CN102663671B - Digital watermarking embedding and detecting method based on three-step phase shift interferometry - Google Patents

Abstract

The invention provides a digital watermarking embedding and detecting method based on a three-step phase shift interferometry. The method includes a watermarking embedding process and a watermarking detecting and extracting process. The method utilizes a propagation law of a numeric field simulation optical process, so that processes that the watermarking is embedded in a digital image to be protected and the watermarking is detected from an image embedded with the watermarking are achieved, and an encryption and a decryption for information are achieved through a double random phase code and a phase shift interferometry of a Fresnel field. The digital watermarking embedding and detecting method based on the three-step phase shift interferometry has the advantages that a phase shift algorithm is introduced to a digital holography, the disadvantages and the shortages of a coaxial digital holography and an off-axis digital holography are overcome by the phase shift interferometry, and a novel information hiding encryption/decryption method is formed; the decryption can be directly performed without original plain code images in the watermarking detecting process, and the method belongs to a blind watermark algorithm; compared with traditional data encryption processes, the method is highly free and safe; and the method is high in measurement accuracy, easy to operate, rapid in processing speed, high in portability, capable of achieving the overall measurement, and the like.

Description

Digital watermarking embedding and detection method based on three step phase shift interference arts

Technical field

The present invention relates to a kind of digital watermarking embedding and detection method based on three step phase shift interference arts, belong to optoelectronic information safety technique field.

Background technology

Along with multi-disciplinary fast developments such as the communication technology, computer science, cryptography and network technologies, information becomes the grand strategy resource of social development, social informatization has become trend and the core of world today's development, and the research of information security field has been subject to the generally attention of countries in the world.Traditional take the information security technology of cryptography theory as the basis, its protected mode is that encrypted information encryption is become skimble-skamble ciphertext, and the disabled user can not be understood.But along with the quick raising of computer process ability, traditional information security technology is subject to huge challenge.

To begin in recent years a kind of information security technology of starting to walk to develop based on the data encryption technology of optical information processing.Different from traditional information security technology, optical system has inherent parallel processing capability, as the processed and transmission simultaneously of each pixel in a width two dimensional image.And robot calculator is subject to the working method of serial processing, and the same time can only be processed a data.And optical data is processed has more degree of freedom, and same information can be hidden in a plurality of degree of freedom spaces, as phase place, wavelength, volume coordinate, polarization state etc.

Digital Holography is to rely on charge coupled cell (Charge-coupled Device, CCD) to replace holographic dry plate to record interference pattern, shows in real time image change on monitor screen, with the method for digitized form recorded hologram.The recording mode of hologram has two kinds: coaxial recording and from the axle record.The coaxial recording mode can cause reproducing in picture original image, conjugate image and mix mutually with bias light, is difficult to separate.Can effectively realize the separation of twin image from the axle recording mode, but because the resolution of CCD is more much smaller than the resolution of dry plate, cause the angle of reference light and object light can not be too large, thereby limit the application of digital holography.

The phase shift interference art is a kind of interference technique that the object phase information is measured, it makes the phase place on the corrugated (reference light) in two relevant corrugateds do staged or continous way variation, when phase place changes to some eigenwert, interference field is carried out image acquisition, have by calculating these interferogram that different light intensity distributes, can obtain the wavefront information of testee.

Different according to the embedding algorithm position, present digital watermark technology can be divided into Spatial Domain Digital Watermarking technology and Digital Watermarking System in Transform Domain technology.In Spatial Domain Digital Watermarking, the watermark embedding of usually adopting or detection algorithm have least significant bit (LSB) algorithm, Patchwork algorithm, texture block mapping code and text fine setting algorithm etc.In Digital Watermarking System in Transform Domain, the watermark embedding or the detection technique that usually adopt have discrete Fourier transformation, discrete cosine transform, wavelet transform etc.The main deficiency of the digital watermark technology of having reported at present has that robustness is not high enough, the embedding quantity of information of watermark is excessive, the imperceptible of watermark is good not, etc.

At present, the phase shift interference art is combined with Digital Holography and is used for the digital watermarking embedding and detects also not being seen in reported in literature.

Summary of the invention

The present invention is directed to the deficiency that existing digital watermarking embedding and detection method exist, a kind of enciphering/deciphering degree of freedom is large, robustness good, level of security is high digital watermarking embedding and detection method based on three step phase shift interference arts are provided.

Digital watermarking embedding and detection method based on three step phase shift interference arts of the present invention comprise the embedding of watermark and detection and the extraction of watermark, and detailed process is:

(1) telescopiny of watermark:

11. the plane at digital watermarking image O place is called input plane, is close to the back of input plane and places first random phase plate G ₁, with wavelength be the monochromatic plane wave vertical irradiation of λ to input plane, numerical simulation calculation digital watermarking image O and random phase plate G ₁The product of complex amplitude transmitance, then this product being carried out distance parameter is d ₁Fresnel Diffraction Transform, obtain a complex amplitude field U ₂, this complex amplitude field U ₂The plane at place is called changing the plane (distance parameter d ₁Be the distance between input plane and changing the plane);

12. be close to second random phase plate G of changing the plane back placement ₂, numerical simulation calculation U ₂And G ₂The product of complex amplitude transmitance, then this product being carried out distance parameter is d ₂Fresnel Diffraction Transform, obtain a complex amplitude field U, the plane at this U place, complex amplitude field is called records plane (distance parameter d ₂Be changing the plane and record distance between the plane), under recording on the plane the complex amplitude script holder record of carrying digital watermark information.

13. adopt three step phase shift interference arts, by interfering with the reference light of introducing, obtain three width and modulated by phase-plate and contain the interferogram I that hides Info ₁, I ₂And I ₃, the phase place during three interference is respectively 0, pi/2 and π;

14. encrypting rear three width interferogram I ₁, I ₂, I ₃Embed in host image, obtain I ₁', I ₂' and I ₃' as the non-negative image after encrypting, and pass to take over party's (by network or alternate manner) of information, parameter G simultaneously ₂, d ₁, d ₂With optical wavelength λ also together transmission;

(2) detection of watermark and leaching process:

21. recover according to three step phase shift formula the complex amplitude field U that records after encrypt on the plane;

22. making distance is d ₂Contrary fresnel diffraction;

23. the complex amplitude that draws multiply by random phase plate G ₂The complex conjugate of complex amplitude transmitance is carried out another distance and is d ₁Contrary fresnel diffraction;

24. extract real amplitude and the normalization of diffraction complex amplitude field.

Said method can use the Design Mode of Visual C++ and MATLAB hybrid programming to realize on general purpose PC.

The present invention introduces digital hologram with phase shift algorithm, utilizes the phase shift interference art to make up coaxial and shortcoming and defect off-axis digital holography, has formed a kind of new Information hiding method for encryption/decryption; The testing process of watermark does not need former plain code image directly to decipher, and belongs to blind watermarking algorithm; Than the traditional data ciphering process, larger degree of freedom is arranged, level of security is high; Have that measuring accuracy is high, easy operating, processing speed are fast, portable strong, can realize the advantage such as measurement of full field.

Description of drawings

Fig. 1 is the Information hiding enciphering/deciphering principle schematic of the inventive method.

Fig. 2 is the software systems basic structure schematic diagram of realizing the inventive method.

Fig. 3 and Fig. 4 are the software interface figure that realizes the inventive method on general purpose PC.

Fig. 5 is watermarking images.

Fig. 6 is host image.

Fig. 7 is the image after watermarking images is encrypted.

Fig. 8 embeds image after host image with watermarking images.

Fig. 9 is the watermarking images through correct deciphering.

In figure: O is digital watermarking image, and I is input plane, and II is changing the plane, and III is for recording the plane, d ₁Be the distance between input plane and changing the plane, d ₂For changing the plane with record distance between the plane; G ₁And G ₂Be two random phase plate, its complex amplitude transmitance is expressed as respectively exp[i2 π P ₁(x ₁, y ₁)] and exp[i2 π P ₂(x ₂, y ₂)], P wherein ₁And P ₂Two white noises that are randomly dispersed between [0,1].

Embodiment

Fig. 1 has provided the digital watermarking embedding that the present invention is based on three step phase shift interference arts and the Information hiding enciphering/deciphering principle schematic of detection method.In figure, O is watermarking images, I is the input plane plane of place (the digital watermarking image O), II be changing the plane (numerical evaluation for the first time the complex amplitude place after Fresnel diffraction the plane), III is for recording plane (the complex amplitude script holder who carries digital watermark information being recorded the plane of getting off).d ₁Be the distance between input plane and changing the plane, d ₂For changing the plane with record distance between the plane.G ₁, G ₂Be two random phase plate, its complex amplitude transmitance is expressed as respectively exp[i2 π P ₁(x ₁, y ₁)] and exp[i2 π P ₂(x ₁, y ₂)], P wherein ₁And P ₂Two white noises that are randomly dispersed between [0,1].Suppose that in the virtual optics system, related diffraction all satisfies the Fresnel approximation condition.In watermark embed process, with wavelength X, input plane, the changing the plane of virtual light wave and record between the plane apart from d ₁And d ₂, random phase plate the complex amplitude transmitance as watermark keys, thereby design multiple key, improve the security of digital watermarking.

Be the monochromatic plane light wave irradiation input plane of λ when a wavelength, under the condition of Fresnel approximation, the complex amplitude field U of changing the plane ₂Can be expressed as:

$U_2(x_2,y_2)=\frac{\exp \left({\mathrm{ikd}}_1\right)}{\mathrm{i\λ}{d}_1}\∫\∫O(x_1,y_1)\exp \left[i2\mathrm{\π}{P}_1(x_1,y_1)\right]\exp \left\{\frac{\mathrm{\π}}{\mathrm{\λ}{d}_1}\right[{(x_1-x_2)}^2+{(y_1-y_2)}^2\left]\right\}{\mathrm{dx}}_1{\mathrm{dy}}_1,---\left(1\right)$

K=2 π/λ wherein, exp represents the exponential function take e the end of as, i represents imaginary unit, (x ₁, y ₁) and (x ₂, y ₂) represent respectively the corresponding coordinate of input plane and changing the plane; The coordinate on plane is recorded in (x, y) expression hereinafter.For explaining for simplicity, following formula is write as:

$U_2(x_2,y_2)={\mathrm{FrT}}_{d_1}\left\{O(x_1,y_1)\exp \right[i2\mathrm{\π}{P}_1(x_1,y_1)\left]\right\},---\left(2\right)$

Wherein

Expression is to d ₁Fresnel transform.Therefore, the complex amplitude field U that records the plane also can be expressed as

$U(x,y)={\mathrm{FrT}}_{d_2}\left\{U_2(x_2,y_2)\exp \right[i2\mathrm{\π}{P}_2(x_2,y_2)\left]\right\},---\left(3\right)$

By using beam splitter BS, can introduce a phase place is δ _nThe plane reference light wave.Reference light wave and object light ripple are at CCD (camera) Surface Interference, and the intensity distributions that obtains is:

$I_n(x,y)=A^2(x,y)+A_r^2+2A_{r}A(x,y)\cos (\mathrm{\ψ}-{\mathrm{\δ}}_n),---\left(4\right)$

Here define U (x, y)=A (x, y) exp[i Ψ (x, y)], A _rBe the real amplitude of reference light wave, it is a normal number; The phase place δ of reference light wave _nCan be by phase shifting devices such as wave plate or piezoelectric device (PZT) control.The present invention adopts standard three to go on foot the phase shift interference art, by interfering with the reference light of introducing (phase place during three interference is respectively 0, pi/2 and π), can obtain three width and is modulated rear by phase-plate and contain the interferogram I that hides Info ₁, I ₂And I ₃, the non-negative image that they can be used as after encryption sends the take over party of information to by network or alternate manner, the geometric parameter of simultaneity factor and optical parametric G ₂, d ₁, d ₂Also together transmit in the past with λ.

After the take over party obtains all keys, rebuild original image on object plane by following steps:

(1) three step phase shift formula by standard recover the complex amplitude field U that records after encrypt on the plane:

$U(x,y)=\frac{1}{{4A}_r}[I_1-I_3+i({2I}_2-I_1-I_3)],---\left(5\right)$

(2) recover complex amplitude field on former input plane by twice contrary Fresnel transform

$O^{\′}(x_1,y_1)={\mathrm{IFrT}}_{d_1}\left\{{\mathrm{IFrT}}_{d_2}\right[U(x,y)\left]\exp \right[-i2\mathrm{\π}{P}_2(x_2,y_2)\left]\right\},---\left(6\right)$

(3) extract the real amplitude of O ', can decrypt hiding watermarking images.

Steal preventing for the security of further enhancing information, the present invention has also introduced digital watermark technology, namely by adding some plain code images to I ₁, I ₂And I ₃Disturb unwarranted recipient.At first, at interferogram I ₁, I ₂And I ₃In add same width image, be positive function a (x, y) with function representation.The actual image that transmits is in this case:

I’ ₁(x，y)＝I ₁(x，y)+wa(x，y)，I’ ₂(x，y)＝I ₂(x，y)+wa(x，y)，I’ ₃(x，y)＝I ₃(x，y)+wa(x，y)，(7)

Wherein w is weight factor, is a constant.Obviously, if use respectively I ' ₁, I ' ₂And I ' ₃Replace the I in formula (5) ₁, I ₂And I ₃, can obtain identical U (x, y).So add identical image on the not impact of recovery of hiding data in a cover interferogram.This is an obvious advantage of the present invention.

Fig. 2 has provided the software systems basic structure that realizes the inventive method on general purpose PC, and Fig. 3 and Fig. 4 have provided the two width software interface figure that realize the inventive method on the general purpose PC.Application program of the present invention adopts the Design Mode of Visual C++ and MATLAB hybrid programming, realizes the embedding extraction of the reading of watermarking images that host image that Fig. 6 is provided and Fig. 5 provide, watermark and to the operations such as attack test of watermark.Based on interactive interface and the basic function of the Information hiding enciphering/deciphering software of phase shift interference art, as image read and dialog box (Dialog) class design that the employing MFC such as the input of demonstration, parameter and output provide realizes; The design of core function (comprising the embedding of three step phase shift interference encryptions, deciphering and watermark) is by MATCOM, the source code of MATLAB to be translated into the C++ source code of same function, calls directly in Visual C++ that hybrid programming realizes.Fig. 7 has provided the image after watermarking images is encrypted, and Fig. 8 has provided watermarking images is embedded image after host image, and Fig. 9 has provided the watermarking images through correct deciphering.

The computing machine that method of the present invention can be made with a plurality of different vendors is realized together with the software of applicable any suitable language compilation.Adopt the Design Mode of Visual C++ and MATLAB hybrid programming, both kept the good algorithm of MATLAB, kept again the height of C++ to carry out efficient.

The present invention also is applicable to the application of optoelectronic information treatment technology.

Claims (1)

1. digital watermarking embedding and detection method based on three step phase shift interference arts, comprise the embedding of watermark and detection and the extraction of watermark, it is characterized in that:

(1) telescopiny of watermark:

11. the plane at digital watermarking image O place is called input plane, is close to the back of input plane and places first random phase plate G ₁, with wavelength be the monochromatic plane wave vertical irradiation of λ to input plane, numerical simulation calculation digital watermarking image O and random phase plate G ₁The product of complex amplitude transmitance, then this product being carried out distance parameter is d ₁Fresnel Diffraction Transform, obtain a complex amplitude field U ₂, this complex amplitude field U ₂The plane at place is called changing the plane;

12. be close to second random phase plate G of changing the plane back placement ₂, numerical simulation calculation U ₂And G ₂The product of complex amplitude transmitance, then this product being carried out distance parameter is d ₂Fresnel Diffraction Transform, obtain a complex amplitude field U, the plane at this U place, complex amplitude field is called records the plane, under recording on the plane the complex amplitude script holder record of carrying digital watermark information;

13. adopt three step phase shift interference arts, by interfering with the reference light of introducing, obtain three width and modulated by phase-plate and contain the interferogram I that hides Info ₁, I ₂And I ₃, the phase place during three interference is respectively 0, pi/2 and π;

14. encrypting rear three width interferogram I ₁, I ₂, I ₃Embed in host image, obtain I ₁ ^,, I ₂ ^,And I ₃ ^,As the non-negative image after encrypting, and pass to the take over party of information, simultaneously parameter G ₂, d ₁, d ₂With optical wavelength λ also together transmission;

(2) detection of watermark and leaching process:

21. recover according to three step phase shift formula the complex amplitude field U that records after encrypt on the plane;

22. making distance is d ₂Contrary fresnel diffraction;

Multiply by random phase plate G 23. draw complex amplitude ₂The complex conjugate of complex amplitude transmitance, carry out another distance and be d ₁Contrary fresnel diffraction;

24. extract real amplitude and the normalization of diffraction complex amplitude field.

Images