WO2023111192A1 - Dosage d'encre pour impression numérique sur des substrats réfléchissants - Google Patents

Dosage d'encre pour impression numérique sur des substrats réfléchissants Download PDF

Info

Publication number
WO2023111192A1
WO2023111192A1 PCT/EP2022/086181 EP2022086181W WO2023111192A1 WO 2023111192 A1 WO2023111192 A1 WO 2023111192A1 EP 2022086181 W EP2022086181 W EP 2022086181W WO 2023111192 A1 WO2023111192 A1 WO 2023111192A1
Authority
WO
WIPO (PCT)
Prior art keywords
color
ink
target color
opacity
data
Prior art date
Application number
PCT/EP2022/086181
Other languages
English (en)
Inventor
Gerardo CERROS
Original Assignee
Colorportal Europe Sa
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from LU501026A external-priority patent/LU501026B1/en
Priority claimed from US17/553,152 external-priority patent/US11521029B1/en
Application filed by Colorportal Europe Sa filed Critical Colorportal Europe Sa
Priority to CA3241023A priority Critical patent/CA3241023A1/fr
Publication of WO2023111192A1 publication Critical patent/WO2023111192A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/46—Colour picture communication systems
    • H04N1/56—Processing of colour picture signals
    • H04N1/60—Colour correction or control
    • H04N1/603—Colour correction or control controlled by characteristics of the picture signal generator or the picture reproducer
    • H04N1/6033—Colour correction or control controlled by characteristics of the picture signal generator or the picture reproducer using test pattern analysis
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/46—Colour picture communication systems
    • H04N1/54—Conversion of colour picture signals to a plurality of signals some of which represent particular mixed colours, e.g. for textile printing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/46—Colour picture communication systems
    • H04N1/56—Processing of colour picture signals
    • H04N1/60—Colour correction or control
    • H04N1/6097—Colour correction or control depending on the characteristics of the output medium, e.g. glossy paper, matt paper, transparency or fabrics

Definitions

  • the present invention relates to color data processing techniques within colorimetric spaces for dosing ink in printing devices or systems with multiple ink channels when printing on reflective substrates.
  • Digital printers have been rapidly adopted in the field of professional printing, as their ease of configuration through computer terminals and associated programs has substantially decreased the economical threshold for printed volumes, permitting ever more bespoke, ever smaller production runs.
  • Digital printers typically include multiple ink channels, e.g. cyan, magenta, yellow and black (‘CMYK’) or more, e.g. additionally orange, green, violet and red (‘CMYKOGVR’) are regularly combinations with diffusive inks e.g. white, silver or additional inks such as gloss and primer.
  • ink channels e.g. cyan, magenta, yellow and black (‘CMYK’) or more, e.g. additionally orange, green, violet and red (‘CMYKOGVR’
  • diffusive inks e.g. white, silver or additional inks such as gloss and primer.
  • the task of color matching is traditionally carried out by a digital printing operator as an iterative process, attempting to match a printed result with a target color, bridging device-dependent colorimetric space(s) associated with the printer with conversions through a reference device-independent colorimetric space, a preferred example of which is the International Commission on Illumination (‘CIE’) Lightness, green-red and blue-yellow (‘L*a*b’) color space (‘CIELAB’).
  • CIE International Commission on Illumination
  • L*a*b’ Green-red and blue-yellow
  • a fundamental difficulty arises from the specular reflectiveness exhibited by highly-reflective surfaces like metal, wherein light scattering is significant, relative to the diffuse reflection of more traditional printing substrates such as white coated surface, paper or cardboard.
  • Angular light scattering of colors printed on reflective substrates also depends upon the size and shape of color pigments from the formulated ink.
  • Pigments of conventional ink typically used in the analog printing of reflective substrate e.g. aluminum cans, metal sheets
  • inkjet pigments used in digital printers representing significantly more volume in an ink particle.
  • the resulting mix of reflectivity and scattering exhibited in a print layer can then cause some involuntary selectivity in the orientation of the reflections.
  • a printed product on a reflective substrate e.g. flat surface or a cylindrical object
  • conventional ink pigments frequently exhibits dull reflections that causes increased scattering, which translates as a loss of image density, clarity and sharpness.
  • a product digitally printed with toner or smaller inkjet pigments typically with UV or Latex inks applied directly on the reflective substrate or onto a film with a functional inkjet coating layer printed with water-based or eco-solvent inks which can be wrapped or laminated onto the substrate exhibits more vivid reflections, sharpness and color clarity resulting in a different color appearance when compared with a conventional printing process.
  • the ink opacity (or density) is represented by a measurement which defines the amount of light passing through the ink coating applied onto the printed surface.
  • the measure is typically made with either a reflective or a transmission densitometer.
  • other measurable methodologies are disclosed to define the opacity of a given colored ink on a white substrate, these methodologies will not deliver satisfactory results since the RSM substrate reflectance is a key component challenging existing methods. It is believed that no method exists to quantify opacity or transparency of a color on RSM substrates.
  • metal decorating ink manufacturers determine the opacities of their inks at their own appreciation, usually based on the pigment selection to formulate a colored ink with or without a diffusive element such as white ink.
  • inks specially adapted for use in decoration applications represent a further difficulty in color and opacity matching for printing on reflective substrates.
  • Manufacturers formulating inks for reflective substrates have introduced inks with discrete levels of opacity, semi-normalized as opaque, semi-opaque and transparent inks, wherein opaque inks block most of the reflectiveness of the underlying substrate, transparent inks allow the reflectiveness of the underlying substrate to pass substantially through the color, and semiopaque inks provide an intermediate level of opacity.
  • Colors on a diffuse white surface are usually measured with a spectrophotometer under 45/0°or 0/45° geometry, and colors on reflective surfaces are measured with a multi-angle or spherical spectrophotometer under d/8° geometry, wherein the spherical spectrophotometer captures specular reflection in a measurement that either includes the specular component (‘SPIN’) or excludes it (‘SPEX’).
  • SPIN specular component
  • SPEX excludes it
  • a SPIN measurement captures without variation the total reflectance regardless of the surface type (matte, gloss or other) and is said to represent the “true color”, so a target SPIN value should be matched for the printed color to exhibit satisfactory color representation.
  • a SPEX measurement usually excludes the gloss component when capturing the reflectance variation based on differing surfaces, and is said to represent the “sample appearance”, so a SPEX value should be matched for the printed color to exhibit satisfactory color consistency.
  • Measuring a color in SPIN or SPEX delivers distinct and respective values for the color, wherein a difference between the spectral reflectance and with its respective converted L*a*b values for the color vary based on the degree of specular reflectance of the substrate, and wherein the non-linearity of the measurement difference in the spectrum range, can further vary differences in the L*a*b values.
  • colors can be selected from a given printed reference or from printed color books such as a Pantone® guide.
  • the color selection may or may not be represented in very different surface reflection such as white paper, while the desired printed product is going to be printed on a RSM substrate which consequently mislead the choice of colors due to a very different perception when compared with the final printed product on a RSM substrate.
  • PantoneLIVE® provides digital color information from colors available in the Pantone® guides that have been pre-processed onto a variety of printed substrates, including reflective substrates such as metal or aluminum.
  • this digital data available from PantoneLIVE® libraries defined for metal or aluminum do not provide sufficient information to reproduce, with an external conventional or digital system, accurately and simultaneously color with its notion of opacity mainly because opacity in such surface is defined arbitrary by a selective group of people from Pantone® or its preferred ink manufacturer partner Sun Chemical which are not disclosing the information or a given methodology to match color and opacity.
  • color and opacity matching workflows for printing on reflective substrates still correspond broadly to traditional workflows disclosed as prior art in EP20178552.4, wherein operators initialize ink values, print samples, check color accuracy and modify ink values towards matching as required.
  • W02021/035105 of Sun Chemical Corporation discloses an example of such prior art techniques in the specific field of reflective substrate printing.
  • Any color matching workflow begins with an operator obtaining a table of spot colors or target colors to reproduce with a specific printer.
  • Each printer has its own printer calibration, which relies on the device’s ink channels, printing head characteristics and printing substrate with a distinct color profile (e.g. International Color Consortium ‘ICC’ profiles) that contains information to convert a color from the L*a*b color space, or another, to the device color space, wherein L*a*b (or other) values obtained for each color in the table are input to a raster image processor (‘RIP’) computer program.
  • the RIP program processes the target L*a*b values with the printer’s color profile and computes output values for each ink as a color- respective ink dosage, known as an inks separation.
  • a RIP program may propose that the respective ink dosage values for a CMYKOG printer should be [50.196, 100, 100, 50.196, 50.196, 0],
  • the device color space of a printer is defined by inks which it uses, then in the context of reflective substrate printing, this includes opaque, semi-opaque and transparent variants.
  • inks which it uses
  • a major difficulty occurs with artworks which require printing digitally within a same workflow, in which target colors with discrete levels of opacity need to be matched.
  • An operator faces the further difficulty that matching colors in both SPIN and SPEX requires the use of respective color profiles, wherein each printer profile will calculate a distinct and respective inks separation, each different from the other.
  • An improved method of dosing inks in multichannel printers when printing artworks on reflective substrates is therefore desirable, apt to provide inks separations that are a closer match to target colors inclusive of opacity and with reduced user input requirements, relative to techniques of the prior art.
  • the present invention provides a method of dosing ink in multi-channel printers, which automates substantially the adjustment workflow inherent to the task of color matching actual and target colorimetric values when printing on a reflective substrate, wherein the opacity of a target color to be printed digitally or conventionally on the reflective substrate is determined.
  • a computer-implemented method for dosing ink in a printing device with multiple ink channels when printing on a reflective substrate comprising the steps of capturing target color data of at least one target color to be printed on the reflective substrate, wherein the target color data comprises both color data and spectral reflectance data inclusive of specular component included and specular component excluded; generating a printer model ; processing the captured color data with the printer model to output a preliminary dosing ratio for each ink channel, representative of a respective color component of the target color ; computing a curve from each ratio and interpolating same to output a digital opacity value for the respective ink channel ; combining respective digital opacity values of all ink channels to output a digital opacity value for the at least one target color ; computing a natural opacity value from the captured spectral reflectance data ; calculating a difference between the computed digital opacity value and the computed natural opacity value
  • An embodiment of the method may comprise the further step of calibrating the printer with both specular component on a reflective surface and specular component on the reflective surface with a diffuse ink layer.
  • the step of generating a printer model may comprise the further step of generating a printer calibration model based on specular component on a reflective surface and specular component on the reflective surface with a diffuse ink layer.
  • An embodiment of the method may comprise the further step of classifying the or each target color according to the defined target opacity ; and repeating the step of processing with substituting the captured color data for data representative of the or each classified color ; wherein the obtained predicted dosing ratio for each ink channel includes a dosing ratio for a diffuse ink, such as white ink.
  • An embodiment of the method may comprise the further steps of adding the predicted ratio of the diffuse ink from the target natural opacity value to output a next digital opacity value ; and calculating a difference between the natural opacity value and the next digital opacity value ; wherein the calculated difference is a value referred to as delta opacity for the reflective substrate.
  • a variant of any of the preceding embodiments may comprise the further step of correcting the calculated difference before the step of interpolation, wherein the correcting comprises setting the difference to zero, either when the natural opacity value is below a predefined threshold value, or when the calculated difference value is negative.
  • a variant of this further embodiment may comprise the further step of correcting the predicted dosing ratio for each ink channel with a composite function saved as a look-up table.
  • a variant of any of the preceding embodiments may comprise the further steps of generating a color chart from the predicted dosing ratio for each ink channel ; or generating a color chart from the corrected dosing ratio for each ink channel ; and printing the color chart with the printer on a reflective substrate.
  • the substrate may be an object directly printed by a cylindrical printer, or a flat surface, or an optical clear or transparent layer for placing onto the intended reflective substrate.
  • a variant of any of the preceding embodiments may comprise the further steps of determining the opacity of a formulated conventional ink where the colorant or base inks are characterized in order to specify the opacity at each ink step with the aim to match specific opacities of the final conventional ink formula.
  • An embodiment of the method may comprise the further step of computing a diffuse ink percentage from a digital opacity value of the target color to obtain respective versions of digital opacities ranging from transparent to opaque by keeping the chroma and hue (independently from its opacity level) of the target color.
  • a variant may comprise the further step of predefining threshold values which predict opacities for the pastel colors that are generally match to an higher opacity.
  • An embodiment of the method may comprise the further step of outputting predicted dosing ratio for each ink channel respectively for a lighter version and a darker version of the target color at a given a distance in the L*a*b color space, for example a Delta-E measure.
  • An embodiment of the method may comprise the further step of generating a digital ink drawdown or color card representative of a digital color and opacity match for a target color deemed to be best, optionally with lighter and darker versions specified at a predetermined distance Delta-E in the L*a*b color space.
  • a digital printing system comprising a digital printer with multiple ink channels, means for capturing target color data of at least one target color to be printed on a reflective substrate with the printer, and a data processing terminal internal to or operably interfaced with the digital printer, configured by a set of instructions to receive the captured target color data, wherein same comprises both color data and spectral reflectance data inclusive of specular component included and specular component excluded ; generate a printer model ; process the captured color data with the printer model to output a preliminary dosing ratio for each ink channel, representative of a respective color component of the target color ; compute a curve from each ratio and interpolating same to output a digital opacity value for the respective ink channel ; combine respective digital opacity values of all ink channels to output a digital opacity value for the at least one target color ; compute a natural opacity value from the captured spectral reflectance data ; calculate a difference between the computed
  • An embodiment of the system may further comprise a network to which the data processing terminal and a remote terminal are operably interfaced, and wherein the captured target color data is received from the remote terminal.
  • the means for capturing is preferably a spherical or multi-angle spectrophotometer.
  • the reflective substrate may be selected from the group comprising reflective, shiny and/or mirrored (‘RSM’) substrates, including metal such as aluminum, plastic such as film, foil and vinyl, and glass.
  • RSM reflective, shiny and/or mirrored
  • system may further comprise bridging means interfacing the data processing terminal and/or the spectrophotometer with remote storage means, for example a cloud-based data storage node, wherein the color data is optionally encrypted prior to uploading to the remote storage means.
  • remote storage means for example a cloud-based data storage node, wherein the color data is optionally encrypted prior to uploading to the remote storage means.
  • captured target color data may be uploaded from the data processing terminal to, stored in a database at, and processed by a cloud-based data processing node operably configured to translate stored color data according to a color data request of a remote data processing terminal.
  • a method of observing a target color matched and applied to a reflective substrate according to the invention is provided in a light booth, wherein viewing angles are related to the opacity level of a given color.
  • Figure 1 is a logical diagram of a digital printing system in a networked environment, configurable according to the invention, including a local data processing terminal interfaced with a digital multichannel color printer, a remote data processing terminal, and a table of spot colors.
  • Figure 2 is a hardware diagram of a typical hardware architecture of a data processing terminal shown in Figure 1 , including a processor and memory means storing a set of data processing instructions.
  • Figure 3 is a logical diagram illustrating the matching of a target color for printing same on a reflective substrate with the digital printing system of Figures 1 and 2.
  • Figure 4 is a flowchart representation of a prior art method for matching target colors as illustrated in Figure 3.
  • Figure 5 is a flowchart representation of a general method of dosing inks according to the invention, useable to improve the target color-matching method of Figures 3 and 4, including a step of predicting ink separations including a diffusive ink and a step of correcting the predicted ink separations.
  • Figure 6 is a logical diagram of the contents of the memory means of the terminal shown in Figures 1 and 2, including a set of instructions embodying a method as shown in Figure 5.
  • Figure 7 is a flowchart representation of a first embodiment of the step of predicting ink separations in Figure 5.
  • Figure 8 is a flowchart representation of a second embodiment of the step of predicting ink separations in Figure 5, wherein a target color is matched from transparent, to semi-opaque to opaque.
  • Figure 9 is a flowchart representation of an embodiment of the step of correcting the predicted ink separations in Figures 5, 7 and (or) 8.
  • Figure 10 is a flowchart representation of a method of automatically computing a lighter and a darker version of the target color inks separation output by the methods described herein.
  • Figure 11 illustrates a viewing booth at which a user may perform a visual check of one or more target color(s) printed according the methods described herein.
  • the digital printing system 100 includes a data processing terminal 110 locally interfaced, through one or more high-bandwidth data connections 112, with a digital multichannel color printer 114, in the example an inkjet printer with eight color channels 1161-8 comprising cyan (c), magenta (m), yellow (y), black (k), orange (o), green (g), violet (v), and white (w) as a diffuse ink (‘CMYKOGV+W’), and a spectrophotometer 117.
  • CMYKOGV+W a diffuse ink
  • the digital printing system 100 is located within a networked environment, wherein the data processing terminal 110 is a personal computer device which uploads and downloads data encoded as digital signals over high-bandwidth wired or wireless data connections 112, wherein such signals are relayed respectively to or from the computer 110 by a local router device 118 implementing a wired local network operating according to the IEEE 802.3-2008 Gigabit Ethernet transmission protocol and/or a high- bandwidth wireless local network operating according to the IEEE 802.11 Wi-Fi wireless transmission protocol.
  • a local router device 118 implementing a wired local network operating according to the IEEE 802.3-2008 Gigabit Ethernet transmission protocol and/or a high- bandwidth wireless local network operating according to the IEEE 802.11 Wi-Fi wireless transmission protocol.
  • the computer is configured with a data processing unit 201 , data outputting means such as video display unit (VDU) 202, data inputting means such as HID devices, commonly a keyboard 203 and a pointing device (mouse) 204, as well as the VDU 202 itself if it is a touch screen display, and data inputting/outputting means such as the wired or wireless network connection 112 to local and wide area networks via the router 118, a magnetic data-carrying medium reader/writer 206 and an optical data-carrying medium reader/writer 207.
  • VDU video display unit
  • HID devices commonly a keyboard 203 and a pointing device (mouse) 204
  • HID devices commonly a keyboard 203 and a pointing device (mouse) 204
  • the VDU 202 itself if it is a touch screen display
  • a central processing unit (CPU) 208 provides task coordination and data processing functionality. Sets of instructions and data for the CPU 208 are stored in memory means 209 and a hard disk storage unit 210 facilitates non-volatile storage of the instructions and the data.
  • a wireless network interface card (NIC) 211 provides the interface to the network connection 112 with the router 118.
  • One or more universal serial bus (USB) input/output interfaces 212 facilitate connection to the keyboard and pointing devices 203, 204.
  • USB universal serial bus
  • data communications between the computer 110, the printer 114 and the spectrophotometer 117 may be routed through the router device 118, or through wired connections to the computer’s USB interfaces 212, or a combination thereof.
  • All of the above components are connected to a data input/output bus 213, to which the magnetic data-carrying medium reader/writer 206 and optical data-carrying medium reader/writer 207 are also connected.
  • a video adapter 214 receives CPU instructions over the bus 213 for outputting processed video data to VDU 202. All the components of data processing unit 201 are powered by a power supply unit 215, which receives electrical power from a local mains power source and transforms same according to component ratings and requirements.
  • the router 118 is itself connected to a wide area network, an example of which is the Internet 120, via a conventional ADSL or optical fiber connection and through which digital data may be uploaded to and downloaded from remote data processing terminals.
  • Network connectivity and interoperable networking protocols of each data processing terminal allow the terminals to connect to one another and communicate data to and receive data from one another according to certain embodiments the methodology described herein.
  • Remote data processing terminals may be desktop computers as described with reference to Figure 2, or portable variants like laptop and tablet computers.
  • Remote data processing terminals may also include personal communication devices 130, e.g. smartphones, which broadcast and receive data, including voice and/or alphanumerical data, encoded as a digital signal over a wireless data transmission 132, wherein the signal is relayed respectively to or from each device 130 by the geographically-closest communication link relay 134 of a plurality thereof.
  • the plurality of communication link relays 134I-N allows digital signals to be routed between mobile devices 130I-N and their counterpart by means of a remote gateway 136.
  • Gateway 136 is for instance a communication network switch, which couples digital signal traffic between wireless telecommunication networks, such as the network within which wireless data transmissions 132 take place, and the WAN 120.
  • the digital printing system 100 outputs printed products 140 having a reflective substrate, a well- known example of which is drinks cans made of aluminum, wherein the accuracy of color reproduction by the printer 114 in output printed products 140 is paramount. Accordingly a table 150 of spot or target colors is provided to help calibrate color reproduction by the printer 114 with the data processing terminal 110, through the process known in the art as color matching.
  • a forward printer model is defined at the operator terminal 110 based on specular component, which may consist of the forward transformation function defined by the printer’s ICC profile.
  • At step 403, at least a first target color 300 is defined in a color library, for example the table 150 of spot or target colors for an artwork printing job, which requires matching in the digital printing system for color accuracy and color opacity, i.e. representative of the targeted printed color 300.
  • the capturing of target color data is accomplished by measuring the L*a*b values 310 of the target color in the table 150 with the spectrophotometer 117, including in SPIN or SPEX, and saving the measurements as respective sets of values at the terminal 110.
  • Each target color 300 is made up of several colors, each corresponding to an ink respectively available from an ink channel 116i-s of the printer 114.
  • the conventional printer model provides a set of ink channel-respective dosing ratios 330, for instance expressed as a percentage for each ink relative to the combination of all inks for the target color, which is known in the art as color separation data.
  • a color chart is generated with the output ink separation(s) at step 407, wherein color separations 330 are inclusive of opacity, then processed by the forward printer model and printed as a color chart 150 with the printer 114 at step 408.
  • the printed color chart is then measured with the spectrophotometer 117, including in SPIN or SPEX, at step 409 and, subject to the scale of the difference observed relative to the values previously measured for the target color at step 403, the color values of step 406 are typically corrected at step 410.
  • Such a correction may be applied with a correction algorithm for the ink color separation according to tolerance definition, for instance with the ink dosage correcting techniques taught in EP20178552.4.
  • the iteration of the printed color chart deemed to best match the target color(s) is then exported as a digital library of ink color separations 330 at step 411.
  • the exported digital library may then be used in the digital printing system 100 with a RIP application to print the artwork with the matched colors.
  • diffuse ink components of a color for example white, silver, gloss, a primer or another (wherein white (w) is used throughout the present description to avoid unnecessary complexity, but may be substited for any other diffuse ink), can be used to compensate the difference between the natural opacity and the digital opacity of a target color 300, for ouputting a more accurate initial set of ink separation(s) 330i, i.e. corresponding more closely to the separations required to match the target color 300 and its opacity relative to the prior art.
  • white (w) is used throughout the present description to avoid unnecessary complexity, but may be substited for any other diffuse ink
  • the inventor has devised a technique which defines the opacity of a target color when printed conventionally or digitally on a reflective substrate, based on a measurement with a spherical or multiangle spectrophotometer 117, wherein the spectral reflectance with the specular inclusion and the specular exclusion (or a combination of different measuring angles) define a target opacity value, for example by subtracting a value representative of the specular component excluded of the target given color data from a value representative of the specular component included of the target given color data.
  • the technique provides a way of matching the natural opacity of a target color to its associated digital opacity via the addition of a predetermined number of diffuse inks, for example white, silver, gloss, a primer, or another.
  • the printer 114 is initially characterized again at step 401. Color undergoes linearization at step 401 A and, in the method of the invention, the printer undergoes calibration with both specular component and specular on a diffuse ink layer applied to the substrate at step 501 , in the example white ink, before the diffuse ink undergoes linearization at step 401 B.
  • a forward printer model is again defined at the operator terminal 110 based on specular components.
  • a further forward printer model is also defined based on specular component on the diffuse white layer applied to the substrate, and the two forward printer models are combined at step 503, resulting in a single forward model combining the SPIN and SPEX spectral reflectance of each color.
  • the capturing of target color data is again accomplished by measuring the target color 150 with the spectrophotometer 117, including in SPIN and SPEX, and inputting the measurements as respective sets of values at the terminal 110.
  • the target opacity is also defined at step 504, wherein the SPEX value is effectively subtracted from the SPIN value to define the degree of opacity therebetween, as a percentage.
  • the classified color(s) is/are processed with a color prediction algorithm to output respective ink separation(s) at step 406, for instance with the ink dosage techniques taught in EP20178552.4.
  • the or each classified color is further processed with an opacity prediction algorithm, to output respective ink separation(s) including a diffuse ink.
  • the opacity prediction algorithm relies upon the natural opacity and the digital opacity values of a target color.
  • the opacity of each target color is calculated using interpolation on the respective digital opacity curve of each component ink in the separation(s) of step 406, then adding up the digital opacities of all component inks.
  • the natural opacity of each target color is computed from the SPIN/SPEX spectral reflectance data obtained at step 403.
  • the opacity prediction algorithm computes the difference between the natural opacity value and the digital opacity value for the target color and interpolates it against the diffuse ink-step, to output a prediction for the diffuse ink (e.g. white) ratio, conferring the target color its target opacity when printed.
  • a color chart is then generated with the output ink separation(s) at step 407, which combines the color separation prediction of step 406 and the color opacity prediction of step 505.
  • the generated color chart is processed by the forward printer model and printed with the printer 114 at step 408 on a test substrate, which may be the reflective substrate of the intended application or, alternatively, an optical clear or transparent substrate which can be superimposed onto the reflective substrate of the intended application.
  • the printed color chart is then measured with the spectrophotometer 117, including in SPIN and SPEX, at step 410 and color values are optionally corrected, subject to the difference observed relative to the sets of values saved for the target color.
  • color values are further corrected at step 506, subject the difference observed relative to the sets of values saved for the target opacity, with an opacity correction algorithm further described with reference to Figure 9.
  • the opacity correction algorithm relies upon a plurality of interpolations of the curves computed by the opacity prediction algorithm.
  • the iteration of the printed color chart deemed to best match the target color(s) is then exported as a digital library of ink color separations with diffuse ink at step 411 , wherein the exported digital library generated with the method of the invention may then be used in the digital printing system 100 with a RIP application to print the artwork onto the reflective subtrate with the matched colors.
  • inks in the printer 114 of the example include cyan (c), magenta (m), yellow (y), black (k), orange (o), green (g), violet (v) and white (w), and the color inks 'c-m-y- k-o-g-V are collectively denoted by u ; the ink-step is denoted by a , varying from 0 to 1; the color wavelength is denoted by 2 , expressing a value in nanometers (nm) in the range for example from 400 Umin) to 700 (A max ).
  • SPEX can be represented respectively as:
  • the natural opacity of a target color is computed from its SPIN/SPEX spectral reflectance data, wherein the areas under the SPIN and SPEX curves for the color inks are respectively given by:
  • the areas are calculated numerically by the mid-point rule and the element by element division using Hadamard product, but alternative embodiments consider the use of Simpson’s 1/3 rd , 3/8 th rule for enhanced accuracy.
  • the digital opacity of a target color is computed using interpolation on the respective digital opacity curve of each component ink based on its respective ratio in the target color, then adding up the digital opacities of all component inks.
  • the digital opacities of the color inks from cyan to violet are given by: wherein is the substrate opacity, calculated as the average of the opacities at 0% ink-step of all colors excluding the diffuse ink, e.g. white:
  • the ink opacities are curve-fitted.
  • a composite curve is constructed from a weighted average of 5 th and 6 th order polynomials, Fourier series and sum-of-sines curve fits, wherein each component can be assigned a respective weight.
  • the curve fit equations are a polynomial curve fit (5 th degree) yi , a polynomial curve fit (6 th degree) y2, a sum-of-sines curve fit (3 term) ys and a Fourier series surve fit (3 term) y4, wherein the composite curve constructed from the above equations is given by: wherein w k , are the weights assigned to the individual curve-fits: each ink has a different impact, wherein the fomula reaches for an average between the inks, whereby the best fit is derived from the weighted average of the four.
  • a best fit is obtained by subtracting substrate opacities from the natural opacities of each color, wherein a zero opacity is assigned whenever the calculation outputs a negative value.
  • the spectral reflectance of the color white ‘w’ under specular inclusion SPIN and specular exclusion SPEX where the subscripts a and A represent respectively the ink-step (going from 0 to 1) and the wavelength (typically ranging from 400 to 700 nm) can be represented respectively as:
  • the digital opacity of the diffuse ink is given by subtracting the natural opacity of white ink at 0% ink from the natural opacities, which is equivalent to: (rnax(7i)W — WQ 7 , 0), 1) wherein the minimum function min and the maximum function max are applied to avoid opacities percentages less than 0% and greater than 100%.
  • the target colors (t ( ) are made up of several colors from the color inks /z.
  • the printer model provides the ink percentages of each color ink this is available from the ink separation data. Based on the ink separation, the digital opacity of each target color can be found out using interpolation on the respective digital opacity curve r M (a), and then adding up the digital opacities of all component inks.
  • the SPIN/SPEX spectral reflectance data for each target color is also available, from which the target color natural opacities can be computed.
  • the principle underlying the solution described herein is to use a diffuse or achromatic ink, e.g. white, silver, a primer or another, to compensate for the difference between the natural and digital opacities of the target color.
  • the difference in the opacities is thus interpolated against the diffuse ink-step, to obtain a first prediction for the diffuse ink, e.g. white in the illustrations herein.
  • the areas under the target SPI N/SPEX curves are: [00101]
  • the target color natural opacities are given by :
  • a preliminary correction may be applied to the difference S’ between its calculation and its interpolation, based on an threshold value £ wherein, when the natural opacity co’ is below e, the opacity difference 3‘ is set to to zero, and wherein any negative opacity difference value is also set to zero, thus:
  • the color matching technique of the invention described above is useable in a variety of color matching processes, implementable as respective color data processing algorthims embodied in corresponding sets of instructions processed by the computer 110, for dosing inks across the 8 inks channels 116i-s of the printer 114, and both distributable and scalable across nodes of one or more networks.
  • the contents of the memory means 209 of the computer 110 at runtime, when configured by a set of instructions embodying the color data processing techniques described herein, include an operating system is shown at 601, for instance Windows 11 TM distributed by MicrosoftTM Inc. of Redmond, Washington, USA.
  • the OS 601 includes instructions for governing the basic data processing, interdependence and interoperability of the computer hardware components as described with reference to Figure 2, and communication subroutines 602 to configure the computer 110 for bilateral network communication via the NIC 211 interfaced with the wired connection 112 to the local router 118.
  • the OS 601 also includes input subroutines for reading and processing input data variously consisting of user direct input to human interface devices, namely the keyboard 203 and computer mouse 204.
  • a set of instructions is next shown at 604, which is interfaced with the printer 114 and the spectrophotometer 117 through the OS 601 via one or more Application Programmer Interfaces (API) 605.
  • the set of instructions 604 comprises and coordinates the data processing activity of further functionspecific data processing subroutines embodying the various functions and algorithms described herein, including a user interface 606 updated and output to the display 202 in real-time.
  • the set of instructions 604 further maintains a variety of data sets processed by its subroutines, including : one or more ICC profiles of the printer 114, shown at 607; the printer model based on diffuse ink generated at step 502, shown at 608; L*a*b data 310 for the or each target color 300 saved at step 403; shown at 609; matrix, curve and interpolation data processed at run time, shown at 610; one or more sets of ink separations 330I-N corresponding to respective dosages of ink channels 116i-s generated at steps 505 and 506, shown at 611; and eventually, at least one color library generated at step 411, shown at 612, usable to print the target color 300 on a reflective substrate at the printer 114.
  • Further local data and network data is also shown, which may be stored in the memory means 209 at runtime, and some or all of which may be processed either by the color matching application 604 and sub-routines thereof, or by or for other application(s) being processed in parallel with the color matching application 604 at runtime.
  • Examples of further local data include spooling data for the printer 114, generated in response to a color chart-printing instruction preceding step 408; and/or L*a*b data 310 for the or each target color 300 acquired by the local spectrophotometer 117 and communicated to the terminal 110 via a USB connection to the USB module 212.
  • Examples of network data include L*a*b data 310 for the or each target color 300 received from a remote device 130 over the WAN 120, to which the terminal 110 may respond with one or more set(s) of ink separations 330 computed according to the invention; and/or remote application or OS updating data communicated by a remote server over the WAN 120.
  • the first embodiment shown in Figure 7 is a straightforward implementation of the inventive technique, wherein a color printed on a diffuse substrate is set as the target color, the method determines the amount of diffuse ink (e.g. white) required to match the target color when printed on a RSM substrate as previously explained, and the technique best matches the natural opacity a) 1 of the target color to its digital opacity n 1 (through the addition of a white/diffusive ink), so as to make the printed color as transparent (or opaque) as the target color whereby, once printed on a RSM substrate, the printed color will be perceived to be the same as the target color printed on a white substrate.
  • diffuse ink e.g. white
  • the second embodiment shown in Figure 8 is referred to a transparent - semi-opaque - opaque (‘TSO’) color matching technique, wherein the color printed on a diffuse substrate is again set as the target color, the method again determines the amount of diffuse ink (e.g.
  • TSO transparent - semi-opaque - opaque
  • the present embodiment best matches the natural opacity a) 1 of the target color to its digital opacity n 1 (through the addition of a white/diffusive ink) according to a specified range, so as to make the printed color more or less transparent (or opaque) whereby, once printed on a RSM substrate, the printed color will be perceived to be the same as the target color printed on a white substrate, or more or less transparent (or opaque).
  • the task is not to match the opacity of the printed color to that the target color, but to compute the amount of diffuse ink, e.g. white, required to produce different versions of the target color given a range of natural opacities.
  • This embodiment advantageously allows a designer to assess how transparent or opaque the different versions of a target color appear, when printed on the RSM substrate.
  • the range of natural opacities can be classified as follow: the n v transparent versions of the target color can be represented as values in a transparency range ⁇ 7 ⁇ , T 2 ⁇ ; the n v semi-opaque versions of the target color can be represented as values in a semi-opaque range of ⁇ S 1 ,S 2 ⁇ ; the n v opaque versions of the target color can be represented as values in an opaque range ⁇ O 1; O 2 ).
  • target colors t ( , TSO are represented as n v versions each of transparent, semi-opaque and opaque colors (i.e. a total of 3n v versions from transparent to opaque).
  • the color separation data a ⁇ 1 is then loaded to obtain the target color digital opacities from the curve-fits as previously defined in equation (5).
  • the diffuse ink prediction will have a total of 3n v number of versions of each target color (n v versions for each of the T, S and O). Therefore, the total number of diffuse-ink predictions are N x 3n v .
  • the difference between the natural and digital opacity for the Zcth version of the target color is defined as 8 lik .
  • the Zcth diffuse ink prediction is then calculated as a w L k following equations (6) and (7).
  • Exceptions can be applied for pastel colors, which are generally characterized by a higher natural opacity.
  • Pastel colors can be defined as a family of pale colors with a high luminance value and low saturation.
  • the qualifiers ‘high value’ and ‘low saturation’ are purposely relative terms.
  • a pastel flag Pp is used to classify pastel colors among other colors, wherein TSO are represented as total of n v versions ranging from semi-opaque to opaque, all located in the higher natural opacity or at a threshold value which can be determined.
  • the qualification of a color as pastel or not is based on its spectral reflectance, can be scaled on a Pastel Index P ind ranging from 0 to 1 (or 0% to 100%), under a set of conditions which, in aggregate, build up the degree of confidence of that qualification as a logical output function (true/1 or false/0).
  • the following conditions C n are provided by way of non-limitative example, and are considered apt to provide a reliable Pastel Index.
  • a condition n r can relate to the spectrum reflectance of the color.
  • One condition may be to have the color spectrum close to a reference high lightness spectrum, between the susbstrate-min and substrate-max spectra as per a number of points n r in the color spectrum ⁇ pl that lie between the corresponding points
  • n 2 can be the number of points in the color spectrum 0 ⁇ that lie above the corresponding points of ⁇ p k . This condition enforces that at least C2 nm % of the color spectrum should lie above the representative light black (or gray) spectrum.
  • a up and A down can represent, respectively, the area between the color spectrum and the white spectrum, and the area between the color spectrum and the light black spectrum. These conditions enforce, respectively, that A up and A down should be at least CTM in and CTM ax units. Furthermore, another condition can be the ratio A up : 4 O wn should be at most CTM ax .
  • a further set of conditions can relate to the color space coordinates (L*a*b*, L*c*h*, L*u*v*, HSL, HSV) .
  • the L* coordinate in CIE-L*a*b color space should be at least CTM in .
  • the L hsl coordinate in HSL color space should be at least CTM m .
  • the V hsv coordinate in HSV color space should be at least CTM 171 .
  • the S hsv coordinate in HSV colors pace should be at most CTM ax .
  • the L lch coordinate in L*c*h* color space should be at least CTM n .
  • the c lch coordinate in Lch color space should be at most CTM ax .
  • the u luv coordinate in Luv color space should be at most CTM ax .
  • the v luv coordinate in Luv color space should be at most CTM ax .
  • a further condition can be based on the CMYKOGV or p color separation. This condition is based on the observation that known pastel colors have a zero (or negligibly low) black ink in the p color separation. Let a k be the black ink % in the p color separation. The condition enforces that a k should be at most C ⁇ ax .
  • the index is 1 or 100%, all conditions are matched. However, a Pastel Index threshold value can be defined by the observer. The conditions do not all have equal importance, wherein different weights w t can be assigned to each condition parity p t , whereby the Pastel Index P ind includes all the constants used in the conditions to determine the pastel-like quality of a color, per- [00129] With reference to Figure 9 now, an embodiment of the correcting step 506 is shown, which outputs corrected ink separations including a diffuse ink component for the or each target color.
  • the predicted diffuse ink ratios are applied for compensating the difference S' between the natural and digital opacities of the target colors, the spectral reflectances in SPIN and SPEX of the resulting colors are measured and color separation values are produced again, with the new SPIN and SPEX measurements providing the basis data for calculating new natural opacity values.
  • step 506 the or each ith target color is corrected on the basis of the procedure outlined in the preceding steps, i.e. wherein the diffuse/white ink percentage (a(v)° necessary to compensate between the natural and the digital opacity of the target color has been calculated.
  • the correction approach is based upon the Euclidean distance between the printed color and the target color in any given color space (CIE-XYZ, L*a*b, xyz or other), as a value indicative of how close a color, printed according to the first predicted diffuse ink component, is to the target color.
  • the International Commission on Illumination commonly referred to as the CIE, has defined a color difference which takes into account the effect of perceptual non-uniformity. This is typically referred to as Delta-E, which represents the difference between the printed color and the target color in the L*a*b* color space.
  • Delta-E represents the difference between the printed color and the target color in the L*a*b* color space.
  • the perception of a color is also influenced by its opacity.
  • another helpful measure to assess the color difference is the difference in the natural opacity of the target color and that of the printed color, referred to as Delta opacity (‘Delta-O’) in the present disclosure.
  • Delta opacity ‘Delta-O’
  • stepp 506 in Figure 9 accordingly optimises ink separations inclusive of the diffuse ink prediction 330 output by any of the method shown and describe with reference to Figures 5, 7 or 8.
  • a target color is typically formulated using a range of color base inks.
  • These color base inks are, in a conventional printing system, similar to what p defines for a digital printing system.
  • Color bases represented as p c , are also known as colorants or pigments wherein the subscript ‘c’ represents each colorant’s use in a typical ink base system (for example 25 colorants).
  • the techniques disclosed herein are useable for defining the opacity of p c wherein p may be simply replaced by p c in the present description, which can advantageously enhance conventional ink formulation systems.
  • step 401 A can be used to characterize p c and 401 B can be used to characterize the conventional diffuse inks.
  • the natural opacities of p c can be curve fit as per equation (1), the resulting digital opacity curve as per equation (2), and diffuse ink digital opacity as per equation (3).
  • Equations (4) and (5) can be used to assess further corrections or selection of different recipe based on a measured Delta-E and Delta-0 differences.
  • an operator running a conventional printing press may require a physical representation 1000 of the target color, which defines the production tolerances of the printing assignment.
  • the target color is typically a sample of the ink formula, also known as ink drawdown 1010, applied directly onto the printed substrate 1000.
  • the target ink drawdown 1010 is frequently accompanied by darker 1020 and lighter 1030 versions, which correspond respectively to thinner and heavier weights of ink film of the target color, applied with the same ink formula onto the same substrate 1000.
  • the embodiment of the color matching method shown in Figure 10 automatically computes, from the best match output at step 506, lighter and darker representations of a target color at a specific distance AE in the L*a*b color space.
  • the L*a*b values of a target color and the substrate are known, along with the spectral reflectance, ideally with the black spectral reflectance printed onto the same substrate on which the target color is measured.
  • the lighter color (of a higher luminance in coordinate L) is typically characterized by a spectral curve that lies above (at a positive offset from) the spectral curve of the target color.
  • the darker color (with a lower luminance in coordinate L) typically lies below (at a negative offset from) the target color spectral reflectance curve.
  • the processing loop can be terminated when the difference between the target (desired) AE and the theoretical AE is within the specified tolerance.
  • the ink separation of the computed lighter color is most likely to be different from the target color. Therefore, the opacity of the lighter color usually requires a correction following equations (6) and (7).
  • a darker color 1020 may be obtained by following the same methodology, but applying negative offset increments instead.
  • the theoretical L*a*b values of a target color are expectedly different from those of the target color printed on a substrate, due to varying printing conditions such as inks, printing speed, room humidity and temperature, tolerances of measuring device, etc.
  • the target L*a*b coordinates are converted to the corresponding p-ink color separation based on a given printer model as previously described, or another printer calibration profile, wherein the color separation itself is non-unique. Therefore, the theoretical target color and the printed target color expectedly have a non-zero AE therebetween.
  • This AE automatically carries over to the corresponding lighter and darker versions of the theoretical target color.
  • the AE obtained between the printed target and the printed lighter version is usually not exactly the same as the desired AE.
  • the compensation for this deviation requires an iterative corrective procedure, provided with the present embodiment.
  • the D50 illuminant is used for the illuminant spectral power distribution S(A).
  • the CIE-1931 standard observer is used for the observer color matching functions %i(A),yi(A), Zj(A), with a conversion to the CIE-L * a * b coordinates from the XYZ tristimulus values.
  • the lighter darker color spectral reflectance can be denoted respectively as:
  • the library function Delta-E 2000 is used to compute the color difference between the target and the light/dark shades.
  • the Target Vs. Light/Dark Color Difference are denoted as:
  • Figure 11 illustrates an example of a color observation station 1100 for observing a printed color or color-printed object (flat, cylindrical or a shape) 1110 under normalized direct or indirect light 1120 within a light booth 1130.
  • the light booth is typically composed of shielding walls 1140 to prevent light contamination of the normalized light 1120 with other adjacent light sources such as office lamps, windows and the like.
  • a color or object placeholder 1150 locatable within the light booth underneath the normalized light 1120 is configured with a support plane 1152 having a top face facing the light source 1120, wherein the support plane is rotatable with a manual or automated crank member 1154 for facilitating observation of the color under different viewing angles, specular or non-specular.
  • the observation station 1100 is preferably configured to correlate the opacity of a color matched according to the invention (e.g a) 1 or, n 1 ) with the viewing angle 9 under normalized light conditions (e.g. D50 or D65), wherein 9 is the positive angle of the placeholder support plane 1152 measured from the light booth axial plane which is, ideally, perpendicular to the light direction 1122 of the light source 1120.
  • 9 is the positive angle of the placeholder support plane 1152 measured from the light booth axial plane which is, ideally, perpendicular to the light direction 1122 of the light source 1120.
  • the same values are preferably used to define the range of 9, wherein the range starts at substantially 9 min as for example 15° for a viewing condition suited to transparent colors evaluated in specular viewing conditions, contrarily to opaque colors observable in a diffuse light condition of 9 max of substantially 90° for example, 0° providing similar viewing conditions to 90°.
  • the color to evaluate is visually assessed on the top face at its transparency-respective viewing angle, wherein the support plane 1152 can then be rotated to evaluate each successive color of the sample.
  • the range of opacities for a color can be classified according to the output of the transparent-semiopaque-opaque embodiments, simplifying the color assessment procedure within the range.
  • transparent colors can have an opacity range from ⁇ T 1; T 2 ⁇ , semi-opaque from ⁇ S x , S 2 ⁇ and opaque colors from ⁇ O 1; O 2 ⁇ which belong to the 9 min - 9 max range.
  • the present invention thus provides computer-implemented methods for dosing ink in a digital multichannel printer in a single workflow when printing on a reflective substrate, embodiments of which further provide for easily correcting and adjusting values representative of the initially computed diffuse ink dosage.
  • the present disclosure advantageously simplifies and accelerates the color matching process for professional users, with a first set of ink separations 330 inclusive of a diffusive effect, that is demonstrably much closer a match for the target color 300, relative to techniques of the prior art.
  • the benefits of these techniques extend to optical checking by the professional user: the color chart printed with the first set of ink separations 330 computed according to the invention, and/or with a subsequent set of ink separations corrected according to the invention, can be printed on an optical clear or transparent layer substrate, which the user can superimpose onto a printable blank of the reflective substrate, for assessment, for instance in the viewing booth 1100.
  • the transparent layer can be considered to be part of the diffusing elements to a greater or lesser degree based on the total amount of ink deposited in the printing process. Additionally, the ink deposited on the transparent layer can be applied front or reverse to the substrate enabling a differential gloss effect typical from the transparent layer.
  • Such machine-learning techniques can be developed from a corpus of data collected over time, that is representative of color and opacity deviation in printing systems. Such data can be based on variables, such as varitations in the ink or the substrate from one production batch to another, variations in the calibration of a spectrophotometer, the wear of digital printing system parts such as the printing head and more, which are all known to affect the consistency of a final printed color between batches over time
  • achromatic inks in a printing system frequently introduces larger and heavier particles, relative to pigment particles of other chromatic inks: white ink uses titanium dioxide particles which are difficult to maintain in suspension in the ink formula vehicle, eventually causing ink density loss and/or print heads to clog, wherein suuch achromatic inks require permanent or semi-permanent agitation.

Landscapes

  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Textile Engineering (AREA)
  • Spectrometry And Color Measurement (AREA)

Abstract

L'invention concerne un procédé mis en œuvre par ordinateur pour doser de l'encre dans un dispositif d'impression numérique avec de multiples canaux d'encre, lors de l'impression sur un substrat réfléchissant. Un système d'impression numérique est configuré avec le procédé. Des données de couleur cible d'une couleur cible à imprimer sur le substrat réfléchissant sont capturées, comprenant à la fois des données de couleur et des données de réflectance spectrale. Les données de couleur capturées sont traitées avec un modèle d'imprimante pour délivrer un rapport de dosage préliminaire pour chaque canal d'encre. Une valeur d'opacité numérique pour la couleur cible est calculée à partir du rapport de dosage de chaque canal d'encre. Une valeur d'opacité naturelle pour la couleur cible est calculée à partir des données de réflectance spectrale capturées, et une différence entre les valeurs d'opacité numérique et naturelle est calculée. Un rapport de dosage prédit pour chaque canal d'encre est obtenu par interpolation de la différence par rapport à une étape d'encrage d'un composant d'encre diffus de la couleur cible.
PCT/EP2022/086181 2021-12-16 2022-12-15 Dosage d'encre pour impression numérique sur des substrats réfléchissants WO2023111192A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA3241023A CA3241023A1 (fr) 2021-12-16 2022-12-15 Dosage d'encre pour impression numerique sur des substrats reflechissants

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
LULU501026 2021-12-16
LU501026A LU501026B1 (en) 2021-12-16 2021-12-16 Dosing ink for digital printing on reflective substrates
US17/553,152 US11521029B1 (en) 2021-12-16 2021-12-16 Dosing ink for digital printing on reflective substrates
US17/553,152 2021-12-16

Publications (1)

Publication Number Publication Date
WO2023111192A1 true WO2023111192A1 (fr) 2023-06-22

Family

ID=84888744

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2022/086181 WO2023111192A1 (fr) 2021-12-16 2022-12-15 Dosage d'encre pour impression numérique sur des substrats réfléchissants

Country Status (2)

Country Link
CA (1) CA3241023A1 (fr)
WO (1) WO2023111192A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120033263A1 (en) * 2008-09-04 2012-02-09 Sun Chemical Corporation Halftone Printing of Metal-Pigmented Inks to Produce Various Metallic Appearances
US20140350895A1 (en) * 2011-11-28 2014-11-27 Axalta Coating Systems Ip Co., Llc Colour recipe calculating method for matt colour standards
US20200384786A1 (en) * 2019-06-06 2020-12-10 Cma Imaging Europe Sa System and method for dosing ink in digital multichannel printers
WO2021035105A1 (fr) 2019-08-21 2021-02-25 Sun Chemical Corporation Procédé d'épreuvage numérique déco-métallique

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120033263A1 (en) * 2008-09-04 2012-02-09 Sun Chemical Corporation Halftone Printing of Metal-Pigmented Inks to Produce Various Metallic Appearances
US20140350895A1 (en) * 2011-11-28 2014-11-27 Axalta Coating Systems Ip Co., Llc Colour recipe calculating method for matt colour standards
US20200384786A1 (en) * 2019-06-06 2020-12-10 Cma Imaging Europe Sa System and method for dosing ink in digital multichannel printers
WO2021035105A1 (fr) 2019-08-21 2021-02-25 Sun Chemical Corporation Procédé d'épreuvage numérique déco-métallique

Also Published As

Publication number Publication date
CA3241023A1 (fr) 2023-06-22

Similar Documents

Publication Publication Date Title
US9626607B2 (en) Spectral print mapping
EP2717556B1 (fr) Calcul des caractéristiques spectrales de la couleur résultant de la superposition de colorants
CA2754188C (fr) Procede de gestion du metamerisme d'une marchandise coloree
US8274718B2 (en) Method for creating color conversion definition for image output devices and image processing apparatus implementing the method
EP2951983B1 (fr) Séparation de couleurs
EP3127319A1 (fr) Gestion de couleurs
US8456697B2 (en) Adaptive illumination independent matching of spot colors
EP2284511A1 (fr) Systèmes et procédés d'évaluation de la couleur d'impressions revêtues
EP2999206B1 (fr) Procédé et dispositif de prédiction de couleur imprimée, procédé et dispositif de génération de profil
US11521029B1 (en) Dosing ink for digital printing on reflective substrates
LU501026B1 (en) Dosing ink for digital printing on reflective substrates
JP6349741B2 (ja) ルックアップテーブル生成方法、及び、色変換装置
WO2010100129A1 (fr) Procédé et appareil destinés à calculer des couleurs métamères
US6873432B1 (en) Method and apparatus for representing color space transformations with a piecewise homeomorphism
WO2023111192A1 (fr) Dosage d'encre pour impression numérique sur des substrats réfléchissants
US20200404123A1 (en) Updating a lookup table for an imaging system
Deshpande N-colour separation methods for accurate reproduction of spot colours
JP5682759B2 (ja) ブロンジング指標値算出方法、及びブロンジング指標値算出装置
Berns et al. Spectral color reproduction of paintings
Tomić et al. Artificial neural networks for optimising camera‐based colour measurements of prints enhanced with pearlescent pigments
US20230291863A1 (en) Information processing apparatus, information processing system, information processing method, and non-transitory recording medium
US11363169B2 (en) Color adjustment system and method
US11936836B2 (en) Information processing apparatus, system, method, and recording medium for deriving amounts of metallic colorant and process colorants based on priority determined from a target color patch
CN107357538B (zh) 一种获取印刷品的阶调值的方法及装置
JP2022547222A (ja) 着色基材上に印刷するためのカラーマッチング

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 22839675

Country of ref document: EP

Kind code of ref document: A1

ENP Entry into the national phase

Ref document number: 3241023

Country of ref document: CA

REG Reference to national code

Ref country code: BR

Ref legal event code: B01A

Ref document number: 112024012199

Country of ref document: BR