JP2665415B2 - Image reading device magnification error correction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnification error correcting method for automatically correcting a magnification error in the sub-scanning direction caused by a variation in the original feeding speed in an original reading type image reading apparatus.

2. Description of the Related Art In a moving original image reading apparatus for reading an image while moving an original or an original reading and moving / fixing original image reading apparatus, originals are pulled out one by one from a hopper and fed to an image reading section. Reading is performed at a speed, but the document feeding speed is likely to deviate from the standard speed due to variations in the mechanical accuracy of the document feeding system and changes in temperature. The deviation of the feeding speed appears as expansion and contraction of the read image in the sub-scanning direction, that is, a magnification error. The present invention provides a method for automatically correcting the magnification error in the sub-scanning direction.

[0003]

2. Description of the Related Art FIG. 5 shows the structure of a mechanism section of a conventional original moving image reading apparatus. In the figure, 1 is a hopper, 2 is a document, 3 is a pad, 4 is a pick roller, 5 and 6 are feed rollers, 7 and 8 are driven rollers, 9 is a reading unit, and 10 is a document feed path.

The pick roller 4 is rotated counterclockwise, and the feed rollers 5 and 6 are rotated clockwise by motors (not shown). The pad 3 is pressed against the pick roller 4, and when the pick roller 4 is rotated counterclockwise, one of the lowermost layers of the document 2 loaded on the hopper 1 is pulled out, and the feed roller 5
Sent to the side. The document is drawn between the feeding roller 5 and the driven roller 7 and is sent out to the feeding roller 6 and the driven roller 8 side. Then, the leading end of the document is drawn into the feed roller 6 and the driven roller 8, and the document is fed at a constant speed over the reading unit 9 in the sub-scanning direction by the two sets of the feeding roller and the driven roller. , And the image is read.

In general, rubber rollers are used for the feed rollers 5 and 6, and it is difficult to obtain processing accuracy, and the diameter changes due to thermal expansion and contraction due to temperature, so that the feed amount with respect to the rotation amount varies. It's easy to do. On the other hand, there are solutions to use a metal roller instead of the rubber roller or to reduce the thickness of the rubber portion of the rubber roller. However, all of these methods have a problem in that the cost is increased. Furthermore, if the number of originals loaded on the hopper is large, a large back pressure is applied to the feeding force of the feeding roller, and the friction coefficient of the pad also varies, and there is a fluctuation due to environmental influences. It was easy to deviate from the standard value.

[0006]

In the conventional original moving image reading apparatus, there is a variation in the original feeding speed and a fluctuation due to the environment, and a magnification error occurs in the sub-scanning direction. Also, problems such as a decrease in the recognition rate in the character recognition processing have occurred.

It is an object of the present invention to detect a deviation of a document feeding speed from a standard value and automatically correct a magnification error based on the deviation.

[0008]

SUMMARY OF THE INVENTION The present invention measures the time during which a document is fed in a measurement section of a fixed distance in a feeding path in the form of the number of driving pulses of a feeding motor. From the standard document feed distance per unit drive pulse, the distance to which the original should be fed is determined, and the magnification error is determined from the distance of the known measurement section, and the feed motor is driven so that the magnification error is eliminated. It changes the pulse frequency.

FIG. 1 is a principle diagram using one embodiment of the present invention. In FIG. 1, 3 is a pad, 4 pick rollers,
5 and 6 are feed rollers, 7 and 8 are driven rollers, 9
Is a reading unit, 10 is a document feeding path, 11 is a feed motor, 12 is a belt, 13 is a motor drive control unit, 14 is a variable pulse source, 15 and 16 are detection sensors, 17 is a drive pulse number counter, and 18 is a drive pulse number counter. This is a magnification error correction processing unit.

The paper feed motor 11 includes a motor drive control unit 13
And the feed rollers 5 and 6 are simultaneously rotated via the belt 12. Motor drive control unit 13
Operates based on a clock pulse from the variable pulse source 14 that can change the pulse frequency. Detection sensor 15,
Reference numeral 16 may be a transmission type or a reflection type, and is provided at a fixed interval S between the feeding rollers 5 and 6.

The document fed by the pick roller 4 is received by the feed roller 5 and fed to the reading unit 9 at a constant speed. When the leading edge of the document is detected by the detection sensor 15, the drive pulse number counter 17 starts counting the drive pulses in the motor drive control unit 13. Next, when the leading edge of the document is detected by the detection sensor 16, The drive pulse number counter 17 stops counting. The count value P during this time is passed to the magnification error correction processing unit 18.

The magnification error correction processing section 18 calculates the count value P
Then, a magnification error b = (Pa−S) / S in the sub-scanning direction is calculated from the known distance S between the detection sensors and the standard document feeding distance a per unit driving pulse, and further, the driving pulse frequency of the motor is calculated. Finding the correction coefficient (1 + b) for Z,
In order that the driving pulse frequency becomes Z ′ = (1 + b) Z,
The variable pulse source 14 is controlled.

[0013]

In FIG. 1, when the feeding speed is higher than the standard value, the distance S between the detection sensors is reduced with a small number of driving pulses P.
Is read, the read image is reduced in the sub-scanning direction, and the magnification error becomes negative. Therefore, the magnification error correction processing unit 18 controls to lower the drive pulse frequency Z to lower the feeding speed.

On the other hand, if the feeding speed is lower than the standard value, the state is reversed, and the magnification error becomes positive,
Control is performed such that the driving pulse frequency is increased and the feeding speed is reduced.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the explanation of the principle of the present invention shown in FIG. 1, a magnification error is calculated using the distance S between detection sensors. However, the value of S may vary due to a mounting error of the detection sensor.

At the time of product shipment, as shown in FIG.
A standard manuscript 19 in which two marks A and B are written at an interval of a distance x defined in the sub-scanning direction of the manuscript is prepared and fed, and the marks A and B are detected by the detection sensor 16 in FIG. The number of drive pulses y of the motor during the detection is counted.
Further, the leading edge of the document is detected by the detection sensors 15 and 16 to determine the count value P of the number of drive pulses, C = y / P is calculated as a constant unique to the apparatus, and stored in the EEPROM of the apparatus.

Since the value of C corresponds to the value of x / S, S
= X / C, and the above-described equation of the magnification error is as follows: b = (P · a−S) / S = (CP · a−x) / x Thereby, the magnification error is calculated without using S,
Control of the pulse drive frequency Z can be performed.

FIG. 3 shows an embodiment in the case of an image reading apparatus of the type for moving and fixing a document. In this case, the detection sensors 15 and 16 in FIG. 1 are unnecessary, and instead, the reading unit is moved between the two corresponding detection positions to detect the leading edge of the document, and counts the number of motor drive pulses during that time. .

In FIG. 3, 2 is an original, 4 is a pick roller, 5 and 6 are feed rollers, 7 and 8 are driven rollers, 20 is a reading unit carrier, and 21 is a platen glass. Points A and B on the platen glass 21 indicate two positions for detecting the leading edge of the document.

First, as shown in FIG. 3A, the carrier 20 is stopped at the detection position of the point A,
The leading edge of the fed document is detected. When the leading edge of the document is detected, counting of the number of drive pulses of the motor is started as in the case of FIG.

Next, the carrier 20 is moved to the point B before the leading end of the document reaches the point B, and stopped in the state shown in FIG. When the leading edge of the document is detected at point B, the counting of the number of driving pulses is stopped, and the number of driving pulses required for feeding between A and B is obtained. Later magnification error correction processing
1 and 2 can be applied.

FIG . 4 is a bottom view of the platen glass 21 of FIG.
And the positions of point A and point B outside the reading range
Is provided with a mark. The carrier 20
The stop position is controlled by detecting the shock. First career at point A
20 stops, detects the leading edge of the document, and then feeds the document.
Moves to point B faster than normal and stops, leading edge of document arrives
Wait to do .

At point B, carrier 20 detects the leading edge of the document
Then, using the count value P, the motor drive pulse described above is used.
Correct the magnification error to change the frequency and adjust the feeding speed.
After the correction, the image is read by the carrier 20 at the point B.
Start sampling.

[0024]

According to the present invention, an original moving type image reading
Document feeding using an inexpensive rubber roller.
Even if you do it, low cost without putting a heavy burden on adjustment
Can easily correct the sub-scanning magnification error.
High-quality image reading is always possible even for environmental changes
Can be used for character recognition and image processing.
To improve the recognition rate and increase the accuracy of the image cropping position.
Which effect can be obtained.

[0025]

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is an explanatory diagram of one embodiment of the present invention.

FIG. 3 is an explanatory diagram of another embodiment of the present invention.

FIG. 4 is an explanatory view of a platen glass according to another embodiment of the present invention.

FIG. 5 is a configuration diagram of a mechanism section of a conventional original moving image reading apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 3 pad 4 pick roller 5, 6 feed roller 7, 8 driven roller 9 reading unit 10 document feed path 11 paper feed motor 12 belt 13 motor drive controller 14 variable pulse source 15, 16 detection sensor 17 drive pulse counter 18 Magnification error correction processing unit

Claims (1)

(57) [Claims] 1. A method of correcting a magnification error of a moving document type image reading apparatus which automatically feeds a document to a predetermined image reading position and reads an image, comprising the steps of: A means for measuring the number of drive pulses of the motor required for feeding is provided, and each time a document is fed, the means is provided at a predetermined distance along a path on the platen glass where the document is fed using the means. The reading unit carrier is sequentially stopped at each position of the mark,
The leading edge of the document is detected at each position, the number of motor drive pulses between each detection time is counted, and the number of motor drive pulses required to feed the document in a section of a predetermined distance in the document feed path is calculated. measured, and the value of the measurement results, and the value of the predetermined distance of said interval, calculating a sub-scanning direction magnification error based on the value of the document feeding distance per known unit driving pulse, calculated magnification A magnification error correction method for an image reading apparatus, comprising: changing a driving pulse frequency of a motor to a value that eliminates an error, controlling document feeding, and correcting a magnification error in a sub-scanning direction.