Optical image information hiding and extraction method

Abstract

The present invention provides an optical image information hiding and extraction method, which belongs to the field of quantum imaging technology. The pump light generated by the pump laser generates a non-simple pump light through a nonlinear crystal and entangles a photon pair. The entangled light beam is split by a beam splitter and then reflected separately. The idle photons carrying the image information are hidden in a strong incoherent host light beam and cannot be stolen during the transmission process. The photon pair is a signal photon and an idle photon. When the entangled photon pair and the pump light pass through the nonlinear crystal again, a quantum induced coherence effect is generated. The signal photons are detected by a high-sensitivity camera to realize the extraction of hidden image information. The present invention hides the image information to be transmitted in a host light beam with a strength far greater than that of the host light beam, and extracts the hidden image information by using the quantum induced coherence effect at the receiving end, which significantly improves the security of free-space optical information transmission.

Description

Technical Field

[0001] The present invention relates to the field of quantum imaging technology, and in particular to an optical image information hiding and extraction method capable of significantly improving the security of free-space optical information transmission. Background Art

[0002] Given that free-space optical information transmission is vulnerable to eavesdropping and leakage, the demand for image encryption and information hiding technology has become increasingly prominent. To this end, researchers are actively exploring various image and information hiding transmission schemes, such as encoding images through degrees of freedom such as polarization and wavelength to achieve their hidden transmission. With the advancement of technology, the security risks of these encryption methods have become more and more obvious. Eavesdroppers can try to separate the hidden information from various degrees of freedom; with the improvement of computer computing power and the maturity of decryption algorithms, the speed of deciphering image codes is also rapidly increasing.

[0003] In order to improve the security of free-space optical information transmission, researchers have begun to explore new solutions based on the basic principles of quantum mechanics. Although some image hiding and transmission schemes that use the temporal correlation of entangled photon pairs have been proposed, these schemes usually require coincidence measurement of the photon pairs, and when the photon pairs are intercepted at the same time, the hidden information is at risk of being leaked. Summary of the invention

[0004] The object of the present invention is to provide a method for hiding and extracting optical image information to solve at least one technical problem existing in the above-mentioned background technology.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides an optical image information hiding and extraction method, comprising:

[0007] The pump light generated by the pump laser generates non-simple pump light through a nonlinear crystal and entangles the photon pairs. The entangled light beams are split by a beam splitter and reflected separately. The idler photons carrying image information are hidden in the strong incoherent host light beam and cannot be stolen during the transmission process. Among them, the photon pairs are signal photons and idler photons. When the entangled photon pairs and the pump light pass through the nonlinear crystal again, a quantum induced coherence effect is generated. The signal photons are detected by a high-sensitivity camera, which can realize the extraction of hidden image information.

[0008] Furthermore, the image information carrier to be transmitted is located in front of the reflector of the idler photons, and an incoherent strong host light beam is introduced in front of the reflector to hide the image information. After the host light beam is combined with the idler photons, it passes through the nonlinear crystal again together with the pump light and the signal photons, and the optical path is adjusted to cause a quantum induced coherence effect. At the receiving end, the image information to be transmitted is extracted by detecting the signal photon in the photon pair.

[0009] Optionally, the pump laser used is a narrow linewidth continuous laser.

[0010] Optionally, the nonlinear crystal is one of periodically poled lithium niobate, periodically poled potassium titanyl phosphate, barium metaborate, lithium niobate or lithium triborate.

[0011] Optionally, an incoherent light source generates an incoherent host light beam having a wavelength similar to that of an idler photon in a photon pair generated by the spontaneous parametric down-conversion process, wherein filtering is used to ensure that the incoherent light source does not emit light having a wavelength similar to that of the signal photon.

[0012] Optionally, the incoherent light source is an LED light source.

[0013] Furthermore, the detector or camera at the receiving end should have almost no response to photons of idler wavelengths, but have a higher detection efficiency for light of signal photon wavelengths.

[0014] Beneficial effects of the present invention: At the transmitting end, the wavelength carrying the image information is λ 2 The photon is hidden in a host beam with much greater intensity and consistent properties, making it almost impossible to steal. At the receiving end, through the quantum induced coherence effect, the photon is entangled with it and has a wavelength of λ. 1 The image information carried in the light beam is extracted.

[0015] Additional advantages of the present invention will be more clearly given in the following description or learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0017] Figure 1 This is a processing flow chart of the optical image hiding and extraction method described in an embodiment of the present invention.

[0018] Figure 2 Schematic diagram of an experimental device for the optical image hiding and extraction method according to an embodiment of the present invention.

[0019] Figure 3 Schematic diagram of relative spectral intensities of signal photons, idler photons, and host LED light beams according to an embodiment of the present invention.

[0020] Figure 4The image (i 1 ) and the image intercepted by the eavesdropper (i 2-3 ). DETAILED DESCRIPTION

[0021] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below by the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0022] It should be understood by those skilled in the art that unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs.

[0023] It should also be understood that terms, such as those defined in commonly used dictionaries, should be understood to have a meaning consistent with that in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless as defined herein.

[0024] Those skilled in the art will appreciate that, unless otherwise stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements and / or groups thereof.

[0025] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. Different embodiments or examples described in this specification and features of different embodiments or examples may be combined and combined by those skilled in the art without contradiction.

[0026] To facilitate understanding of the present invention, the present invention is further explained below with reference to specific embodiments in conjunction with the accompanying drawings, and the specific embodiments do not constitute a limitation on the embodiments of the present invention.

[0027] Those skilled in the art should understand that the drawings are merely schematic diagrams of embodiments, and the components in the drawings are not necessarily necessary for implementing the present invention.

[0028] The present invention proposes an image information hiding and extraction scheme based on quantum induced coherent imaging. The scheme does not require a complex coincidence measurement system, has a compact structure, flexible operation, and high security. Even when photon pairs are intercepted simultaneously, the information will not be at risk of being leaked due to eavesdropping, opening up new possibilities for the secure transmission of free-space optical information.

[0029] Example

[0030] In this embodiment, an optical image hiding and extraction scheme is provided, including: laser pumping nonlinear crystals to generate non-degenerate entangled photon pairs (signal photons and idler photons), which are reflected after splitting, and the idler photons carrying image information are hidden in strong incoherent host light beams, and cannot be stolen during transmission; when the entangled photon pairs and pump light pass through the nonlinear crystal again, a quantum induced coherence effect is generated, and the signal photons are detected by a high-sensitivity camera to achieve the extraction of hidden image information. The image information carrier to be transmitted is located in front of the reflector of the idler photons, and an incoherent strong host light beam is introduced in front of the reflector to hide the image information. After the host light beam is combined with the idler photons, it passes through the nonlinear crystal again together with the pump light and the signal photons, and the optical path is adjusted to cause a quantum induced coherence effect. At the receiving end, the image information to be transmitted is extracted by detecting the signal photons in the photon pair.

[0031] The system includes a pump laser, a nonlinear crystal, an incoherent light source and a number of dichroic mirrors; the laser used is a narrow linewidth continuous laser; the nonlinear crystal is usually periodically polarized lithium niobate, periodically polarized potassium titanyl phosphate, barium metaborate, lithium niobate, lithium triborate, etc. The incoherent host light beam is usually generated by an LED light source, which has a similar wavelength to the idler photons in the photon pair generated by the spontaneous parametric down-conversion process, and it is necessary to ensure that the light source does not emit light with a wavelength close to that of the signal photons by filtering and other means; the detector or camera at the receiving end should have almost no response to the photons of the idler photon wavelength, but have a higher detection efficiency for the light of the signal photon wavelength.

[0032] Specifically, Figure 1 As shown, the wavelength is λ p The spontaneous parametric down-conversion process of the continuous laser pumped second-order nonlinear crystal produces entangled photon pairs, and the wavelengths of the photons in the photon pairs are λ 1 With λ 2 , and λ 1 ≠λ 2 .

[0033] The wavelength is λ 1 The photons with wavelength λ are reflected by the dichroic mirror together with the pump beam. 2After that, all three are reflected by the reflector, and the corresponding reflector has a high reflectivity at the wavelength of the incident photon. The reflected photon pair and the pump light are incident on the second-order nonlinear crystal again, and the second spontaneous parametric down-conversion process occurs. The photons generated by the two spontaneous parametric down-conversion processes have almost the same properties, such as wavelength, polarization, intensity, spatial mode, etc.

[0034] The image information carrier is placed at a reflection wavelength of λ 2 In front of the reflector, the wavelength is λ 2 The photons of carry the image information. After passing through the crystal for the second time, due to the quantum induced coherence effect, the wavelength is λ 1 The photons with wavelength λ will also carry the image information. 1 The photons are separated and detected by a highly sensitive camera. The collimated incoherent LED beam is introduced into the system through a beam splitter placed in front of the image carrier. The intensity of the LED beam is much greater than the wavelength λ 2 photon, and its central wavelength, polarization and other properties should be the same or similar to that of the photon.

[0035] Among them, at the transmitting end, the wavelength carrying the image information is λ 2 The photon is hidden in the host LED beam, which is much stronger than its intensity and has the same properties as its own, and is almost impossible to steal. At the receiving end, through the quantum induced coherence effect, the entangled photon with a wavelength of λ is 1 The image information carried in the light beam is extracted.

[0036] like Figure 2 , Figure 3 , Figure 4 As shown, the experimental device in the following embodiment is used to simulate that in the image hiding transmission system, the eavesdropper intercepts all the light beam information in the channel of the free space image transmission system, but cannot extract the hidden image from the intercepted information by classical means.

[0037] The narrow line width 532nm laser emitted by Nd:YVO4 continuous laser is used as pump light. After collimation, it passes through barium metaborate crystal (β-BBO, cutting angle 22.1°) to produce a type I spontaneous parametric down conversion process with a wavelength of λ 1 =810nm (signal photon) and λ 2=1550nm (idler photon) entangled photon pair, pump light and 810nm signal photon are reflected by dichroic mirror 3, and then reflected by silver-plated reflector together with pump laser, their phase can be controlled by linear translation stage. 1550nm idler photon is reflected by a gold-plated reflector after passing through dichroic mirror 3, and the incoherent light beam emitted by collimated LED light source with central wavelength of 1550nm is combined with 1550nm idler photon through an unbalanced beam splitter and aligned in space. The hidden image carrier is a key-shaped mask, which is placed in front of LED light source and gold-plated reflector respectively, and both are at the same distance from dichroic mirror 3.

[0038] The reflected pump light, LED light and down-converted photon pairs pass through the BBO crystal (nonlinear optical crystal) again to produce a second spontaneous parametric down-conversion process. After the 810nm photons generated by the two parametric processes are reflected by the dichroic mirror 2, their interference pattern is detected by the single-photon camera, and the image information carried by the 1550nm photons is extracted from the 810nm photon interference pattern. Since the intensity of the incoherent LED beam is much greater than the intensity of the photons generated by the spontaneous parametric down-conversion, its wavelength, polarization state and other parameters are consistent with those of the idler photons. Therefore, it is extremely difficult for an eavesdropper to separate the idler photons with the same wavelength, polarization, single photon order and image information from the strong LED host beam.

[0039] In summary, the optical image information hiding and extraction method described in the embodiment of the present invention utilizes the noise robustness characteristics of the Zou-Wang-Mandel interferometer to hide the image information to be transmitted in a host light beam whose intensity is much greater than that of the host light beam, and extracts the hidden image information at the receiving end using the quantum induced coherence effect, thereby significantly improving the security of free-space optical information transmission. Since the intensity of the photons generated by the spontaneous parametric down-conversion process is extremely weak, usually at the single-photon level, its intensity is much smaller than that of the host LED light beam, and the light beam carrying the information has the same wavelength, polarization and other characteristics as the host light beam, so it is impossible to strip the information from the host light beam using existing technologies, and it has extremely high security. The system has a compact structure, flexible operation, and the potential for high integration. Compared with the traditional quantum ghost imaging system, it does not require any external triggering and complex coincidence counting system, and can directly use a high-sensitivity camera to obtain the transmitted image information.

[0040] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative work on the basis of the technical solution disclosed in the present invention should be included in the scope of protection of the present invention.

Claims

1. An optical image information hiding and extraction method, characterized in that: include: The pump light generated by the pump laser generates non-degenerate entangled photon pairs through the nonlinear crystal. The non-degenerate entangled photon pairs are split by the beam splitter and then reflected separately. The idler photons carrying image information are hidden in the strong incoherent host light beam and cannot be stolen during the transmission process. Among them, the non-degenerate entangled photon pairs are signal photons and idler photons. When the non-degenerate entangled photon pairs and the pump light pass through the nonlinear crystal again, a quantum induced coherence effect is generated. The signal photons are detected by a high-sensitivity camera to extract the hidden image information. Among them, the image information carrier to be transmitted is located in front of the reflector of the idler photon, and a strong incoherent host light beam is introduced in front of the reflector to hide the image information. After the strong incoherent host light beam is combined with the idler photon, it passes through the nonlinear crystal again together with the pump light and the signal photon. The optical path is adjusted to make the non-degenerate entangled photon pair after reflection produce quantum induced coherence effect. At the receiving end, the image information to be transmitted is extracted by detecting the signal photon in the non-degenerate entangled photon pair after the quantum induced coherence effect.

2. The optical image information hiding and extraction method according to claim 1, characterized in that: The pump laser used is a narrow linewidth continuous laser.

3. The optical image information hiding and extraction method according to claim 1, characterized in that: The nonlinear crystal is one of periodically poled lithium niobate, periodically poled potassium titanyl phosphate, barium metaborate, lithium niobate or lithium triborate.

4. The optical image information hiding and extraction method according to claim 1, characterized in that: The incoherent light source generates an incoherent host light beam having a wavelength similar to that of an idler photon in a photon pair generated by the spontaneous parametric down-conversion process, wherein filtering means are used to ensure that the incoherent light source does not emit light having a wavelength similar to that of the signal photon.

5. The optical image information hiding and extraction method according to claim 4, characterized in that: The incoherent light source is an LED light source.

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