Method and device for generating partially coherent self-repairing light beam based on frequency spectrum modulation

Abstract

The invention belongs to the technical field of information optics, and relates to a method and device for generating a partially coherent self-repairing light beam based on spectrum modulation, and the method comprises the steps: constructing a cross-spectral density function of the partially coherent light beam on a spectrum plane based on a Schell model correlation function and an amplitude function of the partially coherent light beam on the spectrum plane; constructing a cross-spectral density function of the partially coherent light beams on a source plane based on the cross-spectral density function and the kernel function of the spectrum plane; converting the cross spectral density function of the source plane into an ensemble average function of a partially coherent beam field; based on the cross spectral density function of the source plane and the ensemble average function of the partially coherent light beam field, obtaining a field implementation function of the partially coherent light beam; generating a plurality of random complex fields meeting the Schell model correlation function, and respectively inputting the plurality of random complex fields into the field implementation function to obtain a plurality of output fields; and coding the plurality of output fields to generate a plurality of holograms, and modulating the laser to be modulated based on each hologram to obtain a partially coherent self-repairing beam.

Description

Technical Field

[0001] The present invention relates to the field of information optics technology, and in particular to a method and a device for generating a partially coherent self-repairing light beam based on spectrum modulation. Background Art

[0002] Self-repair refers to the ability of a beam to restore its spatial intensity distribution after being scattered by an obstacle. It is one of the remarkable characteristics of non-diffracting beams, such as Bessel beams. However, since the lateral distribution and energy carried by non-diffracting beams are infinite, it is impossible to produce such non-diffracting beams with self-repairing properties through experiments. The latest research shows that in addition to non-diffracting beams, partially coherent beams with self-repairing capabilities can also be generated by controlling the laser, so that such partially coherent beams with self-repairing capabilities can be applied to the fields of inhomogeneous medium optical communications, microscopic particle manipulation, microscopy technology and quantum entanglement transmission.

[0003] Existing partially coherent beams with self-repairing properties are all realized by modulation in the spatial domain. For example, a radially polarized Gaussian Scherrer mode beam can self-reconstruct its light intensity distribution and polarization state in the focal plane when blocked by an opaque obstacle; an Hermite Gaussian Scherrer mode beam can still restore its light intensity distribution in the far field after encountering an obstacle during short-distance transmission; a partially coherent beam with a cross phase can self-repair its correlation structure in the focal plane after encountering an opaque obstacle; these partially coherent beams with self-repairing properties are all achieved by adjusting the phase distribution of the laser on the source plane, changing the relative phase relationship between the light field at various points in space, thereby changing the interference pattern (beam shape) and spatial intensity distribution of the beam. Since complex phase correlations are introduced in the spatial structure of the beam in the process of changing the beam shape, a "memory" type correlation exists between different parts of the beam. When a part of the beam is disturbed or blocked, due to the complex phase correlations between different parts, the remaining unblocked part of the beam can be used as an information source to provide a reference for the recovery of the blocked part of the beam, thereby giving the partially coherent beam self-repairing properties.

[0004] Since the intensity distribution of a light beam is closely related to its phase distribution, if the phase distribution of the light beam is adjusted to a specific mode on the source plane to give the light beam self-repairing ability, the change in the intensity distribution will cause a change in the phase distribution, thereby destroying the self-repairing mechanism. Therefore, the intensity distribution of a partially coherent light beam with self-repairing properties generated by modulating the light beam in the spatial domain cannot be arbitrarily controlled, which limits the application performance of the partially coherent light beam in various fields (such as imaging quality in the field of optical imaging, signal transmission quality in the field of optical communications, etc.); in addition, after changing the phase distribution of the partially coherent light beam on the source plane, the new phase pattern will change the interference and diffraction characteristics of the light beam, causing the intensity distribution of the light beam to change during propagation, thereby making the intensity distribution in the far field inconsistent with the intensity distribution at the source plane, that is, the intensity distribution stability of the light beam is poor.

[0005] In summary, the existing partially coherent light beams with self-repairing properties generated by modulating the light beam in the spatial domain have the problem that the light intensity distribution cannot be arbitrarily controlled and the light intensity distribution stability is poor. Summary of the invention

[0006] To this end, the technical problem to be solved by the present invention is to overcome the problem in the prior art that a partially coherent light beam with self-repairing properties is generated by modulating the light beam in the spatial domain, but the light intensity distribution cannot be arbitrarily adjusted and the stability of the light intensity distribution is poor.

[0007] In order to solve the above technical problems, the present invention provides a method for generating a partially coherent self-repairing light beam based on spectrum modulation, comprising: Based on the Schermer correlation function and the amplitude function of the partially coherent light beam in the spectrum plane, constructing the cross spectral density function of the partially coherent light beam in the spectrum plane; Based on the cross spectral density function and the kernel function of the frequency spectrum plane, construct the cross spectral density function of the partially coherent light beam in the source plane; and convert the cross spectral density function of the source plane into an ensemble average function of the partially coherent light beam field; Obtaining a field realization function of the partially coherent light beam based on a cross spectral density function of the source plane and an ensemble average function of the partially coherent light beam field; Generate a plurality of random complex fields whose coherence functions in the frequency domain satisfy the Shermo correlation function, and input the plurality of random complex fields into the field realization function respectively to obtain a plurality of output fields; The multiple output fields are respectively encoded to generate multiple holograms, and the laser to be modulated is modulated based on each hologram to obtain multiple modulated light beams, and the multiple modulated light beams are superimposed to obtain a partially coherent self-repairing light beam.

[0008] Preferably, the cross spectral density function of the frequency spectrum surface is expressed as: , in, Represents the cross spectral density function of the spectrum surface; , Represents the vector coordinates of any two points in the partially coherent beam in the spatial frequency domain; Represents the amplitude function of the spectrum surface; represents the Shermo correlation function.

[0009] Preferably, the cross spectral density function of the source plane is expressed as: , , , in, represents the cross spectral density function of the source plane; Represents the cross spectral density function of the spectrum surface; , Represents the vector coordinates of any two points in the partially coherent beam in the spatial frequency domain; Represents the amplitude function of the spectrum surface; represents the Shermo correlation function; , Represents the vector coordinates of any two points in the partially coherent beam in the spatial domain; represents the kernel function; denotes conjugation; represents Fourier transform; , ; The ensemble average function of the partially coherent beam field is expressed as: , in, represents the ensemble average function of the partially coherent beam field; , Represents the vector coordinates of any two points in the partially coherent beam in the spatial domain; Represents a field realization function; Indicates conjugation.

[0010] Preferably, the field realization function is expressed as: , in, Represents a field realization function; Represents the vector coordinates of any point in the partially coherent beam in the spatial domain; Indicates random replay; Represents the vector coordinates of any point in the partially coherent beam in the spatial frequency domain; Represents the amplitude function of the spectrum surface.

[0011] Preferably, generating a plurality of random complex fields satisfying the Shermo correlation function comprises: Use MATLAB's randn function to generate multiple Gaussian random numbers with zero mean and unit variance; Performing Fourier transform on the Shermo correlation function to obtain a target Shermo correlation function; The product of each of the Gaussian random numbers and the square root of the target Shermo correlation function is calculated respectively, and the product is Fourier transformed to obtain a plurality of random complex fields satisfying the Shermo correlation function.

[0012] Preferably, after obtaining the multiple output fields, the method further includes: superimposing the multiple output fields according to the mode superposition principle to obtain the far-field light intensity distribution function of the partially coherent self-repairing light beam.

[0013] Preferably, the far-field light intensity distribution function of the partially coherent self-repairing light beam is expressed as: , in, Represents the far-field intensity distribution function of the partially coherent self-repairing beam; Indicates the number of output fields; Indicates Output fields; Represents the vector coordinates of the partially coherent beam in the far-field plane of the spatial domain; Indicates conjugation.

[0014] The present invention also provides a device for generating a partially coherent self-repairing light beam based on spectrum modulation, which is used to implement the above-mentioned method for generating a partially coherent self-repairing light beam based on spectrum modulation, comprising: Helium-neon laser, used to generate laser light to be modulated; A polarizer, used for modulating the polarization direction of the laser to be modulated into horizontal polarization; A beam expander, used for expanding and collimating the laser light to be modulated emitted from the polarizer; A beam splitter, used for transmitting the laser light to be modulated emitted by the beam expander to the spatial light modulator, receiving a plurality of modulated light beams output by the spatial light modulator, and reflecting the plurality of modulated light beams; A spatial light modulator, used for receiving the laser light to be modulated transmitted by the beam splitter and a plurality of holograms generated by a host computer, modulating the laser light to be modulated based on each hologram, and outputting a plurality of modulated light beams to the beam splitter; A 4f imaging system, used for receiving a plurality of modulated light beams reflected by the beam splitter, filtering the plurality of modulated light beams, and superimposing the filtered light beams to obtain a partially coherent self-repairing light beam; The host computer includes: A function construction module, used for constructing a cross spectral density function of the partially coherent light beam in the spectrum plane based on the Schermer correlation function and the amplitude function of the partially coherent light beam in the spectrum plane; A function conversion module, for constructing a cross spectral density function of the partially coherent light beam in a source plane based on the cross spectral density function and the kernel function of the frequency spectrum plane; and converting the cross spectral density function of the source plane into an ensemble average function of the partially coherent light beam field; A field realization function acquisition module, used for obtaining a field realization function of the partially coherent beam based on the cross spectral density function of the source plane and the ensemble average function of the partially coherent beam field; An output field acquisition module is used to generate a plurality of random complex fields whose coherence functions in the frequency domain satisfy the Shermo correlation function, and input the plurality of random complex fields into the field realization function respectively to obtain a plurality of output fields; A hologram generation module, used for respectively encoding the multiple output fields to generate multiple holograms, and loading the multiple holograms into the spatial light modulator; The helium-neon laser, the polarizer, the beam expander, the beam splitter and the spatial light modulator form a coaxial system, and the reflection surface of the beam splitter is coaxially arranged with the 4f imaging system.

[0015] Preferably, the 4f imaging system comprises: a first thin lens, used for receiving a plurality of modulated light beams reflected by the beam splitter and focusing the plurality of modulated light beams; A pinhole stop is arranged at the rear focal plane of the first thin lens and is used to filter and obtain a first-order diffraction spot in the light beam emitted by the first thin lens; The second thin lens is arranged on the side of the pinhole aperture away from the first thin lens, and is used to focus the light beam emitted by the pinhole aperture to obtain a partially coherent self-repairing light beam.

[0016] Preferably, it also includes: A third thin lens is arranged on a side of the 4f imaging system away from the beam splitter, and is used to focus the partially coherent self-repairing beam onto a charge coupled device; A charge coupler is arranged on the side of the third thin lens away from the 4f imaging system, and its output end is connected to the host computer, and is used to capture the intensity map of the partially coherent self-repairing light beam and transmit the intensity map to the host computer, so that the host computer can obtain the far-field intensity distribution function of the partially coherent self-repairing light beam based on the intensity map.

[0017] The method for generating a partially coherent self-repairing light beam based on spectral modulation provided in the present application is based on the Schermer correlation function and the amplitude function of the partially coherent light beam to construct a cross-spectral density function of the partially coherent light beam on the spectrum plane. Since the Schermer correlation function constrains that the correlation between any two points in the light beam is only related to the relative positions of the two points, in the cross-spectral density function of the spectrum plane constructed based on the Schermer correlation function, the coherence of any two points in the partially coherent light beam on the spectrum plane always satisfies the Schermer correlation function, so that when the light beam is blocked, this coherence can be used to repair the blocked part. At the same time, the amplitude of different frequency components in the light beam can be changed by regulating the amplitude function, thereby changing the light intensity contribution of these frequency components after propagating to the spatial domain, that is, realizing the regulation of the light intensity distribution; then, the cross-spectral density function of the light source plane is constructed based on the cross-spectral density function and the kernel function of the spectrum plane. Since the partially coherent light The intensity distribution of the beam on the light source surface is the Fourier transform of the correlation structure in the cross spectral density function of the spectrum surface. The correlation structure of any two points in the partially coherent light beam on the light source surface is the Fourier transform of the amplitude function in the cross spectral density function of the spectrum surface. Therefore, by adjusting the correlation function and the amplitude function in the cross spectral density function of the light beam on the spectrum surface, the intensity distribution of the partially coherent light beam on the light source surface and the coherence of any two points in the light beam can be controlled, thereby giving the light beam intensity distribution controllable and self-repairing characteristics; finally, the field realization function is obtained based on the cross spectral density function of the light source surface, and the field intensity and phase information of the light beam at different spatial positions are determined by using the field realization function, and the characteristics of the light beam on the spectrum surface are reflected in the spatial domain, thereby generating multiple holograms for modulating the laser on the basis of the field realization function, and modulating the laser to be modulated based on multiple holograms according to the mode superposition principle to obtain a partially coherent self-repairing light beam. The present application changes the distribution characteristics of the light beam in the spatial frequency domain so that the light beam maintains coherence under various light intensity distribution conditions, thereby obtaining a partially coherent self-repairing light beam with adjustable light intensity distribution. At the same time, it avoids the problem that changing the phase distribution of the partially coherent light beam in the source plane causes the light intensity distribution of the light beam to change during the propagation process, resulting in inconsistency between the light intensity distribution in the far field and the light intensity distribution at the source plane, thereby improving the stability of the light intensity distribution.

[0018] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein: Figure 1A flow chart of a method for generating a partially coherent self-repairing light beam based on spectrum modulation provided in this application; Figure 2 A schematic diagram of the structure of a device for generating a partially coherent self-repairing light beam based on spectrum modulation provided in the present application; Explanation of the reference numerals in the specification: 1. Helium-neon laser; 2. Polarizer; 3. Beam expander; 4. Beam splitter; 5. Spatial light modulator; 6. 4f imaging system; 61. First thin lens; 62. Pinhole aperture; 63. Second thin lens; 7. Host computer; 8. Third thin lens; 9. Charge coupled device; 10. Fan-shaped opaque obstacle. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0020] The study of the self-repair phenomenon of beams is caused by the study of non-diffraction beams. Bessel beams are typical non-diffraction beams. Their lateral distribution is infinite and they carry infinite energy. Therefore, such beams cannot be produced experimentally. Bessel beams truncated by Gaussian distribution are called quasi-Bessel beams or Bessel-Gaussian beams, which maintain self-repair and non-diffraction transmission characteristics over a certain transmission distance. Although self-repair is one of the significant characteristics of non-diffraction beams, not all self-repairing beams are non-diffraction. Even some diffraction coherent beams have self-repair properties, such as optical ring lattices, Piercy beams, tightly focused and radially polarized Bessel-Gaussian beams. However, the self-repair ability of fully coherent self-repairing beams depends on the special light intensity distribution. In many cases, such beams are very sensitive to the size, shape and distribution of obstacles.

[0021] Optical coherence theory analyzes the correlation between two points in the electric field in the time domain or space domain. Spatial optical coherence is usually characterized by the degree of coherence (DOC) function, which is a second-order correlation function between two points in the spatial field. In 2007 and 2009, Gori et al. proposed the necessary and sufficient conditions for generating arbitrary scalar and vector real partially coherent beams, respectively. Their research results triggered a series of papers on the construction of partially coherent beams with special correlation structures. As a new degree of freedom, the DOC function can accurately control the transmission characteristics of the beam, reduce the negative effects caused by turbulence in complex environments, and control the interaction between light and matter. At the same time, the latest research shows that partially coherent beams also have self-repairing phenomena.

[0022] Based on this research, the prior art began to modulate the partially coherent light beam in the spatial domain to give it self-repairing properties and obtain a partially coherent self-repairing light beam. However, the light intensity distribution of the partially coherent self-repairing light beam repaired in the focal plane after being blocked is the same as the light intensity distribution in the focal plane when not blocked, but different from the light intensity distribution on the light source surface, which means that the light intensity stability of the light beam during propagation is poor, and the light intensity distribution of this type of partially coherent self-repairing light beam is specific and cannot be arbitrarily adjusted. Therefore, the present application regulates the partially coherent light beam in the spatial frequency domain, thereby generating a partially coherent self-repairing light beam with adjustable light intensity distribution in the source plane and unchanged light intensity distribution in the source plane and the far field.

[0023] See also Figure 1 , Figure 1 The flowchart of the method for generating a partially coherent self-repairing light beam based on spectrum modulation provided by the present application is shown, and the method specifically includes: S10: constructing a cross spectral density function of the partially coherent beam in the spectrum plane based on the Schermer correlation function and the amplitude function of the partially coherent beam in the spectrum plane; S20: constructing a cross spectral density function of a partially coherent beam in a source plane based on the cross spectral density function and the kernel function of the spectrum plane; and converting the cross spectral density function of the source plane into an ensemble average function of the partially coherent beam field; S30: obtaining a field realization function of the partially coherent beam based on the cross spectral density function of the source plane and the ensemble average function of the partially coherent beam field; S40: generating a plurality of random complex fields whose coherence functions in the frequency domain satisfy the Shermo correlation function, and inputting the plurality of random complex fields into the field realization function respectively to obtain a plurality of output fields; S50: encoding the multiple output fields respectively to generate multiple holograms, modulating the laser to be modulated based on each hologram to obtain multiple modulated light beams, and superimposing the multiple modulated light beams to obtain a partially coherent self-repairing light beam.

[0024] Specifically, since the second-order statistical characteristics of the coherent light field of the scalar part can be described by the cross spectral density function (CSD), and the partially coherent light beam of the present application is a type of scalar partially coherent light beam, the present application characterizes the second-order statistical characteristics of the light beam by constructing the cross spectral density function of the partially coherent light beam. At the same time, since the plane reached by the partially coherent light beam after passing through a convex lens (i.e., after a Fourier transform), is the spatial frequency plane (i.e., the spectrum plane), and the statistical characteristics of the light beam on the spectrum plane can be characterized by the correlation structure of the spectrum plane, and this correlation structure is related to the light intensity distribution of the light beam on the light source plane, the present application first constructs the cross spectral density function of the partially coherent light beam on the spectrum plane to characterize the statistical characteristics of the partially coherent light beam on the spectrum plane.

[0025] Furthermore, in the prior art, the Dirac correlation function is usually used when constructing the cross-spectral density function of the light beam on the spectrum plane, that is, , it can be seen from the formula that in the cross-spectral density function, any two points in the partially coherent beam are incoherent on the spectrum plane, which makes it impossible for the beam to self-repair based on the coherence between different frequency points when it is blocked.

[0026] Based on the above reasons, the present application introduces the coherence of the cross spectral density function of the spectrum plane as a new degree of freedom, and assumes that the cross spectral density function of the partially coherent light beam in the spectrum plane is a quasi-homogeneous field.

[0027] Specifically, the present application uses the Scherrer correlation function and the amplitude function of the partially coherent light beam to construct the cross spectral density function of the partially coherent light beam in the spectrum plane. The cross spectral density function of the spectrum plane is expressed as: , in, Represents the cross spectral density function of the spectrum surface; , Represents the vector coordinates of any two points in the partially coherent beam in the spatial frequency domain; Represents the amplitude function of the spectrum surface; represents the Shermo correlation function.

[0028] Since the Schermer correlation function constrains the correlation between any two points in a light beam to be only related to the relative positions of the two points, in the cross-spectral density function of the spectrum surface constructed based on the Schermer correlation function, the coherence between any two points in a partially coherent light beam on the spectrum surface always satisfies the Schermer correlation function, so that when the light beam is blocked, this coherence can be used to repair the blocked part. At the same time, the amplitude of different frequency components in the light beam can be changed by adjusting the amplitude function, thereby changing the light intensity contribution of these frequency components after propagating to the spatial domain, that is, realizing the regulation of the light intensity distribution.

[0029] Furthermore, in this application, it is assumed that the kernel function is expressed in the form of a Fourier transform integral kernel, that is: , , Based on the cross spectral density function and kernel function of the above spectrum plane, the cross spectral density function of the partially coherent beam in the source plane is expressed as: , in, represents the cross spectral density function of the source plane; Represents the cross spectral density function of the spectrum surface; , Represents the vector coordinates of any two points in the partially coherent beam in the spatial frequency domain; Represents the amplitude function of the spectrum surface; represents the Shermo correlation function; , Represents the vector coordinates of any two points in the partially coherent beam in the spatial domain; represents the kernel function; denotes conjugation; represents Fourier transform; , .

[0030] The cross spectral density function of the above-mentioned source plane can characterize the second-order statistical characteristics of the partially coherent light beam. It can be seen from the function that the intensity distribution of the partially coherent light beam on the light source plane is the Fourier transform of the correlation structure in the cross spectral density function of the frequency spectrum plane, and the correlation structure between any two points in the partially coherent light beam on the light source plane is the Fourier transform of the amplitude function in the cross spectral density function of the frequency spectrum plane. Therefore, by controlling the correlation function and amplitude function in the cross spectral density function of the light beam on the frequency spectrum plane, the intensity distribution of the partially coherent light beam on the light source plane and the coherence of any two points in the light beam can be controlled, thereby giving the light beam self-repairing characteristics.

[0031] In order to generate a partially coherent self-repairing beam with the above-mentioned characteristics, it is necessary to design a corresponding computer-generated hologram. By loading the computer-generated hologram onto a spatial light modulator, the spatial light modulator is used to modulate the laser to be modulated, thereby obtaining a partially coherent self-repairing beam with adjustable light intensity distribution and high light intensity stability.

[0032] Specifically, the cross-spectral density function of the source plane is first converted into the ensemble average function of the partially coherent beam field, which is specifically expressed as: , in, represents the ensemble average function of the partially coherent beam field; , Represents the vector coordinates of any two points in the partially coherent beam in the spatial domain; Represents a field realization function; Indicates conjugation.

[0033] By comparing the ensemble average function of the above-mentioned partially coherent beam field and the cross spectral density function of the source plane, the field realization function of the partially coherent beam can be obtained. The field realization function is used to determine the field intensity and phase information of the beam at different spatial positions, and the characteristics of the beam on the spectrum plane are reflected in the spatial domain. Therefore, multiple complex light field patterns can be generated based on the field realization function, and the self-repair performance of the beam can be realized based on these light field patterns.

[0034] Specifically, the field realization function is expressed as: , in, Represents a field realization function; Represents the vector coordinates of any point in the partially coherent beam in the spatial domain; Indicates random replay; Represents the vector coordinates of any point in the partially coherent beam in the spatial frequency domain; Represents the amplitude function of the spectrum surface.

[0035] Furthermore, by generating multiple random complex fields whose coherence functions in the frequency domain satisfy the Shermo correlation function, that is, the correlation structure of the random complex field in the frequency domain satisfies the equation: , multiple random complex fields are respectively input into the field realization function to obtain multiple output fields, each output field represents a light field mode of the final generated light beam, and a partially coherent light beam that conforms to the randomness of the partially coherent light beam can be obtained by superimposing multiple output fields. At the same time, since each random complex field satisfies the Scherrer correlation function, each output field has coherence, so that the partially coherent light beam finally superimposed has self-repairing properties, that is, a partially coherent self-repairing light beam is generated.

[0036] Specifically, in some embodiments of the present application, generating a plurality of random complex fields satisfying the Shermo correlation function includes: Use the randn function of MATLAB to generate multiple Gaussian random numbers with zero mean and unit variance.

[0037] For example, the Gaussian random number can be expressed as randn+i*randn.

[0038] Perform Fourier transform on the Shermo correlation function to obtain the target Shermo correlation function.

[0039] The product of each Gaussian random number and the square root of the target Shermo correlation function is calculated respectively, and the product is Fourier transformed to obtain multiple random complex fields that satisfy the Shermo correlation function.

[0040] Furthermore, since each output field corresponds to a light field mode, a hologram can be generated based on each output field encoding. It is worth noting that the generation of a hologram by output field encoding can be achieved by existing technologies.

[0041] For the multiple holograms generated, an animation is generated in a random order and loaded onto a spatial light modulator, which is then used to modulate the modulated laser based on each hologram. A partially coherent self-repairing beam can be obtained by superimposing the modulated light beams diffracted from each modulation.

[0042] Optionally, after obtaining the multiple output fields, the method further includes: superimposing the multiple output fields according to the mode superposition principle to obtain the far-field light intensity distribution function of the partially coherent self-repairing light beam.

[0043] Specifically, the far-field intensity distribution function of the partially coherent self-repairing beam is expressed as: , in, Represents the far-field intensity distribution function of the partially coherent self-repairing beam; Indicates the number of output fields; Indicates Output fields; Represents the vector coordinates of the partially coherent beam in the far-field plane of the spatial domain; Indicates conjugation.

[0044] The present application also provides a device for generating a partially coherent self-repairing light beam based on spectrum modulation, which is used to implement the method for generating a partially coherent self-repairing light beam based on spectrum modulation provided in the above embodiment, such as Figure 2 As shown, the device specifically includes: a helium-neon laser 1, a polarizer 2, a beam expander 3, a beam splitter 4, a spatial light modulator 5, a 4f imaging system 6 and a host computer 7.

[0045] The HeNe laser 1 is used to generate laser light to be modulated.

[0046] In a specific example of the present application, the HeNe laser 1 emits a laser to be modulated with a wavelength of 632.8 nm.

[0047] The polarizer 2 is used to modulate the polarization direction of the laser light to be modulated into horizontal polarization.

[0048] Specifically, since the spatial light modulator 5 can only respond to horizontally polarized light beams, a polarizer 2 is set on the output surface of the helium-neon laser 1 to adjust the polarization direction of the laser to be modulated to horizontal polarization, thereby matching the response direction of the spatial light modulator 5 .

[0049] The beam expander 3 is used to expand and collimate the laser light to be modulated emitted from the polarizer 2 .

[0050] Specifically, the modulated laser is expanded and collimated so that the waist width of the light beam can be accurately controlled subsequently.

[0051] The beam splitter 4 is used to transmit the laser light to be modulated emitted by the beam expander 3 to the spatial light modulator 5, receive a plurality of modulated light beams output by the spatial light modulator 5, and reflect the plurality of modulated light beams.

[0052] The spatial light modulator 5 is used to receive the laser light to be modulated transmitted by the beam splitter 4 and the multiple holograms generated by the host computer 7 , and modulate the laser light to be modulated based on each hologram, and output multiple modulated light beams to the beam splitter 4 .

[0053] The 4f imaging system 6 is used to receive the multiple modulated light beams reflected by the beam splitter 4, filter the multiple modulated light beams, and superimpose the filtered light beams to obtain a partially coherent self-repairing light beam.

[0054] The host computer 7 specifically includes: A function construction module, used for constructing a cross spectral density function of a partially coherent light beam in a spectral plane based on a Schermer correlation function and an amplitude function of the partially coherent light beam in a spectral plane; A function conversion module is used to construct a cross spectral density function of a partially coherent beam in a source plane based on a cross spectral density function and a kernel function of a spectrum plane; and to convert the cross spectral density function of the source plane into an ensemble average function of a partially coherent beam field; A field realization function acquisition module, used for obtaining a field realization function of a partially coherent beam based on a cross spectral density function of a source plane and an ensemble average function of a partially coherent beam field; An output field acquisition module is used to generate multiple random complex fields whose coherence functions in the frequency domain satisfy the Shermo correlation function, and input the multiple random complex fields into the field realization function respectively to obtain multiple output fields; A hologram generation module, used for respectively encoding a plurality of output fields to generate a plurality of holograms, and loading the plurality of holograms into the spatial light modulator; The helium-neon laser 1 , the polarizer 2 , the beam expander 3 , the beam splitter 4 and the spatial light modulator 5 form a coaxial system, and the reflection surface of the beam splitter 4 is coaxially arranged with the 4f imaging system 6 .

[0055] Furthermore, the 4f imaging system 6 includes a first thin lens 61 , a pinhole stop 62 and a second thin lens 63 .

[0056] The first thin lens 61 is used to receive the multiple modulated light beams reflected by the beam splitter 4 and focus the multiple modulated light beams.

[0057] The pinhole stop 62 is disposed on the rear focal plane of the first thin lens 61 , and is used to filter and obtain the first-order diffraction spot in the light beam emitted from the first thin lens 61 .

[0058] Specifically, the pinhole aperture 62 can eliminate the stray light in the light beam emitted by the first thin lens 61 and only retain the first-order diffraction spot in the light beam.

[0059] The second thin lens 63 is disposed on the side of the pinhole aperture 62 away from the first thin lens 61 and is used to focus the light beam emitted from the pinhole aperture 62 to obtain a partially coherent self-repairing light beam.

[0060] By way of example, the focal lengths of the first thin lens 61 and the second thin lens 63 are f=25 cm.

[0061] The 4f imaging system 6 provided in the present application is intended to obtain a first-order diffraction spot, because spots of different orders cannot be separated directly after the spatial light modulator 5 .

[0062] In some embodiments of the present application, the device further includes: a third thin lens 8 and a charge coupler 9 .

[0063] The third thin lens 8 is arranged on the side of the 4f imaging system 6 away from the beam splitter 4, and is used to focus the partially coherent self-repairing light beam onto the charge coupler 9.

[0064] The charge coupler 9 is arranged on the side of the third thin lens 8 away from the 4f imaging system 6, and its output end is connected to the host computer 7 for capturing the intensity map of the partially coherent self-repairing light beam and transmitting the intensity map to the host computer 7 so that the host computer 7 can average the intensity map to obtain the far-field intensity distribution function of the partially coherent self-repairing light beam.

[0065] Optionally, in order to verify the self-repairing properties of the generated partially coherent self-repairing light beam, the embodiment of the present application also places a fan-shaped opaque obstacle 10 on the light source surface (i.e., the side of the 4f imaging system 6 away from the beam splitter 4), and the blocked partially coherent self-repairing light beam is focused by the third thin lens 8 and then the charge coupled device 9 takes a light intensity image, and then the host computer 7 obtains the far-field light intensity distribution of the partially coherent self-repairing light beam after being blocked.

[0066] Through comparison, it is found that the partially coherent self-repairing light beam generated by the present application has a strong self-repairing ability. In the presence of an obstacle, if the spatial coherence area of ​​the partially coherent self-repairing light beam is much smaller than the area of ​​the obstacle, the partially coherent self-repairing light beam can restore its light intensity distribution in the far field, because the far-field light intensity distribution is related to the associated structure of the light source surface; if the obstacle is not enough to destroy the associated structure of the light source surface, it is not enough to destroy the light intensity distribution of the partially coherent light beam in the far field; even if the light intensity on the light source surface is largely blocked by the obstacle, its light intensity distribution can still be restored in the far field; and, when the size of the obstacle is constant, the low-coherence light beam has a smaller coherence area and is easier to restore its light intensity distribution in the far field. Therefore, the self-repairing ability of the light beam can be further improved by reducing the coherence of the partially coherent self-repairing light beam.

[0067] The device for generating a partially coherent self-repairing light beam based on spectrum modulation provided in the present application does not require complicated optical path settings, nor does it require precise optical path calibration. The device is simple and easy to operate, and the intensity distribution of the generated partially coherent self-repairing light beam can be arbitrarily controlled. At the same time, the light intensity distribution has high stability, and has important applications in optical imaging, optical capture, and information transmission through random media.

[0068] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0069] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0070] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0071] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0072] Obviously, the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for generating a partially coherent self-repairing beam based on spectrum modulation, characterized in that: include: Based on the Schermer correlation function and the amplitude function of the partially coherent light beam in the spectrum plane, constructing the cross spectral density function of the partially coherent light beam in the spectrum plane; Based on the cross spectral density function and the kernel function of the frequency spectrum plane, construct the cross spectral density function of the partially coherent light beam in the source plane; convert the cross spectral density function of the source plane into an ensemble average function of the partially coherent light beam field; Obtaining a field realization function of the partially coherent light beam based on a cross spectral density function of the source plane and an ensemble average function of the partially coherent light beam field; Generate a plurality of random complex fields whose coherence functions in the frequency domain satisfy the Shermo correlation function, and input the plurality of random complex fields into the field realization function respectively to obtain a plurality of output fields; The multiple output fields are respectively encoded to generate multiple holograms, and the laser to be modulated is modulated based on each hologram to obtain multiple modulated light beams, and the multiple modulated light beams are superimposed to obtain a partially coherent self-repairing light beam.

2. The method for generating a partially coherent self-repairing light beam based on spectrum modulation according to claim 1, characterized in that: The cross spectral density function of the spectrum surface is expressed as: ， in, Represents the cross spectral density function of the spectrum surface; , Represents the vector coordinates of any two points in the partially coherent beam in the spatial frequency domain; Represents the amplitude function of the spectrum surface; represents the Shermo correlation function.

3. The method for generating a partially coherent self-repairing light beam based on spectrum modulation according to claim 1, characterized in that: The cross spectral density function of the source plane is expressed as: ， ， ， in, represents the cross spectral density function of the source plane; Represents the cross spectral density function of the spectrum surface; , Represents the vector coordinates of any two points in the partially coherent beam in the spatial frequency domain; Represents the amplitude function of the spectrum surface; represents the Shermo correlation function; , Represents the vector coordinates of any two points in the partially coherent beam in the spatial domain; represents the kernel function; denotes conjugation; represents Fourier transform; , ; The ensemble average function of the partially coherent beam field is expressed as: ， in, represents the ensemble average function of the partially coherent beam field; , Represents the vector coordinates of any two points in the partially coherent beam in the spatial domain; Represents a field realization function; Indicates conjugation.

4. The method for generating a partially coherent self-repairing light beam based on spectrum modulation according to claim 1, characterized in that: The field realization function is expressed as: ， in, Represents a field realization function; Represents the vector coordinates of any point in the partially coherent beam in the spatial domain; Indicates random replay; Represents the vector coordinates of any point in the partially coherent beam in the spatial frequency domain; Represents the amplitude function of the spectrum surface.

5. The method for generating a partially coherent self-repairing light beam based on spectrum modulation according to claim 1, characterized in that: Generating multiple random complex fields that satisfy the Shermo correlation function includes: Use MATLAB's randn function to generate multiple Gaussian random numbers with zero mean and unit variance; Performing Fourier transform on the Shermo correlation function to obtain a target Shermo correlation function; The product of each of the Gaussian random numbers and the square root of the target Shermo correlation function is calculated respectively, and the product is Fourier transformed to obtain a plurality of random complex fields satisfying the Shermo correlation function.

6. The method for generating a partially coherent self-repairing light beam based on spectrum modulation according to claim 1, characterized in that: After obtaining the multiple output fields, the method further includes: superimposing the multiple output fields according to the mode superposition principle to obtain the far-field light intensity distribution function of the partially coherent self-repairing light beam.

7. The method for generating a partially coherent self-repairing light beam based on spectrum modulation according to claim 6, characterized in that: The far-field intensity distribution function of the partially coherent self-repairing beam is expressed as: ， in, Represents the far-field intensity distribution function of the partially coherent self-repairing beam; Indicates the number of output fields; Indicates Output fields; Represents the vector coordinates of the partially coherent beam in the far-field plane of the spatial domain; Indicates conjugation.

8. A device for generating a partially coherent self-repairing light beam based on spectrum modulation, characterized in that: The method for generating a partially coherent self-repairing light beam based on spectrum modulation according to any one of claims 1 to 7 comprises: Helium-neon laser, used to generate laser light to be modulated; A polarizer, used for modulating the polarization direction of the laser to be modulated into horizontal polarization; A beam expander, used for expanding and collimating the laser light to be modulated emitted from the polarizer; A beam splitter, used for transmitting the laser light to be modulated emitted by the beam expander to the spatial light modulator, receiving a plurality of modulated light beams output by the spatial light modulator, and reflecting the plurality of modulated light beams; A spatial light modulator, used for receiving the laser light to be modulated transmitted by the beam splitter and a plurality of holograms generated by a host computer, modulating the laser light to be modulated based on each hologram, and outputting a plurality of modulated light beams to the beam splitter; A 4f imaging system, used for receiving a plurality of modulated light beams reflected by the beam splitter, filtering the plurality of modulated light beams, and superimposing the filtered light beams to obtain a partially coherent self-repairing light beam; The host computer includes: A function construction module, used for constructing a cross spectral density function of the partially coherent light beam in the spectrum plane based on the Schermer correlation function and the amplitude function of the partially coherent light beam in the spectrum plane; A function conversion module, for constructing a cross spectral density function of the partially coherent light beam in a source plane based on the cross spectral density function and the kernel function of the frequency spectrum plane; and converting the cross spectral density function of the source plane into an ensemble average function of the partially coherent light beam field; A field realization function acquisition module, used for obtaining a field realization function of the partially coherent beam based on the cross spectral density function of the source plane and the ensemble average function of the partially coherent beam field; An output field acquisition module is used to generate a plurality of random complex fields whose coherence functions in the frequency domain satisfy the Shermo correlation function, and input the plurality of random complex fields into the field realization function respectively to obtain a plurality of output fields; A hologram generation module, used for respectively encoding the multiple output fields to generate multiple holograms, and loading the multiple holograms into the spatial light modulator; The helium-neon laser, the polarizer, the beam expander, the beam splitter and the spatial light modulator form a coaxial system, and the reflection surface of the beam splitter is coaxially arranged with the 4f imaging system.

9. The device for generating a partially coherent self-repairing light beam based on spectrum modulation according to claim 8, characterized in that: The 4f imaging system comprises: a first thin lens, used for receiving a plurality of modulated light beams reflected by the beam splitter and focusing the plurality of modulated light beams; A pinhole stop is arranged at the rear focal plane of the first thin lens and is used to filter and obtain a first-order diffraction spot in the light beam emitted by the first thin lens; The second thin lens is arranged on the side of the pinhole aperture away from the first thin lens, and is used to focus the light beam emitted by the pinhole aperture to obtain a partially coherent self-repairing light beam.

10. The device for generating a partially coherent self-repairing light beam based on spectrum modulation according to claim 8, characterized in that: Also includes: A third thin lens is arranged on a side of the 4f imaging system away from the beam splitter, and is used to focus the partially coherent self-repairing beam onto a charge coupled device; A charge coupler is arranged on the side of the third thin lens away from the 4f imaging system, and its output end is connected to the host computer, and is used to capture the intensity map of the partially coherent self-repairing light beam and transmit the intensity map to the host computer, so that the host computer can obtain the far-field intensity distribution function of the partially coherent self-repairing light beam based on the intensity map.

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