CN116931107A - Spatial information transmission device and method based on OAM single-pixel wavefront detection - Google Patents
Spatial information transmission device and method based on OAM single-pixel wavefront detection Download PDFInfo
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Abstract
The invention belongs to the crossing field of single-pixel imaging technology and space optical communication, and in the existing OAM information transmission technology, a complex multiplexing or keying technology and an OAM beam demodulation technology are required, so that the complexity of a communication system is increased. The invention provides a spatial information transmission device and a spatial information transmission method based on OAM single-pixel wavefront detection, which utilize different types of modulation bases to encode target information to be transmitted in a spatial two-dimensional form, sequentially send the target information to a free space and realize spatial information transmission by combining a single-pixel wavefront detection principle. Compared with the prior art, the transmitting end does not need an additional multiplexing technology or keying technology, the receiving end does not need an OAM light beam demodulation technology, the transmission device is simple, the modulation base can be flexibly selected according to actual needs and is not limited to an OAM mode, information transmission in a complex environment can be realized, the advantages of wide-band operation and the like are achieved, and a brand new technical scheme is provided for spatial information transmission.
Description
Technical Field
The invention belongs to the crossing field of single-pixel imaging technology and free space information transmission, and particularly relates to a space information transmission device and method based on OAM single-pixel wavefront detection.
Background
Single-pixel imaging is an emerging computational imaging technology with the advantages of high detection sensitivity, broad spectral response, accurate temporal resolution, and the like. When single-pixel imaging is combined with interferometry, spatial wavefront information, i.e., single-pixel wavefront-sensing techniques, can be further retrieved. In contrast to conventional array detector wavefront detection, single pixel detection enables wavefront detection to reconstruct a wavefront using a series of complex coefficients corresponding to the measurement mode.
Structural light fields with different spatial features provide various light field existence forms and are widely applied to the field of free space information transmission at present. Whereas an orbital angular momentum (orbital angular momentum, OAM) optical field with spatial phase variation is one of the typical structural optical fields, which carriesIs defined as the mode value or topology charge number of OAM, and theoretically can be any integer, ">Azimuth). And in theory, the OAM modes are unlimited, and the light beams carrying different orders of OAM are mutually orthogonal. The free space information transmission based on the OAM beam has great advantages in the aspects of improving the channel utilization rate, increasing the information transmission capacity and the like due to the characteristics of the OAM beam. Common OAM beams are of various types including Laguerre-Gaussian (LG) beams, bessel (Bessel) beams, perfect vortex beams, etc. The LG beam is relatively simple and convenient in experimental generation, and is one of the most widely applied OAM beams in the current free space information transmission system. The Bessel beam belongs to a non-diffraction beam and has self-recovery characteristics which are not possessed by other OAM beams. By virtue of this advantageBessel beams have also found many applications in the OAM free space information transmission field.
Based on the characteristics of the OAM beam, single-pixel wavefront detection techniques based on LG and Bessel beams have been demonstrated, but little research has been done in the field of OAM free space information transmission based on single-pixel imaging techniques. Currently, two mechanisms are mainly included for the application of OAM beams in the field of free space information transmission: OAM keying and OAM multiplexing. However, these modes require a relatively complex keying technology or multiplexing technology at the transmitting end and an OAM beam demodulation technology at the receiving end, so that the complex operation mechanism of the OAM beam at the transmitting and receiving ends limits the practical application of the OAM beam in the field of free space information transmission.
Disclosure of Invention
Aiming at the problems existing in the prior art, the invention provides a spatial information transmission device and method based on OAM single-pixel wavefront detection, which utilize different types of modulation bases such as Laguerre Gaussian, bessel and the like to encode target information to be transmitted in a spatial two-dimensional form, sequentially transmit the target information to a free space, and combine a single-pixel wavefront detection principle to realize remote spatial transmission of the information. The transmitting end of the invention has simple coding mode, no multiplexing technology or keying technology, no extra OAM light beam demodulation technology at the receiving end, the invention is suitable for information transmission in complex environment, has the advantages of wide band work, simple structure and the like, and the modulation base can be flexibly selected according to actual needs, is not limited to an OAM mode, thereby providing a brand new technical scheme for spatial information transmission.
In order to achieve the above purpose, the device and the method of the present invention are realized by the following technical schemes:
the utility model provides a spatial information transmission device based on OAM single pixel wavefront detection, includes sender and receiver, wherein: the transmitting end comprises a laser light source, a beam expander, a spatial light modulator and a 4-f system, wherein the 4-f system comprises a first lens, a diaphragm and a second lens; the laser source generates a light source, the light source is expanded by the beam expander and irradiates the surface of the spatial light modulator, the spatial light modulator loads a modulation mode, the modulated light beam is filtered out 1 st-order diffraction light by a diaphragm positioned on the central focal plane of the 4-f system, and the 1 st-order diffraction light is transmitted to a free space; the receiving end comprises a receiving end lens, a pinhole and a single-pixel detector, wherein the receiving end lens receives a light beam transmitted in space and performs Fourier transform, the pinhole and the single-pixel detector are arranged on a Fourier plane of the receiving end lens, and the pinhole is tightly attached to a detection plane of the single-pixel detector; the transmitting end is a reflective transmitting system or a transmissive transmitting system.
Further, when the transmitting end is a reflective transmitting system, an included angle between a beam of the laser light source expanded by the beam expander and a normal line of an acting surface of the spatial light modulator is not more than 10 degrees, and the spatial light modulator is arranged on a front focal plane of the first lens; when the transmitting end is a transmission type transmitting system, the laser light source and the beam expander are coaxially arranged with the spatial light modulator, and the spatial light modulator is arranged on the front focal plane of the first lens.
Further, the spatial light modulator is a liquid crystal spatial light modulator, a ferroelectric liquid crystal spatial light modulator, a digital micromirror device, a deformable mirror, or a modulation plate patterned with all modulation modes.
Based on the spatial information transmission device, the target information to be transmitted is coded in a spatial two-dimensional form by utilizing different types of modulation bases and sequentially transmitted to a free space, and the single-pixel wavefront detection principle is combined to realize the remote spatial transmission of the template information to be transmitted, and the method comprises the following specific steps:
step 1, constructing a spatial information transmission device based on OAM single-pixel wavefront detection, determining the aperture r of a pinhole, expanding a light source emitted by a laser light source through a beam expander, acting on a modulation area of a spatial light modulator, loading a modulation mode on the spatial light modulator, filtering out 1-level diffracted light on a Fourier plane of a first lens, filtering out other diffraction orders except the 1-level diffracted light by a diaphragm, and finally transmitting the light beam to a space through a 4-f system;
the size of the pinhole, the wavelength and the diameter of the light beam passing through the collecting and receiving end lens and the focal length of the receiving end lens meet the relation r less than or equal to 1.27 lambdaf/d, wherein lambdais the wavelength of the light beam, f is the focal length of the receiving end lens, and d is the diameter of the light beam; the light beams in the space are collected through a receiving end lens and are subjected to Fourier transform, pinholes are positioned on a Fourier plane of the receiving end lens and are filtered, and a single-pixel detector detects a signal intensity value of a central point of a Fourier domain;
step 2, determining initial parameters of a transmitting end: determining the resolution M multiplied by N and a modulation mode of two-dimensional information of target information to be transmitted, generating M multiplied by N OAM light beams with different orders and corresponding resolutions, and determining the phase shift steps of a single-pixel wave front detection technology;
step 3, dispersing and encoding M multiplied by N different-order OAM light beams with corresponding resolutions generated in the step 2 to be transmitted into Bessel mode complex amplitude in a space two-dimensional mode, sequentially transmitting the two-dimensional information to a free space, and dispersing and encoding the two-dimensional information to an amplitude or phase part of the Bessel mode if one frame of two-dimensional information is required to be transmitted; if two frames of two-dimensional information are required to be transmitted simultaneously, one frame of two-dimensional information is dispersedly encoded to an amplitude part of the Bessel mode, and the other frame of two-dimensional information is dispersedly encoded to a phase part of the Bessel mode; if more than two frames of two-dimensional information need to be transmitted, the two-dimensional information is realized through multiple times of receiving and transmitting;
step 4, sequentially generating OAM modes of different orders by using a spatial light modulator of a transmitting end, and acquiring corresponding intensity signals of the OAM modes of different orders after transmission by a single pixel detector of a receiving end; shifting the phase of M multiplied by N modulation modes respectively, sequentially loading the phase shift to a spatial light modulator, and simultaneously acquiring corresponding signal intensity values of a central point of a Fourier plane by a single-pixel detector;
step 5: decoding image information, recording signal intensity values detected by a single-pixel detector, and decoding two-dimensional information of target information to be transmitted from a scattered OAM mode by utilizing corresponding different-order OAM modes and combining a single-pixel reconstruction algorithm.
Further, in step 3, the method of scatter encoding the information to be transmitted into the Bessel mode with complex amplitude distribution in a spatial two-dimensional form is as follows:
(1) Selecting Bessel mode coding target information, and setting two frames of two-dimensional information to be transmitted to be respectively in polar coordinatesAnd->The mathematical expression of the Bessel beam is as follows:
wherein J l Is a class i zero order bessel function,is cylindrical in coordinates>For wave vector, λ is wavelength, l is the order of Bessel function, will +.>And->Amplitude and phase portions, respectively, encoded into Bessel modes, i.e
Where l=1, 2,3, … mxn, yielding in total mxn different order Bessel patterns; if only one frame of two-dimensional information is transmittedOr->The other frame is set as a full two-dimensional matrix;
(2) Selecting LG mode coding target information, and setting two frames of two-dimensional information to be transmitted as respectivelyAnd->The LG beam mathematical expression is as follows:
wherein the method comprises the steps ofIs cylindrical, k=2pi/λ is wavenumber, λ is wavelength, l is OAM mode value or called topology payload, p is radial mode value, +.>w 0 Is the Gaussian term beam radius, z R ＝πw 0 2 Lambda represents the Rayleigh distance, L p |l| Is Laguerre polynomial, (2p+|l|+1) arctan (z/z) R ) For Gouy phase, will +.>And->Respectively encoded into the amplitude and phase portions of LG patterns, i.e
Wherein p is greater than or equal to 0, changing p and l, and generating M multiplied by N LG modes of different orders in total; if only one frame of two-dimensional information is transmittedOr->The other frame is set to be a full two-dimensional matrix.
Further, the OAM beam in step 2 includes: LG beam, bessel beam, perfect vortex beam, elliptical vortex beam, partially correlated vortex beam.
Further, the multi-step phase shift in step 2 is: three-step phase shift, four-step phase shift or eight-step phase shift.
Further, the modulation modes in step 2 include complex amplitude modulation modes such as OAM, and Hadamard, fourier, discrete cosine transform DCT, krawtchouk, zernike, and random mode real modulation modes.
Further, the single-pixel reconstruction algorithm in the step 5 comprises a compressed sensing algorithm, a second-order correlation algorithm and a direct inversion algorithm.
Further, the transmission channel in step 3 includes a single channel mode and a dual channel mode, wherein the single channel mode includes only an amplitude channel or only a phase channel of the OAM mode, and the dual channel mode is an amplitude and phase dual channel of the OAM mode.
The invention utilizes the complex amplitude distribution characteristic of an OAM mode, adopts a single-pixel wavefront detection method to realize the spatial information transmission on the constructed spatial information transmission device based on OAM Shan Xiangsu wave detection, and has the following advantages:
1. thanks to the characteristics of the OAM beam, the optical fiber system has anti-interference capability on scattering media such as atmospheric turbulence and the like during spatial information transmission;
2. the invention realizes the dual-channel information transmission, namely an amplitude part and a phase part of a modulation base;
3. compared with the existing OAM beam communication technology, the transmitting end does not need multiplexing or keying technology, the receiving end does not need additional OAM beam demodulation technology, and the transmission device is simple;
4. the modulation base used can be selected according to actual needs, and is not limited to an OAM mode, so that information transmission in a complex environment can be realized;
5. the device has a simple structure, combines a single-pixel wavefront detection technology, and can be expanded to wider wave band application.
Drawings
FIG. 1 is a schematic diagram of a transmitting end of the present invention is a reflective transmitting system;
FIG. 2 is a schematic diagram of a transmission system at a transmitting end according to the present invention;
FIG. 3 is a schematic diagram of a two-pass Bessel mode encoding process of the method of the present invention;
FIG. 4 is a data image to be transmitted by a transmitting end with two channels;
fig. 5 is a data image of a two-channel reception at the receiving end.
In the figure, 1, a transmitting end, 2, a receiving end, 11, a laser light source, 12, a beam expander, 13, a spatial light modulator, 14, a first lens, 15, a diaphragm, 16, a second lens, 21, a receiving end lens, 22, a pinhole, 23 and a single pixel detector.
Detailed description of the preferred embodiments
The invention is described in further detail below with reference to the accompanying drawings.
For convenience of description, the following description will be made with respect to the direction corresponding to the direction of the drawing itself, but the structure of the present invention is not limited thereto.
As shown in fig. 1 to 5, the invention discloses a spatial information transmission device based on OAM single-pixel wavefront detection, which comprises a transmitting end 1 and a receiving end 2, wherein: the transmitting end 1 comprises a laser light source 11, a beam expander 12, a spatial light modulator 13 and a 4-f system, wherein the 4-f system comprises a first lens 14, a diaphragm 15 and a second lens 16; the laser light source 11 generates a light source, the light source is expanded by the beam expander 12 and irradiates the surface of the spatial light modulator 13, the spatial light modulator 13 loads a modulation mode, the modulated light beam is filtered out 1 st-order diffraction light by the diaphragm 15 positioned on the central focal plane of the 4-f system, and the 1 st-order diffraction light is transmitted to a free space; the receiving end 2 comprises a receiving end lens 21, a pinhole 22 and a single-pixel detector 23, wherein the receiving end lens 21 receives the light beam transmitted in space and performs Fourier transformation, the pinhole 22 and the single-pixel detector 23 are arranged on the Fourier plane of the receiving end lens 21, and the pinhole 22 is tightly attached to the detection plane of the single-pixel detector 23. The transmitting end 1 is a reflective transmitting system or a transmissive transmitting system;
when the transmitting end 1 is a reflective transmitting system, the laser light source 11 and the beam expander 12 are placed at a certain angle with the action surface of the spatial light modulator 13, so that the included angle between the beam after beam expansion and the normal line of the action surface of the spatial light modulator 13 is not more than 10 degrees, the spatial light modulator 13 is placed on the front focal plane of the first lens 14, the diaphragm 15 is placed on the central focal plane of the 4-f system formed by the first lens 14 and the second lens 16, and the receiving end pinhole 22 and the single-pixel detector 23 are placed on the fourier plane of the receiving end lens 21, as shown in fig. 1.
When the transmitting end 1 is a transmission type transmitting system, the laser light source 11, the beam expander 12 and the spatial light modulator 13 are horizontally placed, the spatial light modulator 13 is placed on the front focal plane of the first lens 14, the diaphragm 15 is placed on the central focal plane of the 4-f system formed by the first lens 14 and the second lens 16, and the receiving end pinhole 22 and the single pixel detector 23 are placed on the fourier plane of the receiving end lens 21, as shown in fig. 2.
The spatial light modulator is a liquid crystal spatial light modulator, a ferroelectric liquid crystal spatial light modulator, a digital micromirror device, a deformable mirror or a modulation plate which is characterized by all modulation modes. The present invention is exemplified by a liquid crystal spatial light modulator.
The invention also discloses a space information transmission method based on OAM single-pixel wavefront detection, which is based on the space information transmission device, and utilizes different types of modulation bases to encode target information to be transmitted in a space two-dimensional form, and sequentially sends the target information to a free space, and realizes the remote space transmission of template information to be transmitted by combining a single-pixel wavefront detection principle, and the method comprises the following specific steps:
step 1, constructing a spatial information transmission device based on OAM single-pixel wavefront detection, determining the aperture r of a pinhole 22, expanding a light source emitted by a laser light source 11 by a beam expander 12, acting on a modulation area of a spatial light modulator 13, loading a modulation mode on the spatial light modulator 13, filtering out 1-order diffracted light on a Fourier plane of a first lens 14, filtering out other diffraction orders except the 1-order diffracted light by a diaphragm 15, and finally transmitting the light beam to a space by a 4-f system.
The relation r < 1.27 lambda f/d is satisfied between the size of the pinhole 22 and the wavelength and diameter of the light beam passing through the collecting and receiving end lenses 21 and the focal length of the receiving end lenses 21, wherein lambda is the wavelength of the light beam, f is the focal length of the receiving end lenses 21, and d is the diameter of the light beam; the light beams in the space are collected through a receiving end lens 21 and are subjected to Fourier transform, a pinhole 22 is positioned on the Fourier plane of the receiving end lens 21 and is filtered, and a single-pixel detector 23 detects the signal intensity value of the central point of the Fourier domain;
step 2, determining initial parameters of the transmitting end 1: determining the resolution M multiplied by N and a modulation mode of two-dimensional information of target information to be transmitted, generating M multiplied by N OAM light beams with different orders and corresponding resolutions, and determining the phase shift steps of a single-pixel wave front detection technology; the OAM beam comprises: LG beam, bessel beam, perfect vortex beam, elliptical vortex beam, partially correlated vortex beam. Three-step phase shift, four-step phase shift or eight-step phase shift.
The modulation modes include complex amplitude modulation modes such as OAM, hadamard, fourier, discrete cosine transform DCT, krawtchouk, zernike, and random mode real modulation modes.
Step 3, dispersing and encoding M multiplied by N different-order OAM light beams with corresponding resolutions generated in the step 2 to be transmitted into Bessel mode complex amplitude in a space two-dimensional mode, sequentially transmitting the two-dimensional information to a free space, and dispersing and encoding the two-dimensional information to an amplitude or phase part of the Bessel mode if one frame of two-dimensional information is required to be transmitted; if two frames of two-dimensional information are required to be transmitted simultaneously, any one frame of two-dimensional information is dispersedly encoded to an amplitude part of the Bessel mode, and the other frame of two-dimensional information is dispersedly encoded to a phase part of the Bessel mode; if more than two frames of two-dimensional information need to be transmitted, the two-dimensional information is realized through multiple transceiving.
(1) Selecting Bessel mode coding target information, and setting two frames of two-dimensional information to be transmitted to be respectively in polar coordinatesAnd->The mathematical expression of the Bessel beam is as follows:
wherein J l Is a class i zero order bessel function,is cylindrical in coordinates>For wave vector, λ is wavelength, l is the order of Bessel function, will +.>And->Amplitude and phase portions, respectively, encoded into Bessel modes, i.e
Where l=1, 2,3, … mxn, yielding in total mxn different order Bessel patterns; if only one frame of two-dimensional information is transmittedOr->The other frame is set as a full two-dimensional matrix;
(2) Selecting LG mode coding target information, and setting two frames of two-dimensional information to be transmitted as respectivelyAnd->The LG beam mathematical expression is as follows:
wherein the method comprises the steps ofIs cylindrical, k=2pi/λ is wavenumber, λ is wavelength, l is OAM mode value or called topology payload, p is radial mode value, +.>w 0 Is the Gaussian term beam radius, z R ＝πw 0 2 Lambda represents the Rayleigh distance, L p |l| Is a Laguerre polynomial, (2p+|l|+1) arctan (z +. zR ) For Gouy phase, will +.>And->Respectively encoded into the amplitude and phase portions of LG patterns, i.e
Wherein p is greater than or equal to 0, changing p and l, and generating M multiplied by N LG modes of different orders in total; if only one frame of two-dimensional information is transmittedOr->The other frame is set to be a full two-dimensional matrix.
Step 4, sequentially generating OAM modes of different orders by using the spatial light modulator 13 of the transmitting end 1, and acquiring corresponding intensity signals of the OAM modes of different orders after transmission by the single-pixel detector 23 of the receiving end 2; the generated m×n modulation modes are phase-shifted respectively, and sequentially loaded to the spatial light modulator 13, while the single-pixel detector 23 collects the corresponding fourier plane center point signal intensity values.
Step 5: the image information is decoded, the signal intensity value detected by the single-pixel detector 23 is recorded, and the two-dimensional information of the target information to be transmitted is decoded from the scattered OAM mode by utilizing the corresponding different-order OAM modes and combining a single-pixel reconstruction algorithm, wherein the two-dimensional information refers to the two-dimensional information of the image information of the target to be transmitted, which is decoded from the recorded signal intensity value by the receiving end. The single pixel reconstruction algorithm comprises a compressed sensing algorithm, a second-order correlation algorithm and a direct inversion algorithm.
The OAM beam can be selected from an LG beam, a Bessel beam and the like, and the Bessel beam which is one of the commonly used OAM beams is taken as an example, has self-recovery characteristic, and is used for space information transmission occasions based on the Bessel beam single-pixel wavefront detection.
Embodiment one: the present embodiment is described with reference to fig. 1,2 and 3, and is a method for transmitting spatial information based on Bessel beam single-pixel wavefront detection, specifically comprising the following steps:
referring to fig. 1 and 2, a spatial image information data transmission transmitting terminal 1 device based on Bessel beam single-pixel wavefront detection is built. The light source emitted by the laser light source 11 is expanded by the beam expander 12, acts on the modulation area of the spatial light modulator 13, loads a grating on the spatial light modulator 13, aims to filter out 1 st-order diffraction light on the Fourier plane of the first lens 14, filters out other diffraction orders except the 1 st-order diffraction light by the diaphragm 15, and finally transmits the light beam to the space through a 4-f system formed by the first lens 14 and the second lens 16; determining the size of a pinhole 22 in the receiving end 2, wherein the size of the pinhole 22 and the wavelength and diameter of the light beam passing through the receiving end lens 21 and the focal length of the receiving end lens 21 satisfy the relation r less than or equal to 1.27 λf/d, wherein λ is the wavelength of the light beam, f is the focal length of the receiving end lens 21, and d is the diameter of the light beam; and constructing a spatial image information data transmission receiving end 2 device based on Bessel beam single-pixel wavefront detection. The light beam in space is collected by the receiving end lens 21 and fourier transformed, the pinhole 22 is located in the fourier plane of the receiving end lens 21 and filtered, and the single-pixel detector 23 detects the fourier domain center point.
Initial parameters of the transmission system are configured. Determining the resolution M multiplied by N of two-dimensional information data to be transmitted, generating M multiplied by N Bessel modes corresponding to different resolution steps, and determining the phase shift steps of a single-pixel wavefront detection technology; and dispersing and encoding the information to be transmitted into Bessel mode complex amplitude in a space two-dimensional form, and sequentially transmitting the information to be transmitted into free space. If a frame of two-dimensional information needs to be transmitted, the two-dimensional information is scattered and encoded to an amplitude or phase part of a Bessel mode; if two frames of two-dimensional information need to be transmitted simultaneously, one frame of two-dimensional information is dispersedly encoded to an amplitude part of the Bessel mode, and the other frame of two-dimensional information is dispersedly encoded to a phase part of the Bessel mode, as shown in fig. 3; the method for dispersedly encoding the information to be transmitted into the Bessel mode with complex amplitude distribution in a space two-dimensional form is as follows:
two frames of two-dimensional information to be transmitted are respectively set asAnd->The Bessel beam mathematical expression is as follows:
will beAnd->Amplitude and phase portions, respectively, encoded into Bessel modes, i.e
Where l=1, 2,3, … mxn, a total of mxn different order Bessel modes are generated if only one frame of two-dimensional information is transmittedOr->The other frame is set to be a full two-dimensional matrix.
The spatial light modulator 13 of the transmitting end 1 is used to sequentially generate OAM modes of different orders, while the single-pixel detector 23 of the receiving end 2 collects the intensity signals. The generated m×n modulation modes are phase-shifted respectively, and sequentially loaded to the spatial light modulator 13, while the single-pixel detector 23 collects the corresponding fourier plane center point signal intensity values.
Decoding the image information. The intensity values detected by the single-pixel detector 23 are recorded, and two-dimensional information is decoded from the scattered OAM pattern using the corresponding different-order OAM pattern in combination with a single-pixel reconstruction algorithm, the result of which is shown in fig. 5.
Embodiment two: taking a conventional reflective spatial light modulator, i.e. a liquid crystal spatial light modulator as an example, the spatial information transmission device and method based on OAM single-pixel wavefront detection based on the liquid crystal spatial light modulator are used in the spatial information transmission occasion, and the first embodiment is an example in which the spatial light modulator 13 is a reflective liquid crystal spatial light modulator.
Embodiment III: taking one of the conventional multi-step phase shifting methods, i.e., four-step phase shifting as an example, the present embodiment is an example in which the number of phase shifting steps is four-step phase shifting in the first embodiment.
Embodiment four: taking two-channel transmission of image data as an example, one to be transmitted includes a letter "E T" image and one to be transmitted "taiji" image, as shown in fig. 4, the spatial information is transmitted according to the steps of the first embodiment, and the data information decoded at the receiving end after the transmission is shown in fig. 5.
The transmitting end does not need an additional multiplexing technology or keying technology, the receiving end does not need an OAM light beam demodulation technology, the transmission device is simple, the modulation base can be flexibly selected according to actual needs and is not limited to an OAM mode, information transmission in a complex environment can be realized, the advantages of wide-band operation and the like are achieved, and a brand new technical scheme is provided for spatial information transmission.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above examples, and all technical solutions belonging to the concept of the present invention belong to the protection scope of the present invention. It should be noted that modifications and adaptations to the present invention may occur to one skilled in the art without departing from the principles of the present invention and are intended to be within the scope of the present invention.
Claims (10)
1. The spatial information transmission device based on OAM single-pixel wavefront detection is characterized by comprising a transmitting end (1) and a receiving end (2), wherein: the transmitting end (1) comprises a laser light source (11), a beam expander (12), a spatial light modulator (13) and a 4-f system, wherein the 4-f system comprises a first lens (14), a diaphragm (15) and a second lens (16); the laser light source (11) generates a light source, the light source is expanded by the beam expander (12) and irradiates the surface of the spatial light modulator (13), the spatial light modulator (13) loads a modulation mode, the modulated light beam is filtered out by the diaphragm (15) positioned on the central focal plane of the 4-f system, and the 1 st-order diffraction light is transmitted to the free space;
the receiving end (2) comprises a receiving end lens (21), a pinhole (22) and a single-pixel detector (23), wherein the receiving end lens (21) receives a light beam transmitted in space and performs Fourier transform, the pinhole (22) and the single-pixel detector (23) are arranged on a Fourier plane of the receiving end lens (21), and the pinhole (22) is tightly attached to a detection plane of the single-pixel detector (23);
the transmitting end (1) is a reflective transmitting system or a transmissive transmitting system.
2. The spatial information transmission device based on OAM single-pixel wavefront detection as set forth in claim 1, wherein when the transmitting end (1) is a reflective transmitting system, an angle between a beam of the laser light source (11) expanded by the beam expander (12) and a normal line of an acting surface of the spatial light modulator (13) is not more than 10 °, and the spatial light modulator (13) is disposed on a front focal plane of the first lens (14);
when the transmitting end (1) is a transmission type transmitting system, the laser light source (11) and the beam expander (12) are coaxially arranged with the spatial light modulator (13), and the spatial light modulator (13) is arranged on the front focal plane of the first lens (14).
3. The spatial information transmission device based on OAM single-pixel wavefront sensing as set forth in claim 1, wherein said spatial light modulator is a liquid crystal spatial light modulator, a ferroelectric liquid crystal spatial light modulator, a digital micromirror device, a deformable mirror, or a modulation panel patterned with all modulation modes.
4. The spatial information transmission method based on OAM single-pixel wavefront detection is based on the spatial information transmission device according to any one of claims 1-3, and is characterized in that target information to be transmitted is coded in a spatial two-dimensional form by utilizing different types of modulation bases and sequentially transmitted to free space, and the remote spatial transmission of template information to be transmitted is realized by combining a single-pixel wavefront detection principle, and specifically comprises the following steps:
step 1, constructing a spatial information transmission device based on OAM single-pixel wavefront detection, determining the aperture r of a pinhole (22), expanding a light source emitted by a laser light source (11) through a beam expander (12), acting on a modulation area of a spatial light modulator (13), loading a modulation mode on the spatial light modulator (13), filtering out 1 st-order diffracted light on a Fourier plane of a first lens (14), filtering out other diffraction orders except the 1 st-order diffracted light by a diaphragm (15), and finally transmitting the light beam to the space through a 4-f system;
the size of the pinhole (22) and the wavelength and diameter of the light beam passing through the collecting and receiving end lens (21) and the focal length of the receiving end lens (21) meet the relation r less than or equal to 1.27 lambda f/d, wherein lambda is the wavelength of the light beam, f is the focal length of the receiving end lens (21), and d is the diameter of the light beam; the light beams in the space are collected through a receiving end lens (21) and are subjected to Fourier transform, a pinhole (22) is positioned on a Fourier plane of the receiving end lens (21) and is filtered, and a single-pixel detector (23) detects a signal intensity value of a central point of a Fourier domain;
step 2, determining initial parameters of a transmitting end (1): determining the resolution M multiplied by N and a modulation mode of two-dimensional information of target information to be transmitted, generating M multiplied by N OAM light beams with different orders and corresponding resolutions, and determining the phase shift steps of a single-pixel wave front detection technology;
step 3, dispersing and encoding M multiplied by N different-order OAM light beams with corresponding resolutions generated in the step 2 to be transmitted into Bessel mode complex amplitude in a space two-dimensional mode, sequentially transmitting the two-dimensional information to a free space, and dispersing and encoding the two-dimensional information to an amplitude or phase part of the Bessel mode if one frame of two-dimensional information is required to be transmitted; if two frames of two-dimensional information are required to be transmitted simultaneously, one frame of two-dimensional information is dispersedly encoded to an amplitude part of the Bessel mode, and the other frame of two-dimensional information is dispersedly encoded to a phase part of the Bessel mode; if more than two frames of two-dimensional information need to be transmitted, the two-dimensional information is realized through multiple times of receiving and transmitting;
step 4, sequentially generating OAM modes of different orders by using a spatial light modulator (13) of the transmitting end (1), and acquiring corresponding intensity signals of the OAM modes of different orders after transmission by a single pixel detector (23) of the receiving end (2); shifting the phase of M multiplied by N modulation modes respectively, sequentially loading the phase shift to a spatial light modulator (13), and simultaneously acquiring corresponding Fourier plane central point signal intensity values by a single pixel detector (23);
step 5: decoding the image information, recording the signal intensity values detected by the single-pixel detector (23), and decoding the two-dimensional information of the target information to be transmitted from the scattered OAM modes by utilizing the corresponding different-order OAM modes and combining a single-pixel reconstruction algorithm.
5. The method for transmitting spatial information based on OAM single-pixel wavefront sensing as recited in claim 4, wherein in said step 3, the method for scatter-coding the information to be transmitted into the Bessel pattern having the complex amplitude distribution in a spatial two-dimensional form is as follows:
(1) Selecting Bessel mode coding target information, and setting two frames of two-dimensional information to be transmitted to be respectively in polar coordinatesAndthe mathematical expression of the Bessel beam is as follows:
wherein J l Is a class i zero order bessel function,is cylindrical in coordinates>For wave vector, λ is wavelength, l is the order of Bessel function, will +.>And->Amplitude and phase portions, respectively, encoded into Bessel modes, i.e
Where l=1, 2,3, … mxn, yielding in total mxn different order Bessel patterns; if only one frame of two-dimensional information is transmittedOr->The other frame is set as a full two-dimensional matrix;
(2) Selecting LG mode coding target information, and setting two frames of two-dimensional information to be transmitted as respectivelyAnd->The LG beam mathematical expression is as follows:
wherein the method comprises the steps ofIs cylindrical, k=2pi/λ is wavenumber, λ is wavelength, l is OAM mode value or called topology payload, p is radial mode value, +.>w 0 Is the Gaussian term beam radius, z R ＝πw 0 2 Lambda represents the Rayleigh distance, L p |l| Is Laguerre polynomial, (2p+|l|+1) arctan (z/z) R ) For Gouy phase, will +.>And->Respectively encoded into the amplitude and phase portions of LG patterns, i.e
Wherein p is greater than or equal to 0, changing p and l, and generating M multiplied by N LG modes of different orders in total; if only one frame of two-dimensional information is transmittedOr->The other frame is set to be a full two-dimensional matrix.
6. The spatial information transmission method based on OAM single pixel wavefront sensing as recited in claim 4, wherein said OAM beam in step 2 includes: LG beam, bessel beam, perfect vortex beam, elliptical vortex beam, partially correlated vortex beam.
7. The spatial information transmission method based on OAM single pixel wavefront sensing as recited in claim 4, wherein said multi-step phase shifting in step 2 is: three-step phase shift, four-step phase shift or eight-step phase shift.
8. The spatial information transmission method based on OAM single-pixel wavefront sensing as recited in claim 4, wherein said modulation modes in step 2 include OAM-like complex amplitude modulation modes, as well as Hadamard, fourier, discrete cosine transform DCT, krawtchouk, zernike, and random mode real modulation modes.
9. The spatial information transmission method based on OAM single-pixel wavefront sensing as recited in claim 4, wherein said single-pixel reconstruction algorithm in step 5 includes a compressed sensing algorithm, a second-order correlation algorithm, and a direct inversion algorithm.
10. The spatial information transmission method based on OAM single-pixel wavefront sensing as recited in claim 4, wherein said transmission channels in step 3 include a single channel mode and a dual channel mode, wherein the single channel mode includes only an amplitude channel or only a phase channel of the OAM mode, and the dual channel mode is two channels of the amplitude and the phase of the OAM mode.
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