JPH08265563A - Image reader - Google Patents

Abstract

PURPOSE: To provide the image reader capable of reading a high quality docu ment image. CONSTITUTION: The image on the front face of a document and that on the rear face are read by CCDs 1 and 2 respectively and are binarized by a binarization processing circuit 5. The image on the rear face is subjected to mirror image inversion processing in a rear face image/mirror image conversion circuit 6 and is synthesized with the image on the front face by a front and rear image synthesizing circuit 7. The synthesized image is subjected to prescribed picture processing by a picture processing circuit 8 and is outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-sided image reading apparatus.

[0002]

2. Description of the Related Art FIG. 9 is a schematic diagram showing the structure of a document reading section of a conventional image reading apparatus. In FIG. 9, 19 and 20 are CCs
A sensor such as D, 21 is a fluorescent lamp as a light source, 22 is a document, and 23 is a reading guide. The original 22 is irradiated with light from the fluorescent lamp 21 through a slit provided in the reading guide 23, and the reflected light thereof is converted into an electric signal by the sensors 19 and 20 and read.

In such an image reading apparatus, the slits of the reading guide 23 are displaced on the front and back sides so as not to be affected by the incident light on the opposite surface. Further, when performing frame processing or the like, the reading guide 2 is provided so that a portion with the original 22 and a portion without the original 22 can be clearly distinguished.
3, the portion of the original 22 that is the background is blackened, or the surface of the original 22 is mirror-reflected to totally reflect the incident light.
The part without 2 has a method of reading black data.

Next, FIG. 10 shows a block diagram of a configuration of an image processing unit in a conventional image reading apparatus. In FIG. 10, 19 is a CCD for reading the front side, 20 is a CCD for reading the back side, 26 is an A / D conversion circuit for converting the front and back image data read by the CCDs 19 and 20 into multi-values, 27
Is an image processing circuit for performing shading correction and the like, 28 is a binarization processing circuit for binarizing data, and 29 is an image processing circuit for removing isolated points. The front and back analog image data read by the CCDs 19 and 20 become digital multi-values in the A / D conversion circuit 26, and the image processing circuit 27 performs image processing such as shading correction. Subsequently, after passing through the binarization processing circuit 28, image processing such as removal of isolated points is further performed by the image processing circuit 29, and finally image data to be displayed / recorded is created.

When a document is read by such an image reading device, the description is provided on both sides of the document 22. Especially when the paper quality is thin, when the sensors 19 and 20 receive the light, the reflected light also mixes the transmitted light with the opposite light. Even the image data of the surface may be read. This phenomenon is called show-through in the future. The background treatment of the original 22 applied to the reading guide 23 has a slight effect in suppressing the show-through in that the transmitted light from the reflecting surface is reduced at the same time, but it is in fact completely prevented. It's impossible.

As a countermeasure against this, it is necessary to adjust the reading density so that the sharpness of the entire image is sacrificed. In particular, when the background is blackened, the entire image data is blackened, and this tendency becomes remarkable.

[0007]

However, in the above-mentioned conventional example, since the processing for suppressing the show-through is carried out as much as possible, the semi-transparent original such as the second original drawing in which the original format is printed on the back side is used. When a corrected article or the like is written on the back side, the data written from the back side is lost because the show-through is suppressed, and the read image becomes rather unclear.

Further, although the show-through has been suppressed in the past, it is necessary to make adjustments such as reducing the reading density when the original is thin paper, and the show-through is maintained while maintaining the sharpness of the surface image. It was impossible to completely eliminate.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems. According to the first aspect of the invention, an image reading apparatus converts an image on a document into a read image signal. A sensor, a mirror image inverting means for inverting the image signal of the back surface of the original document converted by the sensor, and a back surface image of the image surface of the original document converted by the sensor and the back surface image of the original image reversed by the mirror image inverting means. And an adding means for adding the image signals of.

According to a second aspect of the invention, in the first aspect of the invention, the sensor comprises a first sensor for reading an image on the front surface and a second sensor for reading an image on the back surface. It is what

According to a third aspect of the present invention, in the first aspect of the present invention, the sensor performs image reading of the front surface and the back surface with one sensor.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the adding means removes the signal component of the show-through image when performing addition of the front and back image signals. It is what

According to a fifth aspect of the present invention, in the first aspect of the present invention, the detecting means for detecting the type of the original document and the addition by the adding means according to the type of the original document detected by the detecting means. And a control means for controlling so as to change the method.

According to a sixth aspect of the invention, in the fifth aspect of the invention, the detecting means detects the transparency of the document.

The invention according to claim 7 is characterized in that, in the invention according to claim 4, there is provided discrimination means for discriminating the show-through image by comparing the image signal level of the front surface with the image signal level of the back surface. To do.

According to the present invention, in the image reading apparatus, a sensor for converting an image on a document into a read image signal, and a front image signal and a back image signal of the document converted by the sensor. And an addition unit that adds the signal components of the show-through image excluding the signal components.

According to a ninth aspect of the present invention, in the eighth aspect, the sensor comprises a first sensor for reading an image on the front surface and a second sensor for reading an image on the back surface. To do.

According to a tenth aspect of the present invention, in the eighth aspect of the invention, the sensor is characterized in that the front surface and the back surface are read by one sensor.

According to an eleventh aspect of the invention, in the invention of the eighth aspect, the detection means for detecting the type of the original document and the addition by the addition means according to the type of the original document detected by the detection means. And a control means for controlling so as to change the method.

According to the invention of claim 12, in claim 11,
In the invention described in (3), the detecting means detects the transparency of the original.

According to a thirteenth aspect of the invention, in the eighth aspect of the invention, there is provided a discriminating means for discriminating the show-through image by comparing the image signal level of the front side with the image signal level of the back side. It is what

According to a fourteenth aspect of the present invention, in the image reading apparatus, a sensor for converting an image on a document into a read image signal, and an image signal for the back side from an image signal for the front side of the document converted by the sensor. It has a subtraction means for subtracting.

According to the invention of claim 15, in claim 14
In the invention described in (1), there is provided a mirror image inverting means for inverting a mirror image of the image signal of the back surface of the original document converted by the sensor.

According to the invention described in claim 16, claim 14 is provided.
Alternatively, in the invention described in the fifteenth aspect, the sensor includes a first sensor for reading an image on the front surface and a second sensor for reading an image on the back surface.

According to the seventeenth aspect of the invention, there is provided the fourteenth aspect.
Alternatively, in the invention described in Item 15, the sensor performs image reading of the front surface and the back surface with one sensor.

In the eighteenth aspect of the present invention, the fourteenth aspect is as follows.
In the invention described in (1), the subtraction means performs the subtraction after making the signal level of the show-through image equal to the level of the image signal to be subtracted.

In the invention described in claim 19, claim 18 is provided.
In the invention described in (3) above, there is provided a discriminating means for discriminating a show-through image by comparing the image signal level of the front side with the image signal level of the back side.

[0028]

【Example】

<< Embodiment 1 >> FIG. 1 is a configuration block diagram of an image reading apparatus according to an embodiment of the present invention. In FIG. 1, 1 is a CCD for front surface reading which is a first sensor, 2 is CCD for reading a rear surface which is a second sensor, 3 is multi-value digital for analog image data read by CCDs 1 and 2. An A / D conversion circuit for conversion, 4 an image processing circuit for performing shading correction and the like, 5 a binarization processing circuit for converting multi-values into binary values, 6 a backside image mirroring processing circuit which is a mirror image inverting means,
Reference numeral 7 is a front / back image synthesizing circuit which is an adding means. Also, 8
Is an image processing circuit for removing isolated points.

The analog image data on the front and back sides read by the CCDs 1 and 2 are converted into digital multi-values by the A / D conversion circuit 3, passed through the image processing circuit 4 such as shading correction, and binarized by the binarization processing circuit 5. Be converted. It should be noted that the surface of the original document to be finally obtained as image data in the future is called the front surface, and the opposite surface is called the back surface.

Next, FIG. 2 is a diagram showing a state of image combination by the image reading apparatus of this embodiment, and the combination operation of front and back images will be described below with reference to FIG. 2 and FIG. Both sides of the image 9 of the original are read by the CCDs 1 and 2, respectively, and binarized by the binarization processing circuit 5. Then, of the binarized front and back image data 10 and 11, only the back surface image data 11 is mirror-inverted by the mirror image processing circuit 6, and the mirror image-inverted back image 12 is combined with the front image data 10 and the front and back image. The circuit 7 combines them to obtain a composite image 13.
Here, when synthesizing the image data of the front and back sides, if the images of the opposite surface of each surface are show-through, they are not synthesized. The show-through image can be discriminated by a method such as that of the third embodiment described later.

Next, the necessity of mirror image inversion will be described with reference to FIG. In FIG. 3, 14 is a front surface image read by the CCD 1, 15 is a back surface image read by the CCD 2, and 16 is a mirror image-inverted back surface image. When the semi-transparent original is read from both sides, the entire image of the back side image 15 becomes a mirror image of the front side image 14 which is horizontally reversed, and in this state, the displacement of the front and back images is complicated. Therefore, by using the back surface image 16 in which the image data of the back surface is mirror-inverted and the positional relationship in the horizontal direction of the image is matched with that of the front surface image, the front and back images can be more easily aligned. Further, since both sides of the original are read at the same time, even if the original is read slightly obliquely, if the mirror image is inverted, there is no influence on the image synthesis. Incidentally, as a special example, when the image on the back side is exactly equal to the left and right, it is not necessary to perform such mirror image inversion processing.

As described above, in the present embodiment, since the both-sided images of the original are read at the same time, the positional deviation of the front and back images is mechanically constant. Further, by inverting the back side image by mirror image, it is possible to accurately combine the front and back side images by using the frame of the recorded image or the like. Then, the unclear images on the front and back sides compensate for the lack of each other, and finally a clear recorded / display image is obtained. In this embodiment, two CCDs are provided to read the front and back images, but one CCD may read the both images.

As described above, in the present embodiment, even when a semitransparent original is read, the front and back images of the original can be easily and reliably read without missing necessary data.

<Embodiment 2> Since the combination of the front and back images as in Embodiment 1 described above is effective only when the original is semitransparent, a normal opaque original cannot be read. Therefore, in the second embodiment, by switching the flow of the image signal processing between the case of reading a normal original and the case of reading a semi-transparent original, a normal opaque original can be read clearly.

FIG. 4 is a block diagram showing the arrangement of such an image reading apparatus. Since the basic structure is the same as that of the first embodiment, the same components are designated by the same reference numerals and the description thereof will be omitted. In the image reading apparatus of FIG. 4, the transparency of the document is measured by the document transparency measuring circuit 9 which is the detecting means, and the control circuit 30 which is the controlling means switches the switch 10 according to the measurement result. When the original is a semi-transparent original, the switch 10 is switched to the a side, and the front and back images are combined as described above. When the original is opaque, the switch 10 is switched to the b side. No synthesis processing is performed.

Next, FIG. 5 shows the configuration of the document transparency measuring section 9, and the configuration for automatically determining the transparency of the document will be described. A light source 12 and a light receiving element 13 are provided above and below the passage of the original 11 in the conveying path to measure the transparency of the original, and the light from the light source 12 enters the light receiving element 13 so that the light transmitted through the original enters. Has become. The transparency of the document can be measured by the output level of the light receiving element 13 when the document passes. Of course, it is possible to manually switch the processing according to the document.

As described above, according to the present embodiment, a normal opaque original can be read without combining processing, and a semitransparent original can be combined. Therefore, regardless of the type of the original, high-quality reading is always performed. A high quality image can be read.

<Embodiment 3> FIG. 6 is a block diagram showing the arrangement of an image reading apparatus according to Embodiment 3 of the present invention. Here, in FIG.
Alternatively, the same components as those in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted. In FIG. 6, 14 is a backside image mirroring processing circuit, 15 is a front / backside image comparison circuit, 16 is a show-through data erasing circuit, and 17 is a binarization processing circuit for converting multivalues into binary.

First, as in the first and second embodiments, CCD1,
The analog original image data on the front and back sides read by 2 are A / D converted by the A / D conversion circuit 3 to be digital multi-valued, and image processing such as shading correction is performed by the image processing circuit 4.

In order to easily position the front and back images of the digital multi-valued data at this stage, the back surface data is mirror-inverted by the mirror image inversion circuit 14, and the mirror image-inverted back surface data is compared with the front surface data and the front and back image comparison circuit 15. To do.

Here, FIG. 7 shows a concrete example of image data in the third embodiment. In the figure, A is the data of the front side image to be recorded, and B is the image data of the back side which is the show-through. The image data A has a front surface density equal to or higher than that of the back surface, and the image data B has a back surface density sufficiently higher than that of the front surface as much as the original paper is transmitted. In the front and back image comparison circuit 15 which is the discrimination means, when the density of the front surface image data is equal to or higher than that of the back surface (image data A), it is stored as it is, and the density of the back surface image data is sufficiently higher than that of the front surface. In the case (image data B), the show-through data erasing circuit 16 erases the data from the front side image. By repeating this process, it is possible to obtain image data in which only the show-through image data is selectively erased without damaging the image data on the front surface. Here, the level of the offset image signal and the level of the image signal to be erased are adjusted in the data erasing circuit 16 to be the same level.

As described above, in this embodiment, by comparing the image data of the front side and the back side of the read document at the multi-valued level, only the show-through data is surely erased from the read image data, and no show-through occurs. It is possible to obtain a high-quality read image.

<Embodiment 4> In the above-described Embodiment 3, an example in which the show-through of the back side image is erased when the front side image of the original is read is shown. Is designed to prevent show-through,
A block diagram of the configuration is shown in FIG. Since the configuration of FIG. 8 is basically the same as the configuration of FIG.
The same reference numerals are given and the description is omitted. In FIG. 8, 18
Is a surface image mirroring circuit. In the fourth embodiment, the image data on both the front and back sides is converted into multivalued digital data to create mirror image images of the front and back sides. In the same way as the front side image data and the back side mirror image image were compared in multiple values to obtain the front side image from which the show-through was eliminated, the back side image data and the front side mirror image image were compared in multi-value and the show-through It is possible to obtain the image data of the back side with the erased. In this way, it is possible to obtain a double-sided read image in which only the show-through of each other is selectively erased.

[0044]

As described above, according to the first aspect of the invention, in the image reading apparatus, the sensor for converting the image on the document into the read image signal and the back surface of the document converted by the sensor. A mirror image inverting means for inverting the image signal of the image signal, and an adding means for adding the image signal of the front surface of the original document converted by the sensor and the image signal of the back surface mirror-inverted by the mirror image inverting means. . Then, the front side image signal and the back side image signal can be easily added regardless of the position and shape of the back side image.

According to a second aspect of the invention, in the first aspect of the invention, the sensor comprises a first sensor for reading an image on the front surface and a second sensor for reading an image on the back surface. And Since the front side image and the back side image can be read at the same time, the front side and back side images can be added easily in a short time regardless of the position of the document.

According to a third aspect of the present invention, in the first aspect of the present invention, the sensor has a structure in which the front surface and the back surface are read by one sensor. Then, it becomes possible to read and add images on both sides of the document with a simple configuration.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the addition means is configured to perform the addition by excluding the signal component of the show-through image when adding the front and back image signals. did. Then, it becomes possible to obtain a high-quality added image with an appropriate density.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the detecting means for detecting the type of the original document and the addition by the adding means according to the type of the original document detected by the detecting means. And a control means for controlling so as to change the method. Then, it becomes possible to appropriately add the front and back images according to the type of the document.

According to a sixth aspect of the invention, in the fifth aspect of the invention, the detecting means is configured to detect the transparency of the original. Then, it becomes possible to appropriately add the front and back images according to the transparency of the document.

According to a seventh aspect of the invention, in the fourth aspect of the invention, there is provided a discriminating means for discriminating the show-through image by comparing the image signal level of the front side with the image signal level of the back side. Since the show-through image component can be reliably discriminated, it is possible to obtain a higher quality added image.

According to the eighth aspect of the invention, in the image reading device, a sensor for converting an image on a document into a read image signal, and a front side image signal and a back side image signal of the document converted by the sensor. The configuration includes an adding unit that adds the signal components of the show-through image by removing them. And it has become possible to obtain high-quality images without show-through.

According to a ninth aspect of the invention, in the invention of the eighth aspect, the sensor comprises a first sensor for reading an image on the front surface and a second sensor for reading an image on the back surface. did. Since the front side image and the back side image can be read at the same time, the front side and back side images can be added easily in a short time regardless of the position of the document.

According to a tenth aspect of the present invention, in the eighth aspect of the invention, the sensor is configured so that the front surface and the back surface are read by one sensor. Then, it becomes possible to read and add images on both sides of the document with a simple configuration.

According to an eleventh aspect of the invention, in the invention of the eighth aspect, the detection means for detecting the type of the original document and the addition by the addition means according to the type of the original document detected by the detection means. And a control means for controlling so as to change the method. Then, it becomes possible to appropriately add the front and back images according to the type of the document.

In the invention described in claim 12, claim 11 is provided.
In the invention described in (3), the detecting means is configured to detect the transparency of the original. Then, it becomes possible to appropriately add the front and back images according to the transparency of the document.

According to a thirteenth aspect of the invention, in the eighth aspect of the invention, there is provided a determination means for comparing the image signal level of the front side with the image signal level of the back side to determine the show-through image. . Since the show-through image component can be reliably discriminated, it is possible to obtain a higher quality added image.

According to a fourteenth aspect of the present invention, in the image reading apparatus, a sensor for converting an image on a document into a read image signal, and an image signal for the back side from an image signal for the front side of the document converted by the sensor. And a subtraction means for subtracting. Then, the image signal on the back side can be easily subtracted from the image signal on the front side of the document, and a high-quality image without show-through can be obtained.

According to the fifteenth aspect of the invention, there is provided the fourteenth aspect.
In the invention described in (1), the mirror image inverting means for inverting the image signal of the rear surface of the original document converted by the sensor is provided. Then, regardless of the position or shape of the image on the back surface, it is possible to easily obtain an image by subtracting the image signal on the back surface from the image signal on the front surface.

In the sixteenth aspect of the invention, the fourteenth aspect is
Alternatively, in the invention described in the fifteenth aspect, the sensor includes a first sensor for reading an image on the front surface and a second sensor for reading an image on the back surface. Since the front side image and the back side image can be read at the same time, the back side image can be subtracted from the front side image easily and in a short time regardless of the position of the document.

According to the seventeenth aspect of the invention, there is provided the fourteenth aspect.
Alternatively, in the invention described in the fifteenth aspect, the sensor has a configuration in which the front surface and the back surface are read by one sensor. Then, it becomes possible to read and subtract the images on both sides of the document with a simple configuration.

According to the eighteenth aspect of the invention, there is provided the fourteenth aspect.
In the invention described in (3), the subtraction unit is configured to perform the subtraction after making the signal level of the show-through image and the level of the image signal to be subtracted the same. Since an appropriate image signal can be subtracted, high-quality reading can be performed without destroying the original image.

In the invention described in claim 19, claim 18 is provided.
In the invention described in (3) above, there is provided a discriminating means for discriminating the show-through image by comparing the image signal level on the front side with the image signal level on the back side. Since the show-through image component can be reliably discriminated, a higher quality image can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of an image reading apparatus according to an embodiment.

FIG. 2 is a diagram illustrating a front and back image combining operation of the image reading apparatus according to the embodiment.

FIG. 3 is an explanatory diagram of mirror image inversion of the image reading apparatus according to the embodiment.

FIG. 4 is a configuration block diagram of an image reading apparatus according to an embodiment.

FIG. 5 is a schematic diagram of a document transparency measuring unit according to the embodiment.

FIG. 6 is a configuration block diagram of an image reading apparatus according to an embodiment.

FIG. 7 is an illustration of show-through of a document.

FIG. 8 is a configuration block diagram of an image reading apparatus according to an embodiment.

FIG. 9 is a schematic diagram of a document reading unit of a conventional image reading apparatus.

FIG. 10 is a configuration block diagram of a conventional image reading apparatus.

[Explanation of symbols]

 1, 2 CCD 6, 14 Backside image mirroring circuit 7 Front and back side image synthesizing circuit 9 Original transparency measuring section 15 Front and back side image comparing circuit 16 Showthrough data erasing circuit 18 Front side image mirroring circuit 30 Control circuit

Claims (19)

[Claims] 1. A sensor for reading an image on a document and converting it into an image signal, a mirror image inverting means for inverting the image signal on the back side of the document converted by the sensor, and a sensor for converting the document converted by the sensor. An image reading apparatus comprising: an addition unit that adds the image signal of the front surface and the image signal of the back surface mirror-inverted by the mirror image inversion unit. 2. The image reading device according to claim 1, wherein the sensor includes a first sensor for reading an image on the front surface and a second sensor for reading an image on the back surface. 3. The image reading device according to claim 1, wherein the sensor performs image reading of the front surface and the back surface with one sensor. 4. The image reading apparatus according to claim 1, wherein the adding means removes the signal component of the show-through image when adding the front and back image signals. 5. The detecting means for detecting the type of the original document according to claim 1, and the control means for controlling the addition method by the adding means according to the type of the original document detected by the detecting means. An image reading apparatus having: 6. The image reading apparatus according to claim 5, wherein the detection unit detects the transparency of the document. 7. The image reading apparatus according to claim 4, further comprising a determination unit that compares a front-side image signal level and a back-side image signal level to determine a show-through image. 8. A sensor for converting an image on a document into a read image signal, and an addition for adding the image signal on the front side and the image signal on the back side of the document converted by the sensor, excluding the signal component of the show-through image. An image reading apparatus comprising: 9. The image reading device according to claim 8, wherein the sensor includes a first sensor for reading an image on the front surface and a second sensor for reading an image on the back surface. 10. The image reading device according to claim 8, wherein the sensor performs image reading of the front surface and the back surface with one sensor. 11. The detecting means for detecting the type of the original document according to claim 8, and the control means for controlling so as to change the addition method by the adding means according to the type of the original document detected by the detecting means. An image reading apparatus having: 12. The image reading apparatus according to claim 11, wherein the detection unit detects the transparency of the document. 13. The image reading apparatus according to claim 8, further comprising a determination unit that determines a show-through image by comparing the image signal level of the front side with the image signal level of the back side. 14. A sensor comprising: a sensor for converting an image on a document into a read image signal; and a subtraction unit for subtracting a back image signal from a front image signal of the document converted by the sensor. Image reading device. 15. The image reading apparatus according to claim 14, further comprising a mirror image inverting means for inverting a mirror image of the image signal of the back surface of the original document converted by the sensor. 16. The image reading device according to claim 14, wherein the sensor includes a first sensor for reading an image on the front surface and a second sensor for reading an image on the back surface. 17. The image reading device according to claim 14, wherein the sensor performs image reading of the front surface and the back surface with one sensor. 18. The image reading apparatus according to claim 14, wherein the subtraction unit performs the subtraction after making the signal level of the show-through image equal to the level of the image signal to be subtracted. 19. The image reading apparatus according to claim 18, further comprising a determination unit that compares the image signal level of the front side with the image signal level of the back side to determine a show-through image.