JPH05130336A - Image reader - Google Patents

Abstract

PURPOSE:To speed up the processing in an image processing system by returning at a high speed and exactly a carriage constituting a reading mechanism to a prescribed start position. CONSTITUTION:A CPU 20 executes a scan of designated width by a first carriage 11 by executing an operating instruction to a stepping mode exciting signal generating part 31, and supplying a pulse train of a width corresponding portion of a sub-scan of a read document 2. At the time of return, the CPU 20 executes an operating instruction of a DC mode to a DC mode exciting signal generating part 32, and a DC exciting waveform is generated from the DC mode exciting signal generating part 32. This DC exciting waveform is amplified by a power amplifying part 36 through an FET driving part 34, and supplied to the stepping motor 13. In such a way, the stepping motor 13 is driven by a DC operation, and the carriages 11, 12 move in the opposite direction to the document reading direction 17.

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 for reading an image on a document in order to perform image processing and the like.

[0002]

2. Description of the Related Art Generally, the structure of an optical system of an image reading apparatus such as a facsimile, an image scanner and an OCR is determined by a photoelectric conversion element used. When the contact-type image sensor having a length substantially the same as the document width is used, the optical path length can be shortened, so that the apparatus can be easily downsized and unitized. Further, when a reduction type image sensor having a length shorter than the document width is used, the optical path length becomes long and the size tends to be large, but the depth of focus can be deepened. After illuminating the original with the light source, the reflected light is imaged on the photoelectric conversion element with the lens, the image information of the original is read as an analog image signal, amplified by the analog circuit in the subsequent stage, and then digital image by the A / D conversion circuit. The image data is converted into a signal, optimal image processing is performed, and the image data is transferred to an external device or a host computer. On the other hand, regardless of which optical means is used, although there are differences in the method of fixing or moving the original, the light source is scanned over the original and the reflected light from the original is photoelectrically converted by a combination of optical system means. An image is formed on the element, and the optical signal is converted into an electrical signal and output.

In a conventional image reading apparatus which uses a fixed document reading system and a reduction optical system, a document is scanned by a carriage equipped with a reading mechanism such as a light source and a mirror. A stepping motor is mainly used as a driving source for scanning such a carriage.
In order to suppress the reading pitch error in scanning the original, stable constant speed driving is performed, and at the time of return, the carriage is returned to the start point by step driving.

[0004]

By the way, in recent years, the development of image processing technology of a system using an image reading apparatus as a terminal,
Due to improvements in signal transmission technology and the like, the time required for the document reading sequence can be shortened. Therefore, in the image reading apparatus, it is necessary to speed up the return operation of the carriage that constitutes the reading mechanism and quickly start up the carriage. Has occurred. However, in the above-described conventional image reading apparatus, in order to realize high-speed operation by step driving of the stepping motor, it is necessary to gradually increase the speed by the trapezoidal control, which requires a large number of steps and can be speeded up in a short time. There is a problem in that it is difficult, and when the carriage is moved at high speed, inertial force acts on the carriage, making it difficult to smoothly and accurately stop the carriage at a predetermined start position.

The present invention has been made in response to such a conventional situation, and the carriage constituting the reading mechanism can be quickly and accurately returned to a predetermined start position, and the processing speed in the image processing system can be increased. The present invention aims to provide an image reading device capable of achieving the above.

[0006]

That is, an image reading apparatus according to the present invention is a document scanning unit having a reading mechanism for reading a document and a scanning mechanism having a stepping motor as a driving source, and the stepping motor in a step mode. The scanning control means for driving and controlling the scanning of the original by the original scanning means, the detecting means for detecting the scanning direction and the moving distance of the original scanning means, and the detection signal from the detecting means are referred to And a return control unit for adjusting the amount of electric power supplied to the stepping motor and returning the document scanning unit to a predetermined position by open loop control.

[0007]

In the image reading apparatus of the present invention having the above-described structure, the carriage control at the time of reading the original is performed in the step mode by the scanning control means, and the carriage drive at the return is performed in the DC mode by the return control means. Note that the control at the time of return is performed by referring to the detection signals of the scanning direction and the movement distance by the detection means such as an encoder, while controlling the power amplification section that controls the power of the stepping motor.
This is realized by controlling with a control signal from a control means such as U and limiting the power supplied to the stepping motor.

Therefore, by operating the stepping motor in the DC mode and continuously controlling the rotation of the stepping motor, the acceleration and braking operations can be smoothly performed, and the carriage constituting the reading mechanism can be operated at high speed and accurately. It is possible to return to a predetermined start position.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the image reading apparatus of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 schematically shows the overall structure of the image reading apparatus of this embodiment. This image reading apparatus irradiates a document with a light source and optically processes its reflected image with a lens. Then, the image is formed on a photoelectric conversion element, the original image is converted into an electric signal, and the read image information is subjected to optimum image processing and editing and transmitted to an external device.

In FIG. 1, 1 is an image reading apparatus main body, 2
Is a document, 3 is a platen glass on which a document is placed, 4 is a control circuit for controlling the image reading apparatus main body 1, and 5 is reference correction data for correcting an image signal including shading distortion from a photoelectric conversion element. A reference correction plate for reading the document, 6 is a light source for illuminating the document, 7 is a first mirror for reflecting the reflected light from the document to a mirror of the next stage, 8
Is a second mirror for reflecting the reflected light from the first mirror to the optical means in the next stage, 9 is a lens for forming an image of the reflected light from the second mirror on a photoelectric conversion element described later, 1
Reference numeral 0 is a photoelectric conversion element (CCD sensor) for converting an optical signal into an electric signal, and 11 is a light source 6 and a first mirror 7 so that an original is illuminated by the light source 6 and reflected light from the original is reflected by the first mirror 7. 1st carriage that unitizes and
Is a second carriage composed of two reflecting mirrors.

FIG. 2 shows the structure of a scanning mechanism for scanning in the sub-scanning direction by moving the first carriage 11 and the second carriage 12 constituting the reading mechanism. In FIG. 2, 13 is a stepping motor. , 14 is an encoder having a built-in control mechanism for replacing the rotation speed of the stepping motor with the frequency of the pulse train and outputting the same, 15 is a magnet damper for reducing the natural vibration when the stepping motor is rotating, and 16 is the first carriage 11 and The drive transmission belt transmits the power of the stepping motor 13 so that the second carriage 12 is translated.

In the image reading apparatus thus constructed,
The document 2 to be read is placed on the platen glass 3. When a document reading start command is received from an external device (not shown), the control circuit 4 first causes the stepping motor 1 to operate.
3 is commanded to move the first carriage 11 to the home position, and the first mirror 7 in the first carriage 7 is moved.
Is stopped under the reference correction plate 5.

After this, with the light source 6 turned off, first, CC
Read the black shading data from the D sensor 10,
Write to the black shading memory in the control circuit 4.
This black shading data is used during image processing as correction data for removing dark level noise peculiar to the CCD sensor 10.

Subsequently, the light source 6 is turned on, the stepping motor 13 is step-operated, the white shading data is read from the CCD sensor 10 while scanning under the reference correction plate 5, and the white shading memory in the control circuit 4 is read. Write. The white shading data is used during image processing as correction data for removing light level noise (high frequency noise) peculiar to the CCD sensor 10 and low frequency distortion due to the optical system such as the light source 6 and the lens 9.

After that, the stepping motor 13 is step-operated while the light source 6 is turned on, the first carriage 11 is moved in the document reading direction 17, and scanning of the document (scanning in the sub-scanning direction) is started. This scanning is performed for the designated width by inputting a pulse train from the control circuit 4 to the stepping motor 13 and having a width comparable to the sub-scanning width of the read document. The operation at this time is called closed loop drive.

When the first carriage 11 scans a document at a constant speed, the CCD sensor 10 is controlled by a sync signal having a constant cycle called a horizontal sync signal. Then, the optical signal formed on the CCD sensor 10 is converted into an image electric signal and transmitted to the control circuit 4. At this time, the image electric signal is subjected to correction calculation processing and image editing processing with black shading data and white shading data written in the control circuit 4 in advance, and then transmitted to an external device (not shown).

As described above, by simultaneously performing the operation in the sub-scanning direction and the operation in the main scanning direction in the reading area of the original, the image information on the original can be continuously read. The first carriage 11 is mechanically configured so as to be controlled by receiving power from a stepping motor, which will be described later, so as to move at a speed twice that of the second carriage 12.

When the scanning of reading the document is completed, the first carriage 11 moves in the direction opposite to the document reading direction 17 and returns to the home position, and returns.
The light source 6 in the first carriage 11 is turned off to enter the standby state. Such a return operation is performed by the control circuit 4 operating the stepping motor 13 in the DC mode. When the stepping motor 13 is operated in the DC mode, the rotation speed is determined in proportion to the voltage supplied to the stepping motor 13, so a high voltage is supplied to the motor when performing high speed return. At this time, since the encoder 14 outputs the A-phase and B-phase column pulses, the column pulse is input to the control circuit 4 to detect the rotation state of the stepping motor 13 by detecting the phase and generating a quadruple pulse. While performing the control, the position of the carriages 11 and 12 is managed. Since the stepping motor 13 is controlled from the output pulse of the encoder 14, the operation at this time is called open loop driving.

When the home position is reached by such a return operation, the light source 6 in the first carriage 11 is turned off during the single-shot reading and the standby state is set, and the light source 6 in the first carriage 11 is turned on during the continuous reading. The above sequence is repeated by a command from an external device (not shown).

FIG. 3 shows a block configuration of a portion of the control circuit 4 which mainly controls the operations of the above-mentioned carriages 11 and 12. In FIG. 3, 20 is a CPU which controls the entire operation, and 21 is a CPU. RO that stores the control program
M and 22 are RAMs for working processing, and 23 is a CPU bus.

Further, in FIG. 3, 24 is a phase detection circuit, 25 is a quadruple multiplication circuit, 26 is a counter, and 27 is an I / O.
It is a port.

The phase detection circuit 24 is the A of the encoder 14.
By inputting the phase pulse and the B-phase column pulse, the phase of the column pulse is detected, and the rotation direction of the stepping motor 13, that is, the moving direction of the carriages 11 and 12 is detected. The carriage movement direction 28, which is the output signal of the phase detection circuit 24, is input to the counter 26 and the I / O port 27.

The quadruple multiplication circuit 25 is the A of the encoder 14.
Phase-multiplied pulses are generated by inputting the phase and B-phase train pulses, and the rotation amount of the stepping motor 13, that is, the moving distance of the carriages 11 and 12 is detected. The output signal 29 of the quadruple multiplication circuit 25 is input to the counter 26.

The counter 26 counts the number of pulse trains by inputting the carriage movement direction 28 and the output signal 29 from the quadrupling circuit 25, which are the output signals from the phase detection circuit 24 thus input. The carriage movement amount 30, which is the output signal of the counter 26, is
Input to O port 27 and CP via CPU bus 23
Sent to U20.

In FIG. 3, 31 is a stepping mode excitation signal generator, 32 is a DC mode excitation signal generator, 33 and 34 are FET drivers, 35 and 36 are power amplifiers, 37 is a motor drive power supply, 38 is a constant current control unit, 3
Reference numeral 9 is a comparison unit, and 40 is a current setting unit.

Stepping mode excitation signal generator 31
Generates an excitation waveform for operating the stepping motor 13 in step mode, is connected to the CPU bus 23, and is controlled under the control of the CPU 20. The generated signal from here is input to the FET drive unit 33.

The FET drive section 33 is controlled by the constant current control section 38. The output signal of the FET drive unit 33 is input to the power amplification unit 35, and power is amplified to operate the stepping motor 13 in the step mode.

The DC mode excitation signal generator 32 is for generating an excitation waveform for operating the stepping motor 13 in the DC mode, is connected to the CPU bus 23, and is controlled by the CPU 20. The generated signal from here is input to the FET drive unit 34.

The FET drive section 34 is controlled by the constant current control section 38. The output signal of the FET drive unit 34 is input to the power amplification unit 36 to drive the stepping motor 13 to D
It is power amplified to operate in C mode. The power amplifier 36 is connected to the CPU bus 23 and is controlled by the excitation voltage control signal 41 directly under the control of the CPU 20.

The comparison unit 39 compares the current setting value from the current setting unit 40 with the current value of the power amplification unit 35 or the power amplification unit 36, and inputs the result to the constant current control unit 38. Then, the constant current controller 38 controls the FET drivers 33 and 34 with reference to this result.

Further, the motor driving power source 37 supplies electricity to the stepping motor 13 via the power amplifiers 35 and 36.

Next, the carriages 11 and 1 for single-shot reading
The sequence operation of No. 2 will be described.

When the CPU 20 receives an original reading start command from an external device (not shown), the CPU 20 outputs a step mode operation signal to the stepping mode excitation signal generator 31, and the stepping mode excitation signal generator 31 generates a step excitation waveform. Let This step excitation waveform is amplified by the power amplifier 35 via the FET driver 33,
It is supplied to the stepping motor 13 to drive the stepping motor 13. Then, by rotating the stepping motor 13 a predetermined number of times in a predetermined direction, the first carriage 11 is moved to a home position position (not shown), and the first mirror 7 in the first carriage 11 is positioned below the reference correction plate 5. .. Since the light source 6 has already been turned on, the white reference correction data is read, stored in the correction data memory in the control circuit 4, and the reading is completed. After that, the stepping motor 13 is step-operated while the light source 6 is on, the first carriage 11 is moved in the document reading direction 17, and scanning of the document 2 on the document glass 3 is started.

That is, the CPU 20 determines the scanning width of the original document from the table of the ROM 21 in advance according to the size of the original document 2 on the original glass 3, and gives an operation instruction to the stepping mode excitation signal generating section 31 to excite the stepping mode excitation signal. The signal generator 31 supplies a pulse train corresponding to the width of the sub-scan of the read document 2 to the stepping motor 13 so that the first carriage 11 scans the designated width. When the scanning of the document is completed, the CPU 20 gives a stop instruction to the stepping mode excitation signal generator 31 to stop the stepping motor 13.

Next, the CPU 20 instructs the DC mode excitation signal generator 32 to operate in the DC mode, and causes the DC mode excitation signal generator 32 to generate a DC excitation waveform. The DC excitation waveform is amplified by the power amplifier 36 via the FET driver 34 and supplied to the stepping motor 13. As a result, the stepping motor 13 is driven by DC operation, and the carriages 11 and 12 start moving in the direction opposite to the document reading direction 17.

When the stepping motor 13 is operated by DC, the rotation speed is determined in proportion to the voltage supplied from the motor driving power source 37 to the power amplifying unit 36, so that the CPU 20 excites the power amplifying unit 36. By controlling through the voltage control signal 41, it is possible to perform operations such as start of the stepping motor 13, variable speed at low and high speeds, braking, or stop. At the time of starting the carriage, the CPU 20 controls the power amplifier 36 to increase the voltage, thereby rotating the stepping motor 13 at high speed and returning the carriage at high speed.

At this time, A output from the encoder 14
The phase and B phase train pulses are input to the phase detection circuit 24,
The moving direction signal 28 from the phase detection circuit 24 is input to the I / O.
The CPU 20 reads the data through the port 27 and detects the rotation direction of the stepping motor 13, that is, the movement direction of the carriage.

By inputting the A-phase and B-phase column pulses to the quadruple multiplication circuit 24, a quadruple-multiplied pulse is generated and input to the counter 25, and the output signal 28 of the phase detection circuit 24 is input to the counter 26. By controlling the counter 25 by doing so, the rotation amount of the stepping motor 13, that is, the moving distance of the first carriage 11 from the home position position is counted. This counting result is output as the carriage movement amount signal 30, and CP
The U 20 reads the carriage movement amount signal 30 via the I / O port 27.

As described above, the CPU 20 detects the carriage movement direction signal 28 and the carriage movement amount signal 30 via the I / O port 27, thereby managing the movement of the carriages 11 and 12 with the home position position as a reference point. It is carried out. At this time, the CPU 20 causes the counter 26 to
When it detects that the value of the movement amount signal 30 from the stepping motor 13 has reached a preset predetermined value, the power amplifier 36 is controlled to lower the voltage, and thereby the stepping motor 13
The rotation of the is gradually reduced, and smooth braking is applied to the return speed of the carriage.

In this way, the stepping motor 13
Driving in DC mode and open loop control
The first carriage 11 is quickly and accurately returned to the home position. Then, the light source 6 of the first carriage 11 is turned off to enter the standby state. Further, during continuous reading, the light source 6 of the first carriage 11 is kept on and the above sequence is repeated in response to a command from an external device.

As described above, according to the image reading apparatus of this embodiment, when the carriages 11 and 12 are returning, the CPU 20 controls the stepping motor 13 to DC.
By driving in a mode and performing open loop control, the carriages 11 and 12 can be moved at high speed and smoothly and accurately stopped at a predetermined position. Therefore,
By reducing the time of the document reading sequence, it is possible to shorten the image information input time to the image editing complex system or the like using the image reading device as a terminal, and to speed up the process.

[0043]

As described above, according to the present invention, the carriage constituting the reading mechanism can be quickly and accurately returned to the predetermined start position, and the processing speed in the image processing system can be increased. it can.

[Brief description of drawings]

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

2 is a diagram showing a configuration of a drive system mechanism of the image reading apparatus of FIG.

FIG. 3 is a diagram showing a configuration of a motor control unit of the image reading apparatus shown in FIG.

[Explanation of symbols]

 1 Image Reading Device Main Body 2 Original Document 3 Original Platen Glass 4 Control Circuit 5 Reference Correction Plate 6 Light Source 7 First Mirror 8 Second Mirror 9 Lens 10 Photoelectric Conversion Element (CCD Sensor) 11 First Carriage 12 Second Carriage

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Sakakibara 70 Yanagicho, Sachi-ku, Kawasaki-shi, Kanagawa, Toshiba Intelligent Technology Co., Ltd. Within Terrigent Technology Co., Ltd.

Claims (1)

[Claims] 1. A document scanning unit having a reading mechanism for reading a document and a scanning mechanism using a stepping motor as a drive source, and driving control of the stepping motor in a step mode so that the document scanning unit scans the document. Scanning control means for executing the above, detecting means for detecting the scanning direction and moving distance of the document scanning means, and adjusting the power supply amount to the stepping motor while referring to the detection signal from the detecting means, and open loop An image reading apparatus comprising: return control means for returning the document scanning means to a predetermined position by control.