Printing apparatus, color calibration method, 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 apparatus, a method for color calibration, and a program.

Background Art

[0002] Conventionally, color calibration is known in which a printed patch is read by a measuring instrument, the discharge amount is estimated from the read density, and the amount of ink discharged is changed according to the estimation result to match the color density between printing apparatuses.

[0003] There are roughly two types of measuring instruments used for color calibration. The first is a spectrophotometer, which obtains the color density and color values (e.g., CIE L*a*b*, tristimulus values XYZ, etc.) by receiving light that has been spectrally separated using a white light source having wavelengths in the light regions of UV light and visible light and a diffraction grating. The second is a density sensor. There are two methods used in density sensors. One method is to obtain the reflection coefficient using a light source having a bandwidth at a predetermined wavelength (e.g., an LED light source having peaks in the wavelength regions of red, green, and blue) and a light receiving element (e.g., a photodiode), thereby obtaining the density characteristics of red, green, and blue. The other method is to use a white light source (e.g., an LED having a spectral distribution in the visible light region) and an optical filter in front of the light receiving element (e.g., an optical filter having a spectral sensitivity distribution in the wavelength regions of red, green, and blue, etc.). In this method, the density characteristics are obtained by obtaining the reflection coefficient of the light spectrally separated into red, green, and blue.

[0004] Regardless of whether a spectrophotometer or a density sensor is used as the measuring instrument, when calibrating by printing a patch of fluorescent ink on paper containing a fluorescent whitening agent, caution is required when using a light source that emits light containing UV light such as a white light source as the light source of the measuring instrument. The reason is that the amount of light emitted by the fluorescent whitening agent changes due to variations in the fluorescent whitening agent contained in the paper, making it difficult to determine whether the change in the measurement value by the measuring instrument is due to a change in the ink discharge amount or due to variations in the fluorescent whitening agent.

[0005] Patent Document 1 discloses a technique related to the color calibration of fluorescent ink, which involves correcting the measured density detected by an optical sensor according to the fluorescence information of the ink, and creating a color shift correction table based on density characteristics similar to those of the human eye. Specifically, it involves performing a correction that assigns a weight to the measured density similar to that of the human eye. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2014-136413 [Non-patent literature]

[0007] [Non-Patent Document 1] Lecture: Dye Chemistry for Dyeing Technicians (Part 10) by Kunihiko Imada, Journal of the Textile Machinery Society: Sen'i Vol. 56 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, as mentioned above, even if the amount of ink ejected by the printer does not change, variations in the fluorescent whitening agent contained in the paper can cause the measurement value of the measuring instrument to change, which could lead to misinterpreting variations in the fluorescent whitening agent as changes in the amount of ink ejected.

[0009] In particular, when the target of calibration is fluorescent ink, changes in the luminescence amount of the fluorescent whitening agent promote changes in the luminescence amount of the fluorescent ink, making the impact on the measured value more complex. As a result, even if weights based on visual characteristics are assigned to the sensor readings as in Patent Document 1, it is not possible to improve the accuracy of the sensor readings, and there is a problem that the accuracy of the calibration correction decreases.

[0010] Therefore, in view of the above issues, this disclosure aims to enable high-precision color calibration in a printing apparatus that uses 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 apparatus comprising: printing means for printing a patch chart for estimating the amount of fluorescent ink ejected onto a recording medium containing a fluorescent whitening agent; a white light source emitting UV light; a sensor unit equipped with 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; and correction means for correcting the amount of fluorescent ink impregnated based on the measurement results from the sensor unit, wherein the patches included in the patch chart are printed with the fluorescent ink and non-fluorescent ink, at least one dot of the non-fluorescent ink overlaps with a dot of the fluorescent ink, and the apparatus further comprises control means for controlling the order in which the fluorescent ink and the non-fluorescent ink are applied. [Effects of the Invention]

[0012] According to this disclosure, it is possible to perform high-precision color calibration in a printing apparatus that prints using fluorescent ink with high accuracy, regardless of variations in the fluorescent whitening agent contained in the paper. [Brief explanation of the drawing]

[0013] [Figure 1] Block diagram showing the configuration related to color conversion processing within the image processing unit. [Figure 2] A diagram showing a patch chart. [Figure 3] Diagram explaining 1D-LUT data [Figure 4] Printing system configuration diagram [Figure 5] Diagram showing how the sensor unit reads the patch chart. [Figure 6] Diagram explaining the sensor unit [Figure 7]Diagram of the excitation wavelength and emission wavelength of the fluorescent ink, and the spectral reflectance of the non-fluorescent ink [Figure 8] Diagram of spectral reflectance [Figure 9] Diagram showing the result of measuring the gradation patch for calibration with a color sensor [Figure 10] Diagram for explaining the case of measuring a sample printed with fluorescent ink on paper containing a fluorescent whitening agent [Figure 11A] Diagram schematically showing the printing method of the fluorescent ink and the non-fluorescent ink [Figure 11B] Diagram schematically showing the printing method of the fluorescent ink and the non-fluorescent ink [Figure 11C] Diagram schematically showing the printing method of the fluorescent ink and the non-fluorescent ink [Figure 11D] Diagram schematically showing the printing method of the fluorescent ink and the non-fluorescent ink [Figure 11E] Diagram schematically showing the printing method of the fluorescent ink and the non-fluorescent ink [Figure 11F] Diagram schematically showing the printing method of the fluorescent ink and the non-fluorescent ink [Figure 11G] Diagram schematically showing the printing method of the fluorescent ink and the non-fluorescent ink [Figure 12] Flowchart of the process for determining the amount of non-fluorescent ink to be injected [Figure 13] Flowchart of the calibration process

Mode for Carrying Out the Invention

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

[0015] The first method involves printing single-color gradation patches and generating a table to correct the ink amount so that each density of the gradation patch matches the target density. The second method involves estimating the ejection amount from the density of at least one printed patch and applying the appropriate correction table from the pre-stored correction tables according to the estimated ejection amount. Here, the correction table refers to a table that changes the amount of ink printed by each ink (number of dots, dot diameter, etc.) (see Figure 3(c)). Below, we will describe an example using the first method, gradation patches.

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

[0017] The printer has six inks as colorants: 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, a combination of R (red), Or (orange), B (blue) and a special color ink such as Gy (gray) is also acceptable, or Lc (light cyan), which is a diluted C (cyan), and Lm (light magenta), which is a diluted M (magenta). Furthermore, FB (fluorescent blue) or FY (fluorescent yellow) may be used instead of FP (fluorescent pink).

[0018] <Regarding the configuration related to color conversion processing> Figure 1 is a block diagram showing the configuration of the image processing unit related to color conversion in this embodiment. The printer in this embodiment is assumed to have the functionality of both an RGB printer with RGB signal input and a CMYK printer with CMYK signal input. For the sake of explanation, the image data is assumed to be processed as 8-bit signal values ​​for each color. However, it goes without saying that similar effects can be obtained even if the pixel value of each pixel in the image data is multi-bit, such as 10-bit, 12-bit, or 16-bit representation.

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

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

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

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

[0023] Regarding the aforementioned processing units, the color matching processing unit 102 and the color separation processing unit 104 each perform color conversion processing using a 3D-LUT. The color matching processing unit 103 and the 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 the color separation processing unit 104 consists of 16 grids with 17 count intervals for each color, resulting in a 3D-LUT with 16 x 16 x 16 = 4096 grids.

[0024] As shown in Figure 1, the image processing unit includes a calibration processing unit 107. The calibration processing unit 107 corrects for color variations in the printed result caused by individual differences in the devices, recording media, and colorants that make up the printer, as well as variations in the ejection amount due to changes in the devices over time. Specifically, the calibration processing unit 107 performs processing using a 1D-LUT for each color signal of the colorants. The reason for this processing is to match the density value of the printed area relative to the input data value of the actual printing press to the calibration target value, which is the density value of the printed area relative to the input value of the reference machine (on the production line).

[0025] In this embodiment, the printing device is shown to have an image processing unit, but the image processing unit may be provided separately from the printing device. For example, an information processing device such as a personal computer may perform the function of the image processing unit.

[0026] <About patch charts> Figure 2 shows a patch chart used during calibration to measure the actual print density values ​​for predetermined input data values, representing the print results from an actual printing device. This patch chart has multiple patches for each ink.

[0027] In the cyan, magenta, yellow, black, and green patches, the input signal for each colorant is varied in 20% increments. By measuring the color of the printed patch chart, the corresponding ejection amount for each colorant in the printer can be estimated. For example, patch P20 for cyan is printed with cyan ink only, patch P201 is 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 pigment with the input signal varied in 20% increments, and yellow pigment with a fixed input signal. In other words, the fluorescent pink patch P21 shown in Figure 2 is printed with fluorescent pink and yellow ink.

[0029] <About Calibration> Figure 3(a) is a diagram illustrating the 1D-LUT data used in the calibration processing unit 107 of Figure 1. Figure 3(a) shows an example with one ink type on a certain media, where the vertical axis represents the print density value of the printed area read by the sensor, and the horizontal axis represents the density (%) when printing the patch.

[0030] The "print density" refers to the percentage of ink dots printed on the paper. Here, we will explain using an inkjet printer with a resolution of 1200 dpi x 1200 dpi as an example. If we define one grid as an area where one dot is printed at 1200 dpi x 1200 dpi, then 100% means that one dot is printed in all of the grids. Conversely, 200% means that two dots are printed in each of the 1200 dpi x 1200 dpi grids (twice the number of dots printed compared to 100%). Note that the position where a dot is printed does not necessarily have to be in the center of the grid; dots may be printed between grids.

[0031] When the amount of material injected is X%, the density value is given by the reflection coefficient output by the sensor, where P(X) is... D(X)=-log(P(X) / P(0))...Equation 1 It can be defined as follows: Here, P(0) is the reflectance coefficient of the patch in the white area of ​​the paper.

[0032] Furthermore, if it is printed by mixing it with ink of a certain amount C%, D(X)=-log(P(X) / P(C))...Equation 2 It can be defined as follows: Here, P(C) is the reflectance coefficient of ink with a certain amount of ink (C%).

[0033] The curve shown by the dashed line 301 in Figure 3(b), etc., represents the print density value of the colorant at the reference machine relative to the input data value, and indicates the calibration target value. The reference machine is a standard printer, and its output volume is the center of the variation in the output volume of the actual machine. Information regarding such calibration target values ​​is pre-stored in the memory means of each printer within the system.

[0034] The curve shown by solid line 302 represents the print density values ​​of the colorants on the actual machine. The actual machine is the printer used for calibration. This information is obtained by printing the patch chart shown in Figure 2 and reading the printed patch chart with a sensor. D0 to D6 represent the density (calculated using Equation 1) corresponding to each patch on the patch chart in 20% increments from 0% to 120%. Solid line 302 was derived using interpolation and approximation curves based on the measured values ​​of D0 to D6.

[0035] As shown in the print status of the actual machine in Figure 3(a), the actual machine generally produces a larger amount of colorant than the reference machine, and in particular, prints darker than the reference machine in the intermediate density range. The correction in the calibration processing unit 107 involves converting and correcting the contrast color presence signals for each colorant so that they match the print density of the reference machine. 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] The plot point D2 in Figure 3(b) shows the density value when printing a patch with a 40% density on the actual machine, as shown in the patch chart in Figure 2. This value is higher than the target density value shown at plot point T2, which corresponds to the same density. Therefore, it is necessary to reduce the density to match the density value on the actual machine to the target density value. Specifically, the density value at T2 is determined by searching along the solid line 302 and finding point DY. In other words, when using the actual machine, the printed density value will be approximately equal to the target density value when printed with the density 303 shown at point DY.

[0037] The processing described above for plot point D2 is applied to all plot points D0 to D6, and then interpolation or approximation curves are used. This makes it possible to generate 1D-LUT data, which represents the relationship between the input amount (%) and the output input amount (%), as shown in Figure 3(c). A 1D-LUT is a correction parameter that can be defined by discrete values ​​such as 256 points or 1024 points, or by mathematical formulas that can be defined by curves.

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

[0039] PC401 performs control operations for the printer 407 as described below, according to various software programs. The storage means 405 stores system programs, application software programs, software programs necessary for printing operations, and software programs necessary for the operations described below. The storage means 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 PC401. The storage means 405 is typified by a hard disk or flash ROM. The CPU 403 executes predetermined processing using the work area of ​​the working memory 404 according to the various programs and data stored in the storage means 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 a means of operation for the user, processes user input and output (display, etc.) to the user, and includes input devices such as a keyboard and mouse, and display devices such as a display.

[0042] The printer 407 comprises 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 material. 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 regarding the results of printing, sensor measurements, etc., stored in the storage means within the printer, and sends the read information to the PC 401. The printer control unit 409 consists 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 controls the printing operation as well as the measurement performed by the sensor unit 412.

[0043] <About color sensors> Figure 5 shows an example of the configuration of the sensor unit 412 in the printer 407. The carriage 503 forms a patch image 502 by ejecting ink while scanning the paper 501 from left to right. A sensor member 504 is mounted next to the carriage 503.

[0044] <Regarding the light source and optical filter of the color sensor's light receiving sensor> Figure 6(a) shows a schematic configuration of the sensor unit. The sensor unit includes a white light source 601 that emits light including UV light, and a light-receiving element 602 for receiving light reflected by the printed material 604. The sensor unit also includes an optical filter 603 provided in front of the light-receiving element 602. There are two purposes for using this optical filter.

[0045] One reason is to select complementary colors to receive light with a wide range of wavelengths for density discrimination. In other words, a red filter is selected for cyan and green, a green filter for magenta, fluorescent pink, and black, and a blue filter for yellow, and then measurements are taken.

[0046] Another reason is that when light is shone on fluorescent ink or similar material, the light at the excitation wavelength that is absorbed and the light emitted at wavelengths 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 type is an LED with peaks in the red, green, blue, and UV wavelength ranges, and Figure 6(b) shows the spectral intensity distribution as the spectral emission characteristic 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 consists of white LEDs and UV LEDs with spectral distributions in the visible light range. Figure 6(c) shows the spectral intensity distribution as a spectral emission characteristic of the 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 wavelength range. Figure 6(d) shows the spectral intensity distribution as the spectral emission characteristic of the tungsten light source, indicated by symbol 631.

[0050] Figure 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 the blue filter, which cuts out light other than blue light; reference numeral 642 indicates the spectral sensitivity distribution of the green filter, which cuts out light other than green light; and reference numeral 643 indicates the spectral sensitivity distribution of the red filter, which cuts out light other than red light. Note that the green filter is a filter that cuts out light outside the excitation wavelength range of the fluorescent pink ink, and the red filter is a filter that cuts out light outside the emission wavelength range of the fluorescent pink ink.

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

[0052] Element 702 represents the intensity of light received from the recording sample at each wavelength when the recording sample is irradiated with light of the excitation wavelength. Figure 7 shows a graph for fluorescent pink in this embodiment when 480 nm light is irradiated onto the recording sample.

[0053] Excitation 701 represents the intensity of the received light when the wavelength of the light irradiating the recording sample is changed while the wavelength of the received light is fixed. Figure 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 in which the fluorescent ink recorded on the paper is excited overlaps with the wavelength range in which it emits light, but is on the shorter wavelength side. Furthermore, the excitation 701 has varying intensity depending on the wavelength, with some wavelengths being efficiently emitted and others not. Also, since the fluorescent colorant emits light, the reflectance at the emission wavelength is often greater than 1. In this embodiment, a colorant having the above characteristics is defined as a fluorescent colorant.

[0055] The excitation and emission of fluorescent pink ink were described above, but in this embodiment, fluorescent inks that emit light at other wavelengths may be used. 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). 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, a combination of the aforementioned fluorescent inks may be used. In addition, the color tone may be adjusted by combining fluorescent inks with different excitation wavelength intensities. For example, a fluorescent pink ink that is weakly excited in the blue region, strongly excited in the green region, and emits light in the orange region may be used.

[0056] In this embodiment, non-fluorescent ink is defined as an ink containing a colorant that absorbs light of a specific wavelength and does not emit light when exposed to it. For example, the spectral reflectance of non-fluorescent ink is as shown in Figure 7 for cyan (C) 703, magenta (M) 704, and yellow (Y) 705. Unlike fluorescent ink, non-fluorescent ink only absorbs light, so its reflectance will never exceed 1.

[0057] <About fluorescent ink> Next, the fluorescent ink used in this embodiment will be described. In this embodiment, a fluorescent ink prepared by mixing a dispersion having fluorescent properties, a solvent, and an activator is used. The fluorescent dispersion used in this embodiment is a dispersion having fluorescent properties. For example, NKW-3207E (fluorescent pink aqueous dispersion: Nippon Fluorescent Chemical Co., Ltd.), NKW-3205E (fluorescent yellow aqueous dispersion: Nippon Fluorescent Chemical Co., Ltd.), etc., can be used, but any dispersion having fluorescent properties is acceptable. The dispersion having fluorescent properties contains a fluorescent dye, and it is preferable that the content (mass%) of the fluorescent dye in the ink is 0.1% by mass or more and 5.0% by mass or less.

[0058] The above-mentioned fluorescent dispersion is dispersed into an ink by combining it with a known solvent and activator. The dispersion method of the fluorescent dispersion is not particularly limited. For example, a fluorescent dispersion dispersed with a surfactant, a resin-dispersed fluorescent dispersion dispersed with a dispersion resin, etc., can be used. Of course, it is also possible to use a combination of fluorescent dispersions with different dispersion methods. The surfactant can be anionic, nonionic, cationic, or amphoteric activators. Any water-soluble or water-dispersible resin can be used as the dispersion resin, but among them, a dispersion resin with a weight-average molecular weight of 1,000 to 100,000, and more preferably 3,000 to 50,000, is preferred. As for the solvent, it is preferable to use an aqueous medium containing, for example, water and a water-soluble organic solvent.

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

[0060] Furthermore, some inkjet recording media contain fluorescent whitening agents to make the paper appear whiter. As described in Non-Patent Literature 1, fluorescent whitening agents absorb ultraviolet light (330-380 nm) and emit fluorescence (blue light) in the short wavelength range of the visible spectrum (400-450 nm). They are compounds that have an affinity for fibers and belong to a genus of dyes. Since there are no white dyes, fluorescent whitening agents are used to make the paper appear whiter.

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

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

[0063] First, we will describe an example of reading a magenta gradation patch. Figure 8(a) shows the spectral reflectance of the ink 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), code 801 represents the reflectance of white paper, and codes 802 to 807 represent the reflectance of calibration patches modulated in 20% increments.

[0064] As mentioned above, the color sensor of this embodiment irradiates light in the visible light range (300-700 nm) including UV, and limits the wavelength range of the received light with an optical filter. However, when measuring magenta patches, a green filter is used for measurement. When the amount of magenta ink is changed, the change in reflectance is large around 540 nm. Therefore, by using a green filter when the sensor receives light, the sensor can 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 using a color sensor.

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

[0066] Next, we will describe an example of reading a fluorescent pink gradient patch. Figure 8(b) shows the spectral reflectance of ink 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 white paper, and reference numerals 812 to 817 indicate the spectral reflectance of calibration patches with the ink density modulated in 20% increments.

[0067] When measuring with a color sensor, light in the visible light range (300-700 nm), including UV light, is used. To perform accurate measurements, it is necessary to use an optical filter to separate the wavelength range of the received light for measurement. 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 describe an example of receiving light in the excitation wavelength range. As mentioned earlier, since the reflectivity of fluorescent pink ink changes significantly around λ=540nm, where it absorbs irradiated light, a green filter is used as the optical filter when receiving the light (see Figure 6(e)). In this case, the amount of reduction in light absorbed by the ink from the reflected light of the white paper can be measured. The result measured by the sensor at this time is shown by the symbol 911 in Figure 9(b).

[0069] Next, we will describe an example of receiving light in the emission wavelength range. As mentioned earlier, since fluorescent pink light emits fluorescence around λ=600nm, a red filter is used as the optical filter when receiving the light (see Figure 6(e)). The results measured by the sensor at this time are shown by the symbol 921 in Figure 9(c).

[0070] However, in the case of paper containing a fluorescent whitening agent, variations in the fluorescent whitening agent will affect the measured value. Specifically, if the fluorescent whitening agent deteriorates over time, the measured value will be smaller than before the deterioration. As an example of such a change in measured value, Figure 9(d) shows the case when light of the excitation wavelength 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 when light of the emission wavelength 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 described in detail using Figure 10, which shows a simplified reflection model and the results measured with a spectrophotometer.

[0072] Figure 10(a) shows a simplified 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 printed with fluorescent ink on paper is irradiated with light containing UV light, half of the irradiated light 1003 is reflected by the ink layer and released into the air as first reflected light 1004. The other half becomes incident light 1005 that enters the paper, is reflected inside the paper, then re-enters the ink layer and is released into the air as second reflected light 1006. The measuring instrument measures the combined light of the first reflected light 1004 and the second reflected light 1006. In reality, complex light absorption and scattering occur within the ink and paper, but for simplicity, these are omitted in this embodiment.

[0074] As shown in Figure 10(b), when UV light 1012 with a wavelength range of 330-380 nm is irradiated onto paper 1011 containing a fluorescent whitening agent, blue light 1013 in the wavelength range of 400-450 nm is emitted from the paper. Therefore, paper containing a fluorescent whitening agent has a greater amount of light reflected from the paper, i.e., the amount of blue light in the second reflected light 1006 shown in Figure 10(a), compared to paper without a fluorescent whitening agent. As a result, both 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 of patches printed with fluorescent pink ink on paper containing a fluorescent whitening agent and paper without a fluorescent whitening agent, measured using a spectrophotometer. "Canon Photo Paper Glossy Pro [Platinum Grade]" was used as the paper containing the fluorescent whitening agent, and "Canon Glossy Type Roll Paper (Double-Sided)" was used as the paper without the fluorescent whitening agent; both are resin-coated papers. In Figure 10(c), the spectral reflectance of the paper containing the fluorescent whitening agent is indicated by reference numeral 1021, and the spectral reflectance of the paper without the fluorescent whitening agent is indicated by reference numeral 1022.

[0076] Although there are differences in paper types, paper containing a fluorescent whitening agent increases the amount of light in the blue wavelength range contained in the second reflected light 1006, which is the light reflected from the paper surface. As a result, as the second reflected light 1006 passes through the layer of fluorescent ink dots 1002, the amount of green reflected light (symbol 1023), which is the excitation wavelength light, and furthermore, the excited and emitted red reflected light (symbol 1024), are greater than in paper without a fluorescent whitening agent. This result indicates that when paper containing a fluorescent whitening agent is used and the fluorescent component in the paper deteriorates over time, the excitation wavelength light and emission wavelength light decrease.

[0077] Next, Figure 10(d) shows the spectral reflectance when patches printed with fluorescent pink after being pre-printed with yellow ink on each type of paper were measured using a spectrophotometer. In Figure 10(d), the spectral reflectance of paper containing a fluorescent whitening agent is indicated by reference numeral 1031, and the spectral reflectance of paper without a fluorescent whitening agent is indicated by reference numeral 1032.

[0078] We compare the case where yellow ink is not printed (Figure 10(c)) with the case where yellow ink is printed (Figure 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 are both smaller when yellow ink is printed than when yellow ink is not printed. In other words, by pre-printing yellow ink, it is possible to suppress the concentration changes measured by the sensor caused by variations in the fluorescent whitening agent (manufacturing lot differences, aging degradation).

[0079] <Regarding non-fluorescent inks to be mixed and how to apply the ink> The following describes how to apply non-fluorescent inks in a mixed printing process, using Figures 11A to 11F. In Figures 11A to 11F, the upper figure is a top view of the printed paper 1001 with the ink printed on it. The lower figure, on the other hand, corresponds to the upper figure and shows a cross-section of the printed paper 1001 with the ink printed on it, viewed from the side.

[0080] To mitigate the effects of the fluorescent whitening agent, it is desirable that the non-fluorescent ink used for mixing is an ink that absorbs light at the excitation or emission wavelength of the fluorescent whitening agent. Furthermore, as shown in Figure 11A or Figure 11B, it is desirable that at least one dot 1101 of the non-fluorescent ink used for mixing overlaps with a dot 1002 of the fluorescent ink. In addition, as shown in Figure 11A, the non-fluorescent ink may be printed after the fluorescent ink, or as shown in Figure 11B, it may be printed beforehand.

[0081] Next, we will explain in detail the methods of playing after the opponent and playing before the opponent.

[0082] For example, in printer 407, the order in which each ink is applied to the same area is controlled so that non-fluorescent ink is applied to the same location where fluorescent ink has been applied. This ensures that dots of non-fluorescent ink cover at least a portion of the fluorescent ink dots below them (post-application of non-fluorescent ink). Alternatively, the order in which each ink is applied to the same area is controlled so that fluorescent ink is applied to the same location where non-fluorescent ink has been applied. This ensures that non-fluorescent ink is covered by fluorescent ink (pre-application of non-fluorescent ink).

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

[0084] In other words, as shown in Figure 11C, it is desirable that the non-fluorescent ink dots 1101 to be mixed are printed so that they overlap all of the fluorescent ink dots 1002. In Figure 11C, the dot diameter of the non-fluorescent ink dots 1101 and the dot diameter of the fluorescent ink dots 1002 are equal, and the entire upper surface of the fluorescent ink dots 1002 is covered by the lower surface of the non-fluorescent ink dots 1101.

[0085] Alternatively, as shown in Figure 11D, it is desirable to print the fluorescent ink dots 1002 so that they overlap with all of the non-fluorescent ink dots 1101. In Figure 11D, the dot diameter of the non-fluorescent ink dots 1101 is equal to that of the fluorescent ink dots 1002, 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 consider the spread of reflected light due to scattering within the paper after the irradiated light passes through the fluorescent ink (indicated by reference numeral 1102). Specifically, it is desirable that the paper be covered 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 applied after the fluorescent ink (Figure 11F) or before it (Figure 11G). In Figure 11F, the dot diameter of the non-fluorescent ink dot 1101 is larger than that of the fluorescent ink dot 1002, and the top and sides of the fluorescent ink dot 1002 are covered by the non-fluorescent ink dot 1101. On the other hand, in Figure 11G, the dot diameter of the non-fluorescent ink dot 1101 is larger than that of the fluorescent ink dot 1002, and the bottom surface of the fluorescent ink dot 1002 is covered by the top surface of the non-fluorescent ink dot 1101.

[0088] Furthermore, it is desirable that the non-fluorescent ink dots 1101, which are mixed and printed, have sufficient thickness and colorant density to absorb light at the excitation wavelength and emission wavelength of the fluorescent whitening agent.

[0089] <How to determine the amount of ink to mix for printing> The process for determining the amount of ink to be mixed and applied will be explained below using Figure 12.

[0090] In step S1201, print a calibration patch for the fluorescent ink onto paper containing a fluorescent whitening agent. Hereafter, for simplicity, "step S~" will be abbreviated as "S~".

[0091] Using S1202, print a calibration patch for the fluorescent ink onto paper that does not contain fluorescent whitening agents.

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

[0093] Furthermore, the target density difference for the calibration of the fluorescent ink is defined. In addition, errors that occur during the calibration process are 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 Defined as such, the concentration difference that fluctuates during the measurement process is ΔOD 測定誤差 This is how it is defined. Let's assume that.

[0094] In S1204, determine whether the following equation 3 is satisfied. JPEG0007898925000001.jpg16150

[0095] If the result of the judgment in S1204 is true, the series of processes ends. On the other hand, if the result of the judgment 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 for printing is increased by a predetermined amount. Then, the process returns to S1201, and the patch printing and other processes are performed again.

[0097] The series of processes described above allows us to determine the optimal amount of non-fluorescent ink to be applied. 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 I've listed these two as examples, but the margin of error is not limited to these.

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

[0099] Furthermore, while concentration is used as the quantitative evaluation value for ink ejection volume, this is not the only quantitative evaluation value; 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 Figure 13. This process is executed by the CPU 403 and the like according to the calibration process program stored in the storage means 405 in Figure 4. The parameters required for the calibration process are input via the UI means 402.

[0101] Print the calibration patch chart using S1301. This section describes the process of printing the calibration patch chart shown in Figure 2. First, create patches with varying input levels from 0% to 120% in 20% increments. In this example, as shown in Figure 2, patches with varying input levels from 0% to 120% in 20% increments are used, but increments other than 20% are also acceptable, and the maximum input level may also be other than 120%.

[0102] Next, it is checked whether the patch chart shown in Figure 2 has been created for all the inks to be patched. If it has been completed, the patch chart data is stored in the storage device 405.

[0103] Then, information related to printing on the media (paper, etc.) is read from the storage means 405, and the read information is transmitted to the printer 407. Similarly, 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 color material color signal image signal I / F 101 (see Figure 1), and the subsequent half-toning process is performed directly. After that, it is printed by the printing unit 411.

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

[0105] Next, the process of measuring each patch included in the printed patch chart (S1302-S1306) 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 result of this step is true, proceed to S1303. On the other hand, if the result of this step is false, proceed to S1305.

[0106] In S1303, the printer control unit 409 shines light onto the patch that has a spectral distribution in a wavelength range that includes the excitation wavelength and emission wavelength of the fluorescent ink.

[0107] In S1304a, the printer control unit 409 obtains the measurement result of the sensor unit 412 by reading 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. Specifically, the reflection intensity of the patch is read in the manner described above in <About Patch Printing and Measurement>.

[0108] In this embodiment, the light used to irradiate the calibration patch during the calibration process is selected. However, the measurement may also be performed according to the conditions for the irradiated light that are stored in the storage means 405 beforehand.

[0109] In S1305, the printer control unit 409 shines light onto the patch with a spectral distribution in a wavelength range where the change in the spectral reflectance of the ink in response to the change in ejection amount is large, and reads the reflection intensity with the sensor unit 412 to obtain the measurement result of the sensor unit 412.

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

[0111] Next, we will explain the process of actually performing calibration (S1307~S1309). First, in S1307, the printer control unit 409 estimates the ejection amount based on the reflectance intensity read by the patch measurement.

[0112] In S1308, the printer control unit 409 corrects the ink load based on the estimation result in S1307. Specifically, this is done in the manner described in <About Calibration Execution> above, 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 the calibration for all ink colors has been completed. If the result of this step is true, the series of processes ends. On the other hand, if the result of 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 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 combines these 1D-LUTs.

[0115] <Effects of this embodiment> According to this embodiment, high-precision color calibration in a printing apparatus that prints using fluorescent ink can be performed accurately without being affected by 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 receiving side when measuring light of the emission wavelength of fluorescent pink with a sensor. However, the difference in emission amount can also be estimated by using a green filter as the optical filter on the receiving side. Figure 13(b) is a flowchart of the calibration process in that case.

[0117] The flowchart in Figure 13(b) differs from that in Figure 13(a) in that it includes the process S1304b instead of S1304a. When a red filter is used, the sensor measurement value is the value indicated by the symbol 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 the symbol 911 in Figure 9(d). By using a green filter, it is possible to measure the amount of reduction in light absorbed by the ink from the reflected light of the white of the paper.

[0118] <Effects of this embodiment> According to this embodiment, high-precision color calibration in a printing apparatus that prints using fluorescent ink can be performed accurately without being affected by variations in the fluorescent whitening agent contained in the paper.

[0119] <Technical Features of This Disclosure> This disclosure includes the following configuration and method:

[0120] (Configuration 1) A printing apparatus for performing a process relating to the color calibration of fluorescent ink, comprising: printing means for printing a patch chart for estimating the amount of fluorescent ink ejected on paper containing a fluorescent whitening agent; a white light source emitting UV light; a sensor unit equipped with 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 for correcting the amount of fluorescent ink impregnated based on the measurement results from the sensor unit, wherein the 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 apparatus according to Configuration 1, characterized in that the emission wavelength of the fluorescent whitening agent is the excitation wavelength of the fluorescent ink.

[0122] (Configuration 3) The printing apparatus according to Configuration 1 or 2, characterized in that the non-fluorescent ink absorbs at least one of the light in the excitation wavelength range of the fluorescent whitening agent and the light in the emission wavelength range of the fluorescent whitening agent.

[0123] (Configuration 4) The printing apparatus according to any one of Configurations 1 to 3, characterized in that the dots of the non-fluorescent ink have a thickness and colorant density that can absorb light in the excitation wavelength range of the fluorescent whitening agent and light in the emission wavelength range of the fluorescent whitening agent.

[0124] (Configuration 5) The printing apparatus according to any one of Configurations 1 to 4, characterized in that the light-receiving element receives light that includes at least a portion of the excitation wavelength range and emission wavelength range of the fluorescent ink.

[0125] (Configuration 6) The printing apparatus according to any one of Configurations 1 to 5, characterized in that the sensor unit further comprises a filter provided in front of the light receiving element.

[0126] (Configuration 7) The printing apparatus according to any one of Configurations 1 to 6, characterized in that the filter cuts out light other than the excitation wavelength range of the fluorescent ink.

[0127] (Configuration 8) The printing apparatus according to Configuration 7, characterized in that 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 apparatus according to any one of Configurations 1 to 6, characterized in that the filter cuts out light outside the emission wavelength range of the fluorescent ink.

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

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

[0131] (Configuration 12) A printing apparatus according to 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 apparatus according to any one of Configurations 1 to 12, characterized in that the dots of the non-fluorescent ink cover at least a portion of the dots of the fluorescent ink below the dots.

[0133] (Configuration 14) A printing apparatus according to 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 lower surface of the non-fluorescent ink dot covers the entire upper surface of the fluorescent ink dot below the dot.

[0134] (Configuration 15) A printing apparatus according to any one of Configurations 1 to 12, characterized in that the diameter of the dots of the non-fluorescent ink is larger than the diameter of the dots of the fluorescent ink, and the dots of the non-fluorescent ink cover the upper surface and side surface of the dots of the fluorescent ink formed below the dots.

[0135] (Configuration 16) A printing apparatus according to 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 pre-printed on the fluorescent ink.

[0136] (Configuration 17) The printing apparatus according to Configuration 16, characterized in that the dots of fluorescent ink cover at least a portion of the dots of non-fluorescent ink located below the dots.

[0137] (Configuration 18) The printing apparatus according to 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 lower surface of the fluorescent ink dot covers the entire upper surface of the non-fluorescent ink dot below the dot.

[0138] (Configuration 19) The printing apparatus according to Configuration 16, characterized in that the diameter of the dots of the non-fluorescent ink is larger than the diameter of the dots of the fluorescent ink, and the upper surface of the dots of the non-fluorescent ink covers the entire lower surface of the dots of the fluorescent ink formed on top of the dots.

[0139] (Method 1) A method for color calibration performed in a printing apparatus, comprising the steps of: printing a patch chart for estimating the ejection amount of fluorescent ink on paper containing a fluorescent whitening agent using 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 paper on which the patch chart is printed using a light-receiving element provided in a sensor unit; and correcting the amount of fluorescent ink impregnated based on the measurement result from the sensor unit, wherein the 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.

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

[0141] In the embodiment described above, the reflection coefficient was used to explain the sensor's measured values, but density or color values ​​calculated from the reflection coefficient (for example, CIE L*a*b*, tristimulus values ​​XYZ, etc.) may also be used.

[0142] In the embodiments described above, grayscale patches were described as a patch chart for calibration, but a correction table may also be generated by estimating a specific grayscale output amount.

[0143] In the above-described embodiment, a photodiode was explained as the light-receiving element of the color sensor, but a configuration such as a phototransistor may also be used.

[0144] In the embodiment described above, a configuration was described in which the color sensor is mounted on the side of the carriage, but the color sensor may be mounted in other locations, or the measurement may be performed manually.

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

[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 whitening agent. However, any other color ink may be used as long as it has the property of absorbing light in the excitation wavelength range or the emission wavelength range of the fluorescent whitening agent.

[0147] This disclosure can also be implemented by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be implemented by a circuit (e.g., an ASIC) that implements 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 onto a recording medium containing a fluorescent whitening agent, A white light source that emits UV light, A sensor unit comprising 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 means for correcting the amount of fluorescent ink to be injected based on the measurement results from the sensor unit, It has, The patches included in the patch chart are printed with the fluorescent ink and the non-fluorescent ink, and at least one dot of the non-fluorescent ink overlaps with a dot of the fluorescent ink. The system further includes control means for controlling the order in which the fluorescent ink and the non-fluorescent ink are applied. A printing apparatus characterized by the following features.

2. The emission wavelength of the fluorescent whitening agent becomes the excitation wavelength of the fluorescent ink. The printing apparatus according to feature 1.

3. The non-fluorescent ink absorbs at least one of the light in the excitation wavelength range of the fluorescent whitening agent and the light in the emission wavelength range of the fluorescent whitening agent. The printing apparatus according to feature 2.

4. The dots of the non-fluorescent ink have a thickness and colorant density that can absorb light in the excitation wavelength range of the fluorescent whitening agent and light in the emission wavelength range of the fluorescent whitening agent. The printing apparatus according to feature 3.

5. The light-receiving element receives light that includes at least a portion of the excitation wavelength range and emission wavelength range of the fluorescent ink. The printing apparatus according to feature 3.

6. The sensor unit further includes a filter provided in front of the light-receiving element. The printing apparatus according to feature 5.

7. The filter cuts out light outside the excitation wavelength range of the fluorescent ink. The printing apparatus according to feature 6.

8. The fluorescent ink is a fluorescent pink ink. The aforementioned non-fluorescent ink is yellow ink. The aforementioned filter is a green filter. The printing apparatus according to feature 7.

9. The filter cuts out light outside the emission wavelength range of the fluorescent ink. The printing apparatus according to feature 6.

10. The fluorescent ink is a fluorescent pink ink. The aforementioned non-fluorescent ink is yellow ink. The aforementioned filter is a red filter. The printing apparatus according to feature 9.

11. For all of the dots of the fluorescent ink, each dot overlaps with one dot of the non-fluorescent ink. The non-fluorescent ink is applied to the fluorescent ink afterwards. The printing apparatus according to feature 1.

12. The non-fluorescent ink dots cover at least a portion of the fluorescent ink dots below them. The printing apparatus according to feature 11.

13. The diameter of the fluorescent ink dot and the diameter of the non-fluorescent ink dot below the dot are equal. The lower surface of the non-fluorescent ink dot covers the entire upper surface of the non-fluorescent ink dot below it. The printing apparatus according to feature 11.

14. The diameter of the dots of the non-fluorescent ink is larger than the diameter of the dots of the fluorescent ink. The non-fluorescent ink dots cover the top and side surfaces of the fluorescent ink dots formed beneath them. The printing apparatus according to feature 11.

15. For all of the dots of the fluorescent ink, each dot overlaps with one dot of the non-fluorescent ink. The non-fluorescent ink is pre-applied to the fluorescent ink. The printing apparatus according to feature 1.

16. The dots of the fluorescent ink cover at least a portion of the dots of the non-fluorescent ink below the dots. The printing apparatus according to feature 15.

17. The diameter of the fluorescent ink dot and the diameter of the non-fluorescent ink dot below the dot are equal. The lower surface of the fluorescent ink dot covers the entire upper surface of the non-fluorescent ink dot below it. The printing apparatus according to feature 15.

18. The diameter of the dots of the non-fluorescent ink is larger than the diameter of the dots of the fluorescent ink. The upper surface of the non-fluorescent ink dot covers the entire lower surface of the fluorescent ink dot formed on top of the dot. The printing apparatus according to feature 15.

19. A printing means for printing a patch chart for estimating the amount of fluorescent ink ejected onto a recording medium containing a fluorescent whitening agent, A white light source that emits UV light, A sensor unit comprising 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 means for correcting the amount of fluorescent ink to be injected based on the measurement results from the sensor unit, It has, The patches included in the patch chart are printed with the fluorescent ink and the non-fluorescent ink, and at least one dot of the non-fluorescent ink overlaps with a dot of the fluorescent ink. The non-fluorescent ink absorbs at least one of the light in the excitation wavelength range of the fluorescent whitening agent and the light in the emission wavelength range of the fluorescent whitening agent. The light-receiving element receives light that includes at least a portion of the excitation wavelength range and emission wavelength range of the fluorescent ink. The sensor unit further includes a filter provided in front of the light-receiving element, The filter cuts out light outside the excitation wavelength range of the fluorescent ink. The fluorescent ink is a fluorescent pink ink. The aforementioned non-fluorescent ink is yellow ink. The aforementioned filter is a green filter. A printing apparatus characterized by the following features.

20. A printing means for printing a patch chart for estimating the amount of fluorescent ink ejected onto a recording medium containing a fluorescent whitening agent, A white light source that emits UV light, A sensor unit comprising 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 means for correcting the amount of fluorescent ink to be injected based on the measurement results from the sensor unit, It has, The patches included in the patch chart are printed with the fluorescent ink and the non-fluorescent ink, and at least one dot of the non-fluorescent ink overlaps with a dot of the fluorescent ink. The non-fluorescent ink absorbs at least one of the light in the excitation wavelength range of the fluorescent whitening agent and the light in the emission wavelength range of the fluorescent whitening agent. The light-receiving element receives light that includes at least a portion of the excitation wavelength range and emission wavelength range of the fluorescent ink. The sensor unit further includes a filter provided in front of the light-receiving element, The filter cuts out light outside the emission wavelength range of the fluorescent ink. The fluorescent ink is a fluorescent pink ink. The aforementioned non-fluorescent ink is yellow ink. The aforementioned filter is a red filter. A printing apparatus characterized by the following features.

21. The process involves printing a patch chart for estimating the amount of fluorescent ink ejected onto a recording medium containing a fluorescent whitening agent using a printing method, A step of using a white light source to emit light including UV light, The sensor unit includes a light-receiving element that receives light emitted from the white light source and reflected by the recording medium on which the patch chart is printed, The steps include correcting the amount of fluorescent ink to be injected based on the measurement results from the sensor unit, It has, The patches included in the patch chart are printed with the fluorescent ink and the non-fluorescent ink, and at least one dot of the non-fluorescent ink overlaps with a dot of the fluorescent ink. The method further includes the step of controlling the order in which the fluorescent ink and the non-fluorescent ink are applied. A method characterized by the following:

22. A program for causing a computer to perform the method described in claim 21.

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