Printing device, method of color calibration, and program

Abstract

To perform collar calibration on a printing device that performs printing using a fluorescent ink irrespective of variation in fluorescent whitening agent that is contained in a sheet.SOLUTION: One embodiment of the present invention is a printing device for executing processing relating to collar calibration of a fluorescent ink, the printing device including: printing means for printing a patch chart for estimating an amount of the discharged fluorescent ink on a sheet containing a fluorescent whitening agent; a white light source for emitting UV light; a sensor part including a light receiving element for receiving light emitted from the white light source and reflected by the sheet on which the patch chart is printed; and correction means for correcting an amount of the driven fluorescent ink on the basis of a measurement result by the sensor part. The patch included in the patch chart is printed with the fluorescent ink and a non-fluorescent ink, where at least one dot of the non-fluorescent ink overlaps dots of the fluorescent ink.SELECTED DRAWING: Figure 11A

Description

[Technical Field]

[0001] The present disclosure relates to a printing device, a color calibration method, and a program. [Background technology]

[0002] Conventionally, color calibration is known in which a printed patch is read by a measuring device, the ejection amount is estimated from the read density, and the amount of ink ejected is changed according to the estimated result to match the color density of the printing device between machines.

[0003] There are two main types of measuring instruments used for color calibration. The first is a spectrophotometer, which uses a white light source with wavelengths in the UV or visible light range and a diffraction grating to receive light that has been dispersed, thereby obtaining color density and color values ​​(e.g., CIE L*a*b*, tristimulus values ​​XYZ, etc.). The second is a density sensor. There are two methods used in density sensors. One method uses a light source with a bandwidth at a specific wavelength (e.g., an LED light source with peaks in the red, green, and blue wavelength ranges) and a light-receiving element (e.g., a photodiode) to obtain the reflection coefficient and thereby obtain the density characteristics of each of the red, green, and blue. The other method uses a white light source (e.g., an LED with a spectral distribution in the visible light range) and an optical filter (e.g., an optical filter with spectral sensitivity distributions in the red, green, and blue wavelength ranges) in front of the light-receiving element. With this method, the density characteristics are obtained by obtaining the reflection coefficient of light that has been dispersed into red, green, and blue.

[0004] Whether a spectrophotometer or a density sensor is used as the measuring instrument, care must be taken when using a light source that emits light including UV light, such as a white light source, as the light source for the measuring instrument when calibrating by printing patches of fluorescent ink on paper containing fluorescent brightener.The reason for this is that the amount of light emitted by the fluorescent brightener changes depending on the variation in the fluorescent brightener contained in the paper, making it difficult to determine whether changes in the measured value obtained by the measuring instrument are due to changes in the amount of ink ejected or variations in the fluorescent brightener.

[0005] Patent Document 1 discloses a technique for color calibration of fluorescent inks, in which the measured density detected by an optical sensor is corrected according to the fluorescence information of the ink, and a color misregistration correction table is created based on density characteristics conforming to the visual sense. Specifically, the method performs a weighting correction conforming to the visual sense on the measured density. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-136413 [Non-patent literature]

[0007] [Non-Patent Document 1] Lecture: Dye Chemistry for Dyeing Engineers (Part 10) by Kunihiko Imada, Journal of the Textile Machinery Society: Vol. 56 Summary of the Invention [Problem to be solved by the invention]

[0008] However, as mentioned above, even if the amount of ink ejected from the printer does not change, the measurement values ​​of the measuring instrument will change due to variations in the fluorescent brightening agent contained in the paper, so there is a possibility that variations in the fluorescent brightening agent will be mistakenly determined to be a change in the ejection amount.

[0009] In particular, when the calibration target is fluorescent ink, the effect on the measurement value becomes more complex because changes in the luminescence intensity of the fluorescent whitening agent induce changes in the luminescence intensity of the fluorescent ink. As a result, even if weighting based on visual characteristics is applied to the sensor readings as in Patent Document 1, the sensor reading accuracy cannot be improved, and the correction accuracy of the calibration is reduced, which is an issue.

[0010] In view of the above problems, the present disclosure aims to perform highly accurate color calibration in a printing device that prints using fluorescent ink, without being affected by variations in the fluorescent whitening agent contained in the paper. [Means for solving the problem]

[0011] One embodiment of the present invention is a printing device that performs processing related to fluorescent ink color calibration, and includes: a printing means that prints a patch chart for estimating the fluorescent ink ejection volume on paper containing a fluorescent whitening agent; a white light source that emits UV light; a sensor unit that includes a light-receiving element that receives light emitted by the white light source and reflected by the paper on which the patch chart is printed; and a correction means that corrects the amount of fluorescent ink ejected based on the measurement results by the sensor unit; wherein the patches included in the patch chart are printed using the fluorescent ink and non-fluorescent ink, and at least one dot of the non-fluorescent ink overlaps with a dot of the fluorescent ink. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to perform highly accurate color calibration in a printing device that prints using fluorescent ink, regardless of variations in the fluorescent whitening agent contained in the paper. [Brief explanation of the drawings]

[0013] [Figure 1] A block diagram showing the configuration of the image processing unit involved in color conversion processing. [Figure 2] Diagram showing patch chart [Figure 3] Diagram explaining 1D-LUT data [Figure 4] Printing system configuration diagram [Figure 5] Diagram showing how the sensor reads the patch chart [Figure 6] Diagram explaining the sensor unit [Figure 7]Diagram of excitation and emission wavelengths of fluorescent inks and spectral reflectance of non-fluorescent inks [Figure 8] Spectral reflectance diagram [Figure 9] A diagram showing the results of measuring calibration gradation patches with a color sensor [Figure 10] A diagram to explain the case where a sample printed with fluorescent ink on paper containing a fluorescent whitening agent was measured. [Figure 11A] A diagram showing how fluorescent ink and non-fluorescent ink are printed. [Figure 11B] A diagram showing how fluorescent ink and non-fluorescent ink are printed. [Figure 11C] A diagram showing how fluorescent ink and non-fluorescent ink are printed. [Figure 11D] A diagram showing how fluorescent ink and non-fluorescent ink are printed. [Figure 11E] A diagram showing how fluorescent ink and non-fluorescent ink are printed. [Figure 11F] A diagram showing how fluorescent ink and non-fluorescent ink are printed. [Figure 11G] A diagram showing how fluorescent ink and non-fluorescent ink are printed. [Figure 12] Flowchart of the process for determining the amount of non-fluorescent ink to be applied [Figure 13] Calibration process flowchart DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. There are several methods for color calibration, but the following two are typical methods.

[0015] The first method is to print single-color gradation patches and generate a table for correcting the ink amount so that each density of the gradation patches matches the target density. The second method is to estimate the ejection amount from the density of at least one or more printed patches and apply the appropriate correction table from pre-stored correction tables according to the estimated ejection amount. The correction table here refers to a table (see Figure 3(c)) that changes the ink amount (number of dots, dot diameter, etc.) printed for each ink. Below, we will explain an example using the first gradation patch.

[0016] [First embodiment] <Image processing unit of printing device> A printing device having an image processing unit according to this embodiment will be described below. Specifically, an inkjet printer (hereinafter simply referred to as "printer") is assumed as the printing device. The printer is equipped with a color sensor composed of a white light source for measuring a printed patch chart and a photodiode light-receiving element. The printer can print any patch chart and measure the printed patch chart with this color sensor. The printer can also function simply as a printing device and execute print processing based on print target data such as documents and images processed by various software.

[0017] The printer has six color inks: C (cyan), M (magenta), Y (yellow), K (black), FP (fluorescent pink), and G (green). However, the ink combinations are not limited to these. For example, R (red), Or (orange), B (blue) can be combined with a special color ink such as Gy (gray), or Lc (light cyan) diluted with C (cyan) and Lm (light magenta) diluted with M (magenta) can be used. Also, FB (fluorescent blue) and FY (fluorescent yellow) can be used instead of FP (fluorescent pink).

[0018] <Configuration related to color conversion processing> Figure 1 is a block diagram showing the configuration of the image processing unit in this embodiment that is involved in color conversion processing. The printer in this embodiment has both the functionality of an RGB printer that receives RGB signals and the functionality of a CMYK printer that receives CMYK signals. For ease of explanation, image data is processed as 8-bit signal values ​​for each color. However, it goes without saying that the same effect can be achieved even if the pixel values ​​of each pixel in the image data are expressed in multiple bits, such as 10-bit, 12-bit, or 16-bit representations.

[0019] The image signal I / F 101 is an I / F unit for input image data, and in this embodiment, RGB signal image data and CMYK signal image data are input. The RGB signal image data is subjected to conversion processing by a color matching processing unit 102, which converts color data in a device-independent space into color data in a device-dependent space. Similarly, the CMYK signal image data is subjected to conversion processing by a color matching processing unit 103, which converts color data in a device-independent space into color data in a device-dependent space.

[0020] A color separation processing unit 104 performs color separation processing on the image data output from the color matching processing unit 102, converting color data in the device-dependent space into color material color data. Similarly, a color separation processing unit 105 performs color separation processing on the image data output from the color matching processing unit 103, converting color data in the device-dependent space into color material color data.

[0021] The color material color data output from the color separation processing units 104 and 105 is subjected to a gradation correction processing by a gradation correction processing unit 106 to match the color material color data with the output characteristics of the printer.

[0022] The color matching processors 102 and 103 and the color separation processors 104 and 105 can perform desired color conversion on input image data by setting their own lookup tables (hereinafter referred to as LUTs). The LUTs used here are provided and managed for each recording medium and each printing mode, such as high-speed printing and low-speed high-quality printing.

[0023] Of the above-mentioned processing units, the color matching processing unit 102 and color separation processing unit 104 each perform color conversion processing using a 3D-LUT. The color matching processing unit 103 and color separation processing unit 105 each perform color conversion processing using a 4D-LUT. The gradation correction processing unit 106 performs color conversion processing using a 1D-LUT. Specifically, the 3D-LUT used by the color matching processing unit 102 and color separation processing unit 104 is a 3D-LUT consisting of 16 grids with 17-count intervals for each color, totaling 16x16x16=4096 grids.

[0024] As shown in FIG. 1, the image processing unit has a calibration processing unit 107. The calibration processing unit 107 corrects color variations in the printed result caused by individual differences in the devices, recording media, and color materials that make up the printer, as well as fluctuations in ejection volume due to changes in the devices over time. Specifically, the calibration processing unit 107 performs processing using a 1D-LUT for each color material color signal. The reason for this processing is to align the density values ​​of the printing unit corresponding to the input data values ​​of the actual printing machine with calibration target values, which are the density values ​​of the printing unit corresponding to the input values ​​of a reference machine (on the production line).

[0025] In this embodiment, the printing device has an image processing unit, but the image processing unit may be provided separately from the printing device, and for example, an information processing device such as a personal computer may perform the functions of the image processing unit.

[0026] <About the patch chart> 2 shows a patch chart for measuring density values ​​during actual printing for specific input data values ​​as a print result of the actual printing device used during calibration. This patch chart has multiple patches for each ink.

[0027] For the cyan, magenta, yellow, black, and green patches, the input signal for each colorant ink is changed in 20% increments, and the ejection amount corresponding to each colorant in the printer can be estimated by measuring the color of the printed patch chart. For example, cyan patch P20 is printed using cyan ink only, with patch P201 printed with 0% cyan, patch P202 with 20% cyan, and patch P203 with 120% cyan.

[0028] In contrast, the fluorescent pink patch is printed using fluorescent pink colorant with an input signal that is varied in 20% increments and yellow colorant with a fixed input signal. In other words, the fluorescent pink patch P21 shown in Figure 2 is printed using fluorescent pink and yellow ink.

[0029] <About performing calibration> Fig. 3(a) is a diagram for explaining the 1D-LUT data used in the calibration processing unit 107 in Fig. 1. Fig. 3(a) shows an example of one type of ink on a certain medium, with the vertical axis indicating the print density value of the print part read by the sensor and the horizontal axis indicating the amount of ink applied (%) when printing a patch.

[0030] The coverage amount refers to the percentage of ink dots printed on the paper. Here, we will use an inkjet printer with a resolution of 1200 dpi x 1200 dpi as an example of a printing device. If the area where one 1200 dpi x 1200 dpi dot is printed is defined as one grid, then 100% means that one dot is printed in all of the multiple grids. Furthermore, 200% means that for all 1200 dpi x 1200 dpi grids, two dots are printed in each grid (twice the number of dots printed compared to 100%). Note that the dots do not necessarily have to be printed in the center of the grid; dots can also be printed between the grids.

[0031] When the amount of ink injected is X%, the density value is expressed as follows, assuming that the reflection coefficient output by the sensor is P(X). D(X)=-log(P(X) / P(0))...Equation 1 where P(0) is the reflectance coefficient of the patch in the paper white area.

[0032] Also, if it is printed by mixing it with ink of a certain amount C%, D(X)=-log(P(X) / P(C))...Equation 2 Here, P(C) is the reflection coefficient of ink at a certain ink volume of C%.

[0033] The curve shown by the dashed line 301 in Figure 3(b) etc. is the print density value of the color material in the reference machine relative to the input data value, and indicates the calibration target value. The reference machine is a printer that serves as a reference and whose ejection volume is the center of the variation in the ejection volume of the actual machine. Information about such calibration target values ​​is stored in advance in the storage means of each printer in the system.

[0034] The curve indicated by the solid line 302 represents the print density values ​​of the color materials in the actual machine. The actual machine is the printer on which the calibration is performed. This information is obtained by printing the patch chart of FIG. 2 and reading the printed patch chart with a sensor. D0 to D6 represent the density (calculated using Equation 1) corresponding to each patch in 20% increments from 0% to 120% on the patch chart. The solid line 302 is derived using interpolation processing, an approximation curve, or the like, based on the measured values ​​of D0 to D6.

[0035] As shown in the printing state of the actual machine in Figure 3(a), the actual machine generally ejects more color material than the reference machine, and prints darker than the reference machine, especially in the intermediate density range. The calibration processing unit 107 performs correction by converting and correcting the contone color signals for each color material so that the print density matches that of the reference machine, and the calibration processing unit 107 performs the correction process using correction parameters. The calculation of these correction parameters will be explained using Figure 3(b).

[0036] Plot point D2 in Figure 3(b) shows the density value when a patch with a 40% ink ejection amount on the patch chart in Figure 2 is printed on an actual device. This value is higher than the target density value indicated by plot point T2, which corresponds to the same ink ejection amount. Therefore, the ink ejection amount must be reduced to match the density value of the actual device to the target density value. Specifically, the ink ejection amount of the actual device to which the density value of T2 corresponds is determined by searching the solid line 302 and finding point DY. In other words, when using an actual device, if printing is performed with the ink ejection amount 303 indicated by point DY, the print density value will be approximately equal to the target density value.

[0037] After applying the processing for plot point D2 described above to all plot points D0 to D6, interpolation processing, approximation curves, etc. can be used. This makes it possible to generate 1D-LUT data, which shows the relationship between the input print amount (%) and the output print amount (%), as shown in Figure 3(c). The 1D-LUT contains correction parameters such as discrete values ​​of 256 or 1024 points, or mathematical expressions that can be defined by a curve.

[0038] <Printing system configuration> 4 is a block diagram showing the configuration of a printing system according to this embodiment. The printing system includes a personal computer (hereinafter also referred to simply as a "PC") 401 as an information processing device, and a printer 407 as a printing device. The PC 401 and printer 407 are connected via a network and interfaces such as a USB and a local bus.

[0039] The PC 401 performs processes related to the control of the printer 407, as described below, in accordance with various software programs. The storage unit 405 stores system programs, application software programs, software programs necessary for printing operations, and software programs necessary for the processes described below. The storage unit 405 also stores various image processing parameters, mechanical parameters, printer control data, sensor unit control data, as well as necessary programs, various data, and print target data created on the PC 401. The storage unit 405 is typically a hard disk or flash ROM. The CPU 403 performs predetermined processes using the work area of ​​the work memory 404 in accordance with the various programs and data stored in the storage unit 405.

[0040] The data input / output means 406 is a portable storage device such as a CD, DVD, or USB memory, or a data communication device such as a LAN card, and is used as an interface with the outside.

[0041] The user interface (hereinafter also referred to as "UI") means 402, which is an operation means for the user, processes input by the user and output (display, etc.) to the user, and includes input devices such as a keyboard and a mouse, and display devices such as a display.

[0042] The printer 407 has a data transfer unit 408, a printer control unit 409, an image processing unit 410, a printing unit 411, and a sensor unit 412, and performs printing processing based on print data sent from the PC 401. This print data also includes control data for the sensor unit 412, and the printer 407 uses this control data to measure the printed matter. The data transfer unit 408 extracts image data and image processing parameters from the print data sent from the PC 401 and sends them to the image processing unit 410, and extracts mechanical parameters, printer control data, and sensor unit control data and sends them to the printer control unit 409. The data transfer unit 408 also reads information related to the results of printing, sensor measurement, etc., stored in storage means within the printer, and sends the read information to the PC 401. The printer control unit 409 is composed of a CPU, ROM, RAM, etc., and controls the printing operation of the printer 407 according to the printer control data sent from the data transfer unit 408. The printer control unit 409 also controls the printing operation and the measurement by the sensor unit 412 .

[0043] <About the color sensor> 5 shows an example of the configuration of a sensor unit 412 in a printer 407. A carriage 503 ejects ink while scanning left and right over a sheet of paper 501, thereby forming a patch image 502. A sensor member 504 is mounted on the side of the carriage 503.

[0044] <Color sensor light source and light receiving sensor optical filter> 6(a) shows a schematic configuration of the sensor unit. The sensor unit has a white light source 601 that emits light including UV light, and a light receiving element 602 for receiving light reflected by a printed matter 604. The sensor unit also has an optical filter 603 provided in front of the light receiving element 602. This optical filter is used for two purposes.

[0045] One is to select complementary colors to receive light with a wide wavelength range of density discrimination. That is, a red filter is selected for cyan and green, a green filter for magenta, fluorescent pink, and black, and a blue filter for yellow.

[0046] Another reason is that when light is shone on fluorescent ink, etc., the light with the excitation wavelength that is absorbed from the irradiated light and the light emitted at a wavelength longer than the wavelength range in which the light is absorbed are received separately.

[0047] Below are three examples of white light sources: The first is an LED with peaks in the red, green, blue, and UV wavelength ranges, and Fig. 6(b) shows the spectral intensity distribution as the spectral emission characteristics of each LED. Reference numeral 611 indicates the spectral intensity distribution of the blue LED, reference numeral 612 indicates the spectral intensity distribution of the green LED, reference numeral 613 indicates the spectral intensity distribution of the red LED, and reference numeral 614 indicates the spectral intensity distribution of the UV LED.

[0048] The second type is a white LED and a UV LED, which have a spectral distribution in the visible light range. Figure 6(c) shows the spectral intensity distribution as the spectral emission characteristics of a white LED. Reference numeral 621 indicates the spectral emission intensity distribution of the white LED, and reference numeral 622 indicates the spectral intensity distribution of the UV LED.

[0049] The third is a tungsten light source that also has a spectral distribution in the UV wavelengths, and reference numeral 631 in FIG. 6(d) shows the spectral intensity distribution as the spectral emission characteristic of the tungsten light source.

[0050] 6(e) shows the spectral sensitivity distribution as the spectral sensitivity characteristics of the optical filters. Reference numeral 641 indicates the spectral sensitivity distribution of a blue filter for cutting light other than blue, reference numeral 642 indicates the spectral sensitivity distribution of a green filter for cutting light other than green, and reference numeral 643 indicates the spectral sensitivity distribution of a red filter for cutting light other than red. The green filter is a filter that cuts light other than the excitation wavelength range of the fluorescent pink ink, and the red filter is a filter that cuts light other than the emission wavelength range of the fluorescent pink ink.

[0051] <Characteristics of fluorescent ink and non-fluorescent ink> Fluorescent colorants are colorants that absorb light of an excitation wavelength from their ground state, become excited, emit light of an emission wavelength, and return to their ground state to develop color. Figure 7 shows the intensity of excitation 701 and the intensity of emission 702 when fluorescent pink ink is recorded on paper, with the horizontal axis representing the wavelength of light and the vertical axis representing reflectance (intensity). The graph in Figure 7 shows the light intensity detected when the wavelength of light irradiated on the recording sample and the wavelength of light received from the sample are changed.

[0052] The emission 702 represents the intensity of light received by the recording sample for each wavelength when the recording sample is irradiated with light of an exciting wavelength. Figure 7 shows a graph of the fluorescent pink of this embodiment when the recording sample is irradiated with light of 480 nm.

[0053] Excitation 701 represents the intensity of received light when the wavelength of the light irradiated onto the recording sample is changed while the wavelength of the received light is fixed. Fig. 7 shows a graph for fluorescent pink in this embodiment when the wavelength of the received light is fixed at 600 nm.

[0054] As can be seen from Figure 7, the wavelength range of excitation of fluorescent ink printed on paper overlaps with the wavelength range of emission, but is on the short wavelength side. The excitation 701 has different strengths for each wavelength, with some wavelengths emitting light efficiently and others not. Furthermore, because fluorescent colorants emit light, the reflectance at the emission wavelength often exceeds 1. In this embodiment, colorants with the above-described characteristics are defined as fluorescent colorants.

[0055] While the excitation and emission of fluorescent pink ink have been described above, fluorescent inks that emit light at other wavelengths may also be used in this embodiment. Examples of such fluorescent inks include fluorescent blue, which emits light in the blue region (450 nm to 500 nm), and fluorescent green, which emits light in the green region (500 nm to 565 nm). Alternatively, fluorescent yellow, which emits light in the yellow region (565 nm to 590 nm), and fluorescent orange or fluorescent red, which emit light in the red region (590 nm to 780 nm), may also be used. Furthermore, fluorescent inks that combine the aforementioned fluorescent inks may also be used. Furthermore, color tones may be adjusted by combining fluorescent inks with different excitation wavelength intensities. For example, fluorescent pink, which emits light in the orange region with weak excitation in the blue region and strong excitation in the green region, may be used.

[0056] In this embodiment, non-fluorescent ink is defined as ink containing a coloring material that absorbs light of a specific wavelength when it is irradiated with light and does not emit light. For example, the spectral reflectance of non-fluorescent ink is the spectral reflectance of cyan (C) 703, magenta (M) 704, and yellow (Y) 705 in Figure 7. Unlike fluorescent ink, non-fluorescent ink only absorbs light, so its reflectance does not exceed 1.

[0057] <About fluorescent ink> Next, the fluorescent ink used in this embodiment will be described. In this embodiment, a fluorescent ink is used that is prepared by mixing a dispersion having fluorescent properties, a solvent, and an activator. The fluorescent dispersion used in this embodiment is a dispersion having fluorescent properties. Examples include NKW-3207E (fluorescent pink aqueous dispersion: Nippon Kinko Kagaku Co., Ltd.) and NKW-3205E (fluorescent yellow aqueous dispersion: Nippon Kinko Kagaku Co., Ltd.), but any dispersion having fluorescent properties will do. A fluorescent dye is included in the dispersion having fluorescent properties, and the content (mass %) of the fluorescent dye in the ink is preferably 0.1 mass % or more and 5.0 mass % or less.

[0058] The fluorescent dispersion is dispersed into ink by combining a known solvent and surfactant with the fluorescent dispersion. The dispersion method for the fluorescent dispersion is not particularly limited. For example, fluorescent dispersions dispersed with surfactants or resin-dispersed fluorescent dispersions dispersed with dispersion resins can be used. Of course, fluorescent dispersions dispersed with different dispersion methods can also be used in combination. Anionic, nonionic, cationic, or amphoteric surfactants can be used as surfactants. Any water-soluble or water-dispersible resin can be used as the dispersion resin. Among these, dispersion resins with a weight-average molecular weight of 1,000 to 100,000, and preferably 3,000 to 50,000, are particularly preferred. The solvent is preferably an aqueous medium containing, for example, water and a water-soluble organic solvent.

[0059] <About recording media and fluorescent whitening agents> In this embodiment, the recording medium onto which the ink is ejected (also referred to as the recording medium) has a base material and at least one ink-receiving layer. The recording medium is preferably an inkjet recording medium used in an inkjet image recording method.

[0060] Some inkjet recording media contain fluorescent brighteners to make the paper appear whiter. As described in Non-Patent Document 1, fluorescent brighteners absorb light (UV light) in the ultraviolet region (330 to 380 nm) and emit fluorescence (blue light) on the short wavelength side of the visible region (400 to 450 nm). They are a type of dye genus that has affinity for fibers. Since there are no white dyes, fluorescent brighteners are used to dye paper white.

[0061] The fluorescent whitening agent is mainly added to the ink-receiving layer (coating layer), and its component is 2,5-thiophenediylbis(5-tert-butyl-1,3-benzoxazole), and its content is generally between 0.1g / m² and 2.0g / m².

[0062] <About patch printing and measurement> In this embodiment, the patch is read by the color sensor shown in FIG. 6(a).

[0063] First, we will describe an example of reading a magenta gradation patch. Figure 8(a) shows the ink spectral reflectance obtained by measuring a magenta patch printed on paper with a spectrophotometer. In Figures 8(a) and 8(b), the horizontal axis represents wavelength λ, and the vertical axis represents reflectance. In Figure 8(a), reference numeral 801 represents the reflectance of paper white, and reference numerals 802 to 807 represent the reflectance of calibration patches whose print amount is modulated in 20% increments.

[0064] As mentioned above, the color sensor of this embodiment emits light in the visible light range (300 to 700 nm), including UV, and uses an optical filter to limit the wavelength range of the light it receives. However, when measuring magenta patches, a green filter is used. The change in reflectance caused by changing the amount of magenta ink is particularly large around 540 nm. Therefore, using a green filter when receiving light with the sensor allows the sensor to efficiently detect changes in the amount of ink. Reference numeral 901 in Figure 9(a) shows an example of the results of measuring seven patches printed with magenta ink with a color sensor.

[0065] As shown in Figure 6(e), each filter has a specific wavelength bandwidth. For example, a green filter has a sensitivity spectrum in the wavelength range of approximately 500 to 600 nm, and as shown in Figure 6(a), the sensor receives the reflected light of the irradiated light. For non-fluorescent ink, as the ink volume increases, the reflected light decreases, and the sensor output value (reflection coefficient) decreases. The fluctuation in the ejection volume is estimated based on this decrease. Specifically, the target density is compared with the actual machine density calculated using Equation 1 or Equation 2 using the sensor output value (reflection coefficient). If the actual machine density is lower than the target density, it is estimated that the ejection volume of the actual machine is lower than the ejection volume of the reference machine. On the other hand, if the actual machine density is higher than the target density, it is estimated that the ejection volume of the actual machine is higher than the ejection volume of the reference machine.

[0066] Next, we will describe an example of reading a fluorescent pink gradation patch. Figure 8(b) shows the ink spectral reflectance obtained by measuring a patch printed on paper using only fluorescent pink ink with a spectrophotometer. In Figure 8(b), reference numeral 811 indicates the spectral reflectance of the paper white, and reference numerals 812 to 817 indicate the spectral reflectance of calibration patches whose print amount is modulated in 20% increments.

[0067] When measuring with a color sensor, light in the visible light range (300 to 700 nm), including UV, is irradiated. To measure accurately, it is necessary to separate the wavelength range of the received light using an optical filter. There are two ways to separate the wavelength of the received light: receiving light in the excitation wavelength range (excitation wavelength light) and receiving light in the emission wavelength range (emission wavelength light).

[0068] Here, we will explain an example of receiving light in the excitation wavelength range. As mentioned above, fluorescent pink absorbs irradiated light and has a large change in reflectance around λ = 540 nm, so a green filter is used as the optical filter when receiving light (see Figure 6(e)). In this case, it is possible to measure the amount of light absorbed by the ink from the light reflected by the white paper. The measurement results of this sensor are shown in Figure 9(b) by reference number 911.

[0069] Next, we will explain an example of receiving light in the emission wavelength range. As mentioned above, fluorescent pink emits light due to fluorescence around λ = 600 nm, so a red filter is used as the optical filter when receiving light (see Figure 6(e)). The measurement results of this sensor are shown in Figure 9(c) by reference number 921.

[0070] However, when paper contains a fluorescent brightener, variations in the fluorescent brightener affect the measurement values. Specifically, when the fluorescent brightener deteriorates over time, the measurement value decreases compared to before deterioration. As an example of such a change in measurement value, Figure 9(d) shows the case where excitation wavelength light is received, with reference numeral 911 indicating the value before deterioration and reference numeral 912 indicating the value after deterioration. In contrast, Figure 9(e) shows the case where emission wavelength light is received, with reference numeral 921 indicating the value before deterioration and reference numeral 922 indicating the value after deterioration.

[0071] This phenomenon will be explained in detail using FIG. 10, which shows a simple reflection model and the results of measurements using a spectrophotometer.

[0072] FIG. 10(a) shows a simple reflection model for a sample in which fluorescent ink dots 1002 are printed on printing paper 1001 containing a fluorescent whitening agent.

[0073] When a sample of paper printed with fluorescent ink is irradiated with light containing UV light, half of the irradiated light 1003 is reflected by the ink layer and exits into the air as first reflected light 1004. Meanwhile, the remaining half becomes incident light 1005 that enters the paper, is reflected inside the paper, then re-enters the ink layer, and exits into the air as second reflected light 1006. The measuring instrument measures the combined light of first reflected light 1004 and second reflected light 1006. In reality, complex light absorption and scattering occurs within the ink and paper, but this is omitted in this embodiment for simplicity.

[0074] As shown in Figure 10(b), when UV light 1012 in the wavelength range of 330 to 380 nm is irradiated onto paper 1011 containing a fluorescent brightening agent, light 1013 in the blue wavelength range (400 to 450 nm) is emitted from the paper. Therefore, when paper containing a fluorescent brightening agent is compared to paper not containing a fluorescent brightening agent, the amount of light reflected from the paper, that is, the amount of light in the blue wavelength range contained in second reflected light 1006 shown in Figure 10(a), is increased. As a result, the amount of light at the excitation wavelength and the amount of light at the emission wavelength increase as the light passes through the layer of fluorescent ink dots 1002.

[0075] Figure 10(c) shows the spectral reflectance measured with a spectrophotometer for patches printed with fluorescent pink ink on paper containing and not containing fluorescent brightener. The paper containing fluorescent brightener was "Canon Photo Paper Pro Gloss [Platinum Grade]," and the paper not containing fluorescent brightener was "Canon Glossy Type Roll Paper (Double-Sided)," both of which are resin-coated papers. In Figure 10(c), the spectral reflectance of the paper containing fluorescent brightener is indicated by reference numeral 1021, and the spectral reflectance of the paper not containing fluorescent brightener is indicated by reference numeral 1022.

[0076] Although the type of paper differs, paper containing a fluorescent brightening agent increases the light reflected by the paper surface, i.e., the light in the blue wavelength range contained in the second reflected light 1006. As a result, as the second reflected light 1006 passes through the layer of fluorescent ink dots 1002, the amount of reflected green light (reference numeral 1023), which is excitation wavelength light, and the reflected red light (reference numeral 1024), which is excited and emitted, are greater than with paper without a fluorescent brightening agent. This result indicates that when paper containing a fluorescent brightening agent is used and the fluorescent components in the paper deteriorate over time, the amount of excitation wavelength light and emission wavelength light decreases.

[0077] Next, Fig. 10(d) shows the spectral reflectance when patches on each paper were printed with yellow ink first and then fluorescent pink using a spectrophotometer. In Fig. 10(d), the spectral reflectance of the paper containing fluorescent brightener is indicated by reference numeral 1031, and the spectral reflectance of the paper not containing fluorescent brightener is indicated by reference numeral 1032.

[0078] A comparison is made between the case where yellow ink is not printed (FIG. 10(c)) and the case where yellow ink is printed (FIG. 10(d)). As indicated by reference numerals 1023, 1024, 1033, and 1034, the difference in reflectance in the excitation wavelength range and the difference in reflectance in the emission wavelength range when yellow ink is printed are both smaller than when yellow ink is not printed. In other words, by applying yellow ink first, it is possible to suppress changes in density measured by the sensor caused by variations in the fluorescent brightening agent (differences between manufacturing lots, deterioration over time).

[0079] <About the non-fluorescent inks to be mixed and how to apply the ink> The method of applying mixed non-fluorescent inks will be explained below with reference to Figures 11A to 11F. In each of Figures 11A to 11F, the upper figure is a top view of printing paper 1001 on which ink has been printed. Meanwhile, the lower figure corresponds to the upper figure and is a cross-section of printing paper 1001 on which ink has been printed, viewed from the side.

[0080] In order to mitigate the effects of the fluorescent brightening agent, it is desirable that the non-fluorescent ink to be mixed be an ink that has the property of absorbing light at the excitation wavelength or emission wavelength of the fluorescent brightening agent. Furthermore, as shown in Figure 11A or 11B, it is desirable that at least one dot of the mixed non-fluorescent ink dot 1101 overlaps with a dot of the fluorescent ink 1002. Furthermore, the non-fluorescent ink may be printed after the fluorescent ink, as shown in Figure 11A, or may be printed before the fluorescent ink, as shown in Figure 11B.

[0081] Next, we will explain in detail how to perform post-hitting and pre-hitting.

[0082] For example, in the printer 407, the order in which inks are applied to the same area is controlled so that non-fluorescent ink is applied to a position where fluorescent ink has been applied. This makes it possible for dots of non-fluorescent ink to at least partially cover dots of fluorescent ink below them (post-application of non-fluorescent ink). Alternatively, conversely, the order in which inks are applied to the same area is controlled so that fluorescent ink is applied to a position where non-fluorescent ink has been applied. This makes it possible to cover non-fluorescent ink with fluorescent ink (pre-application of non-fluorescent ink).

[0083] Furthermore, by adjusting the amount of each ink applied at the timing of application, it is possible to have dots of non-fluorescent ink cover dots of fluorescent ink to the desired extent, or to form fluorescent ink on top of non-fluorescent ink to the desired extent.

[0084] 11C, it is desirable to print the mixed non-fluorescent ink dots 1101 so that they overlap all of the fluorescent ink dots 1002. In FIG. 11C, the diameter of the non-fluorescent ink dots 1101 and the diameter of the fluorescent ink dots 1002 are equal, and the entire top surface of the fluorescent ink dots 1002 is covered by the bottom surface of the non-fluorescent ink dots 1101.

[0085] Alternatively, as shown in Fig. 11D, it is desirable to print the fluorescent ink dots 1002 so that they overlap all of the non-fluorescent ink dots 1101. In Fig. 11D, the diameter of the non-fluorescent ink dots 1101 and the diameter of the fluorescent ink dots 1002 are equal, and the entire upper surface of the non-fluorescent ink dots 1101 is covered by the lower surface of the fluorescent ink dots 1002.

[0086] Furthermore, as shown in Figure 11E, it is even more desirable to take into consideration the spread of reflected light due to scattering inside the paper after the irradiated light passes through the fluorescent ink (indicated by reference numeral 1102). Specifically, it is desirable to cover the area with dots 1101 of non-fluorescent ink that are mixed in and extend beyond the spread of reflected light (indicated by reference numeral 1102).

[0087] This is true whether the non-fluorescent ink is deposited after the fluorescent ink (FIG. 11F) or before the fluorescent ink (FIG. 11G). In FIG. 11F, the diameter of the non-fluorescent ink dots 1101 is larger than the diameter of the fluorescent ink dots 1002, and the top and side surfaces of the fluorescent ink dots 1002 are covered by the non-fluorescent ink dots 1101. On the other hand, in FIG. 11G, the diameter of the non-fluorescent ink dots 1101 is larger than the diameter of the fluorescent ink dots 1002, and the bottom surfaces of the fluorescent ink dots 1002 are covered by the top surfaces of the non-fluorescent ink dots 1101.

[0088] Furthermore, the dots 1101 of the mixed non-fluorescent ink preferably have a thickness and colorant density sufficient to absorb light of the excitation wavelength and emission wavelength of the fluorescent brightener.

[0089] <How to determine the amount of ink to be mixed> The process of determining the ink amounts of the inks to be mixed will be described below with reference to FIG.

[0090] In step S1201, fluorescent ink calibration patches are printed on paper containing a fluorescent whitening agent. Hereinafter, for simplicity, "step S~" will be abbreviated to "S~".

[0091] In S1202, fluorescent ink calibration patches are printed on paper that does not contain fluorescent brighteners.

[0092] In S1203, the density of the patch printed in S1201 and the density of the patch printed in S1202 are measured, and the density difference between them is calculated. The density difference calculated here is called ΔOD 蛍光増白剤のばらつき Let's say.

[0093] In addition, the target density difference for fluorescent ink calibration is defined. In addition, the error that occurs during the calibration process is defined. In this embodiment, as an example, the density difference that fluctuates with repeated printing is defined as ΔOD 印刷繰り返し誤差 The concentration difference that varies during the measurement is defined as ΔOD 測定誤差 It is defined as: Let's say.

[0094] In S1204, it is determined whether the following formula 3 is satisfied. JPEG2023162974000002.jpg16150

[0095] If the determination result in S1204 is true, the series of processes ends. On the other hand, if the determination result in S1204 is false, the process proceeds to S1205.

[0096] In S1205, the amount of non-fluorescent ink (yellow ink in this example) to be mixed with the fluorescent ink is increased by a predetermined amount, and then the process returns to S1201, where the process of printing patches is performed again.

[0097] The above-described series of processes allows the optimum amount of non-fluorescent ink to be determined. Here, ΔOD is used as an example of an error that occurs during the calibration process. 印刷繰り返し誤差 and ΔOD 測定誤差 However, errors are not limited to these two.

[0098] Furthermore, although the target density difference for calibration is calculated using the mean square error of density, other error calculation formulas may also be used.

[0099] Furthermore, although density is used as the quantitative evaluation value for the ink ejection amount, the quantitative evaluation value is not limited to this, and color values ​​(CIE L*a*b*, tristimulus values ​​XYZ, etc.) may also be used.

[0100] <About the calibration process> The calibration process in this embodiment will be described below with reference to Fig. 13. This process is executed by the CPU 403 or the like in accordance with the calibration process program stored in the storage means 405 in Fig. 4. Parameters required for the calibration process are input via the UI means 402.

[0101] In S1301, a calibration patch chart is printed. Here, the process of printing the calibration patch chart shown in FIG. 2 will be described. First, patches are created in which the ejection amount is modulated in 20% increments from 0% to 120%. Note that in this example, as shown in FIG. 2, patches are used in which the ejection amount of the patch is modulated in 20% increments from 0% to 120%, but increments other than 20% may be used, and the maximum ejection amount may also be other than 120%.

[0102] 2 has been completed for all the inks for which patches are to be created. If so, the patch chart data is stored in the storage unit 405.

[0103] Then, information related to printing on media (such as paper) is read from the storage means 405, and the read information is sent to the printer 407. The created and saved patch chart data is also read from the storage means 405, and input to the output unit of the calibration processing unit 107 via the image signal I / F 101 (see FIG. 1) for color material color signals, whereupon the next halftoning process is directly performed. Thereafter, the data is printed by the printing unit 411.

[0104] In this embodiment, calibration patches are created during the calibration process, but patch chart data created in advance may be stored in the storage unit 405, and the patch chart data may be read and used when the calibration process is executed.

[0105] Next, the steps (S1302 to S1306) for measuring each patch included in the printed patch chart will be described. First, in S1302, the printer control unit 409 determines whether the patch to be measured is a fluorescent ink patch. If the determination result in this step is true, the process proceeds to S1303. On the other hand, if the determination result in this step is false, the process proceeds to S1305.

[0106] In S1303, the printer control unit 409 irradiates the patch with light having a spectral distribution in a wavelength range including the excitation wavelength and emission wavelength of the fluorescent ink.

[0107] In S1304a, the printer control unit 409 reads the reflection intensity using the sensor unit 412, which receives light of the emission wavelength of the fluorescent ink that has passed through the red filter, to obtain the measurement result of the sensor unit 412. Specifically, the reflection intensity of the patch is read using the method described above in <Regarding Patch Printing and Measurement>.

[0108] In this embodiment, the light to be irradiated when measuring the calibration patch is selected during the calibration process, but the measurement may be performed according to the conditions of the light to be irradiated that are stored in advance in the storage unit 405.

[0109] In S1305, the printer control unit 409 irradiates the patch with light whose spectral distribution is in a wavelength range where the spectral reflectance of the ink changes greatly in response to changes in the ejection amount, and obtains the measurement results of the sensor unit 412 by reading the reflection intensity using the sensor unit 412.

[0110] In S1306, the printer control unit 409 determines whether measurement of patches of all ink colors to be measured has been completed. If the determination result in this step is true, the process proceeds to S1307 to perform calibration. On the other hand, if the determination result in this step is false, the process returns to S1302.

[0111] Next, the steps of actually performing calibration (S1307 to S1309) will be described. First, in S1307, the printer control unit 409 estimates the ejection amount based on the reflection intensity read in the patch measurement.

[0112] In S1308, the printer control unit 409 corrects the amount of ink deposited based on the estimation result of S1307. Specifically, this is performed in the manner described above in <Regarding Calibration Execution>, and the correction process is performed using the 1D-LUT stored in the calibration processing unit 107.

[0113] In S1309, the printer control unit 409 determines whether calibration has been completed for all ink colors. If the determination result in this step is true, the series of processes ends. On the other hand, if the determination result in this step is false, the process returns to S1307.

[0114] In this embodiment, the gradation correction processing unit 106 performs processing using a 1D-LUT that is different from the 1D-LUT used by the calibration processing unit 107. However, the gradation correction processing unit 106 and the calibration processing unit 107 may perform processing using a single 1D-LUT that is a combination of these 1D-LUTs.

[0115] <Effects of this embodiment> According to this embodiment, it is possible to perform highly accurate color calibration in a printing device that prints using fluorescent ink, regardless of variations in the fluorescent whitening agent contained in the paper.

[0116] [Second embodiment] In the first embodiment, a red filter is used as the optical filter on the light receiving side when measuring light with a fluorescent pink emission wavelength using a sensor. However, the difference in ejection volume can also be estimated by using a green filter as the optical filter on the light receiving side. Figure 13(b) is a flowchart showing the calibration process in this case.

[0117] The flowchart in Figure 13(b) differs from Figure 13(a) in that it includes processing in S1304b instead of S1304a. When a red filter is used, the sensor measurement value is the value indicated by reference numeral 921 in Figure 9(c), but when a green filter is used as in this embodiment, the sensor measurement value is the value indicated by reference numeral 911 in Figure 9(d). Using the green filter makes it possible to measure the amount of light that is absorbed by ink from the light reflected by the white paper.

[0118] <Effects of this embodiment> According to this embodiment, it is possible to perform highly accurate color calibration in a printing device that prints using fluorescent ink, regardless of variations in the fluorescent whitening agent contained in the paper.

[0119] <Technical Features of the Present Disclosure> The present disclosure includes the following configurations and methods.

[0120] (Configuration 1) A printing device that performs processing related to color calibration of fluorescent ink, comprising: a printing means that prints a patch chart for estimating the amount of fluorescent ink ejected on paper containing a fluorescent whitening agent; a white light source that emits UV light; a sensor unit that has a light-receiving element that receives light emitted by the white light source and reflected by the paper on which the patch chart is printed; and a correction means that corrects the amount of fluorescent ink ejected based on the measurement results by the sensor unit; wherein patches included in the patch chart are printed with the fluorescent ink and non-fluorescent ink, and at least one dot of the non-fluorescent ink overlaps with a dot of the fluorescent ink.

[0121] (Configuration 2) The printing device according to configuration 1, wherein the emission wavelength of the fluorescent brightening agent is the excitation wavelength of the fluorescent ink.

[0122] (Configuration 3) The printing device according to configuration 1 or 2, wherein the non-fluorescent ink absorbs at least one of light in the excitation wavelength range of the fluorescent brightener and light in the emission wavelength range of the fluorescent brightener.

[0123] (Configuration 4) The printing device described in any one of configurations 1 to 3, wherein the dots of the non-fluorescent ink have a thickness and colorant concentration that can absorb light in the excitation wavelength range of the fluorescent brightener and light in the emission wavelength range of the fluorescent brightener.

[0124] (Configuration 5) The printing device according to any one of configurations 1 to 4, wherein the light receiving element receives light that includes at least a part of the excitation wavelength range and the emission wavelength range of the fluorescent ink.

[0125] (Configuration 6) The printing device according to any one of configurations 1 to 5, wherein the sensor unit further includes a filter provided in front of the light receiving element.

[0126] (Configuration 7) The printing device according to any one of configurations 1 to 6, wherein the filter cuts off light outside the excitation wavelength range of the fluorescent ink.

[0127] (Configuration 8) The printing device according to Configuration 7, wherein the fluorescent ink is fluorescent pink ink, the non-fluorescent ink is yellow ink, and the filter is a green filter.

[0128] (Configuration 9) The printing device according to any one of configurations 1 to 6, wherein the filter cuts off light outside the emission wavelength range of the fluorescent ink.

[0129] (Configuration 10) The printing device according to Configuration 9, wherein the fluorescent ink is fluorescent pink ink, the non-fluorescent ink is yellow ink, and the filter is a red filter.

[0130] (Configuration 11) The printing device according to any one of configurations 1 to 10, further comprising a control means for controlling the order in which the fluorescent ink and the non-fluorescent ink are applied.

[0131] (Configuration 12) A printing device described in any one of configurations 1 to 11, characterized in that for all dots of the fluorescent ink, each dot overlaps with one dot of the non-fluorescent ink, and the non-fluorescent ink is applied after the fluorescent ink.

[0132] (Configuration 13) The printing device according to any one of configurations 1 to 12, wherein the dots of non-fluorescent ink cover at least a portion of the dots of fluorescent ink below them.

[0133] (Configuration 14) A printing device described in any one of configurations 1 to 12, characterized in that the diameter of the fluorescent ink dot and the diameter of the fluorescent ink dot below the dot are equal, and the bottom surface of the non-fluorescent ink dot covers the entire top surface of the fluorescent ink dot below the dot.

[0134] (Configuration 15) A printing device described in any one of configurations 1 to 12, characterized in that the diameter of the non-fluorescent ink dots is larger than the diameter of the fluorescent ink dots, and the non-fluorescent ink dots cover the top and sides of the fluorescent ink dots formed below them.

[0135] (Configuration 16) A printing device described in any one of configurations 1 to 11, characterized in that for all dots of the fluorescent ink, each dot overlaps with one dot of the non-fluorescent ink, and the non-fluorescent ink is applied before the fluorescent ink.

[0136] (Configuration 17) The printing device of Configuration 16, wherein the dots of fluorescent ink cover at least a portion of the dots of non-fluorescent ink below them.

[0137] (Configuration 18) A printing device as described in Configuration 16, characterized in that the diameter of the fluorescent ink dot and the diameter of the fluorescent ink dot below the dot are equal, and the bottom surface of the fluorescent ink dot covers all of the top surface of the non-fluorescent ink dot below the dot.

[0138] (Configuration 19) A printing device as described in Configuration 16, characterized in that the diameter of the non-fluorescent ink dots is larger than the diameter of the fluorescent ink dots, and the upper surfaces of the non-fluorescent ink dots cover all of the lower surfaces of the fluorescent ink dots formed on top of them.

[0139] (Method 1) A color calibration method executed in a printing device, comprising the steps of: printing, by a printing means, a patch chart for estimating the amount of fluorescent ink ejected on paper containing a fluorescent whitening agent; emitting light including UV light using a white light source; receiving, by a light-receiving element provided in a sensor unit, the light emitted from the white light source and reflected by the paper on which the patch chart is printed; and correcting the amount of fluorescent ink ejected based on the measurement results by the sensor unit; wherein the patches included in the patch chart are printed using the fluorescent ink and non-fluorescent ink, and at least one dot of the non-fluorescent ink overlaps with a dot of the fluorescent ink.

[0140] [Other embodiments] In the above-described embodiment, the printing method of the printing device is an inkjet method, but the printing method that can be adopted is not limited to this, and other printing methods such as electrophotography and thermal transfer may also be used.

[0141] In the above-described embodiment, reflection coefficients are used to explain the measurement values ​​of the sensors, but density or color values ​​calculated from reflection coefficients (for example, CIE L*a*b*, tristimulus values ​​XYZ, etc.) may also be used.

[0142] In the above embodiment, the gradation patches are described as patch charts for calibration, but a correction table may be generated by estimating a specific gradation ejection amount.

[0143] In the above embodiment, the photodiode is described as the light receiving element of the color sensor, but a phototransistor or the like may also be used.

[0144] In the above embodiment, a configuration in which the color sensor is mounted on the side of the carriage has been described, but the color sensor may be mounted in another location or may be configured to allow manual measurement.

[0145] In the above-described embodiment, red, green, and blue LEDs were used as the LEDs of the color sensor, but LEDs of other colors may also be used, and the number of colors is not limited to three; it may be more than three or less than three.

[0146] In the above-described embodiment, yellow ink is used as the non-fluorescent ink to be mixed in to mitigate the effects of the fluorescent brightening agent, but any other color ink may be used as long as it has the properties of absorbing light in the excitation wavelength range of the fluorescent brightening agent and light in the emission wavelength range of the fluorescent brightening agent.

[0147] The present disclosure can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions. [Explanation of symbols]

[0148] 407 Printer 409 Printer control unit 411 Printing Department 412 Sensor unit 601 White light source that emits light including UV light 602 Photodetector 603 Optical Filter 604 Printed matter 1001 Printing paper 1002 fluorescent ink dots 1101 Non-fluorescent ink dots

Claims

1. a printing means for printing a patch chart for estimating the amount of fluorescent ink ejected on a recording medium containing a fluorescent whitening agent; a white light source that emits UV light; a sensor unit including a light receiving element that receives light emitted by the white light source and reflected by the recording medium on which the patch chart is printed; a correction unit that corrects the amount of the fluorescent ink applied based on the measurement result by the sensor unit; having the patches included in the patch chart are printed with the fluorescent ink and a non-fluorescent ink, and at least one dot of the non-fluorescent ink overlaps with a dot of the fluorescent ink; A printing device comprising:

2. The emission wavelength of the fluorescent brightener is the excitation wavelength of the fluorescent ink.

2. The printing device according to claim 1.

3. the non-fluorescent ink absorbs at least one of light in an excitation wavelength range of the fluorescent brightening agent and light in an emission wavelength range of the fluorescent brightening agent; 3. The printing device according to claim 2.

4. the dots of the non-fluorescent ink have a thickness and a colorant concentration that can absorb light in the excitation wavelength range of the fluorescent brightening agent and light in the emission wavelength range of the fluorescent brightening agent; 4. The printing device according to claim 3.

5. the light receiving element receives light including at least a part of an excitation wavelength range and an emission wavelength range of the fluorescent ink; 4. The printing device according to claim 3.

6. The sensor unit further includes a filter provided in front of the light receiving element.

6. The printing apparatus according to claim 5.

7. The filter cuts off light other than the excitation wavelength range of the fluorescent ink.

7. The printing apparatus according to claim 6.

8. the fluorescent ink is a fluorescent pink ink, the non-fluorescent ink is a yellow ink, The filter is a green filter.

8. The printing apparatus according to claim 7.

9. the filter cuts off light outside the emission wavelength range of the fluorescent ink; 7. The printing apparatus according to claim 6.

10. the fluorescent ink is a fluorescent pink ink, the non-fluorescent ink is a yellow ink, The filter is a red filter.

10. The printing device according to claim 9.

11. The method further includes a control unit for controlling the order in which the fluorescent ink and the non-fluorescent ink are applied.

2. The printing device according to claim 1.

12. for every dot of the fluorescent ink, each dot overlaps with one dot of the non-fluorescent ink; The non-fluorescent ink is applied after the fluorescent ink.

12. The printing device according to claim 11.

13. the dots of non-fluorescent ink cover at least a portion of the dots of fluorescent ink underneath the dots of non-fluorescent ink; 13. The printing device according to claim 12.

14. the diameter of the fluorescent ink dot is equal to the diameter of the fluorescent ink dot below the fluorescent ink dot, a lower surface of the dot of non-fluorescent ink covers all of the upper surface of the dot of fluorescent ink below the lower surface of the dot of non-fluorescent ink; 13. The printing device according to claim 12.

15. a diameter of the dots of the non-fluorescent ink is larger than a diameter of the dots of the fluorescent ink; the dots of the non-fluorescent ink cover the top and side surfaces of the dots of the fluorescent ink formed below the dots of the non-fluorescent ink; 13. The printing device according to claim 12.

16. for every dot of the fluorescent ink, each dot overlaps with one dot of the non-fluorescent ink; The non-fluorescent ink is deposited prior to the fluorescent ink.

12. The printing device according to claim 11.

17. the dots of fluorescent ink cover at least a portion of the dots of non-fluorescent ink underneath them; 17. The printing device according to claim 16.

18. the diameter of the fluorescent ink dot is equal to the diameter of the fluorescent ink dot below the fluorescent ink dot, a lower surface of the dot of fluorescent ink covers all of the upper surfaces of the dots of non-fluorescent ink below the dot of fluorescent ink; 17. The printing device according to claim 16.

19. a diameter of the dots of the non-fluorescent ink is larger than a diameter of the dots of the fluorescent ink; an upper surface of the dot of the non-fluorescent ink covers an entire lower surface of the dot of the fluorescent ink formed thereon; 17. The printing device according to claim 16.

20. a control means for controlling the printing means to print patches using a fluorescent ink on a recording medium containing a fluorescent whitening agent; a correction means for correcting an amount of the fluorescent ink applied based on a measurement result obtained by receiving light reflected from the recording medium on which the patch is printed; and having the patch is printed with the fluorescent ink and a non-fluorescent ink, and at least one dot of the fluorescent ink overlaps a dot of the non-fluorescent ink; 23. An information processing apparatus comprising:

21. printing a patch chart for estimating the amount of fluorescent ink ejected on a recording medium containing a fluorescent whitening agent by a printing means; emitting light including UV light using a white light source; receiving light emitted from the white light source and reflected by the recording medium on which the patch chart is printed, by a light receiving element included in a sensor unit; correcting the amount of the fluorescent ink applied based on the measurement result by the sensor unit; having the patches included in the patch chart are printed with the fluorescent ink and a non-fluorescent ink, and at least one dot of the non-fluorescent ink overlaps with a dot of the fluorescent ink; A method comprising:

22. A program for causing a computer to execute the method according to claim 21.

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