Device and method for controlling multi-degree-of-freedom of three-dimensional spatial light field through scattering medium

Abstract

The application discloses a device and method for regulating multi-degree-of-freedom information of a three-dimensional space light field through a scattering medium, and is characterized in that a three-dimensional polarization transmission matrix is accurately measured through a coaxial interference method, the complex amplitude information of a single linearly polarized incident field is regulated to regulate the amplitude, phase and polarization information of a three-dimensional space light field through the scattering medium, and thus the regulation of the light field information from few to multi-degree-of-freedom through the scattering medium is realized. The application solves the problems that the current wavefront regulation technology can only realize the regulation of single-degree-of-freedom information such as light focusing and polarized light focusing through the scattering medium, and the regulation of multi-degree-of-freedom information of an outgoing field can be realized only by simultaneously regulating the amplitude, phase and polarization information of an incident field, and thus has a wide application prospect in a complex scattering environment, and can be applied to in-vivo deep tissue cell light manipulation, scattering optical imaging, scattering environment optical communication and the like.

Description

Technical Field

[0001] This invention belongs to the field of novel optical field manipulation technology in scattering environment. Specifically, it is a device and method for manipulating multi-degree-of-freedom information of three-dimensional spatial optical field through scattering medium. It is used to solve and overcome optical scattering problems in complex environments and can be used for optical manipulation of living tissue cells, scattering optical imaging, scattering environment optical communication, etc. Background Technology

[0002] Novel structured light fields are currently a research frontier and hot topic in the field of optics. They refer to a class of light fields with special spatial structures and polarization distributions. Novel structured light fields have significant application value in optical micromanipulation, optical communication, and biomedical super-resolution imaging. However, unlike transparent and homogeneous materials, light undergoes multiple scatterings when propagating through scattering media such as biological tissues, disturbed atmospheres, and turbid liquids. Multiple scattering disrupts the three-dimensional spatial structure and polarization distribution of the light field, resulting in a three-dimensional speckle light field with random intensity and polarization distribution after passing through the scattering medium. Therefore, multiple scattering destroys the spatial structure and polarization distribution of structured light fields. This optical scattering phenomenon significantly limits technologies such as optical micromanipulation, optical communication, and biomedical super-resolution imaging. In particular, it greatly limits the cell capture depth of optical tweezers in vivo, hindering biomedical scientists from further in-depth research into the cellular characteristics and biological phenomena of deep tissues. Therefore, effectively solving and overcoming the optical scattering problem in scattering media will greatly broaden the application prospects of novel structured light fields.

[0003] Wavefront manipulation of scattering media provides an effective way to solve optical scattering problems. By using spatial light modulators or digital microlens arrays to modulate the wavefront of incident light, the multiple scattering of light caused by the scattering medium itself is canceled, thus achieving the goal of controlling the generation of a target light field through the scattering medium. Currently, wavefront manipulation techniques for complex media mainly include iterative optimization algorithms, optical phase conjugation methods, and transfer matrix methods. Iterative optimization algorithms use speckle intensity information collected by cameras or other detectors as feedback signals, and use iterative optimization algorithms, such as genetic algorithms, to gradually optimize the wavefront distribution of the input light field, thereby controlling the target light field through the scattering medium. However, when the target output light field is changed, the above iterative optimization process needs to be repeated, making this method very time-consuming and inconvenient. The optical phase conjugation method records the amplitude and phase information of the scattered light field, and then generates a phase-conjugated light field in reverse. The modulated light field passes through the scattering medium along the original light path, thereby controlling the generation of the target light field.

[0004] However, the optical phase conjugation method is significantly affected by environmental noise and requires the pre-generation of a target light field at the target location as a guide, which is impractical in real-world applications. The transfer matrix method, on the other hand, quantitatively describes the relationship between the emitted and incident light fields using the transfer matrix. In practice, it only requires measuring the transfer matrix of the scattering system, combining it with the target output light field, and obtaining the wavefront information distribution of the incident light field through matrix operations. Furthermore, by manipulating the wavefront information of the incident light field, the target light field can be controlled through the scattering medium. Once the transfer matrix of the scattering system is measured, arbitrary target light field information can be dynamically controlled.

[0005] Most iterative optimization algorithms can only achieve three-dimensional spatial light focusing and three-dimensional polarized light focusing through scattering media. The transfer matrix method, by manipulating the amplitude and phase information of the incident light field, can simultaneously control the amplitude and phase of the output light field through the scattering medium. Furthermore, extending the transfer matrix method to the vector transfer matrix method, by constructing two optical systems to simultaneously control the amplitude and phase distribution of the incident light field in two orthogonal polarization directions, it achieves simultaneous control of the amplitude, phase, and polarization distribution of the output light field through the scattering medium. This method requires strict alignment of the information in the two orthogonal polarization dimensions of the incident light field, resulting in a complex and expensive system setup with high stability requirements.

[0006] Currently, wavefront manipulation techniques in complex media have not yet achieved simultaneous manipulation of multi-degree-of-freedom information across multiple planes in three-dimensional space through scattering media. In practical applications, manipulating only the multi-degree-of-freedom information of a single-plane optical field or the single-degree-of-freedom information of multiple planes cannot meet the needs of practical applications. Therefore, the limitation of wavefront manipulation techniques based on scattering media, which only manipulate the multi-degree-of-freedom information of a single-plane optical field or the single-degree-of-freedom information of multiple planes, to some extent restricts the application of novel structured optical fields in scattering environments. Summary of the Invention

[0007] The present invention addresses the shortcomings of existing technologies and methods by proposing a device and method for controlling a three-dimensional spatial light field with multiple degrees of freedom through a scattering medium. This aims to enable the control of light field information in a scattering environment from few to many degrees of freedom, thereby significantly improving the controllability of light field control through a scattering medium. This invention can be used to solve and overcome optical scattering problems in complex environments and can be further applied to in vivo deep tissue cell light manipulation, scattering optical imaging, and scattering environment light communication.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: The present invention provides a multi-degree-of-freedom device for controlling a three-dimensional spatial light field through a scattering medium, comprising: a laser source system, a collimation and beam expansion system, a laser power and polarization direction control system, a mirror device, an input light field complex amplitude control device, a light scattering system, a signal detection device, and a main control computer system. The laser source system is a He-Ne laser, used to emit coherent laser light. The collimation and beam expansion system consists of two lenses with different focal lengths, used to collimate and expand the laser source to obtain a collimated laser beam, which is then input into the laser power and polarization direction control system. The laser power and polarization direction control system consists of a first half-wave plate, a polarizing beam splitter, a light-blocking plate, and a second half-wave plate. By changing the principal axis direction of the first half-wave plate, the collimated laser beam becomes vertically polarized light with continuously adjustable laser intensity after passing through the polarizing beam splitter. The polarizing beam splitter outputs a transmitted laser beam and a reflected laser beam, wherein the reflected laser beam is blocked by the light-blocking plate. By changing the principal axis direction of the second half-wave plate, the transmitted laser beam becomes linearly polarized light in any direction after passing through the second half-wave plate and illuminates the reflecting mirror device, thereby changing the transmission direction of the incident collimated laser beam so that the reflected laser beam can illuminate the effective target surface of the digital microlens array in the input light field complex amplitude control device at an incident angle of 24°. The main control computer system uses a computer to load a binarized hologram onto the digital microlens array and controls the digital microlens array according to the binarized hologram. This causes the light field after passing through the digital microlens array to pass sequentially through the third lens, the aperture, and the fourth lens in the light field complex amplitude modulation device. The +1 order beam corresponds to the complex amplitude distribution of the target modulated linear polarization light field. The aperture is used to filter the +1 order beam on the focal plane of the third lens, thereby obtaining the modulated laser beam. The computer controls the digital microlens array behind the fourth lens, and simultaneously modulates the signal light and reference light to measure any sub-matrix of the three-dimensional polarization transmission matrix of the light scattering system. By adjusting the complex amplitude distribution of the incident light field, the multi-degree-of-freedom information of the outgoing light field can be simultaneously controlled through the scattering medium. The light scattering system uses a scattering medium to simulate a strong scattering environment, thereby disturbing and coupling the amplitude, phase, and polarization information of the modulated laser beam to form a three-dimensional random speckle field distribution with random amplitude, phase, and polarization in three-dimensional space. The signal detection device consists of a linear polarizer, a camera, and a one-dimensional displacement stage, wherein the camera is fixed on the one-dimensional displacement stage. After passing through the linear polarizer, the three-dimensional random speckle field distribution is obtained as a three-dimensional random speckle field distribution in a single linear polarization direction of the target, and the speckle intensity information of the corresponding plane is acquired by the camera. By adjusting the front and rear positions of the one-dimensional displacement stage and the principal axis direction of the linear polarizer, the camera can acquire intensity information of the three-dimensional random speckle field in different planes and polarization directions and send it to the computer.

[0009] The present invention provides a method for controlling a three-dimensional spatial light field with multiple degrees of freedom through a scattering medium, characterized in that it is applied to the aforementioned device for controlling a three-dimensional spatial light field with multiple degrees of freedom through a scattering medium, and is performed according to the following steps: Step 1: Turn on the laser source system to emit a coherent laser source; Step 2: By changing the principal axis direction of the second half-wave plate in the optical power and polarization direction control system, the transmitted laser beam is changed after passing through the optical power and polarization direction control system. X A laser beam with linear polarization; Step 3: Turn on the digital microlens array in the input light field complex amplitude control device; Step 4: Simultaneously target the incident light using the digital microlens array. n A modulated signal light and reference light Modulation is performed, and the three-step phase shift is 0, / 2、 Superimposed on the first n A modulated signal light Then, sequentially compare with the reference light. After interference, the intensity information of the three speckle fields output through the scattering medium is obtained. , and ; Step 5: Measure the three-dimensional polarization transfer matrix using equation (1). any submatrix element t The n Column elements : (1) In equation (1), * denotes complex conjugate. , and These respectively indicate the absence of signal light. Under the premise that only the reference light Perform three-step phase shift 0, , Then, the intensity information of the three speckle fields output through the scattering medium after interfering with the reflected laser beam of the polarizing beam splitter in sequence; Step 6: Maintain the laser beam after passing through the optical power and polarization direction control system as follows: X With the linear polarization direction unchanged, the computer will be used to measure the three-dimensional polarization transfer matrix. any submatrix element t A series of binarized holograms are loaded and stored on the digital microlens array. By changing the principal axis direction of the polarizer and the position of the one-dimensional displacement stage, the computer controls the digital microlens array to dynamically switch the pre-loaded series of binarized holograms, thereby generating amplitude and phase distributions of different target incident light fields. The camera is then controlled to synchronously acquire speckle intensity information, sequentially measuring the... k a plane The corresponding above and Thus, a three-dimensional polarization transfer matrix based on light scattering can be constructed using equation (2). : (2) In equation (2), X Indicates the linear polarization direction of the incident light field. H and V These represent the two orthogonal polarization directions of the output light field transmitted through the scattering medium; Indicates the emitted light is H Linear polarization direction, incident light is X The first of the linear polarization directions k a plane The polarization transfer matrix, Indicates the emitted light is V Linear polarization direction, incident light is X The first of the linear polarization directions k a plane The polarization transfer matrix; ; K Indicates the total number of planes; T Represents the matrix transpose operation; Step 7: Define the three-dimensional spatial light field transmitted through the scattering medium. K Two orthogonal polarization directions on a plane H and V Target complex amplitude distribution ,in, and They represent the first k a plane The two orthogonal polarization directions H and V The complex amplitude distribution of the target light field; Step 8: Calculate the single element to be modulated using equation (3). XComplex amplitude distribution of linearly polarized incident light field : (3) In equation (3), Represents the transpose and conjugate operation of a matrix; Step 9: Calculate the incident light field of the target using the superpixel coding method. After the corresponding binarized hologram is generated, the main control computer loads the corresponding binarized hologram onto the digital microlens array in the input light field complex amplitude modulation device, thereby obtaining the amplitude, phase, and polarization distribution of the three-dimensional spatial light field generated through the scattering medium. This refers to the multi-degree-of-freedom information of the three-dimensional spatial light field modulated through the scattering medium, among which... and They represent the first k a plane The two orthogonal polarization directions H and V The complex amplitude distribution of the light field generated above.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Existing light field manipulation techniques using scattering media can only simultaneously control the amplitude, phase, and polarization distribution of a two-dimensional planar light field through the scattering medium. This invention utilizes the characteristic of multiple scattering of light to completely disrupt and couple the multi-degree-of-freedom information of light, and proposes a three-dimensional polarization transfer matrix method. Based on this method, it is possible to simultaneously control the amplitude, phase, and polarization distribution of different planes of a three-dimensional spatial light field through the scattering medium, thereby realizing the controllability of light field information from few to many degrees of freedom in the scattering environment, significantly improving the controllability of light field manipulation through the scattering medium.

[0011] 2. Existing light field manipulation techniques using scattering media rely on simultaneously controlling the amplitude, phase, and polarization distribution of the incident light field to simultaneously control the multi-degree-of-freedom information of the outgoing light field through the scattering medium. This invention only requires controlling the amplitude and phase distribution of any single linearly polarized incident light field to achieve multi-degree-of-freedom information manipulation of the three-dimensional spatial light field through the scattering medium. Compared with traditional light field manipulation systems using scattering media, it requires only half the optical instruments and equipment, and has a stronger light field manipulation capability through the scattering medium. It simplifies the device system for controlling multi-degree-of-freedom information of the light field through the scattering medium and reduces the system cost.

[0012] 3. Compared with the traditional method of measuring the transmission matrix by dual-path interferometry, the coaxial interferometry method used in this invention to measure the three-dimensional polarization transmission matrix is ​​simpler, has higher tolerance to environmental noise, does not rely on a complex optical system, and significantly improves the stability and robustness of the optical system.

[0013] 4. This invention improves the accuracy of coaxial interferometry in measuring the three-dimensional polarization transfer matrix by additionally measuring the amplitude and phase distribution of the reference light transmitted through the scattering system.

[0014] 5. This invention fully utilizes the digital microlens array with fast switching characteristics to simultaneously and accurately control the amplitude and phase distribution of the incident light field. Its maximum switching speed is >20 kHz, which significantly improves the speed of measuring the three-dimensional polarization transmission matrix of the scattering system and controlling the multi-degree-of-freedom information of the three-dimensional target light field through the scattering medium.

[0015] 6. Based on a digital microlens array with fast switching characteristics, the present invention has strong reconfigurability in controlling the three-dimensional spatial light field through the scattering medium, thereby ensuring that the amplitude, phase and polarization distribution of the three-dimensional spatial light field of any target can be dynamically controlled through the scattering medium. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the apparatus for controlling the amplitude, phase, and polarization distribution of a three-dimensional spatial light field in different planes through a scattering medium by regulating the amplitude and phase distribution of a single linearly polarized incident light field according to the present invention. Figure 2 This is a flowchart of the method of controlling the amplitude, phase and polarization distribution of a three-dimensional spatial light field in different planes through a scattering medium by regulating the amplitude and phase distribution of a single linearly polarized incident light field according to the present invention. Figure 3 This is a flowchart illustrating the measurement of the three-dimensional polarization transfer matrix based on the coaxial interferometry method used in this invention. Figure 4 This invention is based on Figure 2 A schematic diagram of a device for measuring the phase distribution of a reference light field and a target light field in two orthogonal polarization directions in different planes of three-dimensional space through a scattering medium; The numbers in the diagram are: 1-Laser source, 2-Lens, 3-Lens, 4-First half-wave plate, 5-Polarizing beam splitter, 6-Brightness shield, 7-First half-wave plate, 8-Reflector, 9-Digital microlens array, 10-Lens, 11-Pinhole, 12-Lens, 13-Scattering medium, 14-Polarizer, 15-Camera, 16-One-dimensional displacement stage, 17-Computer, 18-Reflector, 19-Half-wave plate, 20-Spatial light modulator, 21-Beam splitter, 22-Brightness shield. Detailed Implementation

[0017] The present invention will now be described in detail with reference to the accompanying drawings and embodiments: In this embodiment, the present invention proposes for the first time a method for controlling the amplitude, phase, and polarization distribution of a three-dimensional spatial light field in different planes through a scattering medium by adjusting the amplitude and phase distribution of a single linearly polarized incident light field. Compared with the traditional transfer matrix method, the three-dimensional polarization transfer matrix proposed in this invention quantitatively describes the relationship between the complex amplitude distribution of two orthogonal polarization directions in different planes of the scattering medium and the complex amplitude distribution of the incident light field in a single linear polarization direction. Based on the three-dimensional polarization transfer matrix method, by pre-measuring the transfer matrix related to the incident polarization direction in different planes of the scattering medium, and further combining the target complex amplitude distribution in the two orthogonal polarization directions of the light field in different planes of the scattering medium, the complex amplitude distribution of the corresponding linearly polarized incident light field to be controlled can be calculated according to complex matrix operations. Furthermore, by adjusting the complex amplitude distribution of the incident light field, the amplitude, phase, and polarization distribution of the generated three-dimensional spatial light field in different planes can be controlled through the scattering medium. Therefore, the present invention realizes the controllability of light field information in a scattering environment from few to many degrees of freedom, significantly improving the controllability of light field control through the scattering medium. Specifically, as... Figure 1 As shown, a device for controlling multi-degree-of-freedom information of a three-dimensional spatial light field through a scattering medium includes: a laser source-1, a lens-2, a lens-3, a first half-wave plate-4, a polarizing beam splitter-5, a light-blocking plate-6, a second half-wave plate-7, a reflector-8, a digital microlens array-9, a lens-10, a pinhole-11, a lens-12, a scattering medium-13, a polarizer-14, a camera-15, a one-dimensional displacement stage-16, and a computer-17; Laser source 1 is a He-Ne laser, used to emit a coherent laser source with a wavelength of 633 nm; The coherent laser source is collimated and expanded by a collimation and beam-expanding system consisting of lens 2 and lens 3 with focal lengths of 25.4 mm and 300 mm, respectively. The collimation and beam-expanding system is used to collimate and expand the spot diameter of the laser source into a collimated laser beam with a spot diameter of 20 mm. After the collimated laser beam passes through the first half-wave plate 4 and the polarizing beam splitter 5, the polarizing beam splitter 5 outputs a transmitted laser beam and a reflected laser beam. The reflected laser beam is blocked by the light-blocking plate 6. By changing the principal axis direction of the first half-wave plate 4, the transmitted laser beam becomes a vertical beam with continuously adjustable laser intensity after passing through the polarizing beam splitter 5. V The linearly polarized beam, the laser beam reflected by the polarizing beam splitter 5, will be used in the subsequent optical field phase measurement; vertical V After the linearly polarized beam passes through the second half-wave plate 7, the second half-wave plate 7, without sacrificing the laser beam power, continuously changes the polarization verticality by altering the principal axis direction of the second half-wave plate 7. V The linear polarization direction of a linearly polarized beam makes the verticalV After passing through the second half-wave plate 7, the linearly polarized beam becomes arbitrarily oriented. X Linearly polarized beams are intended to highlight that this invention does not require restriction on the linear polarization direction of the incident light field; V A linearly polarized beam of light shines onto mirror 8, which is used to change the incident light. X The propagation direction of the linearly polarized beam ensures that the laser beam reflected by the reflector 8 can illuminate the effective target surface of the digital microlens array 9 in the input optical field complex amplitude control device at an incident angle of 24°. The digital microlens array 9 is a binarized optical component. A computer 17, combined with a superpixel encoding algorithm, calculates a binarized hologram. The computer 17 then loads the binarized hologram onto the digital microlens array 9 and controls the digital microlens array 9 to modulate the incident light based on the binarized hologram. X Linearly polarized beam; the digital microlens array has 1024×768 pixels, a pixel size of 5.86 μm, and the beam area reflected by the digital microlens array is 6.0 mm × 4.5 mm. Modulated by digital microlens array 9 X A linearly polarized beam, after passing through lens 10, aperture 11 and lens 12 in sequence, has a light field with multiple diffraction orders. The beams corresponding to the ±1st order beams are all complex amplitude distributions of the target modulation light field. In this embodiment, the +1st order beam is used as the complex amplitude distribution of the target modulation light field during the experiment. The +1st order beam on the focal plane of lens 10 is filtered by aperture 11 to obtain the complex amplitude distribution of the target modulation beam. The digital microlens array 9 measures any sub-matrix of the three-dimensional polarization transfer matrix of the scattering system by simultaneously modulating the signal light and the reference light, and further achieves multi-degree-of-freedom information of the outgoing light field through the scattering medium by simultaneously controlling the complex amplitude distribution of the target incident beam. Lens 10 and lens 12 have focal lengths of 300 mm and 60 mm, respectively, which can further reduce the beam controlled by the digital microlens array 9. The area of ​​the target modulated incident beam after beam reduction is approximately 1.2 mm × 0.9 mm. The target modulated incident beam passes through the scattering medium 13, which is composed of an electrospun film. The scattering medium 13 is used to simulate a strong scattering environment, thereby completely disturbing and coupling the amplitude, phase and polarization information of the modulated laser beam to form a three-dimensional random speckle field distribution with random amplitude, phase and polarization in three-dimensional space. After passing through the linear polarizer 14, the three-dimensional random speckle field distribution is obtained in a single linear polarization direction of the target. The speckle intensity information of the corresponding plane of the three-dimensional random speckle field is collected by the camera 15 fixed on the one-dimensional displacement stage 16. The polarizer 14 is used to select the three-dimensional speckle field information of the three-dimensional random speckle field distribution in different polarization directions. By changing the front and rear positions of the one-dimensional displacement stage 16 and the principal axis direction of the linear polarizer 14, the camera 15 can collect the intensity information of the three-dimensional random speckle field in different planes and different polarization directions. The intensity information of the three-dimensional random speckle field in different planes and different polarization directions is sent to the computer 17 via the camera 15. The computer 17 is used to record the corresponding speckle intensity information, dynamically control the digital microlens array 9 to generate the amplitude and phase distribution of different target incident light fields, and trigger the camera 15 and the digital microlens array 9 to perform synchronous signal acquisition.

[0018] In this embodiment, the digital microlens array 9 used consists of 1024×768 independent pixels. However, in practical applications, it is impossible to use 1024×768 effective input modes for wavefront modulation. This would result in a very long measurement time for the transmission matrix, as well as a long computation time, large computational load, large memory consumption, and high cost. This embodiment uses only the 768×768 pixels in the middle of the digital microlens array 9 to control the signal light field, i.e., to control the complex amplitude distribution of the target light field. The remaining 256×768 pixels control the reference light for coaxial interferometry measurement of the three-dimensional polarization transmission matrix. The effective incident modes used in this embodiment are 96×96, where every 8×8 pixels of the digital microlens array is considered one effective input mode. The digital microlens array 9 is a binary optical component, theoretically used to control the amplitude distribution of the light field. Combined with a superpixel encoding algorithm, a corresponding binary hologram is calculated. Loading the binary hologram onto the digital microlens array 9 can achieve simultaneous control of the amplitude and phase information of the light field.

[0019] like Figure 2 As shown, a method for controlling multi-degree-of-freedom information of a three-dimensional spatial light field through a scattering medium is applied to a device for controlling multi-degree-of-freedom information of a three-dimensional spatial light field through a scattering medium, and is performed according to the following steps: Step 1: Turn on the laser source system to emit coherent laser source 1; Step 2: The coherent laser source 1 passes through the collimation and beam expansion system, which is used to expand the laser source into a collimated laser beam; Step 3: The collimated laser beam passes through the optical power and polarization direction control system. By changing the principal axis direction of the second half-wave plate 7, the transmitted laser beam, after passing through the optical power and polarization direction control system, obtains a laser power that is adjustable and arbitrary. X A laser beam with linear polarization; Step 4: Turn on the input light field complex amplitude control device. The input light field complex amplitude control device is used to simultaneously control... X Amplitude and phase distribution of a linearly polarized laser beam; Step 5: Modulation target X After passing through the light scattering system, the linearly polarized incident laser beam forms a three-dimensional random speckle field distribution with random distribution of amplitude, phase and polarization in three-dimensional space. This three-dimensional random speckle field information is collected by the signal detection device and sent to the main control computer system. Step 6: Measure the three-dimensional polarization transfer matrix of the scattering system based on the input light field complex amplitude modulation device, the coaxial interferometric measurement transfer matrix method, the signal detection device, and the main control computer. ;like Figure 3 As shown, in this embodiment, the method of measuring the transfer matrix using coaxial interferometry is used to measure the three-dimensional polarization transfer matrix of the scattering system. This is a prerequisite for the present invention to control the amplitude, phase, and polarization distribution of a three-dimensional spatial light field in different planes through a scattering medium by regulating the amplitude and phase distribution of a single linearly polarized incident light field, and is carried out according to the following steps: a: Based on the method of coaxial interferometric measurement of the transmission matrix, a series of binary holograms of the measurement transmission matrix are calculated using a computer 17. In this embodiment, Hadamard basis vectors are used as orthogonal basis vectors to measure the transmission matrix, and the total number of modulated incident modes is... N = 96×96=9216, so we first need to generate a Hadamard matrix with dimensions of 9216×9216, where the Hadamard matrix has a length of 9216×9216. n Listed as number n One Hadamard incident basis vector; b: Using a digital microlens array 9 to simultaneously target the incident first... n A modulated signal light and reference light Modulation is performed, and the three-step phase shift is 0, / 2、 Superimposed on the first n A modulated signal light Then, sequentially compare with the reference light. After interference, the intensity information of the three speckle fields output through the scattering medium is obtained. , and ; c: Measure the three-dimensional polarization transfer matrix using equation (1) The nth column element of any submatrix element t : (1) In equation (1), * denotes complex conjugate. , and These respectively indicate the absence of signal light. Under the premise that only the reference light Perform three-step phase shift 0, , Afterwards, as Figure 4 As shown, reference light The intensity information of three speckle fields output through the scattering medium after interfering sequentially with the reflected laser beam from polarizing beam splitter 5; based on equation (1), the coaxial interferometry method used in this invention requires prior calculation of 3× N +3=27651 binarized holograms were used to measure the transmission matrix.

[0020] d: The computer 17 controls the digital microlens array 9, and the computer 17 loads and stores 27,651 pre-calculated binary holograms of the transmission matrix measured by coaxial interferometry on the digital microlens array 9. e: Rotate the principal axis of the second half-wave plate 7 to any direction; the corresponding polarization direction of the incident light is: X ; f: Move the position of the one-dimensional displacement stage 16 to the target. z At point 1, the principal axis of the linear polarizer 14 is rotated to... H direction; g: The computer 17 controls the digital microlens array 9, which dynamically switches between a series of pre-loaded binary holograms to generate different amplitude and phase distributions of the target light field, and triggers the camera 15 to adjust accordingly. z 1. Planar position H The speckle intensity information in the polarization direction was acquired synchronously. During the experiment, the maximum switching speed of the digital microlens array 9 was 22.27 kHz, but the maximum switching speed of the camera acquiring the speckle intensity information was 180 Hz. This meant that the measurement time for the transmission matrix was mainly limited by the maximum switching speed of camera 15, and measuring one transmission matrix took approximately 3 minutes. Based on the acquired data... z 1. Planar position H The polarization transfer matrix is ​​calculated by combining a series of speckle intensity information along the polarization direction with equation (1). ; h: Maintain the laser beam after passing through the optical power and polarization direction control system as X The linear polarization direction remains unchanged, and the one-dimensional displacement stage 16 is kept on the target. z Position 1 remains unchanged, and the principal axis of the linear polarizer 14 is rotated to... VDirection; using computer 17 to control digital microlens array 9, dynamically switching a series of pre-loaded binary holograms to generate different target light field amplitude and phase distributions, and controlling camera 15 to focus on the corresponding... z 1. Planar position V The speckle intensity information in the polarization direction is acquired synchronously; based on the acquired... z 1. Planar position V The polarization transfer matrix is ​​calculated by combining a series of speckle intensity information along the polarization direction with equation (1). .

[0021] i: Move the position of the one-dimensional displacement stage 16 to the target plane position. z 2 At this point, the principal axis of the linear polarizer 14 is rotated to [location missing]. H and V Direction is determined by speckle measurement and calculation of the target. z 2-position polarization transfer matrix and ; j: Move the position of the one-dimensional displacement stage 16 to the position of the... k Target plane position z k At this location, measure the other locations in sequence. K -2 target plane positions z k polarization transfer matrix and , k ∈[3, K Measuring the polarization transfer matrix of multiple different target planes in three-dimensional space through the scattering medium requires a total of 6 [units of time / time - missing from original text]. K min.

[0022] k: Construct a three-dimensional polarization transfer matrix based on light scattering using equation (2): (2) In equation (2), X Indicates the linear polarization direction of the incident light field. H and V These represent the two orthogonal polarization directions of the output light field transmitted through the scattering medium; Indicates the emitted light is H Linear polarization direction, incident light is X The first of the linear polarization directions k a plane The polarization transfer matrix, Indicates the emitted light is V Linear polarization direction, incident light is X The first of the linear polarization directions k a plane The polarization transfer matrix; ; K Indicates the total number of planes; T This represents the matrix transpose operation.

[0023] Step 7: Define the three-dimensional spatial light field transmitted through the scattering medium. K Two orthogonal polarization directions on a plane H and V Target complex amplitude distribution ,in, and They represent the first k a plane The two orthogonal polarization directions H and V The target light field complex amplitude distribution.

[0024] Step 8: Based on the three-dimensional polarization transfer matrix obtained from experimental measurements Complex amplitude distribution in two orthogonal polarization directions on different planes from the target's three-dimensional space The single element to be modulated is calculated using equation (3). X Complex amplitude distribution of linearly polarized incident light field : (3) In equation (3), This represents the transpose and conjugate operation of a matrix.

[0025] Step 9: Calculate the incident light field of the target using the superpixel coding method. After the corresponding binarized hologram is generated, the main control computer loads the corresponding binarized hologram onto the digital microlens array 9 in the input light field complex amplitude control device, thereby obtaining the amplitude, phase and polarization distribution of the three-dimensional spatial light field generated through the scattering medium.

[0026] Step 10: Experimentally measure the amplitude, phase, and polarization distribution of the three-dimensional spatial light field generated through the scattering medium. The polarization information of the light field depends entirely on the amplitude and phase distribution of its two orthogonal polarization directions. Therefore, the experiment only needs to accurately measure the amplitude and phase distribution in the vertical and horizontal linear polarization directions of different target planes. The amplitude measurement is very simple, only the intensity distribution needs to be measured. However, the phase measurement requires an interferometer. Figure 4 The device measures the phase distribution of the optical field. It is important to note that during the measurement of the phase distribution, the linear polarization directions of the reference light and the signal light must be consistent. This is achieved by changing... Figure 4The device uses a half-wave plate 19 to change the linear polarization direction of the reference light to be consistent with the polarization direction of the signal light. Based on equation (4), the three-step phase shift method is used to measure the amplitude and phase distribution of the optical field. (4) In equation (4), To measure the complex amplitude distribution of the target light field, , and These represent three-step phase shifts (0, 0, ...) of the reflected laser beam from polarizing beam splitter 5. / 2、 Afterwards, as Figure 4 As shown, this is the intensity information of three light fields after they are sequentially interfered with the light field generated with the target plane.

[0027] Step 11: In the experiment, the first... k a plane The two orthogonal polarization directions H and V The complex amplitude distribution of the light field generated above and The complex amplitude information of different planes of the three-dimensional spatial light field generated in the experiment is as follows: This refers to the multi-degree-of-freedom information of the three-dimensional spatial light field generated through the scattering medium.

[0028] Step 12: Generate the three-dimensional spatial light field from the experiment With the target three-dimensional spatial light field The correlation coefficient of the light field is used to quantitatively characterize the accuracy of the multi-degree-of-freedom information of the three-dimensional spatial light field generated through the scattering medium.

Claims

1. A device for controlling a three-dimensional spatial light field with multiple degrees of freedom through a scattering medium, characterized in that, include: Laser source system, collimation and beam expansion system, laser power and polarization direction control system, mirror device, input light field complex amplitude control device, light scattering system, signal detection device and main control computer system; The laser source system is a He-Ne laser, used to emit coherent laser light (1); The collimation and beam expansion system consists of two lenses with different focal lengths, used to collimate and expand the laser source (1) to obtain a collimated laser beam after expansion, and input it into the laser power and polarization direction control system; The laser power and polarization direction control system consists of a first half-wave plate (4), a polarizing beam splitter (5), a light-blocking plate (6), and a second half-wave plate (7). By changing the principal axis direction of the first half-wave plate (4), the collimated laser beam becomes vertically polarized light with continuously adjustable laser intensity after passing through the polarizing beam splitter (5). The polarizing beam splitter (5) outputs a transmitted laser beam and a reflected laser beam, wherein the reflected laser beam is blocked by the light-blocking plate (6). By changing the principal axis direction of the second half-wave plate (7), the transmitted laser beam becomes linearly polarized light in any direction after passing through the second half-wave plate (7) and irradiates the reflecting mirror device, thereby changing the transmission direction of the incident collimated laser beam so that the reflected laser beam can irradiate the effective target surface of the digital microlens array (9) in the input light field complex amplitude control device at an incident angle of 24°. The main control computer system uses a computer (17) to load a binarized hologram onto the digital microlens array (9), and controls the digital microlens array (9) according to the binarized hologram, so that the light field after passing through the digital microlens array (9) passes through the third lens (10), the aperture (11), and the fourth lens (12) in the light field complex amplitude control device in sequence. The +1 order beam corresponds to the complex amplitude distribution of the target controlled linear polarization light field. Thus, the aperture (11) is used to filter the +1 order beam on the focal plane of the third lens (10), thereby obtaining the controlled laser beam. Using the computer (17) to control the digital microlens array (9) behind the fourth lens (12), the signal light and reference light are simultaneously modulated to measure any one of the sub-matrices of the three-dimensional polarization transmission matrix of the light scattering system, and the multi-degree-of-freedom information of the outgoing light field is simultaneously controlled through the scattering medium by adjusting the complex amplitude distribution of the incident light field. The light scattering system uses a scattering medium (13) to simulate a strong scattering environment, thereby disturbing and coupling the amplitude, phase and polarization information of the modulated laser beam to form a three-dimensional random speckle field distribution with random amplitude, phase and polarization in three-dimensional space. The signal detection device consists of a linear polarizer (14), a camera (15) and a one-dimensional displacement stage (16), wherein the camera (15) is fixed on the one-dimensional displacement stage (16); After the three-dimensional random speckle field distribution passes through the linear polarizer (14), a three-dimensional random speckle field distribution in a single linear polarization direction of the target is obtained, and the speckle intensity information of the corresponding plane is collected by the camera (15). By adjusting the front and rear positions of the one-dimensional displacement stage (16) and the principal axis direction of the linear polarizer (14), the camera (15) can acquire the intensity information of the three-dimensional random speckle field in different planes and different polarization directions and send it to the computer (17).

2. A method for controlling a three-dimensional spatial light field with multiple degrees of freedom through a scattering medium, characterized in that, It is applied to the device for controlling the three-dimensional spatial light field with multiple degrees of freedom through a scattering medium as described in claim 1, and is carried out according to the following steps: Step 1: Turn on the laser source system to emit a coherent laser source (1); Step 2: By changing the principal axis direction of the second half-wave plate (7) in the optical power and polarization direction control system, the transmitted laser beam is changed after passing through the optical power and polarization direction control system. X A laser beam with linear polarization; Step 3: Turn on the digital microlens array (9) in the input light field complex amplitude control device; Step 4: Using the digital microlens array (9), simultaneously target the incident first... n A modulated signal light and reference light Modulation is performed, and the three-step phase shift is 0, / 2、 Superimposed on the first n A modulated signal light Then, sequentially compare with the reference light. After interference, the intensity information of the three speckle fields output through the scattering medium is obtained. , and ; Step 5: Measure the three-dimensional polarization transfer matrix using equation (1). any submatrix element t The n Column elements : (1) In equation (1), * denotes complex conjugate. , and These respectively indicate the absence of signal light. Under the premise that only the reference light Perform three-step phase shift 0, , Then, the intensity information of the three speckle fields output through the scattering medium after interfering with the reflected laser beam of the polarizing beam splitter (5) in sequence; Step 6: Maintain the laser beam after passing through the optical power and polarization direction control system as follows: X With the linear polarization direction unchanged, the computer (17) will be used to measure the three-dimensional polarization transfer matrix. any submatrix element t A series of binary holograms are loaded and stored on the digital microlens array (9). By changing the principal axis direction of the polarizer (14) and the position of the one-dimensional displacement stage (16), the computer (17) controls the digital microlens array (9) to dynamically switch the pre-loaded series of binary holograms, thereby generating the amplitude and phase distribution of the incident light field of different targets, and controlling the camera (15) to synchronously acquire speckle intensity information, and sequentially measuring the first... k a plane The corresponding above and Thus, a three-dimensional polarization transfer matrix based on light scattering can be constructed using equation (2). : (2) In equation (1), X Indicates the linear polarization direction of the incident light field. H and V These represent the two orthogonal polarization directions of the output light field transmitted through the scattering medium; Indicates the emitted light is H Linear polarization direction, incident light is X The first of the linear polarization directions k a plane The polarization transfer matrix, Indicates the emitted light is V Linear polarization direction, incident light is X The first of the linear polarization directions k a plane The polarization transfer matrix; ; K Indicates the total number of planes; T Represents the matrix transpose operation; Step 7: Define the three-dimensional spatial light field transmitted through the scattering medium. K Two orthogonal polarization directions on a plane H and V Target complex amplitude distribution ,in, and They represent the first k a plane The two orthogonal polarization directions H and V The complex amplitude distribution of the target light field; Step 8: Calculate the single element to be modulated using equation (3). X Complex amplitude distribution of linearly polarized incident light field : (3) In equation (3), Represents the transpose and conjugate operation of a matrix; Step 9: Calculate the incident light field of the target using the superpixel coding method. After the corresponding binarized hologram is obtained, the main control computer loads the corresponding binarized hologram onto the digital microlens array (9) in the input light field complex amplitude control device, thereby obtaining the amplitude, phase and polarization distribution of the three-dimensional spatial light field generated through the scattering medium. This refers to the multi-degree-of-freedom information of the three-dimensional spatial light field modulated through the scattering medium, among which... and They represent the first k a plane The two orthogonal polarization directions H and V The complex amplitude distribution of the light field generated above.

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