CN104316469B - A kind of printing printing spectrum color separation method false proof towards metamerism - Google Patents

Abstract

The invention discloses a kind of printing printing spectrum color separation method false proof towards metamerism, it calculates the reasonable selection achieving metamerism anti-counterfeiting detection light source according to Pearson's correlation coefficient；By color science correlation computations formula, in conjunction with printing the high accuracy modeling of printing equipment colour generation characteristic, it is achieved that the accurate preparation of metamerism sample；Utilize multistage screening method, significantly improve efficiency and accuracy prepared by metamerism sample.It is preparing aspect towards the metamerism sample printing printing technology, compares existing method more accuracy, and implements conveniently.After determining metamerism sample preparation procedures by this method, can design in conjunction with all kinds of graphic designs, by printing design and the production of the metamerism anti-fake product of mode of printing realization printing and packaging field.

Description

A kind of printing printing spectrum color separation method false proof towards metamerism

Technical field

The invention belongs to printing packaging field of anti-counterfeit technology, be specifically related to a kind of printing printing false proof towards metamerism Spectrum color separation method.

Background technology

In color science field, metamerism refer to different color sample specific illumination and observe under under the conditions of color Join, but the unmatched phenomenon of color under other illumination and observation condition.From colorimetry angle analysis, the generation of this phenomenon be by The formation mechenism of color tristimulus values is determined.Color tristimulus values refers to that human eye is experienced external optical signals and stimulated produced Color perception, its spectral reflectivity being substantially colour substance regards in the mankind under the influence of lighting condition and human eye perception characteristic A kind of integration response formed in feel maincenter, as shown in formula (1):

$X={\∫}_{380}^{780}\stackrel{\‾}{x}\left(\mathrm{\λ}\right)E\left(\mathrm{\λ}\right)R\left(\mathrm{\λ}\right)d\mathrm{\λ};$

$\begin{array}{c}Y={\∫}_{380}^{780}\stackrel{\‾}{y}\left(\mathrm{\λ}\right)E\left(\mathrm{\λ}\right)R\left(\mathrm{\λ}\right)d\mathrm{\λ};\\ Z={\∫}_{380}^{780}\stackrel{\‾}{z}\left(\mathrm{\λ}\right)E\left(\mathrm{\λ}\right)R\left(\mathrm{\λ}\right)d\mathrm{\λ};\end{array}---\left(1\right)$

WhereinRepresenting human eye vision adaptation function, E (λ) represents lighting source, and R (λ) represents material face The spectral reflectivity information of color, λ represents the visible wavelength in the range of 400nm-700nm.Visible, the essence of color tristimulus values The shape that is color spectrum reflectivity information under the conditions of different light sources with perception spectral sensitivity in human eye or equipment photo-sensitive cell A kind of transition response from higher-dimension to low-dimensional become.It can therefore be concluded that along with light source and the change of observer, different color sample This chrominance information there will be match colors under specified conditions and other unmatched problem of condition color, and this problem is homochromy different Spectrum problem.

Printing packaging industry is the important component part of Chinese national economy, and it is closely bound up with the life of the people masses. The above-mentioned characteristic being had in view of metamerism phenomenon, it has obtained industry in the application of printing packaging anti-counterfeit field at present Extensive concern, its key problem focuses primarily upon the preparation technology aspect of high-quality metamerism sample.Such as, Chinese patent 103018813A describes a kind of metal medium optically variable anti-counterfeiting thin film based on metamerism effect, provides for package anti-counterfeiting field One new means.Chinese patent CN101244679A then passes through by different magnetic inks in INFRARED ABSORPTION and reflection characteristic On difference, achieve metamerism based on special ink in specialty printing field false proof.But above-mentioned applied research is universal Depend on complex material preparation process, therefore its application cost is of a relatively high.2010, Chinese patent CN102342087A Propose a kind of method for the most directly creating metamerism chromatic zones set of blocks, false proof for metamerism The development of technology provides a kind of fast and simple and cost-effective method.But, owing to technique is at metamerism sample Use in preparation method and simply enumerate and the method for successive ignition, therefore it still suffers from the most obvious in terms of method efficiency of the practice Deficiency.

In sum, researching and developing field in current printing packaging anti-counterfeiting technology, prior art is ground in metamerism anti-counterfeiting technology Originating party face still suffers from the problem that method applicability, motility and reasonability cannot be taken into account.

Summary of the invention

It is an object of the invention to provide a kind of printing printing spectrum color separation method false proof towards metamerism, to solve There is the problem that method applicability, motility and reasonability cannot be taken into account in printing packaging anti-counterfeiting technology at present.

It is an object of the invention to be achieved through the following technical solutions.

A kind of printing printing spectrum color separation method false proof towards metamerism, comprises the following steps:

Step 1, carries out typical sample sampling in the system colors space printing print system, it is thus achieved that P typical case's color Sample, and exported by printing print system；

Step 2, the spectral reflectivity information of the typical color sample that measuring process 1 is exported, intercept in visible-range Spectral reflectance data R (R1, R2 ... RP)；

Step 3, utilizes Pearson's correlation coefficient equations any light source relative spectral power distributions dependency, with Pierre Inferior correlation coefficient less than threshold value c for according to determine metamerism detection light source to E1, E2, wherein E1 is corresponding to the light of match colors Source, the light source that E2 does not mates corresponding to color；

Step 4, adopts with the following method, calculation procedure 2 is measured corresponding to gained each sample R (R1, R2 ... RP) each with Color different spectrum collection M (M1, M2 ... MP):

Step 4.1, calculates the color object matches function of match colors light source E1 based on step 3 definition, such as formula (2) Shown in, wherein A represents human eye vision adaptation function,

Ψ=A^TE1 (2)

Step 4.2, calculates the orthogonal project operator of color object matches function, as shown in formula (3),

${\hat{R}}_{E1}=\mathrm{\Ψ}{\left({\mathrm{\Ψ}}^T\mathrm{\Ψ}\right)}^{-1}{\mathrm{\Ψ}}^T---\left(3\right)$

Step 4.3, utilizes formula (4) to solve the metamerism collection M corresponding to arbitrary sample R, and wherein α is variable element, Its span is [s, t], and value is spaced apart w；

$M={\hat{R}}_{E1}R+\mathrm{\α}(I-{\hat{R}}_{E1})R---\left(4\right)$

Step 5, rejects each wave band value in the metamerism collection M corresponding to arbitrary sample R tried to achieve in step 4 and is not belonging to [0,1] the metamerism spectrum of scope (i.e. not meeting reflectance spectrum physical significance)；

Step 6, carries out overall situation sampling printout printing the print system colour space, measures output sample spectrum reflection Rate information also passes through principal component analytical method by its dimensionality reduction to three dimensions, utilizes algorithm of convex hull to quantify this three dimensions Build；

Step 7, utilizes field of Computer Graphics inhull algorithm to judge whether metamerism spectrum is quantified in step 6 Within the colour gamut built, if not in colour gamut, then gained sample set after step 5 is simplified is carried out secondary rejecting, obtain any sample Metamerism collection N (N1, N2 ... NP) corresponding to this R (R1, R2 ... RP)；

Step 8, builds CYNSN model (the Cellular Yule-Nielsen Spectral printing print system Neugebauer Model), it is achieved by printing the mapping to output spectrum space of the printing equipment colour space；

Step 9, realizes the reverse modeling of CYNSN model constructed by step 8 by sequential quadratic programming algorithm, and then to step In rapid 7 metamerism collection N corresponding for gained arbitrary sample R, each spectrum carries out reverse color separation, and prints the output for printing；

Step 10, measures the output spectrum of sample in metamerism collection N corresponding to arbitrary sample R, and fixed in calculation procedure 3 Under the E2 light conditions of justice, CIEDE2000 aberration between each spectrum in arbitrary sample R and metamerism collection N, maximum with aberration Turn to foundation, choose representative metamerism spectrum.

And, the value of threshold value c is 0.60.

And, if the pre-set interval of variable element α is [s, t], pre-set interval lower limit s value is 0, pre-set interval upper limit t Value is 2, presets step-length w=0.02.

The present invention calculates the reasonable selection achieving metamerism anti-counterfeiting detection light source according to Pearson's correlation coefficient；Pass through Color science correlation computations formula, in conjunction with printing the high accuracy modeling of printing equipment colour generation characteristic, it is achieved that metamerism sample Accurately preparation；Utilize multistage screening method, significantly improve efficiency and accuracy prepared by metamerism sample.It is towards beating Aspect prepared by the metamerism sample of print printing technology, compares existing method more accuracy, and implements conveniently.Pass through this method After determining metamerism sample preparation procedures, can design in conjunction with all kinds of graphic designs, by print mode of printing realize printing and The design of the metamerism anti-fake product of packaging field and production.

Accompanying drawing explanation

Fig. 1 is the flow chart of the embodiment of the present invention；

Fig. 2 is the spectral reflectivity curve example of metamerism sample prepared by the present invention.

Detailed description of the invention

In order to make the purpose of the present invention, technical scheme and advantage clearer, below in conjunction with drawings and Examples, right The present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, and It is not used in the restriction present invention.

A kind of false proof towards the metamerism printing printing spectrum color separation method that embodiment provides as shown in Figure 1, the party The metamerism sample that method improves towards printing printing technology in certain amplitude prepares precision and efficiency.

Using CMYK tetra-color ink-jet print system and FANTAC210 gram high smooth printing paper in the present embodiment, wherein CMYK is respectively It is blue or green (Cyan), pinkish red (Magenta), yellow (Yellow), the English abbreviation of black (Black) four kinds of colors.It should be noted that The invention is not limited in four color printers and certain paper type, it is for multi-color printing print system and other types paper Zhang Jiezhi is equally applicable.

The present embodiment specifically includes following steps:

1) in the system colors space printing print system, typical sample sampling is carried out, it is thus achieved that P typical case's color sample, And exported by printing print system.

Wherein sample according to IT8.7/3 standard color card data in CMYK tetra-color ink-jet print system, print defeated altogether Go out to obtain 988 typical color samples.

2) 1 is measured) the spectral reflectivity information of typical color sample that exported, intercept the spectrum in visible-range anti- Penetrate rate data R (R1, R2 ... RP).

Visible-range is generally 400nm 700nm.Embodiment is by 1) the typical color sample that generates, with CMYK tetra-color Ink-jet printer and FANTAC210 gram high smooth printing paper export and use its spectral reflectivity of spectrophotometer measurement, intercept 400nm The spectral reflectance data at 700nm interval.

3) Pearson's correlation coefficient equations any light source relative spectral power distributions dependency is utilized, with Pearson came phase Close coefficient less than threshold value c for according to determine metamerism detection light source to E1, E2, wherein E1 is corresponding to the light source of match colors, The light source that E2 does not mates corresponding to color.

In embodiment, to CIE standard illuminants A, 8 class light source skin between any two such as B, C, D65, D50, F2, F8, F11 You are solved by inferior correlation coefficient, and wherein threshold value c is set as 0.60.In conjunction with practical situation, embodiment is respectively adopted standard and shines Phaneroplasm A and D65 as E1, E2, both it between Pearson came correlation coefficient value be-0.712, there is bigger diversity.

Wherein, Pearson's correlation coefficient is existing statistical method, and it will not go into details for the present invention.

4) adopt with the following method, calculate 2) the middle metamerism collection M measured corresponding to gained each sample R (R1, R2 ... RP) (M1, M2 ... MP):

4.1) calculate based on 3) the color object matches function of match colors light source E1 that defines, as shown in formula (2), its Middle A represents human eye vision adaptation function,

Ψ=A^TE1 (2)

4.2) orthogonal project operator of color object matches function is calculated, as shown in formula (3),

${\hat{R}}_{E1}=\mathrm{\Ψ}{\left({\mathrm{\Ψ}}^T\mathrm{\Ψ}\right)}^{-1}{\mathrm{\Ψ}}^T---\left(3\right)$

4.3) utilizing formula (4) to solve the metamerism collection M corresponding to arbitrary sample R, wherein α is variable element, and it takes Value scope is [s, t], and value is spaced apart w；

$M={\hat{R}}_{E1}R+\mathrm{\α}(I-{\hat{R}}_{E1})R---\left(4\right)$

According to the calculating process described by above-mentioned formula (2) (3) (4), final embodiment is calculated IT8.7/3 standard 988 typical color each self-corresponding metamerism collection of sample defined in colour atla.Wherein, if the preset areas of variable element α Between [s, t] its lower limit s value be 0, upper limit t value is 2, preset step-length w=0.02.Therefore each metamerism is concentrated and is comprised 100 Bar metamerism spectrum.

5) reject 4) in the metamerism collection M corresponding to arbitrary sample R that tries to achieve each wave band value be not belonging to [0,1] model Enclose the metamerism spectrum of (i.e. not meeting reflectance spectrum physical significance)；

In an embodiment, as a example by sample in IT8.7/3 (C, M, Y, K)=(40,10,10,20), its foundation 3) 4) required Obtain 100 spectrum that corresponding metamerism is concentrated, have 28 to there is each wave band value and be not belonging to the situation of [0,1] scope, therefore will This type of metamerism spectrum is rejected, and the rest may be inferred for other sample.

6) carry out overall situation sampling printout in the printing print system colour space, measure and export sample spectrum reflectance letter Cease and pass through principal component analytical method by its dimensionality reduction to three dimensions, utilizing algorithm of convex hull to carry out this three dimensions quantifying structure Build；

In embodiment, the CMYK tetra-each dimension of color print system being carried out 5 grades of uniform samplings, each dimension sampled value is respectively 0, 25,50,75,100, total number of sample points is 5*5*5*5=625.Subsequently, printout, spectral measurement, main constituent are carried out successively Three-dimensional dimensionality reduction and convex closure volume constructed step, wherein principal component analysis and algorithm of convex hull are prior art, and the present invention is the most superfluous State.

7) whether metamerism spectrum is 6 to utilize field of Computer Graphics inhull algorithm to judge) quantified to build Within colour gamut, if not in colour gamut, then to through 5) simplify after gained sample set carry out secondary rejecting, obtain arbitrary sample R (R1, R2 ... RP) corresponding to metamerism collection N (N1, N2 ... NP).With sample in embodiment (C, M, Y, K)=(40,10,10,20) As a example by, after this step spectrum is rejected, it rejects hypercolour territory metamerism spectrum 25, simplifies rear metamerism and concentrates spectrum 47 Bar.

Wherein, inhull algorithm is prior art, can be found in following network address, and it will not go into details for the present invention.http:// www.mathworks.com/matlabcentral/fileexchange/10226-inhull。

8) CYNSN model (the Cellular Yule-Nielsen Spectral of printing print system is built Neugebauer Model), it is achieved by printing the mapping to output spectrum space of the printing equipment colour space；

Embodiment uses 6) described 625 uniform sampling samples structure CMYK tetra-color print system CYNSN model, wherein CYNSN model is prior art, and it will not go into details for the present invention.

9) realize 8 by sequential quadratic programming algorithm) constructed by the reverse modeling of CYNSN model, and then to 7) gained appoints In the metamerism collection N that meaning sample R is corresponding, each spectrum carries out reverse color separation, and prints the output for printing；

Embodiment uses sequential quadratic programming algorithm to 8) in constructed CYNSN model reversely model, i.e. build The vertical mapping being controlled CMYK value by each spectrum in metamerism collection N corresponding for arbitrary sample R to equipment.With sample in embodiment As a example by (C, M, Y, K)=(40,10,10,20), this step is to 7) in calculate 47 metamerism spectrum corresponding devices of gained and control CMYK value solves, and obtains 47 groups of CMYK values, and the rest may be inferred for other sample.

10) measure the output spectrum of sample in metamerism collection N corresponding to arbitrary sample R, and calculate 3) in E2 light source strip Under part, CIEDE2000 aberration between each spectrum in arbitrary sample R and metamerism collection N, turns to foundation with aberration maximum, choosing Take representative metamerism spectrum.

In embodiment, first, turn to foundation with CIEDE2000 aberration maximum, choose 988 typical color samples each same The different spectrum of color concentrates metamerism effect the most significantly metamerism spectrum.Wherein, be shown in Fig. 2 (C, M, Y, K)=(40, 10,10,20) sample and the spectral reflectivity curve of corresponding optimum metamerism sample thereof.Both it, color data is as follows: original Sample:

Equipment controls CMYK value=(40,10,10,20)；

XYZ value=(47.2,46.1,20.3) under A working flare；

XYZ value=(43.2,48.5,62.2) under D65 working flare；

Figure two shows metamerism sample:

CMYK=(32,14,1,26)；

XYZ value=(47.1,46.3,20.4) under A working flare；

XYZ value=(44.9,47.2,63.2) under D65 working flare；

CIEDE2000 aberration under the two A working flare: 0.74

CIEDE2000 aberration under the two D65 working flare: 9.59

Its degree of metameris is obvious as seen from the above.Subsequently, according to same standard, at 988 groups of metamerism spectrum pair Choosing 10 groups of the most significantly metamerism spectrum pair in sample, so far metamerism sample is prepared complete, its corresponding sample and It is finally required that equipment control CMYK value is embodiment.

The foregoing is only presently preferred embodiments of the present invention, not in order to limit the present invention, all essences in the present invention Any amendment, equivalent and the improvement etc. made within god and principle, should be included within the scope of the present invention.

Claims (1)

1. one kind is printed spectrum color separation method towards the printing that metamerism is false proof, it is characterised in that comprise the following steps:

Step 1, carries out typical sample sampling in the system colors space printing print system, it is thus achieved that P typical case's color sample, And exported by printing print system；

Step 2, the spectral reflectivity information of the typical color sample that measuring process 1 is exported, intercept the light in visible-range Spectrum reflectivity data R (R1, R2 ... RP)；

Step 3, utilizes Pearson's correlation coefficient equations any light source relative spectral power distributions dependency, with Pearson came phase Close coefficient less than threshold value c for according to determine metamerism detection light source to E1, E2, wherein E1 is corresponding to the light source of match colors, The light source that E2 does not mates corresponding to color；

Step 4, adopts with the following method, and that measures corresponding to gained each sample R (R1, R2 ... RP) in calculation procedure 2 is each homochromy different Spectrum collection M (M1, M2 ... MP)；

Step 5, reject in step 4 each wave band value in the metamerism collection M corresponding to arbitrary sample R tried to achieve be not belonging to [0, 1] the metamerism spectrum of scope；

Step 6, carries out overall situation sampling printout printing the print system colour space, measures output sample spectrum reflectance letter Cease and pass through principal component analytical method by its dimensionality reduction to three dimensions, utilizing algorithm of convex hull to carry out this three dimensions quantifying structure Build；

Step 7, utilizes field of Computer Graphics inhull algorithm to judge whether metamerism spectrum is quantified to build in step 6 Colour gamut within, if not in colour gamut, then gained sample set after step 5 is simplified is carried out secondary rejecting, obtains arbitrary sample R Metamerism collection N (N1, N2 ... NP) corresponding to (R1, R2 ... RP)；

Step 8, builds the CYNSN model printing print system, it is achieved by printing the printing equipment colour space to output spectrum space Mapping；

Step 9, realizes the reverse modeling of CYNSN model constructed by step 8 by sequential quadratic programming algorithm, and then to step 7 In metamerism collection N corresponding for gained arbitrary sample R, each spectrum carries out reverse color separation, and prints the output for printing；

Step 10, measures the output spectrum of sample in metamerism collection N corresponding to arbitrary sample R, and defined in calculation procedure 3 Under E2 light conditions, CIEDE2000 aberration between each spectrum in arbitrary sample R and metamerism collection N, turns to aberration maximum Foundation, chooses representative metamerism spectrum；

Wherein step 4 specifically includes:

Step 4.1, calculates the color object matches function of match colors light source E1 based on step 3 definition, such as formula (2) institute Showing, wherein A represents human eye vision adaptation function,

Ψ=A^TE1 (2)

Step 4.2, calculates the orthogonal project operator of color object matches function, as shown in formula (3),

${\hat{R}}_{E1}=\mathrm{\Ψ}{\left({\mathrm{\Ψ}}^T\mathrm{\Ψ}\right)}^{-1}{\mathrm{\Ψ}}^T---\left(3\right)$

Step 4.3, utilizes formula (4) to solve the metamerism collection M corresponding to arbitrary sample R, and wherein α is variable element, and it takes Value scope is [s, t], and value is spaced apart w；

$M={\hat{R}}_{E1}R+\mathrm{\α}(I-{\hat{R}}_{E1})R---\left(4\right);$

The value of threshold value c is 0.60；

Pre-set interval lower limit s value is 0, and pre-set interval upper limit t value is 2, value interval w=0.02.