JPH08340421A - Image reading device - Google Patents

Abstract

(57) [Abstract] [Purpose] An image reading device that does not reduce the data transfer rate to external devices, and that effectively uses the buffer memory to minimize the number of image joints during a restart reading operation. The purpose is to provide. In an image reading apparatus that relatively moves a document and an optical system in a sub-scanning direction, a buffer memory 21 that temporarily stores the read image data and an interface controller 23 that transfers the data to an external device are provided. A transfer time measuring timer 37 for measuring the data transfer rate to the device is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image input device such as a scanner or a copying machine having a reading position adjusting function.

[0002]

2. Description of the Related Art In recent years, workstations, personal computers, and the like have been made highly functional, and full-color image editing, character input by electronic filing, OCR, etc., can be processed at high speed. Along with this, a flat bed type image scanner device capable of easily inputting an image is becoming widespread. However, as the image reading accuracy is improved and the image reading speed is increased, cooperation with an external device is improved. It becomes a problem. In particular, when the image reading speed of the image scanner device is higher than the data transfer speed with the external device, it is necessary to cooperate with each other by some means. In such a case, it is effective and easy to temporarily store the data for one image in the buffer memory and send it according to the processing speed of the external device.
Since the amount of image data becomes enormous as the resolution becomes higher and the color becomes higher, it is not a good idea to mount a buffer memory for one image because the burden on the cost is large.

Therefore, it is general to add a function of temporarily stopping the reading operation on the way. When the buffer memory is full of read data in a device with such a halfway stop function, the read operation is temporarily suspended and only data transfer to an external device is performed until the data in the buffer memory is discharged to some extent. It will be in a standby state.

In the prior art, a method of restarting the reading after the data in the buffer memory is completely transferred to the external device (conventional example 1), and before the data in the buffer memory is completely transferred to the external device. There is a method (conventional example 2) for restarting the accumulation of read data in the buffer memory.

A conventional image reading apparatus will be described below with reference to the drawings. FIG. 9 is a schematic diagram of a conventional image reading apparatus. In FIG. 9, 1 is an image reading apparatus main body. Reference numeral 2 is a document glass on which a document is set, and 3 is a carriage for scanning and reading the document.
Reference numeral 4 is a support member having a bearing and the like inside and is mounted on the carriage 3. Reference numeral 5 denotes a shaft that supports the carriage 3 via the support member 4, and the shaft 5 regulates the carriage 3 so that the carriage 3 can move only in the sub-scanning direction. 6 is a drive wire for transmitting the driving force to the carriage 3, 7 is a drive pulley, 8 is a driven pulley, the drive wire 6 is connected to the carriage 3, and the drive wire 6 is connected to the drive pulley 7 and the driven pulley 8. It has been banded. Reference numeral 9 denotes a drive motor, and the drive pulley 7 is a drive motor 9 formed by a connecting shaft and a reduction mechanism (both not shown).
The carriage 3 is driven by rotating the drive motor 9. Reference numeral 10 is a driven pulley supporting member, 11 is a biasing means, and the driven pulley 8 is a driven pulley supporting member 10.
The drive wire 6 is biased by the biasing means 11 via the. Reference numeral 12 is a document cover for bringing the document into close contact with the document glass 2.

FIG. 10 is a schematic diagram of a conventional optical system. In FIG. 10, 13 is a light source lamp for illuminating an original, and 14 is a light source lamp.
Is an aperture for narrowing the reading line width in the sub-scanning direction of the document reading section provided on the carriage 3. Reference numeral 15 is a reflection mirror that reflects the reflected light from the document, 16 is a color image sensor that converts optical information into an electric signal, and 17 is an imaging lens that forms an image on the color image sensor 16.

FIG. 11 is an explanatory view of buffer management at the time of restart reading operation in the conventional image reading apparatus. In the conventional method of restarting the reading after the data in the buffer memory is completely transferred to the external device,
The relationship between the elapsed time and the input / output data amount in the buffer memory is shown. In FIG. 11, the horizontal axis represents time, the vertical axis represents the input / output data amount in the buffer memory, the solid line graph represents the input data amount to the buffer memory, and the broken line graph represents the output data amount from the buffer memory. The data transfer rate to the external device is slower than the accumulation of the read data in the buffer memory. In addition, the data transfer speed to the external device actually changes with time depending on the reception status on the external device side, but is expressed as a constant speed for convenience.

The operation of the image reading apparatus configured as described above will be described below.

When a command to read a document is issued from an external device (not shown) with the above-described configuration, the CPU causes the light source lamp 13 to operate.
Is turned on and the drive motor 9 is rotated to drive the carriage 3 connected by the drive pulley 7 and the drive wire 6 at a constant speed. Further, the image sensor drive circuit (not shown) starts the reading operation of the image sensor 16. The original is the light source lamp 1 through the glass window 2b.
The light reflected by the document is emitted by the aperture 14
As a result, the reading line width in the sub-scanning direction is narrowed and the light enters the carriage 3. The reflected light from the original that has entered is reflected by the reflection mirror 15, is imaged on the color image sensor 16 by the imaging lens 17, and is converted into an electric signal. The carriage 3 starts writing the read data on the buffer memory together with the reading start command from the CPU. With that, the data in the buffer memory is asynchronously started to be transferred to the external device.

In FIG. 11, first, read data is accumulated in the buffer memory, and at time A, the amount of accumulated data in the buffer memory becomes the maximum value. At this time, the reading operation is suspended and only data transfer to the external device is performed. In order for the carriage 3 to resume reading again at the same speed at the reading interruption point, it is necessary to return the carriage 3 in the opposite direction to the reading interruption point in order to secure a certain approach distance. After that, at time B when the data in the buffer memory is completely discharged, the CPU
A command for restarting reading is issued, and after the carriage 3 again passes through the reading point again at the reading speed, the accumulation of the read data in the buffer memory is restarted at time C. The above series of operations will be referred to as buffer overrun processing. The time from point B to point C is the time for the read data to be actually resumed to be stored in the buffer memory from the reread command, and is hereinafter referred to as restart delay, which is represented by Td in the figure. During this Td, since the buffer memory is empty, the data transfer to the external device is interrupted.
When the storage of the data in the buffer memory is restarted at the point of C, the data transfer to the external device is also restarted. next,
At the time of D, a buffer overrun occurred, and at the time of E, when the data in the buffer memory was completely discharged, CP
U issues a command to start the restart reading operation, and at the point of F, data accumulation restarts in the buffer memory. The above process is repeated to transfer the read data to the external device. However, in this method, the data transfer to the external device is interrupted by the restart delay Td, and the transfer efficiency is reduced.

In order to solve the above-mentioned decrease in transfer efficiency, conventionally, there is a method (conventional example 2) for restarting the accumulation of read data in the buffer memory before the data in the buffer memory is completely transferred to the external device. is there.

The second conventional example will be described below with reference to the drawings. Since the basic configuration is the same as that of the conventional example 1, the description thereof is omitted.

FIG. 12 is a conceptual diagram showing a data storage state in a buffer memory in a conventional image reading apparatus. As shown in FIG. 12, while the read data is accumulated in the buffer memory, the already accumulated data is transferred to the external device. Here, the data storage amount X in FIG. 12 is a threshold when reading of an image is restarted.

FIG. 13 is an explanatory diagram of buffer management at the time of a restart reading operation in the conventional image reading apparatus. Before the data in the buffer memory is completely transferred to the external device, the data is accumulated in the buffer memory. In the conventional method of resuming, the relationship between the elapsed time and the amount of input / output data in the buffer memory is shown. In FIG. 13, the horizontal axis represents time, the vertical axis represents the input / output data amount of the buffer memory, the solid line graph represents the input data amount to the buffer memory, and the broken line graph represents the output data amount from the buffer memory. Note that the data transfer rate to the external device is slower than writing the read data to the buffer memory. In addition, the data transfer speed to the external device actually changes with time depending on the reception status on the external device side, but is expressed as a constant speed for convenience.

The operation of the second conventional image reading apparatus configured as described above will be described below.

When an original reading command is issued from an external device (not shown) as in the first conventional example, the CPU turns on the light source lamp 13 and rotates the drive motor 9 to drive the drive pulley 7 and the drive wire 6. Carriage 3 connected by
Drive at a constant speed. Further, the image sensor drive circuit (not shown) starts the reading operation of the image sensor 16. The original is the light source lamp 1 through the glass window 2b.
The light reflected by the document is emitted by the aperture 14
As a result, the reading line width in the sub-scanning direction is narrowed and the light enters the carriage 3. The reflected light from the original that has entered is reflected by the reflection mirror 15, is imaged on the color image sensor 16 by the imaging lens 17, and is converted into an electric signal. The carriage 3 starts writing the read data on the buffer memory together with the reading start command from the CPU. With that, the data in the buffer memory is asynchronously started to be transferred to the external device.

In FIG. 13, first, when the read data is stored in the buffer memory at A, the data storage amount in the buffer memory becomes the maximum value and a buffer overrun occurs. After the buffer overrun occurs, the reading operation is suspended and only the data transfer to the external device is performed.
In order for the carriage 3 to resume reading at the same speed at the reading interruption point, in order to secure a certain approach distance,
It is necessary to return the carriage 3 to the reading interruption point in the opposite direction to the reading direction. After that, when the data storage amount in the buffer memory becomes B, the CPU issues a command to start rereading, the carriage 3 passes again to the rereading point at the reading speed, and then the read data is stored in the buffer memory. Is resumed. That time is C,
From the time point B to the time point C, the restart delay is the same as in the conventional example 1. However, the data remains in the buffer memory even at the time point C, and the data transfer to the external device is continued. When the writing of data to the buffer memory is restarted at the point of C,
Data is accumulated in the buffer memory again. next,
A buffer overrun occurs at time D, a restart read operation start command is issued at time E, and the data is accumulated in the buffer memory at time F. It will be restarted. By repeating the above, the read data is transferred to the external device without interruption of the data transfer to the external device.

[0018]

However, in the first conventional example, as compared with the case where the data transfer to the external device shown by the alternate long and short dash line in FIG. 11 is not stopped, the data transfer is performed by the restart delay Td. However, there is a problem that the total throughput is reduced.

Further, in the second conventional example, since the read data storage in the buffer memory is restarted before the data in the buffer memory is completely transferred to the external device, the data transfer is not interrupted, but the buffer is not interrupted. Since the memory capacity of the memory cannot be used efficiently and the number of restart reading operations increases, the number of connected portions of read images increases and the image quality deteriorates.

Therefore, according to the present invention, in an image reading apparatus having a buffer memory, the buffer connection can be effectively used without reducing the data transfer speed to an external device and the image connecting portion at the time of the restart reading operation. It is an object of the present invention to provide an image reading device that minimizes the number of devices.

[0021]

According to the present invention, there is provided means for measuring a transfer speed at which data accumulated in a buffer memory is transferred to an external device when the data is transferred from the buffer memory to the external device. The timing for stopping and restarting the movement of the optical system is given depending on the data storage amount and the transfer speed.

As a second means, when transferring data from the buffer memory to the external device, means for measuring the transfer speed at which the accumulated data in the buffer memory is transferred to the external device, and restarting the movement of the optical system. A means for measuring the restart reading operation time from the start of the reading operation until the storage of the data in the buffer memory is restarted is provided, and the optical reading is performed according to the data storage amount and transfer speed in the buffer memory and the restart reading operation time. Give the timing to stop and restart the system movement.

As a third means, the restart data transfer amount from the buffer memory to the external device from the start of the restart reading operation of the movement of the optical system to the restart of the accumulation of data in the buffer memory. Is provided with a means for measuring
At the time of restart, the timing of stopping and restarting the movement of the optical system is given according to the data transfer amount.

[0024]

[Advantage] With the above structure, when the buffer memory is emptied by the data transfer to the external device, the read data is resumed to be stored, and the buffer memory is enabled without reducing the transfer speed to the external device. Used for
It is possible to minimize the number of image connecting portions during the restart reading operation.

Further, according to the second configuration, there is no need for means for storing beforehand the moving speed information of the carriage according to the required resolution from the external equipment side, and the carriage movement due to the load torque fluctuation of the driving means. The restart reading operation does not depend on the change in the restart reading operation time due to the speed change, and after the second restart reading operation, the transfer speed to the external device is not reduced, and the number of image joints can be minimized. it can.

Further, according to the third configuration, a means for measuring a time for transferring a predetermined amount of accumulated data in the buffer memory to an external device and a restart reading until the accumulation of data in the buffer memory is restarted. With a simple configuration without the need to measure the operation time, after the second restart reading operation, the transfer speed to the external device is not reduced,
It is possible to minimize the number of connecting portions of images.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of an image reading apparatus main body according to the first embodiment of the present invention, and FIG. 2 is a schematic diagram of an optical system of the image reading apparatus according to the first embodiment of the present invention. The description is omitted because it is the same as the conventional example.

FIG. 3 is a block diagram of an electric system of the image reading apparatus in the first embodiment of the present invention. In FIG.
Reference numeral 16 is a color image sensor, 18 is an amplifier for amplifying the output from the color image sensor 16, and 19 is an A / D converter for converting the amplified analog output to digital. Reference numeral 20 denotes a shading correction circuit that performs normalization correction to obtain a uniform output for a document having a uniform density.
Reference numeral 4 is an MTF correction circuit for emphasizing edges or smoothing for noise removal, 35 is an enlargement / reduction circuit for enlarging / reducing a read image, and 36 is a standard color space for image data output to an external device. This is a color correction circuit for performing color conversion to.
Reference numeral 21 is a buffer memory. 22 is a buffer memory 2
1 is a DMA controller for directly controlling high-speed data transfer to the external device (not shown) via the CPU 27. An interface controller 23 controls data transfer with an external device (not shown),
Reference numeral 26 is a write counter of the buffer memory 21 that increases by the number of data when the image data is written in the buffer memory 21. Reference numeral 39 is an output counter of the buffer memory 21 which increases by the number of data when it is transferred to an external device. Reference numeral 40 is a storage counter that indicates the storage amount of the buffer memory that increases with the increase of the write counter 26 and decreases with the increase of the output counter 39. 37 is C
A transfer time measuring timer that can be started or stopped by the PU 27, and 24 is a color image sensor 16
In the driver circuit for driving, a line synchronization signal 32 for each sub-scanning position line and a pixel clock 33 for each pixel are generated from the reference clock signal from the crystal oscillator 25 to the color image sensor 16.

Reference numeral 29 is a D / A converter for converting the digital value output by the CPU 27 into an analog level, which controls the motor driver 30 to change the rotation direction and rotation speed of the drive motor 9. A motor encoder 31 generates two-phase pulses in accordance with the rotation of the drive motor 9. The pulse is counted by a counter built in the CPU 27 and processed as a value of the sub-scan absolute position for reading. Only one phase of the two-phase motor encoder pulse is divided by the prescaler 28 into a power value specified by the CPU 27, and the CPU 2 is compared with the reference clock by comparison.
It is converted into speed information by 7. The rotation speed of the drive motor 9 can be controlled by comparing the speed information with the target speed and changing the digital output to the D / A converter 29.

The operation of the image reading apparatus configured as described above will be described below with reference to FIGS. 1, 2 and 3.

An original is placed on the original glass 2 and an original cover 12 is provided.
When a document reading command is issued from an external device (not shown) in the closed state, the CPU 27 turns on the light source lamp 13 and controls the motor driver 30 to rotate the drive motor 9 to drive the drive pulley. The carriage 3 connected by the drive wire 6 and the drive wire 6 is driven in the sub-scanning reading direction at the reading start position at a constant speed determined by the designated reading resolution. Further, the image sensor drive circuit 24 starts the reading operation of the color image sensor 16. The original is illuminated by the light source lamp 13 through the glass window 2b, and the reflected light from the original is narrowed by the aperture 14 in the reading line width in the sub-scanning direction and enters the carriage 3. The reflected light from the entered document is reflected by the reflection mirror 1.
It is reflected by 5, and is imaged on the color image sensor 16 by the imaging lens 17 and converted into an electric signal. Next, the conversion into electric signals will be described. The crystal oscillator 25, which is a reference clock, is converted into a line synchronization signal 32 and a pixel clock 33 by the color image sensor drive circuit 24. The cycle of the line synchronization signal 32 is set as the charge storage time, and the charges stored in the charge storage section of the color image sensor 16 are shifted to the charge transfer section and are sequentially transferred in the charge transfer section at the next cycle to form one line. Is reading the image data of. The data of one line is simultaneously transferred to each of the RGB as an electric signal for each pixel by the pixel clock 33. The signal output from the color image sensor 16 is amplified by the amplifier 18,
It is converted into digital data by the / D converter 19.
After that, with respect to a document having a uniform density, the shading correction circuit 20 normalizes the document so as to obtain a uniform output, and image data is obtained. The image data is the MTF correction circuit 34.
The edge is emphasized in the case of characters / line drawings, and is output as it is in the case of photographs / natural images. Thereafter, the image data is enlarged / reduced by the enlargement / reduction circuit 35 so as to have the image size requested by the external device. The scaled image data is color-converted by the color correction circuit 36 into image data in a standard color space. According to the write permission of the CPU 27, only the data requested to be transferred to the external device is used for the obtained image data. The write counter 26 of the buffer memory 21.
The count value is added to the buffer memory 21 while being added. Asynchronously with this operation, the DMA controller 22 transfers the data taken in the buffer memory 21 to an external device (not shown) via the interface controller 23. At that time, the count value of the output counter 39 of the buffer memory 21 is incremented by the number of transfer data. The count values of the write counter 26 and the output counter 39 are the transfer time measurement timer 3
It can be read periodically by the timer interrupt of 7. In addition, the accumulation counter 40 has a write counter 2
The data storage amount of the buffer memory 21 obtained by subtracting the value of the output counter 39 from the value of 6 is counted and can be read by the CPU 27. The drive motor 9 is the CPU 27
The output value of 8-bit digital data is converted into an analog output by the D / A converter, and the motor driver 30
It becomes a current value and rotates. At that time, two-phase pulses are generated by the motor encoder 31 as the drive motor 9 rotates. The pulse is counted by a counter built in the CPU 27 and processed as a value of the sub-scan absolute position for reading. Further, of the two-phase motor encoder pulses, only one phase is divided by the prescaler 28 into a power value designated by the CPU 27, and converted by the CPU 27 into speed information. By comparing the speed information with the target speed and changing the digital output to the D / A converter 29, the rotational speed of the drive motor 9, that is, the sub-scanning moving speed of the carriage 3 can be controlled.

In the image reading apparatus which operates as described above, the buffer management in the restart reading operation when the data storage amount of the buffer memory 21, which is the point of the present invention, becomes the maximum value, that is, when the buffer overrun occurs is illustrated. Will be described with reference to.

FIG. 4 is a diagram showing the relationship between the elapsed time and the amount of input / output data in the buffer memory during the restart reading operation in the first embodiment of the present invention. 4, the horizontal axis represents time, the vertical axis represents the input / output data amount of the buffer memory 21, the solid line graph represents the input data amount to the buffer memory 21, and the broken line graph represents the output data amount from the buffer memory 21. ing. Note that the data transfer rate to the external device is slower than writing the read data to the buffer memory 21. In addition, the data transfer speed to the external device actually changes with time depending on the reception status on the external device side, but is expressed as a constant speed for convenience.

First, the transfer time measuring timer 37 is started at the same time when the data transfer to the external device is started, and the transfer time measuring timer 37 is interrupted at a certain fixed period (for example, 10 msec here). The count value of the write counter 26 of the buffer memory 21 is stored. In this case, when the count value of the write counter 26 is increased by 10000, the data transfer rate to the external device is (10000/10 msec =) 1 Mby.
This means a transfer rate of te / sec. This value is calculated in real time and is registered in the CPU 27 register (not shown).
Hold that value in. Further, the restart delay from when the restart reading operation start command is issued from the CPU 27 until the reading data is actually stored in the buffer memory 21 is unique to the machine, and the sub-scanning direction of the carriage 3 that changes depending on the reading resolution. It is assumed that the time is 100 msec, for example, based on the time data stored in advance for each reading resolution, which is determined by the moving speed and the like. A value of 1 obtained by multiplying this restart delay of 100 msec and the data transfer rate of 1 Mbyte / sec to the external device.
When the data storage amount of the buffer memory 21 (that is, the value of the storage counter 40) becomes 00 kbyte (represented by X in FIG. 4), it is the timing to issue the restart reading operation start command. As a result, after the buffer overrun occurs at the time point A in FIG. 4, the motor 9 is controlled to decelerate, the carriage 3 is stopped, and the motor 9 is reversely rotated.
The carriage 3 again accelerates to the reading speed in the sub-scanning reading direction, and returns the carriage 3 in the reverse direction by a distance including the approach distance for passing the rereading point at a constant speed. After that, at B when the accumulation counter 40 becomes 100 kbyte, the CPU drives the motor 9 and issues a command to start the restart reading operation. The carriage 3 is accelerated to the reading speed in the sub-scanning reading direction to a uniform speed, and passes through the rereading point. The read data from the rereading point restarts to be accumulated in the buffer memory 21. The buffer memory 2 at which the accumulation restart point in the buffer memory 21 is the time point C and the accumulation counter 40 is just 0
It becomes equal to that when the data storage amount of 1 becomes empty. Similarly, when the buffer overrun occurs at the time of D and the value of the storage counter 40 becomes 100 kbytes at the time of E, the value of the storage counter 40 is exactly changed by issuing the restart reading operation start command. At the time F when the data storage amount of the buffer memory 21 becomes 0, the storage of the read data in the buffer memory 21 is restarted.

As described above, when the buffer overrun occurs, the image is read by repeating the restart reading operation.

Next, the second embodiment will be described. First
In the second embodiment, the restart delay time needs to be stored in advance, whereas in the second embodiment, by measuring the restart delay time, the moving speed of the carriage due to the load torque fluctuation of the driving means. Even when the restart reading operation time changes, the image reading to the buffer memory 21 is restarted when the data in the buffer memory 21 becomes empty just after the second restart reading operation. This point will be described below.

FIG. 5 is an electric system block diagram of an image reading apparatus according to the second embodiment of the present invention. This is the first
In the electrical system block diagram (FIG. 3) in the embodiment of FIG.
A restart reading operation measurement timer 38 that can be started or stopped by 27 is added, and the time from the restart reading operation start command until the write counter 26 of the buffer memory 21 starts to increase again is measured.

FIG. 6 is a diagram showing the relationship between the elapsed time and the input / output data amount in the buffer memory during the restart reading operation in the second embodiment of the present invention.

In FIG. 6, the horizontal axis represents time, the vertical axis represents the input / output data amount of the buffer memory 21, the solid line graph represents the input data amount to the buffer memory, and the broken line graph represents the output data amount from the buffer memory. Is shown. In addition,
It is assumed that the data transfer rate to the external device is slower than the read data writing to the buffer memory 21. Also,
Actually, the data transfer rate to the external device changes with time depending on the reception status on the external device side, but is expressed as a constant rate for convenience.

The operation of the second embodiment of the present invention will be described below with reference to FIG.
Will be described with reference to. In this operation, in the first restart reading operation, the timing of the restart reading operation start command is set to a threshold value with a margin in the data accumulation amount of the buffer memory 21 so that the data accumulation amount of the buffer memory 21 does not become empty. To do. First, at the time of A, a buffer overrun occurs and the data transfer to the external device is not interrupted. At the time of B when there is a sufficient amount of data storage in the buffer memory 21, the restart read operation start command is issued. Give out. After that, the read counter 26 where the read data actually resumes being accumulated in the buffer memory 21 again
The restart delay time up to the point C until the start of
Measure with. When the value obtained by multiplying the restart delay time and the data transfer rate to the external device described in the first embodiment becomes the next value of the storage counter 40, that is, the data storage amount of the buffer memory 21, the system is restarted. By issuing the command to start the reading operation, in the second and subsequent restart reading operations, the reading data storage is resumed when the data storage amount in the buffer memory 21 where the value of the storage counter 40 becomes 0 becomes empty. It For example, the data transfer rate obtained up to the point A is 1 Mbyte / sec,
The restart delay Td measured between B and C is 90.
If it is msec, the value of the accumulation counter 40 of the buffer memory 21 which determines the command timing of the operation start at the time of the next restart reading operation becomes the time when it becomes 90 kbyte which is obtained by multiplying 1 Mbyte / sec by 90 msec. That is, a buffer overrun occurs at the time of D, and the value of the accumulation counter 40 becomes 90 kbyte at the time of E.
When it becomes (represented by X in FIG. 6), a command to start the restart reading operation is issued, so that the accumulation counter 4 just
At the point of F when the data storage amount of the buffer memory 21 becomes 0 when 0 becomes empty, the storage of the read data in the buffer memory 21 is restarted.

As described above, when the buffer overrun occurs, the restart reading operation is repeated to read the image.

As a third embodiment, the difference between the data storage amount of the buffer memory 21 at the time when the restart reading operation start command is issued and when the data storage is restarted at the buffer memory 21 is calculated as the next buffer memory 21. Even if the restart read operation time changes, the data in the buffer memory 21 will be emptied just after the restart read operation by changing the threshold so that the restart read operation is started. At that point, the image reading to the buffer memory 21 is restarted. This point will be described below.

FIG. 7 is a block diagram of the electric system of the image reading apparatus in the third embodiment of the present invention. This is a configuration in which the transfer time measuring timer 37 and the restart reading operation time measuring timer 38 are removed from the electric system block diagrams (FIGS. 3 and 5) in the first and second embodiments, and the buffer memory Buffer management is performed with the value of the accumulation counter 40 indicating the accumulated amount of 21.

FIG. 8 is a diagram showing the relationship between the elapsed time and the input / output data amount of the buffer memory during the restart reading operation in the third embodiment of the present invention.

In FIG. 8, the horizontal axis represents time, the vertical axis represents the input / output data amount of the buffer memory 21, the solid line graph is the input data amount to the buffer memory, and the broken line graph is the output data amount from the buffer memory. Is shown. In addition,
It is assumed that the data transfer rate to the external device is slower than the read data writing to the buffer memory 21. Also,
Actually, the data transfer rate to the external device changes with time depending on the reception status on the external device side, but is expressed as a constant rate for convenience.

The operation of the third embodiment of the present invention will be described below with reference to FIG.
Will be described with reference to. Also in this operation, similarly to the second embodiment, in the first restart reading operation, the timing of the restart reading operation start command is set to the buffer memory 21 data accumulation so that the data accumulation amount of the buffer memory 21 does not become empty. A value with a sufficient amount is used as the threshold.
First, at the time of A, a buffer overrun occurs and the data transfer to the external device is not interrupted. At the time of B when there is a sufficient amount of data storage in the buffer memory 21, the restart read operation start command is issued. Give out. The amount of data stored in the buffer memory 21, that is, the value of the storage counter 40 at the time point B is held in the register of the CPU 27. After that, at the time point C until the read data actually resumes to be stored in the buffer memory 21 again, the data storage amount of the buffer memory 21, that is, the value of the storage counter 40 is similarly captured in the register, and the difference between the two registers, That is, a value obtained by subtracting the data storage amount of the buffer memory 21 at the time of B from the data storage amount of the buffer memory 21 at the time of B is the data of the buffer memory 21 at the timing of issuing the next restart reading operation start command. By setting the accumulation amount threshold, the second and subsequent restart reading operations restart the accumulation of the read data when the accumulation amount of data in the buffer memory 21 where the accumulation counter 40 becomes 0 becomes empty. For example, the value of the storage counter 40 at the time of B is 23000h in hexadecimal (that is, the data storage amount is 140 kbytes), and the value of the storage counter 40 at the time of C is in hexadecimal is 14000h (that is, the data storage amount is 80 kbytes). If there was 140 kb
60 kbytes (hexadecimal number: F000h) from 80 kbytes subtracted from yte becomes the value of the accumulation counter 40 that determines the command timing of the operation start at the next restart reading operation. That is, when the buffer overrun occurs at the time of D and the value of the accumulation counter 40 becomes 60 kbytes (represented by X in FIG. 8) at the time of E, the restart reading operation start command is issued, and the accumulation is just performed. When the amount of data accumulated in the buffer memory 21 becomes zero when the value of the counter 40 becomes 0, the accumulation of the read data in the buffer memory 21 is restarted.

As described above, when the buffer overrun occurs, the image is read while repeating the restart reading operation.

Further, in the above embodiment, the color image sensor is used as the line sensor, but this may be a monochromatic line sensor.

Further, although the carriage moving type image reading apparatus is used in the above embodiment, it may be an image reading apparatus which moves the optical system relatively in the sub-scanning direction with respect to the original including the original moving type. Good.

Further, in the above embodiment, the timing of the buffer overrun is set to the time when the data storage amount of the buffer memory 21 reaches the maximum value, but this may be a predetermined value.

Further, in the above embodiment, the timing for giving the restart reading operation start command is set to the buffer memory 21.
Although the data accumulation amount is set to a point exactly at the calculated value, it may be increased with a margin.

[0053]

According to the present invention, the accumulation of read data is resumed when the buffer memory is emptied by the data transfer to the external device, and the buffer memory can be transferred without decreasing the transfer speed to the external device. Effectively use
It is possible to provide an image reading apparatus that minimizes the number of image connecting portions during the restart reading operation.

Further, there is no need for a means for storing in advance the carriage moving speed information according to the resolution requested from the external device side, and the restart reading operation accompanying the carriage moving speed change due to the load torque fluctuation of the driving means. Without depending on the change in time, after the second restart reading operation, the transfer speed to the external device is not reduced,
An image reading device that minimizes the number of image connecting portions can be provided.

Further, a means for measuring the time required for transferring a predetermined amount of accumulated data in the buffer memory to the external device and a means for measuring the restart reading operation time until the accumulation of data in the buffer memory is restarted are required. It is possible to provide an image reading apparatus that has a simple configuration and does not slow down the transfer speed to an external device and minimizes the number of image connecting portions after the second restart reading operation.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an image reading apparatus main body according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of an optical system of the image reading apparatus according to the first embodiment of the present invention.

FIG. 3 is a block diagram of an electric system of the image reading apparatus according to the first embodiment of the present invention.

FIG. 4 is a diagram showing the relationship between the elapsed time and the amount of input / output data in the buffer memory during the restart reading operation in the first embodiment of the present invention.

FIG. 5 is a block diagram of an electric system of an image reading apparatus according to a second embodiment of the present invention.

FIG. 6 is a diagram showing the relationship between the elapsed time and the amount of input / output data in the buffer memory during the restart reading operation in the second embodiment of the present invention.

FIG. 7 is a block diagram of an electric system of an image reading apparatus according to a third embodiment of the present invention.

FIG. 8 is a diagram showing the relationship between the elapsed time and the amount of input / output data in the buffer memory during the restart reading operation in the third embodiment of the present invention.

FIG. 9 is a schematic diagram of a conventional image reading device.

FIG. 10 is a schematic diagram of a conventional optical system.

FIG. 11 is an explanatory diagram of buffer management during a restart reading operation in a conventional image reading apparatus.

FIG. 12 is a conceptual diagram showing a data storage state in a buffer memory in a conventional image reading device.

FIG. 13 is an explanatory diagram of buffer management during a restart reading operation in a conventional image reading apparatus.

[Explanation of symbols]

 16 Color Image Sensor 18 Amplifier 19 A / D Converter 20 Shading Correction Circuit 21 Buffer Memory 22 DMA Controller 23 I / F Controller 24 Image Sensor Driving Circuit 25 Crystal Oscillator 26 Write Counter 27 CPU 28 Prescaler 29 D / A Converter 30 Motor Driver 31 Motor encoder 32 Line synchronization signal 33 Pixel clock 34 MTF correction circuit 35 Enlargement / reduction circuit 36 Color correction circuit 37 Transfer time measurement timer 39 Output counter 40 Accumulation counter

Claims (6)

[Claims] 1. A light source for illuminating a document, a line sensor for reading in the main scanning direction for each line, and an optical system capable of relative movement between the document and the document in the sub-scanning direction of the document, A driving unit that relatively moves the document and the optical system in the sub-scanning direction, a control unit that stops and restarts the movement of the optical system during reading, and temporarily stores the image data read by the line sensor. A buffer memory for transferring data to an external device, a writing / reading control unit for the buffer memory, a unit for monitoring the accumulated amount in the buffer memory, and the accumulated data in the buffer memory are transferred to the external device. And a timing for stopping and restarting the movement of the optical system according to the amount of data stored in the buffer memory and the transfer speed. Image reading apparatus characterized by the the like. 2. A light source for irradiating an original, a line sensor for reading in the main scanning direction for each line, and an optical system capable of relative movement between the original and the sub-scanning direction of the original, A driving unit that relatively moves the document and the optical system in the sub-scanning direction, a control unit that stops and restarts the movement of the optical system during reading, and temporarily stores the image data read by the line sensor. A buffer memory for transferring data to an external device, a writing / reading control unit for the buffer memory, a unit for monitoring the storage amount in the buffer memory, and the stored data in the buffer memory is transferred to the external device. Means to measure the transfer rate,
A means for measuring the restart reading operation time from the start of the restart reading operation of the movement of the optical system to the restart of the storage of the data in the buffer memory, and the storage amount of the data in the buffer memory and the An image reading apparatus, wherein a timing for stopping and restarting the movement of the optical system is given according to a transfer speed and the restart reading operation time. 3. A light source for irradiating an original, a line sensor for reading in the main scanning direction for each line, and an optical system capable of relative movement between the original in the sub-scanning direction of the original, A driving unit that relatively moves the document and the optical system in the sub-scanning direction, a control unit that stops and restarts the movement of the optical system during reading, and temporarily stores the image data read by the line sensor. A buffer memory for transferring data to an external device, a writing / reading control means for the buffer memory, a means for monitoring the amount of accumulation in the buffer memory, and a restart of the movement of the optical system from the start of the reading operation There is a means for measuring the amount of data transferred at the time of restart from the buffer memory to the external device until the accumulation of data in the buffer memory is restarted. Image reading apparatus characterized by giving more the stop of the optical system moving, the timing to restart. 4. The timing for restarting the movement of the optical system is as follows: (the amount of accumulated data) ≧ (transfer rate) × (restart of movement of the optical system) The image reading apparatus according to claim 1, wherein the image reading apparatus is at any point satisfying a condition of (restart reading operation time) until restarted. 5. The image reading apparatus according to claim 3, wherein the timing of restarting the movement of the optical system is (data storage amount) ≧ (data transfer amount at restart). 6. In the measurement of the data transfer amount at restart, (data transfer amount at restart) = (data storage amount of the buffer memory at the start of the restart reading operation) − (the data storage restart time) The image reading apparatus according to claim 3, wherein the image reading amount is calculated from a data storage amount of a buffer memory).