JPH09224129A - Image input device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To deal with the fluctuation of inclination quantity with simple structure even in the case of fluctuating the inclination quantity during reading by detecting the inclination of an original based on the position of the original detected from the area of shadow existent near the outer edge of the original and correcting the inclination. SOLUTION: Concerning a device with which the reflected light of light radiated to an original 1 to be conveyed is detected by an image sensor (CCD) 13 and image information is read, this device is provided with a reflection panel 8 having a reflection plane 9 with reflectance practically equal with that of the original so as to be wider in a main scanning direction perpendicular to a conveying direction than the most inclined original on the back side of the original 1 at a light radiation part. A separation circuit 18 and an inclination detection circuit 19 detect the area of shadow existent near the outer edge of the original on the reflection plane 9 from the original surface of the original 1 detected by the CCD 13 and the reflected light on the reflection plane 9, the position of the original 1 in the main scanning direction is detected from this area of shadow, the inclination of the original 1 is detected based on this position of the original 1 and based on this detection output, an inclination correcting mechanism corrects the inclination of the original 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image input device applied to a facsimile device, a digital copying machine, an optical character recognition (OCR) device and the like, and more particularly to an improvement of means for correcting skew of a document.

[0002]

2. Description of the Related Art Image input devices of this type are generally
Irradiate light on the original conveyed on the light irradiation part,
Image information is read by detecting the reflected light with an image sensor.

Here, the original document may be skewed depending on how the operator sets the original document and the mechanism accuracy of the transport roller in the transport mechanism section. If the original is skewed, OC
There are problems that the recognition rate of the recognition processing such as R and OMR decreases, and that the display is difficult to see on an image input device such as an image scanner. On the other hand, in this type of device,
It is effective to detect the skew amount of the document and correct the recognition process or the image information.

For example, in Japanese Unexamined Patent Publication No. 5-176133, it is checked whether the leading edge of a conveyed document is detected first by either the first or second sensor (a configuration different from the image sensor). No matter which sensor is detected first, it starts counting the number of steps of the stepping motor,
There is disclosed an image input device that stops counting when another sensor detects the leading edge of a document and obtains the skew angle of the document based on the count value of the number of steps at this time.
Further, in Japanese Patent Laid-Open No. 63-65765, independent rollers located at both ends of a document and a detector that detects arrival of the left and right leading ends of the document and generates a reach signal (a configuration different from the image sensor). An image input device having and is disclosed.

As described above, the conventional image input device has a structure in which the skew amount of the document is detected only at the leading edge of the document and the skew of the entire document is corrected according to the detected skew amount. .

[0006]

In the conventional image input device, two sensors are installed coaxially in the main scanning direction of the document (generally, a direction perpendicular to the conveying direction), and each sensor has a leading edge of the document. Since the skew feeding amount is obtained from the time difference until the detection of “A”, only the skew feeding amount at the leading edge of the document is detected. For this reason, there is a problem in that it is not possible to deal with the case where the skew amount changes during reading due to the eccentricity of the conveying roller, the slip of the document, and the like.

Further, in the conventional image input apparatus, since a sensor dedicated to the skew feeding detection is used, the skew feeding detection accuracy is affected by the mounting position accuracy of the sensor and the performance of the operating characteristics of the sensor. In order to perform skew correction with high accuracy, it is necessary to maintain high mechanical accuracy.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image input device having a skew correction function which can cope with a case where the skew amount varies during reading.

Another object of the present invention is to provide an image input device having a simple structure that does not exhibit a special structure for skew correction that is complicated and requires maintaining mechanical accuracy.

[0010]

According to the present invention, an image input device for reading image information by irradiating a document conveyed on a light irradiating section with light and detecting the reflected light by an image sensor. In the light irradiation part, the reflection is provided so as to be wider in the main scanning direction perpendicular to the conveyance direction than the virtually skewed original on the background side of the original and has substantially the same reflectance as the original. A reflecting plate having a surface, a document surface detected by the image sensor and a reflected light from the reflecting surface to detect a shadow region existing near the outer edge of the document on the reflecting surface, and in the main scanning direction from the shadow region. A skew detection unit that detects the position of the document and detects skew of the document based on the position of the document, and a skew correction mechanism that corrects skew of the document based on the output of the skew detection unit. Characterized by having That image input device can be obtained.

According to the present invention, the skew feeding detecting section is
Among reflected lights having a width lower than a predetermined reflected light level and not less than a predetermined width, a portion existing on the outermost side in the main scanning direction on the reflecting surface is detected as the shadow area. The image input device is obtained.

Further, according to the present invention, the skew feeding correction mechanism independently drives a pair of conveying rollers which are coaxially arranged in the main scanning direction of the document with a space therebetween and the pair of conveying rollers. The image input device includes a pair of feed motors and a motor control unit that controls the number of rotations of each of the pair of feed motors based on the output of the skew detection unit.

[0013]

According to the present invention, the skew amount is detected from the shadow of the document formed on the reflection surface, so that the skew amount can always be detected during the reading of the document.

Further, since the shadow of the original is detected by using the means for reading the image information of the original, it is not necessary to add a sensor dedicated to the skew feeding correction, maintenance of the mechanism accuracy, etc. Detection accuracy does not deteriorate.

[0015]

DETAILED DESCRIPTION OF THE INVENTION An image input device according to an embodiment of the present invention will be provided below with reference to the drawings.

FIG. 1 is a block diagram showing an image input device according to an embodiment of the present invention, and FIG. 2 is a schematic top view of the document reading section in FIG. 1 and 2
With reference to, the present image input device irradiates the original 1 conveyed on the light irradiating section of the original reading section with light from the light source 10 and detects the reflected light by the CCD 13 as an image sensor. This is a device for reading image information. Further, the present apparatus is provided wider in the main scanning direction perpendicular to the conveyance direction of the original 1 than the original 1 which is virtually skewed on the background side of the original 1 in the light irradiation section, and the original 1 Reflective surface 9 having substantially the same reflectance as
Main scanning by detecting the shadow area existing in the vicinity of the outer edge of the original 1 on the reflecting surface 9 from the light reflected from the original surface of the original 1 and the reflecting surface 9 of the reflecting plate 8 detected by the CCD 13 and the reflecting plate 8 having And a skew feeding correction mechanism that corrects the skew feeding of the document 1 based on the output of the skew feeding detection unit. ing.

In the present embodiment, the skew feeding detecting section includes a separating circuit 18 and a skew feeding detecting circuit 19, which will be described later.

The skew feeding correction mechanism is paired with a left-side conveying roller 2 and a right-side conveying roller 4 (upper and lower pairs) which are a pair of conveying rollers provided on the same axis in the main scanning direction of the document 1 at intervals. Left conveying motor 3 and right conveying motor 5 (a pair only on the upper side), which are a pair of conveying motors that independently drive the conveying rollers 2 and 4, respectively, and the skew detection circuit 1.
The motor control unit 20 controls the rotation speed of each of the pair of transport motors 3 and 5 based on the output of the motor 9.

The apparatus also has a discharge roller 6 for discharging the document 1 and a discharge motor 7 for driving the discharge roller 6.

Next, the overall structure of this apparatus and the flow of signals will be described more specifically.

The original 1 is conveyed by the left side conveying roller 2 and the right side conveying roller 4 and reaches the reflecting plate 8. Here, the left-hand side transport roller 2 and the right-hand side transport roller 4 are coaxially arranged in the main scanning direction of the document 1 with a space therebetween, and are independently driven by the left-hand side transport motor 3 and the right-hand side transport motor 5, respectively.

The reflection plate 8 has a reflection surface 9 having substantially the same reflectance as the original surface of the original 1. The light emitted by the light source 10 is reflected by the document surface of the document 1 passing on the reflecting surface 9 of the reflecting plate 8, and is reflected by the mirror 11 and the lens 12.
It is incident on the CCD 13 through.

The CCD output signal 101 from the CCD 13 to which light is incident is amplified by the amplifier 14 (amplifier output signal 102) and then input to the A / D converter 15. A /
In the D converter 15, the analog amplifier output signal 102
Is converted into, for example, an 8-bit digital signal. The light amount correction circuit 16 constantly monitors the overflow signal 103 of the A / D converter 15, and adjusts the amplification factor so that the input signal level of the A / D converter 15 is always constant regardless of the light amount fluctuation of the light source 10. The control signal 104 controls the amplification factor of the amplifier 14.

The digital A / D converter output signal 105 output from the A / D converter 15 enters the shading correction circuit 17 and the output level variation due to the position in the main scanning direction is corrected. The shading correction circuit output signal 106 output from the shading correction circuit 17 is
The signal enters the separation circuit 18 and is separated into the skew detection signal 107 and the image output signal 110. Skew detection signal 10
7 enters the skew detection circuit 19.

In the skew feeding detection circuit 19, the original document 1 is based on the difference between the reflected light from the original document surface and the reflecting surface 9 of the original document 1 and the reflected light from the shadow area of the original document 1 formed on the reflecting surface 9. The skew amount of the motor is detected and the skew information signal 108 is sent to the motor controller 2.
Output to 0.

In the motor control unit 20, the skew detection circuit 19
Based on the skew feeding information from, the motor control signals 109a and 109b are output to control the rotational speeds of the left side transport motor 3 and the right side transport motor 5 to correct the skew of the document 1.

Next, the skew feeding detection processing and skew feeding correction processing of the original 1 by this apparatus will be described in detail with reference to FIGS. 1 and 2 and FIGS. The skew detection processing includes a light amount correction step, a shading correction step, and a skew detection step.

[Skew detection process (light amount correction step)] The light amount of the light source 1 shown in FIG. 1 tends to decrease due to secular change, in addition to variations due to individual differences. In order to correct such a change in the light amount of the entire light source, it is necessary to perform the light amount correction in this type of device, but in the present invention, the light amount correction is performed by the method described below.

In FIG. 1, immediately before reading the original 1,
The reflecting surface 9 of the reflecting plate 8 is read. Here, since the reflecting surface 9 has substantially the same reflectance as the original 1 (generally white), the waveform of the CCD output signal 101 of the CCD I3 is the original 1 as shown in FIG. Is the maximum value that can occur when is read. On the other hand, the light amount correction circuit 16
While monitoring the overflow signal 103 of the A / D converter 10, the amplification factor of the amplifier 14 is gradually increased. When the overflow signal 103 is detected, the amplification factor is lowered by one step, and the reading of the original 1 is completed until the reading is completed. Maintain amplification rate. The waveform of the amplifier output signal of the amplifier 14 is shown in FIG.
(B).

With such an operation, the A / D converter 15
The peak value of the signal level that is input to is kept constant regardless of the light amount of the light source 10.

[Skew Detection Process (Shading Correction Step)] Generally, the light amount of the light source 10 in FIG. 1 is highest near the center and dark at both ends. Also,
Even in the process of passing through the mirror 11 and the lens 12, a slight change in the amount of light occurs due to the difference in optical path length. In order to correct such a variation in the light amount at each position in the main scanning direction,
In this type of device, shading correction needs to be performed, but in the present invention, it is performed by the method described below.

After the above light amount correction step is completed, the reflecting surface 9 of the reflecting plate 8 is read again. Since the reflectance of the reflecting surface 9 is uniform over the entire surface, the waveform of the A / D converter output signal 105 of the A / D converter 15 reflects the shading characteristics and is shown in FIG. become that way.

In the shading correction circuit 17, the A / D converter output signal 105 is normalized according to the position in the main scanning direction so that the output signal waveform becomes as shown in FIG. Keep this state until the end.

By such an operation, the signal level input to the separation circuit 18 is kept constant even if the light amount varies depending on the position in the main scanning direction.

[Skew Detection Process (Skew Detection Step)] The document 1 in FIG. 1 is skewed depending on how the operator sets the document 1 and the mechanism accuracy of the left side transport roller 2 and the right side transport roller 4. There are cases. If the original 1 is skewed, the recognition rate may be lowered in the recognition processing such as OCR and OMR, and the display may be difficult to see in an image input device such as an image scanner. Detect the line amount, correct the recognition process,
It is effective to correct the image information.

In the present invention, skew detection is performed by the method described below.

After the light amount correcting step and the shading correcting step are completed, the left side conveying roller 2 and the right side conveying roller 4 in FIG. 1 are rotated at the same number of revolutions to convey the original 1.

Since the width of the reflecting surface 9 in the main scanning direction is set to be wider than the width of the original document 1, when the original document 1 passes over the reflecting plate 8, the reflecting surface 9 is placed on the reflecting surface 9 depending on the thickness of the original document 1. There is a slight shadow. This shadow is output in the skew detection signal 107 from the shading correction circuit 17 as a waveform as shown in FIG. In FIG. 5A, the shadow region exists at the outermost position in the main scanning direction on the reflecting surface 9 of the portion having a level lower than the threshold value for skew detection and having a predetermined width or more. It corresponds to the part to do.

In order to detect the shadow area, the separation circuit 18 samples the input 8-bit signal with a threshold value as shown in FIG. 5 (a), and as shown in FIG. 5 (b). The skew detection circuit 19 converts the skew detection signal 107 into a skew detection signal 19
Output to At the same time, the separation circuit 18 converts the input 8-bit signal into a normal image output as shown in FIG.
Sampling is performed with a threshold for image output as shown in FIG. 5A, converted into a signal as shown in FIG. 5C, and output as an image output signal 110.

The skew feeding detection circuit 19 counts, for each main scanning line, the number of bits from the left end in the main scanning direction to the left end of the shadow of the original 1 in the signal waveform of FIG. The difference from the count value is output as skew information.
When the original 1 is not skewed, the count value is constant, so the skew information output value is 0. However, for example, when skew is rising to the right, the count value is As the skew information output value increases, the skew information output value becomes a positive value. On the contrary, when the skew is rising to the left, the count value decreases and the skew information output value becomes a negative value.

Further, even when a skew meandering to the left and right occurs on one sheet of original document 1, an arbitrary value from plus to minus is output as skew information, so that the skew state is accurately detected. can do.

[Skew Correction Processing] The motor controller 20 in FIG. 1 has the skew information signal 108 from the skew detection circuit 19.
Based on the above, the respective rotation speeds of the left side conveyance motor 3 and the right side conveyance motor 5 are determined. For example, when the skew feeding information output value is 0, since the skew feeding does not occur in the original document 1, the left conveyance motor 3 and the right conveyance motor 5 both have the same rotation speed. If the skew information output value is a positive value, the skew of the document 1 is increasing and the skew of the document 1 is increasing. Therefore, the rotation speed of the left transport motor 13 is increased or the rotation speed of the right transport motor 5 is decreased. Do either or both. On the other hand, when the skew feeding information output value is a negative value, the skew of the document 1 is rising to the left, so the rotation speed of the left side conveyance motor 3 is slowed down or the rotation of the right side conveyance motor 15 is rotated. Increase the number, or both. However, it is preferable to control so that the combined conveying speed of the left side conveying motor 3 and the right side conveying motor 5 is always constant so that unevenness in conveyance in the sub-scanning direction does not occur in the read image information. That is, it is preferable to perform control for adjusting both rotation speeds among the above-mentioned control. The speed of the discharge motor 7 that drives the discharge roller 6 for discharging the document 1 is also controlled to be equal to the combined transport speed of the left side transport motor 3 and the right side transport motor 5.

By such an operation, the original 1 is conveyed so that the skew is always 0 during the reading, so that the operator sets the original 1 at random, or the left side conveying roller 2 is changed due to aging or the like. Even if the mechanism accuracy of the right side transport roller 4 changes, the skew of the document 1 is automatically corrected.

[0044]

The image input device according to the present invention is provided so as to be wider in the main scanning direction at right angles to the conveying direction than the document which is virtually skewed on the background side of the document in the light irradiation section. In addition, a reflection plate having a reflection surface having substantially the same reflectance as the original, and the shadow area existing near the outer edge of the original on the reflection surface is detected from the original surface detected by the image sensor and the reflected light from the reflection surface. A skew detection unit that detects the position of the document in the main scanning direction from the shadow area and detects skew of the document based on the position of the document, and corrects skew of the document based on the output of the skew detection unit Since it has a skew feeding correction mechanism, it is possible to always detect skew while reading a document, and it is possible to cope with fluctuations in the skew amount during reading.
The skew of the original can be corrected with higher accuracy.

Further, the skew feeding can be detected by the device originally provided for reading the image information of the document without adding a detection mechanism such as a sensor exclusively for the skew feeding detection. As a result, it has a simple structure even though it has a skew correction function for the document. Also, since skewing is always detected during document reading and the result can be immediately fed back to the transport motor, even if the transport roller becomes eccentric due to aging or mechanical precision deteriorates, these can be automatically corrected. It is not necessary to keep the mechanical precision of the device extremely high.

[Brief description of drawings]

FIG. 1 is a block diagram showing an image input device according to an embodiment of the present invention.

FIG. 2 is a top view of a light irradiation section in the device shown in FIG.

FIG. 3 is an example of a signal waveform in a light amount correction step by the apparatus shown in FIG. 1, (a) shows a CCD output signal waveform, and (b) shows an amplifier output signal waveform.

FIG. 4 is an example of a signal waveform in a shading correction step by the apparatus shown in FIG. 1, where (a) shows an output signal waveform of an A / D converter and (b) shows an output signal waveform of a shading correction circuit. .

5 is an example of a signal waveform in a skew detection step by the apparatus shown in FIG. 1, (a) shows an output signal waveform of a shading correction circuit, and (b) shows an output signal waveform of a separation circuit (skew detection). Signal), and (c) shows an output signal waveform (image output signal) of the separation circuit.

[Explanation of symbols]

 1 Original 2 Left-handed Transport Roller 3 Left-handed Transport Motor 4 Right-handed Transport Roller 5 Right-handed Transport Motor 6 Ejection Roller 7 Emission Motor 8 Reflector 9 Reflective Surface 10 Light Source 11 Mirror 12 Lens 13 CCD 14 Amplifier 15 A / D Converter 16 Light Quantity Correction Circuit 17 Shading Correction Circuit 18 Separation Circuit 19 Skew Detection Circuit 20 Motor Control Section

Claims (3)

[Claims] 1. An image input device which reads image information by irradiating a document conveyed on a light irradiating unit with light and detecting the reflected light by an image sensor, wherein the background side of the document in the light irradiating unit is read. And the image sensor, which is provided so as to be wider in the main scanning direction perpendicular to the conveyance direction than the most obliquely skewed document, and which has a reflection surface having substantially the same reflectance as the document. The area of the shadow existing near the outer edge of the original on the reflective surface is detected from the reflected light of the original surface and the reflection surface detected by, and the position of the original in the main scanning direction is detected from the area of the shadow to detect the original. An image input device comprising: a skew detection unit that detects a skew of a document based on a position; and a skew correction mechanism that corrects a skew of a document based on an output of the skew detection unit. 2. The skew detection unit is a portion of reflected light having a width lower than or equal to a predetermined reflected light level and having a width equal to or larger than a predetermined level, which is located on the outermost side in the main scanning direction on the reflecting surface. The image input device according to claim 1, wherein is detected as the shadow area. 3. The skew feeding correction mechanism includes a pair of conveyance rollers provided coaxially with each other in the main scanning direction of the document at intervals.
It has a pair of conveyance motors that drive the pair of conveyance rollers independently, and a motor control unit that controls the number of revolutions of each of the pair of conveyance motors based on the output of the skew feeding detection unit. The image input device according to claim 1.