Test pattern, imaging control program, and printing system

Abstract

To reduce an error in an adjustment value of a printing density due to peripheral dimming occurring in a captured image.SOLUTION: A test pattern is used for imaging by an imaging section of an information terminal to adjust printing characteristics of a printing device that includes a recording head. A density pattern for adjusting printing density, as one of the printing characteristics, is included in an imaging target region of the test pattern. An arrangement region of the density pattern within the imaging target region is symmetrical with respect to at least one of a center of the imaging target region and a straight line passing through the center as the reference.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a test pattern for adjusting print characteristics, an imaging control program for imaging the test pattern, and a printing system. [Background technology]

[0002] 2. Description of the Related Art Test patterns for adjusting the printing characteristics of printing devices such as inkjet printers are read by scanners. Patent Document 1 discloses an image printing system that creates a print correction table by using a digital camera to photograph a color matching test pattern printed by a printer. This document describes that if the digital camera has an automatic zoom function, the system will automatically zoom to a position where peripheral light intensity at the lens is at a level where it does not pose a problem before photographing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-136603 Summary of the Invention [Problem to be solved by the invention]

[0004] The structure of the lens can cause vignetting in captured images. This is particularly true when using a thin information terminal such as a smartphone for capturing images, as the space available for the image capture unit is limited. Furthermore, if zooming is performed to a level where vignetting is not an issue, the entire test pattern cannot be captured at once, and the test pattern must be captured multiple times. This results in time-consuming adjustment of the print density and requires a large amount of memory to store the captured images. [Means for solving the problem]

[0005] The test pattern of the present invention is a test pattern used for imaging by an imaging unit of an information terminal in order to adjust the printing characteristics of a printing device equipped with a recording head, a density pattern for adjusting print density as the printing characteristic is included in the imaging target area of ​​the test pattern; The density pattern arrangement area relative to the imaging target area is symmetrical with respect to at least one of the center of the imaging target area and a straight line passing through the center.

[0006] An imaging control program according to the present invention is an imaging control program for causing an imaging unit to capture an image of a test pattern for adjusting print characteristics of a printing device having a recording head, the program comprising: an imaging target area of ​​the test pattern includes a density pattern for adjusting print density as the printing characteristic; an arrangement area of ​​the density pattern with respect to the imaging target area is symmetrical with respect to at least one of a center of the imaging target area and a straight line passing through the center; The imaging control program a determination function for determining whether or not an imaging condition is satisfied, the condition including at least a condition that the center of the imaging target area is within a predetermined central area in the angle of view of the imaging unit; and an imaging control function of acquiring a captured image by causing the imaging unit to capture an image of the imaging target area when the imaging condition is satisfied.

[0007] Furthermore, a printing system of the present invention is a printing system including a printing device including a recording head, and an information terminal that captures an image of a test pattern for adjusting the printing characteristics of the printing device, an imaging target area of ​​the test pattern includes a density pattern for adjusting print density as the printing characteristic; an arrangement area of ​​the density pattern with respect to the imaging target area is symmetrical with respect to at least one of a center of the imaging target area and a straight line passing through the center; The information terminal An imaging unit; a control unit including a memory for storing an image obtained from the imaging unit and causing the imaging unit to capture an image of the imaging target area; The control unit has a configuration in which it determines whether or not imaging conditions are satisfied, the imaging conditions including at least a condition that the center of the imaging target area is within a predetermined central area in the angle of view of the imaging unit, and acquires the captured image by causing the imaging unit to capture the imaging target area using the satisfaction of the imaging conditions as a trigger. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram schematically illustrating an example of a printing system. [Figure 2] FIG. 1 is a diagram schematically illustrating an example of the configuration of a printing system. [Figure 3] FIG. 10 is a diagram schematically showing an example of a test pattern. [Figure 4] 4A to 4C are diagrams schematically showing other examples of test patterns. [Figure 5] FIG. 2 is a diagram schematically illustrating an example of a recording head and density patterns in a serial printing device. [Figure 6] FIG. 10 is a diagram schematically illustrating an example of the operation of an information terminal during imaging. [Figure 7] 10A and 10B are diagrams schematically showing examples of captured images of test patterns and density values ​​obtained from the density patterns. [Figure 8] 10 is a flowchart schematically illustrating an example of an imaging control process. [Figure 9] 10A and 10B are diagrams showing examples of whether or not the condition that the center of the imaging target area is included in the central area of ​​the angle of view is satisfied. [Figure 10] 10 is a flowchart illustrating an example of an adjustment process. [Figure 11] FIG. 10 is a diagram schematically showing an example of acquiring an adjustment value G3i. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes embodiments of the present invention. Of course, the following embodiments are merely examples of the present invention, and not all of the features shown in the embodiments are necessarily essential to the solution of the invention.

[0010] (1) Summary of the aspects included in the present invention: First, an overview of the embodiments included in the present invention will be described with reference to the examples shown in Figures 1 to 11. Note that the figures in this application are diagrams showing schematic examples, and the magnifications in each direction shown in these figures may differ, and the figures may not be consistent with each other. Of course, each element of the present embodiment is not limited to the specific example indicated by the symbol. In the "Outline of the embodiments included in the present invention," the words in parentheses indicate supplementary explanations for the immediately preceding words.

[0011] [Aspect 1] 1, 3, etc., a test pattern TP0 according to one embodiment is a test pattern TP0 used for imaging by the imaging unit 120 of an information terminal 1 in order to adjust the printing characteristics of a printing device 2 equipped with a recording head 220, and a density pattern DP0 for adjusting the printing density as the printing characteristic is included in an imaging target area AR0 of the test pattern TP0. A placement area AR1 of the density pattern DP0 relative to the imaging target area AR0 is symmetrical with respect to at least one of a center CT1 of the imaging target area AR0 and a straight line (for example, an axis of symmetry AX0) passing through the center CT1.

[0012] As a result, even if vignetting occurs in the captured image IM0, the effect of vignetting on the print density adjustment value (for example, adjustment value G3i shown in FIG. 11) can be reduced based on the captured image IM0 of the symmetrically arranged density pattern DP0. Therefore, the above aspect can provide a test pattern that can reduce errors in the print density adjustment value due to vignetting that occurs in the captured image.

[0013] There are various examples of the above-described aspects. Examples of the imaging target area include the entire medium, an area partitioned by a plurality of position detection patterns, and the like. The density pattern arrangement area relative to the imaging target area may be line symmetric with respect to a line passing through the center of the imaging target area, or may be point symmetric with respect to the center of the imaging target area. A test pattern refers to a medium that has at least a density pattern. Of course, the above remarks also apply to the following aspects.

[0014] [Aspect 2] As illustrated in FIG. 3 and other figures, the imaging target area AR0 may be rectangular. The test pattern TP0 may have position detection patterns MK0 at the four corners of the imaging target area AR0. The straight line (AX0) may be an axis of symmetry AX0 oriented along a side of the rectangle (e.g., vertical sides S1, S2 or horizontal sides S3, S4). The placement area AR1 of the density pattern DP0 relative to the imaging target area AR0 may be line-symmetric with respect to the axis of symmetry AX0. In the above cases, it is possible to provide a suitable test pattern for reducing errors in the print density adjustment value due to vignetting that occurs in the captured image. Although not included in the above-mentioned mode 2, the case where the test pattern TP0 does not have the position detection pattern MK0 and the entire medium having at least the density pattern DP0 is the imaging target area AR0 is also included in the disclosure of this application.

[0015] [Aspect 3] 3 and 4A, there may be a plurality of density patterns DP0. The plurality of density patterns DP0 may include a first pattern DP1 and a second pattern DP2 having the same shape. The arrangement area of ​​the first pattern DP1 and the arrangement area of ​​the second pattern DP2 may be symmetrical with respect to at least one of the center CT1 and the straight line (AX0). In the above cases, it is also possible to provide a suitable test pattern for reducing errors in the print density adjustment value due to vignetting that occurs in the captured image. Here, the terms "first," "second," etc. in this application are terms for distinguishing between elements among a plurality of elements having similarities, and do not indicate an order. This term also applies to the following aspects.

[0016] [Aspect 4] As illustrated in Figures 4B and 4C, the density pattern DP0 may be located in a position that includes the center CT1 in the imaging target area AR0, and the placement area AR1 of the density pattern DP0 may be symmetrical with respect to at least one of the center CT1 and the straight line (AX0). In the above cases, it is also possible to provide a suitable test pattern for reducing errors in the print density adjustment value due to vignetting that occurs in the captured image.

[0017] [Aspect 5] As illustrated in Figure 3, the imaging target area AR0 may be a rectangle having long sides (e.g., vertical sides S1 and S2) and short sides (e.g., horizontal sides S3 and S4). The straight line (AX0) may be an axis of symmetry AX1 oriented along the short sides (S3 and S4). The placement area AR1 of the density pattern DP0 relative to the imaging target area AR0 may be line-symmetric with respect to the axis of symmetry AX1. In the above cases, since the density pattern DP0 is not divided by the axis of symmetry AX0 in the direction along the short sides (S3, S4), the density pattern DP0 can be made longer in the direction along the short sides (S3, S4). Therefore, the above embodiment can also provide a suitable test pattern for reducing errors in the print density adjustment value due to vignetting that occurs in the captured image.

[0018] [Aspect 6] As illustrated in Figure 3, the test pattern TP0 may have an imaging direction display pattern IP1 that indicates the imaging direction so that the imaging by the imaging unit 120 is performed with the long sides (S1, S2) facing up or down. In the above cases, the user can understand the orientation of the test pattern TP0 at the time of shooting by looking at the imaging direction indication pattern IP1. Therefore, the above embodiment can provide a suitable test pattern for reducing errors in the print density adjustment value due to vignetting that occurs in the captured image.

[0019] [Aspect 7] 2 and 8, an imaging control program PR0 according to one embodiment is an imaging control program PR0 that causes the imaging unit 120 to capture a test pattern TP0 for adjusting the printing characteristics of a printing device 2 equipped with a recording head 220, and causes a determination function FU1 and an imaging control function FU2 to be implemented in a computer (e.g., information terminal 1). The determination function FU1 determines whether imaging conditions are met, including at least a condition that the center CT1 of the imaging target area AR0 is within a predetermined central area CA1 within the angle of view FA of the imaging unit 120 (also referred to as a positioning condition). The imaging control function FU2, triggered by the imaging condition being met, causes the imaging unit 120 to capture an image of the imaging target area AR0, thereby obtaining a captured image IM0.

[0020] The placement area AR1 of the density pattern DP0 relative to the imaging target area AR0 of the test pattern TP0 is symmetrical with respect to at least one of the center CT1 of the imaging target area AR0 and the line (AX0) passing through the center CT1. The imaging target area AR0 is captured when the center CT1 of the imaging target area AR0 of the test pattern TP0 falls within the central area CA1 of the angle of view FA of the imaging unit 120. Therefore, even if vignetting occurs in the captured image IM0, the effect of vignetting on the print density adjustment value (G3i) can be reduced based on the captured image IM0 of the symmetrically placed density pattern DP0. Therefore, the above aspect can provide a test pattern imaging control program that can reduce errors in the print density adjustment value due to vignetting that occurs in the captured image.

[0021] There are various examples of the above-described aspects. Acquiring a captured image may involve storing the captured image obtained from the imaging unit in memory, or may involve controlling a DMA (Direct Memory Access) controller to store the captured image in memory, etc. Storing in memory includes storing in RAM (Random Access Memory), storing in non-volatile memory, etc. The angle of view means the imaging range. Of course, the above remarks also apply to the following aspects.

[0022] [Aspect 8] 1 and 2, a printing system SY1 according to one embodiment includes a printing device 2 including a recording head 220, and an information terminal 1 that captures a test pattern TP0 for adjusting the printing characteristics of the printing device 2. The information terminal 1 includes an imaging unit 120 and a control unit 110 that includes memory (e.g., RAM 113) for storing a captured image IM0 obtained from the imaging unit 120 and causes the imaging unit 120 to capture an image of the imaging target area AR0. The control unit 110 determines whether imaging conditions are satisfied, including at least a condition that the center CT1 of the imaging target area AR0 is within a predetermined central area CA1 within the angle of view FA of the imaging unit 120, and, when the imaging conditions are satisfied, causes the imaging unit 120 to capture an image of the imaging target area AR0, thereby acquiring the captured image IM0. Aspect 8 above can provide a printing system that can reduce errors in print density adjustment values ​​caused by vignetting that occurs in captured images.

[0023] [Aspect 9] 3 and the like, the density pattern DP0 may include a first pattern portion PP1 and a second pattern portion PP2 whose arrangement areas are symmetrical with respect to at least one of the center CT1 and the straight line (AX0). The printing system SY1 may determine the print density adjustment value (G3i), as illustrated in FIG. 11, based on an average value (e.g., average value Ai) of a first value (e.g., density value Aei) obtained from the first pattern portion PP1 included in the captured image IM0 and a second value (e.g., density value Afi) obtained from the second pattern portion PP2 included in the captured image IM0. By averaging the first value (Aei) obtained from the first pattern portion PP1 included in the captured image IM0 and the second value (Afi) obtained from the second pattern portion PP2 included in the captured image IM0, the error in the print density adjustment value (G3i) due to vignetting occurring in the captured image IM0 is reduced. Therefore, the above embodiment can provide a printing system suitable for reducing the error in the print density adjustment value due to vignetting occurring in the captured image. Note that the adjustment value (G3i) may be determined by the control unit 110 or the printing device 2.

[0024] Furthermore, the above-described aspects are applicable to a computer-readable non-transitory medium on which the above-described imaging control program is recorded, the above-described information terminal, a control method for the information terminal, a printing method implemented by the above-described printing system, a control program for the above-described printing system, a computer-readable non-transitory medium on which the control program is recorded, etc. Any of the above-described devices may be composed of multiple distributed parts.

[0025] (2) Example of imaging control program: Fig. 1 schematically illustrates a printing system SY1 including an information terminal 1 and a printing device 2. Fig. 2 schematically illustrates the configuration of the printing system SY1. Figs. 3, 4A to 4C schematically illustrate a test pattern TP0. Examples of the information terminal 1 include a mobile phone such as a smartphone, a tablet terminal, a digital camera, etc. The information terminal 1 may be composed of multiple devices separated so that they can communicate with each other, or may be a stationary device with an imaging unit connected to it so that its position can be changed. The printing device 2 is assumed to be an inkjet printer equipped with a recording head 220 capable of ejecting droplets 280. Of course, the printing device 2 may also be a thermal printer (including a thermal transfer printer) equipped with a thermal head as a recording head, an electrophotographic printer (e.g., a laser printer) equipped with a recording head that deposits toner on the medium ME0, a three-dimensional printer, etc. The printing device 2 may be composed of multiple devices separated so that they can communicate with each other.

[0026] The printing device 2 can form a print image PI0 on a medium ME0, including a density pattern DP0 for adjusting the printing density of the printing device 2. A user US1 can adjust the printing characteristics of the printing device 2 by capturing a test pattern TP0 using an information terminal 1 equipped with an imaging unit 120. The captured image IM0 may exhibit vignetting due to the structure of the imaging unit 120. Vignetting, also known as vignetting, is a phenomenon in which light passing through the center of the lens during imaging is bright and becomes darker as it moves away from the center. This phenomenon can cause the periphery of the captured image IM0 to become darker. In particular, when the information terminal 1 is a thin device such as a smartphone, vignetting is more likely to occur due to the limited space available for the imaging unit 120. Furthermore, for devices that are not thin, vignetting still occurs, although to a lesser extent than for thin devices. Therefore, the placement area AR1 of the density pattern DP0 included in the test pattern TP0 shown in FIG. 3 is symmetrically arranged to accommodate vignetting. The placement area AR1 of the density pattern DP0 is symmetrical with respect to at least one of the center CT1 of the imaging target area AR0 and the axis of symmetry AX0 passing through the center CT1. When a user US1 captures a test pattern TP0 while holding the information terminal 1 in his or her hand, the center CT1 of the imaging target area AR0 may be offset from the angle of view of the imaging unit 120, i.e., the center of the imaging range. Therefore, the imaging control program PR0 shown in FIG. 2 automatically causes the imaging unit 120 to capture an image when imaging conditions are met, thereby enabling the information terminal 1 to capture an appropriate test pattern TP0. The imaging conditions include at least a condition that the center CT1 of the imaging target area AR0 is within a predetermined central area CA1 within the angle of view FA. The information terminal 1 executing the imaging control program PR0 can be said to implement an auto-shutter system. Even if the information terminal 1 is not portable but is a stationary device, the imaging control program PR0 may be executed when the relative positional relationship with the test pattern TP0 changes.

[0027] The communication I / F (interface) 117 of the information terminal 1 is capable of communicating with the communication I / F 230 of the printing device 2. The information terminal 1 is capable of transmitting adjustment values ​​for printing characteristics and the like to the printing device 2 via the communication I / Fs 117 and 230. Upon receiving the adjustment values, the printing device 2 stores the adjustment values ​​and adjusts the printing characteristics based on the adjustment values. Communication via the communication I / Fs 117 and 230 may be wireless communication in accordance with wireless LAN (Local Area Network) standards or the like, wired communication, or even network communication such as the Internet.

[0028] 2 includes a control unit 110, a storage unit 114, an operation unit 115, a display unit 116, a communication I / F 117, and an imaging unit 120. The information terminal 1 may also include sensors SS1 and SS2 connected to the control unit 110. The control unit 110 includes a CPU (Central Processing Unit) 111, which is a processor, a ROM (Read Only Memory) 112, and a RAM (Random Access Memory) 113. The RAM 113 is an example of a memory for storing a captured image IM0 obtained from the imaging unit 120.

[0029] The storage unit 114 stores an imaging control program PR0 for imaging the test pattern TP0, etc. A nonvolatile semiconductor memory such as a flash memory may be used as the storage unit 114. The storage unit 114 may be removably attached to the main body of the information terminal 1. The display unit 116 displays a screen corresponding to the display information based on the display information. A liquid crystal display panel or the like may be used as the display unit 116. A touch panel or hard keys attached to the surface of the display unit 116 may be used as the operation unit 115. The display unit 116 displays a screen corresponding to the display information based on the display information.

[0030] The imaging control program PR0 causes the information terminal 1 to realize a judgment function FU1, an imaging control function FU2, and an adjustment value determination function FU3. The CPU 111 performs various processes by appropriately reading information stored in the storage unit 114 into the RAM 113 and executing the read program. The CPU 111 performs processes corresponding to the above-mentioned functions (FU1 to FU3) by executing the imaging control program PR0 read into the RAM 113. The information terminal 1 that executes the imaging control program PR0 performs a judgment step corresponding to the judgment function FU1, an imaging control step corresponding to the imaging control function FU2, and an adjustment value determination step corresponding to the adjustment value determination function FU3. The computer-readable medium that stores the imaging control program PR0 that causes a computer to realize the above-mentioned functions (FU1 to FU3) is not limited to the storage unit 114, and may be a recording medium external to the information terminal 1.

[0031] The imaging unit 120 includes a lens 121, an AF (autofocus) unit 122, an image sensor 123, and the like. The image sensor 123 converts an image of light incident via the lens 121 and the AF unit 122 into an electrical signal. The image sensor 123 in this specific example outputs digital data corresponding to the electrical signal of each light receiving element. The digital data is stored in the RAM 113 as a frame FR0 or a captured image IM0. The image sensor 123 may be a CMOS (Complementary Metal-Oxide Semiconductor) image sensor, a CCD (Charge Coupled Devices) image sensor, or the like.

[0032] The sensors SS1 and SS2 can be used to determine whether the imaging conditions are met. For example, the sensor SS1 may be a speed sensor that measures the moving speed of the imaging unit 120, or an acceleration sensor that measures the acceleration of the imaging unit 120. In this case, the magnitude of blur in the captured image IM0 can be detected based on the measurement value from the sensor SS1. The sensor SS2 may also be a distance sensor that measures the distance from the imaging unit 120 to the medium ME0. In this case, the distance from the imaging unit 120 to the medium ME0 can be detected based on the measurement value from the sensor SS2.

[0033] The printing device 2 ejects C (cyan) ink, M (magenta) ink, Y (yellow) ink, and K (black) ink as colorants from a recording head 220 as droplets 280 to form a print image PI0 corresponding to print data. The recording head 220 has multiple nozzles Nc capable of ejecting C ink droplets onto the medium ME0, multiple nozzles Nm capable of ejecting M ink droplets onto the medium ME0, multiple nozzles Ny capable of ejecting Y ink droplets onto the medium ME0, and multiple nozzles Nk capable of ejecting K ink droplets onto the medium ME0. C, M, Y, and K inks are supplied to the recording head 220 from ink cartridges Cc, Cm, Cy, and Ck, respectively. The recording head 220 ejects C, M, Y, and K droplets 280 from the nozzles Nc, Nm, Ny, and Nk, respectively, under the control of the controller 210. When the droplets 280 land on the medium ME0, ink dots are formed on the medium ME0. The printing device 2 also includes a drive unit that changes the relative positional relationship between the recording head 220 and the medium ME0 under the control of the controller 210, such as a transport unit 225 that transports the medium ME0 in a predetermined transport direction. As a result, a printed matter is obtained having a pattern of ink dots on the medium ME0 as a print image PI0. The material of the medium ME0 is not particularly limited, and may be paper, fabric, resin, metal, or the like. The shape of the medium ME0 may be a two-dimensional cut shape, a roll, or a three-dimensional shape.

[0034] The test pattern TP0 shown in FIG. 3 includes multiple density patterns DP0, multiple position detection patterns MK0, and an imaging direction indicator pattern IP1. The multiple density patterns DP0 are arranged vertically relative to the imaging target area AR0. Each position detection pattern MK0 is located at a corner C0 of a rectangle on the medium ME0 that includes the multiple density patterns DP0. When a position detection pattern MK0 is located at each of the four corners of the rectangle, the imaging target area AR0 becomes a rectangular area on the medium ME0 with each position detection pattern MK0 at its corner C0. In FIG. 3, the rectangular imaging target area AR0 with vertical sides S1 and S2 and horizontal sides S3 and S4 is indicated by a two-dot chain line. The position detection pattern MK0 can be a square ArUco marker, a triangular pattern, or other pattern with specific geometric characteristics. The imaging direction indicator pattern IP1 indicates the imaging direction. If there is no position detection pattern MK0 on the medium ME0, the medium ME0 itself becomes the imaging target area AR0. In this case, the medium ME0 is preferably cut like a cut sheet of paper, and is preferably, but not limited to, rectangular.

[0035] FIG. 3 shows a rectangular imaging target area AR0, with a symmetry axis AX1 along the horizontal sides S3 and S4 and a symmetry axis AX2 along the vertical sides S1 and S2. The symmetry axis AX0 collectively refers to the symmetry axes AX1 and AX2 and refers to an axis oriented along the sides (S1 to S4) of the rectangle. The intersection of the symmetry axes AX1 and AX2 is the center CT1 of the imaging target area AR0. The multiple density patterns DP0 shown in FIG. 3 include a first pattern DP1 and a second pattern DP2 of the same shape. The density patterns DP0 do not intersect with the symmetry axis AX1 along the horizontal sides S3 and S4, but do intersect with the symmetry axis AX2 along the vertical sides S1 and S2. The first pattern DP1 corresponds to the first pattern portion PP1 of the density pattern DP0, and the second pattern DP2 corresponds to the second pattern portion PP2 of the density pattern DP0. The areas where the first pattern DP1 and the second pattern DP2 are arranged are symmetrical with respect to the symmetry axis AX1 along the horizontal sides S3 and S4. The arrangement area of ​​the first pattern DP1 and the arrangement area of ​​the second pattern DP2 are also line-symmetric with respect to the symmetry axis AX2 along the vertical sides S1 and S2. As a result, the arrangement area of ​​the first pattern DP1 and the arrangement area of ​​the second pattern DP2 are point-symmetric with respect to the center CT1. The arrangement area AR1 of the density pattern DP0 with respect to the imaging target area AR0 can be said to be line-symmetric with respect to the symmetry axis AX0, and can also be said to be point-symmetric with respect to the center CT1. The fact that the placement area AR1 is symmetrical with respect to at least one of the center CT1 and the axis of symmetry AX0 means that attention is focused on the shape of the area. Therefore, when each density pattern DP0 includes multiple individual patterns, the multiple individual patterns in the first pattern DP1 and the multiple individual patterns in the second pattern DP2 do not need to be arranged symmetrically.

[0036] The test pattern TP0 shown in FIG. 4A includes multiple density patterns DP0, multiple position detection patterns MK0, and an imaging direction display pattern IP1. The multiple density patterns DP0 shown in FIG. 4A are arranged horizontally across the imaging target area AR0, do not intersect with the symmetry axis AX2 along the vertical sides S1 and S2, and intersect with the symmetry axis AX1 (see FIG. 3) along the horizontal sides S3 and S4. The first pattern DP1 corresponds to the first pattern portion PP1 of the density pattern DP0, and the second pattern DP2 corresponds to the second pattern portion PP2 of the density pattern DP0. The arrangement areas of the first pattern DP1 and the second pattern DP2 are line-symmetric with respect to the symmetry axis AX2 along the vertical sides S1 and S2. The arrangement areas of the first pattern DP1 and the second pattern DP2 are also line-symmetric with respect to the symmetry axis AX1 (see FIG. 3) along the horizontal sides S3 and S4. As a result, the arrangement areas of the first pattern DP1 and the second pattern DP2 are point-symmetric with respect to the center CT1.

[0037] In addition, when the imaging target area AR0 is a rectangle having long sides (vertical sides S1, S2) and short sides (horizontal sides S3, S4) as shown in FIGS. 3 and 4A, the arrangement area AR1 of the multiple density patterns DP0 relative to the imaging target area AR0 is preferably the example shown in FIG. 3 rather than the example shown in FIG. 4A. When the arrangement area AR1 of the multiple density patterns DP0 is bisected by the symmetry axis AX1 along the short sides (horizontal sides S3, S4), the density patterns DP0 are not divided by the symmetry axis AX0 in the direction along the short sides (horizontal sides S3, S4). As a result, when the arrangement area AR1 is bisected by the symmetry axis AX1, the density patterns DP0 can be elongated in the direction along the short sides (horizontal sides S3, S4). This further reduces errors in the print density adjustment value due to vignetting. This effect is particularly significant when the printing device 2 is a serial type and the main scanning direction is oriented along the short sides of the medium ME0.

[0038] 3 indicates the imaging direction so that imaging is performed by the imaging unit 120 with the long sides (vertical sides S1, S2) facing up and down. By looking at the imaging direction display pattern IP1, the user US1 can understand the orientation of the test pattern TP0 at the time of shooting.

[0039] The test pattern TP0 shown in FIG. 4B includes one density pattern DP0, multiple position detection patterns MK0, and an imaging direction indication pattern IP1. The density pattern DP0 shown in FIG. 4B is located at a position including the center CT1 in the imaging target area AR0, and intersects with the axis of symmetry AX1 along the horizontal sides S3 and S4 and also with the axis of symmetry AX2 (see FIG. 3) along the vertical sides S1 and S2. The longitudinal direction of the density pattern DP0 is along the axis of symmetry AX1 along the horizontal sides S3 and S4. The portion of the density pattern DP0 above the axis of symmetry AX1 corresponds to the first pattern portion PP1, and the portion below the axis of symmetry AX1 corresponds to the second pattern portion PP2. The arrangement regions of the first pattern portion PP1 and the second pattern portion PP2 are line-symmetrical with respect to the axis of symmetry AX1 along the horizontal sides S3 and S4. The arrangement regions of the first pattern portion PP1 and the second pattern portion PP2 are also line-symmetrical with respect to the axis of symmetry AX2 (see FIG. 3) along the vertical sides S1 and S2. As a result, the arrangement area of ​​the first pattern portion PP1 and the arrangement area of ​​the second pattern portion PP2 are point-symmetric with respect to the center CT1.

[0040] The test pattern TP0 shown in FIG. 4C includes one density pattern DP0, multiple position detection patterns MK0, and an imaging direction indication pattern IP1. The density pattern DP0 shown in FIG. 4C is located at a position including the center CT1 in the imaging target area AR0, and intersects with the axis of symmetry AX2 along the vertical sides S1 and S2 and also with the axis of symmetry AX1 (see FIG. 3) along the horizontal sides S3 and S4. The longitudinal direction of the density pattern DP0 is along the axis of symmetry AX2 along the vertical sides S1 and S2. The portion of the density pattern DP0 to the left of the axis of symmetry AX2 corresponds to the first pattern portion PP1, and the portion to the right of the axis of symmetry AX1 corresponds to the second pattern portion PP2. The arrangement areas of the first pattern portion PP1 and the second pattern portion PP2 are line-symmetrical with respect to the axis of symmetry AX2 along the vertical sides S1 and S2. The arrangement areas of the first pattern portion PP1 and the second pattern portion PP2 are also line-symmetrical with respect to the axis of symmetry AX1 (see FIG. 3) along the horizontal sides S3 and S4. As a result, the arrangement area of ​​the first pattern portion PP1 and the arrangement area of ​​the second pattern portion PP2 are point-symmetric with respect to the center CT1.

[0041] FIG. 5 schematically illustrates an example of a recording head 220 and density pattern DP0 when the printing device 2 is a serial printer. The recording head 220 has a nozzle array 221 on its nozzle surface. The nozzle array 221 is made up of multiple nozzles 222 arranged at a predetermined nozzle pitch in the arrangement direction D4, each nozzle 222 being capable of ejecting droplets 280 onto the medium ME0. Here, "nozzle" refers to a small hole from which droplets are ejected, and "nozzle array" refers to an array of multiple nozzles. The nozzle array 221 includes, for example, a nozzle array capable of ejecting C droplets 280, a nozzle array capable of ejecting M droplets 280, a nozzle array capable of ejecting Y droplets 280, and a nozzle array capable of ejecting K droplets 280. The serial printing device 2 includes a carriage 223 on which the recording head 220 is mounted, a carriage drive unit 224 including a servomotor, and a transport unit 225 also including a servomotor. The controller 210 controls the driving of the carriage drive unit 224 to move the carriage 223 back and forth along the main scanning direction D1, and controls the driving of the transport unit 225 to feed the medium ME0 in the feed direction D3. The main scanning direction D1 is a direction intersecting the arrangement direction D4 of the nozzles 222 in the nozzle row 221, for example, a direction perpendicular to the arrangement direction D4. FIG. 5 shows that the right direction is the forward direction D11 of the main scanning and the left direction is the return direction D12 of the main scanning. The feed direction D3 is a direction intersecting the main scanning direction D1, for example, a direction perpendicular to the main scanning direction D1. The sub-scanning direction D2 shown in FIG. 5 is the opposite direction to the feed direction D3. Although the carriage 223 shown in FIG. 5 does not move in the sub-scanning direction D2, a sub-scanning drive unit (not shown) may move the carriage 223 in the sub-scanning direction D2 to achieve sub-scanning.

[0042] For example, when the printing device 2 performs band printing, the print image PI0 is formed in band units in the order of the sub-scanning direction D2. FIG. 5 shows that a density pattern DP0 for adjusting the print density for each nozzle 222 in the nozzle row 221 is formed in band B1, and then the aforementioned density pattern DP0 is formed in band B3, leaving band B2 empty. Each density pattern DP0 has a raster RT0 corresponding to each nozzle 222 in the nozzle row 221. The print density of each nozzle 222 is expressed as the density of the dot row of the raster RT0. The order of the nozzles 222 corresponding to the raster RT0 of the density pattern DP0 in the sub-scanning direction D2 is the same for band B1 and band B3. Therefore, multiple density patterns DP0 are arranged in the sub-scanning direction D2. If the test pattern TP0 includes multiple position detection patterns MK0, etc., these may be formed in bands different from bands B1 to B3.

[0043] Next, an example of the operation of the information terminal 1 when capturing an image will be described with reference to Fig. 6. Normally, capturing an image is triggered by an operation on a shutter button included in the operation unit 115. Frames FR0 constituting the moving image VD0 are transferred from the image sensor 123 of the imaging unit 120 to the RAM 113 of the control unit 110 for each frame period. At this time, the CPU 111 may store the frames FR0 in the RAM 113, or a DMA controller (not shown) may store the frames FR0 in the RAM 113. Each frame FR0 represents a still image for each frame period, but may also contain information indicating a difference from the previous frame. Due to the processing capacity of the information terminal 1, each frame FR0 has a lower resolution than the captured image IM0. It can also be said that the frame FR0 has fewer pixels than the captured image IM0. The control unit 110 controls the AF unit 122 and the like based on the group of frames FR0. The control unit 110 may display each frame FR0 on the display unit 116.

[0044] When the user US1 presses or touches the shutter button, the operation unit 115 accepts the operation, and the operation unit 115 notifies the control unit 110 that the shutter button has been operated. The control unit 110 then issues an image capture instruction IS1 to the image capture unit 120, causing the image capture unit 120 to capture an image. A captured image IM0 generated by this image capture has a higher resolution than the frame FR0, and is stored in the RAM 113. Here again, the CPU 111 may perform the process of storing the captured image IM0 in the RAM 113, or a DMA controller (not shown) may perform the process of storing the captured image IM0 in the RAM 113. When the user US1 performs an operation to save the captured image IM0, the operation unit 115 accepts the operation and notifies the control unit 110 of a save instruction IS2. The control unit 110 then converts the captured image IM0 into a file FL0 format and saves it in the storage unit 114. That is, the storage unit 114 stores the file FL0. Examples of file formats include the JPEG (Joint Photographic Experts Group) format and bitmap format. The control unit 110 may accept settings such as the file format and the resolution of the captured image IM0 included in the file FL0 via the operation unit 115, and save the file FL0 in accordance with the settings in the storage unit 114. The control unit 110 may also automatically generate a file FL0 of the captured image IM0 and store it in the storage unit 114 when the captured image IM0 is stored in the RAM 113.

[0045] However, vignetting may occur in the captured image IM0 of the test pattern TP0. If the zoom is performed to a level where this vignetting is not a problem, the entire test pattern cannot be captured at once, and the test pattern TP0 must be captured multiple times. This results in a long time for adjusting the print density, and a large amount of memory is required to store the captured image IM0. Therefore, in this specific example, the density pattern DP0 is symmetrically arranged in the imaging target area AR0 to reduce errors in the print density adjustment value.

[0046] FIG. 7 shows a schematic diagram of the captured image IM0 of the test pattern TP0 and the density values ​​obtained from the density pattern DP0. FIG. 7 is merely a schematic diagram, and a certain nozzle array 221 of the print head 220 includes nozzles #1, #2, and #3 as nozzles 222. The first pattern DP1 of band B1 includes regions E11-E36, and the second pattern DP2 of band B3 includes regions F11-F36. In reality, the number of nozzles 222 included in the nozzle array 221 is far greater than three. The density pattern DP0 included in the captured image IM0 is a captured image of the density pattern DP0 included in the test pattern TP0, which is arranged vertically with the imaging direction indication pattern IP1 at the top, as shown in FIGS. 3 and 5. Therefore, the captured image IM0 is vertically long, the main scanning direction D1 is horizontal, and the sub-scanning direction D2 is vertical. When printing density pattern DP0, nozzle #1 ejects droplets 280 into the raster RT0 of regions E11 to E16 in band B1, and ejects droplets 280 into the raster RT0 of regions F11 to F16 in band B3. Therefore, dot rows of droplets 280 from nozzle #1 are formed in the rasters RT0 of regions E11 to E16 and F11 to F16. Furthermore, nozzle #2 ejects droplets 280 into the raster RT0 of regions E21 to E26 in band B1, and ejects droplets 280 into the raster RT0 of regions F21 to F26 in band B3. Therefore, dot rows of droplets 280 from nozzle #2 are formed in the rasters RT0 of regions E21 to E26 and F21 to F26. Furthermore, nozzle #3 ejects droplets 280 onto the raster RT0 of regions E31-E36 in band B1, and onto the raster RT0 of regions F31-F36 in band B3. Therefore, dot rows of droplets 280 from nozzle #3 are formed in the rasters RT0 of regions E31-E36 and F31-F36. For convenience of illustration, each of regions E11-E36 and F11-F36 is shown as a square, but the regions corresponding to each of the multiple nozzles 222 included in nozzle row 221 may be formed as a line along main scanning direction D1.

[0047] For ease of explanation, the density value of the raster RT0 in regions E11-E16 will be denoted as Ae1, the density value of the raster RT0 in regions E21-E26 as Ae2, the density value of the raster RT0 in regions E31-E36 as Ae3, the density value of the raster RT0 in regions F11-F16 as Af1, the density value of the raster RT0 in regions F21-F26 as Af2, and the density value of the raster RT0 in regions F31-F36 as Af3. Furthermore, let i be a variable that identifies the raster RT0 included in the first pattern DP1 and the second pattern DP2, and let Aei be the density value of the i-th raster RT0 in regions E11-E36, and Afi be the density value of the i-th raster RT0 in regions F11-F36. The density values ​​Aei and Afi are calculated based on pixel values ​​of the captured image IM0 obtained by capturing the density pattern DP0.

[0048] Vignetting occurs depending on the angle of view FA, i.e., the distance from the center of the captured image IM0. Figure 7 shows that the center CT1 of the imaging target area AR0 of the test pattern TP0 is aligned with the center of the captured image IM0. In this case, the raster RT0 of areas E31-E36 and F11-F16 is less affected by vignetting, while the raster RT0 of areas E11-E16 and F31-F36 is more affected by vignetting. Therefore, the areas E11-E16 and F11-F16 corresponding to nozzle #1 produce relatively dark density values ​​Ae1 and relatively bright density values ​​Af1. The areas E31-E36 and F31-F36 corresponding to nozzle #3 produce relatively bright density values ​​Ae3 and relatively dark density values ​​Af3. The areas E21-E26 and F21-F26 corresponding to nozzle #2 produce intermediate density values ​​Ae3 and intermediate density values ​​Af3. Therefore, in order to reduce the effect of vignetting on the print density adjustment value of each nozzle, it is possible to use the average value A1 = (Ae1 + Af1) / 2 of the density values ​​Ae1 and Af1, the average value A2 = (Ae2 + Af2) / 2 of the density values ​​Ae2 and Af2, and the average value A3 = (Ae3 + Af3) / 2 of the density values ​​Ae3 and Af3. In general, by using the average value Ai = (Aei + Afi) / 2 of the density values ​​Aei and Afi, it is possible to reduce the effect of vignetting on the print density adjustment value of the nozzle row 221.

[0049] Depending on the print density adjustment method, it is also possible to divide each raster RT0 into regions and calculate the average density value. For example, let j be the variable that identifies the region within raster RT0, let Aeij be the density value of region Eij, and let Afij be the density value of region Fij. By using the average value Aij = (Aeij + Afij) / 2 of the density values ​​Aeij and Afij, it is possible to reduce the effect of vignetting on the print density adjustment value of the recording head 220.

[0050] Incidentally, when capturing the test pattern TP0, there is a possibility that the center CT1 of the imaging target area AR0 may be displaced from the center of the angle of view of the imaging unit 120. Therefore, in this specific example, the imaging is automatically performed when imaging conditions are satisfied that include at least the condition that the center CT1 of the imaging target area AR0 is within a predetermined central area CA1 in the angle of view FA.

[0051] (3) Specific examples of imaging control processing: FIG. 8 schematically illustrates an example of the imaging control process performed by the control unit 110. Here, steps S102 to S106 correspond to the determination function FU1, and step S110 corresponds to the imaging control function FU2. Hereinafter, the word "step" may be omitted, and the step code may be shown in parentheses. The imaging control process begins when the control unit 110 receives an instruction to capture an image of the imaging target area AR0 via the operation unit 115. The instruction to capture an image may be an operation on the imaging instruction area displayed after the imaging control program PR0 is started, an operation on the shutter button, or an operation to start the imaging control program PR0. FIG. 9 schematically illustrates an example of whether or not the condition that the center CT1 of the imaging target area AR0 is within the central area CA1 of the angle of view FA is satisfied.

[0052] The user US1 starts the imaging control program PR0 and performs an operation to capture an image of the imaging target area AR0 of the test pattern TP0 with the information terminal 1 while pointing the imaging direction indication pattern IP1 shown in FIG. 3 upward. When the imaging control process starts by starting the imaging control program PR0, the control unit 110 determines whether a new frame FR0 has been transferred from the image sensor 123 to the RAM 113 (S102). The determination process of S102 is repeated until a new frame FR0 is transferred. The determination process of S102 can also be said to be a process of determining whether a new frame FR0 has been acquired from the imaging unit 120. When a new frame FR0 is transferred, the control unit 110 acquires the coordinates of the center CT1 of the imaging target area AR0 based on the frame FR0 (S104). The coordinates of the center CT1 can be obtained based on the coordinates of the four corners of the imaging target area AR0, for example, by averaging the coordinates of the four corners of the imaging target area AR0 in the frame FR0. Details of the processing of S104 will be described later together with the determination processing of S106.

[0053] After acquiring the coordinates of the center CT1, the control unit 110 determines whether the imaging conditions are met based on the coordinates of the center CT1 (S106). The imaging conditions include a positioning condition in which the center CT1 of the imaging target area AR0 is within a predetermined central area CA1 in the angle of view FA of the imaging unit 120, as shown in FIG. 9. The central area CA1 is an area slightly wider than the exact center of the angle of view FA, and is circular in FIG. 9. The central area CA1 is set within an allowable range for errors in the print density adjustment value due to vignetting. As the central area CA1 becomes narrower, errors in the print density adjustment value due to vignetting become smaller. If the imaging conditions are not met, the control unit 110 outputs guidance for meeting the imaging conditions, such as "Align the center of the test pattern with the center of the screen" (S108), and returns the process to S106. As a result, the processes of S102 to S108 are repeated until the imaging conditions are met, and the control unit 110 repeatedly acquires frame FR0 from the imaging unit 120 and repeatedly acquires the coordinates of the center CT1 of the imaging target area AR0. The guidance may be output as a display on the display unit 116, or as an audio output to an audio output unit (not shown), etc.

[0054] Here, the processing of S104 to S106 will be described in detail with reference to Fig. 9. Fig. 9 shows how frames FR1 to FR3 serving as frame FR0 are acquired in chronological order. As a prerequisite for acquiring the coordinates of the center CT1, an inclusion condition must be satisfied, that is, the imaging target area AR0 is included in the angle of view FA of the imaging unit 120. Whether or not the inclusion condition is satisfied can be determined by determining whether or not the imaging target area AR0 is completely included in the frame FR0 corresponding to the angle of view FA.

[0055] For example, suppose that medium ME0 has position detection patterns MK0 (see FIG. 3) at the four corners of imaging target area AR0. In this case, control unit 110 can determine that the inclusion condition is met if it can detect position detection patterns MK0 at four locations from frame FR0. Furthermore, control unit 110 can determine that the inclusion condition is not met if it cannot detect even one of the four position detection patterns MK0 from frame FR0. If the medium ME0 does not have a position detection pattern MK0, the medium ME0 itself becomes the imaging target area AR0. If the medium ME0 is rectangular, the control unit 110 can determine that the inclusion condition is met if it can detect multiple edges from the frame FR0 and detect a rectangle surrounded by two edges determined to be vertically oriented and two edges determined to be horizontally oriented. Since the medium ME0 included in the frame FR0 may be tilted, "vertical orientation" includes orientations that deviate from the strict vertical orientation within a predetermined allowable angle range, and "horizontal orientation" includes orientations that deviate from the strict horizontal orientation within a predetermined allowable angle range. Well-known rectangle recognition techniques, such as business card recognition, can be used to recognize the medium ME0 from the frame FR0.

[0056] As described above, the control unit 110 determines whether the inclusion condition is met based on the frame FR0 repeatedly acquired from the imaging unit 120. If the inclusion condition is not met, the control unit 110 may output guidance for meeting the inclusion condition in S108 shown in Fig. 8. Examples of outputting this guidance include displaying information such as "Please fit the entire test pattern within the screen" or outputting a voice.

[0057] Only a part of the imaging target area AR0 is included in the frame FR1 shown in Fig. 9. In this case, the control unit 110 determines that the imaging conditions including at least the positioning conditions are not satisfied. The entire imaging target area AR0 is included in the frame FR2 shown in Figure 9. In this case, the control unit 110 determines that the inclusion condition is met and calculates the coordinates of the center CT1 of the imaging target area AR0 by averaging the coordinates of the four corners of the imaging target area AR0 in the frame FR2. The control unit 110 then determines whether the center CT1 of the imaging target area AR0 is included in the central area CA1 of the angle of view FA. Because the center CT1 is not included in the central area CA1 of the frame FR2, the control unit 110 determines that the imaging conditions, including at least the alignment condition, are not met.

[0058] 9 includes the entire imaging target area AR0. Control unit 110 determines that the inclusion condition is met, and similarly calculates the coordinates of the center CT1 of imaging target area AR0, and determines whether the center CT1 of imaging target area AR0 is included in the central area CA1 of the angle of view FA. Because the center CT1 is included in the central area CA1 of frame FR3, control unit 110 determines that the imaging conditions, including at least the alignment condition, are met.

[0059] The imaging condition may be the alignment condition and a condition that at least an additional condition other than the alignment condition is satisfied. The additional condition may be at least one of the following: a second condition that the amount of change in the relative positional relationship between the imaging unit 120 and the medium ME0 is equal to or less than a reference change amount; a third condition that the imaging unit 120 is within a predetermined range facing the imaging target area AR0; a fourth condition that the amount of distortion indicating the distortion of the density pattern DP0 included in the frame FR0 is equal to or less than a reference distortion amount; a fifth condition that the amount of spacing corresponding to the spacing between the imaging unit 120 and the medium ME0 is equal to or less than a reference spacing amount; and a sixth condition that the amount of brightness indicating the brightness L of the background color of the medium ME0 is equal to or greater than a reference brightness amount.

[0060] When the imaging conditions are satisfied, the control unit 110 acquires the captured image IM0 by causing the imaging unit 120 to capture an image of the imaging target area AR0 (S110). At this time, the CPU 111 may store the captured image IM0 from the image sensor 123 in the RAM 113, or the DMA controller may store the captured image IM0 from the image sensor 123 in the RAM 113. The captured image IM0 has a higher resolution than the frame FR0. As described above, the control unit 110 acquires the captured image IM0 by causing the imaging unit 120 to capture an image of the imaging target area AR0 using the satisfaction of the imaging conditions including the positioning conditions as a trigger.

[0061] After acquiring the captured image IM0, the control unit 110 determines whether or not to save the captured image IM0 as a file FL0 (S112). For example, when the operation unit 115 accepts an operation to save the captured image IM0, the control unit 110 causes the storage unit 114 to store the captured image IM0 in the format of file FL0 (S114), and ends the imaging control process. That is, the storage unit 114 stores the file FL0. When the operation unit 115 accepts an operation to discard the captured image IM0, the control unit 110 ends the imaging control process without performing the saving process of S114. Furthermore, in S112, the control unit 110 may determine whether the test pattern TP0 included in the captured image IM0 is appropriate for adjusting the printing characteristics. In this case, the control unit 110 may perform the saving process of S114 if it determines that the test pattern TP0 is appropriate, or may return the process to S102 if it determines that the test pattern TP0 is inappropriate. This is because even if the imaging conditions are met, there is a time lag until the actual imaging. Furthermore, the control unit 110 may perform the process of S114 without performing the determination process of S112, so that the storage of the captured image IM0 in RAM 113 is used as a trigger to automatically generate a file FL0 for the captured image IM0 and store it in the storage unit 114.

[0062] The control unit 110 can obtain an adjustment value for adjusting the printing density of the printing device 2 based on the pixel values ​​of the density pattern DP0 contained in the captured image IM0, and can cause the printing device 2 to print an image with a density according to the adjustment value. FIG. 10 schematically shows an example of the adjustment process performed by the control unit 110. Here, steps S202 to S210 correspond to the adjustment value determination function FU3. The adjustment process starts when the control unit 110 receives an instruction to adjust the print density via the operation unit 115. The adjustment instruction may be an operation on the adjustment instruction area displayed after the imaging control process shown in FIG. 8 is completed, or may be an operation on the adjustment instruction area displayed immediately after the imaging control program PR0 is started. FIG. 11 schematically shows an example of acquiring the print density adjustment value G3i for the i-th nozzle 222.

[0063] When the adjustment process starts, the control unit 110 sets the same point of interest from multiple rasters RT0 for the first pattern portion PP1 and the second pattern portion PP2. Then, the control unit 110 acquires density values ​​Aei and Afi of the same point of interest based on pixel values ​​of the captured image IM0 of the density pattern DP0 (S202). In the example shown in Fig. 7, the density value Aei of the i-th raster RT0 of the first pattern DP1 is acquired as the first value, and the density value Afi of the i-th raster RT0 of the second pattern DP2 is acquired as the second value. After acquiring the density values ​​Aei and Afi, the control unit 110 calculates the average value Ai=(Aei+Afi) / 2 of the density values ​​Aei and Afi of the target area (S204).

[0064] After calculating the average value Ai, the control unit 110 determines a print density adjustment value G3i for the i-th nozzle 222 based on the average value Ai (S206). FIG. 11 illustrates a correspondence relationship CO1 between single-color densities G1i and G2i. Single-color density refers to the density of a single color, for example, C, M, Y, or K. In FIG. 11, the horizontal axis represents the input density G1i, and the vertical axis represents the output density G2i. The adjustment value G3i refers to a value for correcting the output for the density G1i from density G2i to density G1i, and can also be considered an input value that results in the output value being density G1i. The control unit 110 can obtain the adjustment value G3i that results in the output value being density G1i according to the correspondence relationship CO1 for each color.

[0065] After determining the adjustment value G3i, the control unit 110 determines whether the adjustment value G3i has been determined for all nozzles 222 in the nozzle row 221 (S208). If there are any remaining nozzles 222 for which the adjustment value G3i has not been determined, the control unit 110 repeats the processes of S202 to S208. If the adjustment value G3i has been determined for all nozzles 222, the control unit 110 sets the adjustment value G3i in the controller 210 of the printing device 2 (S210). Of course, the density pattern DP0 included in the captured image IM0 is not limited to the example shown in FIG. 3 and may be a density pattern DP0 such as those shown in FIGS. 4A to 4C. In either case, the print density adjustment value G3i can be determined based on the average value Ai of the density value Aei obtained from the first pattern portion PP1 included in the captured image IM0 and the density value Afi obtained from the second pattern portion PP2 included in the captured image IM0. Thereafter, when the control unit 110 causes the printing device 2 to print an image, the printing device 2 forms an image on the medium ME0 with a density according to the adjustment value G3i (S212). In this way, the control unit 110 can cause the printing device 2 to form a print image with a density according to the adjustment value G3i. Of course, the processing of S212 does not need to be performed immediately after the processing of S210.

[0066] The adjustment process may be performed by the controller 210 of the printing device 2. In this case, the controller 210 sets the adjustment value G3i itself by performing the adjustment value determination process of S202 to S210. Then, in S212, the controller 210 applies the adjustment value G3i to the image to be printed, thereby forming on the medium ME0 a print image PI0 with little error in print density due to vignetting.

[0067] As described above, even if vignetting occurs in the captured image IM0, the effect of vignetting on the print density adjustment value G3i can be reduced based on the captured image IM0 of the symmetrically arranged density pattern DP0. Therefore, this specific example reduces errors in the print density adjustment value due to vignetting that occurs in the captured image. User US1 can easily adjust the print density of the printing device 2 by capturing the test pattern TP0 with a portable information terminal 1, such as a camera-equipped mobile terminal.

[0068] (4) Variation: The present invention can be embodied in various modifications. For example, the above-described processes can be changed as appropriate, such as by changing the order of the processes, etc. For example, in the imaging control process of Fig. 8, even if the guidance output process of S108 is not performed, the effect of being able to capture an appropriate test pattern can be obtained. The information terminal 1 may accept an operation to set the size of the central area CA1 of the angle of view FA shown in Fig. 9 at the operation unit 115. This makes it possible to reduce errors in the print density adjustment value due to vignetting depending on the environment of the user US1, etc.

[0069] The placement area AR1 of the density pattern DP0 relative to the imaging target area AR0 does not need to be point-symmetric with respect to the center CT1, as long as it is line-symmetric with respect to the symmetry axis AX0. For example, as shown in FIG. 3, the first pattern DP1 and the second pattern DP2 are divided into upper and lower parts with respect to the symmetry axis AX1 along the horizontal sides S3 and S4. If the first pattern DP1 and the second pattern DP2 are both trapezoids with the left side longer than the right side, the placement area AR1 of the density pattern DP0 is not point-symmetric but line-symmetric with respect to the symmetry axis AX1. Also, as shown in FIG. 4B, the portion of the density pattern DP0 above the symmetry axis AX1 corresponds to the first pattern portion PP1, and the portion below the symmetry axis AX1 corresponds to the second pattern portion PP2. If the density pattern DP0 is a trapezoid with the left side longer than the right side, the placement area AR1 of the density pattern DP0 is not point-symmetric but line-symmetric with respect to the symmetry axis AX1.

[0070] Furthermore, the placement area AR1 of the density pattern DP0 relative to the imaging target area AR0 does not need to be line-symmetric about the axis of symmetry AX0, as long as it is point-symmetric about the center CT1. For example, as shown in FIG. 3, the first pattern DP1 and the second pattern DP2 are divided into upper and lower parts about the axis of symmetry AX1 along the horizontal sides S3 and S4. If the first pattern DP1 and the second pattern DP2 are both parallelograms that are not rectangular, the placement area AR1 of the density pattern DP0 will not be line-symmetric but will be point-symmetric about the center CT1. Also, as shown in FIG. 4B, the portion of the density pattern DP0 above the axis of symmetry AX1 corresponds to the first pattern portion PP1, and the portion below the axis of symmetry AX1 corresponds to the second pattern portion PP2. If the density pattern DP0 is a parallelogram that is not rectangular, the placement area AR1 of the density pattern DP0 will not be line-symmetric but will be point-symmetric about the center CT1.

[0071] (5) Conclusion: As described above, the present invention can provide various configurations that can reduce errors in print density adjustment values ​​due to vignetting that occurs in captured images. Of course, even in an embodiment that consists only of the components of the independent claims, the basic functions and effects described above can be obtained. Furthermore, it is possible to implement configurations in which the components disclosed in the above examples are substituted with each other or the combination is changed, or configurations in which the components disclosed in the publicly known techniques and the above examples are substituted with each other or the combination is changed, etc. The present invention also includes these configurations. [Explanation of symbols]

[0072] 1...information terminal, 2...printing device, 110...controller, 111...CPU, 113...RAM, 114...storage unit, 115...operation unit, 116...display unit, 120...imaging unit, 123...image sensor, 210...controller, 220...recording head, 221...nozzle array, 222...nozzle, 223...carriage, 224...carriage drive unit, 225...conveyance unit, 280...droplet, Aei, Afi...density value, Ai...average value, AR0...image capture target area, AR1...placement area, AX0, AX1, AX2...symmetry axis, C0...corner, CA1...central area, CT1...center, D1...main scanning direction, D2...sub-scanning direction, D3...feed direction , D4...arrangement direction, D11...forward direction, D12...return direction, DP0...density pattern, DP1...first pattern, DP2...second pattern, FA...angle of view, FR0...frame, FU1...judgment function, FU2...imaging control function, FU3...adjustment value determination function, G3i...adjustment value, IM0...captured image, IP1...imaging direction display pattern, ME0...medium, MK0...position detection pattern, PI0...printed image, PP1...first pattern section, PP2...second pattern section, PR0...imaging control program, RT0...raster, S1,S2...vertical side, S3,S4...horizontal side, SY1...printing system, TP0...test pattern, VD0...video.

Claims

1. A test pattern used for imaging by an imaging unit of an information terminal in order to adjust the printing characteristics of a printing device equipped with a recording head, a density pattern for adjusting print density as the printing characteristic is included in the imaging target area of ​​the test pattern; A test pattern in which the density pattern arrangement area relative to the imaging target area is symmetrical with respect to at least one of the center of the imaging target area and a straight line passing through the center.

2. the imaging target area is rectangular; the test pattern has position detection patterns at four corners of the imaging target area, the straight line is a symmetry axis oriented along a side of the rectangle, The test pattern according to claim 1 , wherein the arrangement area of ​​the density pattern with respect to the imaging target area is line-symmetric with respect to the axis of symmetry.

3. There are a plurality of the density patterns, the plurality of density patterns include a first pattern and a second pattern having the same shape; 3. The test pattern according to claim 1, wherein the area where the first pattern is arranged and the area where the second pattern is arranged are symmetrical with respect to at least one of the center and the straight line.

4. 3. The test pattern according to claim 1, wherein the density pattern is located at a position including the center in the imaging target area, and the density pattern arrangement area is symmetrical with respect to at least one of the center and the straight line.

5. the imaging target area is a rectangle having long and short sides, the straight line is a symmetry axis oriented along the short side, 2. The test pattern according to claim 1, wherein the arrangement area of ​​the density pattern with respect to the imaging target area is line-symmetric with respect to the axis of symmetry.

6. The test pattern according to claim 5 , further comprising an imaging direction display pattern that indicates an imaging direction such that the imaging unit captures the image with the long sides facing up or down.

7. An imaging control program for causing an imaging unit to capture an image of a test pattern for adjusting print characteristics of a printing device equipped with a recording head, an imaging target area of ​​the test pattern includes a density pattern for adjusting print density as the printing characteristic; an arrangement area of ​​the density pattern with respect to the imaging target area is symmetrical with respect to at least one of a center of the imaging target area and a straight line passing through the center; The imaging control program a determination function for determining whether or not an imaging condition is satisfied, the condition including at least a condition that the center of the imaging target area is within a predetermined central area in the angle of view of the imaging unit; an imaging control function of acquiring a captured image by causing the imaging unit to capture an image of the imaging target area when the imaging condition is satisfied, the imaging control program causing the computer to realize the imaging control function;

8. A printing system comprising a printing device including a recording head and an information terminal that captures an image of a test pattern for adjusting the printing characteristics of the printing device, an imaging target area of ​​the test pattern includes a density pattern for adjusting print density as the printing characteristic; an arrangement area of ​​the density pattern with respect to the imaging target area is symmetrical with respect to at least one of a center of the imaging target area and a straight line passing through the center; The information terminal An imaging unit; a control unit including a memory for storing an image obtained from the imaging unit and causing the imaging unit to capture an image of the imaging target area; The control unit determines whether or not imaging conditions are satisfied, including at least a condition that the center of the imaging target area is within a predetermined central area in the angle of view of the imaging unit, and acquires the captured image by causing the imaging unit to capture the imaging target area when the imaging conditions are satisfied.

9. the density pattern includes a first pattern portion and a second pattern portion whose arrangement regions are symmetrical with respect to at least one of the center and the straight line, The printing system according to claim 8, wherein the printing system determines the adjustment value of the print density based on an average value of a first value obtained from the first pattern portion included in the captured image and a second value obtained from the second pattern portion included in the captured image.

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