Image processing device, image processing method, measuring device, measuring method, and program

Abstract

Conventionally, measuring instruments with optical geometry conditions of 0 / 45 or 45 / 0 could not accurately measure patches recorded on metallic paper. [Solution] By placing a diffusion sheet between the metallic paper to be measured and the measuring means, the strong directional component of light is converted into a diffuse component, allowing even a measuring means that measures only diffuse light in a specific direction to measure patches on the metallic paper.

Description

Technical Field

[0001] The present invention relates to an image processing apparatus, an image processing method, a measuring apparatus, a measuring method, and a program for determining a correction value for recording on metallic paper having specular reflection using a measuring instrument for measuring diffused light in a specific direction.

Background Art

[0002] In commercial and industrial printing, when viewing a recorded object on a recording medium such as coated paper or glossy paper, it is common to view it while avoiding specularly reflected light. Therefore, it is common and widely used to use a measuring instrument with optical geometric conditions of 0 / 45 or 45 / 0 for measuring diffused light from a specific direction. Also, in commercial and industrial printing, various types of recording media are used, and it is necessary to accurately control the color even for recording media with different color development characteristics. In contrast, a method of measuring color patches recorded on various recording media and creating an ICC (International Color Consortium) profile has been adopted.

[0003] On the other hand, metallic paper is known as one of the special recording media. Metallic paper has specular reflection. That is, most of the light from the light source of the measuring instrument is specularly reflected, and there is little diffused light in directions other than the specular reflection direction. Therefore, a measuring instrument with optical geometric conditions of 45 / 0 or 0 / 45 for measuring diffused light in a specific direction cannot accurately measure the color recorded on metallic paper. Generally, when measuring the color recorded on metallic paper, an integrating sphere measuring instrument or a multi-angle measuring instrument is used.

[0004] Patent Document 1 discloses a method of specifying recording conditions using a multi-angle measuring instrument in a recording apparatus that records an image using a metallic coloring material. By this method, color reproducibility can be improved compared to the case where only measurement values measured from a specific direction are used.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2019-4322 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] As mentioned earlier, measuring instruments that measure diffuse light in a specific direction, such as those with optical geometric conditions 0 / 45 or 45 / 0, which are widely used in commercial industrial printing, cannot accurately measure color patches recorded on specularly reflective metallic paper. On the other hand, integrating sphere measuring instruments or multi-angle measuring instruments can be used, but these are very expensive instruments.

[0007] Furthermore, depending on the correspondence between the device values ​​in the measurement data and the measured values, it may not be possible to create an ICC profile. An ICC profile cannot be created when the correspondence is unusual, for example, when the brightness of the non-recorded area of ​​a recording medium where no image is recorded is lower than the brightness of any color in the recorded area where an image is recorded. Even if an ICC profile can be created, if the measurements are not accurate, the color matching accuracy may be low.

[0008] To address these challenges, the present invention aims to appropriately perform color matching for recording on metallic paper. [Means for solving the problem]

[0009] The present invention is a measuring means for measuring diffused light in a specific direction, comprising: measuring a patch recorded on metallic paper, which is a recording medium to be measured, with a diffusion sheet that converts a strongly directional component of light into a diffuse component placed between the metallic paper and the measuring means; and determining a correction value for recording an image on the metallic paper based on a color matching target value corresponding to the state and the measurement result of the patch by the measuring means. [Effects of the Invention]

[0010] According to the present invention, by converting the strongly directional component of the reflected light reflected by the diffusion sheet from the metallic paper into a diffusing component, even a measuring means that measures diffused light in a specific direction can measure patches recorded on metallic paper. [Brief explanation of the drawing]

[0011] [Figure 1] Schematic diagram of measurement using a measuring instrument with optical geometric conditions 45 / 0. [Figure 2] Schematic diagram of measurements using an integrating sphere detector and a multi-angle detector. [Figure 3] Cross-sectional view showing the internal structure of the recording device. [Figure 4] Configuration diagram of the recording system according to the first embodiment [Figure 5] This figure shows the recording process in the recording system according to the first embodiment. [Figure 6] Color matching settings screen [Figure 7] Diagram showing the color conversion sequence performed in conversion step 501. [Figure 8] Diagram showing the contents of the manuscript data [Figure 9] Diagram showing the color conversion flow of spot colors [Figure 10] Diagram showing the contents of the spot color library. [Figure 11] An illustrative diagram showing the overview of the measurement unit 304. [Figure 12] ICC Profile Creation Settings Screen [Figure 13] Diagram showing the ICC profile creation flow. [Figure 14] Experimental results of the first embodiment [Figure 15] A schematic diagram showing the distribution of measured values ​​when using a diffusion sheet. [Figure 16] Experimental combinations and experimental results of the second embodiment [Figure 17] A diagram showing the overlap of the color reproduction ranges of the first and second diffusion sheets. [Figure 18] Spot color adjustment settings screen [Figure 19] Figure showing the spot color adjustment flow [Figure 20] Figure showing the message when measuring a metallic type recording medium [Figure 21] Figure explaining the spot color adjustment patch [Figure 22] Figure showing the color reproduction of the color patch recorded on metallic paper [Figure 23] Figure showing the UI part for displaying notifications to the user

Mode for Carrying Out the Invention

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] ((First Embodiment)) FIG. 3 is a cross-sectional view showing the internal configuration of the recording apparatus of the present embodiment. The recording apparatus of the present embodiment is an inkjet recording apparatus, and is a line printer that performs so-called one-pass recording using a continuous sheet wound in a roll shape as a recording medium. One-pass recording is a recording method in which a recording medium is conveyed with respect to a fixed recording head, and an image is recorded by one relative scan between the recording head and the recording medium. On the other hand, multi-pass recording is known with respect to one-pass recording. Multi-pass recording is a recording method in which an image is recorded by a plurality of relative scans, such as the recording head scanning the recording medium a plurality of times. In the present embodiment, a line printer that performs one-pass recording will be described as an example, but the present invention is not limited thereto, and a printer using a multi-pass recording method may be used.

[0014] The recording apparatus includes a recording medium supply unit 300, a print unit 301, an ink supply unit 302, a drying unit 303, a measurement unit 304, and a recording medium discharge unit 305. The recording medium is conveyed by a conveyance mechanism including roller pairs and belts along a conveyance path from the recording medium supply unit 300 to the recording medium discharge unit 305, which is shown by thick solid lines in the figure, and is subjected to processing by each unit.

[0015] The recording medium supply unit 300 is a unit that stores and supplies continuous recording media wound in a roll. The continuous recording media are paper type, film type, and metallic type recording media that can be recorded by inkjet. In this embodiment, the corresponding metallic type recording media are metallic paper in which the measurement results at any position in the non-recording area are approximately the same, while metallic paper in which the measurement values ​​differ depending on the position on the recording medium, such as holograms, is excluded.

[0016] The print unit 301 is a unit for recording an image on a transported recording medium using a recording head. The print unit 301 is equipped with multiple transport rollers for transporting the recording medium. The recording head has nozzles arranged therein that are equipped with recording elements for applying ink to the recording medium. The recording head in this embodiment is a line-type recording head in which the nozzle row is formed to cover the maximum width of the recording medium that is expected to be used, and multiple recording heads are arranged parallel to each other along the transport direction. Inkjet methods that eject ink as droplets include methods that use a heating element, a piezoelectric element, an electrostatic element, or a MEMS element as the recording element in the nozzle. The recording head in this embodiment is capable of ejecting four colors of ink: cyan (C), magenta (M), yellow (Y), and black (BK). Ink is supplied from the ink supply unit 302 to the recording head via ink tubes corresponding to each color.

[0017] The drying unit 303 is a unit that heats the recording medium printed by the printing unit 301 to dry the ink applied to the recording medium in a short time. The drying unit 303 is equipped with a conveyor belt and conveyor rollers for sending the recording medium to the next process. The measuring unit 304 is equipped with a measuring instrument with an optical geometric condition of 0 / 45 that automatically measures the color patch printed by the printing unit 301. Details of the measuring unit 304 will be described later.

[0018] The recording medium discharge unit 305 includes a winding device that winds the dried recording medium into a roll and discharges the recording medium. The recording device control unit 306 is a unit that controls each part of the recording device. The recording device control unit 306 has a CPU, memory, a controller equipped with various I / O interfaces, and a power supply. The operation of the recording device is controlled based on commands from the controller, or from an image processing device 307 such as a host computer connected to the controller via an I / O interface. In this embodiment, a configuration in which the image processing device 307 is located outside the recording device is illustrated, but the image processing device 307 may also be located inside the recording device.

[0019] (Recording system configuration) Figure 4 shows the configuration of the recording system. The recording system of this embodiment comprises an image processing device 307 and a recording device 410. The image processing device 307 performs rasterization and color matching, issues recording instructions to the recording device 410, transfers information and data necessary for image processing, and performs conversion to a device-dependent color space. Data transfer between the image processing device 307 and the recording device 410 is performed via an interface such as a network, USB (Universal Serial Bus), or local bus. The image processing device 307 also comprises a UI unit 401, a working memory 402, a data input / output unit 403, a calculation unit 404, and a large-capacity storage unit 405.

[0020] The UI unit 401 is a user interface that receives various inputs from the user, including color settings, and displays necessary information to the user. The UI unit 401 is generally composed of input devices such as a keyboard and mouse and output devices such as an LCD display, but it may also be a touch panel with input / output functions, for example. The working memory 402 is a memory that provides the work area for the calculation unit 404, and is, for example, RAM (Random Access Memory). The data input / output unit 403 is an interface that inputs recording jobs and transfers data to the recording device 410.

[0021] The arithmetic unit 404 includes a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit), etc. The arithmetic unit 404 uses the working memory 402 to execute the software of the large-capacity storage unit 405. The arithmetic unit 404 instructs each part of the image processing device 307 to execute each step of the processing described below. This realizes the image processing of this embodiment. The large-capacity storage unit 405 is, for example, an HDD (Hard Disk Drive) and an SSD (Solid State Drive). In addition to software such as the OS and system programs, the large-capacity storage unit 405 stores data such as various setting values ​​and parameters necessary for various processes.

[0022] The recording device 410 comprises a data transfer unit 411, a recording control unit 412, an image processing unit 413, a large-capacity storage unit 414, and a recording engine 415. Recording jobs output from the image processing device 307 are received by the data transfer unit 411. Recording jobs include color-matched device CMYK data, recording setting information, etc. From the received recording jobs, the data transfer unit 411 sends the device CMYK data to the image processing unit 413 and the recording setting information to the recording control unit 412. The recording control unit 412 controls the operation of the recording engine 415 based on the recording setting information.

[0023] The recording engine 415 includes a recording head that ejects ink and a supply system that supplies ink to the recording head. The recording engine 415 performs ink ejection operations based on image data after a series of image processing operations have been performed by the image processing unit 413, which will be described later.

[0024] (Sequence of recording systems) Figure 5 shows the recording process in the recording system according to this embodiment. The original image data input to the image processing device 307 is RGB data defined by RGB luminance signal values, or CMYK data defined by CMYK ink usage. The file format of the original image corresponds to, but is not limited to, the Portable Document Format (hereinafter referred to as PDF).

[0025] In rendering step 500, the calculation unit 404 renders the original image data. After rendering the original image data, in color conversion step 501, the calculation unit 404 converts the image signal values ​​of the target object in the original image data to colors.

[0026] In the color conversion process 501, the calculation unit 404 converts the CMYK data and RGB data using the conversion parameters of the large-capacity storage unit 405, based on the color conversion information set in the UI unit 401. The color conversion is a color conversion using an ICC profile. The user sets the color conversion information via the color matching setting screen 600 shown in Figure 6 in the UI unit 401. On the color matching setting screen 600, the user sets the CMYK source profile 601, the CMYK rendering intent 602, the RGB source profile 603, the RGB rendering intent 604, and the output profile 605 for each recording medium. The output profile is an ICC profile that outputs CMYK, and is used in the color conversion process 501 to output CMYK data. The creation flow of the output profile for each recording medium used here will be described later. The output CMYK data is transmitted to the recording device 410.

[0027] In the color separation process 502, the image processing unit 413 converts the CMYK data received from the image processing device 307 into CMYK signal values ​​corresponding to the CMYK inks used by the recording device 410. At this time, the image processing unit 413 refers to a four-dimensional lookup table (hereinafter referred to as LUT) pre-stored in the large-capacity storage unit 414 and converts it into CMYK signal values ​​associated with the input CMYK signal values ​​in the LUT. Subsequently, the image processing unit 413 uses the CMYK signal values, which are the output values ​​obtained in the color separation process 502, in the gradation correction process 503.

[0028] In the gradation correction process 503, the image processing unit 413, when the data to be corrected is CMYK data, performs a linear conversion for each ink color so that the density of the colors represented on the sheet maintains a linear relationship with the input signal value. At this time, the image processing unit 413 refers to a one-dimensional LUT for each ink color that is pre-stored in the large-capacity storage unit 414.

[0029] In the quantization process 504, the image processing unit 413 converts the grayscale-corrected multi-level data into binary data, where "1" indicates the ejection of ink droplets (dots) for each ink color, and "0" indicates non-ejection. In the recording process 505, the recording engine 415 controls the ink ejection operation from the recording head based on the binary data.

[0030] (Color conversion sequence) Figure 7 shows the color conversion sequence in the color conversion process 501. Input_PDF701 is the original document data, which is intended to be recorded on metallic paper. Figure 8 shows the original document data 800 for recording on metallic paper, which is created as a PDF file. The original document data 800 includes a CMYK object 801 in CMYK data format, an RGB object 802 in RGB data format, and a spot color object 803 with color specified as spot color data. The spot color data includes the spot color name, the color space of the alternative color, the value of the alternative color, and the Tint value (0-100%).

[0031] In Input_PDF701, the RGB object 802 is converted to Lab data by the RGB source profile 702 and then to device CMYK data by the CMYK output profile 705. Similarly, the CMYK object 801 is converted to Lab data by the CMYK source profile 703 and then to device CMYK data by the CMYK output profile 705. The spot color object 803 is color-converted using the spot color library 704, which is pre-stored in the large-capacity storage unit 405.

[0032] Figure 9 shows the color conversion flow for spot colors. In step S901, the spot color name is obtained. In step S902, it is searched to see if the obtained spot color name is stored in the spot color library 704. Figure 10 shows the spot color library 704, which is a table that stores the information shown in this figure. For spot color name 1000, CIE-L*a*b*1001 and device CMYK1002 are stored. For registered spot color names, the CIE-L*a*b*1001, which is the color matching target value, is always registered. However, device CMYK1002 is not mandatory, and for spot colors where the user has adjusted the spot color and determined the optimal CMYK value, the CMYK data is stored.

[0033] In step S902, the system searches for a spot color name that matches the spot color name obtained in step S901 from among the 1000 spot color names. If no match is found, the system proceeds to step S903; if a match is found, the system proceeds to step S904. In step S903, the system proceeds to a color conversion process (a) where the spot color is converted to a color in the color space of the spot color's substitute color.

[0034] In step S904, it is checked whether data is stored in device CMYK1002 for a spot color name that matches the spot color name 1000. If device CMYK is not stored, proceed to step S905; otherwise, proceed to step S906. In step S905, proceed to processing flow (b) for color conversion in Lab, and the color is converted as Lab data. In step S906, proceed to flow (c) for outputting the stored device CMYK value. The stored device CMYK value is output as is without conversion using an output profile.

[0035] (Details of the measuring unit 304) Figure 1 is a schematic diagram of a measurement using a measuring instrument with optical geometry conditions of 45 / 0. Figure 1(a) shows the measurement of high-quality paper, one of the recording media, as the object of measurement. Light from a light source is shone from a 45-degree direction and is shown reflecting off the surface of the high-quality paper being measured. Because the surface of the high-quality paper has very fine irregularities, the reflected light does not reflect in one direction but diffuses and reflects in various directions. The sensor receives the reflected light that is diffused in the 0-degree direction and measures it.

[0036] Figure 1(b) shows a measurement of metallic paper. The surface of metallic paper is mirror-like, and light from a light source irradiated from a 45-degree direction is reflected almost specularly. The reflected light in this case is not diffused in the direction of the sensor at 0 degrees. Therefore, when measuring the non-recorded area of ​​metallic paper using a measuring instrument with optical geometry conditions of 45 / 0 or 0 / 45, the measured value will indicate that it is very dark, making accurate measurement impossible.

[0037] To accurately measure metallic paper, it is common to use integrating sphere measuring instruments or multi-angle measuring instruments, as shown in Figure 2. Figure 2(a) is a schematic diagram of measurement using an integrating sphere measuring instrument, which illuminates the object to be measured evenly from all directions using an integrating sphere or the like. Figure 2(b) is a schematic diagram of measurement using a multi-angle measuring instrument, which illuminates the object with a light source from a 45-degree direction and receives light with sensors at multiple reflection angles. With measuring instruments like those shown in Figure 2, it is possible to measure diffuse light with different reflection intensities depending on the angle, which is characteristic of metallic materials. Now, the details of the measuring unit 304 of this embodiment will be described.

[0038] Figure 11(a) is an illustrative diagram showing an overview of the measurement unit 304. 1100 indicates that the continuous recording medium on which the measurement color patch is recorded has been transported to the measurement unit in the printing unit 301. The measuring instrument 1101 is an optical geometry condition 45 / 0 measuring instrument capable of measuring diffuse light in a specific direction. The measuring instrument 1101 measures the color patch and obtains the CIE L*a*b* value. The measuring instrument 1101 has a mechanism that scans in a direction perpendicular to the direction in which the recording medium is transported (Y direction in the figure) (X direction in the figure), and can measure the color patch while scanning. The pressing mechanism 1102 is a mechanism that presses the recording medium. Immediately after the color patch is recorded in the printing unit 301, the recording medium contains a lot of moisture from the ink, so the drying unit 303 evaporates the moisture in the ink. However, it is not possible to completely remove the moisture, so depending on the type of recording medium, cockling may occur, resulting in an uneven surface shape. The measuring instrument assumes that the distance from the sensor to the object to be measured is within a specified range. If the cocking creates irregularities, the distance from the sensor to the object being measured changes, making accurate measurement impossible. Therefore, a pressing mechanism is used to press the recording medium and flatten the irregularities caused by the cocking.

[0039] As shown in Figure 11(b), the pressing mechanism 1102 has two windows for measurement. Measurement window 1103 is for measuring metallic paper and is fitted with a diffusion sheet that converts the strong directional component of light into a diffuse component. On the other hand, measurement window 1104 is for measuring recording media other than metallic paper and is not fitted with a diffusion sheet.

[0040] In this embodiment, measurement is performed using the measurement window located downstream of the pressing mechanism 1102 in the transport direction (upper in the figure), of the two measurement windows. The pressing mechanism 1102 in this embodiment is equipped with a mechanism to switch the position of the measurement window. Figure 11(b) shows the arrangement when measuring metallic paper, and Figure 11(c) shows the arrangement when measuring recording media other than metallic paper. Details of the mechanism to switch between the state in Figure 11(b) and the state in Figure 11(c) are omitted, but for example, it is configured to swap the positions of the measurement window 1103 with a diffusion sheet attached and the measurement window 1104 without a diffusion sheet attached by rotating it 180 degrees.

[0041] When transporting the recording medium, the pressing mechanism 1102 waits, separated from the recording medium. When transport stops for measurement, the pressing mechanism 1102 presses the recording medium, and the measuring instrument measures the row of color patches on the recording medium while scanning in the scanning direction. Once the measurement of the row of color patches to be measured is complete, the pressing mechanism 1102 separates from the recording medium. When the recording medium is intermittently fed and transported to a position where the next row of color patches can be measured, the next measurement operation begins.

[0042] (Creation of a spot color library specifically for metallic paper) Next, we will explain how to create a spot color library specifically for metallic paper. When performing color conversion for metallic paper, it is necessary to use a spot color library specifically for metallic paper. Using the same measuring instrument and diffusion sheet as the measurement unit 304, the metallic color samples that will be included in the spot color library are measured in advance and recorded in CIE-L*a*b*1001 of the spot color library shown in Figure 10 to create the library. In the initial stage of creating the library, the device CMYK1002 is left unset.

[0043] (ICC profile creation flow) Figure 12 shows the ICC profile creation dialog 1200. The image processing device 307 has a function to create an ICC profile for each type of recording medium. When the ICC profile creation function is activated via the UI unit 401, the ICC profile creation dialog 1200 is launched. The edit box 1201 is a box for entering the file name of the ICC profile to be created. The created ICC profile is stored in the default folder with the entered file name.

[0044] The profile description, which is to be included in the description tag of the ICC profile, is entered using edit box 1202. This is the content displayed when selecting output profile 605 in Figure 6. The recording medium name is selected using list box 1203. As shown in Figure 12(b), the names of recording media registered using the function for registering recording media (not shown) are displayed, and the selected recording medium name is displayed.

[0045] The type of recording medium is selected using list box 1204. The type of recording medium (recording medium type) selected in list box 1203 is selected from the list shown in Figure 12(c). There are three types of recording mediums: paper type, film type, and metallic type. If metallic paper is to be used, the metallic type is selected.

[0046] The type of patch to be used for creating the ICC profile is selected using list box 1205. The selection is made from the patch types shown in Figure 12(d).

[0047] Figure 13 is a flowchart showing the ICC profile creation flow. In step S1301, the file name of the ICC profile to be created is entered in the file name edit box 1201. In step S1302, the description is entered in the description edit box 1202. In step S1303, the name of the recording medium to be created is selected from the recording medium name list box 1203. In step S1304, the type of recording medium to be created is selected from the recording medium type list box 1204. In step S1305, the type of patch to be used to create the ICC profile is selected from the patch type list box 1205. In step S1306, when the execute button 1206 in Figure 12 is pressed, the creation of the ICC profile is initiated.

[0048] In step S1307, the patch selected in step S1305 is recorded using the printing unit 301. The recorded patch is transported to the measurement unit 304. In step S1308, it is determined whether the recording medium type selected in step S1304 is a metallic type. If a metallic type is selected, the process proceeds to step S1309; otherwise, the process proceeds to step S1310.

[0049] In step S1309, as shown in Figure 11(b), a diffusion sheet is placed in the measurement window on the downstream side of the recording medium of the pressing mechanism 1102 and switched. In the normal state, the pressing mechanism 1102 is in the state shown in Figure 11(c), and when the metallic type is selected, it switches to the state shown in Figure 11(b). In step S1310, the color patch is measured using the method described above. The measured data is sent to the working memory 402. In step S1311, an ICC profile is created by the calculation unit 404 using the measurement data on the working memory 402. The created ICC profile is stored in a default folder in the large-capacity storage unit 405.

[0050] (Characteristics and experimental results of the diffusion sheet) The inventors conducted experiments using the following eight types of diffusion sheets. (1) Clear film (transparent film) (2) One sheet of tracing paper (3) Two layers of tracing paper (4) One sheet of translucent film (5) Two layers of translucent film (6) Three layers of translucent film (7) Four layers of translucent film (8) Five layers of translucent film

[0051] Procedure 1: Color patches for creating an ICC profile were recorded using silver metallic paper as the recording medium. Then, measurements were obtained for each of the eight types of diffusion sheets mentioned above, and an ICC profile was created. The color patches include patches of the non-recorded area described later, and single-color patches of C, M, Y, and Bk. A single-color patch refers to a color patch recorded with only one type of ink, rather than recording with a combination of multiple types of inks. Single-color patches include single-color patches with multiple input values, including an input value of 100%. To measure the color patches, for example, a measuring instrument with optical geometry condition 45 / 0 for measuring diffuse light in a specific direction was used, and measurements were taken with one of the eight types of diffusion sheets placed on the silver metallic paper.

[0052] Step 2: Eight color swatches were sampled from commercially available metallic color charts, and measurements were taken for each using the eight types of diffusion sheets mentioned above to create a spot color library.

[0053] Step 3: Using each of the created ICC profiles and their corresponding spot color libraries, the color patches of the eight color swatches were color-converted, and the color conversion results of the eight types of diffuse sheets were recorded.

[0054] Step 4: To verify the matching accuracy, measurements were taken using an integrating sphere analyzer (SCI mode including specular reflection), which is considered to have a high correlation with human perception. The metallic color sample chart and each color patch recorded in Step 3 were measured with the integrating sphere analyzer, and the color difference was calculated.

[0055] Figure 14 is a graph showing the results of the above experiment. The bar graph shows the average ΔE00 of the color matching color difference for each diffusion sheet. In addition, the brightness ratio (W-K100 / Y100-K100) using the following three patches (W, K100, Y100) from the measurements taken using the diffusion sheet in Step 1 is also shown. W:(C,M,Y,K)=(0,0,0,0) K100:(C,M,Y,K)=(0,0,0,100%) Y100:(C,M,Y,K)=(0,0,100%,0) W is a patch in the non-recording area. K100 is one of the black single-color patches, and is the color patch when the input value K=100%. Similarly, Y100 is one of the yellow single-color patches, and is the color patch when Y=100%. In this experiment, a yellow single-color patch with an input value Y=100% was used, but it is not limited to an input value Y=100%; any amount of ink that covers the recording medium and makes the surface invisible is acceptable.

[0056] Figure 15 is a schematic diagram showing the distribution of measured values ​​for (1) "clear film", (2) "one sheet of tracing paper", (4) "one sheet of translucent film", and (6) "three layers of translucent film".

[0057] (1) The "clear film" has a brightness ratio of 0.09, indicating a low degree of light diffusion in the diffusion sheet. As a result, the reflection component in the specular reflection direction is large, and it can be seen that the brightness of patch W in the non-recording area of ​​the silver metallic paper is measured as low.

[0058] (4) The "single translucent film" has a brightness ratio of 0.32, and is more translucent and diffuses light more than the clear film. For this reason, although the brightness of patch W is measured to be slightly higher, it still shows a lower brightness than Y100.

[0059] (6) The "three layers of translucent film" has a brightness ratio of 1.00, and the degree of light diffusion is higher than that of a single layer of translucent film. Therefore, the brightness of patch W is almost the same as that of patch Y100.

[0060] (2) "One sheet of tracing paper" has a brightness ratio of 1.29 and a high degree of light diffusion, indicating that the brightness of patch W is higher than the brightness of Y100.

[0061] According to the matching color difference and lightness ratio data shown in Figure 14, diffuse sheets with low matching accuracy have a lightness ratio below 1.0. This is because when the lightness ratio falls below 1.0, color discrimination in the lightness direction becomes impossible, and colors with the same chromaticity but different lightness levels cannot be distinguished. On the other hand, sheets with a lightness ratio greater than 1.0 tend to have high matching accuracy. A lightness ratio greater than 1.0 means that the lightness of patch W, which is the non-recording area of ​​the metallic paper, is higher than the lightness of patch Y100.

[0062] Furthermore, in the experiment, we attempted to create an ICC profile by measuring color patches recorded on silver metallic paper using a measuring instrument with optical geometry conditions of 45 / 0 without using a diffusion sheet. However, since the measurement data for patch W in the non-recorded area of ​​the metallic paper was measured to be lower than the brightness of patch K100, we were unable to create an ICC profile.

[0063] As described above, we have explained how to create an ICC profile, one of the recording conditions when recording on metallic paper, using a measuring instrument with optical geometry condition 45 / 0 that can measure diffuse light in a specific direction. By measuring both the metallic color sample, which is the target value for color matching, and the color patch on the metallic paper using the same diffusion sheet, color matching can be achieved. Furthermore, the matching accuracy can be further improved by using a diffusion sheet that can measure the brightness of the non-recorded area of ​​the metallic paper at a higher level than the brightness of the yellow single-color patch.

[0064] In this embodiment, an example of attaching the diffusion sheet to the measurement window of the pressing mechanism has been described, but it is not limited to this. When measuring metallic paper, the diffusion sheet may be automatically attached to the aperture portion of the measuring instrument.

[0065] Furthermore, the present invention is not limited to a method of attaching a diffusion sheet to a measurement window, as long as the measurement can be performed using a diffusion sheet. For example, when measuring metallic paper, the user may place the diffusion sheet between the measuring instrument and the recording medium to be measured. In that case, as shown in Figure 23, the user is notified via the UI unit 401 to place the diffusion sheet between the metallic paper and the measuring instrument. When the user presses the OK button, the system determines that information indicating that the diffusion sheet has been placed has been input and starts the measurement. This makes it possible to perform measurements using a diffusion sheet without the device having to provide the diffusion sheet itself.

[0066] Furthermore, if the measurement results differ significantly from the expected value, the user may be notified accordingly. For example, this could be in the form of a notification that the diffusion sheet was not positioned correctly and therefore the measurement was not performed properly.

[0067] ((Second Embodiment)) In the previously described embodiment, the case was explained in which the same diffusion sheet was used for both measuring the color sample of a color swatch and measuring the color patch of metallic paper, which is one of the recording media. In this embodiment, it will be explained that different diffusion sheets can also be used. In this embodiment, the system is configured so that multiple types of diffusion sheets can be placed between the measuring instrument and the recording media of the object to be measured.

[0068] (Characteristics and experimental results of the diffusion sheet) Using the following five diffusion sheets, which showed high matching accuracy in the experiment described in the first embodiment, we confirmed the matching accuracy when the combination of measuring a color sample using the first diffusion sheet and measuring a color patch using the second diffusion sheet was changed. The method for confirming the matching accuracy was the same as in the above experiment.

[0069] Figure 16(a) shows the combinations that were checked. (2) One sheet of tracing paper (3) Two layers of tracing paper (6) Three layers of translucent film (7) Four layers of translucent film (8) Five layers of translucent film

[0070] Figure 16(b) shows the average color difference. The combination with the highest matching accuracy is F, where the first diffusion sheet is (8) "five layers of translucent film" and the second diffusion sheet is (7) "four layers of translucent film". Figure 17(a) shows the overlap of the color reproduction gamut measured for the color patches of each metallic paper, projected onto the L*-b* plane in CIE-L*a*b* space. It can be seen that the color reproduction gamuts of the first and second diffusion sheets are almost identical, and the overlapping area is wide. On the other hand, the combination with the lowest matching accuracy is G, where the first diffusion sheet is (2) "one sheet of tracing paper" and the second diffusion sheet is (8) "five layers of translucent film". Figure 17(b) shows the overlap of the color reproduction gamuts in that case, and it can be seen that the overlap of the color reproduction gamuts of the first and second diffusion sheets is very small.

[0071] This experiment showed that color matching is possible even when the first and second diffusion sheets are different. Furthermore, it was found that the matching accuracy improves when the overlapping color reproduction ranges of the first and second diffusion sheets are wide.

[0072] As explained above, color matching is possible even when the diffusion sheet used to measure the color sample is different from the diffusion sheet used to measure the color patch on metallic paper.

[0073] ((Third Embodiment)) In the previously described embodiment, a color conversion flow using a spot color library was explained, but in this embodiment, the flow of the spot color adjustment function will be described. Spot color adjustment is a function performed when the user is not satisfied with the color matching with the color sample when the color specified by the spot color is output using the color conversion flow described in the first embodiment.

[0074] (Spot color adjustment flow) Figure 18 shows the spot color adjustment dialog 1800. The image processing device 307 has a function to adjust the spot color for each recording medium. When the spot color adjustment function is activated in the UI unit 401, the spot color adjustment dialog 1800 shown in Figure 18 is activated.

[0075] 1801 is a list box for selecting the spot color library to adjust. When adjusting spot colors for metallic paper, select the corresponding spot color library specifically for metallic paper.

[0076] 1802 is a list box for selecting the recording medium to be adjusted. The already registered recording media are listed; to adjust the spot color of metallic paper, select the corresponding metallic paper name.

[0077] 1803 is a list box for selecting the type of recording medium to adjust. Options include paper, film, and metallic. To adjust the spot color on metallic paper, select metallic.

[0078] 1804 is a combo box for setting the name of the spot color to adjust. The spot colors registered in the selected spot color library are listed. You can select a spot color from the list, or you can create a new one by directly entering a spot color name.

[0079] 1805 is a UI for specifying the target value of a spot color using CIE L*a*b*. If the spot color is already registered, the registered Lab value will be displayed. The user can change the numerical value in the UI to set the target value of the spot color. For newly added spot color names, the Lab value will not be displayed, so the user must enter it.

[0080] 1806 is a UI for specifying the step size of the patches output by spot color adjustment. Spot color adjustment records 27 color patches around the Lab value specified by the spot color target value 1805, within the set step size. You can specify the step size. Figure 21(a) shows the relationship between the target value and the patches shifted by the step size around it, and Figure 21(b) shows the Lab value of each patch.

[0081] Figure 19 is a flowchart for spot color adjustment. In step S1901, a spot color library is selected via the spot color adjustment dialog 1800. Select the metallic spot color library in which the spot color to be adjusted is registered.

[0082] In step S1902, select the recording medium to be adjusted. Select the name of the recording medium to be adjusted from the recording media registered in 1802. In step S1903, select the type of recording medium to be adjusted. Select the appropriate type from the recording medium types (paper type, film type, metallic type) in 1803. In step S1904, determine if the set recording medium type is metallic. If it is metallic, proceed to step S1905; otherwise, proceed to step S1906.

[0083] In step S1905, if the metallic type is selected, the user is prompted to use a diffusion sheet when measuring the color sample. A message as shown in Figure 20 is displayed, prompting the user to use a measuring instrument with optical geometry conditions of 0 / 45 or 45 / 0 and to use a diffusion sheet when measuring the color sample of the target color. In step S1906, the user manually measures the color sample of the spot color to be adjusted. The user uses a measuring instrument owned by the user, not a measuring instrument inside the measuring unit 304, and stores the Lab value of the color sample in the user's memory. If the metallic type is selected, the user is asked to place a diffusion sheet on top of the color sample before measuring. The diffusion sheet is provided to the user as an accessory of the recording device. Also, if the target Lab value of the spot color to be adjusted is predetermined, this step does not need to be performed.

[0084] Step S1907 is the step in which the name of the spot color to be adjusted is entered. If the spot color is already registered in 1804, it is selected from the list; if it is a newly registered spot color to be adjusted, it is entered in 1804. In step S1908, the target Lab value of the spot color to be adjusted is entered. The Lab value recorded in step S1906 is entered into the target color in 1805. In step S1909, the step size of the spot color adjustment patch is specified. If the recording medium type is paper or film, the default values ​​are set to predetermined values. For example, ΔL=1, Δa*=1, Δb*=1. The user can adjust each step size. On the other hand, if the recording medium type is metallic, the data range in the brightness and saturation directions when measuring the color patch will be narrower than when not using a diffusion sheet, because a diffusion film is used for measurement.

[0085] Figure 22 shows the color reproduction of a color patch recorded on silver metallic paper, one of the recording media, projected onto the a*-b* plane of CIE-L*a*b*. The figures show measurements taken using a measuring instrument with optical geometry conditions 45 / 0, with (2) "one sheet of tracing paper" as the diffusion sheet, and measurements taken with an integrating sphere measuring instrument. It can be seen that the color reproduction range is narrowed when a diffusion sheet is used.

[0086] When the difference in color reproduction range is large in this way, if the adjustment patch increments are the same as those for paper and film types, the adjustment patch increments relative to the color reproduction range of the diffusion sheet will be relatively large. Therefore, in the case of metallic paper, the interval of the spot color adjustment patches that are actually recorded will be larger than the specified increment, making it difficult to adjust to the target color. For this reason, when metallic type is specified as the recording medium type, the increment in step S1909 is reduced based on the size of the color reproduction range using the diffusion sheet. For example, for the color reproduction range of a standard-sized paper type, the differences between the maximum and minimum values ​​of L*, a*, and b* are ΔL_p, Δa_p, and Δb_p, respectively. Similarly, for color reproduction using a diffusion sheet on metallic paper, these are ΔL_m, Δa_m, and Δb_m. The percentage S to reduce the increment for the metallic type in this case is calculated as follows. S=(ΔL_m / ΔL_p + Δa_m / Δa_p + Δb_m / Δb_p) / 3 In this case, the color gamut of the metallic type can be calculated using the data from the A2B1 tag of the ICC profile associated with the recording medium name 1802.

[0087] For example, if the calculated step size reduction ratio S is S=0.4, the default value when the metallic type 1806 is specified will be set to the following value. ΔL = 1.0 × 0.4 = 0.4 Δa = 1.0 × 0.4 = 0.4 Δb = 1.0 × 0.4 = 0.4 If a metallic type is selected by recording medium type 1803, the default value for the patch adjustment step size in 1806 is also updated. To inform the user that the default value has been changed, the message in Figure 20 also states that the step size for the color adjustment patch has been updated.

[0088] In step S1910, the user instructs the system to perform spot color adjustment. When the user presses the execute button 1807, the spot color adjustment process begins. In step S1911, the spot color adjustment patch is recorded. Image data and parameters for recording the color patch shown in Figure 21(b) are generated and printed by the print unit 301. The printed patch is transported to the measurement unit 304. In step S1912, it is determined whether the recording medium type selected in step S1903 is a metallic type. If it is a metallic type, the system proceeds to step S1913; otherwise, it proceeds to step S1914. In step S1913, the system switches to the configuration shown in Figure 11(b), where the diffusion sheet is placed in the measurement window on the downstream side of the sheet of the pressing mechanism 1102. In step S1914, the color patch is measured. The measured data is sent to the working memory 402. In step S1915, the spot color adjustment value is calculated. The system searches for the color patch closest to the target Lab set in step S1908 from the measured values ​​in working memory 402, and determines the device CMYK value used when outputting that color patch as the adjustment value for the spot color to be adjusted. This completes the spot color adjustment flow.

[0089] When inputting the target Lab value for a spot color, the system prompts the user to use a diffusion sheet for measurement when measuring metallic color samples, allowing the data range to be the same as the ICC profile of the metallic paper. Furthermore, aligning the data ranges improves the matching accuracy of spot color adjustments. [Explanation of Symbols]

[0090] 300 Recording Media Supply Unit 301 Printing Department 302 Ink supply unit 401 UI section 404 Arithmetic section 410 Recording device

Claims

1. A measuring means for measuring diffused light in a specific direction, wherein a diffusion sheet that converts the strongly directional component of light into a diffuse component is placed between the metallic paper, which is the recording medium to be measured, and the measuring means for measuring a patch recorded on the metallic paper, A determination means for determining a correction value for recording an image on metallic paper, based on a color matching target value corresponding to the aforementioned state and the measurement result of the patch by the measurement means, An image processing apparatus characterized by comprising:

2. The image processing apparatus according to claim 1, further comprising recording means for recording the patch on metallic paper.

3. The image processing apparatus according to claim 1, further comprising a holding means for pre-holding the aforementioned color matching target values.

4. The image processing apparatus according to claim 1, characterized in that the measurement means includes means for switching between measuring with the diffusion sheet placed between the recording medium to be measured and the recording medium to be measured and measuring with the diffusion sheet not placed between the recording medium to be measured.

5. The measurement means is capable of switching between placing a first type of diffusion sheet and a second type of diffusion sheet as the diffusion sheet between itself and the recording medium to be measured. The color matching target value is obtained based on the measurement results obtained by measuring the target object using the first type of diffusion sheet. The image processing apparatus according to claim 1, characterized in that the patch is measured using the second type of diffusion sheet.

6. The image processing apparatus according to claim 5, characterized in that when metallic paper is measured using a second type of diffusion sheet, the brightness of the non-recorded area where no image is recorded is higher than the brightness of the recorded area recorded using a single color of yellow ink.

7. The image processing apparatus according to claim 5, characterized in that when metallic paper is measured using a first type of diffusion sheet, the brightness of the non-recorded area where no image is recorded is higher than the brightness of the recorded area recorded using a single color of yellow ink.

8. The image processing apparatus according to claim 5, characterized in that the degree of diffusion of the first type of diffusion sheet and the degree of diffusion of the second type of diffusion sheet are substantially the same.

9. The image processing apparatus according to claim 5, characterized in that the first type of diffusion sheet and the second type of diffusion sheet are the same.

10. The image processing apparatus according to claim 5, characterized in that the recording means records a plurality of adjustment patches in which the color of the surrounding area is varied by a predetermined amplitude, with the measurement result of the object using a first type of diffusion sheet as the color matching target value, and the amplitude is adjusted based on the measurement result of the patch.

11. The image processing apparatus according to claim 1, further comprising a notification means for notifying the user of information indicating that the diffusion sheet should be placed between the metallic paper and the measurement means when measuring a patch recorded on the metallic paper using the measurement means.

12. The image processing apparatus according to claim 11, characterized in that, in response to obtaining information indicating that the diffusion sheet has been placed, the measuring means performs a measurement.

13. The image processing apparatus according to claim 1, characterized in that the measuring means is a measuring instrument for optical geometric conditions 0 / 45 or 45 / 0.

14. A measuring means for measuring diffused light in a specific direction, When measuring a patch recorded on metallic paper using the aforementioned measuring means, a notification means provides information indicating that a diffusion sheet that converts a strongly directional component of light into a diffuse component is to be placed between the metallic paper and the measuring means. An execution means that causes the measuring means to perform a measurement based on the acquisition of information indicating that the diffusion sheet has been placed, A measuring device characterized by comprising the following features.

15. The measuring device according to claim 14, further comprising a determination means for determining a correction value for recording an image on metallic paper based on a color matching target value corresponding to the aforementioned state and the measurement result of the patch by the measuring means.

16. A measurement step of measuring a patch recorded on metallic paper, which is a recording medium to be measured, with a diffusion sheet that converts the strongly directional component of light into a diffusion component, placed between the metallic paper and the measurement means, using a measurement means that measures diffused light in a specific direction. A determination step of determining a correction value for recording an image on metallic paper based on a color matching target value corresponding to the aforementioned state and the measurement result of the patch by the measurement means, An image processing method characterized by comprising:

17. When measuring a patch recorded on metallic paper using a measuring means for measuring diffused light in a specific direction, the process includes notifying information indicating that a diffusion sheet that converts the strongly directional component of light into a diffuse component is to be placed between the metallic paper and the measuring means, The process of causing the measuring means to perform a measurement based on the acquisition of information indicating that the diffusion sheet has been placed, A measurement method characterized by comprising the following features.

18. A program for causing a computer to perform each step of the image processing method described in claim 16.

19. A program for causing a computer to perform each step of the measurement method described in claim 17.

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