JP2006084595A - Wrinkle detector and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect wrinkles produced on recording member, without using a contact sensor. <P>SOLUTION: An image reading part 13 of a wrinkle detector 100 reads an original, formed by an image forming apparatus 900 and generates a scanned image data. Then, a control part 11 of the wrinkle detector 100 acquires image data, used for forming the original by an image forming apparatus 900 via a communication part 15. Then, the control part 11 compares the scanned image data with the image data, and when there is an image that does not exist in the image data in the scanned image data, the control part 11 decides that the image is an image due to paper wrinkles and outputs a wrinkle detection signal. A UI14 displays a message to the effect that the wrinkles have been detected or emits an alarm sound, based on the wrinkle detection signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for detecting wrinkles on a recording material.

  When paper wrinkles (wrinkles) occur on a recording material such as paper, the appearance when an image is formed is significantly impaired. For this reason, it is necessary to identify the paper on which the paper wrinkle has occurred and to remove it. However, relying on such manual processing by humans is not complicated for the operator (user). In particular, if a large amount of printing is performed, there is a limit to such work by humans. For this reason, various techniques for detecting paper wrinkles have been proposed. For example, in the technique described in Patent Document 1, a pickup sensor that detects the displacement of the paper surface by scanning while bringing the actuator into contact with the surface of the paper is provided. Yes.

JP-A-9-202519

However, there are some problems in detecting paper wrinkles using a contact-type sensor as described in Patent Document 1 described above.
First, in order to obtain good detection accuracy using a contact-type sensor, it is necessary that the sensor is always in contact with the paper surface with an appropriate contact pressure. However, since a color material such as toner may be formed on the paper or the paper thickness may be different, it is extremely difficult for the sensor to keep in contact with the paper surface with a constant contact pressure. If the contact pressure is too small, the sensor moves away from the sheet surface, and if the contact pressure is too large, the load at the time of sheet conveyance increases and a paper jam occurs.

In addition, a sensor that is in contact with one point of the paper as in Patent Document 1 cannot scan the entire surface of the conveyed paper, and thus fails to detect paper wrinkles occurring on the paper. Sometimes.
Furthermore, the paper surface may be displaced not only by paper wrinkles but also by, for example, curling. However, if the displacement of the paper surface is detected as in Patent Document 1, it is difficult to distinguish such a displacement from the displacement caused by the paper wrinkles, so it is difficult to separate only the paper wrinkles. is there.

  The present invention has been made in view of such a background, and an object thereof is to provide a technique for accurately detecting wrinkles generated in a recording material without using a contact sensor.

In order to achieve the above-described object, the present invention reads an image formed on a recording material when image data is input to the image forming apparatus and an image is formed on the recording material based on the image data. An image reading unit that generates scan image data representing the read image, the scan image data generated by the image reading unit and the image data input to the image forming apparatus are compared, and the scan image data is A comparison unit that determines whether or not the image data matches, and a wrinkle generated on the recording material when the comparison unit determines that the scanned image data does not match the image data. And a wrinkle detection device including an output means for outputting a wrinkle detection signal.
According to such a wrinkle detection apparatus, the wrinkle is detected by comparing the scanned image data generated by the image reading unit with the image data used for forming the image of the recording material, and therefore a contact type sensor is used. Therefore, it is possible to accurately detect wrinkles generated in the recording material.

Further, in the wrinkle detection device described above, as a more preferable aspect, the comparison unit may be configured such that the scan image data does not match the image data when an image that does not exist in the image data is included in the scan image data. Judge.
When the recording material is wrinkled, a shadow is generated by the wrinkle when the image is read by the image reading means. Therefore, if the image corresponding to the shadow is included in the scanned image data and such an image is not included in the image data input to the image forming apparatus, the recording material is wrinkled in this case. Can be determined.

Further, the wrinkle detection device described above is more preferable in that when the scanned image data is determined not to match the image data and the output means outputs the wrinkle detection signal, the wrinkle detection device is provided with the image forming device. An instruction output means for outputting an instruction to form an image based on the image data is provided.
In this way, the image formed on the wrinkled recording material can be printed again by the image forming apparatus.

According to another aspect of the present invention, as an aspect different from the above-described wrinkle detection apparatus, an image reading unit that reads a front surface and a back surface of a document and generates scan image data representing an image formed on each surface; A comparison unit that compares the scanned image data of the front surface and the scanned image data of the back surface generated by the unit, and a mirror image of the image included in the scanned image data of the back surface by the comparing unit is the scanned image data of the front surface And an output means for outputting a wrinkle detection signal indicating that wrinkles are generated on the original when it is determined that the wrinkle is included.
This wrinkle detection device reads both sides of a document, and determines that the document is wrinkled when the back surface includes a mirror image of the image formed on the front surface. Even in this case, it is possible to accurately detect wrinkles generated on the recording material without using a contact sensor.

Further, in this wrinkle detection apparatus, as a more preferable aspect, the image reading unit reads the back side of the document, and the comparison unit has no image in the scanned image data of the back side generated by the image reading unit. If it is determined, the image reading unit ends the process without reading the surface of the document.
If the image corresponding to the wrinkle does not exist on the back side, it is not necessary to read the front side in this case because the original is not wrinkled. Therefore, it is possible to save time and labor for reading the surface of the document by doing in this way.

  Note that the function of the wrinkle detection apparatus as described above can also be mounted on the image forming apparatus.

(1) First Embodiment (1-1) Configuration FIG. 1 is a block diagram showing a configuration of a wrinkle detection apparatus 100 according to an embodiment of the present invention. As shown in FIG. 1, the wrinkle detection apparatus 100 includes a control unit 11, a storage unit 12, an image reading unit 13, a UI (User Interface) 14, and a communication unit 15.

The control unit 11 includes an arithmetic device such as a CPU (Central Processing Unit) and various memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and controls the operation of each unit of the wrinkle detection device 100. To do. Moreover, the control part 11 performs the wrinkle detection process mentioned later. Various values used for the wrinkle detection process are stored in the ROM.
The storage unit 12 is a large-capacity nonvolatile storage device such as a hard disk, and stores a program PRG1 for the control unit 11 to execute the above-described wrinkle detection process.

The image reading unit 13 is a so-called scanner, and includes a platen, a light source, an optical system, a light receiving element, and a signal processing unit. In the image reading unit 13, a light source irradiates light on a document placed on a platen, and a light receiving element receives the reflected light through an optical system and outputs an image signal. Scanned image data is generated by the signal processing unit performing various types of signal processing.
The UI 14 includes a liquid crystal display, various buttons, and a speaker, and receives an instruction from the user by operating a button. Further, the UI 14 provides the user with information corresponding to the operation of the wrinkle detection device 100, for example, by displaying a message on a liquid crystal display or generating a warning sound from a speaker.
The communication unit 15 is an interface for communicating with an external device such as the image forming apparatus 900. The wrinkle detection apparatus 100 acquires image data from the image forming apparatus 900 via the communication unit 15.

(1-2) Operation Based on the above configuration, the wrinkle detection apparatus 100 reads a document on which an image is formed by the image forming apparatus 900, and executes wrinkle detection processing to determine whether or not wrinkles are generated in the document. To do. Hereinafter, the wrinkle detection process executed by the wrinkle detection apparatus 100 will be described in detail.
First, image data used in the following description of wrinkle detection processing and scan image data obtained by reading a document will be described. Since this process is a process for detecting paper wrinkles, the description here assumes that paper wrinkles are generated in the document.

FIG. 2 is a diagram showing image data D11 and scanned image data D12 in the present embodiment. As shown in the figure, wrinkle image G _w is formed corresponding to the paper wrinkles on the document in the scanned image data D12. In general, paper wrinkles are generated three-dimensionally on a document. When this is read by the image reading unit 13, a part of light from the light source is inhibited from traveling by the paper wrinkles, and shadows on the document. Occurs. Since the image reading unit 13 cannot read the image on the surface of the original in the shadowed portion as described above, an image is generated in a portion corresponding to the paper wrinkle on the original. This image is referred to herein as a “wrinkle image”.
The scanned image data D12 is the same as the image data D11 except that the wrinkled image _Gw is formed. Strictly speaking, there is a slight error between the scanned image data D12 and the image data D11 due to the performance of the image forming apparatus 900 and the image reading unit 13, but this error is negligibly small and wrinkles. That is, it does not affect the detection process.

  Next, a specific operation in the wrinkle detection process of the present embodiment will be described with reference to the flowchart of FIG. Here, an example will be described in which the image forming apparatus 900 forms an image based on the above-described image data D11 on a sheet, and the image reading unit 13 reads the sheet as a document to generate the scan image data D12.

First, the control unit 11 of the wrinkle detection apparatus 100 causes the image reading unit 13 to read (scan) a document and generate scan image data D12 (step S101). The scanned image data D12 is temporarily stored in the RAM of the control unit 11.
Subsequently, the control unit 11 acquires the image data D11 used by the image forming apparatus 900 for image formation via the communication unit 15 (step S102). The acquired image data D11 is also temporarily stored in the RAM of the control unit 11.
When the image data D11 is acquired, the control unit 11 compares it with the scan image data D12 and determines whether or not a wrinkle image is included in the scan image data D12 (step S103).

Here, a method of determining a wrinkle image by the control unit 11 will be specifically described. The control unit 11 obtains color values (for example, values indicating coordinate points in the RGB color space) of each pixel of the image data D11 and the scan image data D12 stored in the RAM, and calculates a difference between these values, that is, a color difference ΔE. Then, the control unit 11 compares the color difference ΔE with a predetermined threshold Th, and specifies a pixel in which the color difference ΔE exceeds the threshold Th (hereinafter, the pixel specified here is referred to as “mutant pixel”). After specifying the mutated pixels with respect to the entire scan image data D12, the control unit 11 then creates a group of mutated pixels that continuously exist on the scan image data D12 with a certain width and height. It is determined whether or not such a variation pixel group exists, and it is assumed that this is a “wrinkle image”.
Note that the threshold value Th may be a value that is small enough to ignore errors due to the performance of the image forming apparatus 900 and the image reading unit 13 in the color difference ΔE. Further, the width and height for specifying the mutated pixel group as a wrinkled image may be arbitrarily determined.

In this determination, if it is determined that the scanned image data D12 includes a wrinkle image (step S103; YES), the control unit 11 indicates a “wrinkle detection signal” indicating that a paper wrinkle has occurred on the document. Is output (step S104). Based on this wrinkle detection signal, the control unit 11 notifies the user of detection of paper wrinkles via the UI 14. For example, the control unit 11 displays a message on the liquid crystal display of the UI 14 or emits a warning sound on the speaker.
When these operations are performed, the control unit 11 ends this processing. When it is determined in step S103 that the scanned image data D12 does not include a wrinkle image (step S103; NO), the control unit 11 ends the process without performing the process of step S104 described above.

  By performing the wrinkle detection process as described above, it is possible to reliably detect whether paper wrinkles are generated on the document. In the present embodiment, since scan image data that is a reading result of the image reading unit 13 is used, it is possible to detect the presence or absence of paper wrinkles on the entire surface of the paper. Further, since this wrinkle detection process does not directly detect the unevenness of the paper surface, it is not affected by the displacement of the paper surface due to curling or the like, and no error due to fluctuations in contact pressure occurs.

(2) Second Embodiment Next, an embodiment of the present invention that is different from the above-described first embodiment will be described.
(2-1) Configuration FIG. 4 is a block diagram illustrating a configuration of the wrinkle detection apparatus 200 according to the present embodiment. As shown in the figure, the wrinkle detection apparatus 200 includes a control unit 11, a storage unit 22, an image reading unit 23, a UI 14, and a communication unit 15. The configuration of the wrinkle detection device 200 is the same as that of the wrinkle detection device 100 of the first embodiment with respect to the control unit 11, UI 14, and communication unit 15. Omitted. The storage unit 22 is different from the storage unit 12 of the first embodiment in that it stores a program PRG2 for executing wrinkle detection processing in the present embodiment.
The image reading unit 23 is a scanner that can read both sides of a document. The image reading unit 23 may include a plurality of light receiving elements and the like, and may be configured to read both sides of the document at the same time. Alternatively, after reading one side of the document, the image is transported and rotated, and then the other side is read. Such a so-called DADF (Duplex Auto Document Feeder) may be used.

(2-2) Operation Next, the wrinkle detection process executed by the wrinkle detection apparatus 200 of this embodiment will be described.
First, the scan image data used for the description of the following wrinkle detection process will be described. In the wrinkle detection process of the present embodiment, both the scanned image data on the front side and the scanned image data on the back side of the document are used. Therefore, in the following, these are referred to as “front-side scan image data” and “back-side scan image data” for distinction. Further, as in the first embodiment described above, this process is a process for detecting paper wrinkles, and therefore, here, description will be made assuming that paper wrinkles are generated in the document.

FIG. 5 is a diagram showing the front scan image data D21 and the back scan image data D22 in the present embodiment. As shown in the figure, a wrinkle image G _w2 corresponding to a paper wrinkle on the document is formed in the back side scan image data D22. Similarly, a wrinkle image G _w1 is formed in the surface scan image data D21. The wrinkle image G _w2 on the back scan image data D22 is equal to an image obtained by inverting the wrinkle image G _w1 on the front scan image data D21. Note that the image indicated by the dotted line in the back scan image data D22 means an image on the front surface, and is not formed on the back surface.
As described above, the paper wrinkle on the document generates a wrinkle image in both the front surface scan image data D21 and the back surface scan image data D22, and these wrinkle images are mirror images of each other.

Next, a specific operation in the wrinkle detection process of the present embodiment will be described with reference to the flowchart of FIG.
First, the control unit 21 of the wrinkle detection apparatus 200 causes the image reading unit 23 to read the surface of the document and generate the surface scan image data D21 (step S201). Subsequently, the control unit 21 causes the image reading unit 23 to read the back side of the document, and generates back side scanned image data D22 (step S202). The control unit 21 temporarily stores these image data in the RAM of the control unit 21.

Next, the control unit 21 inverts the back scan image data D22 in order to obtain a mirror image from the back scan image data D22 (step S203). Specifically, an address shift operation or the like may be performed on the back side scanned image data D22 stored in the RAM. For example, if the back scan image data is image data of m × n pixels and one pixel data is stored in one memory cell, the memory address of the first column of pixel data and the mth The memory address of the pixel data in the column is switched, the memory address of the pixel data in the second column is replaced with the memory address of the pixel data in the (m−1) th column, and so on. The process of replacing the memory address and the memory address of the pixel data in the (m−i + 1) th column (where 1 ≦ i ≦ m / 2) ”may be performed for all rows. The image data obtained by inverting the back scan image data obtained in this way is hereinafter referred to as “back mirror image data”. An image corresponding to the wrinkle image of the back scan image data on the back mirror image data is hereinafter referred to as a “wrinkle mirror image”.
Figure 7 is a diagram illustrating the rear surface scan image data D22 coated mirror image image data D22 obtained by inverting _m, and a wrinkle mirror image images G _m on the back side mirror image image data D22 _m.

After making the inversion of the back scan image data D22, the control unit 21 compares the back mirror image image data D22 _m and the surface scan image data D21, wrinkles mirror image image on the surface scanned image data D21 on the back mirror image image data D22 _m G _m It is determined whether there is an image corresponding to (step S204). As a specific example, on the surface scanned image data D21, if there is an image having the same color value and wrinkles mirror image image G _m in positions corresponding to the pixel group forming the wrinkles mirror image G _m The control unit 21 determines that the result is positive.

In this determination, if it is determined that the image corresponding to the wrinkle mirror image images G _m present in the surface scan image data D21 (step S204; YES), the control unit 21 that the paper wrinkles are occurring on a document Is output (step S205). Based on this wrinkle detection signal, the control unit 21 notifies the user of detection of paper wrinkles via the UI 24. For example, the control unit 21 causes a message to be displayed on the liquid crystal display of the UI 24 or causes a speaker to emit a warning sound.

When these operations are performed, the control unit 21 ends the present process. Note that, in step S204, if the image corresponding to the wrinkle mirror image images G _m are judged to be absent in the surface scan image data D21 (step S204; NO), the control unit 21 perform the processing of the above step S205 This process is terminated without

  By performing the wrinkle detection process as described above, it is possible to reliably detect whether paper wrinkles are generated on the document. In the present embodiment, scan image data that is a reading result of the image reading unit 23 is used as in the first embodiment described above, and therefore the presence or absence of paper wrinkles can be detected on the entire surface of the paper. In the present embodiment, paper wrinkles are detected based on the front-side scan image data and the back-side scan image data, so that image data that is the basis of the document is not necessary.

(3) Modifications Note that the application of the present invention is not limited to the embodiment described above, and various modifications are possible. Some examples are shown below.
(3-1) Modification 1
First, in the above-described first embodiment, it has been described that the control unit 11 notifies the user of the detection of paper wrinkles based on the wrinkle detection signal output in step S104. However, in addition to notifying the user in this way, an instruction to form an image is output to the image forming apparatus 900 in order to form an image on which it is determined that paper wrinkles have occurred on the paper again. May be. Specifically, for example, when the control unit 11 determines that paper wrinkles are generated on the document on which the image data D11 is formed, the control unit 11 forms the image data D11 on the paper again with respect to the image forming apparatus 900. An instruction to do so may be output via the communication unit 15. In this way, even if the user does not give an instruction to form an image again, an alternative to a document in which paper wrinkles have occurred can be obtained.

(3-2) Modification 2
Further, as shown in FIG. 5, in the second embodiment described above, the back scan image data is blank paper, that is, image data having no image other than a wrinkle image. However, this is for facilitating the description of the embodiment, and the present invention is not intended to be limited to such an aspect. The present invention can be applied to a document having images formed on both sides.

When images are formed on both sides, in the example given in the second embodiment described above, there is a possibility that an area that is not originally a paper wrinkle may be determined as a paper wrinkle in the determination in step S204. Therefore, when images are formed on both sides, the determination in step S204 may be performed not in units of pixels but in units of figures as in the following example.
Here, the surface scan image data D31 and the back scan image data D32 in the case of being formed an image on both sides in FIG. 8 shows a back surface mirror image image data D32 _m at this time. In the figure, G _w1 , G _w2 and G _m2 represent wrinkle images. Further, it shows a view obtained by superposing the surface scan image data D31 and the back mirror image image data D32 _m in FIG. For convenience of explanation, it is assumed that the colors of the images formed in these image data are the same color. Further, in FIG. 9, only the G _w is a wrinkle image showing the paper wrinkles.
At this time, if the determination is made as in step S204 of the second embodiment described above, it is determined that the overlapping area X of the rectangular area A and the rectangular area B in FIG. Therefore, in such a case, the control unit of the wrinkle detection device may determine an area having continuous color values as one image. In this way, the control unit makes a determination such as “whether or not an image corresponding to the rectangular area B is formed in the surface scan image data D31”. Therefore, the area X is erroneously determined to be a paper wrinkle. It will not be judged.

(3-3) Modification 3
In the second embodiment described above, when the back side of the document to be read is limited to a blank sheet, the wrinkle detection process can be performed by another method.
FIG. 10 is a flowchart showing a variation of the wrinkle detection process in the second embodiment described above. Explaining along the figure, first, the control unit 21 of the wrinkle detection apparatus 200 causes the image reading unit 23 to read the back side of the document and generate back side scan image data D22 (step S301). Subsequently, the control unit 21 determines whether or not any image exists in the back side scanned image data D22 (step S302). Here, since the back side of the document should be blank, if any image exists in the back side scanned image data D22, it is determined that this image is generated by paper wrinkles. If there is no image in the back side scanned image data D22 (step S302; NO), the control unit 21 determines that no paper wrinkle has occurred in the document, and does not perform the subsequent operations. This process is terminated. On the other hand, if any image exists in the back side scan image data D22 (step S302; YES), the control unit 21 causes the image reading unit 23 to generate the front side scan image data D21 (step S303), and the back side scan image data D22 is stored. is inverted (step S304), the image corresponding to the wrinkle mirror image image G _m subsequent surface scan image data D21 on the back mirror image image data D22 _m determines whether the present (step S305). If the determination in step S305 is affirmative, the control unit 21 outputs a “wrinkle detection signal” (step S306). Note that the processes in steps S303 to S306 are the same as the processes in steps S201 and S203 to S205 of the second embodiment described above, and thus the description thereof is omitted.
When such processing is performed, if the determination in step S302 is negative, the processing ends without performing any subsequent operation. In other words, since the surface is not read for a document on which no paper wrinkles are generated, when performing a wrinkle detection process on a large number of documents, the processing is performed at a higher speed than in the second embodiment. It can be terminated.

(3-4) Modification 4
In the above-described embodiment, the wrinkle detection device includes a platen, and the user places a document on the platen and detects paper wrinkles. However, if paper wrinkles are detected for a large amount of documents, this mode places a great burden on the user. Therefore, a so-called feeder mechanism may be provided in which the original is accommodated in the wrinkle detection device and sequentially conveyed. In such a case, a so-called sorter mechanism may be further provided that sorts a document with paper wrinkles and a document with no paper wrinkles.

(3-5) Modification 5
Note that the control unit, the storage unit, the image reading unit, and the like included in the wrinkle detection apparatus according to the present invention include an image forming apparatus that is generally called a multi-function peripheral and has substantially the same function. Therefore, it is easy for the image forming apparatus itself to execute the above-described wrinkle detection process on the image formed by the image forming apparatus. That is, the function of the above-described wrinkle detection apparatus can be mounted on the image forming apparatus.

It is the block diagram which showed the structure of the wrinkle detection apparatus which concerns on the 1st Embodiment of this invention. It is the figure which showed the image data and scan image data in the embodiment. It is the flowchart which showed the wrinkle detection process of the embodiment. It is the block diagram which showed the structure of the wrinkle detection apparatus which concerns on the 2nd Embodiment of this invention. It is the figure which showed the surface scan image data and back surface scan image data in the embodiment. It is the flowchart which showed the wrinkle detection process of the embodiment. It is the figure which illustrated back mirror image image data which reversed the back scan image data of the embodiment, and a wrinkle mirror image on this back mirror image data. It is the figure which showed the surface scan image data and back surface scan image data in case the image is formed in both surfaces, and the back surface mirror image image data at this time. The figure which superimposed the surface scan image data and the back surface mirror image image data is shown. It is the flowchart which showed the modification of the wrinkle detection process in the 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100, 200 ... Wrinkle detection apparatus, 11 ... Control part (comparison means, output means), 12, 22 ... Memory | storage part, 13, 23 ... Image reading part (image reading means), 14 ... UI, 15 ... Communication part (instruction) Output means).

Claims (6)

When image data is input to the image forming apparatus and an image is formed on a recording material based on the image data, the image reading that reads the image formed on the recording material and generates scanned image data representing the read image Means,
A comparison unit that compares the scanned image data generated by the image reading unit with the image data input to the image forming apparatus and determines whether the scanned image data matches the image data;
A wrinkle detection device comprising: an output unit that outputs a wrinkle detection signal indicating that wrinkles are generated in the recording material when the comparison unit determines that the scanned image data does not match the image data. . The wrinkle detection apparatus according to claim 1, wherein the comparison unit determines that the scanned image data does not match the image data when the scanned image data includes an image that does not exist in the image data. When it is determined that the scanned image data does not match the image data and the wrinkle detection signal is output by the output unit, an instruction to form an image based on the image data is output to the image forming apparatus. The wrinkle detection apparatus according to claim 1, further comprising an instruction output unit. Image reading means for reading the front and back surfaces of the document and generating scan image data representing the images formed on the respective surfaces;
Comparison means for comparing the scanned image data of the front surface and the scanned image data of the back surface generated by the image reading means;
When the comparison unit determines that a mirror image of the image included in the scanned image data on the back surface is included in the scanned image data on the front surface, a wrinkle detection signal indicating that wrinkles are generated on the document A wrinkle detection device comprising: output means for outputting. The image reading means reads the back side of the document;
When the comparison unit determines that no image exists in the scanned image data on the back surface generated by the image reading unit,
The wrinkle detection apparatus according to claim 4, wherein the image reading unit ends the process without reading the surface of the document.   An image forming apparatus comprising the wrinkle detection device according to claim 1.

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