Image processing device, image forming device and method

Abstract

To accurately detect multi-feeding of sheets even if the sheets have low transmissivity.SOLUTION: An image processing apparatus of the present invention has: a light source unit that radiates light; an image pickup unit that picks up an image of a subject based on the light radiated from the light source unit and reflected on the subject; a background unit that is located on the back side of the subject when the image pickup unit picks up the image and has light absorption properties in an arbitrary wavelength region; an image density detection unit that detects density information on the image; and an image analysis unit that analyzes the state of the subject based on the density information on the image.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an image processing apparatus, an image forming apparatus and a method. [Background technology]

[0002] Conventionally, there is a technique for detecting double feeding of paper using the results of reading an image of the paper.

[0003] For example, Patent Document 1 discloses a technique for detecting double feed by reading a sheet of paper to obtain an image, and comparing the image density with an image read from another sheet of paper to detect double feed. Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional configuration, there is a problem that the accuracy of detecting double paper feed decreases when paper with low transparency is used.

[0005] The present invention has been made in consideration of the above, and aims to provide an image processing device, an image forming device, and a method that are capable of accurately detecting double-feeding of paper, even when the paper has low transparency. [Means for solving the problem]

[0006] In order to solve the above problems and achieve the object, the image processing device of the present invention comprises: Includes at least the invisible wavelength range of light a light source unit for irradiating light, and a light source unit for detecting the light reflected from the object based on the light reflected from the object; Body an image capturing unit for capturing an image; The subject is located on the rear side of the subject when capturing an image of the subject, At least the invisible Absorbs light in the wavelength range Contains light absorbing regions A background part; The image capturing unit captures an invisible image based on the reflected light from the subject using the invisible wavelength range light, and the image capturing unit captures an invisible image based on the reflected light from the subject using the invisible wavelength range light. The image processing apparatus is characterized by comprising an image density detection section that detects density information of an image, and an image analysis section that analyzes the state of the subject based on the density information of the image. Effect of the Invention

[0007] According to the present invention, it is possible to accurately detect double feeding of papers even when the papers have low transparency. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 illustrates an example of a device configuration of an image processing device according to a first embodiment. [Diagram 2] FIG. 2 is a diagram illustrating an example of the configuration of the reading unit. [Diagram 3] FIG. 3 is a functional block diagram showing an example of a configuration for detecting double feed in a reading device. [Figure 4] FIG. 4 is a diagram showing an example of the configuration of an absorbing background portion. [Diagram 5] FIG. 5 is a conventional comparison diagram of an optical model showing the reflection of light when a single document is fed and when two documents are fed at the same time. [Figure 6] FIG. 6 is a diagram of an optical model showing the reflection of light in a light-absorbent background portion. [Figure 7] FIG. 7 is a diagram showing a configuration of a first embodiment in which a reading device detects double feed. [Figure 8] FIG. 8 is a diagram showing the relationship between the spectral reflectance of single-feed and double-feed of the same thick paper when an original is read against a light-absorbent background. [Figure 9] FIG. 9 is a diagram showing a configuration of a reading device according to a second embodiment in which double feed detection is performed. [Figure 10] FIG. 10 is a diagram showing the relationship between the spectral reflectance of single-feed and double-feed of the same thick paper when an original is read against a light-absorbent background. [Figure 11] FIG. 11 is a diagram for explaining how the use of a light-absorbent background portion improves detection accuracy not only for low-transmittance paper but also for other types of paper. [Figure 12] FIG. 12 is a diagram for explaining how the detection accuracy of recycled paper, which is a type of paper with low transparency, is improved by using an absorbing background. [Figure 13]FIG. 13 is a diagram showing a configuration of a third embodiment in which a reading device detects double feed. [Figure 14] FIG. 14 is a diagram showing an example of an image sensor on a sensor board. [Figure 15] FIG. 15 is a diagram showing an example of the spectral reflectance characteristics of a background portion that has absorbency only for invisible light. [Figure 16] FIG. 16 is a diagram showing a configuration of a reading device according to a fourth embodiment in which double feed detection is performed. [Figure 17] FIG. 17 is a diagram showing an example of the configuration of a reading device according to a fifth embodiment in which double feed detection is performed. [Figure 18] FIG. 18 is a diagram showing an example of the results of actually measuring the spectral reflectance of a normal background and an absorbing background for single-feed and multiple-feed OHP sheets. [Figure 19] FIG. 19 is a diagram showing an example of the results of actually measuring the spectral reflectance of a normal background and an absorbing background for single-feed and double-feed OHP sheets. [Figure 20] FIG. 20 is a diagram showing an example of the results of actually measuring the spectral reflectance of a normal background and an absorbing background for single-feed and double-feed OHP sheets. [Figure 21] FIG. 21 is a diagram showing an example of the results of actually measuring the spectral reflectance of a normal background and an absorbing background for single-feed and double-feed OHP sheets. [Figure 22] FIG. 22 is a diagram showing an embodiment of the image analysis unit. [Figure 23] FIG. 23 is a diagram showing another embodiment of the image analysis unit. [Figure 24] FIG. 24 is a diagram illustrating a specific example of the state detection process. [Diagram 25] FIG. 25 is a diagram illustrating another example of the state detection process. [Figure 26] FIG. 26 is a diagram illustrating another example of the state detection process. [Figure 27] FIG. 27 is a diagram illustrating another example of the state detection process. [Figure 28]FIG. 28 illustrates an example of a configuration of an image forming apparatus according to the second embodiment. As illustrated in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of an image processing device, an image forming device, and a method will be described in detail with reference to the attached drawings. In the following, the term "visible" refers to a wavelength range of visible light (visible wavelength range), and "invisible" refers to a wavelength range other than visible light, such as infrared light or ultraviolet light.

[0010] (First embodiment) Fig. 1 is a diagram showing an example of the configuration of an image processing device according to the first embodiment. Fig. 1 shows the configuration of an image processing device (hereinafter, referred to as a "reading device") provided with a reading unit as an example. Here, the configuration of a reading device equipped with a reading unit is shown, but the reading device and the image processing device may be provided separately from the reading unit.

[0011] The reading device body 10 has a contact glass 11 on its upper surface, and has a light source 13, a first carriage 14, a second carriage 15, a lens unit 16, a sensor board 17, etc. inside the reading device body 10. In Fig. 1, the first carriage 14 has the light source 13 and a reflecting mirror 14-1, and the second carriage 15 has reflecting mirrors 15-1 and 15-2.

[0012] Light from the light source 13 is irradiated onto the object to be read, and the light reflected from the object to be read is reflected by mirror 14-1 of the first carriage 14 and mirrors 15-1 and 15-2 of the second carriage 15 and enters lens unit 16, and an image of the object to be read is formed on the light receiving surface of sensor board 17 from lens unit 16. Sensor board 17 has a line sensor such as a CCD (Charge Coupled Device) or CMOS (Complementary MOS), and converts the image of the object to be read formed on the light receiving surface of the line sensor into electrical signals in sequence. Reference white plate 12 is a white density reference member that is read to correct changes in the amount of light from light source 13 and variations in the pixels (pixel circuits) of the line sensor.

[0013] The reading device 1 is provided with a control board in the reading device main body 10, and controls each part of the reading device main body 10 and each part of the ADF 20 to read the reading target in a predetermined reading method. The reading target is, for example, a recording medium on which characters, pictures, etc. are formed, or a recording medium before image formation. In the following, this recording medium is called an original. The original corresponds to the "subject", and will be described as paper or a transparent sheet (such as an OHP sheet) as an example, but is not limited to these.

[0014] An ADF (Automatic Document Feeder) 20 is mounted on the top of the reading device main body 10. The reading device 1 uses the ADF 20 to read the original 100 by a sheet-through method. The ADF 20 is an example of a "conveying section." In the configuration shown in FIG. 1, the reading device 1 separates the original 100 one by one from a stack of originals on a tray 21 of the ADF 20 by a pickup roller 22, conveys the original 100 to a conveying path 23, reads the surface of the original 100 to be read at a reading position of the reading section, and discharges the original 100 to a paper output tray 25. The original 100 is conveyed by the rotation of various conveying rollers 24.

[0015] The reading device 1, for example, moves the first carriage 14 and the second carriage 15 to a predetermined home position and fixes them, and while they are fixed, passes the original 100 between the reading window 19 and the background section 26 of the reading unit. The reading window 19 is a slit-shaped reading window provided in part of the contact glass 11. The background section 26 is a member located opposite the reading window 19. While the original 100 passes through the reading window 19, the reading unit irradiates light from the light source 13 onto a first surface (front or back surface) of the original 100 facing the reading window 19, and receives the reflected light with a line sensor on the sensor board 17 to read the image.

[0016] Here, the light source 13, the background unit 26, the optical system (mirror 14-1, mirrors 15-1 and 15-2, lens unit 16, etc.) that guides the reflected light from the original 100 to the line sensor of the sensor board 17, and the line sensor are described as a reading unit (first reading unit). The configuration of the reading unit will be described again with reference to FIG. 3.

[0017] When reading both sides of the document 100, for example, an inversion mechanism that inverts the document 100 is provided. The reading device 1 is provided with an inversion mechanism to invert the document 100 and read the second side of the document 100 at the reading position (reading window 19) of the reading unit. The second side may be read by other configurations, such as a second reading unit, instead of the inversion mechanism. For example, after the document 100 passes through the reading window 19, the second side of the document 100 is read by a reading unit (second reading unit) that has a reading sensor provided on the back side of the document 100. In this case, a member located opposite the reading sensor corresponds to the background portion.

[0018] The configuration of the reading device 1 of this example also allows flatbed reading. Specifically, the ADF 20 is lifted to expose the contact glass 11, and the document 100 is placed directly on the contact glass 11. Then, the ADF 20 is lowered to its original position, and the back side of the document 100 is pressed by the lower part of the ADF 20. In the flatbed method, the document 100 is fixed, so the carriage (first carriage 14, second carriage 15) is moved relative to the document 100 to perform scanning. The first carriage 14 and the second carriage 15 are driven by a scanner motor 18 to scan the document 100 in the sub-scanning direction. For example, the first carriage 14 moves at a speed V, and at the same time, the second carriage 15 moves in conjunction with it at a speed 1 / 2V, half that of the first carriage 14, to read the first surface of the document 100 on the contact glass 11 side. In this case, the lower part of the ADF 20 (a member that presses the document 100 from the back side) corresponds to the background part.

[0019] In this example, the first carriage 14, the second carriage 15, the lens unit 16, the sensor board 17, etc. are shown separately, but these may be provided separately or as an integrated sensor module.

[0020] 2 is a diagram for explaining an example of the configuration of a reading unit. As an example, the configuration and transport mechanism of a reading unit 30 (first reading unit) that reads a first side of a document 100 are shown. As shown in FIG. 2, the document 100 is transported by various transport rollers 24 and passes between the reading position (reading window 19) of the contact glass 11 and the background portion 26.

[0021] The reading unit 30 has a set with a background unit 26, and when the light source 13 is turned on, while the original 100 passes through the reading window 19, the reflected light of the light source 13 from the first side of the original 100 facing the reading window 19 is received by a line sensor on the sensor board 17 via a path shown by a dotted line in Figure 2, and the image is read.

[0022] The configuration of the reading unit is not limited to that of the first reading unit, and may be modified as appropriate according to the configuration of the reading device, such as a method of reading using a contact type image sensor as in the second reading unit.

[0023] (Double feed detection) Next, a description will be given of a typical configuration for detecting a state such as a multiple feed of the original 100 in the reading device 1. In a device that separates and transports the original 100 one sheet at a time from a stack of originals like the reading device 1, if separation fails, multiple sheets (for example, two sheets) are transported in an overlapping state, resulting in a so-called multiple feed state.

[0024] Fig. 3 is a functional block diagram showing an example of a configuration for detecting double feed in the reading device 1 according to the present embodiment. Fig. 3 shows a light source unit 31, an image capturing unit 32, an absorbing background unit 26, an image density detection unit 33, and an image analysis unit 34 as main functional units related to double feed detection. The light source unit 31, the image capturing unit 32, and the absorbing background unit 26 are functional units included in the reading unit 30. The image density detection unit 33 and the image analysis unit 34 are functional units provided on the sensor board 17 or the control board by an ASIC (Application Specific Integrated Circuit) or the like. The image density detection unit 33 and the image analysis unit 34 may be realized as functional units by a CPU (Central Processing Unit) of the control board or the like executing a program in a memory.

[0025] The light source unit 31 has a light source 13 (see FIG. 2) and a light source control unit that controls the light source 13, and controls turning the light source 13 on and off.

[0026] The image capturing unit 32 is the sensor board 17 (see FIG. 1) and has an image capturing sensor such as a CCD or CMOS (a line sensor, for example). The image capturing unit 32 drives the line sensor and captures an image by receiving reflected light from the object to be read on an imaging surface.

[0027] The image density detection unit 33 performs density detection processing from the image (image data) of the reading target (original 100) output from the image capturing unit 32. The density detection processing is processing for detecting density information from a specified area in the image. For example, the image density detection unit 33 detects the density level of the read value of the image area in the center of the original 100.

[0028] The image analysis unit 34 analyzes whether the document 100 is in a state of multiple feeding based on the density level obtained by the density detection process.

[0029] The absorbing background portion 26 corresponds to the background portion 26 (see FIG. 2) and has a high light absorbing function.

[0030] FIG. 4 is a diagram showing an example of the configuration of the absorbing background portion 26. The absorbing background portion 26 shown in FIG. 4 has a light-absorbing background portion 260. The light-absorbing background portion 260 is made of a coloring material such as carbon black (hereinafter collectively referred to as "black") that absorbs light. The wavelength range in which the light-absorbing background portion 260 absorbs light is arbitrary, and the wavelength range may be set by selecting an appropriate coloring material. The light-absorbing background portion 260 may be provided in a range that fills at least a part (for example, the center) of the imaging range captured by the image capturing portion 32. When the light-absorbing background portion 260 is provided in a part of the range, the light that has passed through the original 100 is absorbed in the light-absorbing background portion 260 and is reflected by the other background portions (for example, a white background). The reason why the condition for providing the light-absorbing background portion 260 is set to fill at least the center of the imaging range of the image capturing portion 32 is that the image density fluctuates less in the center portion. The location of the light-absorbent background portion 260 may be changed as appropriate and not limited to the central portion as long as the fluctuation in image density is small. Also, the light-absorbent background portion 260 may be provided over the entire background portion so as to fill the entire area of ​​the imaging range of the image imaging unit 32.

[0031] Fig. 5 is a comparative diagram of conventional optical models showing the reflection of light when the document 100 is fed in a single sheet and when two sheets are fed in a double sheet. The optical model is shown when the background is white. Fig. 5(a) shows the optical model in the case of single feeding, and Fig. 5(b) shows the optical model in the case of double feeding.

[0032] As shown in FIG. 5(a), when the original 100 is a single sheet of original 100-1, the light from the light source 13 becomes a reflected component p1 that is reflected by the first surface of the original 100-1 and a reflected component p2 that passes through the original 100-1 and is reflected by the background portion 26, and enters the line sensor.

[0033] On the other hand, when the original 100 consists of two sheets, 100-1 and 100-2, as shown in FIG. 5(b), the light from the light source 13 enters the line sensor as a reflection component p1 reflected by the first sheet of original 100-1, a reflection component p3 that passes through the first sheet of original 100-1 and is reflected by the second sheet of original 100-2, and a reflection component p4 that also passes through the second sheet of original 100-2 and is reflected by the background portion 26.

[0034] In this way, the reflected components are different even for the same light when single feeding and when multiple feeding are performed, and the density values ​​read by the line sensor are as follows.

[0035] Concentration value for single feed: p1+p2 Density value when multiple sheets are fed: p1+p3+p4

[0036] Here, the reflected component p4 is ignored because it is a reflected component that has passed through the original 100 four times. Also, if the light absorbency of the original 100 is ignored, if there is a sufficient difference between the reflected components p2 and p3, then there will be a difference in level between single feed and multiple feed, and therefore it will be possible to determine whether the document is being fed single or multiple by checking the density value.

[0037] Incidentally, the reflected components p2 and p3 are reflected light components that have passed through the original 100 twice. Therefore, if the original 100 is thick paper or the like, the light transmittance is low, i.e., the transmittance is low, and the difference between the reflected components p2 and p3 is small. If the original 100 is poorly transmittable, such as thick paper, it is difficult to detect double feeding of the thick paper in the optical model shown in Fig. 5. Therefore, in this embodiment, a light-absorbent background portion 260 is applied.

[0038] Fig. 6 is a diagram of an optical model showing the reflection of light in the light-absorbent background portion 260 of the background portion 26. Fig. 6(a) shows the optical model in the case of single feeding, and Fig. 6(b) shows the optical model in the case of multiple feeding.

[0039] 6(a), when the original 100 is a single sheet of original 100-1, the light from the light source 13 becomes a reflected component p1 that is reflected by the first surface of the original 100-1. Since the light (light component p1-1) that passes through the original 100-1 is absorbed by the light-absorbent background portion 260, the value of the reflected component p2 that is reflected by the background portion 26 is assumed to be "0", and the reflected component p1 enters the line sensor.

[0040] 6B, when the original 100 consists of two sheets, 100-1 and 100-2, the light (light component p2-1) of the light from the light source 13 that passes through the second sheet of the original 100-2 is absorbed by the light-absorbent background portion 260. For this reason, the value of the reflection component p4 that passes through the second sheet of the original 100-2 and is reflected by the background portion 26 is also assumed to be "0." The reflection component p1 that is reflected by the first sheet of the original 100-1 and the reflection component p3 that is transmitted through the first sheet of the original 100-1 and is reflected by the second sheet of the original 100-2 are incident on the line sensor.

[0041] Concentration value during single feed: p1 Density value when multiple sheets are fed: p1+p3

[0042] Therefore, the difference in reflected light when there is one sheet of original 100 and when there are two sheets is reflected component p3 when light absorbent background portion 260 is provided, and when there is no light absorbent background portion 260, it is the background region of background portion 26 (white background region in this example), so it is the difference between reflected component p2 and reflected component p3. Here, reflected component p2 and reflected component p3 are reflected light, so they have a relationship of p2>0 and p3>0. Therefore, p3>0 for light absorbent background portion 260, and the difference in level between single feed and multiple feed is greater than p2-p3 for background portion 26 with a white background.

[0043] As described above, by using the light-absorbent background portion 260 in the background portion 26, the accuracy of detecting single and multiple feeds of the original 100 is improved, and therefore the accuracy of detecting single and multiple feeds is improved and detection is possible even for originals 100 with low light transmittance, such as cardboard.

[0044] In this way, the reading device 1 of this embodiment uses an absorbing background portion 26 with high light absorption in the background portion, making it possible to detect single feeding and double feeding regardless of the light transmittance of the original 100. By providing light absorption to the background portion, it is possible to increase the difference in the reflected light received during single feeding and double feeding, making it possible to detect a double feeding state such as low-transmittance cardboard that could not be detected in the past. Note that the reading device 1 needs to be configured according to the wavelength range that absorbs the light of the light-absorbent background portion 260. Therefore, examples according to the wavelength range are shown below.

[0045] Example 1 As a first embodiment, a configuration in which a light-absorbent background portion 260 having light absorbency in the visible light region is used will be described.

[0046] Fig. 7 is a diagram showing a configuration of Example 1 in which double feed detection is performed in the reading device 1. In Fig. 7, in the reading device 1 (see Fig. 3) according to the embodiment, the light source unit 31 is a visible light source unit 31a, the image capturing unit 32 is a visible image capturing unit 32a, and the absorbing background unit 26 is a visible absorbing background unit 26a. The visible absorbing background unit 26a has a light absorbent retaining background unit 260 that has light absorbency in the visible light region.

[0047] The visible light source unit 31a uses a visible light source in the visible wavelength range as the light source 13. The visible light source is, for example, an LED of R (Red), G (Green), or B (Blue). The visible image capturing unit 32a uses an imaging sensor in the visible wavelength range. The imaging sensor in the visible wavelength range is, for example, an imaging sensor of R (Red), G (Green), and B (Blue). In this configuration, the light of the visible light source is reflected from the original 100 against the visible absorbing background portion 26a, and the reflected light is incident on the imaging sensors of R (Red), G (Green), and B (Blue).

[0048] The visible image density detection section 33a performs density detection processing from the visible image output from the visible image capture section 32a.

[0049] The image analysis unit 34 analyzes whether the document 100 is in a state of multiple feeding based on the density level obtained by the density detection process.

[0050] FIG. 8 is a diagram showing the relationship between the spectral reflectance of single feeding and multiple feeding of the same thick paper when the original 100 is read against the light-absorbing background portion 260 of the first embodiment. In FIG. 8, the horizontal axis represents the wavelength of light, and the vertical axis represents the reflectance (100%), and the measurement results of the reflectance of the light irradiated on the original 100 are shown. As an example, a black background is applied to the light-absorbing background portion 260. Graph f1 shows the measurement results when multiple feeding occurs, and graph f2 shows the measurement results when single feeding occurs. From the measurement results shown in FIG. 8, it can be seen that a difference occurs between the reflectance of single feeding and multiple feeding within the visible wavelength range. In particular, in this example, it can be seen that the difference in reflectance increases when the wavelength exceeds around 600 nm. Therefore, the image analysis unit 34 detects multiple feeding by analyzing the density level of the image in the visible wavelength range exceeding around 600 nm obtained by the density detection process.

[0051] Example 2 As a second embodiment, a configuration in which a light-absorbent background portion 260 having light absorbency in the invisible light region is used will be described.

[0052] Fig. 9 is a diagram showing a configuration of Example 2 in which double feed detection is performed in the reading device 1. In Fig. 9, in the reading device 1 (see Fig. 3) according to the embodiment, the light source unit 31 is an invisible light source unit 31b, the image capturing unit 32 is an invisible image capturing unit 32b, and the absorbing background unit 26 is an invisible absorbing background unit 26b. The invisible absorbing background unit 26b has a light-absorbent background unit 260 that has light absorbency in the invisible light region.

[0053] The invisible light source unit 31b uses an invisible light source in an invisible wavelength range as the light source 13. The invisible light source is, for example, a near-infrared LED. The invisible image capturing unit 32b uses an image sensor in an invisible wavelength range. The image sensor in the invisible wavelength range is, for example, an IR (near-infrared) image sensor.

[0054] The image density detection section 33 performs density detection processing from the invisible image output from the invisible image capturing section 32b.

[0055] The image analysis unit 34 analyzes whether the document 100 is in a state of multiple feeding based on the density level obtained by the density detection process.

[0056] FIG. 10 is a diagram showing the relationship between the spectral reflectance of single feeding and multiple feeding of the same thick paper when the original 100 is read against the light-absorbent background portion 260 of the second embodiment. As an example, a black background is applied to the light-absorbent background portion 260. Graph f1 shows the measurement result when multiple feeding occurs, and graph f2 shows the measurement result when single feeding occurs. From the measurement result shown in FIG. 10, it can be seen that a difference occurs between the reflectance of single feeding and multiple feeding within the invisible wavelength range. Therefore, the image analysis unit 34 detects multiple feeding by analyzing the density level of the image in the invisible wavelength range obtained by the density detection process.

[0057] FIG. 11 is a diagram for explaining that the detection accuracy is improved not only for low-transmittance paper by using the light-absorbent retaining background portion 260 of the second embodiment. FIG. 11(a) is a diagram showing the relationship between the spectral reflectance of plain paper (thin paper) in single feeding and double feeding on a normal white background (normal background). FIG. 11(b) is a diagram showing the relationship between the spectral reflectance of thin paper in single feeding and double feeding on a black background. When paying attention to the arrows in FIG. 11(a) and FIG. 11(b), it can be seen that the use of a black background causes a large change in the spectral reflectance from single feeding to double feeding in the invisible region. This is because the use of a black background reduces the reflected light from the background, so the difference in reflected light between the single feeding and double feeding becomes noticeable.

[0058] In addition, the larger the difference in reflected light between single feed and double feed, the larger the value for variation factors such as uneven reading and the influence of individual differences in the whiteness of the paper, which leads to a reduction in false detections when detecting the change between single feed and double feed. In this way, by using an absorbing background such as a black background, the detection accuracy can be improved even for paper other than those with low transparency.

[0059] Fig. 12 is a diagram explaining how the detection accuracy of recycled paper, which is a paper with low transparency, is improved by using an absorbing background. Fig. 12(a) is a diagram showing the relationship between the spectral reflectance of single-feed and double-feed recycled paper on a normal white background (normal background). Fig. 12(b) is a diagram showing the relationship between the spectral reflectance of single-feed and double-feed recycled paper on an absorbing background.

[0060] Besides cardboard, recycled paper is another example of paper with low transparency. When recycled paper is used against a normal background, the spectral reflectance changes only by about 2-3% from the visible to invisible range, even at the point where the change between single feeding and multiple feeding changes the most. This is because the reflected light from the second sheet of paper and the reflected light from the background are close. When used against an absorbing background, the difference in reflected light from the second sheet becomes more noticeable.

[0061] For this reason, as shown in Fig. 12(b), there is a large difference from the visible range to the invisible range in the absorbing background. In this way, by using an absorbing background such as a black background, the detection accuracy can be improved even for low-transparency materials such as recycled paper.

[0062] Example 3 In a reading device such as a scanner, there is a demand for detecting the state of the original 100 (whether it is a single-feed or multiple-feed state) while viewing the imaging result of the visible image of the original 100. Thus, a configuration for irradiating visible light and invisible light onto a background portion that absorbs light at least in the invisible range, and obtaining images obtained by imaging the visible light and invisible light, respectively, is shown as a third embodiment.

[0063] Fig. 13 is a diagram showing the configuration of a third embodiment in which double feed detection is performed in a reading device 1. In Fig. 13, a visible light source unit 31a and a visible image capturing unit 32a are further provided in addition to the configuration of the second embodiment (Fig. 9).

[0064] In the third embodiment, the visible light source unit 31a emits light, and the reflected light from the document 100 with the absorbing background portion 26 as the background is incident on the visible image capturing unit 32a, to obtain a visible image output result (visible image output) 200.

[0065] In addition, the invisible light source unit 31b is illuminated, and the reflected light from the original 100 with the absorbing background portion 26 as the background is incident on the invisible image capturing unit 32b, and based on the invisible image, the image density detection unit 33 and the image analysis unit 34 detect whether the original 100 is being fed singly or in multiples.

[0066] For the visible light source unit 31a and the invisible light source unit 31b, individual light sources specific to visible light and invisible light may be used, or one light source including visible light and invisible light may be used. For example, LEDs in the visible wavelength range (e.g., R (Red), G (Green), B (Blue), etc.) are used for visible light, and infrared LEDs or the like are used for invisible light. Also, a halogen lamp that covers both the wavelength ranges of visible light and invisible light may be used.

[0067] Fig. 14 is a diagram showing an example of an image sensor on a sensor board. Fig. 14 shows an example of an implementation having a three-channel line sensor of R (Red), G (Green), and B (Blue) for capturing visible images, and a one-channel line sensor of IV (Invisible) for capturing invisible images.

[0068] In this example, three channels are used to capture the visible image because it is a color image, but at least one channel is sufficient for capturing the visible image. For example, for a monochrome image, one channel is used for the visible image and one channel is used for the invisible image.

[0069] FIG. 15 is a diagram showing an example of the spectral reflectance characteristics of a background part that is absorbent only to invisible light. If a light-absorbing black background like that shown in FIG. 15 is used, when a visible image is read, the light reflectance from the background part decreases due to the light absorbency of the background part, and there is a possibility that the image quality will be significantly reduced. Therefore, as shown in the graph of the invisible absorbing background in FIG. 15, a background part that is absorbent only in the invisible wavelength range is used. In other words, by using a back part that is absorbent in the invisible wavelength range and reflects light in the visible wavelength range, it becomes possible to detect the state of multiple feeding without affecting the visible image.

[0070] By taking both a visible image and an invisible image as in the third embodiment, it is possible to detect a double feed state with high accuracy from the invisible image while observing the visible image result.

[0071] Example 4 Next, another embodiment will be described in which a background portion having absorbency only in the invisible range is used. Fig. 16 is a diagram showing the configuration of a fourth embodiment in which double feed detection is performed in a reading device 1. In Fig. 16, the absorbing background portion 26 shown in the configuration of the third embodiment (Fig. 13) is changed to an absorbing background portion 26c that exhibits light absorption only in the invisible range (invisible-only absorbing background portion).

[0072] By using the background portion that is absorbent only in the invisible range, the reflected component from the background portion becomes large in the visible range. As a result, the light that passes through the document 100 and is reflected by the background portion becomes large, and even thin paper with low transmittance can be read brightly. On the other hand, since there is little light reflected from the background portion in the invisible range, by using this region, it is possible to improve the paper type adaptability of the multi-feed detection. By using the background portion that is absorbent only in the invisible range in this way, it is possible to perform multi-feed detection that is highly adaptable to paper types while maintaining the quality of a normal visible image. Note that an image captured as an invisible image may be output.

[0073] Example 5 Next, an embodiment in which the state of multiple feeding is detected using the results of the visible image and the invisible image is shown. When using a background that absorbs only the invisible range, image state detection using only the results of the invisible image may not be able to detect the state of a highly transparent document such as an overhead projector sheet. This is because the document itself has almost no reflectance, and most of the light is absorbed by the invisible absorbing background, so the reflected components are small and there is no difference between single feeding and multiple feeding. On the other hand, because the background reflectance is high in the visible wavelength range, the amount of attenuation of the reflected light varies greatly depending on the number of overhead projector sheets.

[0074] Fig. 17 is a diagram showing an example of the configuration of the fifth embodiment in which double feed detection is performed in the reading device 1. Fig. 17 shows a modification in which the visible image output by the visible image capturing unit 32a shown in Fig. 16 is also output to the image density detection unit 33. The image density detection unit 33 uses the visible image and the invisible image, respectively, and detects the density level of each. This makes it possible for the image analysis unit 34 to detect whether double feed has occurred.

[0075] FIG. 18 is a diagram showing an example of the results of actually measuring the spectral reflectance of a normal background and an absorbing background for single-feed and multiple-feed OHP sheets.

[0076] With single feed (visible), the light passes through one OHP sheet and is reflected back, so the reflected light is higher than with multiple feed. With multiple feed (visible), the light passes through two OHP sheets and is reflected back, so the reflected light is lower than with single feed. With single feed (invisible), all the light that passes through the OHP sheet is absorbed, so the value is almost the same as with multiple feed. With multiple feed (invisible), all the light that passes through the OHP sheet is absorbed, so the value is almost the same as with single feed.

[0077] 19 to 21, in the case of a white background, a difference occurs between single feeding and multiple feeding for both visible and invisible wavelengths. In the case of an absorbing background, no difference occurs between single feeding and multiple feeding for both visible and invisible wavelengths.

[0078] Therefore, if a background portion that only absorbs invisible light is used, and a difference appears at visible wavelengths but no difference appears at invisible wavelengths, it can be detected that a highly transparent document such as an overhead projector sheet has been fed multiple times.

[0079] As described above, by using a combination of the invisible wavelength region and the visible wavelength region for the background portion that absorbs only invisible light and detecting the state by observing the difference in the visible region, the applicable range of documents can be increased.

[0080] (Image analysis section) Fig. 22 is a diagram showing an embodiment of the image analysis section 34. As shown in Fig. 22, the image analysis section 34 has an image density result comparison section 34-1 and a reference density holding section 34-2.

[0081] The reference density holding unit 34-2 holds the image density result for at least one frame, which is one frame or more before the image density result output from the previous stage. The reference density holding unit 34-2 can also update the held density reference result with the image density result for one frame that is sequentially output.

[0082] The image density result comparison unit 34-1 judges the state of the document by comparing the density reference result stored in the reference density storage unit 34-2 with the image density result output from the previous stage, and outputs the judgment result (state judgment result).

[0083] The status determination result is output to the overall control unit, etc., and if the status determination result indicates a double feed, for example, the overall control unit interrupts the subsequent reading process and ejects the document being read. Also, to inform the user that a double feed has occurred, the overall control unit may notify a display unit, etc. of an error indicating a double feed.

[0084] In this embodiment, a configuration is shown in which at least the previous reading result is compared with the current reading result (corresponding to the image density result of the "current frame"). By configuring in this way, it is possible to detect the state of the document while suppressing the influence of changes in the temperature characteristics of the sensor and dirt in the background.

[0085] FIG. 23 is a diagram showing another embodiment of the image analysis unit 34. In the configuration shown in FIG. 23, since the image density result is not stored in the reference density storage unit 34-2 in the processing of the first frame, the state of the document cannot be detected in the first frame. Therefore, a reference density setting unit 34-3 is provided as a "setting unit", and the result (corresponding to the image density result) registered in advance in the reference density setting unit 34-3 is set in the reference density storage unit 34-2 before the start of the processing of the first frame. With this configuration, it becomes possible to detect the state of the document by comparing the reading result of the first frame with the result registered in advance.

[0086] Fig. 24 is a diagram for explaining a specific example of the state detection process. Fig. 24 shows a comparison of image density results for the entire image as a specific example of the state detection process. The background is extracted from the entire read image 101 to obtain the background level of the entire image 101, and is compared with the background level of the entire image 102 that has been stored. The state of the original 100 is detected from the difference in the background level, which is the comparison result between the background level of the read image and the background level of the stored image.

[0087] This method requires only one value to be stored, which indicates the background level of the entire image, and the comparison can also be performed between two values ​​indicating the background level. This has the advantage that it can be implemented with a small amount of calculation without increasing the circuit scale.

[0088] The image described here refers to a visible image or an invisible image. When visible image density detection is used, it refers to a visible image, and when invisible image density detection is used, it refers to an invisible image.

[0089] 25 is a diagram for explaining another example of the state detection process. Here, as another example, a method for dividing the entire image into regions in the main scanning direction and acquiring the background level from the divided images will be explained.

[0090] Fig. 25 shows a diagram illustrating a division pattern when the image density detection unit 33 divides an image in the main scanning direction. In Fig. 25, the division patterns are arranged in the main scanning direction of the image. Specifically, the image density detection unit 33 divides the entire image into a plurality of regions in the short side direction (main scanning direction). Furthermore, the image density detection unit 33 extracts the background level for each divided region.

[0091] The image analysis unit 34 compares the background level of each region extracted by the image density detection unit 33 with a background level stored in advance (a background level extracted in advance from a divided region in another frame) to determine the state of the document for each region. The image analysis unit 34 detects the state of the document from the ratio of regions determined to be abnormal to the entire image (abnormal state determination rate).

[0092] The abnormal state determination rate can be calculated by the following formula (1), for example, where the number of divided areas is N and the number of areas where double feeding is detected is α.

number

[0093] When the abnormal state determination rate exceeds a certain threshold value according to formula (1), it is determined that a double feed has occurred.

[0094] Dividing the area in the main scanning direction in this way makes it possible to reduce the following factors and prevent erroneous judgments. One is the effect of variations in light in the main scanning direction. There is variation in the way light hits the area in the main scanning direction. By dividing the area in the main scanning direction and comparing areas that are hit by the same light, the effect of density variations due to variations in light in the main scanning direction can be reduced and erroneous judgments can be prevented. Another is reducing the effect of sticky notes or cut and pasted documents. If there are sticky notes or cut and pasted documents, a peculiar change occurs in the reflectance in the image area, which causes erroneous judgments. However, such peculiar areas are only a part of the entire area, so by dividing the area and taking the overall ratio, the effect is absorbed and it becomes possible to prevent erroneous judgments.

[0095] The image described here may refer to either a visible image or an invisible image. When visible image density detection is used, it refers to a visible image, and when invisible image density detection is used, it refers to an invisible image.

[0096] FIG. 26 is a diagram for explaining another example of the state detection process. Here, a method is described in which the entire image is divided into regions in the sub-scanning direction, instead of the region division in the main scanning direction shown in FIG. 25, and the background level is obtained from the divided images. The method for detecting the state by dividing the image into regions in the sub-scanning direction is mainly different from the method for detecting the state by dividing the image into regions in the main scanning direction explained in FIG. 25 in that the direction of division is the sub-scanning direction, not the main scanning direction. Because of the division in the sub-scanning direction, the division unit is, for example, one line unit or multiple lines unit, and it is possible to compare the divided regions with the same sub-scanning direction. Other than that, the content is almost the same as that explained in FIG. 25. That is, the image density detection unit 33 divides the entire image into multiple regions in the longitudinal direction (sub-scanning direction). Furthermore, the image density detection unit 33 extracts the background level for each divided region. The image analysis unit compares the background level of each region extracted by the image density detection unit 33 with a background level stored in advance (a background level extracted in advance from a divided region in the sub-scanning direction in another frame) to determine the state of the document for each region. The image analysis unit 34 detects the state of the document from the ratio of regions determined to be abnormal in the entire image (abnormal state determination rate). The abnormal state determination rate can be calculated, for example, by Equation (1). Further description will be omitted as it would be a repetition of the description of FIG. 25.

[0097] Note that when the area is divided in the sub-scanning direction, the following factors can be reduced and erroneous judgments can be prevented. One is the effect of the floating of the document. When a document is fed into the ADF, the leading edge of the document may float, and this floating effect changes the density. If the document is divided in the sub-scanning direction and judgment is made using each area, the floating effect is only a partial area of ​​the entire image, so by dividing the area and taking the overall ratio, this effect is absorbed and erroneous judgments can be prevented. Another is the reduction in the effect of sticky notes and cut-and-pasted documents. The reason why this effect is reduced is the same as in the explanation of Figure 25, and so an explanation will be omitted to avoid repetition.

[0098] FIG. 27 is a diagram for explaining another example of the state detection process. Here, a method of performing region division in the main scanning direction shown in FIG. 25 and region division in the sub-scanning direction shown in FIG. 26 will be described. That is, as in the lattice-shaped divided image shown in FIG. 27, the image density detection unit 33 acquires the background level from each divided image divided into the main scanning region and the sub-scanning direction. Note that the method of detecting the state by dividing the region in the main scanning direction and the sub-scanning direction is different from the method of detecting the state by dividing the region in the main scanning direction described in FIG. 25 in that the region division is also performed in the sub-scanning direction described in FIG. 26. Note that since the region division in the sub-scanning direction has been described in FIG. 26, the method of detecting the state from each divided image can be performed in substantially the same manner as the method described in FIG. 25. Therefore. Further description will be omitted since it would be a repetition of the description of FIG. 25.

[0099] Furthermore, by implementing this, it is possible to reduce both the factors that arise when dividing the area in the main scanning direction, as explained in Figure 25, and the factors that arise when dividing the area in the sub-scanning direction, as explained in Figure 26, thereby making it possible to further prevent erroneous judgments.

[0100] There are three methods for extracting the skin level, for example. One uses the average value of the target area as the skin level. Another uses the most frequent value of the target area as the skin level. Another uses the maximum value of the target area as the skin level. The target area is an area for which the skin level value is to be calculated individually, such as the entire image as described above, or each divided area when divided.

[0101] (Second embodiment) Fig. 28 is a diagram showing an example of a configuration of an image forming apparatus according to the second embodiment. In Fig. 28, an image forming apparatus 2 is an image forming apparatus generally called a multifunction peripheral (MFP) having at least two functions of a copy function, a printer function, a scanner function, and a facsimile function.

[0102] The image forming apparatus 2 has a reading device main body 10 which is a reading device, and an ADF 20, and has an image forming section 103 below them.

[0103] The ADF 20 feeds an original document, reads the side to be read at a reading position (reading window), and discharges the document onto a paper discharge tray. The reading device main body 10 reads the side to be read of the original document at the reading position. The ADF 20 is the ADF 20 (see FIG. 1) according to the first embodiment, and the reading device main body 10 is the reading device main body 10 (see FIG. 1) according to the first embodiment. The ADF 20 and the reading device main body 10 have already been described in the first embodiment. Therefore, further description of the ADF 20 and the reading device main body 10 will be omitted.

[0104] In FIG. 28, the image forming unit 103 has an external cover removed to explain the internal configuration so that the internal configuration can be seen. The image forming unit 103 prints an original image read by the reading device main body 10. The image forming unit 103 has a manual feed roller 104 for manually feeding recording paper, and a recording paper supply unit 107 for supplying recording paper. Here, recording paper is an example of a "medium". The recording paper supply unit 107 has a mechanism for feeding recording paper from a multi-stage recording paper feed cassette 107a. The supplied recording paper is sent to a secondary transfer belt 112 via a registration roller 108.

[0105] A toner image on the intermediate transfer belt 113 is transferred to the recording paper conveyed on the secondary transfer belt 112 in a transfer section 114 .

[0106] The image forming unit 103 also includes an optical writing device 109, tandem imaging units (Y, M, C, K) 105, an intermediate transfer belt 113, and the secondary transfer belt 112. Through an image creation process by the imaging units 105, an image (visible image) written by the optical writing device 109 is formed as a toner image on the intermediate transfer belt 113.

[0107] Specifically, the imaging unit (Y, M, C, K) 105 has four rotatable photoconductor drums (Y, M, C, K), and is provided with imaging elements 106 including a charging roller, a developing unit, a primary transfer roller, a cleaner unit, and a static eliminator around each photoconductor drum. The imaging elements 106 function for each photoconductor drum, and the image on the photoconductor drum is transferred onto the intermediate transfer belt 113 by each primary transfer roller.

[0108] The intermediate transfer belt 113 is stretched across a drive roller and a driven roller in the nip between each photosensitive drum and each primary transfer roller. The toner image primarily transferred onto the intermediate transfer belt 113 is secondarily transferred to the recording paper on the secondary transfer belt 112 by the secondary transfer device as the intermediate transfer belt 113 travels. The recording paper is transported to the fixing device 110 as the secondary transfer belt 112 travels, and the toner image is fixed onto the recording paper as a color image. The recording paper is then discharged to a paper discharge tray outside the machine. In the case of double-sided printing, the front and back of the recording paper are inverted by the inversion mechanism 111, and the inverted recording paper is sent onto the secondary transfer belt 112.

[0109] The image forming unit 103 is not limited to one that forms images by the electrophotographic method as described above, but may be one that forms images by an inkjet method.

[0110] Moreover, such a reading device configuration may be provided after the manual feed roller 104 for manually feeding recording paper, or on the transport path after the recording paper supply unit 107 has fed recording paper from the multi-stage recording paper feed cassette 107a. In this case, if multiple recording papers are fed, the user is notified of the abnormality before image formation on the recording paper, and it becomes possible to make an emergency stop.

[0111] Although the embodiment and modified examples of the present invention have been described above, the embodiment and examples are presented as examples and are not intended to limit the scope of the invention. These novel embodiments and examples can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and examples are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0112] 1 Reading device 26 Background section 30 Reading unit 31 Light source section 32 Image capture unit 33 Image density detection unit 34 Image Analysis Unit 260 Light-absorbing retaining background [Prior art documents] [Patent documents]

[0113] [Patent Document 1] JP 2019-080169 A

Claims

1. A light source unit that irradiates light including at least an invisible wavelength range of a light wavelength range; an image capturing unit configured to capture an image of a subject based on light reflected from the subject by light from the light source unit; a background portion that is located on a rear side of the subject when the image capturing unit captures an image of the subject, the background portion including a light absorbing region that has light absorbing properties at least in the invisible wavelength range; an image density detection unit that detects density information of an image corresponding to the light absorption region in an invisible image that is an image captured by the image capturing unit based on the reflected light from the subject using light in the invisible wavelength range; an image analysis unit that analyzes a state of the subject based on density information of the image; An image processing device comprising:

2. the background portion has the light absorbency in at least a region corresponding to a central portion of an imaging range of the image imaging portion; The image processing device according to claim 1 .

3. The light source unit irradiates invisible light which is light in the invisible wavelength range and visible light which is light in the visible wavelength range, The image capturing unit outputs the invisible image, which is an image captured based on the invisible light, and the visible image, which is an image captured based on the visible light.

3. The image processing device according to claim 1 or 2.

4. The light absorbing region has light reflectivity in the visible wavelength range and light absorbency in the invisible wavelength range. The image processing device according to claim 3 .

5. the image density detection unit detects density information of each of the visible image and the invisible image; the image analysis unit analyzes a state of the subject based on density information detected from the visible image and the invisible image, 5. The image processing device according to claim 3.

6. The density information of the visible image is density information of an image corresponding to an area having light reflectivity in the visible wavelength range. The image processing device according to claim 5 .

7. The image analysis unit a reference density storage unit that stores image density information that is density information of an image at least one frame before; an image density result comparison unit that compares image density information, which is density information of an image of a current frame, with the image density information stored in the reference density storage unit; analyzing a state of the subject based on a comparison result of the image density result comparison unit; 7. An image processing device according to claim 1.

8. The image analysis unit a reference concentration storage unit that stores setting information set by the setting unit; an image density result comparison unit that compares image density information of a current frame with the setting information stored in the reference density storage unit; analyzing a state of the subject based on a comparison result of the image density result comparison unit; 7. An image processing device according to claim 1.

9. The density information is background level information obtained from an entire area of ​​the captured image captured by the image capturing unit.

9. An image processing device according to any one of claims 1 to 8.

10. The density information is background level information for each region obtained by dividing the entire surface of the captured image captured by the image capturing unit in the main scanning direction.

9. An image processing device according to any one of claims 1 to 8.

11. The density information is background level information for each region obtained by dividing the entire surface of the captured image captured by the image capturing unit in the sub-scanning direction.

9. An image processing device according to any one of claims 1 to 8.

12. The density information is background level information for each region obtained by dividing the entire image captured by the image capturing unit in the main scanning direction and the sub-scanning direction.

9. An image processing device according to any one of claims 1 to 8.

13. The background level information is an average value, a mode value, or a maximum value for each area of ​​the entire captured image.

13. An image processing device according to any one of claims 10 to 12.

14. The image analysis unit detects the state of the subject based on a ratio of areas in which the value of skin level information for each skin level area extracted from the captured image is abnormal.

14. An image processing device according to any one of claims 10 to 13.

15. the image analysis unit detects that the state of the subject is a state of multiple feeding based on density information of the image. An image processing device according to any one of claims 1 to 14.

16. An image processing device according to any one of claims 1 to 15, an image forming unit that forms a captured image on a recording medium; An image forming apparatus comprising:

17. A method for detecting a state of a subject, comprising: a step of irradiating the subject with light including the invisible wavelength range with a background portion including a light absorbing region having light absorption properties in at least the invisible wavelength range of the light wavelength range as a back surface of the subject; capturing an image of the subject based on reflected light from the subject using light including the invisible wavelength range; detecting density information of an image corresponding to the light absorbing region in an invisible image that is an image captured based on the reflected light from the subject by the light in the invisible wavelength range; analyzing a state of the subject based on density information of the image; The method includes:

Images