Dynamic optical scanning holographic encryption system and method based on time-space joint imaging

Abstract

The invention discloses a dynamic optical scanning holographic encryption system based on time-space joint imaging, which comprises a laser, a light beam emitted by the laser is divided into two light beams by a beam splitter, one transmission light beam irradiates an orbital angular momentum multiplexing hologram, and the other transmission light beam irradiates an orbital angular momentum multiplexing hologram. One beam of reflected light is transmitted to a beam combiner through a space-time coupling spring light generation module and an optical delay line module in sequence, and the other beam of reflected light is transmitted to the beam combiner through a plane mirror, an optical switch and an encryption key in sequence, so that the other beam of reflected light interferes with the time-delayed space-time coupling spring light to generate dynamic interference fringes, and the dynamic interference fringes are scanned through a Fourier transform lens and a scanner; the time-space coupling spring light generation module is used for generating time-space coupling spring light, and the optical delay line module is used for carrying out delay processing on the time-space coupling spring light and realizing accurate modulation time delay. The invention further discloses a dynamic optical scanning holographic encryption method based on time-space combined imaging.

Description

Technical Field

[0001] This invention belongs to the technical field of optical image encryption, specifically relating to a dynamic optical scanning holographic encryption system and method based on spatiotemporal joint imaging. Background Technology

[0002] As a fundamental data carrier, the importance of images in the information industry is self-evident. Video, with its time-flowing narrative and rich image information, better aligns with human subjective perception and plays a vital role in fields such as art appreciation, military modeling, and daily life. However, with the booming rise of a new round of technological revolution represented by network information technology, the use of image data has exploded, leading to increasingly serious information security issues.

[0003] In 1995, Professors Refregier and Javidi of the United States first proposed the Double Random Phase Encoding (DRPE) technique based on a 4f system. This technique uses two statistically independent random phase plates placed on the input and spectral planes of an optical 4f system as the primary encryption key. Finally, an encrypted image is obtained on the output plane of the system. The encrypted image is then a stationary random white noise, with the information of the original image completely hidden within the random white noise [P.Refregier, B. Javidi, Optical image encryption based on input plane and fourier plane random encodind, Opt. Lett., 20(7): 767-769, 1995]. Optical information security systems generally use optical information processing technology to encrypt, decrypt, hide, extract, or authenticate information. Due to its inherent advantages such as parallel data processing capabilities and multidimensional design freedom, optical information security technology has subsequently developed rapidly, attracting increasing attention from scholars both domestically and internationally. Subsequently, optical encryption methods based on fractional Fourier transform, Fresnel transform, and Merlin transform have been proposed. However, the aforementioned optical encryption technologies primarily target 2D images. In our daily lives, 3D images or videos best reflect the world as perceived by humans. Therefore, the information security of video images is a research hotspot in the security field. In the field of 3D image encryption, optical encryption methods based on digital holography digitize optical analog signals and generate encrypted holographic signals on the output plane using interference methods. To expand the receiving field of view and eliminate artifacts in coaxial reconstruction, TC Poon et al. combined optical scanning holography and dual random phase coding to propose optical scanning cryptography, using two-dimensional scanned Fresnel zone plates to encode images [TC Poon, T. Kim, K. Doh. Opticalscanning cryptography for secure wireless transmission. Applied Optics, 42:6496-6503 (2003)]. Although the aforementioned optical imaging encryption technologies have greatly promoted the development of information security for three-dimensional objects, they are static encryption methods that do not consider the temporal dimension of video information streams, resulting in low encryption system capacity. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a dynamic optical scanning holographic encryption method based on spatiotemporal joint imaging, which solves the technical problems of existing technologies not considering the temporal dimension of video information streams and having low encryption system capacity.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A dynamic optical scanning holographic encryption system based on spatiotemporal joint imaging includes a laser. The laser beam is split into two beams by a beam splitter. One transmitted beam illuminates an orbital angular momentum multiplexing hologram and is then transmitted sequentially through a spatiotemporal coupled spring light generation module and an optical delay line module to a beam combiner. The other reflected beam is transmitted sequentially through a plane mirror, an optical switch, and an encryption key to the beam combiner, where it interferes with the delayed spatiotemporal coupled spring light to generate dynamic interference fringes. These fringes are then scanned by a Fourier transform lens and a scanner to encrypt the video image and generate a dynamic encrypted hologram. The spatiotemporal coupling spring light generation module is used to generate spatiotemporal coupling spring light. The optical delay line module is used to perform propagation delay processing on the spatiotemporally coupled spring light to achieve precise modulation time delay.

[0006] Furthermore, the spatiotemporal coupling spring light generation module includes a first diffraction grating, a second diffraction grating, and a spatial light modulator. The first diffraction grating is placed on the front focal plane of the first concave mirror, the second diffraction grating is placed on the rear focal plane of the second concave mirror, and the spatial light modulator is placed on the rear focal plane of the first concave mirror and the front focal plane of the second concave mirror.

[0007] Furthermore, the optical delay line module includes a first plane mirror, a second plane mirror, and a third plane mirror arranged sequentially.

[0008] Furthermore, the laser is a linearly chirped ultrashort pulse laser used to generate ultrashort pulse lasers.

[0009] Furthermore, when the optical switch is off, the beam combiner only outputs the spatiotemporal coupling spring light; when the optical switch is on, the beam combiner will interfere with another beam of light carrying the encryption key and the spatiotemporal coupling spring light to generate dynamic interference fringes.

[0010] A dynamic optical scanning holographic encryption method based on spatiotemporal joint imaging, as described above, involves an ultrashort pulse laser emitted from a laser illuminating a beam splitter and splitting the light into two beams. One of the transmitted beams illuminates the orbital angular momentum multiplexing hologram, generating a composite vortex beam with multiple different frequencies and topological charges. This beam then sequentially illuminates the first diffraction grating and the first concave mirror, causing the light of different frequencies to illuminate the spatial light modulator at different angles for phase optimization. After sequentially illuminating the second concave mirror and the second diffraction grating, it generates a spatiotemporally coupled spring beam. This beam then passes through an optical delay line composed of the first, second, and third plane mirrors before illuminating the beam combiner. Another beam of reflected light shines on the fourth mirror, then passes through the optical switch and encryption key in sequence, and then shines on the beam combiner, causing it to interfere with the delayed spatiotemporal coupling spring light to produce dynamic interference fringes. After passing through the Fourier transform lens and the scanner in sequence, the video image is encrypted, generating a dynamic encrypted hologram. Finally, it is converted into a photoelectric image by a photodetector and stored in the computer.

[0011] Compared with the prior art, the beneficial effects of the present invention are: 1. By segmenting the video information stream in the time dimension and utilizing the orbital angular momentum multiplexing characteristics of vortex light, combined with an ultrashort pulse 4f shaping system, spatiotemporal coupled spring light is generated. The generation technology of spatiotemporal coupled spring light is then integrated with optical scanning holographic encryption technology, combining the time dimension of spatiotemporal coupled spring light with the three spatial dimensions of optical scanning holographic imaging to achieve spatiotemporal joint four-dimensional imaging and dynamic encryption. This breaks through the limitation of traditional optical scanning holography, which can only encrypt two-dimensional images or static 3D images. At the same time, the high-dimensional characteristics of orbital angular momentum and the use of superposition states fully ensure the security of large-capacity video information encryption.

[0012] 2. The encryption method proposed in this invention provides a pioneering approach for the application of ultrashort pulse lasers in optical information processing and imaging, and also has unique application potential in areas such as particle rotation and manipulation, optical information encoding, and laser-matter interaction. Furthermore, the method of this invention is based on classical interference theory, has relatively low experimental difficulty, utilizes mature spatial light modulator phase modulation technology, and features low dispersion in the pulse shaper, exhibiting strong practicality and innovation, and can also be applied to other optical fields. Attached Figure Description

[0013] Figure 1 This is a schematic flowchart illustrating the encryption method of the present invention; Figure 2 This is a schematic diagram of orbital angular momentum composite vortex light in one embodiment of the present invention; Figure 3 This is a schematic diagram of a time-space coupling spring-optical structure in one embodiment of the present invention; Figure 4 This is a schematic diagram of an encrypted hologram obtained in one embodiment of the present invention; Figure 5 This is a schematic diagram of the decryption result in one embodiment of the present invention; Figure 6 This is a schematic diagram of the encryption system of the present invention; Wherein, 0-Laser: Laser; 1-BS1: Beam splitter; 11-H1: Orbital angular momentum multiplexing hologram; 12-G1: First diffraction grating; 13-CM1: First concave mirror; 14-SLM: Spatial light modulator; 15-CM2: Second concave mirror; 16-G2: First diffraction grating; 17-19-M1, M2, M3: First plane mirror - Third plane mirror; 20-BS2: Beam combiner; 21-M4: Fourth plane mirror; 22-K1: Optical switch; 23-K2: Encryption key; 24-FL: Fourier transform lens; 25-SA: Scanner; 26-PD: Photodetector; O: Object. Detailed Implementation

[0014] To make the technical means, creative features, objectives and effects of the present invention easier to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate the dynamic optical scanning holographic encryption system and method based on spatiotemporal joint imaging of the present invention. It should be noted that the description of these embodiments is for the purpose of helping to understand the present invention, but does not constitute a limitation of the present invention.

[0015] like Figure 6 As shown, the present invention provides a dynamic optical scanning holographic encryption system based on spatiotemporal joint imaging, including a laser. The laser beam is split into two beams by a beam splitter. One beam illuminates an orbital angular momentum multiplexing hologram and is then transmitted to a beam combiner via a spatiotemporal coupling spring light generation module and an optical delay line module. The other beam is transmitted to the beam combiner via a plane mirror, an optical switch, and an encryption key, so that it interferes with the delayed spatiotemporal coupling spring light to generate dynamic interference fringes. The fringes are then scanned by a Fourier transform lens and a scanner to complete the encryption of the video image and generate a dynamic encrypted hologram. The spatiotemporal coupled spring light generation module is used to generate spatiotemporal coupled spring light, including a first diffraction grating, a second diffraction grating, and a spatial light modulator. The first diffraction grating is placed on the front focal plane of the first concave mirror, the second diffraction grating is placed on the rear focal plane of the second concave mirror, and the spatial light modulator is placed on the rear focal plane of the first concave mirror and the front focal plane of the second concave mirror. This optical delay line module is used to delay the propagation of spatiotemporally coupled spring light. It includes a first plane mirror, a second plane mirror, and a third plane mirror arranged in sequence to achieve precise modulation of time delay, so that interference fringes are generated after two ultrashort pulse beams pass through a beam combiner.

[0016] This laser uses a linearly chirped ultrashort pulse laser to generate ultrashort pulse lasers with a pulse width of 30~100 fs, a center wavelength of 600~1000 nm, and an arbitrary spot radius. The optimal values ​​are: pulse width of 30 fs, center frequency of 800 nm, and spot radius of 3 mm.

[0017] The orbital angular momentum reuse hologram is composed of topological charge. l The interference of vortex beams of 1, 3, 5, 7, and 9 with a Gaussian beam is generated.

[0018] In this way, when the optical switch is off, the beam combiner only outputs the spatiotemporal coupling spring light; when the optical switch is on, the beam combiner will interfere with the spatiotemporal coupling spring light to produce dynamic interference fringes.

[0019] Reference Figure 1 The present invention also provides a dynamic optical scanning holographic encryption method based on spatiotemporal joint imaging for a dynamic optical scanning holographic encryption system, the encryption and decryption processes of which are as follows: Encryption process: The ultrashort pulse laser generated by laser 0 is split into two beams by beam splitter 1. One of the transmitted beams is projected onto the orbital angular momentum multiplexing hologram 11, generating multiple beams of different frequencies. ω and different topological loads l The composite vortex light sequentially illuminates the first diffraction grating 12 and the first concave mirror 13. Light of different frequencies illuminates the spatial light modulator 14 at different angles. Optimized phase is loaded at different positions of the spatial light modulator 14 to eliminate dispersion. After passing through the second concave mirror 15 and the second diffraction grating 16, it generates spatiotemporal coupled spring light. Then, it passes through the optical delay line composed of the first plane mirror 17, the second plane mirror 18 and the third plane mirror 19, and illuminates the beam combiner 20. Another beam of reflected light shines on the fourth plane mirror 21, passes through the optical switch 22 and the encryption key 23 in sequence, and then shines on the beam combiner 20, causing it to interfere with the delayed spatiotemporal coupling spring light to produce dynamic interference fringes. After passing through the Fourier transform lens 24 and the scanner 25 in sequence, the video image is encrypted to generate a dynamic encrypted hologram. Finally, the photoelectric conversion is performed by the photodetector 26 and stored in the computer.

[0020] Decryption process: The decryption process is actually the image reconstruction process, which in this invention is the inverse process of holographic recording. With the correct decryption key, point source holograms are obtained at each video image location, and then the corresponding impulse response functions are obtained, allowing the correct video image to be reconstructed.

[0021] The optical switch 22 has two functions: when the optical switch is in the off state, it only outputs spatiotemporal coupling spring light after passing through the beam combiner 20; when the optical switch 22 is in the on state, it can generate interference fringes after passing through the beam combiner 20, generating a dynamic encrypted hologram.

[0022] To verify the feasibility of this invention, we conducted the following experiment: In this embodiment, the parameters selected for the ultrashort pulse laser 0 are: pulse width of 30 fs, center frequency of 800 nm, and spot radius of 3 mm; the orbital angular momentum multiplexing hologram 11 is composed of topological charge number l The interference of vortex beams with values ​​of 1, 3, 5, 7, and 9 with a Gaussian beam produces the following: Figure 2 The figures show the amplitude and phase distribution of the vortex light; when the optical switch 22 is turned off, the structure of the spatiotemporally coupled spring light output after passing through the beam combiner 20 is shown in the figure. Figure 3 As shown.

[0023] The plaintext to be encrypted is a video containing 5 frames. When the encryption key 23 is a random phase plate, the resulting encrypted hologram is as follows: Figure 4 As shown, all plaintext is encrypted into white noise, and the encryption effect is good.

[0024] When the decryption key is correct, the decrypted image is as follows: Figure 5 As shown, the five images that make up the miniature video were decrypted.

[0025] In summary, the encryption method proposed in this invention provides a pioneering approach for using strong-field ultrashort pulse lasers in optical information processing and imaging, and also has unique application potential in areas such as particle rotation and manipulation, optical information encoding, and the interaction between strong lasers and matter. Furthermore, this method is based on classical interference theory, has relatively low experimental difficulty, utilizes mature spatial light modulator phase modulation technology, and employs a pulse shaper with low dispersion, exhibiting strong practicality and innovation, and can also be applied to other optical fields.

[0026] It is important to note that the schemes and arrangements of this application shown in the exemplary embodiments are merely exemplary. Although only a few embodiments are described in detail in this disclosure, those who consult this disclosure will readily understand that many modifications are possible (e.g., variations in various parameter values ​​(temperature, power, humidity, etc.), installation arrangements, names, colors, logical orders, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in this application. Therefore, all such modifications are also included within the scope of the invention, and the order or sequence of any process or method steps may be changed or rearranged according to alternative embodiments. In the claims, any "apparatus plus function" clause is intended to cover the structure described herein for performing the function, and not only structurally equivalent but also equivalent in structure. Other substitutions, modifications, alterations, and omissions may be made in the design, operation, and arrangement of the exemplary embodiments without departing from the scope of the invention. Therefore, the invention is not limited to the particular embodiments but extends to a variety of modifications that still fall within the scope of the appended claims.

[0027] Furthermore, in order to provide a concise description of exemplary embodiments, not all features of actual embodiments (i.e., those features that are not relevant to the best mode of carrying out the invention as currently considered, or those features that are not relevant to implementing the invention) may be omitted.

[0028] It should be understood that numerous specific implementation decisions can be made during the development of any practical implementation, such as in any engineering or design project. Such development efforts may be complex and time-consuming, but for those skilled in the art who benefit from this disclosure, the development effort will be a routine work of design, manufacturing, and production without requiring much experimentation.

[0029] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A dynamic optical scanning holographic encryption system based on spatiotemporal joint imaging, characterized in that: The system includes a laser, whose emitted beam is split into two beams by a beam splitter. One transmitted beam illuminates an orbital angular momentum multiplexing hologram and is then transmitted sequentially through a spatiotemporal coupling spring light generation module and an optical delay line module to a beam combiner. The other reflected beam is transmitted sequentially through a plane mirror, an optical switch, and an encryption key to the beam combiner, where it interferes with the delayed spatiotemporal coupling spring light to generate dynamic interference fringes. These fringes are then scanned by a Fourier transform lens and a scanner to encrypt the video image, generating a dynamic encrypted hologram. The spatiotemporal coupling spring light generation module is used to generate spatiotemporal coupling spring light. The optical delay line module is used to generate optical delay lines to achieve precise modulation time delay.

2. The dynamic optical scanning holographic encryption system based on spatiotemporal joint imaging according to claim 1, characterized in that: The spatiotemporal coupling spring light generation module includes a first diffraction grating, a second diffraction grating, and a spatial light modulator. The first diffraction grating is placed on the front focal plane of the first concave mirror, the second diffraction grating is placed on the rear focal plane of the second concave mirror, and the spatial light modulator is placed on the rear focal plane of the first concave mirror and the front focal plane of the second concave mirror.

3. The dynamic optical scanning holographic encryption system based on spatiotemporal joint imaging according to claim 2, characterized in that: The optical delay line module includes a first plane mirror, a second plane mirror, and a third plane mirror arranged in sequence.

4. The dynamic optical scanning holographic encryption system based on spatiotemporal joint imaging according to claim 1, characterized in that: The laser is a linearly chirped ultrashort pulse laser used to generate ultrashort pulse lasers.

5. The dynamic optical scanning holographic encryption system based on spatiotemporal joint imaging according to claim 1, characterized in that: When the optical switch is off, the beam combiner only outputs the spatiotemporal coupling spring light; when the optical switch is on, the beam combiner will interfere with the spatiotemporal coupling spring light to generate dynamic interference fringes.

6. A dynamic optical scanning holographic encryption method based on spatiotemporal joint imaging, based on the dynamic optical scanning holographic encryption system based on spatiotemporal joint imaging as described in claim 1, characterized in that: An ultrashort pulse of laser light emitted by a laser is split into two beams by a beam splitter. One of the transmitted beams illuminates the orbital angular momentum multiplexing hologram, generating a composite vortex beam with multiple different frequencies and topological charges. This beam then sequentially illuminates the first diffraction grating and the first concave mirror, causing the light of different frequencies to illuminate the spatial light modulator at different angles for phase optimization. After sequentially illuminating the second concave mirror and the second diffraction grating, it generates a spatiotemporally coupled spring beam. This beam then passes through an optical delay line composed of the first, second, and third plane mirrors before illuminating the beam combiner. Another beam of reflected light shines on the fourth mirror, then passes through the optical switch and encryption key in sequence, and then shines on the beam combiner, causing it to interfere with the delayed spatiotemporal coupling spring light to produce dynamic interference fringes. After passing through the Fourier transform lens and the scanner in sequence, the video image is encrypted, generating a dynamic encrypted hologram. Finally, it is converted into a photoelectric image by a photodetector and stored in the computer.

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