JP3066904B2 - Image reading device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus that reads an image using a line sensor.

[Conventional technology]

As an image reading device used for image input of personal computers, facsimile machines, etc., a document is transported using a paper feed roller and paper discharge roller driven by a motor, and a document image passing through the reading position is scanned by a CCD line sensor etc. There is known a type in which photoelectric exchange is performed for each line to obtain image data.

[Problems to be solved by the invention]

However, in the conventional image reading apparatus, when the motor is driven at a constant speed to read an image, if the motor is stopped for some reason, the reading is interrupted, and the reading is restarted, the movement of the original is stopped. However, there is a disadvantage that the image disappears and deteriorates at the joint of the images without synchronizing the sensor driving with the sensor driving.

[Means for solving the problem]

The present invention has been made in view of the above points, a reading unit that reads a document image line by line, a moving unit that relatively moves the reading unit and the document, and an image data read by the reading unit. Processing means for processing, when operating the moving means at a constant speed, output a drive pulse at a constant interval to the moving means, when decelerating the moving means, the driving pulse with a pulse interval gradually becomes longer A driving unit for outputting to the moving unit, and a control unit for selectively taking in the image data of each line read by the reading unit to the processing unit, wherein the control unit controls the moving unit by the driving pulse. While the relative moving speed is gradually decelerating, the image data per driving pulse is smaller than the period in which the relative speed is constant before the deceleration is started. Said reading means to increase the uptake number of is to provide an image reading apparatus characterized by having a control means for selectively taken up to said processing means the image data of each line read is.

Also, the present invention provides a reading unit for reading a document image line by line, a moving unit for relatively moving the reading unit and the document, a processing unit for processing image data read by the reading unit, When operating the means at a constant speed, a drive pulse that outputs a drive pulse at a constant interval to the moving means, and when accelerating the moving means, a drive means that outputs a drive pulse whose pulse interval gradually decreases to the moving means. Control means for selectively loading the image data for each line read by the reading means into the processing means, the control means gradually increasing the relative moving speed of the moving means by the driving pulse. During the operation, the number of image data to be captured per drive pulse is reduced compared to a period in which the relative speed is constant after the end of acceleration. There is provided an image reading apparatus characterized by having a control means for selectively taken up to said processing means the image data of each line of the reading means read.

〔Example〕

 Hereinafter, the present invention will be described using preferred embodiments.

FIG. 2 is a block diagram showing a configuration of an image reading apparatus to which the present invention is applied.

In the figure, 1 is an apparatus main body, 2 is a document table, and a sheet document conveying path 3 is formed on an extension of the document table. A pickup roller 4 for transporting the sheet document, a microswitch 5 that operates with a small force to detect the presence of the sheet document, and a pair of transport rollers (paper feed). Rollers 6 and 6a, a microswitch (a cue sensor) that operates with a small force for detecting the leading and trailing edges of the document, a pair of transport rollers (discharge rollers) 8 and 8a, and a sheet document discharging device. A paper tray 9 is provided. The transport rollers 6, 6a and 8, 8a are driven to rotate by a stepping motor (not shown).

A fluorescent lamp 14 is a light source for illuminating the original.
Irradiates the document conveyed to the mirror 16
The original image is input to a photoelectric conversion element (CCD line sensor) 18 composed of a plurality of light receiving elements arranged in a line via a lens 17, and the original image is read and scanned line by line. The reading position 15 is provided with a uniform white reference plate 11 having a white color.

The transport path 3 is formed by a guide unit 19 and a guide member 20 and can be opened upward at a document reading position 15. That is, the guide unit 19 is
The microswitch 22 is turned on around a fulcrum 21 on the apparatus main body. When the transport path 3 is opened, the micro switch 22 is turned on, and the opening of the transport path 3 can be detected.

Next, the operation of the image reading apparatus configured as described above will be described.

When the guide unit 19 is closed,
When the sheet document 23 is placed on the document table 2 and the start switch provided on the operation unit is operated, the micro switch 5 first detects the presence or absence of the sheet document, and the micro switch 5 Turns on the solenoid when detecting the sheet document, presses the pickup roller against the sheet document, and conveys the sheet document to the left.
When the leading end of the sheet document is held between the conveying rollers 6 and 6a and the microswitch 7 detects the sheet document, the solenoid is turned off and the pressure of the pickup roller 4 is released.

When the solenoid is turned off and the pressure of the pick-up roller 4 is released, the drive motor is driven in the SA step to convey the sheet document by the distance A from the microswitch 7 to the reading position 15. Then, when the leading end of the sheet document reaches the reading position 15, reading of the document image is started. In this reading, the fluorescent lamp 14 illuminates the sheet original, the reflected light forms an image on the CCD line sensor 18 via the mirror 16 and the lens 17, and the CCD line sensor 18 converts the image into one image.
This is performed by converting into an electric signal for each line.
Thereafter, when the rear end of the sheet document reaches the reading position 15 and reading is completed, the motor is driven by the number of steps SB corresponding to the distance B from the reading position 15 to the conveying rollers 8, 8a, and the sheet document is placed on the tray 9. To be discharged. This completes the sheet document reading operation.

FIG. 1 is a block diagram of a control circuit of the image reading apparatus shown in FIG.

31 is a CPU, ROM, RAM to control the entire sequence
32, a CCD line sensor; 33, a binarizing circuit for converting image data obtained from the CCD line sensor 32 into monochrome binary data; 34, a memory for storing binary image data; Communication control unit (CCU), 36 is a timing generation circuit, 37 is a cue sensor, 38 is a timer,
39 is a motor driver circuit, 40 is a stepping motor for document conveyance, and 41 is an AND gate.

The operation of the circuit block shown in FIG. 2 will be described in detail.

The timing circuit 36 generates a synchronization signal SH for the CCD line sensor 32 and the binarization circuit 33. To the CCD line sensor 32 and the binarizing circuit 33, an image clock VCLK, which is a synchronizing signal of an image signal for each dot, is input from a timing circuit 36 together with a horizontal synchronizing signal SH indicating the beginning of one line. The horizontal synchronization signal SH is input to the controller 31 as an interrupt signal. FIG. 3 shows the operation of generating the horizontal synchronizing signal SH and the image clock VCLK.

The CCD line sensor 32 synchronizes with the horizontal synchronizing signal SH
The image data for the line is output to the binarization circuit 33.

The binarizing circuit 33 converts the image data obtained from the CCD line sensor 32 into monochrome binary data in synchronization with the horizontal synchronizing signal SH, and writes it into the memory 34. A gate 41 is provided at the input of the horizontal synchronizing signal SH to the binarization circuit 33. The gate 41 receives a gate signal G output from the controller 31.
When the gate 41 is closed, the horizontal synchronization signal SH is not input to the binarization circuit 33, and the binarization of the image data and the writing to the memory 34 are stopped.

The CCU 35 performs facsimile communication procedures, and
And reads out the image data from the communication line. CC
The U35 also manages the memory 34, and notifies the controller 31 of the availability of the memory 34 by a signal M.

In FIG. 2, a sheet document is conveyed from right to left. When the stepping motor 40 is rotated, the sheet feeding roller 6 is rotated.
Then, the paper discharge roller 8 rotates to convey the sheet document. When the leading edge of the sheet document passes the cueing sensor 37, a signal S is sent to the controller 31.

A motor driver circuit 39 is provided to rotate the stepping motor 40. The controller 31 sends a drive pulse signal MP and a current value setting signal Mi to the motor driver circuit 39. Upon receiving the drive pulse signal MP, the motor driver circuit 39 causes the current set by the signal Mi to flow to the stepping motor 40 to rotate the stepping motor 40 by one step.

The timer 38 can arbitrarily set a timer value by the controller 31, and sends an interrupt signal TM to the controller 31 when the timer value reaches the set timer value.

 Hereinafter, the operation at the time of image reading will be described.

The controller 31 starts operation in response to the input of the horizontal synchronization signal SH generated from the timing circuit 36.

First, the stepping motor 40 is accelerated to reach a predetermined speed. The controller 31 sets the current value with the signal Mi to the motor driver 39, sends the drive pulse signal MP, and further sets the motor drive cycle to a timer.
Set to 38. When the TM signal is input from the timer 38, the current value setting signal Mi is transmitted again, the driving pulse MP is transmitted,
The timer is set, and this is repeated as shown in FIG. now,
It is assumed that the current value can be set in three stages of 1 to 3. The motor drive is started by the horizontal synchronization signal SH, and the timer value set in the timer 38 is gradually reduced, so that the generation interval of the drive pulse signal MP is gradually shortened, and the current value Mi is also gradually increased. By accelerating the stepping motor. Finally, the horizontal synchronization signals SH and TM
The timer value is adjusted so that the signals are synchronized, and the operation shifts to the constant speed drive from the time of synchronization (Syn).

Next, when the sheet original reaches the cue sensor 37, the signal S
Is input to the controller 31. From there, the controller 31 drives a motor for a predetermined number of steps necessary for the document to reach the reading position 15, then outputs a gate signal G to enable the gate 41, and sends a horizontal synchronizing signal to the binarization circuit 33.
Image input is started by inputting SH (FIG. 5).

The CCU monitors the state of the memory, and sends a read interruption signal RS to the controller 31 when the free space in the memory decreases. When the controller 31 receives the RS signal, it shifts to the reading interruption operation.

 FIG. 6 shows a timing chart of the reading interruption operation.

When the reading interrupt operation starts according to the input of the signal RS, the timer
While gradually increasing the set value of 38 to gradually increase the generation interval of the drive pulse signal MP, the current set value Mi is also gradually reduced. On the other hand, the gate signal G is operated to prevent the image from being extended due to the deceleration of the motor 40. That is, the gate signal G is operated when the SH interrupt occurs, and the number of drive steps of the motor 40 and the number of read lines are matched.

Then, when the speed becomes sufficiently low, the horizontal synchronizing signal SH and the MP signal are synchronized with each other. Further, until the rotation of the motor 40 is stabilized, the motor 40 is driven several steps, and the driving and reading of the motor 40 are stopped.

Here, regarding the operation of the gate signal G, if the motor speed is reduced due to the nature of the document conveyance system, the document reading position may relatively move forward. G for such a system
As described above, the number of lines larger than the number of drive steps is read to prevent image distortion.

On the other hand, the CCU 35 turns off the RS signal when there is sufficient space in the memory 34 after the reading is interrupted. The controller 31 resumes reading when the RS signal drops. Regarding the method of restart, two methods will be described.

The first method is to reverse the above-mentioned interruption. That is, as shown in FIG. 7, in order to accelerate the motor 40, the set value of the timer 38 is gradually shortened, the current value is increased, and the number of read lines is adjusted by the gate signal G. Also in this case, the reading position of the original may relatively retreat in accordance with the motor acceleration depending on the transport system. In this case, the number of lines smaller than the number of drive steps, such as G ', is read.

Another method of restarting the motor is to fix the motor drive current value to 1 and restart the motor 40 at a low speed and a constant speed after the restart, as shown in FIG. Motor 40
Causes uneven rotation due to resonance or the like during acceleration. Therefore, the remaining portion of the document is read at a constant low speed in order to prevent deterioration in image quality due to uneven rotation.

 Finally, the operation at the end of reading is as shown in FIG.

When the trailing edge of the document passes below the cue sensor 37, the signal S falls. After the signal S falls, the controller drives the motor 40 for a predetermined number of steps necessary for the trailing edge of the document to pass the reading position 15, and then lowers the gate signal G to level the horizontal signal to the binarization circuit 33. The input of the synchronization signal SH is inhibited, and the reading is terminated. Then, the motor 40 is continuously rotated until the sheet document is discharged, and the motor 40 is further decelerated and stopped.

In the above-described embodiment, the motor drive timing is all based on the interrupt signal (TM) from the timer 38. However, during the constant speed drive, the motor drive is performed using the horizontal synchronization signal SH without using the TM38. The timer 38 may be used only when a pulse (MP) is generated and the motor 40 is accelerated or decelerated.

In addition, the type in which an image is read while a sheet original is conveyed has been described. On the contrary, the image is read by fixing the original and moving an optical element for guiding a light image to a line sensor or a sensor. The present invention is also applicable to movement control of a line sensor or an optical element in a type of reader.

The cause of the interruption of the reading operation is not only the overflow of the memory but also other causes such as an interruption instruction from the destination of the image data. In this case, the interruption and the resumption of the reading are similarly controlled.

Further, it goes without saying that other processing such as multi-level processing by an A / D converter and halftone processing may be performed on the image data from the line sensor in addition to the binarization processing.

〔The invention's effect〕

As described above, according to the present invention, while the relative moving speed of the moving means is gradually decelerating by the driving pulse, the driving pulse 1 is compared with the period in which the relative speed before the start of deceleration is constant. Since the number of image data per line is increased and the image data for each line read by the reading unit is selectively taken into the processing unit, when the reading speed is reduced, the reading position of the original is relatively forward. The distortion of the document image read while the relative moving speed between the reading means and the document is reduced can be reduced.

Further, according to the present invention, while the relative moving speed of the moving means is gradually accelerating by the driving pulse, the driving pulse is not longer than the period in which the relative speed is constant after the end of the acceleration.
Since the number of image data taken per line is reduced and the image data for each line read by the reading means is selectively taken into the processing means, the reading position of the document relatively moves backward when the reading speed is increased. In the apparatus, the distortion of the original image read during acceleration of the relative movement speed between the reading means and the original can be reduced.

[Brief description of the drawings]

 1 is a block diagram of an image reading apparatus embodying the present invention, FIG. 2 is a block diagram of the image reading apparatus, FIG. 3 is a timing chart of SH and VCLK, and FIG. 4 is a timing chart at the start of conveyance. 5 is a timing chart at the start of reading, FIG. 6 is a timing chart at the time of interrupting reading, FIG. 7 is a timing chart at the time of resuming reading, FIG. 8 is a timing chart at the end of reading, FIG. FIG. 9 is a timing chart at the end of conveyance. 31 ... Controller 32 ... CCD line sensor 33 ... Binarization circuit 34 ... Memory 36 ... Timing circuit 37 ... Cueing sensor 38 ... Timer 39 ... Motor driver circuit 40 ... Stepping motor 41 ... … Gate circuit

Claims (8)

(57) [Claims] A reading unit that reads a document image line by line; a moving unit that relatively moves the reading unit and the document; a processing unit that processes image data read by the reading unit; When operating at a constant speed, a driving pulse that outputs a driving pulse at a constant interval to the moving unit, and when decelerating the moving unit, a driving unit that outputs a driving pulse whose pulse interval gradually increases to the moving unit, Control means for selectively loading the image data for each line read by the reading means into the processing means, wherein the control means gradually reduces the relative moving speed of the moving means by the driving pulse. During this period, the number of image data taken per drive pulse is increased compared to a period in which the relative speed before the start of deceleration is constant. Control means for selectively loading the image data for each line read by the reading means into the processing means. 2. The method according to claim 1, wherein when the reading is interrupted during the reading of the document, the driving unit outputs the driving pulse to the moving unit so as to gradually reduce the relative moving speed. 2. The image reading device according to claim 1, wherein: 3. When reading is interrupted during reading of a document, and when reading is resumed thereafter, the driving means outputs a driving pulse whose pulse interval gradually decreases to the moving means, and the relative moving speed is reduced. 2. The image reading device according to claim 1, wherein the image reading device is configured to gradually accelerate the image. 4. The image reading apparatus according to claim 1, wherein said control means gradually reduces the amount of drive current of a drive pulse to be applied to said moving means in accordance with deceleration. apparatus. 5. A reading means for reading a document image line by line; a moving means for relatively moving the reading means and the document; a processing means for processing image data read by the reading means; When operating at a constant speed, a driving pulse that outputs a driving pulse at a constant interval to the moving unit, and when accelerating the moving unit, a driving unit that outputs a driving pulse whose pulse interval gradually decreases to the moving unit, Control means for selectively loading the image data for each line read by the reading means into the processing means, wherein the control means gradually increases the relative movement speed of the movement means by the drive pulse. During the operation, the number of image data taken per drive pulse is reduced compared to the period in which the relative speed is constant after the end of acceleration. Control means for selectively loading the image data for each line read by the reading means into the processing means. 6. When reading is interrupted during reading of a document, the driving means outputs a driving pulse having a pulse interval gradually increased to the moving means, and gradually reduces the relative moving speed. Claim 5 characterized by the features
An image reading device according to the item. 7. When reading is interrupted during reading of a document and thereafter reading is resumed, the driving means outputs a driving pulse whose pulse interval gradually decreases to the moving means, and the relative moving speed is reduced. 6. The image reading device according to claim 5, wherein the image reading device is configured to gradually accelerate the image. 8. An image reading apparatus according to claim 5, wherein said control means gradually increases the amount of drive current of a drive pulse to be applied to said moving means in accordance with acceleration. apparatus.