JPH07236032A - Page scanner device - Google Patents

Abstract

(57) [Summary] [Object] To provide a scanner device capable of high-speed reading by effectively utilizing a linear encoder and controlling the maximum speed and stop position of a driving means. A line image reading sensor that outputs an image signal according to a line image, a scanner head unit for moving a reading position on the document surface of the image reading sensor in the frame direction, and a movement amount of the scanner head unit are directly set. And a linear encoder for detecting, which reads line images repeatedly at substantially equal intervals according to the position information from the linear encoder, regardless of the moving speed of the scanner head, and the scanner head according to the output of the linear encoder. The speed control of the drive means is performed, and the stop position control of the scanner head drive means is performed according to the linear encoder output in addition to the first means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device, and more particularly to a page scanner device which can be used in a scanner, a digital copying machine, a fax machine or the like.

[0002]

2. Description of the Related Art Generally, a digital image reading apparatus exposes a document and reads an image by detecting a reflected light reflected on the surface of the document with an optical sensor such as a CCD. Therefore, in order to faithfully reproduce the image information, it is necessary to accurately drive the scanner head unit at a constant speed and perform the reading operation at equal time intervals to realize line image reading at equal intervals. Therefore, the drive means of the scanner head unit includes a speed control circuit, a speed detecting means,
There is a problem in that high-precision driving force transmission means and the like are required, and the cost is inevitably high.

FIGS. 6A, 6B and 7C are diagrams showing an example of a scanner device of a scanner head moving type, an operation diagram and a timing diagram of read signals which have been conventionally used. As shown in FIG. 1A, the scanner device comprises a scanner head unit 1, a mirror base unit 2, guide means 3a and 3b, a line image reading sensor 4, a drive motor 5, a home position sensor 6 and a drive wire 7. Although the drive motor is expensive, a DC servo motor that can be driven at a constant speed is used. In the scanner device configured as described above, the scanner head unit 1 stands by at the home position, and when the DC servomotor 5 is activated, the scanner head unit 1 slides on the guide units 3a and 3b to read the image information.

As shown in FIG. 5 (b), the scanner head unit 1 is driven by the DC servo motor 5 and is accelerated to the scan speed while passing through the acceleration regions P to R, and is uniformly moved in the scan regions R to S. To drive. After passing through the scan area, the vehicle decelerates and stops in the deceleration areas S to U. The scanner having such a configuration generally requires an acceleration / deceleration region of about several tens of mm, which causes a problem of increasing the size of the device. On the other hand, the return operation of the scanner head unit is devised to return to the home position as quickly as possible by maximizing the function of the motor. In the scanner device shown in FIG. After moving to (distance L) at high speed, it moves to the sensor detection position Q at a low speed capable of maintaining accuracy, and a stop operation is performed so as not to cause an error. Therefore, in order to ensure the accuracy of the stop position, there have been problems such as an increase in the return time and complicated control.

Further, when a CCD is used as the reading sensor 4, the incident light is converted into an electric signal based on a scanning operation, the electric signal is once moved into a shift register by a shift pulse, and then serialized by a transfer clock. The image data is extracted in the form of voltage. That is, since the image reading is performed when the shift pulse is given, as shown in FIG. 7C, the moving speed of the scanner head unit 1 is made as constant as possible in the scan region, and the line image is not read. It was necessary to generate shift pulses at equal time intervals using the read clock.

Another reading device is disclosed in Japanese Patent Laid-Open No. 61-5.
Japanese Patent No. 9322 discloses an invention in which a rotary encoder is attached to a motor shaft that drives a scanner head unit to obtain a braking start position at the time of a return operation to speed up the return operation. On the other hand, JP-A-64-
Japanese Patent No. 55275 discloses an invention in which a linear encoder is applied to detect a print portion position of a recording apparatus.

However, in the above-mentioned inventions including the page scanner device which has been generally used, the position detection by the linear encoder is merely applied to the detection of the printing portion of the recording device. None were used for image reading. Further, since a handy scanner or the like is not required to have a high reading accuracy, there is a method of finding the reading position by a rotary encoder, but in a highly accurate digital image reading device, the reading position is found by using a rotary encoder. There is a problem that it is difficult.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and in particular against the background of the recent introduction of a technique for providing a highly accurate linear encoder at a low price, a linear encoder It is an object of the present invention to provide a scanner device capable of high-speed reading by effectively utilizing the above, and controlling the maximum speed and stop position of the driving means.

[0009]

To achieve this object, a first means of a page scanner device according to the present invention is a line image reading sensor for outputting an image signal according to a line image,
A scanner head unit for moving the reading position on the document surface of the image reading sensor in the frame direction, and a linear encoder for directly detecting the moving amount of the scanner head unit, the moving speed of the scanner head unit. Regardless of the position, the line image is repeatedly read at substantially equal intervals according to the position information from the linear encoder. The second means is characterized in that, in addition to the first means, speed control of the scanner head driving means is performed according to the linear encoder output. The third means is
In addition to the first means, stop position control of the scanner head driving means is performed according to the linear encoder output.

[00010]

With the scanner device as described above, the first means uses the linear encoder for detecting the position of the scanner head to read without depending on the drive speed of the motor, which is necessary in the conventional scanner device. The acceleration / deceleration area of the scanner head that has been deleted can be deleted. In addition, since the second means is configured to control the motor drive speed by using the linear encoder for position detection of the scanner head, it is possible to speed up to near the maximum speed that can be read using an inexpensive drive source. The read image can be realized. Further, since the third means is configured to control the stop position of the motor by using the linear encoder for detecting the position of the scanner head, an inexpensive drive source can be used accurately and at high speed without incurring cost increase. It is possible to realize the image reading in which the stop operation can be performed.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A digital image reading apparatus according to the present invention will be described in detail below with reference to the embodiments shown in the drawings.
1 (a), 1 (b), and 2 (c) are a diagram showing a configuration of a digital image reading device according to the present invention, a diagram showing an operation diagram, and a diagram showing timing of a read signal, respectively. As shown in FIG. 1A, the scanner device according to the present invention, like the scanner device shown in FIG. 6A, has a scanner head unit 11, a mirror base unit 12, guide means 13a and 13b, and line image reading. Sensor 1
4, a drive motor 15, a home position sensor 16, and a drive wire 17, and further a magnetizing wire 18 along the guide means 13b, a magnetic encoder on the magnetizing wire 18 and interlocking with the scanner head unit 11. 19
Is equipped with.

As shown in FIG. 1B, the operation diagram of the scanner device constructed as described above is driven in the feed direction from the point P, the image area is set between the points R and S, and the conventional scanner device is used. The deceleration area such as is not set. That is, as shown in FIG. 2C, by using the position information directly provided by the magnetic encoder 19 regardless of the moving speed of the scanner head unit 11,
Instead of the conventional reading clock, the encoder output signal is used as a shift pulse generation source that executes image capturing, and equidistant reading is realized, thereby configuring equidistant reading. There is.

Therefore, a low-priced motor having no speed control function can be used as the motor 15 as the driving means, and the acceleration / deceleration area unlike the conventional scanner device is not required. It has an excellent effect in constructing and supplying at a low price. FIG. 3 is a block diagram of a drive circuit of another embodiment of the scanner device according to the present invention, which is a DC brush motor for performing speed control or stop position control of the scanner head drive means using a linear encoder output. The CPU 20 includes a position information signal from the linear encoder 19 and the home position sensor 1
6 is supplied, the CPU 20 generates CPU outputs Vs, A, B, C and D based on the two signals, and switches the switches 21 to 24 to drive the motor and to rotate the motor. It is configured so that the direction, braking operation and non-driving can be controlled.

That is, in the case of non-driving, the switches 21-
Signals A to D are not generated so that 24 is turned off, and when the motor is normally rotated, the switches 21 and 24 are turned on and the other switches are turned off.
0 outputs a signal. Further, the switches 22 and 23 are turned on for reversing the motor, and the switches 23 and 24 are turned on for braking.
PU works. Therefore, according to the position information from the linear encoder 19, the motor, which is the driving means, is rotated forward or backward, or the brake is operated, so that reading at equidistant intervals can be realized despite using an inexpensive motor. Is possible.

FIGS. 4 (a) and 4 (b) are a control flow chart of a drive voltage and a drive mode of a DC brush motor, which is a drive means when the speed of the scanner head drive means is controlled by using a linear encoder output. It is a figure showing an example of an operation diagram. First, the speed information read by the linear encoder is compared with a predetermined target speed, and the motor voltage is digitally switched to simply maintain the target speed as much as possible. As a control method, a PID control method, a fuzzy control method, or the like may be applied. The reason for controlling the speed of the driving means in this way is that even if a linear encoder is used, there is a scan upper limit speed at which line reading can be executed, and reading is not performed correctly at a speed exceeding this. Therefore, in a DC brush motor that does not have a speed control function, it is necessary to set the drive speed to a speed sufficiently lower than the scan upper limit speed, which is an obstacle to speeding up, because speed fluctuations are expected.

Therefore, for the speed control of the motor,
The high-precision PLL control method normally used in a DC servo motor or the like is not adopted, and the drive voltage of the DC brush motor is feedback-controlled in accordance with the speed information obtained from the linear encoder to perform the drive that substantially matches the scan upper limit speed. It has been realized in a stable manner. By controlling the speed of the driving means in this manner, the speed accuracy is insufficient, but a sufficient effect is obtained for the purpose of bringing the driving speed of the DC brush motor close to the scannable upper limit speed. It becomes possible to execute the high-speed scan very stably as compared with the case of performing the scan at a sufficiently low drive speed that does not exceed the scannable upper limit speed without performing the scan.

FIGS. 5A and 5B show examples of a DC brush motor drive voltage for controlling the stop position of the scanner head drive means using the linear encoder output, a control flow chart of the drive mode, and a motor operation diagram. It is a figure. The stop position control of the motor is an important control for avoiding a collision with the end block and ensuring the scan area surely. However, when using the drive means that allows the speed fluctuation as in the above-mentioned embodiment, the stop is controlled. It is expected that the position accuracy will deteriorate, and in order to avoid this deterioration of the stop position accuracy, it is necessary to suppress the drive speed to a lower level, which is an obstacle to speeding up.

Therefore, in the present embodiment, it is possible to prevent the deterioration of the stop position accuracy by performing the simple control of braking the motor by judging from the home position sensor and the linear encoder output count that the motor has approached the stop position. As other means, PID control or fuzzy control may be applied for the purpose of improving the stop position accuracy. That is, by converting the relative position information obtained from the linear encoder 19 into an absolute position based on the home position sensor 16, the start timing of the stop operation is determined and the brake operation is performed, so the scan speed is set to a high speed. Even in such a case, it is possible to reduce the deterioration of the stop position accuracy with respect to the fluctuation of the motor speed, and it is possible to provide stable high-speed scanning.

[0019]

As described above, according to the present invention, the linear encoder for detecting the position of the scanner head is used so that the reading can be performed without depending on the driving speed of the motor. The area can be deleted, miniaturization can be achieved, and a remarkable effect is achieved in realizing image reading using an inexpensive drive source. In addition, according to the second embodiment of the present invention, the linear encoder for detecting the position of the scanner head is used to control the drive speed of the motor, so that an inexpensive drive is achieved without increasing the cost. It is extremely effective in realizing high-speed image reading near the maximum speed that can be read using a source. Further, according to the third embodiment of the present invention, the linear encoder for detecting the position of the scanner head is used to control the stop position of the motor. A remarkable effect is achieved in realizing image reading in which a stopping operation can be accurately performed at high speed using a power source.

[0020]

[Brief description of drawings]

FIG. 1A is a diagram showing a configuration of a digital image reading device according to the present invention, and FIG. 1B is a diagram showing an operation diagram of the digital image reading device according to the present invention.

FIG. 2C is a diagram showing a timing of a read signal of the digital image reading apparatus according to the present invention.

FIG. 3 is a diagram showing a drive circuit block diagram of a DC brush motor that performs speed control or stop position control of a scanner head drive unit using a linear encoder output in the scanner device according to the present invention.

FIG. 4A is a control flowchart diagram of a drive voltage and a drive mode of a DC brush motor when speed control of a scanner head drive unit is performed using a linear encoder output, and FIG. 4B is a motor operation of the DC brush motor. The figure which showed an example of the diagram.

FIG. 5A is a control flowchart diagram of a drive voltage and a drive mode of a DC brush motor that controls a stop position of a scanner head drive unit by using a linear encoder output;
(B) The figure which showed the example of the motor operation diagram of the DC brush motor which performs stop position control.

FIG. 6A is a diagram showing a configuration of a conventionally used scanner head moving type scanner device, and FIG. 6B is a diagram showing an operation diagram of a conventionally used scanner head moving type scanner device. .

FIG. 7C is a diagram showing an example of a timing chart of an image reading signal of a scanner device of a scanner head moving type which is conventionally used.

[Explanation of symbols]

11 ... Scanner head part, 12 ... Mirror base part, 13a, 13b ... Guide means, 14 ... Line image reading sensor, 15 ... Drive motor,
16 ... Home position sensor, 17 ... Drive wire, 18 ... Magnetizing wire, 19 ... Magnetic encoder (linear encoder).

Claims (3)

[Claims] 1. A line image reading sensor that outputs an image signal according to a line image, a scanner head unit for moving a reading position of the image reading sensor on a document surface in a frame direction, and a scanner head unit of the scanner head unit. A linear encoder for directly detecting the amount of movement, characterized in that line images are repeatedly read at substantially equal intervals according to position information from the linear encoder, regardless of the moving speed of the scanner head section. Page scanner device. 2. The page scanner device according to claim 1, wherein speed control of the scanner head driving means is performed according to the output of the linear encoder. 3. The page scanner device according to claim 1, wherein the stop position control of the scanner head driving means is performed according to the output of the linear encoder.