JPH0965061A - Image input device for detecting inclination of original - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cancel operational complex for performing light quantity correction or shading correction by providing a circuit for detecting the inclination of original corresponding to the shadow of original formed on a reflection plane, which is provided behind the original, having the almost same reflection factor as the original. SOLUTION: Just before reading an original 1, a CCD 8 reads a reflection plane 4. Since the reflection plane 4 has the same reflection factor as the original (generally in white), the output signal waveform of the CCD 8 becomes a maximum value to be generated when the original is read. When the overflow signal of an A/D converter 10 is detected, a light quantity correction circuit 11 decreases an amplification factor for one stage and keeps this amplification factor until the original is completely read. With this operation, the peak value of a signal level inputted to the converter 10 is kept constant regardlessly of the quantity of light from a light source 5.

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 capable of detecting skew of a document.

[0002]

2. Description of the Related Art Conventionally, when a document is read by an image input device using a CCD, a contact image sensor, etc., a non-reflective surface or a non-reflective reading roller is provided in the background of the document reading portion to Black) and original (white)
The structure is such that the skew feeding of the document is detected by detecting the fluctuation or deviation of the boundary position of the document.

[0003]

The first problem is that in the prior art, the operation becomes complicated or the structure becomes complicated.

The reason for this is that in an image input device that irradiates a document with light and reads image information by the reflected light, a decrease in the light amount of the entire light source due to aging is corrected, and variations in the light amount that differ depending on the position of the light source are corrected. Although it is necessary to perform correction (shading correction), in the conventional technology, the background of the document reading part is a non-reflective surface. Therefore, in order to perform light amount correction and shading correction, the same reflectance as a standard document is used. This is because it is necessary to read the reference document that the user has or to move the reference reflection surface to the document reading surface by providing a special mechanism. Alternatively, it is necessary to fix the reference reflecting surface at a position different from the original reading surface, irradiate the light from the light source toward the reference reflecting surface by moving the optical system, and read the reflected light.

[0005] The second problem is that in the prior art,
This means that the manuscript is easy to get dirty.

The reason for this is that in the prior art, the background of the document reading portion is a black non-reflective surface or a black reading roller that has been subjected to an anti-reflective treatment. The back of the is black and easily soiled. In particular, when the same document is repeatedly read, this tendency becomes remarkable due to accumulation of dirt.

It is an object of the present invention to eliminate the operational complexity of reading a reference original having the same reflectance as a standard original in order to perform light amount correction and shading correction.

Another object of the present invention is to eliminate the complexity of the apparatus structure in which the reference reflecting surface is moved to the original reading surface or the optical system is moved by providing a special mechanism.

Another object of the present invention is to eliminate the problem that the back surface of the document is black and easily soiled due to abrasion of the material caused by contact with the document.

[0010]

The image input device of the present invention has a reflecting surface having the same reflectance as the original on the background of the original reading portion. Since the reflecting surface is not a non-reflective surface, a shadow is formed at the edge of the document, so the image input apparatus of the present invention detects the skew of the document by detecting the shadow of the document.

Further, since the reflecting surface of the image input device of the present invention has the same reflectance as the original, it is read as a reference original surface when the original is not read, and can be used for light quantity correction and shading correction of the light source. Therefore, in order to perform light amount correction and shading correction, a reference document having the same reflectance as a standard document is read, or a special mechanism is provided to move the reference reflection surface to the document reading surface, You don't have to move around.

Furthermore, since the background of the document reading section is not a black non-reflective surface or a black reading roller that has been subjected to anti-reflection processing, the back surface of the document is not contaminated.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a first embodiment of the present invention, and is a block diagram of a document moving type image input device for outputting skew information and image information.

The original 1 is conveyed by the roller 2 and passes through the reading position 3. Here, the roller 2 is used only for conveying the original document, and therefore, white or uncolored rubber or the like is used in order to prevent the original document from being soiled. At the reading position 3, a reflecting surface 4 having the same reflectance as the original is fixed.

The light emitted by the light source 5 is reflected by the reflecting surface 4
Also, the light is reflected by the original 1 passing on the reflecting surface 4, and the mirror 6
And enters the CCD 8 via the lens 7. Where C
The photoelectric conversion unit of the CD 8 is arranged in the main scanning direction for reading the original. The light incident on the CCD 8 is converted into an analog signal, amplified by the amplifier 9, and then supplied to the A / D converter 10. The A / D converter 10 converts the input analog signal into, for example, an 8-bit digital signal.

The light amount correction circuit 11 constantly monitors the overflow signal of the A / D converter 10 and an amplifier so that the input signal level of the A / D converter is always constant regardless of the light amount fluctuation of the light source 1. Control the amplification factor of 9.

The digital signal output from the A / D converter 10 is supplied to the shading correction circuit 12 to correct variations in output level depending on the position in the main scanning direction. The digital signal output from the shading correction circuit 12 is supplied to the separation circuit 13 and is separated into the skew detection signal 107 of the first image signal and the image output signal 109 of the second image signal, and the skew detection is performed. The signal 107 is
The skew detection circuit 14 is entered. The skew feeding detection circuit 14 detects the skew feeding amount of the document from the shadows at both ends of the document in the main scanning direction based on the skew detection signal 107, and outputs it as skew feeding information.

Next, the operation of the image input device shown in FIG. 1 will be described. [Light Quantity Correction] The light quantity of the light source 5 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 correct the light amount in this type of device, but in the embodiment of the present invention, the method described below is used.

In FIG. 1, the CCD 8 reads the reflecting surface 4 immediately before reading the original 1. Here, since the reflecting surface 4 has the same reflectance as that of a document (generally white), C
The output signal waveform of the CD 8 has the maximum value that can occur when a document is read, as shown in FIG.

The light amount correction circuit 11 gradually increases the amplification factor of the amplifier 9 while monitoring the overflow signal of the A / D converter 10, and when the overflow signal is detected, the amplification factor is lowered by one step and the original document is read. This amplification rate is maintained until the reading is completed. The output signal waveform of the amplifier 9 is
It is shown in FIG.

By the above operation, the peak value of the signal level input to the A / D converter 10 is kept constant regardless of the light quantity of the light source 5. [Shading correction] The light amount of the light source 5 in FIG.
Generally, it is highest near the center and tends to be dark at both ends. Further, even in the process of passing through the mirror 6 and the lens 7, a slight change in the light amount occurs due to the difference in optical path length.

In order to correct such a variation in the amount of light depending on the position in the main scanning direction, it is necessary to perform shading correction in this type of apparatus, but in the embodiment of the present invention, the method described below is used. .

After the light amount correction process is completed, the CCD 8 reads the reflecting surface 4 again. Since the reflectance of the reflecting surface 4 is uniform over the entire surface, the output signal waveform of the A / D converter 10 reflects the shading characteristics and becomes as shown in FIG. The shading correction circuit 12 normalizes the signal according to the position in the main scanning direction so that the output signal waveform becomes as shown in FIG. 3B, and maintains this state until the reading of the document is completed. Since this normalization is well known, detailed description thereof will be omitted.

By the above operation, the signal level supplied to the separation circuit 13 is kept constant even if the amount of light varies depending on the position in the main scanning direction. [Skew Detection] The document 1 in FIG. 1 may be skewed due to a method of setting the document by an operator, a defect in mechanical accuracy of the roller 2, or the like. If the document is skewed, the recognition rate may be lowered in the recognition processing such as OCR or OMR, and the display may be difficult to see with an image input device such as an image scanner. There is a case where the amount is detected to correct the recognition process or the image information. In the embodiment of the present invention, the skew detection is performed by the method described below.

After the light amount correction processing and the shading correction processing are completed, the roller 2 in FIG. 1 is rotated to convey the original 1. The width of the reflecting surface 4 in the main scanning direction is generally
Therefore, when the document 1 passes over the reflection surface 4, a slight shadow is formed on the reflection surface 4 due to the thickness of the document 1. This shadow is output from the shading correction circuit 12 as a waveform as shown in FIG. This shadow is a shadow on both ends of the document in the main scanning direction.

The separation circuit 13 inputs an 8-bit signal (value of 00 to FF) in order to detect this minute shadow.
Is sampled with a threshold value S1 as shown in FIG. 4A, converted into a signal as shown in FIG. 4B, and output as a skew detection signal 107 to the skew detection circuit 14. The threshold value S1 is set to an appropriate value smaller than the signal value FF and larger than the level of the shadow of the document. At the same time, the separation circuit 1
3 obtains a normal image output by sampling an input 8-bit signal with a threshold value S2 as shown in FIG. 4 (a) and converting it into a signal as shown in FIG. 4 (c). , And output as the image output signal 109. The threshold value S2 is lower than the level of the shadow of the document and is set to about 50% of the peak value.

The skew detection circuit 14 sets the number of bits of the high-speed clock signal, which corresponds to the distance 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.
Each main scanning line is counted, and the difference from the count value (bit number) one line before is output as skew information.

When the document 1 is not skewed, the count value is constant and the skew information output value is 0. For example, the document is skewed to the right. In this case, since the count value increases, the skew information output value becomes a positive value. On the contrary, when a certain skew occurs to the upper left, the count value decreases and the skew information output value is negative. Becomes the value of. Further, even when a skew that is meandering left and right occurs in one document, an arbitrary value from plus to minus is output as skew information.
The skewed state can be accurately detected. The output of the skew feeding detection circuit 14 is supplied to a skew feeding correction mechanism (not shown) to correct the skew feeding of the document.

In the present embodiment, the skew is detected by the difference between the current line and the previous line of the distance between the left end of the CCD 8 in the main scanning direction which is the light receiving range and the left end of the shadow of the document 1; It may be detected by a change in the distance between the left end or the right end of the document and the right end of the shadow of the document 1. This skew detection circuit 14
Has an advantage that skew feeding can be easily detected regardless of the size of the original. (Other Embodiments) Next, as a second embodiment of the present invention, a block diagram of a stationary original image input device is shown in FIG.
Shown in

In the present embodiment, the original 1 is set between the stage glass 201 and the lid having the reflecting surface 4 attached to one surface, and the reading unit 202 in which the light source 5, the mirror 6, the lens 7 and the CCD 8 are integrated. But the stage glass 20
The original is read by moving below 1. CCD
The device configuration after 8 is the same as that of the first embodiment of the present invention.

In such a stationary document image input apparatus, when the document 1 is set on the stage glass 201, the document is skewed and the reading unit 20 is used.
Since slanting occurs due to rattling caused by a problem in mechanical accuracy when moving 2, the skewing detection by the skewing detection circuit 14 is effective.

In the above embodiments, the CCD is used as the image light receiving element, but a contact image sensor in which the light source and the light receiving element are integrated may be used.

[0034]

The first effect of the present invention is that the operation is simple or the structure is simple. The reason for this is that the reflecting surface of the image input device of the present invention has the same reflectance as the original, so that it is read as the reference original surface when the original is not read, and can be used for light amount correction and shading correction of the light source. As in the conventional technique, in order to perform light amount correction and shading correction, a reference document having the same reflectance as a standard document is read, or a special mechanism is provided to move the reference reflection surface to the document reading surface. Because there is no need. Further, since the skew is detected by the shadow of the document, no complicated circuit is required.

The second effect is that the back surface of the document is not soiled. The reason is that the reflecting surface of the present invention uses a color (generally white) having the same reflectance as the original.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is an example of a signal waveform in light amount correction, showing (a) CC.
The output signal waveform of D and the output signal waveform of the amplifier (b).

FIG. 3 is an example of a signal waveform in shading correction,
(A) Output signal waveform of A / D converter, (b) Output signal waveform of shading correction circuit.

FIG. 4 is an example of a signal waveform in skew detection, (a) an output signal waveform of a shading correction circuit, (b) an output signal waveform of a separation circuit (skew detection signal), (c) an output signal of a separation circuit. It is a waveform (image output signal).

FIG. 5 is a block diagram of a second embodiment of the present invention.

[Explanation of symbols]

 1 Original 2 Roller 3 Reading Position 4 Reflecting Surface 5 Light Source 6 Mirror 7 Lens 8 CCD 9 Amplifier 10 A / D Converter 11 Light Quantity Correction Circuit 12 Shading Correction Circuit 13 Separation Circuit 14 Skew Detection Circuit

Claims (6)

[Claims] 1. An image input device for irradiating a document with light and reading image information by the reflected light, wherein the background of the document reading portion has a reflecting surface having substantially the same reflectance as the document, and the reflecting surface can be the reflecting surface. An image input device comprising a document skew detection circuit for detecting skew of a document based on the shadow of the document. 2. An image input device for irradiating a document with light and reading image information by the reflected light, wherein a reflective surface is provided in the background of the document reading section and has substantially the same reflectance as the document, and the document reading section has A light source that emits light, a light receiving element that receives the reflected light from the document reading section, and a skew of the document by detecting a shadow formed on the edge of the document on the reflecting surface based on the output of the light receiving element. An image input device including a document skew detection circuit for detecting a document. 3. The skewed document detection circuit detects a shadow formed on both ends of the document in the main scanning direction based on the output of the light receiving element, and one end of the light receiving element in the main scanning direction and the detection. 3. The image input device according to claim 2, further comprising a circuit for detecting a distance between the shadow detected by the circuit and a circuit for detecting the skew of the document due to the change of the distance during scanning of the document. 4. The image input device according to claim 3, wherein the circuit for detecting the distance comprises a counter circuit. 5. An image input device for irradiating a document with light and reading image information by the reflected light, the reflecting surface being arranged in the background of the document reading section and having a reflectance substantially the same as that of the document, and the document reading section. A light source that emits light, a light receiving element that receives the reflected light from the document reading unit, a correction circuit that performs light amount correction or shading correction based on the output of the light receiving element, and a light source when the document is read. A document skew detection circuit that detects a skew of the document by detecting a shadow formed on the edge of the document based on the output of the light receiving element, and the reflection surface is a reference document when the document is not read. An image input device that is read as a surface and the correction circuit performs light amount correction or shading correction. 6. An image input device for irradiating a document with light and reading image information by the reflected light, the reflecting surface being arranged in the background of the document reading section and having substantially the same reflectance as the document, and the document reading section. A light source that emits light, a light receiving element that receives the reflected light from the document reading unit, a correction circuit that performs light amount correction or shading correction based on the output of the light receiving element, and a light source when the document is read. An image signal output circuit for outputting a first image signal including a shadow formed at the edge of the document and a second image signal not including the shadow based on the output of the correction circuit; An image input device including a document skew detection circuit for detecting skew of a document based on the document skew detection circuit.