Transmission-invariant structured light field generation system and method

Abstract

The present invention provides a system and method for generating a transmission-invariant structured light field. It relates to the technical field of optical transmission and solves the problem of being unable to achieve an arbitrary transmission-invariant structured light field. The method includes: emitting a laser beam through an input light field generation component, performing spatial filtering and beam expansion on the laser beam to convert it into a fundamental mode Gaussian beam, and transmitting the fundamental mode Gaussian beam to an optical field modulation component; through the optical field modulation component, loading a dynamic phase hologram obtained by combining the Fourier spectra of the transmission-invariant structured light fields at different positions with the corresponding propagation phases onto the fundamental mode Gaussian beam; and transmitting the loaded beam to an output light field acquisition component; through the output light field acquisition component, performing an inverse Fourier transform on the loaded beam and capturing the spots of the beam after the inverse Fourier transform at multiple preset positions. The present invention realizes the generation of an arbitrary transmission-invariant structured light field and has strong practicability.

Description

Technical Field

[0001] The present invention relates to the field of optical transmission technology, and particularly to a system and method for generating a transmission-invariant structured optical field. Background Art

[0002] A transmission-invariant structured optical field, also known as a non-diffracting beam, refers to a beam whose wavefront or cross-sectional light intensity distribution remains unchanged during spatial transmission. Compared with the traditional Gaussian laser mode, this beam can be transmitted over a long distance with very little energy loss. It has a wide range of applications in optical communication, optical imaging, particle manipulation, etc. In the past ten-odd years, a large number of exciting studies have emerged on typical non-diffracting beams such as Bessel beams and Airy beams. On the one hand, the Bessel beam is an exact solution of the Helmholtz equation's transmission-invariant mode and is one of the most typical non-diffracting beams. Its main lobe does not significantly broaden during long-distance transmission, showing non-diffracting characteristics. On the other hand, the Airy beam is a particular solution of the Schrödinger equation under paraxial conditions, and this solution has the characteristics of non-diffraction, self-acceleration, and self-healing. Therefore, the Airy-type beam also exhibits non-diffraction and self-repair characteristics. However, the non-diffracting propagation of such beams over a sufficiently long distance usually requires the beam to carry infinite energy, and when propagating over a short distance, the beam's side lobes can also have an adverse impact on related applications. In recent years, another type of non-diffracting beam has emerged. In the article "Robust propagation of pin-like optical beam through atmospheric turbulence" published on page 7 of Volume 4, Issue 7 of APL Photonics in 2019, a pin-shaped beam was proposed. This beam has a stable wavefront during long-distance propagation in free space and can resist diffraction and environmental turbulence. In the article "Free-space realization of tunable pin-like optical vortex beams" published on pages 1204 - 1212 of Volume 9, Issue 7 of Photonics Research in 2021, a pin-shaped vortex beam was proposed. This beam carrying angular momentum has an adjustable peak intensity and has strong anti-diffraction propagation, which is achieved by modulating the amplitude and phase distribution of a standard laser beam. However, these two beams can only generate specific transmission-invariant structured optical fields and cannot generate arbitrary transmission-invariant structured optical fields. Nonlinear optical solitons can also generate non-diffracting beams, but they require ideal nonlinear media and are not suitable for practical free-space applications. Therefore, realizing an arbitrary transmission-invariant structured optical field is an urgent problem to be solved in practical applications. Summary of the Invention

[0003] A brief summary of the present invention is given below to provide a basic understanding of certain aspects of the present invention. It should be understood that this summary is not an exhaustive summary of the present invention. It is not intended to identify the key or important parts of the present invention, nor is it intended to limit the scope of the present invention. Its purpose is only to present certain concepts in a simplified form as a prelude to the more detailed description that follows.

[0004] In view of this, the present invention provides a system and method for generating a transmission-invariant structured light field to at least solve the problem in the prior art that an arbitrary transmission-invariant structured light field cannot be realized.

[0005] According to one aspect of the present invention, there is provided a system for generating a transmission-invariant structured light field, including: an input light field generation component, a light field modulation component, and an output light field acquisition component;

[0006] The input light field generation component is configured to emit a laser beam, perform spatial filtering and beam expansion on the laser beam, convert it into a fundamental mode Gaussian beam, and transmit the fundamental mode Gaussian beam to the light field modulation component;

[0007] The light field modulation component loads a dynamic phase hologram obtained by combining the Fourier spectrum of the transmission-invariant structured light field at different positions with the corresponding propagation phase onto the fundamental mode Gaussian beam; and transmits the loaded beam to the output light field acquisition component;

[0008] The output light field acquisition component is configured to perform an inverse Fourier transform on the loaded beam and capture the spots of the beam after the inverse Fourier transform at a plurality of preset positions.

[0009] In a preferred embodiment of the present invention, the input light field generation component includes: a laser and a spatial filtering component, and the spatial filtering component includes: a first spatial filtering lens, a diaphragm, and a second spatial filtering lens;

[0010] The first spatial filtering lens and the second spatial filtering lens are arranged coaxially to form a 4f beam expansion system, the diaphragm is disposed at the common focal point between the first spatial filtering lens and the second spatial filtering lens, and the laser beam generated by the laser passes through the first spatial filtering lens and converges to the diaphragm, and then passes through the diaphragm and is expanded by the second spatial filtering lens to form a fundamental mode Gaussian beam.

[0011] In a preferred embodiment of the present invention, the system further includes: a polarization beam splitter component;

[0012] The polarization beam splitter component performs polarization state conversion and intensity control on the fundamental mode Gaussian beam to form a fundamental mode Gaussian beam with a horizontal polarization state and transmits it to the light field modulation component.

[0013] In a preferred embodiment of the present invention, the polarization beam splitting component includes: a half-wave plate and a polarization beam splitter. The fundamental mode Gaussian beam is converted into a fundamental mode Gaussian beam with a horizontal polarization state through the half-wave plate and the polarization beam splitter, and the angle of the half-wave plate is adjusted so that the intensity of the fundamental mode Gaussian beam with a horizontal polarization state emerging from the polarization beam splitter meets a preset condition.

[0014] In a preferred embodiment of the present invention, the optical field modulation component includes: a liquid crystal-spatial light modulator or a digital micromirror.

[0015] In a preferred embodiment of the present invention, the output optical field acquisition component includes: a Fourier transform lens and a CCD camera. The loaded beam undergoes an inverse Fourier transform through the Fourier transform lens, and the spots of the beam after the inverse Fourier transform are captured by the CCD camera at multiple preset positions.

[0016] In a second aspect, the present invention also provides a method for generating a transmission-invariant structured optical field, including:

[0017] Emitting a laser beam through an input optical field generation component, performing spatial filtering and beam expansion on the laser beam to convert it into a fundamental mode Gaussian beam, and transmitting the fundamental mode Gaussian beam to the optical field modulation component;

[0018] Through the optical field modulation component, loading a dynamic phase hologram obtained by combining the Fourier spectra of the transmission-invariant structured optical fields at different positions with the corresponding propagation phases onto the fundamental mode Gaussian beam; and transmitting the loaded beam to the output optical field acquisition component;

[0019] Through the output optical field acquisition component, performing an inverse Fourier transform on the loaded beam, and capturing the spots of the beam after the inverse Fourier transform at multiple preset positions.

[0020] In a preferred embodiment of the present invention, before transmitting the fundamental mode Gaussian beam to the optical field modulation component, it further includes:

[0021] Performing polarization state conversion and intensity control on the fundamental mode Gaussian beam through a polarization beam splitting component to form a fundamental mode Gaussian beam with a horizontal polarization state, and transmitting it to the optical field modulation component.

[0022] In a preferred embodiment of the present invention, loading a dynamic phase hologram obtained by combining the Fourier spectra of the transmission-invariant structured optical fields at different positions with the corresponding propagation phases onto the fundamental mode Gaussian beam includes:

[0023] Combining the Fourier spectra of the transmission-invariant structured light fields at different positions with the spatial propagation phase to generate a dynamic phase hologram, and using the dynamic phase hologram to perform complex amplitude modulation on the fundamental mode Gaussian beam with a horizontal polarization state.

[0024] In a preferred embodiment of the present invention, loading the dynamic phase hologram obtained by encoding the Fourier spectra of the transmission-invariant structured light fields at different positions with the corresponding propagation phases onto the fundamental mode Gaussian beam includes:

[0025] Changing the distance between the transmission-invariant structured light field and the virtual Fourier transform lens in a digitally controlled manner, and based on the complex amplitude modulation method, generating the phase holograms corresponding to different positions of the transmission-invariant structured light field relative to the virtual Fourier transform lens through encoding calculations;

[0026] Loading the corresponding phase hologram at each position onto the fundamental mode Gaussian beam with a horizontal polarization state.

[0027] The present invention realizes the digital control of the transmission-invariant structured light field through the relationship between the transmission-invariant distance of the incident light field in the 4f system and the focal length of the lens. Based on the characteristics of the 4f system and the angular spectrum theory, by loading the holograms of the continuously varying structured light field onto the spatial light modulator, the generation of any transmission-invariant structured light field is realized, which has strong practicability. Compared with the optical needle beam and the free-space needle-shaped vortex beam, the system and method provided by the present invention have the advantage of realizing the transmission invariance of any structured light field in space. In addition, compared with optical solitons, the system and method provided by the present invention do not require an ideal nonlinear medium and are suitable for practical free-space applications. Compared with linear non-diffracting beams (such as Bessel beams, Airy beams, etc.), the system and method provided by the present invention can achieve non-diffracting propagation without carrying infinite energy. It has wide applications in optical scanning, optical imaging, particle manipulation, etc.

[0028] These and other advantages of the present invention will become more apparent from the following detailed description of the best embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention can be better understood by referring to the descriptions given in the following in conjunction with the accompanying drawings, in which the same or similar reference numerals are used throughout the drawings to denote the same or similar components. The accompanying drawings, together with the following detailed description, are included in this specification and form a part of this specification, and are further used to illustrate the preferred embodiments of the present invention and to explain the principles and advantages of the present invention. In the drawings:

[0030] Figure 1 is a schematic structural diagram showing the transmission-invariant structured light field generation system of the present invention;

[0031] Figure 2 is an exemplary schematic diagram showing the principle of the transmission-invariant structured light field generation method of the present invention;

[0032] Figure 3 is a spot schematic diagram showing the transmission-invariant super-Gaussian beam of the present invention;

[0033] Figure 4 is a spot schematic diagram showing the transmission-invariant perfect vortex beam of the present invention;

[0034] Figure 5 is a spot schematic diagram showing the transmission-invariant superposition circular Airy beam of the present invention;

[0035] Wherein, 1 represents a laser, 2 represents a first spatial filtering lens, 3 represents a diaphragm, 4 represents a second spatial filtering lens, 5 represents a half-wave plate, 6 represents a polarization beam splitter, 7 represents a light field modulation component, 8 represents a Fourier transform lens, and 9 represents a CCD camera;

[0036] Figure 3 (a) is a schematic diagram of the light field distribution of the transmission-invariant super-Gaussian beam;

[0037] Figure 3 (b) is Figure 3 (a) the spot image at the dotted line position;

[0038] Figure 3 (c) is Figure 3 (b) the light intensity distribution curve graph at the dotted line position;

[0039] Figure 4 (a) is a schematic diagram of the light field distribution of the transmission-invariant perfect vortex beam;

[0040] Figure 4 (b) is Figure 4 (a) the spot image at the dotted line position;

[0041] Figure 4 (c) is Figure 4 (b) the light intensity distribution curve graph at the dotted line position;

[0042] Figure 5 (a) is a schematic diagram of the light field distribution of the transmission-invariant superposition circular Airy beam;

[0043] Figure 5 (b) is Figure 5 (a) the spot image at the dotted line position.

[0044] Those skilled in the art should understand that the elements in the drawings are shown only for simplicity and clarity and are not necessarily drawn to scale. For example, the dimensions of some elements in the drawings may be enlarged relative to other elements to help improve the understanding of the embodiments of the present invention. Detailed implementation manners

[0045] In the following, exemplary embodiments of the present invention will be described in conjunction with the accompanying drawings. For the sake of clarity and conciseness, not all features of the actual implementation manners are described in the specification. However, it should be understood that many implementation-specific decisions must be made during the development of any such actual implementation manner in order to achieve the specific goals of the developer, for example, to comply with those system- and business-related constraints, and such constraints may vary with different implementation manners. In addition, it should also be understood that although the development work may be very complex and time-consuming, for those skilled in the art who benefit from the present disclosure, such development work is merely a routine task.

[0046] Here, it should also be noted that in order to avoid obscuring the present invention due to unnecessary details, only the device structures and / or processing steps closely related to the solution according to the present invention are shown in the drawings, while other details less related to the present invention are omitted.

[0047] As Figure 1 shown, an embodiment of the present invention provides a transmission-invariant structured light field generation system, including: an input light field generation component, a light field modulation component, and an output light field acquisition component;

[0048] The input light field generation component is configured to emit a laser beam, perform spatial filtering and beam expansion on the laser beam, convert it into a fundamental mode Gaussian beam, and transmit the fundamental mode Gaussian beam to the light field modulation component;

[0049] The light field modulation component loads a dynamic phase hologram obtained by combining the Fourier spectra of the transmission-invariant structured light fields at different positions with the corresponding propagation phases onto the fundamental mode Gaussian beam; and transmits the loaded beam to the output light field acquisition component;

[0050] The output light field acquisition component is configured to perform an inverse Fourier transform on the loaded beam and capture the spots of the beam after the inverse Fourier transform at a plurality of preset positions.

[0051] In a preferred embodiment of the present invention, the input light field generation component includes: a laser 1 and a spatial filtering component, and the spatial filtering component includes: a first spatial filtering lens 2, a diaphragm 3, and a second spatial filtering lens 4;

[0052] The first spatial filtering lens 2 and the second spatial filtering lens 4 are coaxially arranged to form a 4f beam expander system. The aperture 3 is disposed at the common focus between the first spatial filtering lens 2 and the second spatial filtering lens 4. The laser beam generated by the laser 1 is converged to the aperture 3 through the first spatial filtering lens 2 and transmitted through the aperture 3 to the second spatial filtering lens 4 for beam expansion, forming a fundamental mode Gaussian beam.

[0053] In the embodiment of the present invention, the aperture 3 can be a small hole. The first spatial filtering lens 2 and the second spatial filtering lens 4 form a coaxially arranged beam expander system. Among them, the focal length of the first spatial filtering lens 2 is less than the focal length of the second spatial filtering lens 4, and the aperture 3 is at the common focus of the two spatial filtering lenses.

[0054] In a preferred embodiment of the present invention, the system further includes: a polarization beam splitter assembly;

[0055] The polarization beam splitter assembly performs polarization state conversion and intensity control on the fundamental mode Gaussian beam to form a fundamental mode Gaussian beam with a horizontal polarization state and transmits it to the optical field modulation component 7.

[0056] In a preferred embodiment of the present invention, the polarization beam splitter assembly includes: a half-wave plate 5 and a polarization beam splitter 6. The half-wave plate 5 and the polarization beam splitter 6 are arranged along the optical path at the rear side of the second spatial filtering lens 4. The fundamental mode Gaussian beam is converted into a fundamental mode Gaussian beam with a horizontal polarization state through the half-wave plate 5 and the polarization beam splitter 6, and the angle of the half-wave plate 5 is adjusted so that the intensity of the fundamental mode Gaussian beam with a horizontal polarization state emitted through the polarization beam splitter 6 meets a preset condition.

[0057] In the embodiment of the present invention, the polarization beam splitter 6 is fixedly arranged behind the second spatial filtering lens 4, and the intensity of the fundamental mode Gaussian beam with a horizontal polarization state is controlled by rotating the half-wave plate 5 so that the emitted intensity meets a preset condition.

[0058] In a preferred embodiment of the present invention, the optical field modulation component 7 includes: a liquid crystal-spatial light modulator or a digital micromirror.

[0059] In a preferred embodiment of the present invention, the output optical field acquisition component includes: a Fourier transform lens 8 and a CCD camera 9. The loaded beam undergoes an inverse Fourier transform through the Fourier transform lens 8, and the spot of the beam after the inverse Fourier transform is captured by the CCD camera 9 at a plurality of preset positions.

[0060] In the embodiment of the present invention, the Fourier transform lens 8 can be a convex lens with a focal length of 200 mm.

[0061] In an embodiment of the present invention, the laser beam emitted by the laser 1 is converted into a Gaussian TEM 00 mode through a spatial filtering component composed of a first spatial filtering lens 2, a diaphragm 3, and a second spatial filtering lens 4. To control the polarization state and intensity of the output beam, a half-wave plate 5 and a polarization beam splitter 6 are introduced. Next, the transmitted TEM 00 mode beam with horizontal polarization irradiates the optical field modulation component 7 (the optical field modulation component includes a spatial light modulation device, such as a liquid crystal-spatial light modulator or a digital micromirror, etc.). An encoded dynamic phase hologram is loaded on the spatial light modulation device, combining the Fourier spectrum of the structured light field at different positions with the corresponding propagation phase. In this way, the phase hologram can be encoded based on complex amplitude modulation to form a dynamic hologram. Then, a Fourier transform lens 8 with a focal length of 200 mm is used for inverse Fourier transform, and the CCD camera 9 is moved to capture the light spots at different positions.

[0062] In a second aspect, the present invention also provides a method for generating a transmission-invariant structured light field, including:

[0063] Generating a laser beam through an input optical field generation component, performing spatial filtering and beam expansion on the laser beam, converting it into a fundamental mode Gaussian beam, and transmitting the fundamental mode Gaussian beam to the optical field modulation component;

[0064] Through the optical field modulation component, loading a dynamic phase hologram obtained by combining the Fourier spectrum of the transmission-invariant structured light field at different positions with the corresponding propagation phase onto the fundamental mode Gaussian beam; and transmitting the loaded beam to the output optical field acquisition component;

[0065] Through the output optical field acquisition component, performing inverse Fourier transform on the loaded beam, and capturing the light spots of the beam after inverse Fourier transform at multiple preset positions.

[0066] In a preferred embodiment of the present invention, before transmitting the fundamental mode Gaussian beam to the optical field modulation component, it further includes:

[0067] Converting the polarization state and controlling the intensity of the fundamental mode Gaussian beam through a polarization beam splitting component to form a fundamental mode Gaussian beam with a horizontal polarization state, and transmitting it to the optical field modulation component.

[0068] In a preferred embodiment of the present invention, loading a dynamic phase hologram obtained by combining the Fourier spectrum of the transmission-invariant structured light field at different positions with the corresponding propagation phase onto the fundamental mode Gaussian beam includes:

[0069] Combining the Fourier spectra of the transmission-invariant structured light fields at different positions with the spatial propagation phase to generate a dynamic phase hologram, and using the dynamic phase hologram to perform complex amplitude modulation on the fundamental mode Gaussian beam with a horizontal polarization state.

[0070] In a preferred embodiment of the present invention, loading the dynamic phase hologram obtained by encoding the Fourier spectra of the transmission-invariant structured light fields at different positions in combination with the corresponding propagation phases onto the fundamental mode Gaussian beam includes:

[0071] Changing the distance between the transmission-invariant structured light field and the virtual Fourier transform lens in a digitally controlled manner, and generating the phase holograms corresponding to different positions of the transmission-invariant structured light field relative to the virtual Fourier transform lens through encoding calculation based on the complex amplitude modulation method;

[0072] Loading the corresponding phase hologram at each position onto the fundamental mode Gaussian beam with a horizontal polarization state.

[0073] In the embodiment of the present invention, the phase hologram of the transmission-invariant structured light field is generated in a digitally controlled manner. The Fourier transform lens in the optical field modulation component has no physical object in the optical path and is added to the process of generating the phase hologram in the form of a virtual Fourier transform lens in code form.

[0074] The principle of generating the transmission-invariant structured light field in the example of the present invention: First, place the incident light field on the object plane of a 4f system composed of two Fourier transform lenses. Then, move the incident light field towards the first Fourier transform lens. The distance where the incident light field is transmission-invariant behind the second Fourier transform lens is related to the moving distance of the incident light field and the focal lengths of the two Fourier transform lenses. By controlling the incident light field to move a small distance towards the first Fourier transform lens and gradually reach the front surface of the first Fourier transform lens. This process can achieve the non-diffracting propagation of the incident light field within a certain distance to obtain a transmission-invariant light field.

[0075] Specifically, as Figure 2 , it is known that the distance from the incident light field U1(x1, y1) to the first lens is d0, the focal length of the first Fourier transform lens is f1, the focal length of the second Fourier transform lens is f2, and the position where the outgoing light field is invariant with the incident light field is z.

[0076] U2(f x , f y ) is the frequency domain expression of the light field U2(x2, y2) at the back focal plane of U1(x1, y1) passing through the first Fourier transform lens.

[0077]

[0078] Among them, are the spatial frequencies in the x and y directions, i is the imaginary unit, and λ is the wavelength corresponding to the incident light field U1(x1, y1).

[0079] U2(x2, y2) propagates through the second Fourier transform lens to its rear focal plane, which is equivalent to a single inverse Fourier transform, and the expression is as follows:

[0080]

[0081] U3(x3, y3) is the expression of the light field emerging from the rear focal plane of the second lens, and then propagates through space to the light field at a distance z:

[0082]

[0083] where k is the wave number.

[0084] According to the expression of U3(x3, y3), we get:

[0085]

[0086] Therefore,

[0087]

[0088] When (i.e., ) :

[0089]

[0090] Taking the inverse Fourier transform of both sides of the above equation, that is:

[0091]

[0092] The intensity distribution at position z is:

[0093] I z (x z , y z ) ∝ I1(x1, y1).

[0094] Therefore, when , the intensity distribution of the emerging light field is consistent with that of the incident light field. Specifically, the incident light field on the front focal plane of the first Fourier transform lens moves towards the first Fourier transform lens. By adjusting the distance d0 between the incident light field and the first Fourier transform lens, that is, adjusting f1 - d0 to increase incrementally from 0 to f1 by a small distance, this process can achieve the non-diffracting propagation of the incident light field within a distance of f2 2 / f1 to obtain a propagation-invariant light field.

[0095] In the embodiments of the present invention, through a light field modulation component, digital regulation is performed. The first Fourier transform lens of the two Fourier transform lenses constituting the 4f system is based on complex amplitude modulation, and a hologram is generated through encoding calculation. By digitally regulating the distance between the incident light field and the first Fourier transform lens, a dynamic hologram is obtained, thereby generating a propagation-invariant structured light field.

[0096] Embodiment

[0097] A 532 nm laser source is adopted. The focal lengths of the two Fourier transform lenses constituting the 4f system are both 200 mm. Based on complex amplitude modulation, a hologram is generated through encoding calculation. By digitally regulating the distance between the incident light field and the first Fourier transform lens, a dynamic hologram is obtained, thereby generating a propagation-invariant structured light field. In this embodiment, several structured light fields with transmission changes are selected as the target light fields. Among them, the super-Gaussian beam has an obvious self-focusing tendency as the propagation distance increases and cannot maintain the propagation invariance of the flat-top beam. The perfect vortex beam is the Fourier transform of the Bessel beam and gradually transforms into the Bessel beam during propagation, and cannot maintain the propagation invariance of the perfect vortex beam. The superimposed circular Airy beam is evolved into various ring lattices during propagation and cannot maintain its original state. Such light fields can only be applied at a certain plane and will evolve into other light fields once propagated and cannot be applied. Using the system and method of the present invention, a propagation-invariant light field within a certain propagation distance can be obtained. The experimental results are as Figures 3 to 5 shown. Figure 3 The experimental result of the super-Gaussian beam with order N = 12 remaining unchanged during the spatial propagation of 500 mm. Figure 4 The experimental result of the perfect vortex beam with topological charge 5 remaining unchanged during the spatial propagation of 500 mm. Figure 5 The structured light field of the circular Airy beams with topological charges 2 and 12 superimposed and propagated to 50 mm in space, and the experimental result of keeping it unchanged during the spatial propagation of 50 mm. To show its propagation-invariant characteristics, the light field is extracted at Figure 3 (a), Figure 4 (a) and Figure 5 (a) The spot images at the dotted line positions are obtained respectively as Figure 3 (b), Figure 4 (b) and Figure 5 (b), and the light intensity distributions corresponding to the dotted line positions in Figure 3 (b) and Figure 4 (b) are extracted to obtain the light intensity distribution curves of Figure 3 (c) and Figure 4 (c) respectively. Through this embodiment, it is verified that digitally regulating the propagation-invariant structured light field can achieve the spatial propagation invariance of various structured light fields.

[0098] Although the present invention has been described in terms of a limited number of embodiments, those skilled in the art, having the benefit of the foregoing description, will appreciate that other embodiments can be contemplated within the scope of the invention as thus described. Additionally, it should be noted that the language used in this specification has been principally selected for readability and instructional purposes and not to limit or circumscribe the inventive subject matter. Accordingly, many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the appended claims. For the scope of the present invention, the disclosure herein is illustrative, not restrictive, and the scope of the invention is defined by the appended claims.

Claims

1. Transmission-invariant structured light field generation system, characterized in that Including: An input optical field generation component, an optical field modulation component, and an output optical field acquisition component; The input optical field generation component is configured to emit a laser beam, perform spatial filtering and beam expansion on the laser beam, convert it into a fundamental mode Gaussian beam, and transmit the fundamental mode Gaussian beam to the optical field modulation component; The optical field modulation component loads a dynamic phase hologram obtained by combining the Fourier spectra of the transmission-invariant structured optical fields at different positions with the corresponding propagation phases onto the fundamental mode Gaussian beam; and transmits the loaded beam to the output optical field acquisition component; The output optical field acquisition component is configured to perform an inverse Fourier transform on the loaded beam and capture the spots of the beam after the inverse Fourier transform at multiple preset positions; Through the optical field modulation component, digital regulation is carried out to form the first Fourier transform lens among the two Fourier transform lenses that make up the 4f system. The output optical field acquisition component includes the second Fourier transform lens among the two Fourier transform lenses of the 4f system. The incident optical field on the front focal plane of the first Fourier transform lens moves towards the first Fourier transform lens. By regulating the distance d0 between the incident optical field and the first Fourier transform lens, regulate f1 - d0 to increment from 0 to f1 at a tiny distance, so as to achieve the non-diffracting propagation of the incident optical field within the f2 2 / f1 distance, and realize loading the encoded dynamic phase hologram on the spatial light modulation device to obtain a transmission-invariant optical field, where f1 is the focal length of the first Fourier transform lens and f2 is the second Fourier transform lens.

2. The system according to claim 1, characterized in that The input optical field generation component includes: a laser and a spatial filtering component, and the spatial filtering component includes: a first spatial filtering lens, a diaphragm, and a second spatial filtering lens; The first spatial filtering lens and the second spatial filtering lens are arranged coaxially to form a 4f beam expansion system, the diaphragm is arranged at the common focal point between the first spatial filtering lens and the second spatial filtering lens, and the laser beam generated by the laser passes through the first spatial filtering lens and converges to the diaphragm, and then passes through the diaphragm and is expanded by the second spatial filtering lens to form a fundamental mode Gaussian beam.

3. The system according to claim 2, wherein It also includes: A polarization beam splitting component; The polarization beam splitting component performs polarization state conversion and intensity control on the fundamental mode Gaussian beam to form a fundamental mode Gaussian beam with a horizontal polarization state, and transmits it to the optical field modulation component.

4. The system according to claim 3, wherein The polarization beam splitting component includes: a half-wave plate and a polarization beam splitter. The fundamental mode Gaussian beam is converted into a fundamental mode Gaussian beam with a horizontal polarization state through the half-wave plate and the polarization beam splitter, and the angle of the half-wave plate is adjusted so that the intensity of the fundamental mode Gaussian beam with a horizontal polarization state emerging from the polarization beam splitter meets a preset condition.

5. The system according to claim 1, wherein The optical field modulation component includes: a liquid crystal-spatial light modulator or a digital micromirror.

6. The system according to claim 1, characterized in that The output optical field acquisition component includes: a Fourier transform lens and a CCD camera. The loaded beam passes through the Fourier transform lens for inverse Fourier transform, and the spots of the beam after the inverse Fourier transform are captured by the CCD camera at multiple preset positions.

7. Method for generating a transmission-invariant structured light field, characterized in that, Including: Emitting a laser beam through the input optical field generation component, performing spatial filtering and beam expansion on the laser beam, converting it into a fundamental mode Gaussian beam, and transmitting the fundamental mode Gaussian beam to the optical field modulation component; Through the optical field modulation component, loading a dynamic phase hologram obtained by combining the Fourier spectra of the transmission-invariant structured optical fields at different positions with the corresponding propagation phases onto the fundamental mode Gaussian beam; and transmitting the loaded beam to the output optical field acquisition component; Through the output optical field acquisition component, performing an inverse Fourier transform on the loaded beam and capturing the spots of the beam after the inverse Fourier transform at multiple preset positions; Loading the dynamic phase hologram obtained by combining the Fourier spectra of the transmission-invariant structured optical fields at different positions with the corresponding propagation phases onto the fundamental mode Gaussian beam includes: Combining the Fourier spectra of the transmission-invariant structured light fields at different positions with the spatial propagation phase to generate a dynamic phase hologram, and using the dynamic phase hologram to perform complex amplitude modulation on the fundamental mode Gaussian beam with a horizontal polarization state: including: Changing the distance between the transmission-invariant structured light field and the virtual Fourier transform lens in a digitally controlled manner, and based on the complex amplitude modulation method, generating the phase holograms corresponding to different positions of the transmission-invariant structured light field relative to the virtual Fourier transform lens through coded calculation; Loading the corresponding phase hologram at each position onto the fundamental mode Gaussian beam with a horizontal polarization state; Changing the distance between the transmission-invariant structured light field and the virtual Fourier transform lens in a digitally controlled manner, and based on the complex amplitude modulation method, generating the phase holograms corresponding to different positions of the transmission-invariant structured light field relative to the virtual Fourier transform lens through coded calculation includes: Through the optical field modulation component, digital regulation is carried out to form the first Fourier transform lens among the two Fourier transform lenses that make up the 4f system. The output optical field acquisition component includes the second Fourier transform lens among the two Fourier transform lenses of the 4f system. The incident optical field on the front focal plane of the first Fourier transform lens moves towards the first Fourier transform lens. By regulating the distance d0 between the incident optical field and the first Fourier transform lens, regulate f1 - d0 to increment from 0 to f1 at a tiny distance, so as to realize the non-diffracting propagation of the incident optical field within the f2 2 / f1 distance, and realize loading the encoded dynamic phase hologram on the spatial light modulation device to obtain the propagation-invariant optical field, where f1 is the focal length of the first Fourier transform lens and f2 is the second Fourier transform lens.

8. The method according to claim 7, wherein Before transmitting the fundamental mode Gaussian beam to the optical field modulation component, it further includes: Performing polarization state conversion and intensity control on the fundamental mode Gaussian beam through a polarization beam splitter component to form a fundamental mode Gaussian beam with a horizontal polarization state, and transmitting it to the optical field modulation component.

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