Reading device, reading method, program, inspecting device, and printing system

Abstract

Provided are a reading device, a reading method, a program, an inspecting device, and a printing system capable of acquiring preferable read data of a printed image, for an inspection or the like that employs the read data of the printed image. A reading device (30) is provided with a transillumination device (44) equipped with an image sensor (32), an imaging lens (34), a transmission bright field illuminating device (40) and a transmission dark field illuminating device (42), and a transillumination condition setting unit for setting a transmission bright field illumination condition in accordance with processing to be performed with respect to read data, wherein the transmission bright field illuminating device and the transmission dark field illuminating device are each controlled in accordance with a transillumination condition.

Description

Reading device, reading method, program, inspection device, and printing system

[0001] The present invention relates to a reading device, a reading method, a program, an inspection device, and a printing system.

[0002] Inkjet printing devices apply image processing technology to scanned data of printed images to measure the accuracy of the nozzle ejection direction of the inkjet head, correct printing irregularities, and detect streak-like defects that tend to occur during printing. A reading device such as a scanner is used to read the printed image.

[0003] Patent Document 1 describes an apparatus for detecting scratches and the like on a transparent original such as photographic film by switching between dark-field illumination and bright-field illumination. The apparatus described in this document includes a light-blocking plate that is configured to be freely movable in the sub-scanning direction, and the light-blocking plate is moved over a light diffusion plate to block illumination light entering the lens aperture. This allows switching to dark-field illumination, in which only light obliquely incident from both ends of the light diffusion plate in the sub-scanning direction illuminates the transparent original.

[0004] Japanese Patent Application Laid-Open No. 2000-266690

[0005] The device described in Patent Document 1 makes fine scratches and foreign matter on a transparent original less noticeable, thereby suppressing degradation of image quality caused by scratches, etc. However, when using the scanned data to detect defects in a printed image, scanned data in which scratches, etc. are less noticeable is not suitable.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a reading device, reading method, program, inspection device, and printing system that can obtain preferable read data of a printed image for inspections, etc., in which read data of a printed image is used.

[0007] A reading device according to a first aspect of the present disclosure includes an image sensor that reads a printed image printed on a substrate and generates read data of the printed image; an imaging lens that forms an optical image of the printed image on the image sensor and defines a field of view that represents the range in which an illumination device that directly incidents illumination light is positioned; a transmitted illumination device that is positioned opposite the light receiving surface of the image sensor and includes a transmitted brightfield illumination device that is positioned within the field of view of the imaging lens and a transmitted darkfield illumination device that is positioned outside the field of view of the imaging lens; a transmitted illumination condition setting unit that sets the transmitted illumination conditions to be applied to the transmitted illumination device; and one or more first processors, wherein the transmitted illumination condition setting unit sets the transmitted brightfield illumination conditions to be applied to the transmitted brightfield illumination device and sets the transmitted darkfield illumination conditions to be applied to the transmitted darkfield illumination device in accordance with the processing performed on the read data, and the one or more first processors control each of the transmitted brightfield illumination device and the transmitted darkfield illumination device in accordance with the transmitted illumination conditions set using the transmitted illumination condition setting unit.

[0008] According to the reading device of the first aspect of the present disclosure, the brightfield illumination device and the darkfield illumination device are controlled in accordance with the processing performed on the read data of the printed image, thereby making it possible to obtain read data of the printed image that is suitable for processing such as an inspection in which the read data of the printed image is used.

[0009] The print image may include an inspection image, which may include a ladder pattern and a gradation pattern.

[0010] The transmitted bright-field illuminator is positioned at a position where the optical axis of the imaging lens passes through, so that at least a portion of the direct light of the emitted light can be focused onto the image sensor by the imaging lens. The transmitted dark-field illuminator can be positioned at a position outside the range where light directly incident on the imaging lens passes, so that all of the direct light of the emitted light is not focused onto the image sensor by the imaging lens.

[0011] Direct light is light emitted from an illumination device that travels without being reflected or diffused by the substrate, ink, etc. Light reflected by the substrate, etc. becomes reflected light and is reflected in various directions. Similarly, light diffused by the substrate, etc. becomes diffused light and is diffused in various directions. A portion of the reflected light and a portion of the diffused light can reach the light receiving surface of the image sensor via the imaging lens.

[0012] In a reading device according to a second aspect, in the reading device of the first aspect, the transmitted illumination condition setting unit may set the amount of light emitted by the transmitted illumination device based on a first light transmittance obtained from reading data obtained by turning on the transmitted brightfield illumination device and reading a non-ink-applied region, which is a region of the substrate where ink is not applied, or a state in which there is no substrate, or based on a second light transmittance obtained from reading data obtained by turning on the transmitted darkfield illumination device and reading a non-ink-applied region of the substrate or a state in which there is no substrate.

[0013] According to this aspect, the reference pixel values ​​of the read data are defined based on the read data of the non-ink-applied region of the substrate or the read data in the absence of the substrate, thereby enabling the read sensitivity of the image sensor to be set based on the defined reference pixel values.

[0014] A reading device according to a third aspect may be the reading device according to the first or second aspect, wherein the image sensor is a color sensor and a line sensor.

[0015] According to this aspect, a color image can be read and read data for each color can be generated.

[0016] A reading device according to a fourth aspect may be a reading device according to any one of the first to third aspects, wherein the transmission dark field illumination device includes a first transmission dark field illumination device that emits illumination light in a first direction, and a second transmission dark field illumination device that emits illumination light in a second direction different from the first direction.

[0017] In this aspect, the first direction and the second direction may be perpendicular to each other.

[0018] A reading device according to a fifth aspect is the reading device of the fourth aspect, wherein the transmitted light illumination condition setting unit may set a first transmitted light dark field illumination condition in which either the first transmitted light dark field illumination device or the second transmitted light dark field illumination device is turned on, or a second transmitted light dark field illumination condition in which both the first transmitted light dark field illumination device and the second transmitted light dark field illumination device are turned on, depending on the processing to be performed on the read data.

[0019] According to this aspect, it is possible to control the amount of emitted illumination light in a preferable manner and to realize illumination conditions that are preferable for defect detection in accordance with the processing that is performed on the read data.

[0020] A reading device according to a sixth aspect is a reading device according to any one of the first to fifth aspects, wherein the transmitted illumination device may include a light diffusing member that diffuses the emitted light from at least one of the transmitted bright-field illumination device and the transmitted dark-field illumination device.

[0021] A reading device according to a seventh aspect is a reading device according to any one of the first to sixth aspects, wherein the reading device is a reflective lighting device that is arranged on the same side as the image sensor with respect to a space divided in two by a plane perpendicular to the optical axis of the imaging lens at the reading position of the image sensor, and is equipped with a reflective lighting device that irradiates illumination light onto a substrate supported at the reading position, a reflective lighting condition setting unit that sets reflective lighting conditions to be applied to the reflective lighting device, and one or more second processors, and the one or more second processors may control the reflective lighting device according to the reflective lighting conditions.

[0022] According to this aspect, it is possible to control the amount of emitted illumination light in a preferable manner and to realize illumination conditions that are preferable for defect detection in accordance with the processing that is performed on the read data.

[0023] A reading device according to an eighth aspect is the reading device of the seventh aspect, wherein the reflective lighting device includes a first reflective lighting device that emits illumination light in a third direction and a second reflective lighting device that emits illumination light in a fourth direction different from the third direction, and the reflective lighting condition setting unit may set a first reflective lighting condition that turns on either the first reflective lighting device or the second reflective lighting device, or a second reflective lighting condition that turns on both the first reflective lighting device and the second reflective lighting device, depending on the processing performed on the read data.

[0024] In this aspect, the third direction and the fourth direction may be perpendicular to each other.

[0025] A reading device according to a ninth aspect is a reading device according to any one of the first to eighth aspects, wherein the one or more first processors may set the amount of light emitted from the transmitted dark field illumination device so that, when the pixel values ​​of the read data are larger in relatively bright parts of the printed image than in relatively dark parts, the maximum average value of the pixel values ​​of the read data of the solid images in the first test image, which is printed on a transparent substrate and includes a plurality of solid images with different density values ​​for each of one or more ink colors, exceeds the average value of the pixel values ​​of the read data in non-ink-applied areas of the substrate.

[0026] According to this aspect, the pixel values ​​of the high density areas of the printed image, which are susceptible to noise, are made relatively large in the read data, making it possible to set lighting conditions that are suitable for obtaining read data that is suitable for correcting unevenness in the high density areas.

[0027] A reading device according to a tenth aspect is a reading device according to any one of the first to ninth aspects, wherein one or more first processors may adjust the amount of light emitted from the transmitted dark-field illumination device so that the maximum pixel value in the read data of a printed image printed on a transparent substrate is equal to the pixel value of a non-ink-applied area on the substrate.

[0028] According to this aspect, the amount of emitted illumination light is controlled based on the pixel values ​​of the non-ink-applied areas in the read data, so that read data is obtained in which the values ​​of the read data of the printed image are large and the bright parts are not crushed.

[0029] A reading device according to an eleventh aspect is a reading device according to any one of the first to tenth aspects, wherein one or more first processors may adjust the amount of light emitted from the transmitted dark-field illumination device so that the maximum pixel value in the read data of an ink-applied area on a transparent substrate, where the amount of ink per unit area is equal to or less than a specified amount, exceeds the pixel value of a non-ink-applied area on the substrate.

[0030] According to this aspect, the amount of emitted illumination light is controlled based on the pixel values ​​of the ink application area in the read data, so that read data is obtained in which the values ​​of the read data of the printed image are small and dark areas are not crushed.

[0031] A reading device according to a twelfth aspect is a reading device according to any one of the first to eleventh aspects, wherein one or more first processors may adjust the amount of light emitted from the transillumination device so that, when the transillumination device is turned on, the minimum pixel value in the read data generated by reading a printed image using an image sensor is greater than the pixel value of the read data corresponding to the dark current of the image sensor.

[0032] According to this aspect, it is possible to reduce the influence of noise in the read data caused by the dark current of the image sensor.

[0033] A reading device according to a thirteenth aspect is a reading device according to any one of the first to twelfth aspects, wherein the transmitted illumination condition setting unit determines two or more combinations of illumination conditions of the transmitted bright-field illumination device and illumination conditions of the transmitted dark-field illumination device, and may set the combination of illumination conditions of the transmitted bright-field illumination device and illumination conditions of the transmitted dark-field illumination device according to the reading conditions of the image sensor.

[0034] In this aspect, a combination of the illumination conditions of the transmitted light bright-field illumination device and the illumination conditions of the transmitted light dark-field illumination device may be stored.

[0035] A reading device according to a fourteenth aspect is a reading device according to any one of the first to thirteenth aspects, wherein the transmitted illumination condition setting unit sets a first transmitted illumination condition and a second transmitted illumination condition different from the first transmitted illumination condition for reading one printed image, one or more processors switch between the first transmitted illumination condition and the second transmitted illumination condition for reading one printed image, and the image sensor generates first reading data to which the first transmitted illumination condition is applied, and generates second reading data to which the second transmitted illumination condition is applied.

[0036] According to this aspect, one printed image can be read once to generate read data for each of a plurality of different illumination conditions.

[0037] A reading method according to a fifteenth aspect of the present disclosure is a reading method applicable to a reading device that includes an image sensor that reads a printed image printed on a substrate and generates read data of the printed image, an imaging lens that forms an optical image of the printed image on the image sensor and defines a field of view that represents the range in which an illumination device that directly incidents illumination light is positioned, and a transmitted illumination device that is positioned opposite the light receiving surface of the image sensor and is equipped with a transmitted brightfield illumination device that is positioned within the field of view of the imaging lens and a transmitted darkfield illumination device that is positioned outside the field of view of the imaging lens, wherein the reading method sets transmitted brightfield illumination conditions to be applied to the transmitted brightfield illumination device and sets transmitted darkfield illumination conditions to be applied to the transmitted darkfield illumination device according to processing to be performed on the read data, emits transmitted brightfield illumination light from the transmitted brightfield illumination device according to the transmitted brightfield illumination conditions, emits transmitted darkfield illumination light from the transmitted darkfield illumination device according to the transmitted darkfield illumination conditions, and reads the printed image using the image sensor.

[0038] According to the reading method according to the fifteenth aspect of the present disclosure, it is possible to obtain the same effects as the reading device according to the first aspect of the present disclosure. The constituent elements of the reading devices according to the second to fourteenth aspects can be applied to the constituent elements of the reading methods according to the other aspects.

[0039] A program according to a sixteenth aspect of the present disclosure is a program applicable to a reading device that includes an image sensor that reads a printed image printed on a substrate and generates read data of the printed image, an imaging lens that forms an optical image of the printed image on the image sensor and defines a field of view that represents the range in which an illumination device that directly incidents illumination light is positioned, and a transmitted illumination device that is positioned opposite the light receiving surface of the image sensor and is equipped with a transmitted brightfield illumination device that is positioned within the field of view of the imaging lens and a transmitted darkfield illumination device that is positioned outside the field of view of the imaging lens, and the program enables a computer to realize the functions of setting transmitted brightfield illumination conditions to be applied to the transmitted brightfield illumination device and setting transmitted darkfield illumination conditions to be applied to the transmitted darkfield illumination device in accordance with processing to be performed on the read data, emitting transmitted brightfield illumination light from the transmitted brightfield illumination device in accordance with the transmitted brightfield illumination conditions, emitting transmitted darkfield illumination light from the transmitted darkfield illumination device in accordance with the transmitted darkfield illumination conditions, and reading the printed image using the image sensor.

[0040] According to the program of the sixteenth aspect of the present disclosure, it is possible to obtain the same effects as the reading device of the first aspect of the present disclosure. The constituent elements of the reading device of the second to fourteenth aspects can be applied to the constituent elements of the program of the other aspects.

[0041] An inspection device according to a seventeenth aspect of the present disclosure is an inspection device comprising: a reading device that reads a printed image printed on a substrate and generates read data of the printed image; and an analyzing device that analyzes the read data, wherein the reading device comprises an image sensor; an imaging lens that forms an optical image of the printed image on the image sensor, the imaging lens defining a field of view that represents the range in which an illumination device that directly incidents illumination light is positioned; a transmitted illumination device that is positioned opposite the light receiving surface of the image sensor and includes a transmitted bright-field illumination device that is positioned within the field of view of the imaging lens and a transmitted dark-field illumination device that is positioned outside the field of view of the imaging lens; a transmitted illumination condition setting unit that sets the transmitted illumination conditions to be applied to the transmitted illumination device; and one or more first processors, wherein the transmitted illumination condition setting unit sets the transmitted bright-field illumination conditions to be applied to the transmitted bright-field illumination device and sets the transmitted dark-field illumination conditions to be applied to the transmitted dark-field illumination device in accordance with the processing performed on the read data, and the one or more first processors control each of the transmitted bright-field illumination device and the transmitted dark-field illumination device in accordance with the transmitted illumination conditions set using the transmitted illumination condition setting unit.

[0042] According to the inspection device according to the seventeenth aspect of the present disclosure, it is possible to obtain the same effects as the reading device according to the first aspect of the present disclosure. The constituent elements of the reading devices according to the second to fourteenth aspects can be applied to the constituent elements of the inspection devices according to the other aspects.

[0043] An inspection device according to an 18th aspect is the inspection device of the 17th aspect, wherein the transmitted illumination condition setting unit determines two or more combinations of illumination conditions of the transmitted bright-field illumination device and illumination conditions of the transmitted dark-field illumination device, and sets the combination of illumination conditions of the transmitted bright-field illumination device and illumination conditions of the transmitted dark-field illumination device according to the reading conditions of the image sensor, and the analysis device may, when performing one type of analysis processing, analyze multiple read data generated by applying multiple different illumination conditions.

[0044] According to this aspect, illumination control suited to the reading conditions of the image sensor can be realized, and by using read data under different illumination conditions, analysis processing can be performed with high accuracy.

[0045] The inspection device of the 19th aspect is the inspection device of the 17th aspect, wherein the transmitted illumination condition setting unit sets a first transmitted illumination condition and a second transmitted illumination condition different from the first transmitted illumination condition for reading one printed image, one or more processors switch between the first transmitted illumination condition and the second transmitted illumination condition for reading one printed image, the image sensor generates first read data to which the first transmitted illumination condition is applied and generates second read data to which the second transmitted illumination condition is applied, and the analysis device may analyze the same number of read data as the number of multiple illumination conditions when performing one type of analysis processing.

[0046] According to this aspect, one printed image is read once, and the same number of read data as the number of lighting conditions is generated, and the same number of analyses as the number of read data can be performed for one type of analysis data.

[0047] An inspection device according to a twentieth aspect is the inspection device of the nineteenth aspect, wherein the analysis device may perform a magnification change process on the read data in the transport direction of the substrate.

[0048] According to this aspect, it is possible to match the resolution of the plurality of read data to the resolution of the image sensor.

[0049] An inspection apparatus according to a 21st aspect is an inspection apparatus according to any one of the 17th to 20th aspects, wherein the transmission dark field illumination device comprises a first transmission dark field illumination device that emits illumination light in a first direction and a second transmission dark field illumination device that emits illumination light in a second direction different from the first direction, the transmission illumination condition setting unit sets a first transmission dark field illumination condition in which either the first transmission dark field illumination device or the second transmission dark field illumination device is turned on, or a second transmission dark field illumination condition in which both the first transmission dark field illumination device and the second transmission dark field illumination device are turned on, and the analysis device may analyze the read data to detect defects in the printed image.

[0050] According to this aspect, defects in a printed image can be detected in a preferable manner.

[0051] An inspection apparatus according to a 22nd aspect is the inspection apparatus of any one of the 17th to 21st aspects, wherein the reflective illumination device is arranged on the same side as the image sensor with respect to a space divided in two by a plane perpendicular to the optical axis of the imaging lens at the reading position of the image sensor, and comprises: a reflective illumination device that irradiates illumination light onto a substrate supported at the reading position; a reflective illumination condition setting unit that sets reflective illumination conditions to be applied to the reflective illumination device; and one or more second processors that control the reflective illumination device in accordance with the reflective illumination conditions, wherein the reflective illumination device comprises a first reflective illumination device that emits illumination light in a third direction and a second reflective illumination device that emits illumination light in a fourth direction different from the third direction, and the reflective illumination condition setting unit sets a first reflective illumination condition that turns on either the first reflective illumination device or the second reflective illumination device, or a second reflective illumination condition that turns on both the first reflective illumination device and the second reflective illumination device, and the analysis device may analyze the read data to detect defects in the printed image.

[0052] According to this aspect, defects in a printed image can be detected in a preferable manner.

[0053] An inspection device according to a 23rd aspect is an inspection device according to any one of the 17th to 22nd aspects, wherein one or more first processors adjust the amount of light emitted by the transmitted dark field illumination device so that the maximum pixel value in the read data of an ink-applied area on a transparent substrate, where the amount of ink per unit area is equal to or less than a specified amount, exceeds the pixel value of a non-ink-applied area on the substrate, and the analysis device analyzes the read data to detect defects in the printed image.

[0054] According to this aspect, defects in a printed image can be detected in a preferable manner.

[0055] A printing system according to a twenty-fourth aspect of the present disclosure comprises a printing device and a reading device that reads a printed image printed on a substrate using the printing device, wherein the reading device comprises an image sensor that reads the printed image and generates read data of the printed image, an imaging lens that forms an optical image of the printed image on the image sensor, the imaging lens defining a field of view that represents the range in which an illumination device that directly incidents illumination light is positioned, a transmitted illumination device that is positioned opposite the light receiving surface of the image sensor and includes a transmitted brightfield illumination device that is positioned within the field of view of the imaging lens and a transmitted darkfield illumination device that is positioned outside the field of view of the imaging lens, a transmitted illumination condition setting unit that sets the transmitted illumination conditions to be applied to the transmitted illumination device, and one or more first processors, wherein the transmitted illumination condition setting unit sets the transmitted brightfield illumination conditions to be applied to the transmitted brightfield illumination device and sets the transmitted darkfield illumination conditions to be applied to the transmitted darkfield illumination device in accordance with processing performed on the read data, and the one or more first processors control each of the transmitted brightfield illumination device and the transmitted darkfield illumination device in accordance with the transmitted illumination conditions set using the transmitted illumination condition setting unit.

[0056] The printing system according to the twenty-fourth aspect of the present disclosure can achieve the same effects as the reading device according to the first aspect of the present disclosure. The components of the reading device according to the second to fourteenth aspects can be applied to the components of the printing systems according to the other aspects.

[0057] A reading device according to a twenty-fifth aspect of the present disclosure includes an image sensor that reads a printed image printed on a substrate and generates read data of the printed image, an imaging lens that forms an optical image of the printed image on the image sensor, the imaging lens defining a field of view that represents a range in which an illumination device that directly incidents illumination light is disposed, a transmitted illumination device disposed in a position opposite the light receiving surface of the image sensor, a light diffusing member, and a switching member that switches between a proportion of the emitted light that is incident on the light diffusing member and emitted from within the field of view of the imaging lens, and a proportion of the emitted light that is not incident on the light diffusing member and emitted from outside the field of view of the imaging lens. a transmitted illumination condition setting unit that sets transmitted illumination conditions to be applied to the transmitted illumination device, and one or more first processors, wherein the transmitted illumination condition setting unit sets transmitted bright-field illumination conditions to be applied to transmitted bright-field illumination light emitted from within the field of view of the imaging lens, and sets transmitted dark-field illumination conditions to be applied to transmitted dark-field illumination light emitted from outside the field of view of the imaging lens, in accordance with the processing to be performed on the read data, and the one or more first processors control each of the transmitted bright-field illumination light and the transmitted dark-field illumination light in accordance with the transmitted illumination conditions set using the transmitted illumination condition setting unit.

[0058] The reading device according to the 25th aspect of the present disclosure can achieve the same effects as the reading device according to the 1st aspect. The constituent elements of the reading devices according to the 2nd to 14th aspects can be applied to the constituent elements of the reading devices according to the other aspects.

[0059] According to the present invention, the brightfield and darkfield transmission illumination devices are controlled in accordance with the processing performed on the scanned data of the printed image, thereby obtaining scanned data of the printed image that is suitable for processing such as inspection in which the scanned data of the printed image is used.

[0060] FIG. 1 is a schematic diagram of a printed matter using non-transparent printing paper, viewed from a direction parallel to the paper surface. FIG. 2 is a schematic diagram of a printed matter using a transparent film substrate, viewed from a direction parallel to the substrate surface. FIG. 3 is a schematic diagram of a printed matter using a white background to read the printed matter using the transparent film substrate shown in FIG. 2. FIG. 4 is a schematic diagram of a printed matter using a non-printed surface NPF as the observation side, viewed from a direction parallel to the printed surface PF. FIG. 5 is a schematic diagram of a printed matter using a printed surface PF as the observation side, viewed from a direction parallel to the printed surface PF. FIG. 6 is a schematic diagram of a printed image using transmitted illumination, viewed from a direction parallel to the printed surface PF, using a transparent film substrate. FIG. 7 is a schematic diagram of a transmitted illumination device with relatively high light diffusion properties. FIG. 8 is a schematic diagram of a transmitted illumination device with relatively low light diffusion properties. FIG. 9 is a perspective view showing the overall configuration of a printing system according to an embodiment. FIG. 10 is a view of the printing system shown in FIG. 9, viewed from the substrate width direction. FIG. 11 is a functional block diagram showing the electrical configuration of the printing system shown in FIGS. 9 and 10. FIG. 12 is a functional block diagram showing the electrical configuration of the reading control unit shown in FIG. 11. FIG. 13 is a block diagram showing an example of the hardware configuration of the electrical configuration of the printing system shown in FIG. 9. FIG. 14 is a flowchart showing the procedure of the reading method according to the embodiment. FIG. 15 is a table showing an example of use of the illumination device. FIG. 16 is an explanatory diagram of an application example of the embodiment. FIG. 17 is a schematic diagram of an illumination device according to an application example.

[0061] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In this specification, the same components are designated by the same reference numerals, and redundant explanations will be omitted where appropriate.

[0062] [Problem Description] In industrial inkjet printing systems that print on transparent film substrates for flexible packaging used in food packaging, etc., it is necessary to measure the ejection direction accuracy of each nozzle, correct density unevenness, and inspect the printed material for defects such as streaks in order to maintain the quality of the printed material. Examples of film substrates include biaxially oriented polypropylene, unoriented polypropylene, linear low-density polyethylene, polyethylene terephthalate, and nylon. The printed material refers to the substrate on which a product image is printed. Margins and other white space used in the manufacturing process are removed from the printed material that will become a product.

[0063] Biaxially oriented polypropylene can be represented by OPP, an abbreviation for Oriented Polypropylene. Unoriented polypropylene can be represented by CPP, an abbreviation for Cast Polypropylene. Linear low density polyethylene can be represented by LLDPE, an abbreviation for Linear Low Density Polyethylene. Polyethylene terephthalate can be represented by PET, an abbreviation for PolyEthylene Terephthalate. Nylon can be represented by Nylon.

[0064] In a printing system that prints on printing paper such as non-transparent coated printing paper, the above-mentioned measurement of the ejection direction accuracy for each nozzle is performed by optically reading the printed material using an inline scanner and then analyzing the read data using image processing technology.

[0065] On the other hand, when a printed material having a transparent film substrate is read using a scanner equipped with an imaging element such as an image sensor, the following problems arise.

[0066] [Non-printed areas are visible] Figure 1 is a schematic diagram of reading a printed matter printed on non-transparent printing paper, viewed from a direction parallel to the paper surface. The figure shows, enlarged to the extent that individual ink droplets are visible, the state in which multiple ink droplets are ejected onto the print image IMG printed on non-transparent printing paper NTP and adhere to the paper surface in raised shapes. It also shows the state in which the multiple ink droplets are irradiated with reflected illumination light RL. The symbol OA represents the optical axis of the imaging lens provided in the reading device. The same applies to the symbol OA shown in Figure 2 and other figures. For example, non-transparent printing paper may be paper with a light transmittance of less than 50 percent. The symbol PF represents the printed surface, and the symbol NPF represents the non-printed surface.

[0067] 2 is a schematic diagram of reading a printed matter using a transparent film substrate, viewed from a direction parallel to the substrate surface. The figure shows, enlarged to a level where individual ink droplets are visible, the state in which the ink droplets are ejected onto the printed image IMG printed on the transparent film substrate SU and rise up and adhere to the substrate surface. The figure also shows a schematic diagram of the state in which the ink droplets are irradiated with reflected illumination light RL. For example, the transparent film substrate SU may be made of a material with a light transmittance of 50 percent or more.

[0068] Here, the print image IMG represents the area on the printing paper NTP shown in FIG. 1 and the substrate SU shown in FIG. 2 where the product image is printed. The print image IMG is primarily composed of ink-application areas PP where ink is present. The print image IMG may also include non-ink-application areas NPP where ink is not present. The non-ink-application areas NPP represent areas where ink is not present on the substrate SU, etc., and non-ink-application areas NPP may also exist outside the area on the substrate SU, etc. where the product image is printed. Hereinafter, the term substrate SU refers to a medium applied for printing, including the printing paper NTP shown in FIG. 1.

[0069] When printing is performed on the printing paper NTP shown in Figure 1, the printed image IMG can be read using the base color of the printing paper NTP as the background, but in the non-ink application area NPP where no ink is present in the printed image IMG printed on the transparent substrate SU shown in Figure 2, objects in the background of the substrate SU are visible and can be read.

[0070] That is, when reading in which the transparent substrate SU is irradiated with reflected illumination light RL from the observation side, an object located on the non-printed surface NPF side of the substrate SU is read as background. When reading in which the transparent substrate SU is irradiated with reflected illumination light RL from the observation side, it is preferable to place an object on the non-printed surface NPF side of the substrate SU that does not interfere with the analysis of the print image IMG.

[0071] 3 is a schematic diagram of a printed matter reading process using a white background for reading a printed matter using the transparent film substrate shown in FIG. The figure shows a state in which a white background WB is placed on the non-printed surface NPF of the transparent substrate SU, and a printed image IMG illuminated with reflected illumination light RL is read. The white background WB shown in the figure is formed by a roller whose outer periphery is painted white. When reading the printed image IMG, the white background WB is placed in contact with the non-printed surface NPF of the substrate SU, and reflected illumination light RL is illuminated from the observation side.

[0072] The printed image IMG shown in Figure 3 is separated from the white background WB by the thickness of the substrate SU, so when reflected illumination light RL is irradiated from a direction that is not parallel to the optical axis OA of the imaging lens, the shadow SH of the printed image IMG printed on the printing surface PF of the substrate SU appears on the white background WB, creating the problem that the shadow SH of the printed image IMG is reflected in the read data.

[0073] [Reading White Ink] In printed materials using a transparent film substrate SU for flexible packaging, a background is printed using white ink depending on the application. Furthermore, when an image such as text contains white portions, printing is performed using white ink. That is, when printing on the transparent substrate SU, white ink is used in the same way as black ink, cyan ink, magenta ink, yellow ink, etc.

[0074] When printing using white ink, it is necessary to perform the above-mentioned measurement of the ejection direction accuracy for each nozzle for the white ink as well. On the other hand, when measuring the ejection direction accuracy for each nozzle, it is necessary to read the ink color to have a contrast with the background color.

[0075] When printing on white printing paper, the white background of the printing paper can be used as a background to create contrast between the color inks, such as black, cyan, magenta, and yellow. However, when printing on a material that uses white ink in addition to color inks, the same white color as the white ink cannot be used as the background color.

[0076] In other words, when measuring the ejection direction accuracy of each nozzle, a background color that can be distinguished from the color of the ink being used is required, but due to the use of white ink, it is difficult to read printed material that uses white ink and colored inks other than white with an appropriate contrast between the background color and the background color using only one type of background color, such as white.The reasons for this are as follows.

[0077] First, the colors cyan, magenta, and yellow used in printing are the three primary colors. ＊ a ＊ b ＊ When each color is displayed in the color space of the color system, the colors are located at positions separated from each other. ＊ a ＊ b ＊ In the color space of the color system, a ＊ and b ＊ is around 0, and black ink is L ＊ is around 0, and the white ink is L ＊ is around 100.

[0078] That is, cyan ink, magenta ink, yellow ink, black ink, and white ink are ＊ a ＊ b ＊ If colors that are located far apart in the color space of the color system and far away from any of the colors mentioned above are selected as background colors, the colors will be relatively close to the mid-density colors of these inks, so the contrast with the mid-density colors will be small and it will not be possible to read with appropriate contrast between them and the background color.

[0079] [Observation of the Non-Printed Surface] For printed materials using printing paper, the printed surface PF is the observation side on which the printed material is observed. For printed materials using the transparent substrate SU shown in FIG. 2, the printed surface PF may be the observation side, or the non-printed surface NPF may be the observation side. Whether the printed surface PF or the non-printed surface NPF is the observation side is determined depending on the intended use of the printed material, etc. When reading printed materials in which both the printed surface PF and the non-printed surface NPF may be the observation side, it is preferable to read each side using a scanner positioned on the printed surface PF side of the printed material and a scanner positioned on the non-printed surface NPF side, particularly when reflected illumination light RL is used. The reason for this is as follows.

[0080] FIG. 4 is a schematic diagram of a printed matter, with the non-printed surface NPF being the observation side, viewed from a direction parallel to the printed surface PF. The figure shows ink droplets of color ink CI and white ink WI ejected onto the printed surface PF, rising up and adhering to the printed surface PF, enlarged to the extent that individual ink droplets of color ink CI are visible. The printed image IMG shown in the figure has a background of highly opaque white ink WI printed on the top layer of the printed surface PF, and the color inks CI other than the white ink WI are obscured by the white ink WI background. Therefore, even if reflected illumination light RL is irradiated onto the printed image IMG from the printed surface PF and an attempt is made to read the image from the printed surface PF, it would be difficult to read the color inks CI obscured by the white ink WI from the printed surface PF side. Therefore, it is necessary to irradiate the printed image IMG with reflected illumination light RL from the non-printed surface NPF side and read the image from the observation side.

[0081] FIG. 5 is a schematic diagram of a printed matter, with the printed surface PF being the observation side, viewed from a direction parallel to the printed surface PF. The figure shows ink droplets of color ink CI ejected onto the printed surface PF, rising up and adhering to the printed surface PF, enlarged to the extent that individual ink droplets are visible. The printed image IMG shown in the figure has a background of white ink WI printed at the bottom, with the color ink CI printed on top of the background. Even if reflected illumination light RL were irradiated onto the printed image IMG from the non-printed surface NPF side and an attempt was made to read the image from the non-printed surface NPF, it would be difficult to read the color ink CI overlaid on the white ink WI from the non-printed surface NPF side. Therefore, it is necessary to irradiate the printed surface PF with reflected illumination light RL and read the image from the observation side.

[0082] Therefore, if a scanner is provided on both the printed surface PF side and the non-printed surface NPF side of the printed matter, it is possible to read from both the printed surface side and the non-printed surface side, but this is not desirable as the cost of the components related to the scanner doubles compared to when the scanner is provided on either the printed surface side or the non-printed surface side of the printed matter.

[0083] [Solution to the above-mentioned problems when using transmitted illumination] To address the above-mentioned problems, we attempted to read a printed image using only transmitted illumination. FIG. 6 is a schematic diagram of the reading of a printed image using transmitted illumination, viewed from a direction parallel to the printing surface PF, of a printed image using a transparent film substrate. The figure shows ink droplets ejected onto the printing surface PF, rising and adhering to the printing surface PF, enlarged to a level where individual ink droplets can be seen. The figure also shows the state in which transmitted illumination light TLL is irradiated onto the non-printing surface NPF of a transparent substrate SU used in a printed matter from a transmitted illumination device TL disposed on the non-printing surface NPF side of the substrate SU. The solid arrow in the figure represents the transmitted illumination light TLL irradiated from the transmitted illumination device TL onto the substrate SU, and the dashed arrow represents the transmitted illumination light TLL transmitted through the substrate SU.

[0084] A scanner is disposed on the printing surface PF side of the substrate SU. The scanner receives transmitted illumination light TLL that has passed through the substrate SU and generates read data of the print image IMG. Note that the scanner is not shown in FIG. 6.

[0085] When reading the printed image IMG shown in Figure 6, the ink-applied area PP is transmitted by the transmitted illumination light TLL according to the transmittance of the substrate SU and the transmittance of the ink, and is read as darker than the non-ink-applied area NPP to the extent that the ink blocks the transmitted illumination light TLL. In the read data, the non-ink-applied area NPP is the brightest, and the non-ink-applied area NPP forms the background corresponding to the base of the printing paper. Furthermore, because the transmitted illumination light TLL is transmitted through the substrate SU and emitted from the ink-applied area PP of the substrate SU, which forms the background, the shadow of the ink on the printing surface PF does not appear. In other words, the problem of the non-ink-applied area NPP being see-through has been solved.

[0086] Consider the issue of reading the white ink WI. The ink-applied area PP is read as darker than the non-ink-applied area NPP because the transmitted illumination light TLL passes through it in accordance with the transmittance of the substrate SU and the transmittance of the ink. Similar to the color inks CI, the white ink WI is also transmitted by illumination light in accordance with the transmittance of the ink, making it possible to read the printed image IMG in which the white ink WI is used.

[0087] Consider the issue of observing the non-printed surface NPF. When transmitted illumination light TLL is used, the white ink WI and color inks CI can be read regardless of the order of printing on the transparent substrate SU. In many parts of the printed image IMG, where various colors are used, two or three ink colors are overlapped in the same position, or some of the ink dots of two or three colors are overlapped.

[0088] When the overlapping ink portion is read by irradiating the image with reflected illumination light RL from the observation side using a scanner, the ink dots on the lower side as viewed from the observation side are hidden to some extent due to the concealing properties of the ink. In contrast, when the overlapping ink portion is read by irradiating the image with transmitted illumination light TLL from the opposite side of the observation side, the ink dots on the lower side as viewed from the observation side are read more clearly than when reflected illumination light RL is used.

[0089] When reading the printed image IMG using the transmitted illumination light TLL, the printed image IMG is read as an image in which multiple ink dots are superimposed, but image defects in the printed matter such as streaks can be detected because ink dots for each ink are missing or the position of the ink dots for each ink is misaligned.

[0090] Consider the brightness of the ink-applied areas PP and the brightness of the non-ink-applied areas NPP in the scanned data of the printed image IMG when transmitted illumination light TLL is used. If the pixel values ​​of the non-ink-applied areas NPP are set to the same as when reflected illumination light RL is used, the pixel values ​​of the ink-applied areas PP will be darker than when reflected illumination light RL is used. This results in a problem where the signal-to-noise ratio of the ink-applied areas PP in the scanned data decreases, and the density resolution in high-density areas decreases.

[0091] For example, 8-bit data expressed as integers between 0 and 255 is applied as the pixel values ​​of the pixels that make up the print image IMG, with the darkest pixel value being 0 and the brightest pixel value being 255. When the pixel value of the non-ink-application region NPP is set to 230, the pixel value of the ink-application region PP when transmitted illumination light TLL is used is between half and one-third of the pixel value of the ink-application region PP when reflected illumination light RL is used. Specifically, if the pixel value of the ink-application region PP when reflected illumination light RL is used is 3, the pixel value of the ink-application region PP when transmitted illumination light TLL is used is 1.

[0092] The following describes in detail an illumination device suitable for reading a printed image IMG printed on a transparent film substrate SU using an inkjet method. The illumination device described below can adjust the brightness of the ink-applied area PP and the brightness of the non-ink-applied area NPP to an appropriate relationship, thereby obtaining brightness suitable for processing such as analysis of the read data, a good signal-to-noise ratio, and the required density resolution in the dark, high-density area.

[0093] [Example of configuration of transmitted illumination device] In order to solve the above-mentioned problems, the light diffusion property of the transmitted illumination device TL was changed and the printed image IMG on the transparent substrate SU was read using the transmitted illumination light TLL. As a result, it was found that the relationship in brightness between the ink-applied area PP and the non-ink-applied area NPP changes due to the difference in the light diffusion property of the transmitted illumination light TLL.

[0094] Specifically, when transmitted illumination light TLL with relatively high light diffusion, such as illumination light close to perfect diffusion, is used, the ink-applied area PP is read brighter at the relative brightness ratio between the non-ink-applied area NPP and the ink-applied area PP, compared to when transmitted illumination light TLL with relatively low light diffusion is used. This makes it possible to relatively increase the signal-to-noise ratio in the read data, and to relatively increase the density resolution of high-density areas. Perfect diffusion refers to a state in which the brightness of the illumination light appears uniform from any direction. Light diffusion can be measured as the ratio between the light intensity in the normal direction at an angle of 90° to the light exit surface and the light intensity in the direction at an angle of θ° to the normal to the light exit surface. In other words, perfect diffusion is when the light intensity in the normal direction at an angle of 90° to the light exit surface is measured as I ０ The intensity I(θ) of light in the direction at an angle of θ° with respect to the normal to the light exit surface is I(θ)=I ０ × cos(θ).

[0095] Fig. 7 is a schematic diagram of a transmitted illumination device with relatively high light diffusion. Fig. 8 is a schematic diagram of a transmitted illumination device with relatively low light diffusion. The light diffusion member LDP provided in the transmitted illumination device TL shown in Fig. 7 has relatively high light diffusion compared to the light diffusion member LDP provided in the transmitted illumination device TL shown in Fig. 8. In Figs. 7 and 8, the degree of light diffusion is expressed using the length of the arrows of the transmitted illumination light TLL and the shape of the ellipse passing through the base and tip of each arrow. An elongated ellipse indicates high directionality of the transmitted illumination light and low light diffusion, while an ellipse closer to a circle indicates light diffusion that is close to complete diffusion.

[0096] The light source LS provided in the transillumination device TL shown in Fig. 7 is equivalent to the light source LS provided in the transillumination device TL shown in Fig. 8. In other words, the light diffusibility of the transillumination device TL depends on the light diffusibility of the light diffusing member LDP.

[0097] However, even when reading a printed image IMG using transmitted illumination light that is nearly completely diffused, in order to obtain the full effect of diffused light, it is necessary to bring the light diffusion member LDP close enough to be in contact with the substrate SU. If it is not possible to bring the light diffusion member LDP close to the substrate SU, the area of ​​the exit surface of the light diffusion member LDF is relatively increased so that light that is more nearly parallel to the substrate SU reaches the optical axis OA.

[0098] In the method of bringing the light diffusing member LDP closer to the substrate SU, the light diffusing member LDP may come into contact with the substrate SU, causing concerns about scratching the substrate SU and malfunctioning of the transmitted illumination device TL. On the other hand, in the method of relatively increasing the area of ​​the exit surface of the light diffusing member LDF, the transport member that supports and transports the substrate SU may need to be repositioned so as not to interfere with the light diffusing member LDF. Furthermore, in this method, there is a concern about a decrease in the amount of emitted transmitted illumination light TLL from the light diffusing member LDF, which may necessitate an increase in the amount of light emitted by the light source LS. These measures may affect the performance and cost of the transmitted illumination device TL.

[0099] Furthermore, when reading a printed image IMG using nearly completely diffused transmitted illumination light, there is a problem in that the utilization efficiency of the transmitted illumination light TLL is relatively low, especially when a scanner equipped with a line sensor is used. Furthermore, when reading a printed image IMG that contains streaks, using transmitted illumination light TLL with lower light diffusion than nearly completely diffused transmitted illumination light results in a clearer contrast between the streaks and the printed image IMG, thereby improving the performance of detecting the presence or absence of streaks. However, when determining the intensity of streaks rather than the presence or absence of streaks, high density resolution is effective for determining subtle differences in density in the streak image, and using nearly completely diffused transmitted illumination light can improve the performance of determining streak intensity. Overall, using nearly completely diffused transmitted illumination light is effective in detecting streaks.

[0100] In summary, it has been found that when reading a printed image IMG using a transmitted illumination device TL, there is a light diffusion characteristic that is suitable for each process in which the read data is used. Specifically, it is advisable to read the image so that the ink-applied areas PP are not too dark compared to the non-ink-applied areas NPP, and to obtain read data with a relatively high signal-to-noise ratio and relatively high density resolution by setting the light diffusion characteristic relatively high. Read data with a relatively high light diffusion characteristic is suitable for correcting print irregularities and detecting streak defects.

[0101] On the other hand, if it is desired to obtain a dark, clear contrast between the ink-applied areas PP and the non-ink-applied areas NPP, it is advisable to set the light diffusion property relatively low. The read data obtained when the light diffusion property is relatively low is suitable for measuring the nozzle ejection direction accuracy. Below, a reading device equipped with a transmitted illumination device TL having different light diffusion properties and a printing system equipped with the reading device will be described in detail.

[0102] [Overall configuration of printing system according to embodiment] Fig. 9 is a perspective view showing a schematic configuration of a printing system according to an embodiment. Fig. 10 is a view of the printing system shown in Fig. 9 as seen from the substrate width direction. The printing system 10 will be described below with appropriate reference to Figs. 9 and 10.

[0103] Here, the substrate transport direction is the direction in which the substrate SU travels in the printing system 10. The upstream side of the substrate transport direction represents the supply side of the substrate SU in the substrate transport direction. The downstream side of the substrate transport direction represents the recovery side of the substrate SU in the substrate transport direction. The substrate width direction is a direction perpendicular to the substrate transport direction and parallel to the transport surface of the substrate SU. The arrows shown in Figures 9 and 10 represent the substrate transport direction.

[0104] 9 includes a transport device 12, a printing device 20, a reading device 30, and a fixing device 60. In addition, as shown in FIG.

[0105] The printing system 10 prints an image on a continuous substrate SU that is transported using a roll-to-roll transport device 12. The substrate SU shown in FIGS. 9 and 10 is a transparent film. The transport device 12 pulls out the substrate SU from a supply roll 14 on which the substrate SU is wound in a roll before printing, supports the non-printing surface NPF of the substrate SU using multiple support rollers 16, and transports the substrate SU along the substrate transport direction. The transported substrate SU is taken up onto a recovery roll 18. Note that the arrow on the supply roll 14 indicates the rotation direction of the supply roll 14 when the substrate SU is transported. Also, the arrow on the recovery roll 18 indicates the rotation direction of the recovery roll 18 when the substrate SU is transported.

[0106] The transport device 12 includes a tension roller that applies a specified tension to the substrate SU, a dancer roller that suppresses fluctuations in the tension applied to the substrate SU, and a tension pickup that detects the tension applied to the substrate SU. Note that the tension roller, dancer roller, and tension pickup are not shown in the drawings.

[0107] The transport device 12 includes a motor M1 that functions as a drive source for the core of the supply roll 14 and a motor M2 that functions as a drive source for the core of the recovery roll 18. The motors M1 and M2 are shown schematically in FIG.

[0108] An encoder E is attached to any one of the plurality of support rollers 16. The encoder E may be attached to the rotation shaft of the motor M1 or may be attached to the rotation shaft of the motor M2.

[0109] The conveying device 12 may be configured to convey a substrate in a sheet form instead of the roll-to-roll system shown in Figures 9 and 10. Any conveying system such as a roller conveying system may be used to convey the substrate in a sheet form.

[0110] The printing device 20 performs printing on the substrate SU that is transported using the transport device 12. That is, the transport device 12 holds the passing position of the substrate SU at a specified position relative to the printing device 20, and maintains a specified transport speed.

[0111] The printing device 20 includes a plurality of inkjet heads corresponding to a plurality of ink colors, each of which may be black, cyan, magenta, and yellow. The printing device 20 may also include an inkjet head that ejects white ink for printing a background onto the transparent substrate SU.

[0112] The printing device 20 may be provided with inkjet heads corresponding to inks of colors such as green, red, pink, purple, and orange, thereby printing color images that reproduce a variety of colors. Note that the inkjet heads are not shown in the drawings.

[0113] The inkjet head may be a line head in which the length of the region in which the nozzles are arranged in the width direction of the substrate corresponds to the entire width of the substrate SU. The line head may be configured in such a way that multiple head modules are arranged along the width direction of the substrate. The inkjet head may be a piezo-jet type or a thermal type.

[0114] The printing device 20 ejects ink of each color from the inkjet head of each color toward the substrate SU based on the print data of the print image, and prints the print image IMG on the printing surface PF of the substrate SU. Ink is supplied from an ink tank to one or more inkjet heads provided in the printing device 20 using an ink supply device 70 shown in FIG.

[0115] Inkjet heads are subjected to maintenance using a maintenance device to maintain their ejection performance. Examples of maintenance for inkjet heads include dummy jetting, purging, and wiping of the nozzle surface.

[0116] The maintenance device includes a wiping device that wipes the nozzle surface of the inkjet head, and a cap that seals the nozzle surface and functions as an ink receiver during dummy jets and purging. The maintenance device is not shown in Figures 9 and 10. The maintenance device is designated by the reference numeral 72 and is shown in Figure 11.

[0117] The reading device 30 reads the print image IMG printed on the substrate SU transported by the transport device 12, and generates read data of the print image IMG. That is, the transport device 12 holds the substrate SU passing at a specified position relative to the reading device 30, and maintains a specified transport speed. The read data of the print image IMG is used to measure the ejection direction accuracy for each nozzle, correct density unevenness, and inspect the printed matter for defects such as streaks.

[0118] The reading device 30 includes an image sensor 32, an imaging lens 34, a reference plate 36, a reflective illumination device 38, a transmitted light bright-field illumination device 40, and a transmitted light dark-field illumination device 42. The image sensor 32 is a color sensor equipped with light-receiving elements corresponding to each of the RGB colors. The image sensor 32 is a line sensor in which multiple light-receiving elements are arranged in a line. Examples of the image sensor 32 include a CMOS image sensor and a CCD image sensor.

[0119] In RGB, R stands for red, G stands for green, and B stands for blue. CMOS is an abbreviation for Complementary Metal Oxide Semiconductor. CCD is an abbreviation for Charge Coupled Device.

[0120] The imaging lens 34 is an optical element that forms an optical image of the print image IMG printed on the substrate SU supported at the reading position of the image sensor 32 onto the light receiving surface of the image sensor 32. The imaging lens 34 may be configured as an imaging lens group including a plurality of lenses. The symbol OA denotes the optical axis of the imaging lens 34.

[0121] The reference plate 36 is a flat plate whose reading surface, which is read by the image sensor 32, is painted white, and is a member that represents the standard for the brightness of white when reading by the image sensor 32. The read data of the reference plate 36 is used when calibrating the image sensor 32.

[0122] The reference plate 36 is supported by a reference plate moving device so as to be movable between a reading position and a standby position. The reading position is a position where the optical axis OA of the imaging lens 34 passes through the reference plate 36. The standby position is a position outside the field of view of the imaging lens 34. M3 shown in FIG. 9 represents a motor provided in the reference plate moving device that movably supports the reference plate 36.

[0123] When calibrating the brightness of the image sensor 32, the reading device 30 irradiates the reference plate 36, which has been moved to the reading position, with reflected illumination light, reads the white color of the reference plate 36 using the image sensor 32, and determines the reference brightness based on the read data. The read data of the reference plate 36 may be applied to shading correction of the image sensor 32.

[0124] The reflective illumination device 38 irradiates the printed surface PF of the substrate SU with reflected illumination light. The reflective illumination device 38 mainly emits reflected illumination light when reading a printed matter to which an opaque substrate such as paper is applied.

[0125] The reflective illumination device 38 shown in Figures 9 and 10 includes a first reflective illumination device 38A arranged upstream in the substrate transport direction relative to the reading position of the substrate SU, and a second reflective illumination device 38B arranged downstream in the same direction. The first reflective illumination device 38A may have a structure in which multiple light source elements are arranged along the substrate width direction. Examples of light source elements include white LED elements. The first reflective illumination device 38A may also be equipped with an optical member such as a light guide plate. The second reflective illumination device 38B may have a structure similar to that of the first reflective illumination device 38A. Note that LED is an abbreviation for Light Emitting Diode.

[0126] The first reflective illuminating device 38A emits illumination light in a third direction. The second reflective illuminating device 38B emits illumination light in a fourth direction different from the third direction. Figures 9 and 10 show an example in which the third direction and the fourth direction intersect. The third direction and the fourth direction may be perpendicular to each other.

[0127] The transmitted illumination device 44, which includes the transmitted brightfield illumination device 40 and the transmitted darkfield illumination device 42, is located on the non-printed surface NPF side of the substrate SU, opposite the printed surface PF, and is positioned opposite the light receiving surface of the image sensor 32. Note that the printed surface PF of the substrate SU described in the embodiment is an example of a plane perpendicular to the optical axis of the imaging lens. Furthermore, the space in which the reflective illumination device 38 and the transmitted illumination device 44 described in the embodiment are arranged is an example of a space divided in two by a plane perpendicular to the optical axis of the imaging lens.

[0128] The transmitted illumination device 44 irradiates the substrate SU with transmitted illumination light when the printed image IMG is read using the image sensor 32. When the printed image IMG of the substrate SU is read using the image sensor 32, the transmitted illumination device 44 and the reflective illumination device 38 may be used in combination.

[0129] The transmitted light bright-field illumination device 40 is disposed at a position through which the optical axis OA of the imaging lens 34 passes. In other words, the transmitted light bright-field illumination device 40 is disposed at a position within the range of the field of view of the imaging lens 34. The field of view of the imaging lens 34 refers to the position of the transmitted light bright-field illumination device 40 at which transmitted illumination light is directly incident on the imaging lens 34.

[0130] For example, the field of view of the imaging lens 34 can be understood as the area inside two imaginary lines L1 and L2 that start from the end of the image sensor 32 shown in Figure 9, pass through the imaging lens 34, and pass through the end of the substrate SU in the substrate width direction.

[0131] The transmitted brightfield illumination device 40 includes a light diffusing member 46. The light diffusing member 46 is disposed on the emission surface of the transmitted illumination light. The transmitted brightfield illumination device 40 causes illumination light emitted from the light source element to be incident on the light diffusing member 46, and irradiates the non-printed surface NPF of the substrate SU with transmitted illumination light having increased uniformity of brightness in a plane parallel to the non-printed surface NPF of the substrate SU. The transmitted brightfield illumination device 40 includes multiple light diffusing members 46 with different light diffusivities, and the light diffusivities can be changed by appropriately changing the light diffusing members 46.

[0132] The transmission dark field illumination device 42 includes a first transmission dark field illumination device 42A disposed upstream in the substrate transport direction relative to the reading position of the substrate SU, and a second transmission dark field illumination device 42B disposed downstream in the same direction. The first transmission dark field illumination device 42A and the second transmission dark field illumination device 42B are disposed outside the field of view of the imaging lens 34. In other words, the first transmission dark field illumination device 42A and the second transmission dark field illumination device 42B are disposed at positions where the transmission dark field illumination light emitted therefrom does not directly enter the imaging lens 34.

[0133] The transmitted light dark field illumination device 42 includes a light diffusing member, similar to the transmitted light bright field illumination device 40. The light diffusing member included in the transmitted light dark field illumination device 42 is not shown in the drawing. The transmitted light dark field illumination device 42 may include a cylindrical lens, and may use the cylindrical lens to focus the illumination light emitted from the light source element onto the reading position of the substrate SU. The transmitted light dark field illumination device 42 may include a light guide, and may use the light guide to focus the illumination light emitted from the light source element onto the reading position of the substrate SU.

[0134] The first transmission dark field illumination device 42A emits illumination light in a first direction. The second transmission dark field illumination device 42B emits illumination light in a second direction different from the first direction. Figures 9 and 10 show an example in which the first direction and the second direction intersect. The first direction and the second direction may be perpendicular to each other.

[0135] The fixing device 60 fixes the print image IMG printed on the substrate SU. That is, the fixing device 60 dries the ink applied to the substrate SU. The fixing device 60 may include a heating device such as a heater and an air blowing device such as a fan.

[0136] [Electrical Configuration of Printing System] Figure 11 is a functional block diagram showing the electrical configuration of the printing system shown in Figures 9 and 10. The printing system 10 includes a control device to which a computer is applied, and the control device executes various programs corresponding to various functions to realize the various functions. Note that the control device is not shown in Figure 11. The control device is illustrated in Figure 13 using the reference numeral 200.

[0137] The computer applied to the control device may be in the form of a server, a personal computer, a workstation, a tablet terminal, etc. The computer may also be in the form of a virtual machine.

[0138] The printing system 10 includes a system control unit 100. The system control unit 100 comprehensively controls the entire printing system 10. That is, the system control unit 100 transmits command signals to various processing units and controls each unit of the printing system 10 via the various processing units.

[0139] The printing system 10 includes a substrate information acquisition unit 120. The substrate information acquisition unit 120 acquires information about the substrate SU used for printing. Examples of the information about the substrate SU include information about whether the substrate SU is transparent or non-transparent, information about the material of the substrate SU, and information about the size of the substrate SU.

[0140] The printing system 10 includes a print data acquisition unit 122. The print data acquisition unit 122 acquires print data transmitted from an external device such as a server, and stores the acquired print data.

[0141] The printing system 10 includes a storage device 130. The storage device 130 stores various programs, various parameters, and various data used in the printing system 10. The storage device 130 stores various data such as substrate information acquired using the substrate information acquisition unit 120 and print data acquired using the print data acquisition unit 122.

[0142] The storage device 130 may include a program storage section in which various programs are stored, a parameter storage section in which various parameters are stored, and a data storage section in which various data are stored.

[0143] The printing system 10 includes a sensor 132. The sensor 132 includes various sensors provided in the printing system 10. Examples of the sensor 132 include a temperature sensor that measures various temperatures, a position detection sensor that detects the position of the substrate SU, and a tension pickup that measures the tension applied to the substrate SU.

[0144] The printing system 10 includes a transport control unit 102. The transport control unit 102 controls the transport device 12 based on a command signal transmitted from the system control unit 100. The transport control unit 102 sets transport conditions for the transport device 12 in accordance with substrate information acquired using the substrate information acquisition unit 120. The term "setting" can include the concept of changing previously set information.

[0145] The conveyance control unit 102 includes a motor driver that controls the operation of the motors M1 and M2 shown in Fig. 1. The motor driver performs feedback control of the motors M1 and M2 based on an encoder signal transmitted from an encoder E. The motor driver is not shown in the figure.

[0146] The transport control unit 102 controls the tension applied to the substrate SU. The transport control unit 102 performs feedback control of the tension applied to the substrate SU based on a detection signal transmitted from the tension pickup.

[0147] The printing system 10 includes a print control unit 104. The print control unit 104 generates a drive voltage to be supplied to an inkjet head provided in the printing device 20, based on print data acquired using a print data acquisition unit 122. Discharge control of the inkjet head is performed based on the drive voltage.

[0148] That is, the print control unit 104 performs various correction processes on the print data, such as color separation, color conversion, halftone processing, and density correction, to generate dot data for each color. The print control unit 104 generates a drive voltage to be supplied to the inkjet head based on the dot data for each color. The print control unit 104 supplies the drive voltage to the inkjet head.

[0149] Furthermore, the print control unit 104 sets the print conditions of the printing device 20 according to the substrate information acquired using the substrate information acquisition unit 120. The print control unit 104 may set the print conditions of the printing device 20 according to the type of ink.

[0150] The printing system 10 includes a fixing control unit 106. The fixing control unit 106 controls the operation of the fixing device 60 in accordance with predetermined fixing conditions based on a command signal transmitted from the system control unit 100. The fixing control unit 106 sets fixing processing conditions for the fixing device 60 in accordance with the substrate information, print data, etc.

[0151] The printing system 10 includes an ink supply control unit 108. The ink supply control unit 108 controls the operation of the ink supply device 70 based on command signals sent from the system control unit 100.

[0152] The printing system 10 includes a maintenance control unit 110. The maintenance control unit 110 controls the operation of the maintenance device 72 based on a command signal sent from the system control unit 100.

[0153] The printing system 10 includes a reading control unit 112 and a reading condition setting unit 124. The reading control unit 112 controls the operation of the reading device 30 based on a command signal transmitted from the system control unit 100. The reading condition setting unit 124 sets reading conditions to be applied to the reading device 30.

[0154] The reading conditions include image sensor conditions such as the reading resolution of the image sensor 32, and illumination conditions such as the light intensity of the illumination device. The illumination conditions include reflective illumination conditions applied to the reflective illumination device 38 and transmitted illumination conditions applied to the transmitted illumination device 44. The transmitted illumination conditions include transmitted bright-field illumination conditions applied to the transmitted bright-field illumination device 40 and transmitted dark-field illumination conditions applied to the transmitted dark-field illumination device 42.

[0155] The reading condition setting unit 124 can set reading conditions by referring to the substrate information acquired using the substrate information acquisition unit 120. Furthermore, the reading condition setting unit 124 can set reading conditions according to the type of the print image IMG to be read.

[0156] For example, for a test image used to measure the ejection direction accuracy of each nozzle of a ladder pattern or the like, reading conditions are set such that the reflective illumination device 38 shown in FIG. 1 is used, and reading conditions are set such that either the first transmitted light dark field illumination device 42A or the second transmitted light dark field illumination device 42B is turned on and the other is turned off.

[0157] The reading condition setting unit 124 may use the type of substrate SU, the printed image IMG to be read, etc. as parameters, and refer to a reading condition storage unit 126 that stores reading conditions for each parameter to set reading conditions to be applied to the reading device 30. Note that the reading condition setting unit 124 described in the embodiment is an example of a transmitted illumination condition setting unit and an example of a reflected illumination condition setting unit.

[0158] The reading control unit 112 can independently control the operation of each of the first reflective illumination device 38A, the second reflective illumination device 38B, the transmitted light bright-field illumination device 40, the first transmitted light dark-field illumination device 42A, and the second transmitted light dark-field illumination device 42B. Note that the term "illumination device" represents a comprehensive concept that includes the above-described first reflective illumination device 38A, etc.

[0159] The printing system 10 includes a read data analysis unit 114. The read data analysis unit 114 analyzes the read data of the print image IMG acquired via the read control unit 112 and stores the analysis results. The analysis results of the read data of the print image IMG are used to measure the ejection direction accuracy for each nozzle, etc.

[0160] The read data analysis unit 114 is set to perform an analysis process according to the print image IMG to be read. For example, for a test image used to measure the ejection direction accuracy for each nozzle of a ladder pattern or the like, a process for measuring the position and width of each pattern is applied.

[0161] The first test image, which is used to correct density unevenness, is subjected to a process of measuring the pixel values ​​of the chart for each density value. The product image, which is subjected to inspection for print defects such as streaks, is subjected to a process of comparing the image data of the product image with the image data of the product image.

[0162] For example, the first test image used for density unevenness correction includes solid images corresponding to at least 10 different density values ​​ranging from low density to high density. The solid images for each density value have a rectangular shape that is long in the substrate width direction and are arranged in order of density value in the substrate transport direction.

[0163] That is, when performing one type of analysis process, the read data analysis unit 114 analyzes the same number of read data as that generated for each of the plurality of illumination conditions. Note that the read data analysis unit 114 described in the embodiment is an example of an analysis device.

[0164] [Configuration Example of Reading Control Unit] Fig. 12 is a functional block diagram showing a configuration example of the reading control unit shown in Fig. 11. The reading control unit 112 includes a reading condition acquisition unit 140. The reading condition acquisition unit 140 acquires reading conditions to be applied to the reading device 30, which are set using the reading condition setting unit 124.

[0165] The reading control unit 112 includes an image sensor control unit 142. The image sensor control unit 142 controls the operation of the image sensor 32 based on the image sensor conditions included in the acquired reading conditions. The control of the image sensor 32 includes setting various parameters generally used to set the operating conditions of the image sensor 32, such as adjusting the amplifier gain for the analog output of the image sensor 32, setting an offset value, setting the reading cycle, and setting the shutter speed, as well as controlling the reading operation of the image sensor 32.

[0166] The reading control unit 112 includes a first reflective illumination control unit 144. The first reflective illumination control unit 144 controls the amount of light emitted from the first reflective illumination device 38A based on the illumination conditions included in the acquired reading conditions.

[0167] The reading control unit 112 includes a second reflective illumination control unit 146. The second reflective illumination control unit 146 controls the amount of light emitted from the second reflective illumination device 38B based on the illumination conditions included in the acquired reading conditions.

[0168] The reading control unit 112 includes a transmitted light bright field illumination control unit 148. The transmitted light bright field illumination control unit 148 controls the amount of light emitted from the transmitted light bright field illumination device 40 based on the illumination conditions included in the acquired reading conditions.

[0169] The reading control unit 112 includes a first transmission dark field illumination control unit 150. The first transmission dark field illumination control unit 150 controls the amount of light emitted from the first transmission dark field illumination device 42A based on the illumination conditions included in the acquired reading conditions.

[0170] The reading control unit 112 includes a second transmitted light dark field illumination control unit 152. The second transmitted light dark field illumination control unit 152 controls the amount of light emitted from the second transmitted light dark field illumination device 42B based on the illumination conditions included in the acquired reading conditions.

[0171] The read control unit 112 includes a read data acquisition unit 154. The read data acquisition unit 154 acquires read data of the print image IMG transmitted from the image sensor 32, converts the analog read data into digital read data, and transmits the digital read data to the read data analysis unit 114. In this embodiment, an example is shown in which analog-to-digital conversion is performed to generate a 12-bit digital signal from an analog signal, and after digital gain adjustment, the most significant 10 bits of the 12-bit data are output as pixel values ​​of the read data for each color.

[0172] [Hardware Configuration of Control Device Applied to Printing System] Fig. 13 is a block diagram showing an example of the hardware configuration of the electrical configuration of the printing device shown in Fig. 11. The control device 200 provided in the printing system 10 includes a processor 202, a computer-readable medium 204 which is a non-transitory tangible entity, a communication interface 206, and an input / output interface 208.

[0173] The processor 202 includes a CPU (Central Processing Unit). The processor 202 may include a GPU (Graphics Processing Unit). The processor 202 is connected to a computer-readable medium 204, a communication interface 206, and an input / output interface 208 via a bus 210. The processor 202 described in the embodiment is an example of a first processor and an example of a second processor.

[0174] The computer-readable medium 204 includes a memory 212 serving as a main storage device and a storage 214 serving as an auxiliary storage device. The computer-readable medium 204 may be a semiconductor memory, a hard disk drive, a solid-state drive, or the like. The computer-readable medium 204 may be any combination of multiple devices. The memory 212 corresponds to a part of the storage device 130 shown in FIG. 11 .

[0175] A hard disk drive may be referred to as an HDD, which is an abbreviation of the English term Hard Disk Drive, and a solid state drive may be referred to as an SSD, which is an abbreviation of the English term Solid State Drive.

[0176] The memory 212 of the computer-readable medium 204 stores a transport control program 220, a print control program 222, a reading control program 224, a read data analysis program 226, a fixing control program 228, and a maintenance control program 230. The memory 212 also stores substrate information 232 and reading conditions 234.

[0177] The transport control program 220 is applied to the transport control unit 102 shown in Fig. 11 and realizes the transport function of the substrate SU using the transport device 12. The print control program 222 is applied to the print control unit 104 and realizes the print function using the printing device 20.

[0178] The reading control program 224 is applied to the reading control unit 112, and refers to the substrate information 232 and the reading conditions 234 to realize the reading function of the print image IMG used by the reading device 30. The read data analysis program 226 is applied to the read data analysis unit 114, and realizes the analysis function of the read data.

[0179] The fixing control program 228 is applied to the fixing control unit 106, and realizes the function of fixing a printed image onto a substrate SU using the fixing device 60. The maintenance control program 230 is applied to the maintenance control unit 110, and realizes the function of maintaining the inkjet head.

[0180] The various programs stored in the computer-readable medium 204 include one or more instructions. The computer-readable medium 204 stores various data, various parameters, and the like.

[0181] In the control device 200, the processor 202 executes various programs stored in a computer-readable medium 204, thereby realizing various functions in the printing system 10. Note that the term "program" is synonymous with the term "software."

[0182] The control device 200 performs data communication with an external device via a communication interface 206. The communication interface 206 may conform to various standards, such as USB (Universal Serial Bus). The communication format of the communication interface 206 may be either wired communication or wireless communication. Note that USB is a registered trademark.

[0183] The control device 200 is connected to an input device 216 and a display 218 via an input / output interface 208. The input device 216 is implemented by input devices such as a keyboard and a mouse. The display 218 displays various information applied to the control device 200.

[0184] The display 218 may be a liquid crystal display, an organic EL display, a projector, or any combination of multiple devices. The EL in the organic EL display is an abbreviation for Electro-Luminescence.

[0185] Examples of the hardware structure of the processor 202 include a CPU, a GPU, a programmable logic device (PLD), and an application specific integrated circuit (ASIC). The CPU is a general-purpose processor that executes programs and functions as various functional units. The GPU is a processor specialized for image processing.

[0186] A PLD is a processor whose electrical circuit configuration can be changed after the device is manufactured. An example of a PLD is an FPGA (Field Programmable Gate Array). An ASIC is a processor with dedicated electrical circuitry designed specifically to perform a specific process.

[0187] A processing unit may be configured with one of these various processors, or may be configured with two or more processors of the same or different types. Examples of combinations of various processors include a combination of one or more FPGAs and one or more CPUs, and a combination of one or more FPGAs and one or more GPUs. Another example of a combination of various processors is a combination of one or more CPUs and one or more GPUs.

[0188] A single processor may be used to configure multiple functional units. An example of using a single processor to configure multiple functional units is a configuration in which a single processor is configured by applying a combination of one or more CPUs and software, such as a SoC (System On a Chip) that is typified by a computer such as a client or server, and this processor operates as multiple functional units.

[0189] Another example of using one processor to configure multiple functional units is to use a processor that uses one IC chip to realize the functions of an entire system including multiple functional units. Note that IC is an abbreviation for Integrated Circuit.

[0190] In this way, the various functional units are configured as hardware structures using one or more of the various processors described above. Furthermore, the hardware structures of the various processors described above are more specifically electric circuits (circuitry) that combine circuit elements such as semiconductor elements.

[0191] The computer-readable medium 204 may include semiconductor devices such as read-only memory (ROM), random access memory (RAM), and SSDs. The computer-readable medium 204 may include magnetic storage media such as hard disks. The computer-readable medium 204 may comprise multiple types of storage media.

[0192] [Procedure of Reading Method According to Embodiment] Fig. 14 is a flowchart showing the procedure of the reading method according to the embodiment. In an adjustment step S10, the reading control unit 112 shown in Fig. 11 adjusts the reading device 30. The adjustment of the reading device 30 includes adjustment of the amount of emitted illumination light, adjustment of the reading timing, adjustment of the reading position, etc., depending on the type of substrate SU on which the print image IMG to be read is printed.

[0193] For example, in the adjustment step S10, when a transparent substrate SU is used, the transmitted light brightfield illumination device 40 shown in FIG. 9 is turned on, and the unprinted substrate SU is read using the image sensor 32. Based on the read data of the substrate SU, the light intensity of the transmitted light brightfield illumination device 40 is adjusted, and the gain of the amplifier that amplifies the output signal of the image sensor 32 is adjusted, thereby adjusting the bright reference value of the output signal of the image sensor 32. Next, the unprinted substrate SU is read using the image sensor 32 without irradiating the substrate SU with illumination light, and the dark reference value of the output signal of the image sensor 32 is adjusted based on the read data. When reading without irradiating the substrate SU with illumination light, the reference plate 36 may be moved to a position where the reading optical axis of the image sensor 32 passes and used as a light shield to block extraneous light. In either method, the brightness of the ambient light at the reading position when adjusting the dark reference value must be sufficiently darker than the brightness of the illumination light at the reading position when adjusting the bright reference value. The sufficiently dark state is a state where the brightness is equal to or less than the brightness corresponding to the least significant bit depending on the number of bits when the output signal of the image sensor 32 is converted into a digital signal. For example, when converted into a 12-bit digital signal, the brightness of the ambient light is 1 / 2 of the brightness of the illumination light at the reading position when adjusting the bright reference value. １２ Preferably, it is equal to or less than half of 0.00024.

[0194] In the adjustment step S10, when a paper substrate SU such as printing paper is used, the reference plate 36 is moved to a position where the reading optical axis of the image sensor 32 passes, the first reflective illuminator 38A and the second reflective illuminator 38B are turned on, the light intensity of the first reflective illuminator 38A and the second reflective illuminator 38B are adjusted, and the gain of the amplifier that amplifies the output signal of the image sensor 32 is adjusted, thereby adjusting the light reference value of the output signal of the image sensor 32 based on the read data of the reference plate 36. Next, the reference plate 36 is read using the image sensor 32 without irradiating the reference plate 36 with illumination light, and the dark reference value of the output signal of the image sensor 32 is adjusted based on the read data of the reference plate 36. After the adjustment of the image sensor 32 and the adjustment of the illumination devices such as the reflective illuminator 38 is completed in the adjustment step S10, the process proceeds to the reading condition setting step S12.

[0195] In the reading condition setting step S12, the reading condition setting unit 124 sets reading conditions according to the type of substrate, etc. For example, in the reading condition setting step S12, the reading resolution of the image sensor 32 is set according to the transport speed of the substrate SU and the print resolution of the printed image IMG to be read, etc. In addition, the lighting device is set to be turned on or off, and the amount of light emitted by the lighting device that is turned on is adjusted according to the type of substrate SU and the type of printed image IMG to be read, etc. Once the reading conditions for the reading device 30 are set in the reading condition setting step S12, the process proceeds to the reading step S14.

[0196] In the reading step S14, reading of the printed image IMG is started when the leading edge of the printed image IMG to be read reaches the reading position of the reading device 30. In the reading step S14, a preset reading cycle is applied to read the entire printed image IMG. In the reading step S14, the illumination device is operated according to the illumination conditions, and the image sensor 32 is operated according to the image sensor conditions. Once the reading step S14 is started, the process proceeds to a reading completion determination step S16.

[0197] In the reading end determination step S16, the reading control unit 112 determines whether or not reading of the printed image IMG has ended. If it is determined in the reading end determination step S16 that reading of the printed image IMG will continue, the determination is No. If the determination is No, the process proceeds to the reading condition change determination step S18.

[0198] In the reading condition change determination step S18, the reading control unit 112 determines whether or not to maintain the reading conditions. If it is determined that the reading conditions are to be maintained in the reading condition change determination step S18, the determination is No. If the determination is No, the process proceeds to the reading step S14, and the reading step S14, the reading completion determination step S16, and the reading condition change determination step S18 are repeatedly executed until the determination is Yes in the reading completion determination step S16.

[0199] On the other hand, if it is determined that the reading conditions will be changed in the reading condition change determination step S18, a Yes determination is made. For example, if the type of substrate SU is changed or if it is determined that the type of print image IMG is changed, a Yes determination is made. If the Yes determination is made, the process proceeds to the reading condition setting step S12, and the reading step S14, the reading completion determination step S16, and the reading condition change determination step S18 are repeatedly executed until a Yes determination is made in the reading completion determination step S16.

[0200] On the other hand, if it is determined that the reading of the printed image has been completed in the reading completion determination step S16, the determination is Yes. If the determination is Yes, a specified end process is carried out and the procedure of the reading method is completed.

[0201] 15 is a table showing an example of how the illumination devices are used, which shows the relationship between the read characteristics and the combinations of on and off of the reflective illumination device 38, the transmitted light bright field illumination device 40, and the transmitted light dark field illumination device 42 shown in FIG.

[0202] Illumination condition 1, in which the reflective illumination device 38, the transmitted light brightfield illumination device 40, and the transmitted light darkfield illumination device 42 are all turned off, is applied to reading in the dark state of the image sensor 32. The dark state of the image sensor 32 is a state in which all illumination devices shown in Fig. 9 are turned off, the illumination light used in normal reading is eliminated, and transmitted illumination light that has passed through the substrate and reflected illumination light that has been reflected by the substrate do not reach the image sensor 32. Note that the dark state may also be a state in which the illumination light used in normal reading is eliminated in the absence of a substrate.

[0203] Illumination condition 2, in which the reflective illumination device 38 is turned on and the transmitted light bright field illumination device 40 and the transmitted light dark field illumination device 42 are turned off, is applied to reading a printed material in which paper is used as the substrate SU. Illumination condition 2 is applied to reading a printed image IMG in which a transparent substrate SU is used, in which the non-ink-applied areas NPP are relatively dark.

[0204] Illumination condition 3, in which the reflective illumination device 38 and the transmitted light dark field illumination device 42 are turned off and the transmitted light bright field illumination device 40 is turned on, is for reading a transparent substrate SU and is suitable for reading a printed image IMG when the ink application area PP is relatively dark.

[0205] In illumination condition 3, the transmitted brightfield illumination light, the uniformity of which has been increased using the light diffusing member 46, is incident on the imaging lens 34. The transmitted brightfield illumination light incident on the imaging lens 34 is incident on all of the light receiving elements of the image sensor 32. As a result, the reading range of the printed image IMG is read relatively brightly.

[0206] The transparent substrate SU supported at the reading position of the image sensor 32 is read such that the non-ink-applied areas NPP are read as relatively bright, and the ink-applied areas PP are read as relatively dark depending on the light transmittance and light diffusibility of the ink.

[0207] Illumination condition 3 is applied to read the non-ink-application region NPP of the substrate SU and obtain a first light transmission amount expressed as a pixel value of the read data. Illumination condition 3 is applied to obtain a second light transmission amount expressed as a pixel value of the read data in the absence of the substrate SU. The first light transmission amount and the second light transmission amount are used when setting the illumination conditions.

[0208] Illumination condition 4, in which the reflective illumination device 38 and the transmitted light bright field illumination device 40 are turned off and the transmitted light dark field illumination device 42 is turned on, is suitable for reading a transparent substrate SU and for clearly reading defects such as scratches on the substrate SU and image defects such as scratches on the printed image IMG.

[0209] Under illumination condition 4, the transmitted dark-field illumination light emitted from the transmitted dark-field illumination device 42 does not directly enter the imaging lens 34. However, the ink in the ink application region PP diffuses the dark-field illumination light emitted from the transmitted dark-field illumination device 42. A portion of the diffused dark-field illumination light enters the imaging lens 34 and is incident on the light-receiving elements of the image sensor 32, causing the ink to be read brightly.

[0210] In other words, since the transmitted dark field illumination device 42 illuminates the substrate SU from outside the field of view of the imaging lens 34, it does not function as illumination light for the substrate SU, which does not have light diffusion properties, but diffused light is generated for the ink, which does have light diffusion properties, and the diffused light incident on the imaging lens 34 functions as illumination light for the ink, so that the ink application area PP where the ink is present is read brightly.

[0211] Illumination condition 5, in which the reflective illumination device 38 is turned off and the transmitted light bright field illumination device 40 and the transmitted light dark field illumination device 42 are turned on, is used to read a transparent substrate SU and is applied when the ink application area PP is relatively bright.

[0212] Under illumination condition 5, it is further possible to adjust the contrast between the ink-applied areas PP and the non-ink-applied areas NPP by adjusting the amount of light emitted by the transmitted light brightfield illumination device 40 and the transmitted light darkfield illumination device 42. Furthermore, under illumination condition 5, read data of the printed image IMG including ink images of all colors is obtained, corresponding to the ink-applied areas PP where ink images of multiple colors are superimposed.

[0213] Illumination condition 5 is suitable for reading a test image, which is the print image IMG, when density unevenness correction is performed. In the density unevenness correction, density unevenness is corrected for each color in the print image IMG from high density regions to low density regions.

[0214] The test image used for density unevenness correction has a solid image having a plurality of different density values ​​for each ink color within the density range applied to printing. The plurality of different density values ​​for each ink color is preferably 10 or more.

[0215] The amount of transmitted illumination light is determined so that, among solid images having a plurality of different density values ​​for each ink color, the brightest solid image, which has the smallest amount of ink per unit area, can be distinguished from the non-ink-application areas NPP. This makes it possible to distinguish the non-ink-application areas NPP from the low-density ink-application areas PP. It is self-evident that solid images other than the solid image with the smallest amount of ink per unit area can be distinguished from the non-ink-application areas NPP. Hereinafter, the term ink amount refers to the amount of ink per unit area.

[0216] When a printed image IMG using cyan, magenta, yellow, and black inks is read using an image sensor 32 of colors corresponding to RGB, cyan ink is the complementary color of red and has a high light absorption rate for red. Similarly, magenta is the complementary color of green and has a high light absorption rate for green, and yellow is the complementary color of blue and has a high light absorption rate for blue. The pixel values ​​of the complementary colors of each ink color have a higher signal value than the pixel values ​​of other colors, making it easy to distinguish between ink-applied areas PP and non-ink-applied areas NPP.

[0217] For black ink and white ink, equivalent signal values ​​are obtained for each of the RGB colors. For black ink and white ink, the average value of each RGB pixel value may be used. That is, for inks other than cyan ink, magenta ink, and yellow ink, the pixel value of the color with the largest RGB pixel value may be used, or the average value of each RGB pixel value may be used. Using the pixel value of the color with the largest RGB pixel value simplifies processing. On the other hand, using the average value of the RGB pixel values ​​can reduce the random noise component superimposed on the output signal of the image sensor 32 by about 40%.

[0218] In actual adjustment, the emitted light intensity of the transmitted illumination light is set so that the value of the non-ink-applied area NPP becomes darker, but when setting the emitted light intensity of the transmitted illumination light, the emitted light intensity of the transmitted illumination light is set by focusing on the pixel value of the ink color that has the smallest difference from the pixel value of the read data of the non-ink-applied area NPP.

[0219] Illumination condition 6, in which the reflective illumination device 38 and the transmitted light bright field illumination device 40 are turned on and the transmitted light dark field illumination device 42 is turned off, is applied to reading a transparent substrate SU, which is similar to reading in which reflected illumination light RL is used.

[0220] Under illumination condition 6, illumination light emitted from the reflective illumination device 38 is irradiated onto the ink-applied region PP, reading the surface of the ink-applied region PP, and illumination light emitted from the transmitted bright field illumination device 40 is irradiated onto the non-ink-applied region NPP, reading the non-ink-applied region NPP brighter than the ink-applied region PP. In other words, illumination condition 6 can obtain read data that is close to the read data of a printed image IMG printed on a white background such as printing paper, and illumination condition 6 prevents the shadow SH of the printed image IMG shown in FIG. 3 from appearing in the read data.

[0221] Illumination condition 7, in which the reflective illuminator 38 and the transmitted light dark field illuminator 42 are turned on and the transmitted light bright field illuminator 40 is turned off, is used to read a transparent substrate SU, where the non-ink-applied areas NPP are relatively dark and the transmitted image of the printed image IMG in the ink-applied areas PP is read in a state where it overlaps with the reflected image generated when illumination light is irradiated onto the printed image IMG from the reflective illuminator 38. Illumination condition 7 emphasizes unevenness, and is therefore suitable for correcting unevenness.

[0222] Illumination condition 8, which turns on the reflective illuminator 38, the transmitted light brightfield illuminator 40, and the transmitted light darkfield illuminator 42, is used to read a transparent substrate SU, where the non-inked regions NPP are relatively bright and the transmitted image of the printed image IMG in the ink-applied regions PP is read in a state where it overlaps with the reflected image generated when illumination light is irradiated onto the printed image IMG from the reflective illuminator 38. Illumination condition 8, like illumination condition 7, emphasizes unevenness and is therefore suitable for correcting unevenness. Furthermore, when reading a test image used for density unevenness correction, illumination condition 8 reads the non-inked regions NPP as relatively bright, making it easy to separate the solid image having multiple different density values ​​that make up the test image from the non-inked regions NPP.

[0223] Here, Patent Document 1 discloses an illumination device that switches between bright field illumination light and dark field illumination light when reading a photographic film to detect scratches, etc. The document does not disclose reading a printed image printed on a transparent substrate SU using a printing device that uses an inkjet method or the like.

[0224] On the other hand, in the method for reading a printed image according to the embodiment, as described above, the reflective illumination device 38, the transmitted light bright-field illumination device 40, and the transmitted light dark-field illumination device 42 are selectively turned on and off, and the amount of light emitted from each is adjusted as desired. The combinations of turning on and off the reflective illumination device 38, the transmitted light bright-field illumination device 40, and the transmitted light dark-field illumination device 42 are as shown in the table of FIG.

[0225] Furthermore, the amount of emitted light can be adjusted as desired for each of the reflective illumination device 38, the transmitted light brightfield illumination device 40, and the transmitted light darkfield illumination device 42. This makes it possible to select illumination conditions suitable for reading each printed image IMG, such as when the amount of ink in the ink application area PP differs, when inks of multiple colors are overlapped, and when the ink overlap is relatively small.

[0226] When reading the print image IMG, it is necessary to be able to distinguish the area of ​​the ink-application area PP with the least amount of ink from the non-ink-application area NPP. Therefore, under illumination condition 5, the amount of light emitted by the transmitted light brightfield illumination device 40 and the transmitted light darkfield illumination device 42 is adjusted so that the brightness of the entire ink-application area PP is darker than the brightness of the non-ink-application area NPP.

[0227] Under illumination condition 5, when the output light amounts of the transmitted light brightfield illumination device 40 and the transmitted light darkfield illumination device 42 are adjusted, the illumination condition is suitable for reading test images applied to measure the ejection direction accuracy of each nozzle, which requires accurate reading of the density of the printed image IMG, and test images applied to correct density unevenness. Furthermore, when the test image to be read is applied to measure the ejection direction accuracy of each nozzle, the output light amount of the transmitted light darkfield illumination light is further reduced relative to the output light amount of the transmitted light brightfield illumination light, and the contrast of the line images constituting the test image to be used to measure the ejection direction accuracy is relatively increased.

[0228] Under illumination condition 5, when the output light amounts of the transmitted light brightfield illumination device 40 and the transmitted light darkfield illumination device 42 are adjusted so that, relative to the brightness of the non-ink-applied regions NPP, the brightness of the low-density regions of the ink-applied regions PP is brighter, and the brightness of the medium- to high-density regions of the ink-applied regions PP is darker, and the non-ink-applied regions NPP maintain a constant brightness, the signal-to-noise ratio is improved in the medium to high densities where streaks are most noticeable, and the density resolution is improved in the medium to high densities. This illumination condition is applied to reading test images used in inspecting printed matter for defects such as streaks, and makes it possible to read printed images that can improve the accuracy of streak detection.

[0229] Note that intermediate density refers to a density range that includes a density that is intermediate between the minimum density value on the bright side and the maximum density value on the dark side. When density values ​​are expressed using values ​​from 0 to 255, for example, intermediate densities can be in the range from 120 to 136. However, the range of intermediate densities is not limited to the range from 120 to 136, and can be defined as any range that includes the intermediate value of the density range.

[0230] When reading a test image applied to inspecting defects in a printed image IMG such as streaks, instead of the second transmitted dark field illumination condition in which the first transmitted dark field illumination device 42A and the second transmitted dark field illumination device 42B are turned on, a first transmitted dark field illumination condition can be applied in which either the first transmitted dark field illumination device 42A or the second transmitted dark field illumination device 42B is turned on and the other is turned off.

[0231] Furthermore, when reading a test image applied to inspecting printed matter for defects such as streaks, under illumination conditions 2, 6, 7, and 8 in which the reflective illumination device 38 is turned on, instead of the second reflective illumination condition in which the first reflective illumination device 38A and the second reflective illumination device 38B are turned on, a first reflective illumination condition in which either the first reflective illumination device 38A or the second reflective illumination device 38B is turned on and the other is turned off can be applied.

[0232] Under these lighting conditions, when inspecting printed matter for defects such as streaks when ink that produces raised ink dots is used, reading is performed in such a way that the shadows of the ink dots in the area where defects such as streaks exist are emphasized. Note that under all lighting conditions, the brightness of the darkest area in the read data of the ink-applied area PP is made greater than the noise value of the image sensor.

[0233] The adjustment of the amount of emitted illumination light from each illumination device is performed when starting up the printing system 10 shown in Fig. 9. Furthermore, the amount of emitted illumination light from each illumination device may be readjusted depending on the results of processing in which the read data is used.

[0234] The illumination conditions shown in the table of FIG. 15 are an example of a combination of two or more determined illumination conditions of a transmitted light bright-field illumination device and an illumination condition of a transmitted light dark-field illumination device.

[0235] [Application Example of the Embodiment] FIG. 16 is an explanatory diagram of an application example of the embodiment. FIG. 16 schematically illustrates scan data of a printed image IMG constituting a printed material. The image sensor 32 outputting the scan data shown in FIG. 16 is a line sensor, and is capable of scanning the entire width of the substrate SU in the substrate width direction by scanning one line. The entire scan data 300 shown in FIG. 16 represents the entire printed image IMG. In FIG. 16, 16 scan lines numbered 1 to 16 from top to bottom are schematically illustrated on the left side of the entire scan data 300. Each scan line shown in FIG. 16 has multiple pixels arranged in a row in the left-right direction, forming two-dimensional scan data as a whole. In the scan data scanned using the image sensor 32 shown in FIG. 1, for example, 7,500 pixels are arranged on each scan line. Each pixel is composed of data for three colors: red, green, and blue.

[0236] When LED light sources or laser light sources are used as the light sources for the reflective illumination device 38, the transmitted light brightfield illumination device 40, and the transmitted light darkfield illumination device 42, the light sources can be turned on and off at high speed, and the light intensity can be adjusted. Therefore, the light sources are turned on and off in synchronization with the reading of each reading line used by the image sensor 32, applying a predetermined light intensity each time each line is read. When reading the entire read data 300, either illumination condition 4 or illumination condition 5 is applied in conjunction with the reading of one line by the image sensor 32, and the entire print image IMG is read, generating the entire read data 300 in which lines with different illumination conditions appear alternately.

[0237] In the entire read data 300, when 16 lines are read, illumination condition 4 is applied to the odd-numbered lines and illumination condition 5 is applied to the even-numbered lines. That is, in the entire read data 300, illumination condition 4 is applied to odd-numbered read lines and illumination condition 5 is applied to even-numbered read lines alternately.

[0238] From the entire read data 300, first partial read data 302 to which illumination condition 4 is applied and second partial read data 304 to which illumination condition 5 is applied are generated. In other words, as a result of reading one print image, multiple read data under different illumination conditions are obtained.

[0239] The first partial scanned data 302 to which illumination condition 4 is applied is scanned data suitable for detecting defects such as streaks in a printed image that uses a transparent substrate SU. The second partial scanned data 304 to which illumination condition 5 is applied is scanned data suitable for correcting density unevenness.

[0240] When reading using an image sensor 32 having three lines corresponding to each of the RGB colors, the reading data for each color read at the same time does not match in position in the printed image, but is positioned one or two lines apart in the substrate transport direction.

[0241] When an image sensor 32 is used in which the distance between lines corresponding to each color in the substrate transport direction is one line, two types of illumination conditions are alternately switched at each reading timing to obtain read data for each color at the same position on the printed image. In this case, the resolution in the substrate transport direction of the read data for each illumination condition is half the reading resolution.

[0242] When an image sensor 32 is used in which the distance between lines corresponding to each color in the substrate conveyance direction is two lines, reading three lines will obtain read data for each color at the same position on the print image IMG. In such a case, three types of illumination conditions are switched in sequence at each reading timing.

[0243] When two types of illumination conditions are applied, one illumination condition is applied to read two lines, and the other illumination condition is applied to read one line. When two types of illumination conditions are applied, the reading cycle of the image sensor 32 is set to two-thirds of that when the illumination conditions are not switched, and the two types of illumination conditions are alternately switched at each reading timing.

[0244] The read data when the illumination conditions are switched has a smaller number of read lines and a lower resolution than the read data when the illumination conditions are not switched, so that a variable magnification process is performed in the substrate conveyance direction as necessary to generate read data having a specified resolution. In this embodiment, a line sensor is exemplified as the image sensor 32, but an area sensor may also be used as the image sensor 32.

[0245] Note that the illumination condition 4 applied to reading odd-numbered lines described in the embodiment is an example of a first transmitted illumination condition, and the illumination condition 5 applied to even-numbered lines is an example of a second transmitted illumination condition. Also, the first partial read data 302 described in the embodiment is an example of first read data, and the second partial read data 304 is an example of second read data.

[0246] [Application example of illumination device] Fig. 17 is a schematic diagram of an illumination device according to an application example. Fig. 17 schematically illustrates the structure of an illumination device 400 having a length in the substrate width direction corresponding to the entire width of the substrate SU. The illumination device 400 shown in Fig. 17 has the function of the transmitted light bright-field illumination device 40 shown in Fig. 1 and also has the function of the transmitted light dark-field illumination device 42. The substrate width direction is the direction penetrating the plane of the paper in Fig. 17 .

[0247] The lighting device 400 includes an LED light source 402, a diffuser 404, a mirror box 406, and a pair of movable reflectors 408. The pair of movable reflectors 408 are configured to be movable by driving a motor (not shown) so as to increase or decrease the distance between them in the left-right direction in FIG. 17 . The inner surface of the mirror box 406, the front surface of the movable reflector 408, and the back surface of the movable reflector 408 are mirror surfaces with a light reflectance of approximately 90% or more. Arrows shown inside the mirror box 406 represent the illumination light emitted from the LED light source 402.

[0248] The illumination light emitted from the LED light source 402 is divided into light that reaches the diffuser plate 404 directly, light that is reflected on the inner surface of the mirror box 406 and reaches the diffuser plate 404, light that reaches the movable reflector plate 408, and light that passes through the gaps on the left and right sides of the pair of movable reflectors 408.

[0249] Furthermore, the light that reaches the movable reflector 408 is reflected by the surface of the movable reflector 408 and further reflected repeatedly by the internal surfaces of the mirror box 406, and is divided into light that reaches the diffuser 404, light that reaches the movable reflector 408, and light that passes through the gaps on the left and right sides of the pair of movable reflectors 408. The light that reaches the diffuser 404 becomes bright-field illumination light, and the light that passes through the gaps on the left and right sides of the pair of movable reflectors 408 becomes dark-field illumination light.

[0250] The movable reflector 408 has the function of splitting the illumination light that reaches it into bright-field illumination light and dark-field illumination light. The ratio of light that reaches the diffuser 404 to light that passes through the left and right gaps between the pair of movable reflectors 408 is determined depending on the position of the movable reflector 408, so the movable reflector 408 adjusts the ratio of bright-field illumination light to dark-field illumination light depending on its position. The movable reflector 408 and the mirror box 406 do not need to be flat reflective members, and may be reflective members with a curved surface such as an arc cross section. Note that the movable reflector 408 described in the embodiment is an example of a light diffusing member.

[0251] That is, part of the branched illumination light reaches the diffuser plate 404 and is irradiated as transmitted bright-field illumination light onto the reading position of the image sensor 32. The illumination light that does not reach the diffuser plate 404 is irradiated as transmitted dark-field illumination light from outside the field of view of the imaging lens 34 onto the reading position of the image sensor 32.

[0252] The ratio between the transmitted bright-field illumination light and the transmitted dark-field illumination light is determined according to the positions of the pair of movable reflectors 408. In other words, the illumination device 400 can adjust the ratio between the transmitted bright-field illumination light and the transmitted dark-field illumination light according to the positions of the pair of movable reflectors 408. Adjustment of the emitted light intensity of the transmitted bright-field illumination light and the emitted light intensity of the transmitted dark-field illumination light can be achieved by adjusting the emitted light intensity of the LED light source 402.

[0253] The pair of movable reflectors 408 described in the embodiment is an example of a switching member that switches between the proportion of the emitted light that is incident on the light diffusion member and emitted from within the field of view of the imaging lens, and the proportion of the emitted light that is not incident on the light diffusion member and is emitted from outside the field of view of the imaging lens.

[0254] 15 , the illumination device 400 adjusts the amount of light emitted from the LED light source 402 and adjusts the position of the movable reflector 408. Compared to a case in which the transmitted light bright-field illumination device 40 and the transmitted light dark-field illumination device 42 are provided separately, the illumination device 400 has the disadvantage of increasing the amount of light emitted from the LED light source 402, but the transmitted light bright-field illumination device 40 and the transmitted light dark-field illumination device 42 are integrated, thereby reducing the number of light sources and the number of drive power supplies for the light sources.

[0255] Furthermore, the illumination device 400 requires components such as a diffuser 404 and a movable reflector 408, but these can be manufactured using sheet metal parts and drawn metal parts, and are less expensive than light sources, allowing the desired effect to be achieved with a cost-reduced configuration. Furthermore, in the case of a reading device installed in a printing system with a relatively slow printing speed, the reading speed is also slow, and the required absolute light intensity can be reduced, so that illumination light with an intensity suitable for reading can be obtained in a configuration using one light source.

[0256] [Specific example of read data] The read data generated by reading the print image using the image sensor 32 is digital data and can be understood as having a structure equivalent to an image in which multiple pixels are arranged two-dimensionally. When the read data is considered as image data, each pixel has a pixel value corresponding to the brightness of each position on the print image IMG.

[0257] The pixel value is an output signal value of the image sensor 32 and is represented in a digital format. When the pixel value is represented as 8-bit digital data, each pixel has a pixel value represented using an integer ranging from 0 to 255. When the pixel value is represented as 10-bit digital data, each pixel has a pixel value represented using an integer ranging from 0 to 1023.

[0258] When an RGB color sensor is used as the image sensor 32, each pixel has a pixel value of each of RGB. ＊ a ＊ b ＊ The form of the output signal from the image sensor 32 is determined by the characteristics of the color filters provided in the image sensor 32.

[0259] In this embodiment, pixel values ​​are represented as 8-bit digital data, with the darkest pixel value being 0 and the brightest pixel value being 255. However, due to variations in the substrate SU, variations in the distribution of the emitted light intensity of the illumination light, changes over time in the emitted light intensity of the illumination light, and fluctuations in the sensitivity of the image sensor 32, the brightness of the image on the brightest side may exceed the maximum pixel value of 255. When the image brightness exceeds the maximum pixel value of 255, this is generally referred to as overflow, and the pixel value of the overflowing pixel becomes 255. In such cases, it is difficult to properly read the print image IMG. Therefore, the reading conditions of the image sensor 32 are specified so that a margin is added to the pixel values ​​of the read data, and the pixel values ​​of the read data of the non-ink application region NPP are around 230. The value of this margin is determined primarily depending on the illuminance distribution of the illumination device used, the magnitude of brightness fluctuations in the illumination device used, the pixel-to-pixel variation in the sensitivity of the image sensor used, and the magnitude of the sensitivity fluctuations of the image sensor used.

[0260] Reading conditions are applied in which an upper limit value for the pixel value on the brightest side is specified, and the pixel value of the read data of the printed image IMG printed on a transparent substrate SU can be specified as the amount of light transmission of ink at each position in the printed image IMG.

[0261] When determining the amount of emitted illumination light, the pixel value of each pixel in the read data of the specified pattern is obtained. If the specified pattern is a solid image having a uniform density including multiple pixels, the average value of the pixel values ​​of the multiple pixels can be determined as the amount of light transmitted through the specified pattern.

[0262] When calculating the average value of pixel values ​​for a plurality of pixels that make up a pattern, the random error component is reduced by a factor of 1 / square root of the number of pixels used to calculate the average value. For example, if the number of pixels used to calculate the average value is 100, the random error component is reduced by a factor of 10.

[0263] [Specific example of adjusting the amount of emitted illumination light] In controlling the brightness expressed as pixel values ​​of the read data of the printed image IMG, the amount of emitted light from the transmitted light brightfield illumination device 40 and the transmitted light darkfield illumination device 42 is determined so that the non-ink-applied areas NPP of the substrate SU have a specified brightness and the maximum pixel value of the read data of the ink-applied areas PP is equivalent to the pixel value of the read data of the non-ink-applied areas NPP.

[0264] The term "equivalent" may refer to the same or may refer to a case where there is a difference that is less than the reading resolution of the image sensor. An example of the specified brightness of the non-ink-applied region NPP is a pixel value of 230 when the pixel values ​​of the read data are expressed as integers from 0 to 255.

[0265] In adjusting the amount of emitted illumination light, the amount of emitted illumination light is set so that the ink-applied area PP is darker than the non-ink-applied area NPP. The degree to which the ink-applied area PP is darkened is determined such that, when the pixel value of the read data of the non-ink-applied area NPP is set to 230, the pixel value in the read data of a solid image having a print density of 0.25 to 0.35 is 103 to 129 for the ink color that has the smallest difference between the maximum pixel value of the read data and the pixel value 230. Note that the print density D is expressed as the intensity of light incident on the surface of the printed material, expressed as I. ｉｎ and the intensity of light reflected from the surface of the print is I ｏｕｔ In this case, D=Log １０ (I ｉｎ / I ｏｕｔ ) is a relative value expressed as Log １０ is a logarithm with the base 10. For example, if the intensity of light reflected from the surface of the print is half of the intensity of light incident on the surface of the print, D is approximately 0.3.

[0266] In this lighting state where the amount of emitted light is adjusted, the maximum pixel value in the read data of the ink-applied region PP is equal to the pixel value in the read data of the non-ink-applied region NPP.

[0267] For example, when the print density of a solid image is in the print density range of 0.25 to 0.35 and the pixel value in the read data of the solid image is in the print density range of 103 to 129, appropriate accuracy can be obtained in image processing of a test image for correcting density unevenness in a relatively light print density range. When the print density of the solid image is in the print density range of less than 0.25 and the pixel value in the read data of the solid image is less than 103, the pixel value in the read data becomes relatively small, and the error in calculation becomes relatively large due to the decrease in density resolution, raising concerns about a decrease in correction accuracy.

[0268] Furthermore, when the print density of a solid image is in a print density range exceeding 0.35 and the pixel value in the read data of the solid image exceeds 129, the pixel value in the read data of the solid image with the lightest density in a test image made up of multiple solid images with different densities, which is used when correcting density unevenness, may exceed 255, causing pixel value overflow. When pixel value overflow occurs, there is a concern that appropriate unevenness correction cannot be performed in the light density range.

[0269] [Improving quality in analysis of read data] In controlling the brightness expressed as pixel values ​​of the read data of the printed image IMG, the amount of light emitted from the transmitted bright field illumination device 40 and the transmitted dark field illumination device 42 is determined so that the non-ink applied area NPP of the substrate SU has a specified brightness and the maximum pixel value in the read data of the area in the ink applied area PP where the amount of ink is less than a specified amount exceeds the pixel value of the non-ink applied area NPP.

[0270] The purpose of adjusting the amount of emitted illumination light as described above is to improve the quality of processing of read data from areas of the ink-application area PP where the amount of ink is relatively large. Areas of the ink-application area PP where the amount of ink is relatively small and bright have relatively large pixel values ​​in the read data, are less susceptible to the influence of noise, and have high pixel value resolution.

[0271] On the other hand, in the dark areas of the ink application area PP where the amount of ink is relatively large, the pixel values ​​in the read data are relatively small, making them more susceptible to noise and lowering the resolution of the pixel values. In particular, in the areas where the amount of black ink is at its maximum, the pixel value is around 3, which means that the accuracy of density unevenness correction is insufficient.

[0272] Therefore, an area in the ink-application area PP where the amount of ink is equal to or less than a specified amount is arbitrarily defined, and the amounts of light emitted by the transmitted light bright-field illumination device 40 and the transmitted light dark-field illumination device 42 are determined so that the pixel values ​​of the read data for the area where the amount of ink is equal to or less than the specified amount are greater than the pixel values ​​of the read data for the non-ink-application area NPP. When pixel values ​​are expressed using integers from 0 to 255, a pixel value of 230 can be applied as the pixel value of the read data for the non-ink-application area NPP.

[0273] As a result, the dark areas in the ink application area PP where the amount of ink is relatively large become relatively brighter, the effect of noise from the image sensor 32 becomes relatively smaller, and the resolution of pixel values ​​becomes relatively higher, so that uneven density in high-density areas can be appropriately corrected.

[0274] On the other hand, in areas in the ink application area PP where the amount of ink is below a specified amount, particularly in areas where the amount of ink is relatively small, the pixel value may exceed the maximum value of 255, making it impossible to obtain accurate read data. Below, we will explain how to deal with cases where the pixel value exceeds the maximum value and accurate read data cannot be obtained.

[0275] When reading a test image using the image sensor 32, the amount of light emitted from the transmitted illumination device 44 is adjusted so that the pixel value of the read data for the non-ink-applied area NPP is around 230, and the adjustment of the amount of light emitted from the illumination device 44 is selectively switched between adjusting the amount of light emitted from the illumination device 44 to be applied to reading a solid image with a density value below a specified value and adjusting the amount of light emitted from the illumination device 44 to be applied to reading a solid image with a density value above the specified value.

[0276] When reading a solid image with a density value below a specified value, the amount of emitted illumination light is adjusted so that the maximum pixel value in the read data of the ink-applied area PP is equivalent to the pixel value in the read data of the non-ink-applied area NPP.

[0277] In addition, when reading a solid image that exceeds the specified density value, the amount of emitted illumination light is adjusted so that the maximum pixel value of the read data in the area of ​​the ink application area PP where the ink amount is below the specified amount exceeds the pixel value of the read data in the non-ink application area NPP.

[0278] Adjusting the amount of emitted illumination light in this way prevents the pixel value of the read data from exceeding 255, making it impossible to read the image. Also, dark areas of the ink application area PP, where the amount of ink is relatively large, are read as relatively bright.

[0279] When the emitted light intensity of the illumination light is adjusted in this manner, the emitted light intensity of the illumination light differs between areas where the ink amount is below a specified amount and areas where the ink amount exceeds a specified amount, so relative correction of the read data in each area is necessary.

[0280] The emitted light amount of illumination light applied to an area where the ink amount is equal to or less than the specified amount is set to A, and the emitted light amount of illumination light applied to an area where the ink amount exceeds the specified amount is set to B. The emitted light amount A exceeds the emitted light amount B.

[0281] The scanned data in the area where the ink amount exceeds the specified amount is multiplied by A / B to correct the scanned data in the area where the ink amount exceeds the specified amount. When the pixel values ​​of each scanned data described above are expressed using 8-bit integers, it is preferable to apply an integer with a bit number greater than 8, such as 16 bits, to the pixel values ​​during multiplication. This prevents overflow during multiplication.

[0282] The image used to inspect image defects such as streaks is read as follows: First, the amount of light emitted from the transmitted illumination device 44 is adjusted so that the pixel value of the read data of the non-ink-application area NPP becomes 255.

[0283] In inspecting image defects, the pixel values ​​of the read data themselves are not important; all that is required is that valid read data of the ink-applied area PP is obtained and that the pixel values ​​of the read data are relatively large. This reduces the effect of noise superimposed on the read data and relatively increases the resolution of the read data.

[0284] In areas of the ink application area PP with relatively low density values, image defects such as streaks are less likely to be visible. Therefore, in areas with relatively high density values ​​where image defects are more likely to be visible, the amount of emitted illumination light is adjusted so that the pixel value of the read data in the area with the minimum density value becomes 255.

[0285] This allows the largest possible range of pixel values ​​to be obtained in the read data, from areas with relatively low print density values ​​to areas with relatively high print density values, in the range of print density values ​​where streaks and the like are easily visible, thereby ensuring a certain level of accuracy in inspecting image defects.

[0286] The print density value at which image defects are less likely to be visible is generally 0.1 or less for black ink, which is the ink that makes image defects most noticeable. However, the print density value at which image defects are less likely to be visible differs for each ink.

[0287] Countermeasures for noise caused by dark current of image sensor The following describes countermeasures for noise generated in the image sensor 32. When illumination light is irradiated onto the print image IMG and the print image IMG is read, the amount of emitted illumination light is adjusted so that the pixel value of the read data in the darkest area of ​​the ink application area PP exceeds the pixel value corresponding to the dark current of the image sensor 32.

[0288] Noise caused by dark current in the image sensor 32 is determined based on the read data in a dark state. The pixel values ​​of the read data generated by reading the print image IMG in a dark state represent noise equivalent to the dark current. The pixel value representing the noise equivalent to the dark current is calculated by applying the average value of the pixel values ​​of each pixel in the read data.

[0289] As a countermeasure against noise in the read data, the amount of emitted illumination light is adjusted so that the minimum pixel value in the read data of the print image IMG is greater than the pixel value of the read data corresponding to the dark current generated in the image sensor 32.

[0290] "Larger than the pixel value corresponding to the dark current" means that when the pixel values ​​of the read data are used as is in analyzing the read data, the minimum pixel value in the read data when the lighting device is turned on is greater than the value obtained by adding the standard deviation of the pixel values ​​of each pixel of the read data in a dark state to the average value of the pixel values ​​of each pixel of the read data in a dark state.

[0291] The term "greater than the pixel value corresponding to the dark current" means that, when analyzing the read data, n is an integer of 2 or more, and when n pixel values ​​are averaged and used to analyze the read data, the standard deviation is n １／２ This indicates that the minimum pixel value in the read data when the illumination device is turned on is greater than the value obtained by adding the value obtained by dividing by .

[0292] Effects of the Embodiment The printing system 10 of the embodiment can achieve the following effects.

[0293] [1] When reading the printed image IMG, if only the reflective illumination device 38 or only the transmitted light bright-field illumination device 40 is used, it is difficult to read the printed image IMG at an appropriate brightness for each of measuring the ejection accuracy, measuring density unevenness, and inspecting image defects due to the influence of the light diffusion properties of the ink. In the printing system shown in this embodiment, by adding the transmitted light dark-field illumination device 42, it becomes possible to read the printed image IMG at an appropriate brightness for each of measuring the ejection accuracy, measuring density unevenness, and inspecting image defects.

[0294] [2] The illumination conditions are defined according to the processing to be performed on the read data, thereby setting illumination conditions for reading the print image that are suitable for the processing to be performed on the read data.

[0295] [3] When the read data is expressed using integers from 0 to 255, the illumination conditions are set so that the pixel value of the non-inked area of ​​the substrate SU, where no ink is applied, is set to around 230. This prevents the brightest area of ​​the read data from being too bright and preventing the print image IMG from being read correctly.

[0296] [4] Only one of the first transmitted light dark field illumination device 42A or the second transmitted light dark field illumination device 42B is turned on. This makes it possible to improve the visibility of streaks in the printed image by utilizing the shadow of the printed image IMG.

[0297] [5] Only one of the first reflective lighting device 38A or the second reflective lighting device 38B is turned on. This makes it possible to utilize the shadow of the print image IMG to improve the visibility of streaks in the print image.

[0298] [6] When pixel values ​​in the read data are expressed using integers between 0 and 255, the pixel values ​​in the read data of the non-ink-applied areas of the substrate SU are adjusted to around 230. When reading the printed image for density unevenness correction, the pixel values ​​in the read data of a solid image having the same density as the area with the smallest ink amount are compared for each ink color. The lighting conditions are set based on the pixel value in the read data of the ink color with the smallest pixel value. This prevents the minimum density value of the lightest ink color from being brighter than the non-ink-applied areas, and the lighting conditions can be set based on the lightest ink color.

[0299] That is, for each ink color, the emitted light intensity of the illumination light is adjusted so that the pixel value of the preferred read data or the average value of multiple pixel values ​​can be distinguished between the solid image with the least amount of ink and the read data of the non-ink-applied area of ​​the substrate SU.

[0300] [7] When pixel values ​​in the read data are expressed using integers from 0 to 255, the pixel values ​​in the read data of the non-ink-applied regions of the substrate SU are adjusted to around 230. The emitted light intensity of the illumination light is adjusted so that the maximum pixel value in the read data of the ink-applied regions is equivalent to the pixel value in the read data of the non-ink-applied regions of the substrate SU. This adjusts the emitted light intensity of the illumination light so that the brightness of the region with the lightest ink density is equivalent to the brightness of the non-ink-applied regions of the substrate SU.

[0301] [8] When pixel values ​​in the read data are expressed using integers from 0 to 255, the pixel values ​​in the read data of the non-ink-applied regions of the substrate SU are adjusted to around 230. The emitted light intensity of the illumination light is adjusted so that the ink-applied regions where the ink amount is below a specified amount are brighter than the non-ink-applied regions of the substrate SU. This makes it possible to improve the signal-to-noise ratio in the read data when only the ink-applied regions are subject to inspection and the non-ink-applied regions are not. It also makes it possible to improve the resolution of the pixel values ​​in the read data.

[0302] [9] The amount of emitted illumination light is adjusted so that the maximum pixel value in the read data of the ink-applied area when the illumination light is emitted is greater than the pixel value in the read data caused by the dark current of the image sensor 32. This can reduce the influence of noise in the read data caused by the image sensor 32.

[0303]

[10] In one reading of one printed image, multiple illumination conditions are applied and the illumination conditions are switched in units of reading lines, thereby generating read data for each illumination condition.

[0304] 1 and the like can be configured as an external device of the printing system 10. That is, a reading device that includes the image sensor 32, imaging lens 34, reflective illumination device 38, transmitted light bright field illumination device 40, and transmitted light dark field illumination device 42 shown in FIGS. 1 and 2 and that includes the reading control unit 112 and reading condition setting unit 124 shown in FIG. 11 can function as an external device of the printing system 10.

[0305] A reading device that can function as an external device for the printing system 10 includes components having functions related to the control of the reading device 30 by the system control unit 100. The reading device may include a reading condition storage unit 126.

[0306] [Example of application to an inspection device] A configuration including the reading device 30 provided in the printing system 10 shown in Fig. 1 etc., and the system control unit 100, reading control unit 112, and read data analysis unit 114 shown in Fig. 11 can function as an inspection device for printed matter output from the printing system. The inspection device may include a substrate information acquisition unit 120, a reading condition setting unit 124, and a reading condition storage unit 126.

[0307] The above-described embodiments of the present invention may be modified, added, or deleted as appropriate within the scope of the spirit of the present invention. The present invention is not limited to the above-described embodiments, and many modifications may be made by a person skilled in the art within the technical concept of the present invention. Furthermore, the embodiments, modifications, and applications may be implemented in appropriate combinations.

[0308] REFERENCE SIGNS LIST 10 Printing system 12 Conveying device 14 Supply roll 16 Support roller 18 Recovery roll 20 Printing device 30 Reading device 32 Image sensor 34 Imaging lens 36 Reference plate 38 Reflection illumination device 38A First reflection illumination device 38B Second reflection illumination device 40 Transmitted light bright field illumination device 42 Transmitted light dark field illumination device 42A First transmission dark field illumination device 42B Second transmission dark field illumination device 44 Transmitted light illumination device 46 Light diffusion member 60 Fixing device 70 Ink supply device 72 Maintenance device 100 System control unit 102 Conveying control unit 104 Printing control unit 106 Fixing control unit 108 Ink supply control unit 110 Maintenance control unit 112 Reading control unit 114 Read data analysis unit 120 Substrate information acquisition unit 122 Print data acquisition unit 124 Reading condition setting unit 126 Reading condition storage unit 130 Storage device 132 Sensor 140 Reading condition acquisition unit 142 Image sensor control unit 144 First reflected illumination control unit 146 Second reflected illumination control unit 148 Bright field illumination control unit 150 First dark field illumination control unit 152 Second dark field illumination control unit 154 Read data acquisition unit 200 Control device 202 Processor 204 Computer readable medium 206 Communication interface 208 Input / output interface 210 Bus 212 Memory 214 Storage 216 Input device 218 Display 220 Conveyance control program 222 Print control program 224 Reading control program 226 Read data analysis program 228 Fixing control program 230 Maintenance control program 232 Substrate information 234 Reading conditions 300 Overall read data 302 First partial read data 304 Second partial read data 400 Illumination device 402 LED light source 404 Diffusion plate 406 Mirror box 408 Movable reflector S10 to S18 Steps of reading method CI Color ink IMG Printed image LS Light source LDP Light diffusion member M1 Motor M2 Motor M3 Motor NPP Non-ink applied area NPF Non-printed surface OA Optical axis PF Printed surface PP Ink applied area RL Reflected illumination light SH Shadow SU Base material TL Transmitted illumination device TLL Transmitted illumination light WI White ink

Claims

a transmitted light illumination device arranged opposite the light receiving surface of the image sensor, the transmitted light illumination device including a transmitted light brightfield illumination device arranged within the field of view of the imaging lens and a transmitted light darkfield illumination device arranged outside the field of view of the imaging lens; a transmitted light illumination condition setting unit that sets the transmitted light illumination conditions to be applied to the transmitted light illumination device; and one or more first processors, wherein the transmitted light illumination condition setting unit sets the transmitted light illumination conditions to be applied to the transmitted light illumination device and sets the transmitted light illumination conditions to be applied to the transmitted light darkfield illumination device in accordance with processing performed on the read data, and the one or more first processors control each of the transmitted light illumination device and the transmitted light darkfield illumination device in accordance with the transmitted light illumination conditions set using the transmitted light illumination condition setting unit.

2. The reading device described in claim 1, wherein the transmitted illumination condition setting unit sets the amount of light emitted by the transmitted illumination device based on a first light transmittance obtained from reading data acquired by turning on the transmitted brightfield illumination device and reading a non-ink-applied area of ​​the substrate, which is an area where ink is not applied, or a state in which the substrate is not present, or based on a second light transmittance obtained from reading data acquired by turning on the transmitted darkfield illumination device and reading a non-ink-applied area of ​​the substrate, which is an area where ink is not applied, or a state in which the substrate is not present.

3. The reading device according to claim 1, wherein the image sensor is a color sensor and a line sensor.

4. The reading device according to claim 1, wherein the transmitted dark field illumination device comprises: a first transmitted dark field illumination device that emits illumination light in a first direction; and a second transmitted dark field illumination device that emits illumination light in a second direction different from the first direction.

5. The reading device described in claim 4, wherein the transmitted light illumination condition setting unit sets a first transmitted light dark field illumination condition in which either the first transmitted light dark field illumination device or the second transmitted light dark field illumination device is turned on, or a second transmitted light dark field illumination condition in which both the first transmitted light dark field illumination device and the second transmitted light dark field illumination device are turned on, depending on the processing performed on the read data.

6. The reading device according to claim 1, wherein the transmitted illumination device is provided with a light diffusing member for diffusing light emitted from at least one of the transmitted bright field illumination device and the transmitted dark field illumination device.

7. A reading device as described in claim 1, comprising: a reflective lighting device that is arranged on the same side as the image sensor with respect to a space divided in two by a plane perpendicular to the optical axis of the imaging lens at the reading position of the image sensor, and that irradiates illumination light onto the substrate supported at the reading position; a reflective lighting condition setting unit that sets reflective lighting conditions to be applied to the reflective lighting device; and one or more second processors, wherein the one or more second processors control the reflective lighting device in accordance with the reflective lighting conditions.

8. The reading device described in claim 7, wherein the reflective lighting device comprises a first reflective lighting device which emits illumination light in a third direction, and a second reflective lighting device which emits illumination light in a fourth direction different from the third direction, and the reflective lighting condition setting unit sets a first reflective lighting condition for turning on either the first reflective lighting device or the second reflective lighting device, or a second reflective lighting condition for turning on both the first reflective lighting device and the second reflective lighting device, depending on the processing performed on the read data.

9. The reading device of claim 1, wherein the one or more first processors set the amount of light emitted by the transmitted dark field illumination device so that, when the pixel values ​​of the read data are greater in relatively bright parts of the printed image than in relatively dark parts, the maximum average value of the pixel values ​​of the read data of the solid images in the first test image printed on the transparent substrate, the first test image including a plurality of solid images having different density values ​​for each of one or more ink colors, exceeds the average value of the pixel values ​​of the read data in non-ink-applied areas of the substrate.

10. The reading device of claim 1, wherein the one or more first processors adjust the amount of light emitted by the transmitted dark field illumination device so that the maximum pixel value in the read data of the printed image printed on the transparent substrate becomes equal to the pixel value of the non-inked area on the substrate.

11. The reading device according to claim 1, wherein the one or more first processors adjust the amount of light emitted by the transmitted dark field illumination device so that the maximum pixel value in the read data of an ink-applied area of ​​the transparent substrate, where the amount of ink per unit area is equal to or less than a specified amount, exceeds the pixel value of an ink-unapplied area of ​​the substrate.

12. The reading device according to claim 1, wherein the one or more first processors adjust the amount of light emitted by the transillumination device so that, when the transillumination device is turned on, the minimum pixel value in the read data generated by reading the printed image using the image sensor becomes greater than the pixel value of the read data corresponding to the dark current of the image sensor.

13. The reading device of claim 1, wherein the transmitted illumination condition setting unit determines two or more combinations of illumination conditions of the transmitted brightfield illumination device and the transmitted darkfield illumination device, and sets the combination of illumination conditions of the transmitted brightfield illumination device and the transmitted darkfield illumination device according to the reading conditions of the image sensor.

14. The reading device described in claim 1, wherein the transmitted illumination condition setting unit sets a first transmitted illumination condition and a second transmitted illumination condition different from the first transmitted illumination condition for reading one of the printed images, the one or more processors switch between the first transmitted illumination condition and the second transmitted illumination condition when reading one of the printed images, and the image sensor generates first reading data to which the first transmitted illumination condition is applied, and generates second reading data to which the second transmitted illumination condition is applied.

15. A reading method applied to a reading device comprising: an image sensor that reads a printed image printed on a substrate and generates read data of the printed image; an imaging lens that forms an optical image of the printed image on the image sensor, the imaging lens defining a field of view that represents the range in which an illumination device that directly incidents illumination light is positioned; and a transmitted illumination device that is positioned opposite the light receiving surface of the image sensor, the transmitted illumination device comprising a transmitted brightfield illumination device that is positioned within the field of view of the imaging lens and a transmitted darkfield illumination device that is positioned outside the field of view of the imaging lens, the reading method comprising the steps of: setting transmitted brightfield illumination conditions to be applied to the transmitted brightfield illumination device, and setting transmitted darkfield illumination conditions to be applied to the transmitted darkfield illumination device, in accordance with processing to be performed on the read data; emitting transmitted brightfield illumination light from the transmitted brightfield illumination device in accordance with the transmitted brightfield illumination conditions; emitting transmitted darkfield illumination light from the transmitted darkfield illumination device in accordance with the transmitted darkfield illumination conditions; and reading the printed image using the image sensor.

16. A program applicable to a reading device comprising: an image sensor that reads a printed image printed on a substrate and generates read data of the printed image; an imaging lens that forms an optical image of the printed image on the image sensor, the imaging lens defining a field of view that represents the range in which an illumination device that directly incidents illumination light is positioned; and a transmitted illumination device that is positioned opposite the light receiving surface of the image sensor, the transmitted illumination device comprising a transmitted brightfield illumination device that is positioned within the field of view of the imaging lens, and a transmitted darkfield illumination device that is positioned outside the field of view of the imaging lens, wherein the program causes a computer to realize the following functions: setting transmitted brightfield illumination conditions to be applied to the transmitted brightfield illumination device, and setting transmitted darkfield illumination conditions to be applied to the transmitted darkfield illumination device, in accordance with processing performed on the read data; a function of emitting transmitted brightfield illumination light from the transmitted brightfield illumination device in accordance with the transmitted brightfield illumination conditions; a function of emitting transmitted darkfield illumination light from the transmitted darkfield illumination device in accordance with the transmitted darkfield illumination conditions; and a function of reading the printed image using the image sensor.

17. A non-transitory computer-readable recording medium having the program according to claim 16 recorded thereon.

18. An inspection device comprising: a reading device that reads a print image printed on a substrate and generates read data of the print image; and an analyzing device that analyzes the read data, wherein the reading device comprises: an image sensor; an imaging lens that forms an optical image of the print image on the image sensor, the imaging lens defining a field of view that represents a range in which an illumination device that directly incidents illumination light is disposed; a transmitted illumination device that is disposed at a position opposite the light receiving surface of the image sensor, the transmitted illumination device including a transmitted bright-field illumination device disposed within the field of view of the imaging lens and a transmitted dark-field illumination device disposed outside the field of view of the imaging lens; a transmitted illumination condition setting unit that sets transmitted illumination conditions to be applied to the transmitted illumination device; and one or more first processors, wherein the transmitted illumination condition setting unit sets transmitted bright-field illumination conditions to be applied to the transmitted bright-field illumination device and sets transmitted dark-field illumination conditions to be applied to the transmitted dark-field illumination device in accordance with processing performed on the read data, The one or more first processors control each of the transmitted light brightfield illumination device and the transmitted light darkfield illumination device in accordance with the transmitted light illumination conditions set using the transmitted light illumination condition setting unit.

19. The inspection device described in claim 18, wherein the transmitted illumination condition setting unit determines two or more combinations of illumination conditions of the transmitted brightfield illumination device and the transmitted darkfield illumination device, and sets the combination of illumination conditions of the transmitted brightfield illumination device and the transmitted darkfield illumination device according to the reading conditions of the image sensor, and the analysis device analyzes multiple read data generated by applying multiple mutually different illumination conditions when performing one type of analysis processing.

20. The inspection device described in claim 18, wherein the transmitted illumination condition setting unit sets a first transmitted illumination condition and a second transmitted illumination condition different from the first transmitted illumination condition for reading one of the printed images, the one or more processors switch between the first transmitted illumination condition and the second transmitted illumination condition when reading one of the printed images, the image sensor generates first read data to which the first transmitted illumination condition is applied, and generates second read data to which the second transmitted illumination condition is applied, and the analysis device analyzes the same number of read data as the number of multiple illumination conditions when performing one type of analysis processing.

21. The inspection device according to claim 20, wherein the analysis device performs a magnification change process on the read data in the transport direction of the base material.

22. The inspection device described in claim 18, wherein the transmitted dark field illumination device comprises a first transmitted dark field illumination device that emits illumination light in a first direction, and a second transmitted dark field illumination device that emits illumination light in a second direction different from the first direction, the transmitted illumination condition setting unit sets a first transmitted dark field illumination condition in which either the first transmitted dark field illumination device or the second transmitted dark field illumination device is turned on, or a second transmitted dark field illumination condition in which the first transmitted dark field illumination device and the second transmitted dark field illumination device are turned on, and the analysis device analyzes the read data to detect defects in the printed image.

23. An inspection device as described in claim 18, comprising: a reflective lighting device arranged on the same side as the image sensor with respect to a space divided in two by a plane perpendicular to the optical axis of the imaging lens at the reading position of the image sensor, the reflective lighting device irradiating illumination light to the base material supported at the reading position; a reflective lighting condition setting unit setting reflective lighting conditions to be applied to the reflective lighting device; and one or more second processors controlling the reflective lighting device in accordance with the reflective lighting conditions, wherein the reflective lighting device comprises a first reflective lighting device that emits illumination light in a third direction, and a second reflective lighting device that emits illumination light in a fourth direction different from the third direction, the reflective lighting condition setting unit setting a first reflective lighting condition for turning on either the first reflective lighting device or the second reflective lighting device, or a second reflective lighting condition for turning on the first reflective lighting device and the second reflective lighting device, and the analysis device analyzing the reading data to detect defects in the printed image.

24. The inspection device described in claim 18, wherein the one or more first processors adjust the amount of light emitted by the transmitted dark field illumination device so that the maximum pixel value in the read data of an ink-applied area of ​​the transparent substrate, where the amount of ink per unit area is equal to or less than a specified amount, exceeds the pixel value of an ink-not applied area of ​​the substrate, and the analysis device analyzes the read data to detect defects in the printed image.

25. A printing device; and a reading device that reads a printed image printed on a substrate by the printing device, the reading device comprising: an image sensor that reads the printed image and generates read data of the printed image; an imaging lens that forms an optical image of the printed image on the image sensor, the imaging lens defining a field of view that represents a range in which an illumination device that directly incidents illumination light is disposed; a transmitted illumination device that is disposed at a position facing the light receiving surface of the image sensor, the transmitted illumination device including a transmitted bright-field illumination device disposed within the field of view of the imaging lens and a transmitted dark-field illumination device disposed outside the field of view of the imaging lens; a transmitted illumination condition setting unit that sets transmitted illumination conditions to be applied to the transmitted illumination device; and one or more first processors, the transmitted illumination condition setting unit setting transmitted bright-field illumination conditions to be applied to the transmitted bright-field illumination device and setting transmitted dark-field illumination conditions to be applied to the transmitted dark-field illumination device in accordance with processing performed on the read data, A printing system in which the one or more first processors control each of the transmitted light brightfield illumination device and the transmitted light darkfield illumination device in accordance with transmitted light conditions set using the transmitted light condition setting unit.

26. An image sensor that reads a print image printed on a substrate and generates read data of the print image; an imaging lens that forms an optical image of the print image on the image sensor, the imaging lens defining a field of view that represents a range in which an illumination device that directly inputs illumination light is positioned; a transmitted illumination device that is positioned opposite the light receiving surface of the image sensor and includes a light diffusing member and a switching member that switches between a ratio of emitted light that is incident on the light diffusing member and output within the field of view of the imaging lens and a ratio of emitted light that is not incident on the light diffusing member and output from outside the field of view of the imaging lens; a transmitted illumination condition setting unit that sets transmitted illumination conditions to be applied to the transmitted illumination device; and one or more first processors, wherein the transmitted illumination condition setting unit sets transmitted bright field illumination conditions to be applied to transmitted bright field illumination light that is output within the field of view of the imaging lens and sets transmitted dark field illumination conditions to be applied to transmitted dark field illumination light that is output from outside the field of view of the imaging lens in accordance with processing performed on the read data, The one or more first processors are configured to control each of the transmitted bright-field illumination light and the transmitted dark-field illumination light in accordance with a transmitted illumination condition set using the transmitted illumination condition setting unit.

Images