Image reading device and image reading method

Abstract

To detect thick paper early to prevent false detection of multi-feeding and thereby to prevent complicated operations.SOLUTION: A reading unit 11 can pick up an image of a shadow generated at a leading end of a document P, and a control unit 13 estimates the thickness of the document P based on a pixel value of the shadow. In thick paper determination in a step S106, when the document is determined to be thin paper, a multi-feeding error is determined again in step S108, and the error is displayed on a display 14. When the document is determined to be thick paper in step S106, the control unit 13 turns off multi-feeding detection in step S110. That is, even though multi-feeding is determined in step S102, in step S110, the control unit turns off multi-feeding detection to ignore the determination, stands by until the completion of paper feed in step S112, and upon completion, turns on the multi-feeding detection again in step S114.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an image reading apparatus and an image reading method. [Background technology]

[0002] Document scanners read documents by transporting each document set in the ADF to the scanning unit one by one. Sometimes, multiple documents are unintentionally fed from the ADF at the same time, which is called a multi-feed. If multiple documents are fed, the documents that should be read cannot be read, so it is necessary to detect the multi-feed and interrupt or stop the scanning. Ultrasonic sensors are sometimes used to detect double feeds. When an ultrasonic sensor is installed in the document transport path, the amount of ultrasonic transmission attenuation when multiple documents pass through is greater than the amount of ultrasonic transmission attenuation when a single document passes through, so double feeds can be detected by detecting the amount of transmission attenuation.

[0003] However, even if there is only one document, if it is thick paper, the ultrasonic transmission attenuation is large, which may result in a false detection of a double feed. If the scanner stops due to a false detection of a double feed, the user is required to perform an operation to continue processing. The same applies when there is both thick and thin paper. Alternatively, the user will need to turn off the double feed detection function beforehand. Here, techniques for detecting thick paper are known, such as those disclosed in Patent Document 1 and Patent Document 2.

[0004] The technology disclosed in Patent Document 1 assumes that the document is thick paper with a specific shape, such as a credit card, and recognizes the shape of the scanned document. If the document has a specific shape, processing is performed to prevent double feeding. Moreover, the technology disclosed in Patent Document 2 recognizes a shadow that occurs at the edge of a document and corresponds to the paper thickness as an image, and estimates the thickness based on the image of the shadow. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-100459 A [Patent Document 2] JP 2018-195960 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the case of the technology disclosed in Patent Document 1, in order to recognize the shape of the document, it is necessary to read the entire document, and the timing at which the thickness can be reflected is delayed. In the case of the technology disclosed in Patent Document 2, even if the thickness can be detected, it is not possible to immediately prevent erroneous detection of double feeding. The present invention detects thick paper at an early stage, prevents erroneous detection of double feeding, and prevents complicated operations. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the present invention provides an image reading device comprising a reading unit that reads a document, a background plate that forms the background of the document, a multi-feed detection unit that detects multi-feed of the document, and a control unit, wherein the control unit is configured to read the shadow of the document that appears on the background plate using the reading unit, and to not determine that a multi-feed has occurred when a multi-feed is detected by the multi-feed detection unit and the pixel value of the read shadow exceeds a predetermined threshold, and to determine that a multi-feed has occurred when a multi-feed is detected by the multi-feed detection unit and the pixel value of the read shadow does not exceed a predetermined threshold.

[0008] In the above configuration, the multi-feed detection unit detects a multi-feed. The control unit causes the reading unit to read a shadow of the document that appears on the background board. Also, when the multi-feed detection unit detects a multi-feed and a pixel value of the read shadow exceeds a predetermined threshold, the control unit does not determine that a multi-feed has occurred, and when the multi-feed detection unit detects a multi-feed and a pixel value of the read shadow does not exceed a predetermined threshold, the control unit determines that a multi-feed has occurred.

[0009] In this way, the pixel value of the shadow that is read is compared with a predetermined threshold value. If the shadow is large, the pixel value of the shadow is large. The thicker the paper, the longer and darker the shadow becomes. Therefore, the size of the pixel value of the shadow corresponds to the thickness of the document, and when the document is thick, even if the multi-feed detection detects a multi-feed, the control unit does not determine that a multi-feed has occurred.

[0010] As described above, when the document is thick, it is not judged as a double feed, so when reading thick paper, it is not erroneously detected as a double feed and the original document can be read correctly. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of an image reading device according to an embodiment of the present invention; [Diagram 2] FIG. [Diagram 3] 4 is a flowchart of a reading process of the image reading device. [Figure 4] 13 is a flowchart of a reading process of an image reading device according to a modified example. [Diagram 5] 13 is a flowchart of a reading process of an image reading device according to a modified example. [Figure 6] 13 is a flowchart of a reading process of an image reading device according to a modified example. [Figure 7] Fig. 7A is a schematic diagram showing a read target, Fig. 7B is a schematic diagram showing a conventional reading process, and Fig. 7C is a schematic diagram showing the reading process of this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of an image reading device according to one embodiment of the present invention, and FIG. 2 is a schematic diagram showing a reading unit. It is. The image reading device 10 includes a reading unit 11 that reads a document, a double feed detection unit 12, and a control unit 13. The reading unit 11 includes a transparent member 16 and a background plate 17 that face each other, and the document P that is transported along the transport direction D is sandwiched between them and transported. The transparent member 16 is formed of glass, for example. The reading unit 11 is disposed on the opposite side of the transparent member 16 to the side on which the background plate 17 is located. The background plate 17 is a member of a predetermined color, for example, a gray color of a predetermined density, and is irradiated by a light source 11a included in the reading unit 11. The reading unit 11 reads the document by receiving reflected light (reflected light from the background plate 17 or the document P) of the light irradiated from the light source 11a with an imaging element (also called a reading element) 11b facing the document.

[0013] The imaging element 11b is a line sensor consisting of multiple imaging elements (pixels) arranged in a direction perpendicular to the transport direction D (direction perpendicular to the paper surface of FIG. 2), and reads one line of an image in one reading operation. The reading unit 11 obtains a two-dimensional reading result, that is, a reading result of the entire surface of the original P, by repeating the reading of one line at a predetermined frequency. Although FIG. 2 shows a configuration for reading one surface of the original P (the surface facing downward in FIG. 2), it goes without saying that the image reading device 10 may also be a scanner capable of reading both surfaces simultaneously, which also has a configuration for reading the other surface of the original P (the surface facing upward in FIG. 2).

[0014] Here, the light source 11a is located upstream of the image sensor 11b with respect to the conveying direction D, and the light emitted from the light source 11a casts a shadow downstream of the leading edge of the document P. The length of the shadow is proportional to the thickness of the document P at the image capturing position of the image sensor 11b. In addition, the thicker the document, the longer the shadow, and the darker the shadow tends to be. This is because it is presumed that the thicker the document, the more difficult it is for light to pass through the document, and as a result, the darker the shadow of the document cast on the background board 17 becomes. Therefore, the control unit 13 specifies the pixel value of the darkest part among the pixel values ​​of the shadow of the document P. As described above, the thickness of the document P can be measured or estimated based on the pixel values ​​of the shadow captured by the image sensor 11b. The thickness estimation process based on the pixel values ​​of the shadow is described in detail in JP 2018-195960 A.

[0015] In this way, the control unit 13 compares the pixel value of the darkest part among the pixel values ​​of the shadow with a predetermined threshold value. The double feed detection unit 12 is composed of an ultrasonic transmitter and receiver that face each other across the transport path. Based on the degree of attenuation of ultrasonic waves when the document P passes between the transmitter and receiver, it determines whether the document P is one or multiple documents passing through, and if multiple documents are passing through, it detects the document P as a double feed.

[0016] The control unit 13 controls the entire image reading device 10, which includes the reading unit 11, the double feed detection unit 12, the display unit 14, and the paper discharge unit 15. The display unit 14 also serves as a touch panel type operation unit, and the paper discharge unit 15 also serves as a transport unit that transports the document P. 3 is a flowchart showing the reading process of the image reading device. Hereinafter, the image reading process of the image reading device will be described, mainly with respect to the process in the case of detecting multiple feed, with reference to this flowchart.

[0017] In step S100, control unit 13 causes multi-feed detection unit 12 to start a multi-feed detection operation. Control unit 13 monitors the detection results by multi-feed detection unit 12, and when multi-feed detection unit 12 detects a multi-feed, in step S102 it determines that an error has occurred. However, at this point in time, it does not immediately determine that a multi-feed has occurred, but rather performs leading edge shadow detection in step S104. Lead edge shadow detection is a process that determines the thickness of document P based on the pixel value of the shadow that appears at the leading edge of document P detected by reading unit 11.

[0018] The reading unit 11 can capture an image of a shadow that occurs at the leading edge of the document P, and the control unit 13 estimates the thickness of the document P based on the pixel value of the shadow. Once the thickness is obtained, it is compared with a predetermined threshold value, and if it is smaller than the threshold value, it is determined to be thin paper, and if it is larger than the threshold value, it is determined to be thick paper. Then, if it is determined to be thin paper in the thick paper determination in step S106, it is determined again to be a multi-feed error in step S108, and is displayed on the display unit 14. If it is determined to be a multi-feed error, the conveyance is stopped at that point, and the user is required to resolve the multi-feed state, and the reading is awaited to be resumed. Thus, in this example, the display unit 14 is provided, and the control unit 13 displays the occurrence of a multi-feed when it determines that a multi-feed has occurred. It is also possible to display this when a multi-feed is detected in step S102 (step S103).

[0019] On the other hand, if it is determined in step S106 that the paper is thick paper, the control unit 13 turns off the multi-feed detection in step S110. That is, although it was determined that a multi-feed occurred in step S102, the control unit 13 turns off the multi-feed detection in order to ignore this determination in step S110, waits until the paper passing is completed in step S112, and when the paper passing is completed, turns the multi-feed detection back on in step S114.

[0020] In this example, the multi-feed detection is turned on when the passing of the document for which the multi-feed has been detected is completed, but the multi-feed detection may also be turned on when the next document is fed. FIG. 5 is a flowchart of a reading process of an image reading device according to a modified example. In this example, during continuous paper feeding, if multi-feed detection unit 12 detects multi-feed (step S102) and the pixel value of the read shadow does not exceed a predetermined threshold (step S106: determined to be thin paper), control unit 13 determines that multi-feed has occurred (step S108), and then feeds the next document in step S300.When paper feeding is complete, control unit 13 starts detecting multi-feed by multi-feed detection unit 12 by turning it ON in step S302.

[0021] Thus, in this embodiment, when a multi-feed is detected by the multi-feed detection unit 12 and the pixel value of the read shadow exceeds a predetermined threshold (when it is determined to be thick paper), it is not determined to be a multi-feed (steps S102, S106, S110), but when a multi-feed is detected by the multi-feed detection unit 12 and the pixel value of the read shadow does not exceed the predetermined threshold (when it is determined to be thin paper), it is determined to be a multi-feed (steps S102, S106, S108).

[0022] In this example, the control unit 13 has a procedure in which, after the multi-feed detection unit 12 detects the multi-feed, the reading unit 11 reads the shadow of the document that appears on the background plate 17 . Then, if the pixel value of the shadow read by the reading unit 11 exceeds a predetermined threshold, the control unit 13 can be said to have stopped detection of multi-feed by the multi-feed detection unit 12.

[0023] Incidentally, it is also possible to determine whether the paper is a thick sheet or not before detecting double feed. In this case, the double feed detector 12 is located downstream of the reader 11. 4 is a flowchart showing the reading process of the image reading device according to this modified example. In this embodiment, in step S200, the leading edge shadow detection process performed in step S104 is performed. In step S202, the thick paper determination performed in step S106 is performed. If the paper is thick, the result of the multi-feed detection by the multi-feed detection unit 12 is essentially ignored, and the multi-feed detection process ends.

[0024] On the other hand, if the paper is determined to be thin paper in the thick paper determination in step S202, multi-feed detection in step S100 is started in step S204, and the multi-feed detection determination in step S102 is performed in step S206. The result of multi-feed detection by multi-feed detection unit 12 is awaited, and if multi-feed is not detected, the multi-feed detection process ends. On the other hand, if multi-feed is detected, the multi-feed error notification performed in step S108 is performed in step S208, and the multi-feed detection process ends by awaiting the completion of paper passing performed in step S112 in step S210.

[0025] Thus, in this embodiment, control unit 13 reads the shadow of document P on background board 17 with reading unit 11, and when the pixel value of the shadow does not exceed a predetermined threshold (determined as thin paper), determines that a multifeed has occurred when multifeed detection unit 12 detects a multifeed. On the other hand, when the pixel value of the shadow exceeds a predetermined threshold (determined as thick paper), it does not determine that a multifeed has occurred even if multifeed detection unit 12 detects a multifeed. In this embodiment, control unit 13 does not obtain the detection result of multifeed detection unit 12, and therefore does not determine that a multifeed has occurred even if multifeed detection unit 12 detects a multifeed.

[0026] FIG. 6 is a flowchart of a reading process of an image reading device according to a modified example. As an example of the case of continuous paper feeding, if the control unit 13 determines that a double feed has occurred during continuous paper feeding, the double-fed documents are discharged by the paper discharge unit 15, and paper feeding is interrupted before feeding the next document. For example, after detecting a double feed, when the document is determined to be thin paper in step S106, the control unit 13 waits for the completion of paper discharge by the paper discharge unit 15 in step S400, and once the paper is discharged, the control unit 13 interrupts paper feeding in step S402 and notifies the detection of a double feed in step S404.

[0027] Although up until now, when a double feed is detected, the paper passing and ejection are completed, the control unit 13 may be configured to interrupt the transport of the document midway when it determines that a double feed has occurred. FIG. 7 is a schematic diagram showing the improvement of the reading process of the present invention. In continuous paper feeding, as shown in FIG. 7A, it is assumed that the first and second sheets are plain paper, the third sheet is a plastic card, and the fourth sheet is plain paper.

[0028] With a conventional image reading device, as shown in Fig. 7B, the first and second sheets of plain paper are read without any problems and the feeding of the third plastic card begins. However, if a double feed is detected midway through the card reading, both the reading and feeding are interrupted, and the continuous feeding job comes to a halt.

[0029] In contrast, according to the present invention, as shown in Fig. 7C, the first and second sheets of plain paper are read without any problems, which is the same. Then, when feeding of the third plastic card begins, the multi-feed detection unit 12 detects the multi-feed, but the document is determined to be thick paper, so the multi-feed detection is turned off and it is not processed as a multi-feed. Then, when the paper feed is completed, the multi-feed detection is turned back on. Then, feeding of the fourth sheet of plain paper also begins, and since no multi-feed is detected, reading is completed. In this way, one job in which continuous paper feeding is performed can be completed to the end.

[0030] Features of the Invention 1) Double feed detection notification timing The timing of the double feed detection notification can be either immediately after detection or after ejection, but the present invention can handle either timing. In the case of a conventional example in which the shape of the paper is determined from an image, it is not possible to stop immediately after detecting double feed.

[0031] 2) Differences due to double feed detection patterns According to the prior art, when a multi-feed is detected, the multi-feed level is determined by the accumulation. It is disclosed that this makes it possible to determine whether the paper is thick or plain based on the continuity of the detection level. However, even if the paper is thick, it is not always possible to obtain a continuous multi-feed level depending on the material and conditions, so the method of determining based on the thickness of the paper itself, as in the present invention, is advantageous.

[0032] 3) Processing at the leading edge and in the middle of the paper In the present invention, detection is basically performed at the leading edge of the paper. However, cases can also be considered in which plain paper is transported with a thick paper photo attached. Even when detection is performed halfway through the paper, it is possible to perform detection in the same way, since a shadow is cast not on the background board 17 but on the document P being transported. In other words, even if a multi-feed is detected halfway through the document, it is possible to detect the thickness of the paper, and therefore, if the paper is thick, it is possible to avoid processing it as a multi-feed detection. In this way, it is possible to prevent false detection of double feed not only for mixed cards, but also for ordinary paper with photos attached or paper with thick paper stickers or the like attached.

[0033] 4) Carrier sheets When a carrier sheet is used, pattern detection is generally performed using a transmissive sensor to detect the carrier sheet. However, when thickness estimation is possible as in the present invention, the carrier sheet can be detected using a double feed detection pattern that combines paper thickness estimation and double feed detection. Therefore, the conventional detection mechanism using a transmissive sensor can be omitted.

[0034] As another modified example, an operation for designating the thickness of the document may be accepted, and when the accepted thickness corresponds to thick paper, the multi-feed detection section may not detect multi-feed. This imaging device includes a reading unit that reads an original, a background plate that forms the background of the original, a multi-feed detection unit that detects multi-feeding of the original, an operation unit that accepts setting operations, and a control unit. The control unit causes the reading unit to read the shadow of the original that appears on the background plate. The control unit also accepts an operation that specifies the thickness of the original, and when the accepted thickness corresponds to thick paper, the control unit does not detect multi-feeding. The operation unit is realized by a touch panel display unit 14.

[0035] It goes without saying that the present invention is not limited to the above-mentioned embodiment. -Appropriately change and apply the mutually replaceable members and configurations disclosed in the above embodiments. · Appropriately replacing members and configurations that are not disclosed in the above embodiments but are publicly known and can be mutually substituted for the members and configurations disclosed in the above embodiments, and changing the combinations thereof for application. - Substitute members and configurations, etc. that are not disclosed in the above embodiments but that a person skilled in the art could imagine as substitutes for the members and configurations, etc. disclosed in the above embodiments based on publicly known techniques, and change the combinations and apply the present invention. is disclosed as one embodiment of the present invention. In addition, since the image reading device undergoes a number of steps in its processing, it is possible to grasp the concept of the invention as a method. Therefore, the image reading method is also disclosed. [Explanation of symbols]

[0036] 10...image reading device, 11...reading section, 11a...light source, 11b...imaging element, 12...multiple feed detection section, 13...control section, 14...display section, 15...paper discharge section, 16...transparent member, 17...background plate.

Claims

1. A reading unit that reads a document; A background plate that serves as a background for the document; a multi-feed detection unit for detecting multi-feeding of the document; A control unit and an image reading device comprising: The control unit is The shadow of the document that appears on the background plate is read by the reading unit; When the multifeed detection unit detects a multifeed and the pixel value of the shadow that is read is the smallest, When the pixel value of the dark portion exceeds a predetermined threshold, it is not determined that a double feed has occurred. When the multifeed detection unit detects a multifeed and the pixel value of the shadow that is read is the smallest, An image reading method comprising: determining that a double feed has occurred if the pixel value of a dark portion does not exceed a predetermined threshold value; Device.

2. The control unit detects a double feed by the double feed detection unit, and detects a document that is generated on the background plate.

2. The image reading device according to claim 1, wherein the reading unit reads a shadow of the object.

3. The control unit reads a shadow of the document on the background plate by the reading unit, and calculates a pixel value of the shadow. When the pixel value of the darkest part of the image exceeds a predetermined threshold value, the multifeed detection unit Even if a double feed is detected, it is not judged as a double feed, and the pixel value of the darkest part of the shadow is determined to be equal to or larger than a predetermined threshold value. If the limit is not exceeded, it is determined that a double feed has occurred when the double feed is detected by the double feed detection unit.

2. The image reading apparatus according to claim 1, wherein the image reading apparatus comprises:

4. A display unit is provided, and the control unit displays the occurrence of a multi-feed when the control unit determines that a multi-feed has occurred.

4. The image reading device according to claim 1, wherein the image reading device is a digital camera.

5. The control unit is configured to determine whether a pixel value of the darkest part of the pixel values ​​of the shadow read by the reading unit is a predetermined pixel value. If the threshold value is exceeded, detection of double feed by the double feed detection unit is stopped. The image reading device according to any one of claims 1 to 4.

6. The control unit detects a double feed by the double feed detection unit during continuous paper feeding and If the pixel value of the darkest part of the pixel values ​​of the shadow does not exceed a predetermined threshold, it is determined that there is a double feed. and then, when the next document is fed, detection of double feed by the double feed detection unit is started.

6. The image reading device according to claim 1,

7. The reading unit reads an image of a shadow generated at the leading edge of the document by a reading element facing the document. Read it as a raw value, The control unit estimates a thickness of the document based on a pixel value of a darkest part among pixel values ​​of the shadow.

7. The image reading device according to claim 1, further comprising:

8. A paper discharge unit is provided, When the control unit determines that a double feed has occurred during continuous paper feeding, the control unit ejects the double-fed originals by the paper ejection unit. Paper, Any one of claims 1 to 7, characterized in that the feeding of the document is interrupted before the next document is fed. The image reading device according to any one of the preceding claims.

9. The control unit interrupts the transport of the document when it determines that a double feed has occurred. The image reading device according to any one of claims 1 to 7.

10. A reading unit for reading an original, a background plate for forming a background of the original, and a double feed detector for detecting double feeding of the original An image reading method for an image reading device including a feed detection unit and a control unit, comprising: reading a shadow of the document that appears on the background plate by the reading unit; When the multifeed detection unit detects a multifeed and the pixel value of the shadow that is read is the smallest, When the pixel value of the dark portion exceeds a predetermined threshold, it is not determined that a double feed has occurred. In addition, when the multifeed is detected by the multifeed detection unit and the pixel value of the read shadow is If the pixel value of the darkest part does not exceed a predetermined threshold value, it is determined that a double feed has occurred. An image reading method comprising the steps of:

Images