JPH11252318A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly accurately reproduce the phase relation of a position information signal and a line synchronizing signal at the restarting by resetting the line synchronizing signal when a read means arrives at a read restarting position, through the use of position information of one precision in rough position information and fine position information. SOLUTION: When a buffer becomes full, an image reader main body temporarily stops a picture read operation and waits for a host device to absorb image data held by a buffer 24 via an interface 25. When a CPU 26 detects that the buffer becomes full, it drives a carriage in a direction opposite to a read direction by fine quantity and it prepares for the resumption of reading. A CPU 26 periodically checks a buffer monitor signal, drives the carriage at speed corresponding to read resolution designated by a host device in the read direction, when it detects the release of a buffer full state and resumes reading from a line which is next to the line where the buffer becomes full.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus such as a scanner for reading an image from an image sensor such as a CCD.

[0002]

2. Description of the Related Art Conventionally, an image reading apparatus has been used as an image input section of a scanner, a facsimile, a copying machine, and the like.

Depending on the processing speed of the host PC, the speed of reading image data from the image sensor may be higher than the speed of transferring image data through an interface such as SCSI, so that the interface transfer is performed smoothly. In this case, the read image data must be temporarily stored in a memory (hereinafter, abbreviated as a buffer) before being transferred to the interface.

Therefore, a buffer having a capacity for storing image data for one screen which can be read by the image reading apparatus is required. However, introduction of a memory having such a capacity increases the cost, so that the demand for lowering the price is met. Will be gone. For the above reasons, it is necessary to reduce the capacity of the buffer.

At this time, when the buffer becomes full (hereinafter abbreviated as “buffer full”) with image data of the last transfer, image reading means (hereinafter abbreviated as “carriage”) equipped with an image sensor or the like is mounted. It is necessary to incorporate a mechanism in which the image reading operation is suspended and stopped until all the image data in the buffer is transferred, and then the carriage is moved to restart the reading operation. The above series of operations is called a restart.

Hereinafter, the conventional technique will be described with reference to FIG.
FIG. 6 is a diagram schematically showing a conventional image reading apparatus.
In FIG. 6, reference numeral 1 denotes an image reading apparatus main body. Reference numeral 2 denotes a document glass on which a document to be read is placed. Reference numeral 3 denotes a carriage for scanning and reading a document. The carriage 3 is supported by support members (not shown) such as a shaft and a rail, and the movement direction is restricted to one direction. A driving source 4 drives the carriage, and employs a stepping motor. 5 is a drive pulley, 6 is a timing belt, and the power generated by the drive source 4 is transmitted to the drive pulley 5 by the timing belt 6. Reference numeral 7 denotes a belt, and 8 denotes a driven pulley. The belt 7 is stretched between the driving pulley 5 and the driven pulley 8, and moves the carriage 3 in the direction d1 and in the opposite direction as the driving pulley 5 rotates. Reference numeral 9 denotes a document placed on the document glass 2, and the document 9 is read line by line by moving the carriage 3. Reference numeral 10 denotes a document cover, which is supported by a support unit 11 so as to be openable and closable. Reference numeral 12 denotes a reference data acquisition position, and a white reference plate is stuck on the document glass at this position. pol is the home position of the carriage 3,
When the image reading device is on standby, the carriage 3 is always located at the home position po1.

FIG. 7 is a view showing the internal structure of a carriage of a conventional image reading apparatus. In FIG. 7, 13 is a lamp for irradiating the original, 14 is an aperture for substantially specifying the image reading position, 15-1, 15-2, 15-
Reference numeral 3 denotes a reflection mirror that reflects light reflected from a document, 16 denotes an image sensor that converts optical information into an electric signal, and 17 denotes an imaging lens that forms an image on the image sensor 16. The image sensor 16 is fixed inside the carriage 3, and reads optical information reflected from the document 9, reduced and imaged by the reflection mirror 15 and the lens 17 in a one-to-one relationship with the document surface.

The operation of the image reading apparatus configured as described above will be described below with reference to FIGS. 6 and 7.

When the power of the apparatus is turned on, the carriage 3
Returns to the home position po1 regardless of the initial position. Thereafter, the aperture 14 moves to the reference acquisition position 12 immediately below the reference plate, turns on the lamp 13 to actually read the reference plate, determines the amplification factor for the analog signal output from the image sensor 16, and determines the black and white level. Correction (shading correction). Thereafter, it returns to the home position po1 again, and enters a standby state.

Next, the reading operation of the conventional image reading apparatus will be described. For example, an external host such as a personal computer (not shown; hereinafter simply referred to as PC)
After setting the reading resolution, reading range, etc., when an instruction to read a document is issued, the lamp 13 is turned on and the driving source 4 is rotated, and the timing belt 6, the driving pulley 5, the belt 7, the driven pulley 8, the driving force is transmitted to the carriage 3, and the carriage 3 is moved in the direction d.
Move to 1. Immediately before the carriage 3 arrives at the head of the area corresponding to the reading range set from the PC, P
The drive speed is changed from C to a speed corresponding to a preset reading resolution, and reading of the original placed on the original glass 2 is started. The original 9 is illuminated by the lamp 13 through the original glass 2, and the reflected light from the original is reflected by the reflection mirrors 15-1, 15-2 and 15-3 and reduced on the image sensor 16 by the imaging lens 17. An image is formed and converted into an electric signal. When the reading operation for the specified reading range is completed, the carriage 3 is moved in the direction opposite to the direction d1, and the home position po is moved.
Return to 1.

A method for reproducing the restart position will be described below. FIG. 8 is a diagram illustrating an operation of a carriage drive motor of a conventional image reading apparatus.

FIG. 3A shows a timing when a buffer full occurs during reading, and FIG. 3B shows a timing at the time of restart.

Reference numeral 18 denotes a first phase of the excitation pulse used for driving the carriage, and 19 denotes a second phase of the excitation pulse used for driving the carriage. 20 is a line synchronization signal, that is, Hsy
nc signal.

When a buffer full occurs, the excitation pulse is stopped, and the reading operation is stopped at the same time. At the time of buffer full release, an excitation pulse is generated and at the same time, Hsy
The nc signal 20 is reset. Then, the reading operation after the restart is started.

[0015]

However, the phase of the excitation pulse first phase 18 and the excitation pulse second phase 19 is shifted from Hsync 20 between the time when the buffer full occurs and the time when the buffer is released.

That is, since the measurement and reproduction of the phase relationship between the position information signal and the line synchronizing signal are not performed with high accuracy at the time of restart, the phase relationship shifts before and after restart as described above. It is. For this reason, there is a problem that a clear step is generated at a position where the read image is restarted.

Therefore, an object of the present invention is to reproduce the phase relationship between the position information signal and the line synchronization signal at the start of the restart with high accuracy.

[0018]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for reading an image line by line.
The position information composed of coarse position information based on a reading device drive signal for driving a reading device constituted by a photoelectric conversion element or the like in a prescribed direction and minute position information finer than the coarse position information, Reading restart position detecting means for detecting when a line synchronizing signal used for reading an image in units is input, and using the position information of at least one of the coarse position information and the minute position information, the reading means restarts reading. An image reading apparatus comprising: a reading restart position reproducing unit that reproduces a reading restart position by resetting a line synchronization signal when a position is reached.

With the above arrangement, the phase relationship between the position information signal and the line synchronizing signal can be reproduced with high accuracy at the start of the restart.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, in order to read an image line by line, a reading unit drive signal for driving a reading unit composed of a photoelectric conversion element or the like in a predetermined direction is provided. Reading restart position detecting means for detecting position information composed of coarse position information based on the position information and fine position information finer than the coarse position information at the time of inputting a line synchronization signal used for reading an image in line units. Reading restart that reproduces the reading restart position by resetting the line synchronization signal when the reading unit reaches the reading restart position, using the position information of at least one of the coarse position information and the minute position information. An image reading apparatus characterized by comprising a position reproducing means, wherein a phase relationship between a position information signal and a line synchronization signal is obtained. It is possible to carry out the current with high accuracy.

The invention according to a second aspect of the present invention is characterized in that the multi-phase reading means driving signal formed by shifting the phase of the reading means driving signal is input to a coarse position information detecting means. 2. The accuracy of the coarse position information can be improved.

According to a third aspect of the present invention, the reading restart position is determined by measuring an interval smaller than the interval measured by the coarse position information detecting unit in the period of the reading unit drive signal. 2. The image reading device according to claim 1, wherein the accuracy of the minute position information can be improved.

Hereinafter, an embodiment of the present description will be described with reference to the drawings. The components in FIGS. 6 and 7 are the same as those in the conventional example, and the description is omitted.

Next, the hardware configuration of the image reading apparatus according to the present invention will be described with reference to FIG.

FIG. 1 is a diagram showing a hardware configuration of an image reading apparatus according to the present invention. In FIG. 1, reference numeral 21 denotes an amplifier and an A / D converter, which define an analog signal RGB output from the image sensor 16. Amplification at the amplification rate of
The data is converted into digital data RGB. A shading correction unit 22 normalizes the digitized image data between white and black levels. An image processing unit 23 performs a color correction process, a resolution conversion process, and the like. Reference numeral 24 denotes a buffer, and the image data is temporarily stored in the buffer and then output from the image reading device. An interface 25 outputs the image data stored in the buffer 24 while negotiating with an external device. A CPU 26 controls the overall operation of the image reading apparatus.

Reference numeral 27 denotes a reading reference signal generation unit,
The pulse is output at a prescribed cycle according to the value written in advance by the PU 26. Reference numeral 28 denotes a pulse signal generated by the read reference signal generation unit 27, and hereinafter Hsync2
Described as 8. Hsync 28 gives one line cycle,
In this image reading apparatus, it is used by various modules as a one-line start signal of image data processing. Reference numeral 29 denotes a buffer status management unit which monitors the use status of the buffer 24, that is, whether the buffer 24 is full or empty, and notifies the CPU 26 of the status.
Reference numeral 30 denotes a motor control unit which manages the driving speed of the stepping motor 31 and the position associated with the driving (motor driving position = position of the carriage 3).

Next, the CPU 26 writes the generation cycle of the Hsync 28 in the read reference signal generation section 27. Thereafter, the operation of the reading reference signal generation unit 27 is started. As a result, generation of Hsync 28 is started. On the other hand, CPU 26
Is detecting Hsync28 by interruption, and Hs
Upon detecting the sync 28, the Hsync counter variable is immediately incremented.

Next, a method of managing the carriage position when reading the first line (reading start line) when reading an image will be described with reference to FIGS. 1, 6 and 2. FIG. FIG. 2 is a diagram showing an image reading apparatus according to the present invention and an external host device (PC) for controlling the image reading apparatus.

First, the use of a general image reading apparatus will be described with reference to FIG. In FIG. 2, reference numeral 1 denotes an image reading apparatus main body. A host device (PC) 32 controls the image reading device and receives image data. Reference numeral 33 denotes the image reading device main body 1 and the host device 3
2 is a cable connecting the two.

Generally, a SCSI (Small Computer Sy) is provided between the image reading apparatus and the host apparatus.
In many cases, the connection is made using a “Stem Interface”. In the SCSI, the host device 32 specifies the reading resolution in the main scanning direction and the sub-scanning direction, the reading start position in the main scanning direction and the sub-scanning direction, the reading length in the main scanning direction and the sub-scanning direction, and the like for the image reading device main body 1. (These are generally Set Window
Command). And the host device 32
Issues a reading start command (Scan command) to the image reading apparatus main body 1, the image reading apparatus main body 1 starts driving the carriage 3 shown in FIG. An image is read according to setting parameters such as a reading resolution in the sub-scanning direction, a reading start position in the main scanning and sub-scanning directions, and a reading length in the main scanning and sub-scanning directions.

In general, the host device 32 reads an image at low resolution (about 30 dpi to 60 dpi is often specified in consideration of the resolution of the display device) before obtaining the image data to be finally obtained ( After the pre-scan) and the pre-scan, the final image data is read by designating the area and the reading resolution. (Main scan).

Next, referring to FIG. 1, the image reading apparatus
A process of reading an image from a designated reading start position will be described. The CPU 26 obtains reading start position information in the sub-scanning direction via the interface 25 (more specifically, SCSI). The CPU 26 converts the reading start position information into the number of driving steps of the motor 31. In the image reading apparatus according to the present invention, since the driving source of the carriage 3 shown in FIG. 6 is a stepping motor, the moving distance can be easily replaced with the number of pulses output to the stepping motor. The CPU 26 is a motor control unit 30
, An excitation pulse cycle for driving the stepping motor is set, and driving of the motor is started. Motor control unit 3
0 is set to CP each time an excitation pulse is issued to the motor 31.
An excitation pulse output notification signal is output to U26. This notification signal is an interrupt factor of the CPU 26, and C
The PU 26 can accurately grasp the amount of rotation of the motor 31, that is, the amount of movement of the carriage 3 in FIG. 6 by counting the notification signal in the interrupt processing. Therefore CP
U26 can grasp the reading start position in the sub-scanning direction specified by the host device by counting the excitation signal of the stepping motor.

Next, a case where the image reading is interrupted during the reading operation will be described with reference to FIGS. 6, 1 and 2. FIG.

The image reading apparatus main body 1 includes a host device 32
Although the function of reading an image can be exhibited for the first time by connecting to the host device 32, the performance of the host device 32 varies, and the image data is transferred from the image reading device main body 1 to the host device 32 depending on the performance of the host device 32. The time to do it also varies greatly.

If the processing speed of the host device side is slow and it becomes impossible to output image data, the image reading device main body 1 cannot read the image any more.
The image reading operation is interrupted. Normally, in order to minimize this interruption, the image reading apparatus main body 1 is provided with a buffer 24 shown in FIG. 1 so that even if the host apparatus 32 cannot receive image data (that is, the image data is Even if the transfer is stopped), the image reading apparatus main body 1 can continue reading the image.

However, since the capacity of the buffer 24 is limited due to cost restrictions, it is impossible to keep the image data beyond the capacity of the buffer 24.
Such a state in which the buffer 24 of the image reading device 1 becomes full is referred to as a buffer full. When the buffer full occurs, the image reading device main body 1 temporarily suspends the image reading operation, and the host device 32
4 waits for the image data held in 4 to be downloaded via the interface 25. That is, while a large amount of image data remains in the buffer 24, the reading operation is suspended, and when the buffer 24 becomes empty to some extent (buffer empty), the image reading operation is restarted. This operation is called a restart operation.

The CPU 26 can detect the transition to the buffer full state by an interrupt signal (buffer monitor signal) generated by the buffer state management unit 29 for managing the state of the buffer 24. When the CPU 26 detects that the buffer is full, it drives the carriage 3 by a small amount in the direction opposite to the reading direction to prepare for resuming reading. Then CP
The U26 periodically checks the buffer monitor signal, and upon detecting the release of the buffer full state (buffer empty), drives the carriage in the reading direction at a speed according to the reading resolution designated by the host device 32, and the buffer full state is detected. Resume reading from the line following the occurrence of.

Next, the control of the carriage position at the time when the restart occurs will be described with reference to FIGS.

FIG. 3 is a diagram showing details of the motor control unit 30 in FIG. In FIG. 3, 34 is a counter 1
And counts clock signals having a predetermined cycle.

Reference numeral 35 denotes a register 1a to which a value is written from the CPU 26. 36 is a register 1b, CP
The value is written from U26.

Reference numeral 37 denotes a counter 2 which counts clock signals having a predetermined period, similarly to the counter 1.

Reference numeral 38 denotes a register 2a to which a value is written from the CPU 26. 39 is a register 2b, and CP
The value is written from U26.

Reference numeral 40 denotes a counter 3, which counts clock signals having a predetermined period.

Reference numeral 41 denotes a register 3a, Hsync2
Every time 8 occurs, the count value of the counter 3 (40) is read and held. The register 3a can be read from the CPU 26, and the CPU 26 can obtain the count value of the counter 3 held in the register 3a every time an interrupt by the Hsync 28 occurs.

Reference numeral 42 denotes a register 3b to which a value is written from the CPU 26. A clock signal generator 43 generates a clock signal having a predetermined cycle. The output of the clock signal generator 43 is input to the counter 1, the counter 2, and the counter 3, which count the clock signal generated by the clock signal generator 43.

Reference numeral 44 denotes a comparator 1a, which is a counter 1 (3
The count value of 4) is compared with the value of the register 1a (35), and if they match, a match signal is generated (compare match). The coincidence signal output from the comparator 1a (44) is notified to the CPU 26 as an interrupt,
26 counts the number of occurrences of the coincidence signal (more specifically, the CPU 26 regards the coincidence signal output from the comparator 1a (44) as an excitation pulse of the motor, and uses the counted value as position information of the carriage. Do). The coincidence signal of the comparator 1a (44) is input to the counter 1, counter 2, and counter 3, and each counter is reset to 0 by the input of the coincidence signal. That is, the counter 1, the counter 2, and the counter 3 perform a so-called synchronous operation in which the counter 1 is reset all at once when the counter 1 reaches a specific value.

Reference numeral 45 denotes a comparator 1b, which is a counter 1 (3
The count value of 4) is compared with the value of the register 1b (36), and if they match, a match signal is generated (compare match).

Reference numeral 46 denotes a comparator 2a, which is a counter 2 (3
The count value of 7) is compared with the value of the register 2a (38), and if they match, a match signal is generated (compare match).

Reference numeral 47 denotes a comparator 2b, which is a counter 2 (3
The count value of 7) is compared with the value of the register 2a (39), and if they match, a match signal is generated (compare match).

Reference numeral 48 denotes a comparator 3, which is a counter 3 (4
The count value of (0) is compared with the value of the register 3b (42), and if they match, a match signal is generated (compare match).

49h Output control unit 1 and comparator 1a
The match signal output from (44) and the comparator 1b (4
Based on the coincidence signal output from 5), a motor excitation signal (one phase) is generated.

A motor driver 50 drives the stepping motor 31 based on the one-phase excitation signal output from the output controller 1 (49).

Reference numeral 51 denotes an output control unit 2, which is a comparator 2a.
The coincidence signal output from (46) and the comparator 2b (4
7) Based on the coincidence signal output from 7), the output control unit 1
A signal whose phase is shifted by 90 ° from the output of (49) is generated.

Reference numeral 52 denotes an output control unit 3, which is a comparator 3 (4
From 8), so-called toggle output is performed in which High and Low are alternately inverted each time a match signal is input.

Reference numeral 53 denotes a counter 4 which is an output control unit 1
The excitation signal output from (49) and the output control unit 2 (5
This is a phase counting counter that uses a signal output from 1), which is 90 ° out of phase with the output of the output control unit 1 (49), as a two-phase input. The counter 4 (53) measures the amount of rotation of the motor, that is, the amount of movement of the carriage, without the intervention of the CPU 26.

Reference numeral 54 denotes a register 4a, which is Hsync2
Every time 8 occurs, the count value of the counter 4 (53) is read and held. The register 4a can be read from the CPU 26, and the CPU 26 can obtain the count value of the counter 4 (53) held in the register 4a, that is, information on the position of the carriage, every time an interrupt is generated by the Hsync 28.

Reference numeral 55 denotes a register 4b to which a value is written from the CPU 26. Reference numeral 56 denotes a comparator 4, which compares the count value of the counter 4 (53) with the value of the register 4b (55), and generates a match signal (compare match) when they match.

Numeral 57 denotes a double edge detection unit which detects both edges of the toggle signal output from the output control unit 3 (52) and generates a pulse signal corresponding to both edge positions. 5
Reference numeral 8 denotes a gate circuit, which outputs a pulse signal having a specified width based on the signals from the two edge detectors 57 when the comparator 4 (56) generates a coincidence signal. The output of the gate circuit 58 is input to the CPU 26. The CPU 26 recognizes the output of the gate circuit 58 as an interrupt.

The motor control unit 30 configured as described above
Will be described in detail with reference to FIGS. 3 and 4.

FIG. 4 is a diagram showing the operation of the motor control unit 30 from before the occurrence of buffer full to when it occurs.

The counter 1 (34) and the counter 2 (3
7) The counter 3 (40) is counted up by a predetermined clock signal generated by the clock signal generator 43. A set value 59 is set in the register 1a (35), and when the count value of the counter 1 (34) reaches the set value 59, it is cleared to zero. Further, the coincidence signal output from the comparator 1a (44) allows the counter 2 (37), the counter 3
(40) is also cleared to 0 at the same time. On the other hand, register 1b
The set value 60 is set in (55). Set value 60
Is set to 1/2 of the set value 59.

The comparator 1a (44) is a counter 1 (34)
Is compared with the set value 59, and when the values match, a match signal is output, and the comparator 1b (45) outputs the counter 1 (3
The count value of 4) is compared with the set value 60, and when the values match, a match signal is output.
9), and when the output control unit 1 (49) detects a coincidence signal from the comparator 1a (44), the output is switched to Hi.
gh, and when a coincidence signal is detected from the comparator 1b (45), the output is set to Low. Thus, the output control unit 1 output 61
Is obtained. The output control unit 1 output 61 is the motor driver 5
0, the motor driver 50 controls the rotation of the motor 31 based on the output 61 of the output control unit 1.
The setting value 62 is set in the register 2a (38), and the setting value 63 is set in the register 2b (39). The set value 62 is set as set value 62 = (set value 59 + set value 60) / 2... (Equation 1), and the set value 63 is set as set value 63 = set value 60/2. Have been.

The comparator 2a (46) is the counter 2 (37)
Is compared with the set value 62, and when the values match, a match signal is output, and the comparator 2b (47) sets the counter 2 (3
7) is compared with the set value 63, and when the values match, a match signal is output.
1). When the output control unit 2 (51) detects a coincidence signal from the comparator 2a (46), it outputs Hi.
gh, and when a coincidence signal is detected from the comparator 2b (47), the output is set to Low. Thus, the output control unit 2 output 64
Is obtained.

By setting the set value 59, the set value 60, the set value 62, and the set value 63 as described above, the output control unit 2
The phase difference between the output 64 and the output 61 of the output control unit 1 can be controlled.
° phase difference).

The output 61 of the output control unit 1 and the output 64 of the output control unit 2 are input to the counter 4 (53), and the counter 4 (53), which is a phase counting counter, goes up or down based on the phase difference between the two inputs. Functions as a counter. The count value of the counter 4 (53) is held in the register 4a (54) every time the Hsync 28 is input, and
When U26 is interrupted by Hsync28,
The value of the register 4a (54) is read and stored (Po1H: coarse position information 65).

Since the value of Po1H is a count value which is counted up every motor driving step, Hsync2
This means that the carriage position when 8 occurs is roughly measured. On the other hand, in counter 3 (40), Hsync28
Each time is input, the count value is held in the register 3a (41), and when an interrupt is generated by the Hsync 28, the CPU 26 reads and stores the value of the register 3a (41) (PO1L: minute position information 66). .

Although the minute position information 66 does not directly reflect the driving state of the motor, the motor is driven at a substantially constant speed between the driving pulses, and the power of the motor is transmitted via a belt or the like. Since the driven carriage can be regarded as being driven at substantially constant speed, the minute position information 66 can be regarded as carriage position interpolation information between motor excitation pulses.

That is, PO1L minutely measures the carriage position when Hsync 28 occurs.

The hardware of the image reading apparatus according to the present invention is designed so that the image data is valid up to Hsync 28 immediately before the buffer is full. The occurrence of the buffer full is input from the buffer state management unit 29 to the CPU 26. However, when the buffer full occurs, the reading of the image data, that is, the data processing is stopped without the intervention of the CPU 26.

When the CPU 26 detects that the buffer is full,
Immediately, the motor 31 is stopped, the signal generation rule of the output control unit 2 (51) is changed, and the counter 2 (37) and the set value 6 are set.
2 is Low due to the match signal output when 2 matches.
Is set to output High by a match signal output when the counter 2 matches the set value 63, and then the motor 31 is rotated in the direction opposite to the reading direction. Since the phase shift direction of the output control unit 1 output 61 and the output control unit 2 output 64 is opposite, the counter 4 which is a phase counting counter functions as a down counter.

The CPU 26 stores the value of the Hsync counter when a buffer full occurs. Also, the Hsy
coarse position information 6 immediately before the nc counter value
5 (ie, PO1H) and the minute position information 66 (ie, PO1H).
L) is stored as the restart position when the buffer full is released. Then, the CPU 26 drives the motor in a direction opposite to the reading direction so that the carriage position is PO1H.
Then, the carriage is driven until it is upstream (in the direction opposite to the reading direction) from the position at which the buffer full is detected, and then the motor is stopped to wait until the buffer full is released.
(The down count of the counter 4 due to the motor reverse rotation is
This is performed until the value becomes smaller than the value shown in FIG. 4).
Next, the operation when the buffer full is released will be described with reference to FIGS.

FIG. 5 is a diagram showing the operation of the motor control unit 30 at the time of buffer full release. The release of the buffer full is transmitted from the buffer state management unit 29 to the CPU 26. When the CPU 26 recognizes the buffer full release, the CPU 26
Writes PO1H as the set value 67 in the register 4b (55), and further writes PO1L as the set value 69 in the register 3b (42).

Then, the motor returning in the direction opposite to the reading direction is driven in the reading direction.

By writing PO1L as the set value 69 in the register 3b (42), the comparator 3 (48) causes the counter 3 (40) and the register 3b (42) to repeat up-counting and reset together with driving of the motor (31). Are compared, and when a match occurs, a match signal is output to the output control unit 3.
Output to (52). Each time the output control unit 3 (52) receives the coincidence signal, the output control unit 3 (52) alternately repeats Low and High.
Output a so-called toggle signal (output control unit 3 (52)
Output 70). Further, the both-edge detecting section (57) detects both edges of the toggle signal and outputs a pulse signal corresponding to both-edge positions (both-edge detecting section (57) output 71).

On the other hand, by writing PO1H as the set value 67 in the register 4b (55), the comparator 4 (56)
Compares the value of the counter 4 (53), which is counted up with the driving of the motor (31), with the value set in the register 4b (55), and outputs a match signal to the gate circuit (58) when a match occurs (comparator) 4 (56) output 68).

In the gate circuit (58), the comparator 4 (56)
When the output 68 is input, an interrupt signal is generated for the CPU 26 based on the output 71 of the both-edge detector (57) that has occurred next (the output 72 of the gate circuit (58)). CP
U26 is at the position indicated by position 73, and upon detecting this interrupt signal, resets Hsync28.

As described above, the CPU 26 stores the buffer full occurrence position as the position 74 based on the Hsync count value. Since buffer full occurs on the last valid line, the next line to read is from the next Hsync after position 73. Therefore, if the CPU 26 starts the operation of the hardware immediately after detecting Hsync at the position 73, the CPU 26 can accurately read the image data from the line next to the line where the buffer full occurs.

As described above, while reading the image, based on the reference value of the Hsync count value,
Precise position information of the carriage is measured, and when a buffer full occurs, the carriage returns a minute distance and stops, and when the carriage reaches the line position to be read after the buffer full is released, based on the measured carriage position information , Hsync, the phase relationship between the carriage position information and the Hsync signal can be restored to the state before reading.

[0079]

As described above, according to the present invention, the CPU
Reaches the reading start designated position, the accurate position information of the carriage is measured based on the Hsync count value while reading the image, and when the buffer is full, the carriage is returned by a small distance and stopped, and the buffer is stopped. When the carriage reaches the line position to be read after the full release, the Hsync signal is reset based on the measured carriage position information, so that the phase relationship between the carriage position information and the Hsync signal can be restored to the state before reading. it can.

As a result, even if a buffer full occurs, it is possible to keep reading the image without any apparent step difference.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a hardware configuration of an image reading apparatus according to the present invention.

FIG. 2 is a diagram illustrating an image reading device and an external host device (PC) that controls the image reading device.

FIG. 3 is a diagram showing details of a motor control unit.

FIG. 4 is a diagram showing an operation of a motor control unit before and after a buffer full occurs.

FIG. 5 is a diagram showing the operation of the motor control unit at the time of buffer full release.

FIG. 6 is a diagram schematically showing a conventional image reading apparatus.

FIG. 7 is a diagram showing an internal structure of a carriage of a conventional image reading apparatus.

FIG. 8 is a diagram showing an operation of a carriage drive motor of a conventional image reading apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image reading apparatus main body 3 Carriage 4 Drive source 16 Image sensor 24 Buffer 25 Interface 27 Reading reference signal generation part 28 Hsync (signal name) 29 Buffer state management part 30 Motor control part 31 Motor 32 Host device (PC)

Claims (3)

[Claims] 1. A coarse position information based on a reading unit drive signal for driving a reading unit constituted by a photoelectric conversion element or the like in a prescribed direction to read an image in line units.
Reading restart position detecting means for detecting position information composed of minute position information finer than the coarse position information at the time of inputting a line synchronization signal used for reading an image in line units; A read restart position reproducing unit that reproduces the read restart position by resetting the line synchronization signal when the reading unit reaches the read restart position by using position information of at least one of the minute position information. An image reading device characterized by being performed. 2. The image reading apparatus according to claim 1, wherein the multi-phase reading means driving signal formed by shifting the phase of the reading means driving signal is input to a coarse position information detecting means. 3. The method according to claim 2, wherein:
2. The image reading apparatus according to claim 1, wherein the reading restart position is detected by measuring a smaller interval than the interval measured by the coarse position information detecting means.