CN103072390B - Method for manufacturing and identifying digital holographic anti-counterfeiting stamp - Google Patents

Abstract

The invention belongs to the technical field of anti-counterfeiting identification of stamps, and particularly relates to a method for manufacturing and identifying a digital holographic anti-counterfeiting stamp. The method comprises two steps of manufacturing the digital holographic anti-counterfeiting stamp and extracting and identifying holographic stamp impression. The stamp is very sensitive to scanning replication and modification of a stamp impression image of the stamp, so that the performance of identifying counterfeit stamps is improved, and the stamp counterfeiting difficulty is improved.

Description

The making of digital hologram security stamp and recognition methods

Technical field

The invention belongs to the anti-counterfeit recognition technical field of seal, particularly a kind of making stamp of digital hologram anti-counterfei waterprint and recognition technology, specifically for the false proof and automatic identification new technology and method of high emulation falsification of seal.

Background technology

Seal is authenticity, the validity of government offices, enterprises and institutions and citizenship papers plaintext book described content or the important means that shows right, falsification of seal tends to bring huge consequence, and the research of quickening making stamp anti-counterfeiting technology and falsification of seal recognition technology two aspects is the keys of dealing with problems.Current conventional making stamp anti-counterfeiting technology comprises the false proof and large class of stamp-pad ink false proof two of impression.The impression anti-counterfeiting technology of having succeeded in developing comprises: the typesetting, the laser engraving system that 1) contain the special character library of seal; 2) containing typesetting, the relief printing plate system processed of distinctive mark; 3) there is the technological means such as typesetting, atom print system of personal characteristics containing irregular dot matrix or the random unreal line of optics etc.Stamp-pad ink is false proof is that detectable substance by comprising in stamp-pad ink is realized.Having developed more successful stamp-pad ink anti-counterfeiting technology comprises: 1) temperature-sensitive anti-counterfeiting technology; 2) visible fluorescence anti-counterfeiting technology; 3) Ultraluminescence anti-counterfeiting technology; 3) infrared anti-false technology etc.

But the technological means of falsification of seal is also improving constantly, traditional-handwork engraving and individual character the falsification of seal gimmick such as are pieced together and are replaced by high-tech means gradually.First the means of high-tech falsification of seal obtain the printed text of true seal by the method that scans or duplicate, then adopt the preparation methods identical with true seal such as laser engraving, photosensitive chapter processed, traditional atom print chapter processed, resin or metallograph chapter processed to make high emulation seal.This high emulation falsification of seal is consistent owing to making the data of seal and the process made from true seal substantially, sometimes can reach the degree of mixing the spurious with the genuine, and checks very difficult.

In order to improve the forgery difficulty of seal, Chinese patent CN1224665 discloses a kind of seal and stamper machine of printing out laser holographic seals vestige.Utilize the base band for laser holographic signet of this technological invention, can on paper, print out laser hologram impression clearly, make seal be difficult for being imitated, palming off texts.

For high emulation falsification of seal, the current method of inspection is very complicated, and common method mainly contains: 1) microscopic examination method of inspection, 2) chemical analysis method; These two kinds of methods are due to complicated operation, consuming time, require degree high to experience, are not therefore all widely used.Within 2007, Chinese patent CN100568264 discloses a kind of seal mirror automatic recognition control method.This invention gathers printed text image by scanner, then extracts the global characteristics such as printed text skeleton, frame with Digital Image Processing, finally by the method for template matches, printed text is carried out to true and false discriminating.Within 2010, Chinese patent CN101894260A discloses a kind of method for identifying forgery seal based on feature line randomly generated by matching feature points.The contour emulation seal reproduction technology but the scanning of the printed text of Faces Modernization and laser carve a seal, existing seal image recognition technology all will be difficult to discern the false from the genuine.

Summary of the invention

Defect and deficiency that the present invention exists in order to solve above-mentioned prior art, provide a kind of scanning to its printed text image to copy and revise very responsive, thereby improve the recognition performance of falsification of seal, increased the making stamp with digital hologram anti-counterfeiting information and the recognition methods of the forgery difficulty of seal simultaneously.

Technical scheme of the present invention: content of the present invention comprises two parts: the making of digital hologram security stamp and the identification of the digital hologram of printed text.

1. a preparation method for digital hologram security stamp, it comprises the steps:

1) designing the binary digital image of a low pixel and make this bianry image is p (x0, y0);

2) with a random-phase marks, bianry image is modulated, the image representation after modulation is

3) image after this Stochastic Modulation is done to the Fresnel Diffraction Transform of d distance, the complex amplitude obtaining after Diffraction Transformation is again

$P(x,y)=\∫\∫p_0(x_0,y_0)\exp \left[\mathrm{jk}\frac{{(x-x_0)}^2+{(y-y_0)}^2}{2d}\right]{\mathrm{dx}}_0{\mathrm{dy}}_0$

Wherein k=2 π/λ;

4) introduce a plane reference light R (x, y), the angle of establishing its direction of propagation and xy plane is (θ, β), and amplitude is unit amplitude, and in xy plane, reference light wave can be expressed as

R (x, y)=exp[j2 π (xcos θ+ucos β)/λ]; This step is convenient to obtain the Fresnel numeral hologram of bianry image;

5) then the diffracted wave P (x, y) of bianry image and reference light wave R (x, y) superposes to interfere also wiping out background DC component to obtain the surface of intensity distribution be H ₀(x, y)=P (x, y) R ^*(x, y)+P ^*(x, y) R (x, y);

6) obtained digital hologram H0 (x, y) is carried out to binary conversion treatment, thereby obtain the digital hologram H (x, y) of binaryzation; This step makes it easy to seal 's production;

7) image is carried out to 0 interpolation, increase the information redundance of image, then it is carried out to image and cut apart, thereby obtain N subhologram, then by certain rule, N subhologram carried out to scramble; This step improves the disguise of binaryzation hologram;

8) finally using the subhologram of these scrambles in seal background texture is embedded in respectively the white space of seal, thereby produce the security stamp with digital hologram anti-counterfeiting information.

Described step 1) in binary digital image be chequered with black and white square chessboard or the circular array of some black.

Described step 2) middle two-dimensional phase determined by Gauss number.

In described step 3) in regressor Frt (p ₀(x ₀, y ₀), d, λ) represent that the Fresnel Diffraction Transform to Stochastic Modulation bianry image p0 (x, y), λ are optical wavelength.

Described step 1) in the pixel of binary digital image be 5X5-20X20.

Described optical wavelength is visible optical wavelength.

Described step 3) in d be 50-500mm, described step 4) direction of propagation of midplane reference light R (x, y) and the angle (θ, β) of xy plane be (0-10 °, 0-10 °).

The recognition methods of a digital hologram security stamp its comprise the steps:

1) obtain true printed text image as with reference to printed text image by imaging device, give eachly with reference to fixing ID of printed text image, build with reference to printed text database;

2) use and step 1) identical method obtains the printed text image of seal to be tested;

3) extract respectively the subhologram picture with reference to printed text and printed text white space to be tested according to the design rule of original seal, and carry out reverse splicing and subtract sampling by scramble rule, thereby obtain complete digital hologram anti-counterfeiting image H (x, y);

4) by step 3) the holographic false proof image obtaining carries out Fresel diffraction the delivery of d distance, that is:

P _r(x ₀,y ₀)＝|Frt(H(x,y),d,λ)|

Thus can reproducing be positioned at the bianry image p (x0, y0) of x0y0 plane, the seal to be tested reproducing and reference seal bianry image be normalized to mean square error (NMSE) and calculate,

$\mathrm{NMSE}=\frac{\underset{i}{\mathrm{\Σ}}\underset{j}{\mathrm{\Σ}}{[p(i,j)-p^{\′}(i,j)]}^2}{\underset{i}{\mathrm{\Σ}}\underset{j}{\mathrm{\Σ}}{\left[p(i,j)\right]}^2}$

In formula, p (i, j), p ' (i, j) are respectively with reference to the digital hologram extracting in printed text and printed text to be tested and reproduce as intensity map;

5) by step 4) normalized mean squared error calculating and certain threshold value of setting compare, if be less than this threshold value, thinks that seal to be tested is true seal, if be greater than threshold value seal to be tested be dummy seal.

Preferably, described step 1) and step 2) in imaging device be the one of camera, scanner or CCD camera.

Preferably, described step 4) in d be 50-500mm.

In order to introduce a plane reference light R (x, y), the angle of establishing its direction of propagation and xy plane is (θ, β), and amplitude is unit amplitude, and in xy plane, reference light wave can be expressed as

R(x,y)＝exp[j2π(xcosθ+ucosβ)/λ]

Then it is H that interference the wiping out background DC component of the diffracted wave P (x, y) of bianry image and reference light wave R (x, y) being superposeed obtains the surface of intensity distribution ₀(x, y)=P (x, y) R ^*(x, y)+P ^*(x, y) R (x, y).

The definition of reproducing picture due to digital hologram is very responsive to the texture variations of interference fringe, and the operation such as scanning and typesetting amendment to true printed text all will cause that the interference grain distribution in printed text changes in seal forgery process, so in forged seal imprint hiding Reconstructed Image Quality in Digital Holography amount the Reconstructed Image Quality in Digital Holography amount than with reference to extracting in printed text is declined a lot, thereby can differentiate easily the true and false of printed text by calculating normalized mean squared error between them.

Brief description of the drawings

Fig. 1 is the making flow chart of digital hologram security stamp in the present invention;

Fig. 2 is binaryzation digital hologram in the present invention;

Fig. 3 is digital hologram security stamp schematic diagram in the present invention;

Fig. 4 is the identification process figure of digital hologram security stamp in the present invention.

Detailed description of the invention

Below in conjunction with the drawings and specific embodiments, the present invention is further detailed explanation, but be not limiting the scope of the invention.

Embodiment 1

The making of the digital hologram security stamp that the present invention proposes and recognition methods comprise the making of digital hologram security stamp and the digital hologram of printed text identification two parts.1, digital hologram security stamp is made: make flow process as shown in Figure 1.First design the bianry image 1 of a 10X10 pixel.It is modulated and obtains modulating complex amplitude Fig. 2 by random phase, then remove to irradiate this modulation image by the planar light that wavelength is 632.8nm, it is carried out to the Fresnel Diffraction Transform of 200mm, and with a deflection be (5o, the plane reference light that 0o) amplitude is 1 and this Fresnel diffraction field are interfered and are obtained interfering hologram 3, the binaryzation digital hologram Fig. 4 that this hologram is carried out LPF and binary conversion treatment and obtained high-contrast, the two-value hologram of example as shown in Figure 2.Again this two-value hologram is cut apart to the scramble white space that texture is embedded in printed text as a setting and formed anti-fake holographic original printed text 5, finally be made into digital hologram security stamp 6 taking this printed text as template by means such as laser engraving or base band mold pressings, its example as shown in Figure 3.

2, digital hologram printed text identification: identifying operation flow process as shown in Figure 4.First obtain true printed text image as with reference to printed text image 1 with the imaging device such as camera, scanner, give eachly with reference to fixing ID of printed text image, build with reference to printed text database.Use the same method and obtain the printed text image (2) of seal to be tested.Extract the subhologram in printed text white space, and carry out Image Mosaics by scramble rule and obtain complete false-proof digital hologram 3, false-proof digital hologram is carried out to the Fresnel Diffraction Transform 4 of distance for 200mm, obtain respectively rebuilding and rebuilding as intensity distribution 6 as intensity distribution 5 and printed text digital hologram to be tested with reference to printed text digital hologram, then calculate the normalized mean squared error 7 between this two width figure, finally result of calculation and threshold value are compared, treat print test chapter and make true and false judgement 8.

Embodiment 2

The making of the digital hologram security stamp that the present invention proposes and recognition methods comprise the making of digital hologram security stamp and the digital hologram of printed text identification two parts.1, digital hologram security stamp is made: make flow process as shown in Figure 1.First design the bianry image 1 of a 20X20 pixel.It is modulated and obtains modulating complex amplitude Fig. 2 by random phase, then remove to irradiate this modulation image by the planar light that wavelength is 777.8nm, it is carried out to the Fresnel Diffraction Transform of 500mm, and with a deflection be (10o, the plane reference light that 0o) amplitude is 1 and this Fresnel diffraction field are interfered and are obtained interfering hologram 3, the binaryzation digital hologram Fig. 4 that this hologram is carried out LPF and binary conversion treatment and obtained high-contrast, the two-value hologram of example as shown in Figure 2.Again this two-value hologram is cut apart to the scramble white space that texture is embedded in printed text as a setting and formed anti-fake holographic original printed text 5, finally be made into digital hologram security stamp 6 taking this printed text as template by means such as laser engraving or base band mold pressings, its example as shown in Figure 3.

2, digital hologram printed text identification: identifying operation flow process as shown in Figure 4.First obtain true printed text image as with reference to printed text image 1 with the imaging device such as camera, scanner, give eachly with reference to fixing ID of printed text image, build with reference to printed text database.Use the same method and obtain the printed text image 2 of seal to be tested.Extract the subhologram in printed text white space, and carry out Image Mosaics by scramble rule and obtain complete false-proof digital hologram 3, false-proof digital hologram is carried out to the Fresnel Diffraction Transform 4 of distance for 500mm, obtain respectively rebuilding and rebuilding as intensity distribution 6 as intensity distribution 5 and printed text digital hologram to be tested with reference to printed text digital hologram, then calculate the normalized mean squared error 7 between this two width figure, finally result of calculation and threshold value are compared, treat print test chapter and make true and false judgement 8.

Embodiment 3

The making of the digital hologram security stamp that the present invention proposes and recognition methods comprise the making of digital hologram security stamp and the digital hologram of printed text identification two parts.1, digital hologram security stamp is made: make flow process as shown in Figure 1.First design the bianry image 1 of a 5X5 pixel.It is modulated and obtains modulating complex amplitude Fig. 2 by random phase, then remove to irradiate this modulation image by the planar light that wavelength is 555.8nm, it is carried out to the Fresnel Diffraction Transform of 50mm, and with a deflection be (0o, the plane reference light that 10o) amplitude is 1 and this Fresnel diffraction field are interfered and are obtained interfering hologram 3, the binaryzation digital hologram Fig. 4 that this hologram is carried out LPF and binary conversion treatment and obtained high-contrast, the two-value hologram of example as shown in Figure 2.Again this two-value hologram is cut apart to the scramble white space that texture is embedded in printed text as a setting and formed anti-fake holographic original printed text 5, finally be made into digital hologram security stamp 6 taking this printed text as template by means such as laser engraving or base band mold pressings, its example as shown in Figure 3.

2, digital hologram printed text identification: identifying operation flow process as shown in Figure 4.First obtain true printed text image as with reference to printed text image 1 with the imaging device such as camera, scanner, give eachly with reference to fixing ID of printed text image, build with reference to printed text database.Use the same method and obtain the printed text image 2 of seal to be tested.Extract the subhologram in printed text white space, and carry out Image Mosaics by scramble rule and obtain complete false-proof digital hologram 3, false-proof digital hologram is carried out to the Fresnel Diffraction Transform 4 of distance for 50mm, obtain respectively rebuilding and rebuilding as intensity distribution 6 as intensity distribution 5 and printed text digital hologram to be tested with reference to printed text digital hologram, then calculate the normalized mean squared error 7 between this two width figure, finally result of calculation and threshold value are compared, treat print test chapter and make true and false judgement 8.

Claims (10)

1. a preparation method for digital hologram security stamp, is characterized in that: it comprises the steps:

1) designing the binary digital image of a low pixel and make this bianry image is p (x ₀, y ₀);

2) with a random-phase marks, bianry image is modulated, the image representation after modulation is

3) image after this Stochastic Modulation is done to the Fresnel Diffraction Transform of d distance, the complex amplitude obtaining after Diffraction Transformation is again

$P(x,y)=\∫\∫p_0(x_0,y_0)\exp \left[\mathrm{jk}\frac{{(x-x_0)}^2+{(y-y_0)}^2}{2d}\right]{\mathrm{dx}}_0{\mathrm{dy}}_0$

Wherein k=2 π/λ;

4) introduce a plane reference light R (x, y), the angle of establishing its direction of propagation and xy plane is (θ, β), and amplitude is unit amplitude, and in xy plane, reference light wave can be expressed as

R(x,y)＝exp[j2π(xcosθ+ucosβ)/λ]；

5) then the diffracted wave P (x, y) of bianry image and reference light wave R (x, y) superposes to interfere also wiping out background DC component to obtain the surface of intensity distribution be H ₀(x, y)=P (x, y) R ^*(x, y)+P ^*(x, y) R (x, y);

6) by obtained digital hologram H ₀(x, y) carries out binary conversion treatment, thereby obtains the digital hologram H (x, y) of binaryzation;

7) image is carried out to 0 interpolation, increase the information redundance of image, then it is carried out to image and cut apart, thereby obtain N subhologram, then by certain rule, N subhologram carried out to scramble;

8) finally using the subhologram of these scrambles in seal background texture is embedded in respectively the white space of seal, thereby produce the security stamp with digital hologram anti-counterfeiting information.

2. the preparation method of a kind of digital hologram security stamp according to claim 1, is characterized in that: described step 1) in binary digital image be chequered with black and white square chessboard or the circular array of some black.

3. the preparation method of a kind of digital hologram security stamp according to claim 1, is characterized in that: described step 2) middle two-dimensional phase determined by Gauss number.

4. the preparation method of a kind of digital hologram security stamp according to claim 1, is characterized in that: in described step 3) in regressor Frt (p ₀(x ₀, y ₀), d, λ) represent Stochastic Modulation bianry image p ₀the Fresnel Diffraction Transform of (x, y), λ is optical wavelength.

5. the preparation method of a kind of digital hologram security stamp according to claim 1, is characterized in that: described step 1) in the pixel of binary digital image be 5X5-20X20.

6. the preparation method of a kind of digital hologram security stamp according to claim 4, is characterized in that: described optical wavelength is visible optical wavelength.

7. the preparation method of a kind of digital hologram security stamp according to claim 1, it is characterized in that: described step 3) in d be 50-500mm, described step 4) midplane reference light R (x, angle (the θ of the direction of propagation y) and xy plane, be β) (0-10 °, 0-10 °).

8. according to a recognition methods for the digital hologram security stamp that in claim 1-7, any described preparation method makes, it is characterized in that: it comprises the steps:

1) obtain true printed text image as with reference to printed text image by imaging device, give eachly with reference to fixing ID of printed text image, build with reference to printed text database;

2) use and step 1) identical method obtains the printed text image of seal to be tested;

3) extract respectively the subhologram picture with reference to printed text and printed text white space to be tested according to the design rule of original seal, and carry out reverse splicing and subtract sampling by scramble rule, thereby obtain complete digital hologram anti-counterfeiting image H (x, y);

4) by step 3) the holographic false proof image obtaining carries out Fresel diffraction the delivery of d distance, that is:

P _r(x ₀,y ₀)＝|Frt(H(x,y),d,λ)|

Can be positioned at x by reproducing thus ₀y ₀bianry image p (the x of plane ₀, y ₀), the seal to be tested reproducing and reference seal bianry image are normalized to mean square error (NMSE) calculating,

$\mathrm{NMSE}=\frac{\underset{i}{\mathrm{\Σ}}\underset{j}{\mathrm{\Σ}}{[p(i,j)-p^{\′}(i,j)]}^2}{\underset{i}{\mathrm{\Σ}}\underset{j}{\mathrm{\Σ}}{\left[p(i,j)\right]}^2}$

In formula, p (i, j), p ' (i, j) are respectively with reference to the digital hologram extracting in printed text and printed text to be tested and reproduce as intensity map;

5) by step 4) normalized mean squared error calculating and certain threshold value of setting compare, if be less than this threshold value, thinks that seal to be tested is true seal, if be greater than threshold value seal to be tested be dummy seal.

9. recognition methods according to claim 8, is characterized in that: described step 1) and step 2) in imaging device be the one of camera, scanner or CCD camera.

10. recognition methods according to claim 8, is characterized in that: described step 4) in d be 50-500mm.