Sheet identification device, image processing device, and sheet identification method

Abstract

This sheet determination device comprises an acquisition unit and an unevenness determination unit. The acquisition unit acquires a specific image (Im1). The specific image (Im1) is an image of a specific region (R1) of a surface (A1) of a sheet (Sh1) on which an image is to be formed or from which an image is to be read. The specific region (R1) is a region of the surface (A1) of the sheet (Sh1) where pattern light (P1) is being projected. The unevenness determination unit determines, on the basis of the specific image (Im1), unevenness information which pertains to unevenness of the surface (A1) of the sheet (Sh1).

Description

[Technical field]

[0001] The present invention relates to a sheet specifying device, an image processing device, and a sheet specifying method. [Background technology]

[0002] Related technology is known that is used in image forming devices such as copiers or laser printers to automatically identify the type of sheet (paper) from an image of the surface (see, for example, Patent Document 1). An image reading device according to the related technology includes a light emitting element that irradiates light onto the surface of the sheet from an oblique direction, and an area sensor that reads the illuminated area as an image, and reads information about the sheet from the reading results.

[0003] This image reading device estimates the surface roughness of a sheet by detecting the shadow image caused by the unevenness of the sheet surface from the image in the illuminated area. When the sheet surface has large unevenness, the contrast is higher than when the unevenness is small, so the magnitude of the surface unevenness can be estimated from the contrast. Furthermore, this image reading device maintains the sheet fiber direction and the light incident direction at approximately 45 degrees by setting the incident direction of the light from the light emitting element at an angle of 45 degrees to the sheet transport direction, resulting in a configuration with little variation in detection accuracy due to the fiber direction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-038879 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the configuration of the above-mentioned related technology, in order to obtain an image that is highly sensitive to unevenness, the angle of the light incidence direction relative to the surface of the sheet must be shallow (small), which results in an image that is dark overall and the shadows caused by the unevenness are easily buried in noise.

[0006] An object of the present invention is to provide a sheet identification device, an image processing device, and a sheet identification method that can easily improve the accuracy of identifying unevenness on the surface of a sheet. [Means for solving the problem]

[0007] A sheet specifying device according to one aspect of the present invention includes an acquisition unit and an unevenness specifying unit. The acquisition unit acquires a specific image that is an image of a specific region. The specific region is a region on a surface of a sheet on which an image is to be formed or read, onto which pattern light is projected. The unevenness specifying unit specifies unevenness information relating to unevenness on the surface of the sheet based on the specific image. Effect of the Invention

[0008] According to the present invention, it is possible to provide a sheet specifying device, an image processing device, and a sheet specifying method that can easily improve the accuracy of specifying unevenness on the surface of a sheet. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic block diagram of an image processing device according to the first embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing the external appearance and the internal configuration of the image processing device according to the first embodiment. [Diagram 3] FIG. 3 is a schematic diagram showing a light irradiating unit and an imaging unit of the sheet specifying device according to the first embodiment. [Figure 4] FIG. 4 is a schematic diagram showing a light irradiating unit and a sheet of the sheet specifying device according to the first embodiment. [Diagram 5] FIG. 5 is a schematic diagram showing the principle of detection of irregularities on the surface of a sheet in the sheet specifying device according to the first embodiment. [Figure 6] FIG. 6 is a diagram showing an example of a specified image obtained by the sheet specifying device according to the first embodiment. [Figure 7] FIG. 7 is a flowchart of an operation example of the sheet specifying device according to the first embodiment. [Figure 8] FIG. 8 is a diagram showing an example of a specified image obtained by the sheet specifying device according to the first embodiment when the specified angle is changed. [Figure 9] FIG. 9 is a graph showing the relationship between the standard deviation and the arithmetic mean height obtained by the sheet specifying device according to the first embodiment. [Figure 10] FIG. 10 is a table showing the results of calculating the coefficient of determination while changing the line width of the pattern light and the relationship between the irradiation direction of the pattern light and the fiber direction in the sheet specifying device according to the first embodiment. [Figure 11] FIG. 11 is a schematic diagram showing pattern light that generates a grid pattern in the sheet specifying device according to the first embodiment. [Figure 12] FIG. 12 is a schematic block diagram of an image processing device according to the second embodiment. [Figure 13] FIG. 13 is a schematic diagram showing a light irradiating unit and a sheet of a sheet specifying device according to the third embodiment. [Figure 14] FIG. 14 is a diagram showing an example of a specified image and an integrated image obtained by the sheet specifying device according to the third embodiment. [Figure 15] FIG. 15 is a diagram showing an example of a specified image and an integrated image obtained by the sheet specifying device according to the third embodiment. [Figure 16] FIG. 16 is a graph showing pixel values ​​of each pixel in one row of an integrated image obtained by the sheet specifying device according to the third embodiment. [Figure 17] FIG. 17 is a graph showing the relationship between the width and the arithmetic mean height of the intermediate layer obtained by the sheet specifying device according to the third embodiment. [Figure 18] FIG. 18 is a flowchart of an operation example of the sheet specifying device according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The following embodiment is an example of the present invention, and is not intended to limit the technical scope of the present invention.

[0011] (Embodiment 1) [1] Overall configuration of image processing device First, the overall configuration of an image processing device 10 according to this embodiment will be described with reference to FIGS.

[0012] The image processing device 10 according to the present embodiment is, for example, a multifunction device having multiple functions such as a scanning function for reading an image (image data) from an original, a printing function for forming an image based on image data, a facsimile function, and a copy function. The image processing device 10 only needs to have an image processing function including at least one of a function for forming an image and a function for reading an image, and may be a printer, a scanner, a facsimile machine, a copy machine, or the like.

[0013] As shown in Fig. 1, the image processing device 10 includes an automatic document feeder 11, an image reading unit 12, an image forming unit 13, a paper feeder 14, an operation display unit 15, and a control unit 16. The automatic document feeder 11 is an ADF (Auto Document Feeder), and is therefore indicated as "ADF" in Fig. 1, and will also be referred to as "ADF 11" in the following description. In this embodiment, as shown in Fig. 2, the image processing device 10 includes a housing 100. The ADF 11, the image reading unit 12, the image forming unit 13, the paper feeder 14, the operation display unit 15, and the control unit 16 are provided in the housing 100.

[0014] The ADF 11 conveys a sheet (original) whose image is to be read by the image reading unit 12. The ADF 11 includes an original setting unit, a plurality of conveying rollers, an original pressing unit, a paper ejection unit, and the like.

[0015] The image reading unit 12 reads an image from a sheet and outputs image data corresponding to the read image. The image reading unit 12 includes a document table, a light source, a plurality of mirrors, an optical lens, a CCD (Charge Coupled Device), and the like.

[0016] The image forming unit 13 forms an image on a sheet Sh1 (see FIG. 2) based on image data output from the image reading unit 12. The image forming unit 13 also forms an image on the sheet Sh1 based on image data input from an information processing device external to the image processing device 10, such as a personal computer. As an example, in the present embodiment, as shown in FIG. 2, the image forming unit 13 includes a transfer device 131, a fixing device 132, and a paper discharge tray 133, and forms an image on the sheet Sh1 by an electrophotographic method. The image forming unit 13 is not limited to a configuration for forming a monochrome image, and may be a configuration for forming a full-color image using four colors, C (cyan), M (magenta), Y (yellow), and K (black). The image forming unit 13 may also be a configuration for forming an image on a sheet by an image forming method other than the electrophotographic method, such as an inkjet method.

[0017] The image forming unit 13 forms an image on the sheet Sh1 using toner as a developer. Specifically, the image forming unit 13 forms an electrostatic latent image by irradiating a laser beam onto the surface of a charged photosensitive drum, and develops the electrostatic latent image with toner to form a toner image on the surface of the photosensitive drum. The transfer device 131 transfers the toner image onto the sheet Sh1 conveyed along the conveying path T1 (see FIG. 2). The fixing device 132 melts and fixes the toner image transferred onto the sheet Sh1 to the sheet Sh1. For example, the fixing device 132 includes a fixing roller and a pressure roller, and heats the toner image transferred onto the sheet Sh1 and presses the sheet Sh1 to fix the toner image onto the sheet Sh1. The sheet Sh1 after the image formation is discharged to the paper discharge tray 133. When the image forming unit 13 forms an image by an inkjet method, ink (another example of a developer) is supplied instead of toner.

[0018] The paper feed unit 14 supplies a sheet Sh1 to the image forming unit 13. The paper feed unit 14 has a plurality of paper feed cassettes 141, a manual feed tray, a plurality of transport rollers, etc. The paper feed unit 14 transports the sheet Sh1 from the plurality of paper feed cassettes 141 or the manual feed tray, etc., through a transport path T1 using a plurality of transport rollers, etc., and supplies the sheet Sh1 to the image forming unit 13. The image forming unit 13 forms an image on the sheet Sh1 supplied from the paper feed unit 14 through the transport path T1.

[0019] The operation display unit 15 is a user interface in the image processing device 10. The operation display unit 15 has a display unit such as a liquid crystal display that displays various information in response to control instructions from the control unit 16, and an operation unit such as a switch or a touch panel that inputs various information to the control unit 16 in response to user operations. Furthermore, the image processing device 10 may include, for example, an audio output unit and an audio input unit, in addition to or instead of the operation display unit 15, as a user interface.

[0020] The control unit 16 controls the image processing device 10 in an integrated manner. The control unit 16 is mainly configured as a computer system having one or more processors and one or more memories. In the image processing device 10, the function of the control unit 16 is realized by the one or more processors executing a program. The program may be pre-recorded in one or more memories, may be provided through a telecommunication line such as the Internet, or may be recorded and provided in a non-transitory recording medium readable by a computer system such as a memory card or an optical disk. The one or more processors are composed of one or more electronic circuits including a semiconductor integrated circuit. Furthermore, the computer system referred to in this disclosure includes a microcontroller having one or more processors and one or more memories. The control unit 16 may be a control unit provided separately from a main control unit that controls the image processing device 10 in an integrated manner.

[0021] The image processing device 10 further includes a storage unit, a communication unit, a power supply unit, etc. The storage unit includes one or more non-volatile memories, and stores information such as control programs for causing the control unit 16 to execute various processes in advance. The communication unit is an interface that executes data communication between the image processing device 10 and an external device connected via a communication network such as the Internet or a LAN (Local Area Network). The power supply unit is a power supply circuit that generates (outputs) power for the operation of the image processing device 10.

[0022] Incidentally, a technology related to this type of image processing device 10 is known that is used in image forming devices such as copiers and laser printers, and that automatically identifies the type of sheet (paper) from an image of the surface. The image reading device according to the related technology includes a light emitting element that irradiates light onto the surface of the sheet from an oblique direction, and an area sensor that reads the illuminated area as an image, and reads information about the sheet from the reading result.

[0023] This image reading device estimates the surface roughness of a sheet by detecting the shadow image caused by the unevenness of the sheet surface from the image in the illuminated area. When the sheet surface has large unevenness, the contrast is higher than when the unevenness is small, so the magnitude of the surface unevenness can be estimated from the contrast. Furthermore, this image reading device maintains the sheet fiber direction and the light incident direction at approximately 45 degrees by setting the incident direction of the light from the light emitting element at an angle of 45 degrees to the sheet transport direction, resulting in a configuration with little variation in detection accuracy due to the fiber direction.

[0024] However, in the configuration of the above-mentioned related technology, in order to obtain an image that is highly sensitive to unevenness, the angle of the light incidence direction relative to the surface of the sheet must be shallow (small), which results in an image that is dark overall and the shadows caused by the unevenness are easily buried in noise.

[0025] In contrast, in this embodiment, an image processing device 10 is realized that can easily improve the accuracy of identifying unevenness on the surface of a sheet by using the configuration described below.

[0026] 1, an image processing apparatus 10 according to this embodiment includes a sheet specifying device 2. The sheet specifying device 2 according to this embodiment is integrated with the image processing apparatus 10.

[0027] The sheet identification device 2 includes an acquisition unit 21 and an unevenness identification unit 22. The acquisition unit 21 acquires a specific image Im1 (see FIG. 4). The specific image Im1 is an image of a specific region R1 (see FIG. 4) of a surface A1 (see FIG. 3) of a sheet Sh1 on which an image is to be formed or read. The specific region R1 is a region on the surface A1 of the sheet Sh1 onto which a pattern light P1 (see FIG. 3) is projected. The unevenness identification unit 22 identifies unevenness information relating to unevenness on the surface A1 of the sheet Sh1 based on the specific image Im1. In this embodiment, the acquisition unit 21 and the unevenness identification unit 22, which are components of the sheet identification device 2, are provided in the control unit 16 as one function of the control unit 16.

[0028] According to the above-mentioned configuration, the sheet identification device 2 according to the present embodiment and the image processing device 10 including the sheet identification device 2 have an advantage that it is easy to improve the identification accuracy of the unevenness of the surface A1 of the sheet Sh1. That is, the pattern light P1 is projected onto the specific region R1 of the surface A1 of the sheet Sh1, instead of uniformly irradiating the light from the light emitting element. Therefore, the unevenness identification unit 22 can identify unevenness information related to the unevenness of the surface A1 of the sheet Sh1 from the degree of deformation or distortion of the pattern light P1 in the specific image Im1. Therefore, even if the angle of the light incident direction with respect to the surface A1 of the sheet Sh1 is not made shallow (small) as in the related technology, it is possible to identify unevenness information even from a relatively bright specific image Im1, and as a result, it is easier to improve the identification accuracy of the unevenness compared to the related technology.

[0029] The sheet identification device 2 according to this embodiment, together with an image processing unit (an image reading unit 12 and an image forming unit 13), constitutes an image processing device 10. In other words, the image processing device 10 according to this embodiment includes the sheet identification device 2 and an image processing unit that performs at least one of image formation and image reading for a sheet Sh1.

[0030] [2] Definition The term "sheet" in the present disclosure refers to a sheet on which an image is to be formed or read. In the present embodiment, as an example, the sheet Sh1 to be irradiated with the patterned light P1 is the sheet Sh1 on which an image is to be formed by the image forming unit 13. That is, in the present embodiment, the sheet Sh1 conveyed on the conveying path T1 by the paper feed unit 14 is the sheet to be irradiated with the patterned light P1. However, without being limited to this example, the sheet to be irradiated with the patterned light P1 may be a sheet (original) on which an image is to be read by the image reading unit 12, that is, a sheet conveyed by the ADF 11. In addition, the sheet Sh1 is paper as an example in the present embodiment, but is not limited to paper and may be, for example, a resin film or the like.

[0031] The "pattern light" in the present disclosure is, for example, light projected from the light projection unit 3 (see FIG. 1) onto a projection surface (here, the surface A1 of the sheet Sh1) with its shape and direction controlled, and is so-called structured light. That is, in an area (specific area R1) irradiated with the pattern light P1, the area is not uniformly illuminated by the pattern light P1, but figures, designs, pictures, patterns, symbols, letters, numbers, etc. corresponding to the pattern light P1 are projected. Specifically, by irradiating the specific area R1 with the pattern light P1, a luminance distribution of a pattern corresponding to the pattern light P1, such as a stripe pattern, a lattice pattern, or an arc pattern, is generated in the specific area R1. Furthermore, the pattern light P1 is not limited to a fixed pattern such as a still image, and may generate a luminance distribution of a pattern that changes over time such as a moving image (including animation) in the specific area R1.

[0032] The "specific image" in the present disclosure is, for example, an image of the specific region R1 in a state where the pattern light P1 is projected, captured by the imaging unit 4. That is, the specific image Im1 includes the pattern light P1 projected onto the specific region R1, more precisely, the luminance distribution of a pattern according to the pattern light P1 that is generated in the specific region R1 by projecting the pattern light P1. The specific image Im1 may be either a monochrome image or a color image, and may further be either a still image or a moving image.

[0033] The "irregularity information" in the present disclosure refers to information on the irregularities of the surface A1 of the sheet Sh1, and includes, for example, information on the height (or depth) of the irregularities and / or the size of the irregularities in a planar view. The surface A1 of the sheet Sh1 has irregularities including at least one of recesses and protrusions. That is, the surface A1 may include only a plurality of recesses or only a plurality of protrusions. Furthermore, the surface A1 may include a plurality of recesses and one protrusion. In this case, as an example, the surface A1 may include one net-like protrusion and a plurality of recesses consisting of the mesh parts surrounded by this protrusion. Similarly, as an example, the surface A1 may include one net-like recess and a plurality of protrusions consisting of the mesh parts surrounded by this recess.

[0034] The unevenness (concave and convex portions) on the surface A1 are so small that they cannot be individually identified by the naked eye, and the surface A1 of one sheet Sh1 contains many unevennesses. In other words, the unevenness is finer than the entire surface A1, and when a person looks at the surface A1, the unevenness makes the surface A1 look rough and "matte". Such many fine unevennesses are formed, for example, by the many fibers that make up the paper in the case of a paper sheet Sh1, or by embossing or the like in the case of a resin film. Information on such fine unevenness includes an index representing surface roughness, such as the arithmetic mean height (Sa) or the arithmetic mean height of lines (Ra).

[0035] The "fiber direction" in this disclosure refers to the direction of the fibers on the surface A1 of the sheet Sh1, and for example, in the case of a paper sheet Sh1, it is the extension direction of the numerous fibers that make up the paper, that is, the direction of the grain of the paper. Generally, the sheet Sh1 has a "vertical grain" in which the fiber direction is along the long side of the sheet Sh1, and a "cross grain" in which the fiber direction is along the short side of the sheet Sh1. The conveying direction D1 of the sheet Sh1 in the image processing device 10 (see FIG. 2) is the direction along the long side or short side of the sheet Sh1. Therefore, basically, the fiber direction is along the conveying direction D1 of the sheet Sh1 or along a direction perpendicular to the conveying direction D1.

[0036] [3] Seat identification device Next, the configuration of the sheet specifying device 2 according to this embodiment will be described in more detail with reference to FIGS.

[0037] In this embodiment, the sheet specifying device 2 includes an acquisition unit 21, an unevenness specifying unit 22, a condition determining unit 23, a direction specifying unit 24, a thickness specifying unit 25, a light irradiating unit 3, an imaging unit 4, and a thickness sensor 5. The acquisition unit 21, the unevenness specifying unit 22, the condition determining unit 23, the direction specifying unit 24, and the thickness specifying unit 25 are provided in the control unit 16 as functions of the control unit 16. That is, in this embodiment, the image processing device 10 includes, in addition to the acquisition unit 21 and the unevenness specifying unit 22, the condition determining unit 23, the direction specifying unit 24, and the thickness specifying unit 25 as functions of the control unit 16.

[0038] The light irradiation unit 3 irradiates the pattern light P1 toward the surface A1 of the sheet Sh1. That is, the light irradiation unit 3 generates the pattern light P1 whose shape and direction are controlled, and projects the pattern light P1 onto the surface A1 of the sheet Sh1 in a specific region R1 on the surface A1 of the sheet Sh1. The pattern light P1 from the light irradiation unit 3 projects figures, designs, pictures, patterns, symbols, letters, numbers, etc. according to the pattern light P1 onto the specific region R1 on the surface A1 of the sheet Sh1.

[0039] In the present embodiment, as an example, the pattern light P1 forms a stripe pattern in which light portions L1 and dark portions L2 are alternately arranged on the specific region R1 as shown in FIG. 4. That is, by projecting the pattern light P1, a luminance distribution of a stripe pattern including light portions L1 and dark portions L2 is generated in the specific region R1. Here, the light portions L1 are brighter than the dark portions L2. In other words, the stripe pattern is a pattern in which a plurality of light portions L1 are arranged at intervals, or a pattern in which a plurality of dark portions L2 are arranged at intervals. That is, by projecting the pattern light P1 in the specific region R1, a stripe pattern is formed in which linear light portions L1 and linear dark portions L2 are alternately arranged in a direction perpendicular to each longitudinal direction. In the present embodiment, as an example, linear light portions L1 and dark portions L2 perpendicular to the conveying direction D1 of the sheet Sh1 are arranged so as to be alternately arranged in the conveying direction D1. In FIG. 4 and the like, the light portions L1 are indicated by shading (dot hatching), and the dark portions L2 are indicated by blackening. As a result, the stripe pattern on the specific region R1 is more likely to show deformation or distortion according to the unevenness of the surface A1. However, the pattern light P1 that produces the stripe pattern shown in Fig. 4 is merely one example of the pattern light P1, and the pattern light P1 can be changed as appropriate.

[0040] In this embodiment, as shown in FIG. 3 and FIG. 4, the light irradiation unit 3 has a light source 31 and a shielding body 32. The shielding body 32 transmits the pattern light P1 by blocking a part of the light output from the light source 31. The light source 31 includes a light-emitting element that emits light when power is supplied, and outputs the light generated by the light-emitting element toward the shielding body 32. The light source 31 is controlled by a control signal from the control unit 16, and can be switched on and off at least by the control unit 16. The shielding body 32 is a component that is disposed between the light source 31 and a specific region R1 on the surface A1 of the sheet Sh1, and blocks a part of the light from the light source 31 and transmits the rest. As a result, a part of the light output from the light source 31 is blocked by the shielding body 32, and the rest transmits through the shielding body 32, so that the light that transmits through the shielding body 32 becomes the pattern light P1 controlled to a desired shape by the shielding body 32. As a result, the pattern light P1 can be realized with a relatively simple configuration.

[0041] In the present embodiment, as an example, the light source 31 has one or more light-emitting elements such as light-emitting diodes (LEDs) or organic electroluminescence (EL), and emits light substantially uniformly over the entire area of ​​a light-emitting surface 311 (see FIG. 3) that is rectangular in plan view, thereby emitting light from the surface. Furthermore, in the present embodiment, the light source 31 outputs parallel light or light close to parallel light. Therefore, the optical axis Ax1 (see FIG. 3) of the pattern light P1 output from the light irradiation unit 3 is a perpendicular line to the light-emitting surface 311 that passes through the center (center of gravity) of the light-emitting surface 311 of the light source 31. The light source 31 may have an optical component, such as a collimator lens, that converts light from the light-emitting element into parallel light. In the present embodiment, as an example, the light source 31 outputs visible light, specifically white light. However, the light source 31 may output light of a wavelength to which the imaging unit 4 is sensitive, and may output light other than white light, or may output light of a wavelength range other than visible light, such as infrared light or ultraviolet light.

[0042] In the present embodiment, as an example, the shield 32 is a rectangular plate-shaped component that absorbs or reflects light from the light source 31, and has one or more slits 321 (see FIG. 4 ). As a result, a part of the light output from the light source 31 is shielded by the shield 32, and the rest passes through the shield 32 through the slits 321 of the shield 32. In the present embodiment, the shield 32 has a plurality of linear slits 321 to realize the pattern light P1 that forms a stripe pattern in the specific region R1. As a result, in the specific region R1 irradiated with the pattern light P1, the light that has passed through the slits 321 becomes the bright portion L1, and the shadow of the shield 32 becomes the dark portion L2, thereby projecting the stripe pattern. However, the present embodiment is not limited to the configuration in which the light that has passed through the slits 321 becomes the bright portion L1, and the pattern light P1 may be realized by, for example, "interference fringes" that utilize the interference of light.

[0043] Here, a first virtual straight line connecting the light irradiation unit 3 that irradiates the pattern light P1 and the center of the specific region R1 is inclined at a predetermined angle θ1 with respect to a second virtual straight line along the conveying direction D1 of the sheet Sh1. In this embodiment, since the surface A1 of the sheet Sh1 is along the conveying direction D1 of the sheet Sh1 in the specific region R1, the angle between the first virtual straight line and the surface A1 of the sheet Sh1 is the predetermined angle θ1. Furthermore, since the first virtual straight line is the optical axis Ax1 of the pattern light P1, the optical axis Ax1 of the pattern light P1 is inclined at a predetermined angle θ1 with respect to the surface A1 of the sheet Sh1. In particular, in this embodiment, the light irradiation unit 3 is configured to irradiate the pattern light P1 obliquely at a predetermined angle θ1 with respect to the specific region R1 from the downstream side in the conveying direction D1, that is, from the front side in the traveling direction of the sheet Sh1. As a result, deformation or distortion according to the unevenness of the surface A1 is likely to appear in the pattern on the specific region R1.

[0044] The imaging unit 4 captures an image of the specific region R1 of the surface A1 of the sheet Sh1 as a specific image Im1. Here, since the imaging unit 4 captures an image of the specific region R1 in a state where the pattern light P1 is projected (specific image Im1), the light irradiation unit 3 irradiates the specific region R1 with the pattern light P1 at least during the imaging timing of the imaging unit 4. In the present embodiment, as an example, the imaging unit 4 and the light irradiation unit 3 are synchronized, and the light irradiation unit 3 irradiates the pattern light P1 in accordance with the imaging timing of the imaging unit 4. In other words, during a period when the imaging unit 4 does not perform imaging, the light irradiation unit 3 does not output the pattern light P1, thereby suppressing unnecessary power consumption in the light irradiation unit 3.

[0045] In this embodiment, as shown in Fig. 3, the imaging unit 4 has an imaging element 41 and an optical component 42. The imaging element 41 includes an area sensor or a line sensor, and outputs image data of the captured specific image Im1 as an electrical signal to the control unit 16. In this embodiment, as an example, the imaging unit 4 is a CIS (Contact Image Sensor) type area sensor using a CMOS (Complementary Metal Oxide Semiconductor) sensor as the imaging element 41. However, the imaging unit 4 is not limited to this example, and may be, for example, a CCD type using a CCD (Charge Coupled Device) as the imaging element 41.

[0046] The optical component 42 includes, for example, an imaging lens, and is disposed between the imaging element 41 and the specific region R1 on the surface A1 of the sheet Sh1. As a result, light from the specific region R1 is incident on the imaging element 41 through the optical component 42. In this embodiment, the imaging element 41 and the optical component 42 are arranged on a perpendicular line to the specific region R1 passing through the center (center of gravity) of the specific region R1. Furthermore, the light receiving surface 411 (see FIG. 3) of the imaging element 41 is disposed parallel to the specific region R1. Therefore, the optical axis Ax2 (see FIG. 3) of the imaging unit 4 is a perpendicular line to the light receiving surface 411 passing through the center (center of gravity) of the light receiving surface 411 of the imaging element 41. The optical axis Ax2 of the imaging unit 4 is also perpendicular to the specific region R1, and intersects with the optical axis Ax1 of the light irradiation unit 3 (pattern light P1) at the center of the specific region R1. The area of ​​the specific region R1 imaged by the image sensor 41 is equal to the area of ​​the light receiving surface 411 of the image sensor 41 divided by the image magnification M of the optical component 42. In this embodiment, for ease of explanation, it is assumed that the image magnification M is "1." However, the image magnification M may be a value other than 1.

[0047] In the present embodiment, as an example, the imaging section 4 is integrated with the light irradiation section 3 to form a sensor unit 20 (see FIG. 2). In other words, the sensor unit 20 includes the light irradiation section 3 and the imaging section 4. The sensor unit 20 is housed in a housing 100 of the image processing device 10, and is electrically connected to at least the control section 16.

[0048] In this embodiment, as shown in FIG. 2, the sensor unit 20 including the light irradiation unit 3 and the imaging unit 4 is disposed facing the transport path T1 between the paper feed unit 14 and the image forming unit 13. Therefore, the imaging position of the specific region R1 is set on the transport path T1 between the paper feed unit 14 and the image forming unit 13. In other words, the light irradiation unit 3 and the imaging unit 4 can irradiate the pattern light P1 to the sheet Sh1 transported from the paper feed unit 14 to the image forming unit 13 at a position between the paper feed unit 14 and the image forming unit 13 to capture the specific image Im1. More specifically, the sensor unit 20 is disposed at a position upstream of the transfer device 131 of the image forming unit 13 and downstream of the junction of the transport paths T1 connected to the multiple paper feed cassettes 141 in the transport direction D1 of the sheet Sh1. Therefore, for the sheets Sh1 supplied to the image forming unit 13 from a plurality of paper feed cassettes 141, a specific image Im1 can be captured by one sensor unit 20, and it is not necessary to provide a sensor unit 20 for each paper feed cassette 141.

[0049] In the present embodiment, the surface A1 of the sheet Sh1 including the specific region R1 is, as an example, one side of the sheet Sh1 on which an image is formed by the image forming unit 13 in the thickness direction, but is not limited to this example. The specific region R1 may be set, for example, on one side (rear side) of the sheet Sh1 on which an image is not formed by the image forming unit 13 in the thickness direction. In this case, the light irradiation unit 3 and the imaging unit 4 are disposed on the rear side of the sheet Sh1. Also, the specific region R1 may be set, for example, on both sides of the sheet Sh1 in the thickness direction. In this case, two sets of the light irradiation unit 3 and the imaging unit 4 may be provided and disposed on both sides of the sheet Sh1 in the thickness direction, or the sheet Sh1 may be turned over to image the specific image Im1 on both sides of the sheet Sh1 with one set of the light irradiation unit 3 and the imaging unit 4.

[0050] The thickness sensor 5 detects a physical quantity related to the thickness of the sheet Sh1. The thickness sensor 5 outputs the detected physical quantity to the control unit 16 as an electric signal. This allows the control unit 16 to specify the thickness of the sheet Sh1. As an example, the thickness sensor 5 includes an optical sensor that detects the thickness (or basis weight) of the sheet Sh1 by using transmitted light. The thickness sensor 5 may be included in the sensor unit 20, or may be provided separately from the sensor unit 20.

[0051] The acquisition unit 21 acquires the specific image Im1 captured by the imaging unit 4. Specifically, the acquisition unit 21 acquires image data of the specific image Im1 captured by the imaging unit 4 from the imaging element 41 of the imaging unit 4 as an electrical signal. The acquisition unit 21 controls the light irradiation unit 3 and the imaging unit 4, and causes the light irradiation unit 3 to irradiate the pattern light P1 and the imaging unit 4 to capture the specific image Im1, for example, in accordance with the timing when the sheet Sh1 passes through a position on the transport path T1 corresponding to the sensor unit 20. The specific image Im1 acquired by the acquisition unit 21 is temporarily stored in one or more memories. The acquisition unit 21 may acquire the specific image Im1 from a source other than the imaging unit 4.

[0052] The unevenness specifying unit 22 specifies unevenness information on unevenness of the surface A1 of the sheet Sh1 based on the specified image Im1 acquired by the acquiring unit 21. This makes it possible to specify the unevenness state of the surface A1 of the sheet Sh1. The unevenness information includes information on at least one of the dimension of the unevenness of the surface A1 in a direction perpendicular to the plane along the surface A1 and the dimension in a direction along the plane. In other words, the unevenness information includes information on the height (or depth) of the unevenness, which is the dimension in a direction perpendicular to the plane along the surface A1, and / or the size of the unevenness in a planar view, which is the dimension in a direction along the plane. This makes it possible to specify the height (or depth) of the unevenness of the surface A1 of the sheet Sh1 and / or the size of the unevenness in a planar view. In this embodiment, as an example, the unevenness specifying unit 22 calculates a numerical value equivalent to the arithmetic mean height (Sa) of the surface A1 regarding the height (or depth) of the unevenness as the unevenness information.

[0053] Here, the unevenness specifying unit 22 specifies unevenness information based on the degree of deformation or distortion of the pattern light P1 in the specific image Im1. That is, since the specific image Im1 includes a luminance distribution of a pattern (a stripe pattern in this embodiment) corresponding to the pattern light P1, which is generated in the specific region R1 by projecting the pattern light P1, the unevenness of the surface A1 causes deformation or distortion of the pattern. For example, even if the pattern light P1 forms a linear pattern, deformation (wandering) corresponding to the unevenness of the surface A1 occurs in the pattern light P1 projected on the surface A1. Therefore, the unevenness specifying unit 22 calculates unevenness information related to the unevenness of the surface A1 from the degree of deformation or distortion of the pattern light P1. In this embodiment, the unevenness specifying unit 22 specifies unevenness information based on at least the variation in the line width of the pattern light P1 on the specific region R1. This makes it possible to specify the uneven state of the surface A1 of the sheet Sh1 by a relatively simple calculation process.

[0054] The condition determination unit 23 determines image processing conditions based on the unevenness information identified by the unevenness identification unit 22. The image processing conditions here are conditions related to image formation or image reading. In other words, various image processing conditions including image formation conditions related to image formation executed by the image processing device 10 and / or image reading conditions related to image reading are determined by the condition determination unit 23. Specifically, the image processing conditions include, for example, the fixing pressure, fixing temperature, conveying speed of the sheet Sh1, transfer voltage, or ink ejection amount in the inkjet method in the image forming unit 13, and further, the conveying speed, light amount, or resolution of the sheet in the image reading unit 12. For example, if the arithmetic mean height (Sa) of the surface A1 of the sheet Sh1 becomes large (i.e., rough), heat may not be easily transmitted during fixing by the image forming unit 13, or electrical contact resistance may increase during transfer, making it difficult for current to flow. Therefore, the condition determination unit 23 automatically sets image processing conditions based on the unevenness information so that when the arithmetic mean height (Sa) becomes large (i.e., rough), the fixing temperature is increased, the conveying speed is decreased, the transfer voltage is increased, etc. This makes it possible to form and / or read images under appropriate image processing conditions according to the unevenness of the front surface A1 of the sheet Sh1, leading to an improvement in the quality (including image quality) of the image formation and / or image reading.

[0055] In addition, in this embodiment, the condition determination unit 23 determines the image processing conditions for forming or reading an image based on the fiber direction. That is, in this embodiment, the fiber direction of the surface A1 of the sheet Sh1 is specified by the direction specification unit 24. Therefore, the condition determination unit 23 determines the image processing conditions based not only on the unevenness information but also on the fiber direction. For example, in the inkjet type image forming unit 13, since the curl behavior differs depending on the fiber direction, the curl direction may be predicted according to the fiber direction and the curl may be corrected. The image processing conditions determined by the condition determination unit 23 based on the fiber direction include the curl correction conditions. In addition, since it is possible to estimate "skew" in which the long side or short side of the sheet Sh1 is inclined with respect to the conveying direction from the fiber direction, the image processing conditions determined by the condition determination unit 23 based on the fiber direction may include the skew correction conditions. This makes it possible to form and / or read an image under appropriate image processing conditions according to the fiber direction of the surface A1 of the sheet Sh1, leading to improvement in the quality (including image quality) of the image formation and / or image reading.

[0056] However, the condition determination unit 23 only needs to have a function of determining image processing conditions based on at least one of the unevenness information and the fiber direction. In other words, the condition determination unit 23 is not limited to a configuration in which the image processing conditions are determined based on both the unevenness information and the fiber direction, and may determine image processing conditions based on only either the unevenness information or the fiber direction. Furthermore, in this embodiment, the thickness determination unit 25 specifies the thickness of the sheet Sh1. Therefore, the condition determination unit 23 may determine image processing conditions based on the thickness of the sheet Sh1 in addition to or instead of at least one of the unevenness information and the fiber direction.

[0057] The direction specifying unit 24 specifies the fiber direction of the surface A1 of the sheet Sh1 based on the specific image Im1. Here, the direction specifying unit 24 specifies the fiber direction based on the deformation or distortion of the pattern light P1 in the specific image Im1. That is, depending on the line width of the pattern light P1 on the specific region R1, the degree of deformation or distortion of the unevenness of the surface A1 caused by the pattern light P1 varies depending on the relationship between the extension direction of the pattern light P1 and the fiber direction. Therefore, in this embodiment, the direction specifying unit 24 specifies the fiber direction based on at least the variation in the line width of the pattern light P1 on the specific region R1. This makes it possible to specify the fiber direction of the surface A1 of the sheet Sh1 through a relatively simple calculation process.

[0058] The thickness specifying unit 25 specifies the thickness of the sheet Sh1 based on the output of the thickness sensor 5. That is, the thickness specifying unit 25 receives an electrical signal representing a physical quantity related to the thickness of the sheet Sh1 from the thickness sensor 5 and calculates the thickness of the sheet Sh1. The sheet specifying device 2 according to the present embodiment includes the thickness specifying unit 25, and thus can estimate the type (paper type) of the sheet Sh1, including the thickness, in addition to the state of the surface A1 of the sheet Sh1.

[0059] [4] Sheet identification method Next, a sheet identification method according to the present embodiment, that is, the operation of the sheet identification device 2 will be described with reference to FIGS.

[0060] [4.1] Principle First, the principle of how the unevenness identification unit 22 identifies unevenness information based on the specific image Im1 will be described with reference to Fig. 5 and Fig. 6. In Fig. 5, the bright part L1 of the pattern light P1 is typically indicated by a dotted line, and the dark part L2 is typically indicated by a two-dot chain line.

[0061] As shown in the upper part of FIG. 5 as "protrusion 1", it is assumed that a rectangular parallelepiped protrusion A11 having a height ΔZ from the surface A1 exists on the surface A1 of the sheet Sh1. Here, the pattern light P1 is obliquely incident on the surface A1 of the sheet Sh1 at a predetermined angle θ1. Therefore, the pattern light P1 is projected on the same plane as the surface A1 except for the protrusion A11, and is projected forward of the surface A1 by a height ΔZ at the protrusion A11, and when viewed from the perpendicular direction of the surface A1, the projection position of the pattern light P1 is shifted by the portion of the protrusion A11. In other words, in the specific image Im1 captured by the imaging unit 4, the pattern light P1 (light portion L1 and dark portion L2) in the portion where the protrusion A11 exists is shifted from the original projection position on the surface A1 by a shift amount ΔX expressed by the following formula 1. ΔX=ΔZ / tan θ1 (Equation 1)

[0062] Since the predetermined angle θ1 is known, if the shift amount ΔX is obtained from the specific image Im1, the height ΔZ of the convex portion A11 can be calculated from the shift amount ΔX and the above formula 1. Then, from the shift amount ΔX for the entire specific region R1, unevenness information for the entire specific region R1 can be obtained. The unevenness information calculated in this manner has a correlation with the arithmetic mean height (Sa) of the surface A1.

[0063] Also, as shown as "protrusion 2" in the lower part of Fig. 5, even if there is a triangular prism-shaped protrusion A12 on the surface A1 of the sheet Sh1, the height ΔZ from the surface A1 of which varies for each part, it is possible to calculate the height ΔZ of each part of the protrusion A12. That is, similar to the above example, by determining the shift amount ΔX from the specific image Im1, it is possible to calculate the height ΔZ of the protrusion A12 from the above formula 1. Therefore, for example, as in the case of a paper sheet Sh1, it is also possible to calculate unevenness information for unevenness caused by a wavy component that occurs when a large number of fibers are continuously entangled.

[0064] However, in the method of determining the roughness of the surface A1 from a shadow image caused by unevenness as in the above-mentioned related art, for example, in the case of a paper sheet Sh1, the calculation result strongly reflects the local fiber unevenness, so the calculation result does not necessarily have a linear relationship with the arithmetic mean height (Sa). Therefore, in the method of the above-mentioned related art, it is difficult to determine the magnitude of the surface roughness of a sheet Sh1 of the same type (for example, plain paper) from the calculation result, even if it is possible to distinguish between glossy paper (gloss paper) and plain paper, which have a high degree of flatness. Therefore, in order to determine the magnitude of surface roughness in the method of the above-mentioned related art, it is necessary to prepare in advance, for example, a table (database) that associates the calculation results and the arithmetic mean height (Sa) for various sheets Sh1.

[0065] In contrast, in the sheet specifying device 2 according to this embodiment, the line width of the pattern light P1, the predetermined angle θ1, etc. are optimized to reduce the influence of local fibers, and it becomes possible to calculate unevenness information having high linearity with the arithmetic mean height (Sa). Therefore, with the method of this embodiment, it is possible to uniquely determine the arithmetic mean height (Sa) from the calculation result of the unevenness specifying unit 22, even if a table (database) that associates the calculation result (unevenness information) with the arithmetic mean height (Sa) is not prepared in advance.

[0066] An example of a specified image Im1 obtained by the sheet specifying device 2 according to this embodiment is shown in Fig. 6. Here, the imaging conditions for the specified image Im1 are: a predetermined angle θ1 of 40 degrees, a resolution (number of pixels) of the imaging element 41 of 100x100, a line width W1 (see Fig. 4) of the light portion L1 of the stripe pattern formed by the pattern light P1 of 120 µm, and a line width W2 (see Fig. 4) of the dark portion L2 of 120 µm. Furthermore, the image magnification M is "1", and the irradiation direction of the pattern light P1, i.e., the arrangement direction of the light portion L1 and the dark portion L2, is the same as the fiber direction.

[0067] The specific image Im1 is composed of a plurality of pixels, each of which has a pixel value corresponding to the luminance. In the present embodiment, as an example, the relationship between the luminance and the pixel value is defined such that the pixel value increases as the luminance increases. Therefore, in the specific image Im1 obtained by capturing the specific region R1 onto which the pattern light P1 is projected, the pixel value of the pixel corresponding to the bright portion L1 is relatively large, and the pixel value of the pixel corresponding to the dark portion L2 is relatively small.

[0068] The upper part of FIG. 6 ("Sa: small") shows a specific image Im1 when a pattern light P1 is projected onto a specific region R1 of glossy paper (gloss paper) with a small arithmetic mean height (Sa), i.e., high flatness. On the other hand, the lower part of FIG. 6 ("Sa: large") shows a specific image Im1 when a pattern light P1 is projected onto a specific region R1 of plain paper (Sa=6 μm) with a large arithmetic mean height (Sa), i.e., low flatness. As shown in FIG. 6, the larger the arithmetic mean height (Sa), the greater the deformation and distortion of the stripe pattern caused by the pattern light P1 in the specific image Im1. Specifically, when the deformation and distortion of the stripe pattern becomes large, the boundary between the light portion L1 and the dark portion L2 of the stripe pattern becomes distorted, and the variation in the line width of each of the light portion L1 and the dark portion L2 becomes large. In other words, when the arithmetic mean height (Sa) increases, the undulation component of the height of the surface A1 increases, and the variation in the line width of each of the bright portion L1 and the dark portion L2 increases. Thus, in Fig. 6, it is clear that in the specific image Im1, the stripe pattern formed by the pattern light P1 is deformed or distorted depending on the unevenness of the surface A1.

[0069] [4.2] Specific processing Next, a specific process for identifying unevenness information based on the identified image Im1 by the unevenness identifying unit 22 will be described with reference to Fig. 7. Steps S1, S2, ... in the flowchart shown in Fig. 7 indicate the numbers of the processing procedures (steps) executed by the control unit 16. The process described below starts, for example, in synchronization with the timing when the sheet Sh1 passes through a position (monitor position) on the conveying path T1 corresponding to the sensor unit 20.

[0070] When the purpose of analysis of the specific image Im1 including the pattern light P1 is to restore a three-dimensional shape, it can be realized by, for example, a method of continuously projecting a plurality of pattern lights P1 and using a Fourier transform of the specific image Im1 to calculate the phase change of the pattern light P1. However, this method has a relatively high computation load, takes a relatively long time to calculate the roughness (unevenness information) of the surface A1, and also requires relatively high hardware (CPU, GPU, memory, etc.) costs. Therefore, in this embodiment, instead of the above method, the following method is adopted so that the roughness (unevenness information) of the surface A1 can be calculated by a relatively simple computation process.

[0071] That is, in this embodiment, the unevenness specification unit 22 calculates the width (line width) of at least one of the bright portion L1 and the dark portion L2 for each row (line) of the specific image Im1, with the arrangement direction of the bright portion L1 and the dark portion L2 in the specific image Im1 (left and right direction in FIG. 6) as the "row direction". That is, the specific image Im1 is an "N pixels x M rows" image in which N pixels are arranged in the arrangement direction of the bright portion L1 and the dark portion L2, and the unevenness specification unit 22 calculates the line width for each of the M rows included in the specific image Im1. The unevenness specification unit 22 obtains the line width of at least one of the bright portion L1 and the dark portion L2 calculated for each row in this way for the entire specific image Im1, and calculates the magnitude of the variation in the line width within the specific image Im1 as unevenness information. As a result, the unevenness specification unit 22 can obtain unevenness information that is correlated with the arithmetic mean height (Sa) of the surface A1 based on the variation in the line width of the pattern light P1.

[0072] <Step S1> Specifically, in step S1, the control unit 16 determines whether the sheet Sh1 reaches the monitor position, that is, a position on the transport path T1 corresponding to the sensor unit 20. When the sheet feeding unit 14 supplies the sheet Sh1 to the image forming unit 13, the control unit 16 determines that the sheet Sh1 reaches the monitor position (S1: Yes) if the sheet Sh1 is detected by a sensor at the monitor position, and shifts the process to step S2. On the other hand, if the sheet Sh1 is not detected by the sensor at the monitor position, the control unit 16 determines that the sheet Sh1 has not reached the monitor position (S1: No), and shifts the process to step S1.

[0073] <Steps S2 and S3> In step S2, the control unit 16 controls the light irradiation unit 3 by the acquisition unit 21 to cause the light irradiation unit 3 to irradiate the pattern light P1. As a result, the pattern light P1 is projected onto the specific region R1 on the front surface A1 of the sheet Sh1. In step S3, the control unit 16 controls the imaging unit 4 by the acquisition unit 21 to cause the imaging unit 4 to capture the specific region R1 on which the pattern light P1 is projected. As a result, a specific image Im1, which is an image of the specific region R1 on the front surface A1 of the sheet Sh1, is generated by the imaging unit 4.

[0074] <Step S4> In step S4, the control unit 16 causes the acquisition unit 21 to acquire an image of one row (one line) of the specific image Im1 from the imaging unit 4. That is, the acquisition unit 21 acquires one row of the specific image Im1, which corresponds to one pixel in the column direction. Since the imaging unit 4 (image sensor 41) is generally designed to read out an image sequentially row by row in this manner, by acquiring the specific image Im1 row by row and analyzing it (steps S5 and S6), the memory usage can be reduced.

[0075] <Step S5> In step S5, the control unit 16 executes preprocessing on the specific image Im1 in the acquisition unit 21. At this time, the specific image Im1 for one row (one line) acquired in step S4 is the subject of preprocessing. That is, the control unit 16 executes preprocessing on the specific image Im1 for each row. The preprocessing includes, for example, a filtering process and a binarization process. Specifically, the control unit 16 performs noise removal and the like on the specific image Im1 for one row by filtering process, and further binarizes it using a certain reference value.

[0076] The reference value used in the binarization process is, for example, the average value of multiple pixels or a predetermined value (predetermined value). Pixels corresponding to the light area L1 are pixels having a pixel value equal to or greater than the reference value and are therefore "white pixels", while pixels corresponding to the dark area L2 are pixels having a pixel value less than the reference value and are therefore "black pixels". The preprocessing may include a trimming process that cuts out only a portion of the specific image Im1, thereby narrowing down the range to be processed in step S6. Furthermore, filtering processes and the like are not essential and can be omitted as appropriate.

[0077] <Step S6> In step S6, the control unit 16 extracts width data indicating the width (line width) of at least one of the bright portion L1 and the dark portion L2 from the specific image Im1 using the unevenness identification unit 22. At this time, the target for extracting the width data is one row (one line) of the specific image Im1 acquired in step S4. That is, the control unit 16 executes extraction of the width data for the specific image Im1 on a row-by-row basis. Specifically, the control unit 16 calculates, as the width data, how many white pixels corresponding to the bright portion L1 and how many black pixels corresponding to the dark portion L2 are present in one row of the specific image Im1. At this time, the control unit 16 extracts the number of white pixels and the number of black pixels for the entire one row of the specific image Im1, thereby extracting the total line width of the multiple bright portions L1 and the total line width of the multiple dark portions L2.

[0078] In the present embodiment, as an example, both the number of white pixels corresponding to the line width of the light portion L1 and the number of black pixels corresponding to the line width of the dark portion L2 are used as the width data, but the present invention is not limited to this example, and only one of the pixel numbers may be used as the width data. That is, the control unit 16 may specify the unevenness information by focusing on the line width of either the light portion L1 or the dark portion L2. The control unit 16 may also extract the line width for each light portion L1 and each dark portion L2 by extracting the number of white pixels consecutive in the row direction and the number of black pixels consecutive in the row direction. In this case, the control unit 16 may use each line width of the multiple light portions L1 (or dark portions L2) as the width data, or may use a representative value (for example, an average value, a mode value, or a median value) of the line widths of the multiple light portions L1 (or dark portions L2) as the width data.

[0079] <Step S7> In step S7, the control unit 16 judges whether the processing has been completed up to the last row of the specific image Im1. That is, for the specific image Im1 of "N pixels x M rows", if the target of the processing is the Mth row, which is the last row, the control unit 16 judges that the processing has been completed up to the last row (S7: Yes) and shifts the processing to step S8. On the other hand, if the target of the processing is not the Mth row, which is the last row, the control unit 16 judges that the processing has not been completed up to the last row (S7: No), shifts the processing to step S4, and acquires the next row of the specific image Im1.

[0080] <Step S8> In step S8, the control unit 16 calculates the standard deviation σ of the width data for M rows of the specified image Im1 using the unevenness identification unit 22. When the arithmetic mean height (Sa) increases, the waviness component of the height of the surface A1 increases, so the variation in the line widths of the light and dark areas L1 and L2 increases (see FIG. 6), and the standard deviation σ increases. In other words, the unevenness identification unit 22 calculates the standard deviation σ as unevenness information.

[0081] <Step S9> In step S9, the control unit 16 determines image processing conditions in the condition determination unit 23. That is, the condition determination unit 23 determines image processing conditions including image formation conditions according to the standard deviation σ calculated in step S8. As an example, when the standard deviation σ becomes large, the condition determination unit 23 sets image formation conditions such as increasing the fixing temperature, decreasing the conveying speed, and increasing the transfer voltage. As a result, when an image is formed on the sheet Sh1 by the image forming unit 13, image formation conditions according to the unevenness of the surface A1 of the sheet Sh1 are automatically applied.

[0082] The procedure of the sheet identification method described above is merely an example, and the order of the processes shown in the flowchart of FIG. 7 may be changed as appropriate.

[0083] [5] Beam angle Next, the irradiation angle of the pattern light P1 will be described with reference to Fig. 8, which shows an example of a specific image Im1 when the predetermined angle θ1 is changed. In Fig. 8, the imaging conditions for the specific image Im1 are set as follows: the arithmetic mean height (Sa) of the specific region R1 is 6 μm, the resolution (number of pixels) of the imaging element 41 is 100×100, the line width W1 of the light portion L1 of the stripe pattern formed by the pattern light P1 is 100 μm, and the line width W2 of the dark portion L2 is 100 μm. Furthermore, the irradiation direction of the pattern light P1, that is, the arrangement direction of the light portion L1 and the dark portion L2 is set to be the same as the fiber direction.

[0084] The optical axis Ax1 of the pattern light P1 is inclined at a predetermined angle θ1 with respect to the surface A1 of the sheet Sh1 (see FIG. 3). Here, the predetermined angle θ1 greatly affects the brightness of the specific image Im1. In the method of obtaining the roughness of the surface A1 from a shadow image caused by unevenness as in the above-mentioned related art, the irradiation angle of light (corresponding to the predetermined angle θ1) with respect to the surface A1 of the sheet Sh1 is set relatively shallow (small) in order to capture unevenness of the order of several μm as a shadow image. In particular, in order to increase the sensitivity to unevenness, the irradiation angle is set to a very shallow angle of about 10 degrees. However, at a very small irradiation angle, not enough light reaches the imaging unit 4, and the specific image Im1 becomes a relatively dark image, and a relatively expensive, high-sensitivity imaging element 41 is required to obtain the roughness of the surface A1 from the dark image.

[0085] In contrast, in the sheet identification device 2 according to the present embodiment, the roughness of the surface A1 is obtained from the degree of deformation or distortion of the pattern light P1 in the specific image Im1, so it is sufficient if the pattern light P1 is deformed or distorted due to unevenness. Therefore, in the present embodiment, the predetermined angle θ1 can be set larger than in the method of the related art described above, and a bright image can be realized as the specific image Im1. Therefore, even if a relatively inexpensive imaging element 41 is used, the roughness of the surface A1 can be obtained from the specific image Im1.

[0086] On the contrary, in the configuration of this embodiment, as shown in FIG. 8, when the predetermined angle θ1 becomes small, the shape of the pattern light P1 projected on the specific region R1 becomes distorted, and the boundary between the light part L1 and the dark part L2 of the stripe pattern becomes unclear. That is, as is clear from FIG. 8, the shape of the pattern light P1 becomes more distorted when the predetermined angle θ1 is 30 degrees than when it is 40 degrees, and when the predetermined angle θ1 is 20 degrees, the shape of the pattern light P1 becomes even more distorted, and when the predetermined angle θ1 is 10 degrees, the shape of the pattern light P1 becomes even more distorted. From the specific image Im1 of the pattern light P1 whose shape is distorted in this way, it is difficult to extract deformation or distortion of the pattern light P1 due to unevenness. The inventors have verified various predetermined angles θ1 and have found that when a sheet Sh1 having an arithmetic mean height (Sa) of the surface A1 of about several μm is targeted, the predetermined angle θ1 is preferably 20 degrees or more.

[0087] In short, in consideration of the brightness of the specific image Im1, the predetermined angle θ1 is preferably 10 degrees or more, and more preferably 15 degrees or more. Furthermore, in this embodiment, the predetermined angle θ1 is set to 20 degrees or more so that the shape of the pattern light P1 is not too distorted. That is, the predetermined angle θ1 is 20 degrees or more and 90 degrees or less. Here, the lower limit of the predetermined angle θ1 is not limited to 20 degrees, and may be, for example, 25 degrees, 30 degrees, 35 degrees, 40 degrees, 45 degrees, 50 degrees, 55 degrees, 60 degrees, 65 degrees, 70 degrees, 75 degrees, or 80 degrees. In addition, the upper limit of the predetermined angle θ1 is not limited to 90 degrees, and may be, for example, 85 degrees, 80 degrees, 75 degrees, 70 degrees, 65 degrees, 60 degrees, 55 degrees, 50 degrees, or 45 degrees.

[0088] Since the difference between 90 degrees and the specified angle θ1 corresponds to the "incident angle" which is the angle with respect to the perpendicular line of the surface A1, when the specified angle θ1 is 20 degrees, the "incident angle" of the pattern light P1 is 70 degrees (=90 degrees-20 degrees). On the other hand, when the specified angle is 90 degrees, the incident angle of the pattern light P1 is 0 degrees.

[0089] [6] Line width Next, the line width of the pattern light P1 will be described with reference to Figs. 9 and 10. Fig. 9 is a graph showing the relationship between the standard deviation σ as unevenness information calculated according to the flowchart of Fig. 7 and the actual arithmetic mean height Sa for 48 types of sheets Sh1. In Fig. 9, the horizontal axis is the arithmetic mean height Sa, and the vertical axis is the standard deviation σ (the standard deviation σ is the average value of five points of the bright portion L1 or the dark portion L2). In Fig. 9, the imaging conditions for the specific image Im1 are that the resolution (number of pixels) of the imaging element 41 is 100 x 100, the line width W1 of the bright portion L1 of the stripe pattern by the pattern light P1 is 80 μm, and the line width W2 of the dark portion L2 is 80 μm. Furthermore, the irradiation direction of the pattern light P1, that is, the arrangement direction of the bright portion L1 and the dark portion L2 is the same as the fiber direction.

[0090] In the example of Figure 9, the coefficient of determination R 2 is "0.9684", and it can be confirmed that there is high linearity between the standard deviation σ and the arithmetic mean height Sa as unevenness information.

[0091] On the other hand, FIG. 10 shows the relationship between the line width of the pattern light P1 and the irradiation direction of the pattern light P1 and the fiber direction while changing the coefficient of determination R 2 10 shows the results of calculation. In Fig. 10, the imaging conditions for the specific image Im1 are a predetermined angle θ1 of 40 degrees and a resolution (number of pixels) of the imaging element 41 of 100 x 100. In addition, the line width W1 of the light portion L1 and the line width W2 of the dark portion L2 of the stripe pattern formed by the pattern light P1 are changed within a range of 40 µm to 200 µm, and the relationship between the irradiation direction of the pattern light P1 and the fiber direction is changed between "same" (i.e. parallel) and "90°" (i.e. perpendicular).

[0092] According to Fig. 10, it can be surmised that the influence of the relationship between the irradiation direction of the pattern light P1 and the fiber direction on the standard deviation σ as unevenness information varies depending on the line width of the pattern light P1. In other words, Fig. 10 confirms that the smaller (thinner) the line width of the pattern light P1 is, the greater the influence of the relationship between the irradiation direction of the pattern light P1 and the fiber direction on the standard deviation σ as unevenness information. This is believed to be due to the fact that the fiber width of the sheet Sh1 is several tens of µm or less, and the line width of the pattern light P1 approaches the fiber width, which makes it easier for the waviness component of the local height of the surface A1 to occur as a variation in the line width of each of the light portion L1 and the dark portion L2.

[0093] If the line width of the pattern light P1 is 100 μm or more, the coefficient of determination R 2 is 0.85 or more. Therefore, if the line width of the pattern light P1 is 100 μm or more, the influence of the relationship between the irradiation direction of the pattern light P1 and the fiber direction on the standard deviation σ as unevenness information is relatively small, and the relationship between the irradiation direction of the pattern light P1 and the fiber direction can be ignored. In short, whether the relationship between the irradiation direction of the pattern light P1 and the fiber direction affects the unevenness information is determined depending on whether the line width W1 of the light part L1 and the line width W2 of the dark part L2 of the stripe pattern by the pattern light P1 are 100 μm or more or less than 100 μm. In other words, if the line width is 100 μm or more, the relationship between the irradiation direction and the fiber direction is unlikely to affect the unevenness information, so the calculated unevenness information can be considered to be "independent of the fiber direction". On the other hand, if the line width is less than 100 μm, the relationship between the irradiation direction and the fiber direction is likely to affect the unevenness information, so the calculated unevenness information can be considered to be "dependent on the fiber direction".

[0094] As described above, even in the sheet specifying device 2 according to this embodiment, the relationship between the irradiation direction of the pattern light P1 and the fiber direction may affect the standard deviation σ as unevenness information, depending on the line width of the pattern light P1. By making the line width of the pattern light P1 relatively larger than the fiber width of the sheet Sh1, the effect can be reduced, and high linearity is achieved between the standard deviation σ as unevenness information and the arithmetic mean height Sa.

[0095] From the above, in this embodiment, the width of at least one of the bright portion L1 and the dark portion L2 is preferably 60 μm or more and 500 μm or less. Furthermore, in order to make the unevenness information less susceptible to the influence of the relationship between the irradiation direction of the pattern light P1 and the fiber direction, at least one of the line width W1 of the bright portion L1 and the line width W2 of the dark portion L2 of the stripe pattern by the pattern light P1 is preferably 100 μm or more. On the other hand, in order to make the unevenness information more susceptible to the influence of the relationship between the irradiation direction of the pattern light P1 and the fiber direction, at least one of the line width W1 of the bright portion L1 and the line width W2 of the dark portion L2 of the stripe pattern by the pattern light P1 is preferably less than 100 μm. Here, the lower limit of the width of at least one of the bright portion L1 and the dark portion L2 is not limited to 60 μm, and may be, for example, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, or 95 μm. Furthermore, the upper limit of the width of at least one of the bright and dark regions L1 and L2 is not limited to 500 μm, and may be, for example, 450 μm, 400 μm, 350 μm, 300 μm, 250 μm, 200 μm, 180 μm, 160 μm, 140 μm, or 120 μm.

[0096] [7] Lattice pattern Next, the pattern light P1 that produces a grid pattern will be described with reference to Fig. 11. That is, by projecting the pattern light P1 onto the specific region R1, a luminance distribution of a grid pattern including bright parts L1 and dark parts L2 is produced.

[0097] A grid pattern is a superposition of a vertical stripe pattern and a horizontal stripe pattern that are orthogonal to each other. Therefore, as shown in Fig. 11, the pattern light P1 that generates the grid pattern can be considered as a composite light of a first pattern light P11 that generates a first stripe pattern (vertical stripe pattern) and a second pattern light P12 that generates a second stripe pattern (horizontal stripe pattern). In the example of Fig. 11, in the area where the light portion L1 and the dark portion L2 of the first pattern light P11 and the second pattern light P12 overlap, the dark portion L2 is prioritized, but this is not limited thereto, and the light portion L1 may be prioritized. In other words, the light portion L1 (shaded) and the dark portion L2 (blackened) of the grid pattern shown in Fig. 11 may be reversed.

[0098] Here, the line width of the first pattern light P11 and the line width of the second pattern light P12 are different from each other. That is, the line widths of the vertical stripes and the horizontal stripes of the lattice pattern are different. In the example of FIG. 11, the line width W11 of the bright portion L1 and the line width W12 of the dark portion L2 of the first pattern light P11 are larger than the line width W21 of the bright portion L1 and the line width W22 of the dark portion L2 of the second pattern light P12. Specifically, the line width W11 of the bright portion L1 and the line width W12 of the dark portion L2 of the first pattern light P11 are both 100 μm, and the line width W21 of the bright portion L1 and the line width W22 of the dark portion L2 of the second pattern light P12 are both 80 μm. Therefore, in the example of FIG. 11, the vertical stripe pattern of the lattice pattern is wider than the horizontal stripe pattern.

[0099] In short, the stripe pattern includes a first stripe pattern (vertical stripe pattern) and a second stripe pattern (horizontal stripe pattern) that are orthogonal to each other. The first stripe pattern and the second stripe pattern have different widths in at least one of the light portions L1 and the dark portions L2. This makes it possible to specify the fiber direction of the sheet Sh1 in addition to the unevenness information. In the example of FIG. 11, the first stripe pattern is wider than the second stripe pattern in both the light portions L1 and the dark portions L2, but this is not limited to this example, and the first stripe pattern may be wider than the second stripe pattern only in the light portions L1 or only in the dark portions L2. Also, the second stripe pattern may be wider than the first stripe pattern in at least one of the light portions L1 and the dark portions L2.

[0100] Furthermore, the pattern light P1 that produces the above-mentioned grid pattern may be realized by using a grid-shaped shield 32, or may be realized by using two shields 32 with slits 321 formed therein. In the latter case, by arranging two shields 32 with slits 321 of different widths on top of each other so that the orientations of the slits 321 are perpendicular to each other, it is possible to realize a grid pattern as shown in FIG.

[0101] When such a lattice pattern light P1 is used, the control unit 16 can analyze the line width of the second stripe pattern (horizontal stripe pattern) in addition to the line width of the first stripe pattern (vertical stripe pattern) when analyzing the specific image Im1. That is, the control unit 16 can calculate the variation in the line width in the horizontal direction from the first stripe pattern, and can calculate the variation in the line width in the vertical direction from the second stripe pattern. In this way, it is possible to obtain the specific image Im1 required for analysis in two directions, the vertical direction and the horizontal direction, which are perpendicular to each other, at once. In this case, since the specific image Im1 cannot be obtained and analyzed for each line, it is necessary to store the entire specific image Im1 in memory, but it is possible to identify the fiber direction by comparing the calculation result in the vertical direction with the calculation result in the horizontal direction.

[0102] That is, the control unit 16 can specify the fiber direction of the surface A1 of the sheet Sh1 by the direction specifying unit 24 from the difference between the calculation results in the vertical direction and the horizontal direction. In the example of Fig. 11, the line widths W11, W12 of the first pattern light P11 that projects the first stripe pattern (vertical stripe pattern) are 100 µm or more, so the horizontal unevenness information calculated from the first pattern light P11 is considered to be "independent of the fiber direction". On the other hand, the line widths W21, W22 of the second pattern light P12 that projects the second stripe pattern (horizontal stripe pattern) are less than 100 µm, so the vertical unevenness information calculated from the second pattern light P12 is considered to be "dependent on the fiber direction".

[0103] Therefore, when the same result (unevenness information) is obtained in the vertical direction and the horizontal direction, the direction specifying unit 24 determines that the fiber direction is perpendicular to the second stripe pattern (horizontal stripe pattern) by the second pattern light P12. In other words, the fiber direction is determined to be the same as the arrangement direction of the light parts L1 and the dark parts L2 of the second pattern light P12. On the other hand, when different results (unevenness information) are obtained in the vertical direction and the horizontal direction, the direction specifying unit 24 determines that the fiber direction is along the second stripe pattern (horizontal stripe pattern) by the second pattern light P12. In other words, the fiber direction is determined to be perpendicular to the arrangement direction of the light parts L1 and the dark parts L2 of the second pattern light P12. Here, whether the unevenness information is the same in the vertical direction and the horizontal direction is determined based on whether the difference between the unevenness information in the vertical direction and the unevenness information in the horizontal direction is equal to or less than a predetermined value, and if the difference is equal to or less than a predetermined value, the unevenness information in the vertical direction and the unevenness information in the horizontal direction is determined to be the same.

[0104] In this way, by narrowing the line width of only one of the stripe patterns of the grid pattern to obtain unevenness information that is "dependent on the fiber direction," it becomes possible to identify both the unevenness information and the fiber direction from the specific image Im1. If the fiber direction is identified, for example, in the inkjet type image forming unit 13, it becomes possible to predict the curl direction according to the fiber direction and perform curl correction in the condition determining unit 23.

[0105] [8] Variations A plurality of components included in the image processing device 10 may be distributed among a plurality of housings. For example, at least one of the components of the sheet identification device 2, such as the acquisition unit 21, the unevenness identification unit 22, the condition determination unit 23, the direction identification unit 24, and the thickness identification unit 25, may be provided in a housing separate from the control unit 16, without being limited to a configuration realized as one function of the control unit 16. In other words, the sheet identification device 2 does not need to be integrated with the image processing device 10, and at least a part of the sheet identification device 2 may be provided in a housing separate from the image processing device 10.

[0106] Furthermore, the sheet specifying device 2 only needs to have a function of specifying unevenness information related to unevenness on the surface A1 of the sheet Sh1, and the function of specifying the fiber direction of the sheet Sh1 and the thickness of the sheet Sh1, etc., can be omitted as appropriate. For example, when the function of specifying the thickness of the sheet Sh1 is omitted, the thickness sensor 5 and the thickness specifying unit 25 may be omitted.

[0107] In the first embodiment, the optical axis Ax1 of the light irradiation unit 3 is inclined at a predetermined angle θ1 with respect to the specific region R1 of the sheet Sh1, and the optical axis Ax2 of the imaging unit 4 is perpendicular to the specific region R1 of the sheet Sh1, but the present invention is not limited to this configuration. For example, the optical axis Ax1 of the light irradiation unit 3 may be perpendicular to the specific region R1 of the sheet Sh1, and the optical axis Ax2 of the imaging unit 4 may be inclined with respect to the specific region R1 of the sheet Sh1, or both the optical axis Ax1 and the optical axis Ax2 may be inclined with respect to the specific region R1 of the sheet Sh1.

[0108] The light irradiation unit 3 may include, for example, a projector, and may project an arbitrary pattern light P1 input as projection data onto the specific region R1. In other words, an image projected from the projector may be projected onto the specific region R1 as the pattern light P1. In this case, it is also easy to adopt a moving image as the pattern light P1.

[0109] Furthermore, the sheet Sh1 to be irradiated with the pattern light P1 is not limited to a sheet being conveyed, and may be, for example, a sheet Sh1 set in a paper feed cassette 141. In this case, by moving at least one of the sheet Sh1 and the imaging unit 4 and capturing a specific image Im1 in a state in which the sheet Sh1 and the imaging unit 4 are moved relatively, it becomes possible to capture a wide range of the sheet Sh1 while reducing the image magnification.

[0110] (Embodiment 2) 12, the image processing device 10A according to this embodiment differs from the image processing device 10 according to the first embodiment in that the sheet specifying device 2A includes an output unit 26. Hereinafter, the same components as those in the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted as appropriate.

[0111] The output unit 26 outputs at least one of the identification results from the unevenness identification unit 22, the direction identification unit 24, and the thickness identification unit 25. In this embodiment, as an example, the output unit 26 outputs the identification result by displaying it on the operation display unit 15, and notifies the user. The form of output of the identification result by the output unit 26 is not limited to display on the operation display unit 15, but may be transmission to an external device, writing to a non-transitory recording medium readable by a computer system, etc. The output unit 26 is provided in the control unit 16 as one function of the control unit 16.

[0112] The content output by the output unit 26 is, for example, the standard deviation σ as unevenness information, the arithmetic mean height (Sa), or information indicating the type of the sheet Sh1, in the case of the result of identification by the unevenness identification unit 22. Similarly, the content output by the output unit 26 is, for example, the fiber direction, or information indicating "longitudinal" or "lateral" in the case of the result of identification by the direction identification unit 24.

[0113] The output unit 26 may also output information such as a lifespan estimation result, a recommendation for a maintenance time, or a recommendation for a type of sheet Sh1, which is estimated from the identification result of the unevenness identification unit 22, etc. For example, wear may occur on parts of the image processing device 10A when the sheet Sh1 is conveyed, and the rougher the surface A1 of the sheet Sh1 to be conveyed, the more likely the wear will progress. In other words, since the degree of deterioration of the image processing device 10A differs depending on the surface roughness of the sheet Sh1 used, for example, if unevenness information of the sheet Sh1 is known in addition to the number of sheets Sh1 conveyed, the accuracy of the lifespan estimation of the image processing device 10A is improved. Therefore, the output unit 26 can output information such as a lifespan estimation result of the image processing device 10A or a recommendation for a maintenance time of the image processing device 10A by displaying it on the operation display unit 15, for example, and notify the user. Furthermore, in order to extend the life of the image processing device 10A, the output unit 26 can notify the user of information such as a recommendation for a sheet Sh1 having a flatter surface than the sheet Sh1 currently being used.

[0114] In particular, the sheet specifying device 2A according to this embodiment can calculate unevenness information having high linearity with the arithmetic mean height (Sa) as described in the embodiment 1. Therefore, even if the sheet Sh1 is not registered in advance in a database or the like, it can be reflected in, for example, the life estimation of the image processing device 10A.

[0115] The output unit 26 may also output information such as an estimation result of the front and back sides of the sheet Sh1 estimated from the identification result of the unevenness identification unit 22, etc. That is, depending on the type of the sheet Sh1, the roughness may differ between the front and back sides of the sheet Sh1, such as the back side being rougher than the front side. Therefore, if the unevenness information of the front and back sides of the sheet Sh1 is known, it is possible to estimate the front and back sides of the sheet Sh1. Therefore, the output unit 26 can output information such as the estimation result of the front and back sides of the sheet Sh1 by, for example, displaying it on the operation display unit 15, and notify the user. In this case, it is necessary to capture the specific image Im1 of both sides of the sheet Sh1 in the thickness direction. Therefore, two sensor units 20 may be arranged on either side of the conveying path T1, or a mirror or the like may be used to capture the specific image Im1 of both sides with one sensor unit 20, or the sheet Sh1 may be turned over.

[0116] As a modification of the second embodiment, the condition determining unit 23 may be omitted as appropriate.

[0117] (Embodiment 3) In this embodiment, the unevenness identification unit 22 does not use the specific image Im1 as it is, but identifies unevenness information related to the unevenness of the surface A1 of the sheet Sh1 based on the integrated image Im10. The integrated image Im10 is an image obtained by accumulating the specific image Im1 when the specific region R1 moves by a certain amount in the surface A1 of the sheet Sh1. In this way, by identifying unevenness information using the integrated image Im10 obtained by accumulating the specific image Im1 rather than the specific image Im1 itself, it becomes easier to identify unevenness information even if there is "blur" in the specific image Im1. That is, in this embodiment, the unevenness information is identified based on the integrated image Im10 that may contain a "blur" component by accumulating it in the first place, so that unevenness information can be identified regardless of "blur" in the specific image Im1, and it becomes easier to improve the identification accuracy of unevenness compared to the related technology. Hereinafter, common reference symbols are used for configurations similar to those of the first embodiment, and explanations are omitted as appropriate.

[0118] In the present disclosure, the "blurring" of an image such as the specific image Im1 means that the subject and the imaging unit 4 move relatively while the subject is being imaged by the imaging unit 4, causing the subject in the resulting image to appear overlapped and unclear. For example, if a high-speed camera or the like is used for the imaging unit 4, such "blurring" is less likely to occur, but this type of imaging unit 4 tends to be expensive.

[0119] In the present disclosure, "image accumulation" means accumulating pixel values ​​(brightness values) for each pixel. For example, when the exposure time of the imaging unit 4 capturing the specific image Im1 is 10 ms, the pixel values ​​for 10 ms are continuously accumulated for each pixel. In other words, the time required for the specific region R1 to move by a certain amount is set as the exposure time, and the pixel values ​​during the exposure time are continuously accumulated to obtain an accumulated image Im10 obtained by accumulating the specific image Im1 when the specific region R1 moves by a certain amount within the surface A1 of the sheet Sh1. In addition to such continuous accumulation of pixel values, "image accumulation" also includes discontinuous accumulation, for example, accumulating (adding) pixel values ​​for each pixel for multiple specific images Im1. In other words, by accumulating pixel values ​​for multiple specific images Im1 intermittently acquired while the specific region R1 moves by a certain amount, an accumulated image Im10 obtained by accumulating the specific image Im1 when the specific region R1 moves by a certain amount within the surface A1 of the sheet Sh1 is obtained. Furthermore, it is possible to obtain an average value of the pixel values ​​of a predetermined number of pixels by accumulating the pixel values ​​of the predetermined number of pixels and then dividing the pixel value by the predetermined number of pixels. This averaging process for obtaining an average value is also included in the "accumulation of an image."

[0120] In the present embodiment, as an example, the pattern light P1 forms a stripe pattern in which light portions L1 and dark portions L2 are alternately arranged on the specific region R1 as shown in FIG. 13. That is, by projecting the pattern light P1, a luminance distribution of a stripe pattern including light portions L1 and dark portions L2 is generated in the specific region R1. Here, the light portions L1 are brighter than the dark portions L2. In other words, the stripe pattern is a pattern in which a plurality of light portions L1 are arranged at intervals, or a pattern in which a plurality of dark portions L2 are arranged at intervals. That is, by projecting the pattern light P1 in the specific region R1, a stripe pattern is formed in which linear light portions L1 and linear dark portions L2 are alternately arranged in a direction perpendicular to each longitudinal direction. In the present embodiment, as an example, linear light portions L1 and dark portions L2 extending along the conveying direction D1 of the sheet Sh1 are arranged so as to be alternately arranged in the conveying direction D1.

[0121] In this embodiment, the sheet Sh1 moves relative to the sensor unit 20 including the light irradiation unit 3 and the imaging unit 4 as the sheet Sh1 is transported along the transport path T1 in the transport direction D1. Therefore, the specific region R1 that is the target of irradiation with the pattern light P1 by the light irradiation unit 3 and the target of imaging of the specific image Im1 by the imaging unit 4 moves along the transport direction D1 within the front surface A1 of the sheet Sh1. Therefore, the transport direction D1 is the movement direction of the specific region R1 within the front surface A1 of the sheet Sh1. Therefore, in this embodiment, at least one of the light portion L1 and the dark portion L2 of the stripe pattern extends along the movement direction of the specific region R1 within the front surface A1 of the sheet Sh1.

[0122] Specifically, the stripe pattern formed by projecting the pattern light P1 onto the surface A1 of the sheet Sh1 has a shape in which both the light portion L1 and the dark portion L2 extend along the transport direction D1, which is the moving direction of the specific region R1. However, even if at least one of the light portion L1 and the dark portion L2 is not strictly parallel to the moving direction of the specific region R1, the stripe pattern is considered to be aligned with the moving direction of the specific region R1 as long as the angle between the moving direction of the specific region R1 and the light portion L1 is within a tolerance range (a few dozen degrees). This makes it easier for the influence of the unevenness of the surface A1 to appear in the integrated image Im10 obtained by integrating the specific images Im1 when the specific region R1 moves within the surface A1 of the sheet Sh1.

[0123] However, in the method of determining the roughness of the surface A1 from a shadow image caused by unevenness as in the above-mentioned related art, for example, in the case of a paper sheet Sh1, the calculation result strongly reflects the local fiber unevenness, so the calculation result does not necessarily have a linear relationship with the arithmetic mean height (Sa). Therefore, in the method of the above-mentioned related art, it is difficult to determine the magnitude of the surface roughness of a sheet Sh1 of the same type (for example, plain paper) from the calculation result, even if it is possible to distinguish between glossy paper (gloss paper) and plain paper, which have a high degree of flatness. Therefore, in order to determine the magnitude of surface roughness in the method of the above-mentioned related art, it is necessary to prepare in advance, for example, a table (database) that associates the calculation results and the arithmetic mean height (Sa) for various sheets Sh1.

[0124] In contrast, in the sheet specifying device 2 according to this embodiment, the line width of the pattern light P1, the predetermined angle θ1, etc. are optimized to reduce the influence of local fibers, and it becomes possible to calculate unevenness information having high linearity with the arithmetic mean height (Sa). Therefore, with the method of this embodiment, it is possible to uniquely determine the arithmetic mean height (Sa) from the calculation result of the unevenness specifying unit 22, even if a table (database) that associates the calculation result (unevenness information) with the arithmetic mean height (Sa) is not prepared in advance.

[0125] 14 and 15 show examples of a specific image Im1 and an integrated image Im10 obtained by the sheet specifying device 2 according to this embodiment. Here, the imaging conditions for the specific image Im1 are a predetermined angle θ1 of 40 degrees, a resolution (number of pixels) of the imaging element 41 of 100×100, a line width W1 (see FIG. 13) of the light portion L1 of the stripe pattern formed by the pattern light P1 of 120 μm, and a line width W2 (see FIG. 13) of the dark portion L2 of 120 μm. Furthermore, the image magnification M is "1", and the extension directions (longitudinal directions) of the light portion L1 and the dark portion L2 of the stripe pattern formed by the pattern light P1 are the same as the transport direction D1 (movement direction of the specific region R1). Here, Fig. 14 shows two types of sheets Sh1 with arithmetic mean heights Sa of 0.8 μm and 2.3 μm, and Fig. 15 shows two types of sheets Sh1 with arithmetic mean heights Sa of 5.16 μm and 6.1 μm, for a total of four types of sheets. In both Fig. 14 and Fig. 15, the specific image Im1 is shown on the left side, and the integrated image Im10 obtained by integrating the specific image Im1 is shown on the right side.

[0126] The specific image Im1 is composed of a plurality of pixels, each of which has a pixel value corresponding to the luminance. In the present embodiment, as an example, the relationship between the luminance and the pixel value is defined such that the pixel value increases as the luminance increases. Therefore, in the specific image Im1 obtained by capturing the specific region R1 onto which the pattern light P1 is projected, the pixel value of the pixel corresponding to the bright portion L1 is relatively large, and the pixel value of the pixel corresponding to the dark portion L2 is relatively small.

[0127] The integrated image Im10 is an image obtained by accumulating the specific image Im1 when the specific region R1 moves by a predetermined number of pixels of the specific image Im1. Specifically, the integrated image Im10 is an image obtained by accumulating a predetermined number of pixels of the specific image Im1 in the transport direction D1, which is the movement direction of the specific region R1, and then dividing and averaging the pixel value of each pixel by the pixel number. Here, as an example, the predetermined number of pixels accumulated in the integrated image Im10 is 50 pixels (pix.). In other words, each pixel of the integrated image Im10 has a pixel value that is the average value of the pixel values ​​of 50 pixels (pix.) in the transport direction D1 in the specific image Im1.

[0128] The upper part of Fig. 14 shows the specific image Im1 and the integrated image Im10 for glossy paper with an arithmetic mean height (Sa) of 0.8 μm, i.e., high flatness, and the lower part of Fig. 14 shows the specific image Im1 and the integrated image Im10 for plain paper with an arithmetic mean height (Sa) of 2.3 μm. Similarly, the upper part of Fig. 15 shows the specific image Im1 and the integrated image Im10 for plain paper with an arithmetic mean height (Sa) of 5.16 μm, and the lower part of Fig. 15 shows the specific image Im1 and the integrated image Im10 for plain paper with an arithmetic mean height (Sa) of 6.1 μm.

[0129] As shown in Fig. 14 and Fig. 15, the larger the arithmetic mean height (Sa), the larger the deformation and distortion of the stripe pattern caused by the pattern light P1 in the specific image Im1. Specifically, when the deformation and distortion of the stripe pattern becomes large, the boundary between the light part L1 and the dark part L2 of the stripe pattern becomes distorted, and the variation in the line width of each of the light part L1 and the dark part L2 becomes large. In other words, when the arithmetic mean height (Sa) becomes large, the undulation component of the height of the surface A1 becomes large, and the variation in the line width of each of the light part L1 and the dark part L2 becomes large. Thus, in Fig. 14 and Fig. 15, it is clear that the deformation or distortion occurs in the stripe pattern caused by the pattern light P1 in the specific image Im1 according to the unevenness of the surface A1.

[0130] Furthermore, as shown in Fig. 14 and Fig. 15, in the integrated image Im10, the line width of the intermediate layer L3 on the boundary between the bright part L1 and the dark part L2 increases as the arithmetic mean height (Sa) increases. Specifically, when the deformation and distortion of the stripe pattern caused by the pattern light P1 in the specified image Im1 increases, the boundary between the bright part L1 and the dark part L2 of the stripe pattern becomes distorted, and the line width of the intermediate layer L3 generated by integrating (averaging) this becomes larger (thicker). Thus, in Fig. 14 and Fig. 15, it is clear that the intermediate layer L3 with a line width corresponding to the unevenness of the surface A1 is generated in the integrated image Im10. In the sheet specifying device 2 according to this embodiment, unevenness information of the surface A1 of the sheet Sh1 is specified by analyzing the width (line width) of the intermediate layer L3 in the integrated image Im10.

[0131] In particular, in this embodiment, the image obtained by accumulating the specific images Im1 when the specific region R1 moves by a certain amount is the integrated image Im10, and the amount of movement is equal to or greater than the pixel pitch of the imaging unit 4 that captures the specific image Im1 divided by the image magnification M. In this embodiment, the image magnification M is assumed to be "1", so the amount of movement of the specific region R1 is equal to or greater than the pixel pitch of the imaging unit 4. As a result, the specific region R1 moves by the amount of movement, and the integrated image Im10 is obtained by accumulating the specific images Im1 in which the sheet Sh1 has moved by at least the pixel pitch. Therefore, in the integrated image Im10, an intermediate layer L3 is likely to occur according to the variation in the line width of each of the light portion L1 and the dark portion L2.

[0132] However, as in the integrated image Im10 in the lower part of FIG. 15, there are cases where the width (line width) of the intermediate layer L3 is not uniform over the entire area of ​​the integrated image Im10 in the conveying direction D1. This is because the variation in the line width of each of the bright and dark parts L1 and L2 is not evened out even in the integrated image Im10, and the variation components of the line width of each of the bright and dark parts L1 and L2 due to the unevenness of the surface A1 remain. For example, as in the case of a paper sheet Sh1, a wavy component generated by the continuous entanglement of a large number of fibers occurs in a relatively long period, so that the line width of each of the bright and dark parts L1 and L2 varies in the integrated image Im10 according to such long-period unevenness. Therefore, in order to make the width of the intermediate layer L3 uniform over the entire area of ​​the conveying direction D1 in the integrated image Im10, it is preferable to set the movement amount of the specific region R1 for obtaining the integrated image Im10 to be equal to or greater than the period (distance) of the long-period unevenness. This allows the specific image Im1 to be integrated over a range equal to or greater than the period (distance) of the long-period irregularities to obtain an integrated image Im10, so that the width of the intermediate layer L3 can be made uniform over the entire area in the transport direction D1 in the integrated image Im10.

[0133] FIG. 16 shows the pixel values ​​of each pixel at an arbitrary position (one row) in the conveying direction D1 of the integrated image Im10 for the above four types of sheet Sh1, when the predetermined number of pixels to be integrated is set to be equal to or greater than the period of the long-period unevenness of the sheet Sh1. In FIG. 16, the horizontal axis represents the pixel number (pixel position) in the "row direction" in which the light parts L1 and the dark parts L2 are arranged in the integrated image Im10 (the left-right direction in FIG. 14 and FIG. 15), and the vertical axis represents the pixel value (brightness value). That is, according to FIG. 16, it can be seen that a region corresponding to the intermediate layer L3 exists between the light parts L1 having a pixel value of "50" or more and the dark parts L2 having a pixel value of less than "30". The width of the intermediate layer L3 corresponds to the slope of the rise (or fall) of the pixel value between the light parts L1 and the dark parts L2, and the gentler the slope, the larger the width of the intermediate layer L3. In other words, the larger (rougher) the arithmetic mean height Sa of the surface A1 of the sheet Sh1 is, the gentler the slope of the rise (or fall) of the pixel values ​​between the light area L1 and the dark area L2 becomes. In other words, among the graphs for the four types of sheet Sh1 shown in FIG. 16, the slope of the graph with the arithmetic mean height Sa of "6.1" is the gentlest.

[0134] Then, the width of the intermediate layer L3 in the integrated image Im10 can be calculated by extracting the width of the intermediate layer L3 from the graph in FIG. 16 described above and calculating a representative value (for example, an average value, a mode value, or a median value) of the widths of the multiple intermediate layers L3 for each integrated image Im10. The width of the intermediate layer L3 calculated in this way, that is, the average value of the slope width in the graph in FIG. 16, is expressed in terms of the number of pixels as shown in FIG. 17. In FIG. 17, the horizontal axis represents the arithmetic mean height Sa, and the vertical axis represents the width of the intermediate layer L3 (average value of the slope width). In the example in FIG. 17, it can be confirmed that there is high linearity between the width of the intermediate layer L3 in the integrated image Im10 and the arithmetic mean height Sa for at least the above four types of sheets Sh1.

[0135] As described above, by identifying unevenness information using the integrated image Im10 obtained by accumulating the specific image Im1, it becomes easier to identify unevenness information even if there is "blurring" in the specific image Im1. That is, in the imaging unit 4 that captures the specific image Im1, in order to capture the specific image Im1 as bright as possible, it is necessary to make the exposure time relatively long, and "blurring" may occur in the specific image Im1 due to the movement of the subject (sheet Sh1).

[0136] As an example, when the conveying speed of the sheet Sh1 is set to 500 mm / sec to improve the productivity of the image processing device 10, if the exposure time is 10 ms at the maximum with the image capturing unit 4 having a frame rate of 100 Hz, the sheet Sh1 moves 5 mm within the exposure time. Therefore, in the specific image Im1, "blurring" occurs due to the movement of the sheet Sh1, and in the method of determining the roughness of the surface A1 from the shadow image of the specific image Im1 as in the related art, the shadow is crushed by the "blurring" and it is difficult to determine the roughness of the surface A1. When the related art is applied, in order to suppress the "blurring" of the specific image Im1, it becomes necessary to slow down the conveying speed of the sheet Sh1 or to shorten the exposure time by using a high-sensitivity image capturing element 41 in the image capturing unit 4. This causes problems such as a decrease in the productivity of the image processing device 10 and a high cost for the image capturing unit 4. In contrast, in the sheet identifying device 2 according to the present embodiment, unevenness information is identified using the integrated image Im10 that may contain a "blurring" component in the first place, so there is no need to suppress the "blurring" of the specific image Im1. Therefore, in this embodiment, it is easy to improve the productivity of the image processing device 10 and reduce the cost of the imaging unit 4.

[0137] Furthermore, in this embodiment, the movement amount of the specific region R1 for obtaining the integrated image Im10 is set to be equal to or greater than the period of the long-period unevenness of the sheet Sh1. The movement amount is determined by at least one of the conveying speed of the sheet Sh1 and the exposure time of the imaging unit 4 for capturing the specific image Im1. As a result, the width of the intermediate layer L3 becomes uniform throughout the entire area of ​​the integrated image Im10 in the conveying direction D1, so that it is possible to obtain the width of the intermediate layer L3 even when focusing on an arbitrary position (one row) in the conveying direction D1 of the integrated image Im10. As a result, the computation load for calculating the width of the intermediate layer L3 can be reduced.

[0138] Next, a specific process for identifying unevenness information based on the identified image Im1 by the unevenness identifying unit 22 will be described with reference to Fig. 18. Steps S1, S2, ... in the flowchart shown in Fig. 18 indicate the numbers of the processing procedures (steps) executed by the control unit 16. The process described below starts, for example, in synchronization with the timing when the sheet Sh1 passes through a position (monitor position) on the conveying path T1 corresponding to the sensor unit 20.

[0139] When the purpose of analysis of the specific image Im1 including the pattern light P1 is to restore a three-dimensional shape, it can be realized by, for example, a method of continuously projecting a plurality of pattern lights P1 and using a Fourier transform of the specific image Im1 to calculate the phase change of the pattern light P1. However, this method has a relatively high computation load, takes a relatively long time to calculate the roughness (unevenness information) of the surface A1, and also requires relatively high hardware (CPU, GPU, memory, etc.) costs. Therefore, in this embodiment, instead of the above method, the following method is adopted so that the roughness (unevenness information) of the surface A1 can be calculated by a relatively simple computation process.

[0140] That is, in this embodiment, the unevenness identification unit 22 calculates the width (line width) of the intermediate layer L3 by focusing on any one row (one line) of the integrated image Im10, with the arrangement direction of the light parts L1 and the dark parts L2 in the integrated image Im10 (the left-right direction in Figs. 14 and 15) as the "row direction". That is, the integrated image Im10 is an image of "N pixels x M rows" in which N pixels are arranged in the arrangement direction of the light parts L1 and the dark parts L2, and the unevenness identification unit 22 calculates the line width for any one of the M rows included in the integrated image Im10. The unevenness identification unit 22 calculates the line width of the intermediate layer L3 calculated by focusing on one row in this way as unevenness information. As a result, the unevenness identification unit 22 can obtain unevenness information that is correlated with the arithmetic mean height (Sa) of the surface A1 based on the line width of the intermediate layer L3.

[0141] <Step S1> Specifically, in step S1, the control unit 16 determines whether the sheet Sh1 reaches the monitor position, that is, a position on the transport path T1 corresponding to the sensor unit 20. When the sheet feeding unit 14 supplies the sheet Sh1 to the image forming unit 13, the control unit 16 determines that the sheet Sh1 reaches the monitor position (S1: Yes) if the sheet Sh1 is detected by a sensor at the monitor position, and shifts the process to step S2. On the other hand, if the sheet Sh1 is not detected by the sensor at the monitor position, the control unit 16 determines that the sheet Sh1 has not reached the monitor position (S1: No), and shifts the process to step S1.

[0142] <Steps S2 and S3> In step S2, the control unit 16 controls the light irradiation unit 3 by the acquisition unit 21 to cause the light irradiation unit 3 to irradiate the pattern light P1. As a result, the pattern light P1 is projected onto the specific region R1 on the front surface A1 of the sheet Sh1. In step S3, the control unit 16 controls the imaging unit 4 by the acquisition unit 21 to cause the imaging unit 4 to capture the specific region R1 on which the pattern light P1 is projected. As a result, a specific image Im1, which is an image of the specific region R1 on the front surface A1 of the sheet Sh1, is generated by the imaging unit 4.

[0143] <Step S4> In step S4, the control unit 16 accumulates the specific images Im1 when the specific region R1 moves a certain amount of movement on the surface A1 of the sheet Sh1 to generate an accumulated image Im10. Specifically, the time required for the specific region R1 to move a certain amount of movement (for example, 5 mm) on the surface A1 is set as the exposure time of the imaging unit 4, and then imaging is performed by the imaging unit 4, so that the image acquired by the acquisition unit 21 becomes the accumulated accumulated image Im10. Here, in this embodiment, the amount of movement of the specific region R1 for obtaining the accumulated image Im10 is set to be equal to or greater than the period of the long-period unevenness of the sheet Sh1. The generation of the accumulated image Im10 may be performed in the control unit 16.

[0144] <Step S5> In step S5, the control unit 16 causes the acquisition unit 21 to acquire one row (one line) of the integrated image Im10 from the imaging unit 4. That is, the acquisition unit 21 acquires one row of the integrated image Im10, which corresponds to one pixel in the column direction. The imaging unit 4 (image sensor 41) is generally designed to sequentially read images one row at a time, so that acquiring one row of the integrated image Im10 and analyzing it (steps S6 and S7) in this manner can reduce memory usage. The row to be acquired at this time may be, for example, predetermined or may be set by the user.

[0145] <Step S6> In step S6, the control unit 16 causes the acquisition unit 21 to perform preprocessing on the integrated image Im10. At this time, the target of the preprocessing is one row (one line) of the integrated image Im10 acquired in step S5. That is, the control unit 16 performs preprocessing on the integrated image Im10 row by row. The preprocessing includes, for example, a filtering process. Specifically, the control unit 16 performs noise removal and the like on one row of the integrated image Im10 by filtering. The preprocessing may include a trimming process that cuts out only a part of the integrated image Im10, and may narrow down the range to be processed in step S7. Moreover, the filtering process and the like are not essential and can be omitted as appropriate.

[0146] <Step S7> In step S7, the control unit 16 extracts width data indicating the width (line width) of the intermediate layer L3 from the integrated image Im10 in the unevenness identification unit 22. At this time, the width data is extracted from one row (one line) of the integrated image Im10 acquired in step S5. That is, the control unit 16 executes extraction of width data for the integrated image Im10 on a row-by-row basis. Specifically, the control unit 16 classifies each pixel of the integrated image Im10 for one row into a bright portion L1 and a dark portion L2, with pixels having a pixel value equal to or greater than a first threshold (for example, "50") as a bright portion L1 and pixels having a pixel value less than a second threshold (for example, "30") as a dark portion L2. Here, pixels that are not included in the bright portion L1 or the dark portion L2, that is, pixels having a pixel value less than the first threshold and equal to or greater than the second threshold, are classified into the intermediate layer L3. Then, the control unit 16 calculates the number of pixels in the intermediate layer L3 as width data. At this time, the control unit 16 extracts the total line width of a plurality of lines in the intermediate layer L3 by extracting the number of pixels in the intermediate layer L3 for the entirety of one row of the integrated image Im10.

[0147] The first and second thresholds used to classify pixels into the bright area L1, the dark area L2, and the intermediate layer L3 are, for example, values ​​determined based on the average value of a plurality of pixels, or predetermined values ​​(predetermined values). The second threshold is smaller than the first threshold. The control unit 16 may extract the line width for each intermediate layer L3 by extracting the number of pixels corresponding to the intermediate layers L3 that are continuous in the row direction. In this case, the control unit 16 may use the line width of each of the intermediate layers L3 as the width data, not limited to the total of the multiple intermediate layers L3, or may use a representative value (for example, the average value, the mode, or the median value) of the line widths of the multiple intermediate layers L3 as the width data.

[0148] <Step S8> In step S8, the control unit 16 calculates the arithmetic mean height Sa from the width data of the intermediate layer L3 in the unevenness specifying unit 22. That is, since there is a high degree of linearity between the width (line width) of the intermediate layer L3 in the integrated image Im10 and the arithmetic mean height Sa, it is possible to uniquely determine the arithmetic mean height Sa from the width of the intermediate layer L3 using a linear regression model.

[0149] <Step S9> In step S9, the control unit 16 determines image processing conditions in the condition determination unit 23. That is, the condition determination unit 23 determines image processing conditions including image formation conditions according to the arithmetic mean height Sa calculated in step S8. As an example, when the arithmetic mean height Sa increases, the condition determination unit 23 sets image formation conditions such as increasing the fixing temperature, decreasing the conveying speed, and increasing the transfer voltage. As a result, when an image is formed on the sheet Sh1 by the image forming unit 13, image formation conditions according to the unevenness of the surface A1 of the sheet Sh1 are automatically applied.

[0150] The procedure of the sheet identification method described above is merely an example, and the order of the processes shown in the flowchart of FIG. 18 may be changed as appropriate.

[0151] Furthermore, it is not essential that at least one of the light portion L1 and the dark portion L2 of the stripe pattern extends along the moving direction (transport direction D1) of the specific region R1 in the surface A1 of the sheet Sh1, and for example, both the light portion L1 and the dark portion L2 may be perpendicular to the transport direction D1. Even in this case, as the specific region R1 moves in the surface A1, the pattern light P1 projected onto the surface A1 of the sheet Sh1 dynamically undergoes deformation or distortion according to the unevenness of the surface A1. Therefore, even when such a pattern light P1 is used, the unevenness identifying unit 22 can identify unevenness information based on the integrated image Im10, similar to the third embodiment.

[0152] In addition, in the third embodiment, the specific image Im1 is integrated over time, but the specific image Im1 may be integrated over space. In other words, the "integration of images" also includes integration in which pixel values ​​are integrated (added) for each pixel of the image (specific image Im1) in the specific region R1 while moving the specific region R1 within one image. In other words, by integrating pixel values ​​for the image (specific image Im1) in the specific region R1 cut out while the specific region R1 moves by a certain amount within one image, an integrated image Im10 is obtained by integrating the specific image Im1 when the specific region R1 moves by a certain amount.

Claims

1. an acquisition unit that acquires a specific image, which is an image of a specific area on a surface of a sheet on which an image is to be formed or read, onto which the pattern light is projected; an unevenness specifying unit that specifies unevenness information related to unevenness on the surface of the sheet based on the specific image, the pattern light forms a stripe pattern in which light and dark areas are arranged alternately on the specific region, the stripe pattern includes a first stripe pattern and a second stripe pattern that are perpendicular to each other; The first stripe pattern and the second stripe pattern have different widths of at least one of the bright portions and the dark portions. Seat identification device.

2. a condition determination unit that determines an image processing condition related to image formation or image reading based on the unevenness information identified by the unevenness identification unit, The sheet identification device according to claim 1 .

3. a first virtual line connecting a light irradiation unit that irradiates the pattern light and a center of the specific region is inclined at a predetermined angle with respect to a second virtual line along a conveyance direction of the sheet; The sheet identification device according to claim 1 .

4. The predetermined angle is equal to or greater than 20 degrees and equal to or less than 90 degrees. The sheet identification device according to claim 3 .

5. The light irradiation unit that irradiates the pattern light includes: A light source; a shield that blocks a portion of the light output from the light source to transmit the pattern light; The sheet identification device according to claim 1 .

6. At least one of the widths of the bright portion and the dark portion is 60 μm or more and 500 μm or less. The sheet identification device according to claim 1 .

7. The unevenness information includes information regarding at least one of a dimension of the unevenness of the surface in a direction perpendicular to a plane along the surface and a dimension along the plane. The sheet identification device according to claim 1 .

8. the unevenness specifying unit specifies the unevenness information based on at least a variation in line width of the pattern light on the specified region. The sheet identification device according to claim 1 .

9. The sheet specifying device according to claim 1 ; and an image processing unit that performs at least one of forming an image and reading an image on the sheet. Image processing device.

10. Acquiring a specific image, which is an image of a specific area on a surface of a sheet on which an image is to be formed or read, onto which the pattern light is projected; and identifying unevenness information relating to unevenness on the surface of the sheet based on the specific image, the pattern light forms a stripe pattern in which light and dark areas are arranged alternately on the specific region, the stripe pattern includes a first stripe pattern and a second stripe pattern that are perpendicular to each other; The first stripe pattern and the second stripe pattern have different widths of at least one of the bright portions and the dark portions. Sheet identification method.

11. an acquisition unit that acquires a specific image, which is an image of a specific area on a surface of a sheet on which an image is to be formed or read, onto which the pattern light is projected; an unevenness specifying unit that specifies unevenness information related to unevenness on the surface of the sheet based on an integrated image obtained by integrating the specific images when the specific region moves by a certain movement amount on the surface of the sheet, the pattern light forms a stripe pattern in which light and dark areas are arranged alternately on the specific region, the stripe pattern includes a first stripe pattern and a second stripe pattern that are perpendicular to each other; The first stripe pattern and the second stripe pattern have different widths of at least one of the bright portions and the dark portions. Seat identification device.

12. a condition determination unit that determines an image processing condition related to image formation or image reading based on the unevenness information identified by the unevenness identification unit, The sheet identification device according to claim 11.

13. the movement amount is determined by at least one of a conveying speed of the sheet and an exposure time of an imaging unit that captures the specific image; The sheet identification device according to claim 11.

14. the movement amount is equal to or greater than a value obtained by dividing a pixel pitch of an imaging unit that captures the specific image by an image magnification. The sheet identification device according to claim 11.

15. The light irradiation unit that irradiates the pattern light includes: A light source; a shield that blocks a portion of the light output from the light source to transmit the pattern light; The sheet identification device according to claim 11.

16. At least one of the bright portion and the dark portion of the stripe pattern extends along the moving direction of the specific region on the surface of the sheet. The sheet identification device according to claim 11.

17. The unevenness information includes information regarding at least one of a dimension of the unevenness of the surface in a direction perpendicular to a plane along the surface and a dimension along the plane. The sheet identification device according to claim 11.

18. the unevenness specifying unit specifies the unevenness information based on at least a variation in line width of the pattern light on the specified region. The sheet identification device according to claim 11.

Images