JP2003060911A - Image reader and imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader that can optimally eliminate the background of a double-side original, without being affected by original information of each side of the double-side original. SOLUTION: The image reader detects background levels of both sides of the original and eliminates the background of both the sides, by using the side with a brighter background level for a reference. Or the background of the first side and then that of the second side read thereafter the eliminated, by using the background level of the first side read first for a reference. Or the background of both the sides is eliminated, by using the background level of one of both the sides read at the same time, for reference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus for removing a background of an original, and more particularly to an image reading apparatus for reading a double-sided original and an image forming apparatus equipped with the image reading apparatus.

[0002]

2. Description of the Related Art As a conventional example for removing the background of an original,
For example, Japanese Patent Application Laid-Open No. 11-103391 proposes a method for appropriately removing the background by setting an offset value that matches a user's instruction. As another conventional example, Japanese Patent Laid-Open No. 08-289145 proposes a method capable of preventing show-through when reading a double-sided original and improving the background density and image thinness of the original to be read. ing.

[0003]

By the way, in the prior art,
When the background of the original is removed by the method of alternately reading the front and back of a double-sided original using the original reversing function, the background is removed independently of the front and back even though the background has the same level of background. Therefore, if it is necessary to set the background detection range separately, or if the background areas on the front and back sides are significantly different, there is a possibility that the same degree of background removal may be processed differently. There is a point.

In view of the above-mentioned problems of the conventional example, it is an object of the present invention to provide an image reading apparatus capable of optimally removing the background of a double-sided original without being influenced by the original information of each side of the double-sided original. And

[0005]

In order to achieve the above-mentioned object, a first means is based on an image reading means for reading both sides of a document and a background level of one side of both sides read by the image reading means. And a background removing means for removing the background on both sides.

A second means is characterized in that, in the first means, the background removing means detects the background levels on both sides and removes the backgrounds on both sides with reference to the background level on the side having a bright background. .

In a third means, in the first means, the image reading means sequentially reads each surface of both sides, and the background removing means indicates the background level of the first surface previously read by the image reading means. As a reference, the backgrounds of the first surface and the second surface read later are removed.

In a fourth means, in the first means, the image reading means simultaneously reads each surface of both surfaces, and the background removing means reads one surface of each of both surfaces as a reference. It is characterized by removing the background.

The fifth means comprises an image reading device according to the first to fourth means and an image forming means for forming a visible image on a medium based on the image data read by the image reading device. The forming device is configured.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION <First Embodiment> An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a main part of a digital PPC as an embodiment of an image reading apparatus according to the present invention, FIG. 2 is a block diagram showing the reading unit of FIG. 3 in detail, and FIG. FIG. 4 is an explanatory diagram showing the background level, FIG. 4 is a circuit diagram showing the background removal circuit, and FIG. 5 is a configuration diagram showing a double-sided reading mechanism.

As shown in FIG. 1, the digital PPC according to this embodiment comprises a reading unit 10, an image processing unit 20, and a writing unit (not shown). As shown in FIG. 2, the reading unit 10 includes a CCD 11, an amplifier 12, an AD converter 13, and a timing processing IC 14, and an image processing unit 20 performs shading processing on the digital image data generated by the reading unit 10. A unit for performing image correction such as gamma correction processing, scaling processing, and filter processing, and an image processing IC 22 having a peak detection block 21, a memory 23, a CPU
24.

The image data read by the CCD 11 is
The background density of the document is detected by being sent from the reading unit 10 to the peak detection block 21, and this background density is fed back to the reading unit 10. Then, based on this background density, the image data read by the CCD 11 is adjusted to an appropriate white level by the amplifier 12 (amplifier 12b), and then converted into a digital signal by the AD converter 12. Here, it is assumed that the data is converted to 8-bit (256 gradations) data. The AD-converted image data is synchronously transferred to the image processing unit 20 in the next stage via the timing IC 14. Timing IC1
4, in addition to driving the CCD 11 and the AD converter 13, generating a sampling signal, each register and serial I / F function for generating and setting a control gate signal (setting of the reading width, etc.) associated with the reading operation. Have In the image processing unit 20, processing such as shading correction is performed on the sent image data, and thereafter,
Printing is performed via a writing unit (not shown).

The writing unit is the image processing unit 2.
An optical writing unit that optically writes on a photosensitive member based on image image data transferred from 0, and an image forming unit that develops a latent image written on the photosensitive member and transfers it onto a sheet to form an image. And a paper feeding unit that supplies paper to the image forming unit, a fixing unit that fixes the image transferred onto the paper, and a paper ejection unit that ejects the paper on which the image is fixed. Is ejected to the ejection tray. The optical writing unit, the image forming unit, and the fixing unit form an image forming unit that forms an image (visible image) on the paper fed from the paper feeding unit. In addition,
The sheet on which the image is formed is ejected from the sheet ejection unit. In addition,
Since each of these units is a known technique, detailed description thereof is omitted here.

Here, the background removal processing means that the original is not necessarily white, and there is an original having a background density such as newspaper, and the background density is replaced with white and the characters and pictures expressed in the original are displayed. It is a function to pick up only information such as. Use this function when you want to scan the original faithfully.
On the other hand, this function is turned on when FF is performed and only the expressed information is required, and in general, a switch SW is often provided in the operation unit of the PPC according to the needs of the user.

Various methods have been devised as a background removal method. As a general idea, the read original data is peak-held, and if it is an analog signal, it is fed back to the reference input of the AD converter 13 as shown in FIGS. You can cancel. This is because the background area in the document is considered to have the lowest density (white).

If the peak-held signal is a digital value after AD conversion, the original data is shifted by using a multiplication circuit or the like as follows: background removal data = input data × (255 / peak detection value). By doing so, the background part can be removed.

In the case of processing with a digital signal, it is also possible to store the document data in the memory once, perform the background removal processing after the reading, and then output.

Here, the conventional apparatus for reading a double-sided original using a DF having an original reversing function treats the front side and the back side as independent originals and removes the background, respectively, when removing the background. Was detected and the removal processing was performed. However, considering the original background, it is considered that the background is the density of the paper of the original, and the difference in density between the front and the back is small and can be almost ignored.

Theoretically, the same result should be obtained even if the peaks are detected independently as in the prior art, but some documents have many characters on the front side and a large background area, and the back side is a photograph and the background area is In the case of a narrow space, in order to recognize the background level in the same manner, it is necessary to devise a circuit and control. Therefore, an object of the present invention is to easily obtain a well-balanced double-sided read image by setting the same background detection level on the front and back even in such a case.

Here, FIG. 5 has a document reversing function and shows a conveyance path for reading both sides. In FIG. 5, the upper tray 3
The original set on the sheet 1 is read by the CCD 11 while being conveyed along the roller 32, and the front and back sides of the original are discharged on a lower tray (reversing tray) 33 parallel to the upper tray 31. Next, the reverse tray 33 (and the upper tray 3
With 1) raised to the original position of the upper tray 31, the original set on the reversing tray 33 is fed by the roller 32.
It is read by CCD 11 while being transported along
It is discharged onto the contact glass 34. The read document information is AD-converted and then stored in the memory.

At this time, in the first embodiment, the background level (peak detection) is performed on each of the front surface and the back surface. Then, the background level of the front surface and the background level of the back surface are compared with each other, and when the larger (white) background level is adopted and output from the memory, the background removal is performed on the same basis. The reason why a higher background level is adopted is that even if there is a document surface that does not have a large background area as described above, special control is possible if the other side is removed (such as speeding up the peak detection tracking speed). The idea is not to do. Also,
There is also the advantage that it can be balanced because it is not an independent process on the front and back.

As described above, according to the present embodiment, since the background of both sides is removed with the background level of one side of both sides as a reference, the accuracy is improved without being influenced by the document information of each side of the double-sided document. Highly effective background removal can be easily performed without variations in front and back.

<Second Embodiment> In the first embodiment,
Due to the method of comparing the background level (peak detection value) between the front and back sides, it is necessary to store the data after digital conversion in a memory or perform a prescan and reflect the result in an analog or digital processing circuit. Therefore, there are disadvantages that the processing takes time and the memory is required. In the second embodiment, the background detection level of the front side original that is read in advance is adopted and applied to the back side to compensate for this disadvantage.

An example of application is shown in FIG. Here, an example of feedback to an analog circuit will be described. The analog data read on the surface is input to parallel AD converters 13a and 13b via the amplifier 12. The AD converter 13b is supplied with a fixed reference voltage, and A
The D-converted digital data is used in the peak detection block 2
The peak is held at 1. The peak-held digital value is supplied as a reference input voltage of the AD converter 13a through the DA converter 22.

When reading the back side, the peak hold value used on the front side is fixed and read to remove the background. As a result, it is expected that the disadvantages of the first embodiment will be improved and that the removal of the background of the front and back surfaces will be balanced. However, while the front surface has a region where the reference changes in the process of peak detection, the back surface does not have a completely matched state because it is fixed. Further, the certainty of removing the background of the back surface depends on the accuracy of detecting the background of the surface.

Since the background of the first surface read earlier is used as a reference and the background of the second surface read later is removed, the background removal level between the front and back is processed without variation. Further, it is possible to omit the setting of the detection range associated with the document reversal and the control such as the start and end of the detection when reading the back surface. Further, it is not necessary to perform the background processing after reading both sides, and the memory or the like used for this processing becomes unnecessary.

<Third Embodiment> FIG. 7 shows a configuration example in which both sides of a document are read simultaneously. In this example, the contact sensors 11a and 11b arranged on the upper and lower sides are configured to read both the front surface and the back surface as the document passes between them. However, when the sensors 11a and 11b are arranged so as to face each other, they are influenced by the light from the light sources of each other, and therefore, the reading method is adopted in a state where they are arranged not to face each other. In that sense, the simultaneous reading is not a complete simultaneous reading, but the simultaneous reading here is defined as a reading operation performed by one job.
In this example, the contact sensors 11a and 11b are used, but the mechanism is complicated, but there is no problem even if it is a reduction optical system or the like.

In the structure shown in FIG. 7, the reading by the sensor 11a arranged on the lower side is defined as the front side original, and the reading by the sensor 11b arranged on the upper side is defined as the rear side original.
Loading will start on the surface first. In the third embodiment, in a device having such a double-sided simultaneous reading function, by removing the background of one of the backgrounds by using the background detection information of one of the two, the first and second
Similar to the above embodiment, the object is to reduce the variation in the background removal level between the front and back. Originally, it does not matter which one of the document surface detection levels is used, but in the configuration example, it is preferable to use the surface information because the surface starts reading first.

Here, it is assumed that the surface detection level of the front surface is Pk1 and the background detection level applied to the back surface is Pk2. At this time, if the front and back sensors 11a and 11b have the same reading characteristics, Pk1 = Pk2 is considered and the removal processing is performed. If the sensors 11a, 11b
If the characteristics are different due to different variations or configurations, for example, if the target value of the white level is different, it is necessary to apply the value compensated for Pk1 as Pk2. As an example, the white level target value of the front surface is 220/255 degit and the white level target value of the back surface is 200/255 degit Pk2 = Pk1 × 200/220.

If Pk1 and Pk2 are, for example, analog signals (peak voltage) of the read document, and the background is removed by inputting to the reference voltage of the AD converter 13, the information on the front surface is corrected to correct the information on the back surface. Since it is removed, it can be expected to suppress variations between the front and back. Also in the case of the third embodiment, as in the second embodiment,
Although the variation between the front and back can be suppressed, the certainty of the background level depends on the detection accuracy of the surface.

As described above, according to the present embodiment, even when both sides are read at the same time, the background removal level between the front and back can be processed without variation as in the first embodiment. Furthermore, it is not necessary to perform background processing after reading both sides, and it is not necessary to interpose a memory or the like.

[0033]

As described above, according to the present invention, the image reading means for reading both sides of a document and the background level of one side of both sides read by the image reading means are used as a reference to remove the background. Since the background removal means is provided and the background of both sides is removed based on the background level of one side of both sides, the background of the double-sided original is optimally removed without being influenced by the original information of each side of the double-sided original. You can

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of a digital PPC as an embodiment of an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the reading unit of FIG. 1 in detail.

FIG. 3 is an explanatory diagram showing a document and a background level thereof.

FIG. 4 is a circuit diagram showing a background removal circuit.

FIG. 5 is a configuration diagram showing a double-sided reading mechanism.

FIG. 6 is a circuit diagram showing a background removal circuit according to a second embodiment.

FIG. 7 is a configuration diagram showing a double-sided reading mechanism according to a third embodiment.

[Explanation of symbols]

10 reading unit 11 CCD 13, 13a, 13b AD converter 14 Timing IC 20 Image processing unit 21 Peak detection block 22 Image processing IC 23 memory 24 CPU

Claims (5)

[Claims] 1. An image reading device comprising image reading means for reading both sides of a document, and background removing means for removing the background of both sides based on the background level of one side of both sides read by the image reading means. apparatus. 2. The image reading apparatus according to claim 1, wherein the background removing means detects the background levels of both sides and removes the background of both sides with reference to the background level of a surface having a bright background level. 3. The image reading means sequentially reads each surface on both sides, and the background removing means uses the background level of the first surface previously read by the image reading means as a reference. The image reading apparatus according to claim 1, wherein the background of the second surface read later is removed. 4. The image reading means simultaneously reads each surface of both sides, and the background removing means removes the background of both sides with reference to the background level of one surface read by the image reading means. Claim 1 characterized by
The image reading device described. 5. An image reading apparatus according to claim 1, further comprising: an image forming unit that forms a visible image on a medium based on image data read by the image reading apparatus. An image forming apparatus characterized in that