this data transfer is a DMA transfer, the microprocessor 8 is not involved in this data transfer.

The back buffer control unit 63 also performs the same processing as the front buffer control unit 61. That is, the back buffer control unit 63
Writes the back image data to the back write buffer register 6
After storing the data in No. 4, the write request (back write request) to the image memory 66 is sent to the DMA control unit 65. In response to this, the DMA control unit 65 returns the write permission (back write response) to the back buffer control unit 63. Upon receiving this, the back buffer control unit 63 forms an address signal (back writing address) for the writing, and sends it to the DMA control unit 65 together with the back image data to be written (back writing data).

The front write address and the back write address are each a 26-bit signal, for example.
The front write data and the back write data are each 32 bits, for example. That is, in the data transfer between the front buffer control unit 61, the back buffer control unit 63, and the DMA control unit 65, image data (image data block) for four pixels are collectively transferred at one time. These values depend on the configuration of the image memory 66.

The DMA controller 65 is a table buffer controller 6
When receiving the table write address and the table write data from 1, the table write data is written to the table write address of the image memory 66. Similarly, when receiving the back write address and the back write data from the back buffer control unit 63, the DMA control unit 65 writes the back write data to the back write address of the image memory 66.

The interface buffer controller 67 sends a read request (IF read request) for the image data stored in the image memory 66 at a predetermined timing.
It is sent to the MA control unit 65. In response to this, the DMA control unit 65 returns the read permission (IF read response) of the image data to the interface buffer control unit 67. I
The interface buffer control unit 67 that has received the F read response receives the address signal (IF
A read address) is formed and sent to the DMA control unit 65. The DMA control unit 65 that has received the IF read address reads the image data (IF read data) at the IF read address of the image memory 66, and transfers this to the interface buffer control unit 67. Since this data transfer is a DMA transfer, the microprocessor 8 is not involved in this data transfer.

The IF read address is, for example, 26.
It is a bit signal. Further, the IF read data is, for example, 32 bits. That is, the data transfer between the interface buffer control unit 67 and the DMA control unit 65 is the same as the data transfer between the front buffer control unit 61 and the back buffer control unit 63 and the DMA control unit 65. The image data blocks of are collectively transferred at one time.

FIG. 6 shows writing and reading of image data in the image memory 66 described above.
This writing / reading is done by D so as not to collide with each other.
Mediation control is performed by the MA control unit 65. Further, the image memory 66 is arbitrarily divided into two, and the first half portion 661 and the second half portion 662 thereof are used for writing / reading the front writing data and the back writing data, respectively.

In the ADF mode, the first sheet 30
When 0 is fed, the writing of the table write data is started, and the first half 661 is sequentially written from the beginning. At some point after this, as shown in FIG. 6A, the writing of the table write data advances to a predetermined position of the first half portion 661,
Writing of back writing data is started, and the latter half 662
Are written in order from the beginning of. At the same time, the reading of the table write data is started, and the front half portion 661 is sequentially read from the beginning. Reading of the table write data is performed following the table write process while confirming that the write has been performed using the table write address. The same applies to the following.

Next, as shown in FIG. 6 (B), the writing of the table writing data proceeds to the end of the first half portion 661 and ends, and the reading of the table writing data proceeds to a predetermined position of the first half portion 661, The writing of the back writing data proceeds to a predetermined position of the latter half 662.

Next, when the reading of the first sheet 300 is completed, the second sheet 300 is continuously fed. As a result, as shown in FIG. 6C, the writing of the table writing data is started, and the writing is sequentially performed from the beginning of the first half portion 661. At this time, the writing of the back writing data proceeds to a predetermined position of the latter half portion 662, the reading of the back writing data is started, and the latter half portion 662 is sequentially read from the beginning.

Next, as shown in FIG. 6D, the writing of the front writing data proceeds to a predetermined position of the first half portion 661, the writing of the back writing data proceeds to the end of the second half portion 662, and ends. The reading of the back writing data proceeds to a predetermined position in the latter half 662.

By using the image memory 66 as described above, the image memory 66 is shared on the front and back sides, and the resource efficiency thereof is improved. In addition, by using this together with the DMA transfer for every multiple bytes (4 bytes),
Further, the occupation efficiency (access frequency) of the image memory 66 is improved. Then, DMA transfer is performed for every plural bytes, and buffer registers (62, 64, 68) are provided in the front and rear stages (described later) of the image memory 66 to improve the occupation rate and resource efficiency of the image memory 66. In addition, the data transfer speed of the image data can be set independently of the reading speed of the image data by the line sensor 11 or the like. That is, the data transfer rate of image data is variable.

That is, according to the present invention, based on the drive frequency (for example, 6 MHz) of the line sensor or the like, for example, 6 /
The data transfer clock (that is, data transfer rate) of the conventional image scanner, which is fixed at 8 MHz (1 byte per 8 pixels), can be independently set. Here, in general, the hardware configuring the data transfer means 6 and the host computer 200 is capable of clock operation at a frequency higher than 6/8 MHz. Therefore, the upper limit of the data transfer rate is not determined depending on the drive frequency of the line sensor or the like, but is determined by the upper limit of the range guaranteed by the hardware. As a result, in the double-sided reading mode, image data having the same data amount as when the driving frequency of the line sensor or the like is artificially doubled to 12 MHz can be obtained, but at a higher speed (for example, twice as much as the conventional one). Data can be transferred (at a speed of 12/8 MHz).

The buffer registers (62, 64) in the preceding stage of the image memory 66 are accessed mainly in units of a plurality of bytes to increase the speed of reading image data and the speed of data processing thereof. Contribute. This memory access is performed with the highest priority. The buffer register (68) in the latter stage of the image memory 66, which will be described later, accesses the data in units of a plurality of bytes, so that the data transfer on the interface is not mainly affected by the access to the image memory 66. Contributes to faster transfer.

In the single-sided reading mode, writing / reading of image data is performed in the same manner as described above using only the first half portion 661 of the image memory 66. Therefore, also in this case, the data transfer speed of the image data is variable, and the speed of data transfer can be increased.

The interface buffer control unit 67 uses the D
The image data block (IF read data) transferred from the MA control unit 65 is temporarily stored in the read buffer register 68. That is, buffering is performed. After that, the interface buffer control unit 67
The IF read data stored in the read buffer register 68 is sequentially read from the beginning thereof in synchronization with the transfer request signal transmitted from the transfer speed timer 69 at a predetermined timing, and the data is transferred to the host computer 200 as interface data.

The interface data is, for example, 8-bit parallel data for one pixel or eight pixels. Therefore, the interface buffer control unit 67 temporarily stores the 32-bit image data block read from the image memory 66 in the read buffer register 68, sequentially sends out 8 bits from the beginning on the interface, and transfers the data to the host computer 200. To do. That is, the reading of the image data from the image memory 66 is a prior advance reading (prefetch) of the image data to be transferred.

The transfer speed timer 69 forms a transfer request signal based on the data transfer speed designated by the microprocessor 8 in response to a predetermined instruction input from the outside of the image scanner 100 by the operator as described above.
The transfer request signal is formed according to a designated speed from the microprocessor 8, for example, by a well-known clock generation circuit (not shown) included in the transfer speed timer 69. Also,
For example, it may be formed by dividing the system clock by a known dividing circuit.

For example, in the single-sided reading mode,
6 according to the operator's speed designation of 6/8 MHz
A transfer request signal having a frequency of / 8 MHz is formed. Note that if specified in this way, in the single-sided reading mode, the image scanner 100 of the present invention can be connected to the host computer 200 without any change (in addition to the interface). In double-sided scanning mode,
According to the operator's speed designation of 12/8 MHz,
A transfer request signal with a frequency of 12/8 MHz is formed.
Thus, in the double-sided reading mode, it is possible to set the first speed of data transfer so that the paper is continuously supplied by the paper supply unit without changing the interface.

The interface buffer controller 67 transfers the image data based on the transfer request signal in accordance with a predetermined interface shown in FIG. In particular, FIG. 7A shows data transfer in the double-sided reading mode, and FIG. 7B shows data transfer in the single-sided reading mode.

As can be seen from FIGS. 7A and 7B, this image data connection (transfer) interface is common to the double-sided reading mode and the single-sided reading mode. As shown in FIGS. 7A and 7B, this interface uses a vertical valid signal (V gate signal) and a horizontal valid signal (H
Gate signal), a data transfer clock (V clock), and a data signal (V data) to be transmitted. Therefore, the image scanner 100 also sends the data transfer clock to the host computer 200. The data transfer clock is substantially equal to the transfer request signal.

The vertical valid signal indicates a page break.
For example, one page of image data in which the vertical effective signal is at a high level (ON or 1) is being sent,
When the level is low (OFF or 0), it indicates a page break. The horizontal effective signal indicates a division of one line (one line). For example, when the horizontal effective signal is at the high level, one line of image data is transmitted, and when the horizontal effective signal is at the low level, it indicates a division of one line. A high level of a plurality of predetermined horizontal valid signals (for the number of lines in one page) is included during the period when the vertical valid signal is at the high level. A plurality of predetermined data signals (for the number of pixels in one line) are included while the horizontal effective signal is at the high level. The data signal is, for example, an 8-bit parallel signal for one pixel or eight pixels.

The data signal is transferred in synchronization with the data transfer clock. Further, the number of horizontal valid signals included in the period in which the vertical valid signal is high level and the number of data transfer clocks included in the period in which the horizontal valid signal is high level are predetermined. Therefore, the high level period of the vertical valid signal and the horizontal valid signal is determined by the operator's designation of the data transfer rate (frequency of the transfer request signal) via the microprocessor 8.

For example, as shown in FIG. 7A, in the double-sided reading mode, the operator 12/8 MHz
A data transfer clock of 12/8 MHz is formed according to the speed designation. Further, in the single-sided reading mode, as shown in FIG.
A data transfer clock of 6/8 MHz is formed according to the speed designation of MHz. As a result, as can be seen from the comparison between FIGS. 7A and 7B, the high level period of the vertical effective signal and the horizontal effective signal in the double-sided reading mode is changed to the vertical effective signal and the horizontal effective signal in the single-sided reading mode. Is set to 1/2 of the high level period. As a result, in the double-sided reading mode, the host computer 2 can transfer twice the image data per unit time in the same transfer time as the conventional one.
00 can be transferred. Therefore, in the double-sided reading mode, the first speed of data transfer can be set so that the paper is continuously supplied by the paper supply means without changing the interface.

FIG. 8 shows the timing of data transfer of image data. As shown in FIG. 8, the first sheet 300
When the paper feeding is started, the image data (table) of the front surface of the first sheet 300 is obtained at a timing delayed by a predetermined time. The image data (back) of the back surface of the first sheet 300 is obtained at a timing delayed by a predetermined time from the start of forming the front image data. At a predetermined timing after the formation of the back image data, the feeding of the first sheet 300 is completed (the ejection is completed). Therefore, when the feeding of the second sheet 300 is started, the front and back image data are obtained at the same timing as in the case of the first sheet.

Here, as described above, the time required to obtain the front and back image data is the same. After starting feeding the first sheet 300, the second sheet 300
Image data of four pages can be obtained in the time until the end of the paper feeding. Image scanner 100
As shown in FIG. 8, the front to back image data is continuously transferred at a high speed (at a double speed), and
The paper 300 is continuously supplied by the ADF function.

[0058]

As described above, according to the present invention,
An image scanner equipped with a double-sided reading mode that reads image data on the front and back sides of the paper, simultaneously reads the image data written on the front and back sides of the paper, and transfers the image data formed based on the image data to the host computer. By making the speed variable, the image data of the double-sided original can be input at high speed without operator intervention, so it is possible to improve the amount of input processing such as forms per unit time in the host computer, and to transfer data. Since the interface can be the same as the conventional image data transfer interface, the interface is not changed even for the host computer having the image scanner connection interface corresponding to the conventional image scanner (single-sided scanner). Can be connected, thus, it is possible while maintaining compatibility with logically and physically and conventional image data interface, to speed up the input image data.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is an explanatory diagram of an image scanner structure.

FIG. 3 is an explanatory diagram of a structure of an image scanner.

FIG. 4 is a configuration diagram of an image scanner.

FIG. 5 is a configuration diagram of an image scanner.

FIG. 6 is an explanatory diagram of an image memory.

FIG. 7 is an explanatory diagram of data transfer.

FIG. 8 is an explanatory diagram of data transfer.

[Explanation of symbols]

1 First reading means 2 Second reading means 3 Third reading means 4 Reading control means 5 Signal processing means 6 Data transfer means 7 Paper supply means 8 microprocessors 61 table buffer controller 62 Table write buffer register 63 Back buffer control unit 64 Back write buffer register 65 DMA controller 66 image memory 67 Interface buffer controller 68 Read Buffer Register 69 Transfer rate timer 100 image scanner 200 host computer 300 sheets

Claims (5)

(57) [Claims] 1. An image scanner which is connected to a host computer and transfers data to and from a host computer according to a predetermined interface, the first reading means for a double-sided reading mode for reading image data on a front surface of a sheet. And a second reading means for double-sided reading mode for reading image data on the back side of the sheet, and a third reading for single-sided reading mode for reading the image data on the front side of the sheet at a position different from that of the first reading means. Means and in the double-sided reading mode, the first and second reading means are controlled so as to simultaneously read the image data written on the front surface and the back surface of the paper, and in the single-sided reading mode, it is written on the front surface of the paper. Reading control means for controlling the third reading means to read the image data, and the first reading means. The third form of the surface and back of the image data of the sheet by performing a predetermined operation on the image data read by the reading means, and a signal processing means for writing in the image memory, the image data written in said image memory,
A data transfer means for reading at a predetermined speed and transferring data to a host computer according to the interface; in the double-sided reading mode, the first and second reading means are under the control of the reading control means; And the image data on the back side are read at the same time, and the signal processing is performed.
Means forms the image data to generate the image memo.
The image data written in the image memory according to the interface, the image data written in the image memory is transferred at a first speed, and the image transfer is performed.
When writing to and reading from the memory, the image
Image memory, which is the front side writing data that is the image data of the front side of the paper.
Image data of the front writing part to write data and the back side of the paper
The back writing unit that writes the back writing data is 2
Divide the above table writing data for the first sheet
At the time when the data is written to the predetermined position of the front writing unit
Read the data written in the table and
Start writing the back write data of all
The back writing data for the paper is the back writing
Back writing at the time when it has been written to the prescribed position of the copy
Reading of data and writing of the table for the next sheet
In the single-sided reading mode, the third reading means reads the image data on the front side of the sheet, and the data transfer means follows the interface to start the writing of the data. Image data is transferred at a second speed lower than the first speed. 2. The image scanner according to claim 1, wherein the data transfer speed can be set by an instruction input from the outside of the image scanner. 3. The reading position of the image data of the first reading unit and the reading position of the image data of the second reading unit are different from each other in the sheet feeding direction. The image scanner according to claim 1. 4. The image scanner according to claim 1, wherein the first reading unit and the third reading unit are the same reading unit. 5. The paper supply, wherein the image scanner further supplies paper by feeding the paper to the first or second reading means in a predetermined direction in a predetermined direction at a predetermined speed. 2. The image according to claim 1, further comprising means, wherein the first speed of data transfer can be set such that the paper is continuously supplied by the paper supply means in the double-sided reading mode. Scanner.