Multi-dimensional complex-amplitude holographic imaging method based on wavelength division multiplexing optical waveguide chip

Abstract

The application discloses a kind of multi-dimensional complex amplitude holographic imaging methods based on wave division multiplexing optical waveguide chip, comprising: obtaining the image to be imaged containing target and pre-processing, obtain a plurality of slices;Each slice is carried out sparse aperture complex amplitude holographic imaging using GS iteration algorithm based on Bessel weighting, obtain the first pre-imaging result and first modulation voltage corresponding to each slice;Splice first pre-imaging result and first modulation voltage, obtain second pre-imaging result and voltage time sequence;Based on the intensity characteristic distribution difference of second pre-imaging result and the image to be imaged, correct voltage time sequence, obtain second modulation voltage;Using second modulation voltage to the holographic imaging of image to be imaged, obtain the holographic imaging result of target.The application solves the image distortion problem existing in diffractive wavefront coding device, and the number of phase shifters used for phase modulation can be reduced from N 2 3N using the chip structure adopted, which greatly reduces the modulation power consumption of optical waveguide phased array.

Description

Technical Field

[0001] This invention belongs to the field of optical imaging technology, specifically relating to a multidimensional complex amplitude holographic imaging method based on wavelength division multiplexing optical waveguide chips. Background Technology

[0002] Active holographic imaging mechanisms can actively and in real-time adjust the generated holographic pattern through programming and other methods. Existing programmable holographic imaging devices mainly include spatial light modulators, digital micromirrors, and programmable metasurfaces. Under the drive of control signals, spatial light modulators can flexibly modulate the characteristics of light waves, thus becoming the main research direction of active holographic imaging. Currently, there are three main types: acousto-optic modulators, digital micromirror devices, and liquid crystal spatial light modulators.

[0003] Florian Willomitzer et al. used an acousto-optic modulator combined with their proposed wavelength holography method to achieve holographic image reconstruction of targets behind scattering media. Chonglei Zhang et al. proposed a dynamic panchromatic 3D holographic imaging method based on a single digital microarray mirror. Through independent phase modulation, the holographic images obtained by this method possess panchromaticity, high refresh rate, and high fidelity. Qiong-Hua Wang and Di Wang et al. proposed using an adjustable liquid crystal grating. Based on the secondary diffraction mechanism of the adjustable liquid crystal grating, they overcame the limitations of narrow imaging field of view and small size in traditional 3D holographic imaging.

[0004] Achieving final 3D display technology based on spatial light modulators with discrete pixel structures still faces challenges. Stephen A. Benton points out in his book that, limited by the pixel size and pixel pitch of the spatial light modulator, the resulting 3D hologram has a small field of view, failing to meet the requirements for direct 3D viewing. Although a type of reflective silicon-based liquid crystal spatial light modulator can solve these problems, its application in AR systems requires an additional projection engine, increasing system size, power consumption, and complexity. While holographic images obtained from silicon-based liquid crystal spatial light modulators can achieve high spatial resolution, the image refresh rate is significantly limited. Digital micromirror spatial light modulators, on the other hand, can achieve holographic images with high-efficiency refresh rates, but their practical application is hindered by limitations in device diffraction efficiency and modulation mechanisms. Furthermore, holographic imaging also suffers from image distortion due to diffraction effects.

[0005] In summary, most existing active digital holographic imaging methods focus on the research of spatial light modulators. However, due to their limited wavefront modulation capabilities, they can only achieve wavefront modulation of a single parameter, resulting in low imaging quality and frame rate. Therefore, the relevant research has certain limitations in the practical application of AR systems. Summary of the Invention

[0006] To address the aforementioned problems in the existing technology, this invention provides a multidimensional complex amplitude holographic imaging method based on a wavelength division multiplexing optical waveguide chip. The technical problem to be solved by this invention is achieved through the following technical solution:

[0007] This invention provides a multidimensional complex amplitude holographic imaging method based on wavelength division multiplexing optical waveguide chips, which can be applied to holographic imaging systems;

[0008] The method includes:

[0009] The image to be imaged, containing the target, is acquired and preprocessed to obtain multiple slices;

[0010] The Gerchberg-Saxton iterative algorithm based on Bessel weighting is used to perform sparse aperture complex amplitude holographic imaging on each slice to obtain the first pre-imaging result and the first modulation voltage corresponding to each slice.

[0011] By stitching together the first pre-imaging results and the first modulation voltage of all slices, the second pre-imaging results and voltage timing sequence are obtained.

[0012] Based on the difference in intensity feature distribution between the second pre-imaging result and the image to be imaged, the voltage timing is corrected to obtain the second modulation voltage;

[0013] Holographic imaging of the image to be imaged is performed using the second modulation voltage to obtain the holographic imaging result of the target.

[0014] In one embodiment of the present invention, the step of acquiring an image to be imaged containing the target and preprocessing it to obtain multiple slices includes:

[0015] Acquire the image to be imaged, which contains the target;

[0016] The image to be imaged is decomposed to obtain the TM component and the TE component;

[0017] The TM and TE components are discretized into three-dimensional slices to obtain multiple slices.

[0018] In one embodiment of the present invention, the holographic imaging system includes: a host computer, a control circuit, a laser, and a wavefront encoding device, wherein the wavefront encoding device includes: a steplessly adjustable low-power complex amplitude optical waveguide chip;

[0019] The steps for performing sparse aperture complex amplitude holographic imaging on each slice using the Bessel-weighted Gerchberg-Saxton iterative algorithm to obtain the first pre-imaging result and the first modulation voltage for each slice include:

[0020] Let i = 1;

[0021] The input light is generated using a laser;

[0022] Under the current modulation voltage of the control circuit, the stepless adjustable low-power complex amplitude optical waveguide chip is used to modulate the input light to obtain the output light;

[0023] The output light is collected to obtain the current imaging result of the i-th slice;

[0024] Input the current imaging result into the host computer and determine whether the current imaging result meets the preset conditions;

[0025] If not, the current modulation voltage is adjusted according to the Gerchberg-Saxton iterative algorithm based on Bessel weighting, and the step of modulating the input light using the wavefront coding device is returned under the adjusted current modulation voltage.

[0026] If so, the current imaging result is used as the first pre-imaging result of the i-th slice, the current modulation voltage is used as the first modulation voltage of the i-th slice, and it is further determined whether i is less than K, where K is the number of slices;

[0027] If i < K, then set i = i + 1 and return to the step of generating input light using the laser; otherwise, obtain the first pre-imaging result and the first modulation voltage corresponding to all slices.

[0028] In one embodiment of the present invention, the continuously adjustable low-power complex amplitude optical waveguide chip includes: an input terminal, a polarization multiplexing unit, a dual-ring cascaded resonant cavity array, a phase shifter array, and a transmitting antenna array.

[0029] In one embodiment of the present invention, under the current modulation voltage of the control circuit, the stepless adjustable low-power complex amplitude optical waveguide chip includes the step of modulating the input light to obtain the output light, comprising:

[0030] The polarization multiplexing unit converts the input light from the input terminal into a polarization signal based on the current modulation voltage applied by the control circuit. The polarization signal is either a TM polarization signal or a TE polarization signal.

[0031] After the intensity of the polarization signal is modulated by the dual-ring cascaded resonant cavity array, the phase shifter array further modulates the phase of the polarization signal;

[0032] The antenna array outputs modulated light.

[0033] In one embodiment of the present invention, the stepless adjustable low-power complex amplitude optical waveguide chip further includes: a 1×2 power divider array, wherein the 1×2 power divider array is connected to the phase shifter array via an optical waveguide;

[0034] The 1×2 power divider array includes cascaded M-stage 1×2 multimode interference couplers. The M-stage 1×2 multimode interference coupler includes a first multimode interference coupler and a second multimode interference coupler. The phase shifter array includes a first phase shifter array and a second phase shifter array. The first multimode interference coupler is connected to the input end of the first phase shifter array through a first optical waveguide, and the second multimode interference coupler is connected to the input end of the second phase shifter array through a second optical waveguide. The first optical waveguide and the second optical waveguide intersect to form a first checkerboard region. The first checkerboard region includes a double-ring cascaded resonant cavity array.

[0035] The output terminals of the first phase shifter array and the second phase shifter array are respectively connected to the third optical waveguide and the fourth optical waveguide, wherein the third optical waveguide and the fourth optical waveguide intersect to form a second chessboard area, and the second chessboard area includes the transmitting antenna array.

[0036] In one embodiment of the present invention, the transmitting antenna array includes N×N transmitting antennas, and the phase shifter array includes 2N thermo-optical phase shifters, wherein the first phase shifter array and the second phase shifter array contain the same number of thermo-optical phase shifters, N=2. M-1 .

[0037] In one embodiment of the present invention, the first chessboard area includes N×N chessboard squares, the dual-ring cascaded resonant cavity array includes N dual-ring cascaded resonant cavities, the N dual-ring cascaded resonant cavities are respectively located in the N chessboard squares on the diagonal of the first chessboard area, and each dual-ring cascaded resonant cavity includes two micro-ring modulators.

[0038] In one embodiment of the present invention, the second chessboard area includes N×N chessboard squares, and each chessboard square includes a transmitting antenna.

[0039] In one embodiment of the present invention, the step of correcting the voltage timing based on the difference in intensity feature distribution between the second pre-imaging result and the image to be imaged to obtain the second modulation voltage includes:

[0040] The weights are calculated based on the second pre-imaging result and the light field intensity of the image to be imaged.

[0041] An N×N dimensional random phase matrix is ​​randomly generated, and this random phase matrix is ​​used as the phase of the transmitting antenna in the second chessboard area.

[0042] Based on phase For the second pre-imaging result I original Performing an inverse Fourier transform yields the strength of the transmitting antenna:

[0043]

[0044] In the formula, j is the imaginary unit;

[0045] Let l = 1;

[0046] Based on the strength A and weight of the transmitting antenna Calculate intermediate parameters B, C, and D sequentially:

[0047]

[0048]

[0049] D = I original ·e jph(C) ;

[0050] Where ph(·) represents the imaginary part;

[0051] The strength of the transmitting antenna is updated by performing an inverse Fourier transform on the intermediate parameter D:

[0052]

[0053] The phase of the transmitting antenna is updated based on the updated intensity A':

[0054]

[0055] Based on the updated intensity A' and the updated phase And determine whether the intensity of the light output by the transmitting antenna at this time meets the preset conditions;

[0056] If so, then the updated magnitude |A'| of the intensity A' and the updated phase are used. Correct the voltage timing to obtain the second modulation voltage; otherwise, let l = l + 1, A' = A, And return the strength A and weight based on the transmitting antenna. The steps for calculating intermediate parameters B, C, and D in sequence.

[0057] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0058] This invention provides a multidimensional complex amplitude holographic imaging method based on wavelength division multiplexing (WDM) optical waveguide chips. Through an image feature weight compensation algorithm, it solves the image distortion problem existing in diffractive wavefront coding devices. Furthermore, by forming a first and second checkerboard area through a bidirectional cross-shaped optical waveguide configuration, it effectively reduces the number of phase shifters used for phase modulation from N... 2 The power consumption has been reduced to 3N (including N dual-ring cascaded resonant cavities and 2N thermo-optical phase shifters), which can greatly reduce the modulation power consumption of the optical waveguide phased array.

[0059] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0060] Figure 1 This is a flowchart of a multidimensional complex amplitude holographic imaging method based on wavelength division multiplexing optical waveguide chip provided in an embodiment of the present invention;

[0061] Figure 2 This is a schematic diagram of the preprocessing of the image to be imaged provided in an embodiment of the present invention;

[0062] Figure 3 This is a schematic diagram of a wavefront coding device provided in an embodiment of the present invention;

[0063] Figure 4 This is a schematic diagram of a stepless adjustable low-power complex amplitude optical waveguide chip provided in an embodiment of the present invention;

[0064] Figure 5 This is a partial schematic diagram of the first chessboard area provided in an embodiment of the present invention;

[0065] Figure 6 This is a schematic diagram of micro-ring modulation provided in an embodiment of the present invention;

[0066] Figure 7 This is a partial schematic diagram of the second chessboard area provided in an embodiment of the present invention;

[0067] Figure 8 This is a schematic diagram illustrating the limitation of the single-slit diffraction envelope on the amplitude distribution of holographic imaging provided in an embodiment of the present invention;

[0068] Figure 9 This is a schematic diagram of antenna feature weighting provided in an embodiment of the present invention;

[0069] Figure 10 This is another schematic diagram of antenna feature weighting provided in an embodiment of the present invention;

[0070] Figure 11 This is a schematic diagram illustrating the principle of the time-division compensation algorithm provided in this embodiment of the invention;

[0071] Figure 12This is a schematic diagram of antenna feature weighted time division multiplexing compensated holographic imaging provided in an embodiment of the present invention. Detailed Implementation

[0072] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0073] Figure 1 This is a flowchart of a multidimensional complex amplitude holographic imaging method based on a wavelength division multiplexing optical waveguide chip provided in an embodiment of the present invention. Figure 1 As shown, this embodiment of the invention provides a multidimensional complex amplitude holographic imaging method based on a wavelength division multiplexing optical waveguide chip, which is applied to a holographic imaging system;

[0074] The above methods include:

[0075] S1. Obtain the image to be imaged containing the target and perform preprocessing to obtain multiple slices;

[0076] S2. Use the Gerchberg-Saxton iterative algorithm based on Bessel weighting to perform sparse aperture complex amplitude holographic imaging on each slice to obtain the first pre-imaging result and the first modulation voltage corresponding to each slice.

[0077] S3. Combine the first pre-imaging results and the first modulation voltage of all slices to obtain the second pre-imaging results and voltage timing sequence.

[0078] S4. Based on the difference in intensity feature distribution between the second pre-imaging result and the image to be imaged, the voltage timing is corrected to obtain the second modulation voltage;

[0079] S5. Use the second modulation voltage to perform holographic imaging on the image to be imaged, and obtain the holographic imaging result of the target.

[0080] Figure 2 This is a schematic diagram of the preprocessing of the image to be imaged according to an embodiment of the present invention. Please refer to... Figure 2 In step S1 above, the step of acquiring the image to be imaged containing the target and preprocessing it to obtain multiple slices includes:

[0081] S101. Acquire the image to be imaged, which contains the target;

[0082] S102. Decompose the image to be imaged to obtain the TM component and the TE component;

[0083] S103. Discretize the TM component and TE component into three-dimensional slices to obtain multiple slices.

[0084] The above process can be represented as follows:

[0085] I = ITM +I TE ={I TM1 +…+I TMi}+{I TE1 +…+I TEj}

[0086] In the formula, I represents the image to be imaged, I TM I TE Representing the TM component and TE component respectively, I TM1 ... I TMi Indicates to I TM The i-th slice after discretization of the 3D slice, I TE1 ... I TEj Indicates to I TE j slices after discretization and 3D slicing.

[0087] Figure 3 This is a schematic diagram of a wavefront coding device provided in an embodiment of the present invention. Figure 3 As shown, in this embodiment, the holographic imaging system includes: a host computer, a control circuit, a laser, and a wavefront encoding device. The wavefront encoding device includes: a continuously adjustable low-power complex amplitude optical waveguide chip.

[0088] Optionally, step S2, which involves performing sparse aperture complex amplitude holographic imaging on each slice using a Bessel-weighted Gerchberg-Saxton iterative algorithm to obtain the first pre-imaging result and the first modulation voltage for each slice, includes:

[0089] S201, Let i = 1;

[0090] S202. Use a laser to generate input light;

[0091] S203. Under the current modulation voltage of the control circuit, the stepless adjustable low-power complex amplitude optical waveguide chip is used to modulate the input light to obtain the output light.

[0092] S204. Collect the output light to obtain the current imaging result of the i-th slice;

[0093] S205. Input the current imaging result into the host computer and determine whether the current imaging result meets the preset conditions.

[0094] S206. If not, adjust the current modulation voltage according to the Gerchberg-Saxton (GS) iterative algorithm based on Bessel weighting, and return to the step of modulating the input light using the wavefront coding device under the adjusted current modulation voltage.

[0095] S207. If so, the current imaging result is used as the first pre-imaging result of the i-th slice, the current modulation voltage is used as the first modulation voltage of the i-th slice, and it is further determined whether i is less than K, where K is the number of slices.

[0096] S208. If i < K, then let i = i + 1 and return to the step of generating input light using the laser; otherwise, obtain the first pre-imaging result and the first modulation voltage corresponding to all slices.

[0097] In this embodiment, the GS iterative algorithm based on Bezier weighting is used to process slice I. Tmi or I TEj Pre-imaging is performed, and the PSNR of the current imaging result can be used as the stopping condition for iteration. That is, in each iteration, the PSNR is used to determine whether the current imaging result meets the preset accuracy.

[0098] It should be noted that the purpose of introducing Bessel weighting in this step is to accelerate the convergence of the iterative process in order to achieve holographic imaging with a sparse array antenna. However, in some other embodiments of this application, weighting methods such as Gaussian weighting and Chebyshev weighting can also achieve the above purpose, and this application does not limit it to these methods. In this embodiment, the antenna position and the complex amplitude of its output light required to reproduce the image to be imaged can be calculated using the GS iterative algorithm based on Bessel weighting.

[0099] In related technologies, phase retrieval algorithms are typically used to calculate the phase of the output light from each antenna element on the transmitting end face in order to reconstruct the image to be imaged as much as possible. Compared with this algorithm, under the same iteration cutoff accuracy conditions, the GS iterative algorithm based on Bessel weighting used in this embodiment to achieve sparse aperture imaging can obtain holographic images of almost the same quality as traditional all-antenna element imaging methods. In addition, the arrangement of sparse aperture antennas has always been used to increase the imaging field of view of phased array antennas through phase adaptation. Sparse aperture antennas correspond to a larger imaging field of view. Therefore, this embodiment can also use an image with a larger field of view to inversely deduce the antenna array, indirectly improving the field of view range of holographic imaging.

[0100] Furthermore, the steplessly adjustable low-power complex amplitude optical waveguide chip includes: an input terminal, a polarization multiplexing unit, a dual-ring cascaded resonant cavity array, a phase shifter array, and a transmitting antenna array.

[0101] In step S203, under the current modulation voltage of the control circuit, the step of using a continuously variable low-power complex amplitude optical waveguide chip to modulate the input light to obtain the output light includes:

[0102] The polarization multiplexing unit converts the input light from the input terminal into a polarization signal based on the current modulation voltage applied by the control circuit. The polarization signal is either a TM polarization signal or a TE polarization signal.

[0103] After the intensity of the polarization signal is modulated by the dual-ring cascaded resonant cavity array, the phase shifter array further modulates the phase of the polarization signal.

[0104] The output light is obtained by modulating the output of the antenna array.

[0105] For example, the continuously variable low-power complex amplitude optical waveguide chip further includes: a 1×2 power divider array, which is connected to a phase shifter array via an optical waveguide;

[0106] The 1×2 power divider array includes cascaded M-stage 1×2 multimode interference couplers. The M-stage 1×2 multimode interference coupler includes a first multimode interference coupler and a second multimode interference coupler. The phase shifter array includes a first phase shifter array and a second phase shifter array. The first multimode interference coupler is connected to the input end of the first phase shifter array through a first optical waveguide, and the second multimode interference coupler is connected to the input end of the second phase shifter array through a second optical waveguide. The first optical waveguide and the second optical waveguide intersect to form a first checkerboard region. The first checkerboard region includes a double-ring cascaded resonant cavity array.

[0107] The outputs of the first phase shifter array and the second phase shifter array are connected to the third optical waveguide and the fourth optical waveguide, respectively. The third optical waveguide and the fourth optical waveguide intersect to form a second chessboard area, which includes a transmitting antenna array.

[0108] In this embodiment, the steplessly adjustable low-power complex amplitude optical waveguide chip includes an input terminal, a polarization multiplexing unit, a 1×2 power divider array, a phase shifter array, and a transmitting antenna array. The polarization multiplexing unit includes a Mach-Zehnder interferometer, a polarization rotator, and a reverse polarization rotator connected in sequence. This polarization multiplexing unit can guide the input light of different polarization states into subsequent waveguide devices. The 1×2 power divider array includes cascaded M-stage 1×2 multimode interference couplers for splitting a single beam into multiple beams.

[0109] Figure 4 This is a schematic diagram of a steplessly adjustable low-power complex amplitude optical waveguide chip provided in an embodiment of the present invention. Please refer to... Figure 4Taking a 1×2 power divider array comprising 5 cascaded 1×2 multimode interference couplers as an example, the 5th 1×2 multimode interference coupler includes a first multimode interference coupler and a second multimode interference coupler. The phase shifter array includes a first phase shifter array and a second phase shifter array. The first multimode interference coupler is connected to the input of the first phase shifter array via a first optical waveguide, and the second multimode interference coupler is connected to the input of the second phase shifter array via a second optical waveguide. Furthermore, the first and second optical waveguides extend in different directions, thus intersecting to form a first checkerboard area. Figure 4 The chessboard structure on the left side of the phase shifter array is shown from the perspective of the first chessboard area, in which a double-ring cascaded resonant cavity array is set.

[0110] Of course, in some other embodiments of the present invention, the 1×2 power divider array may also be composed of cascaded 3, 4, 6, 7 or 8 1×2 multimode interference couplers, and the present invention does not limit this.

[0111] The outputs of the first and second phase shifter arrays are respectively connected to the third and fourth optical waveguides. Similarly, the third and fourth optical waveguides extend in different directions. Figure 4 A second checkerboard area is formed to the right of the phase shifter array from the viewing angle, and a transmitting antenna array is located within the second checkerboard area. In this embodiment, the phase shifter array is used to adjust the phase of the output light field.

[0112] The transmitting antenna array includes N×N transmitting antennas, and the phase shifter array includes 2N thermo-optical phase shifters. The first phase shifter array and the second phase shifter array contain the same number of thermo-optical phase shifters, N=2. M-1 .

[0113] Figure 5 This is a partial schematic diagram of the first chessboard area provided in an embodiment of the present invention. In this embodiment, the first chessboard area includes N×N chessboard squares, and the dual-ring cascaded resonant cavity array includes N dual-ring cascaded resonant cavities. The N dual-ring cascaded resonant cavities are respectively located in the N chessboard squares on the diagonal of the first chessboard area, and each dual-ring cascaded resonant cavity includes two micro-ring modulators.

[0114] Figure 6 This is a schematic diagram of micro-ring modulation provided in an embodiment of the present invention. Please refer to [link / reference]. Figure 5-6If the first direction X is perpendicular to the second direction Y, then in each grid cell on the diagonal of the first grid area, each double-ring cascaded resonant cavity encloses two micro-ring modulators to modulate the output light field intensity of the transmitting antenna. This specific structure along the diagonal allows for stepless adjustment of the output light field intensity of the entire antenna array. Specifically, in the first direction X, the input light field, after being modulated by the micro-ring modulator, combines with the light field in the second direction Y to form a new light field that propagates along the second direction Y. Conversely, in the second direction Y, the input light field, after being modulated by the micro-ring modulator, combines with the light field in the first direction X to form a new light field that propagates along the first direction X.

[0115] The above analysis shows that introducing a micro-ring modulator at the diagonal position of the first chessboard area can change the phase of adjacent waveguides, thereby changing the intensity of the output light field of the transmitting antenna. In this method, only N phase shifters for intensity modulation are needed to achieve N... 2 The light intensity of the path is modulated. Furthermore, to achieve independent phase control, this embodiment also incorporates 2N thermo-optical phase shifters, each controlling the phase of one row / column. Through the coordinated combination of the micro-ring modulator array and the phase shifter array, the above chip can modulate N... 2 The complex amplitude of the output light field of each antenna.

[0116] Figure 7 This is a partial schematic diagram of the second chessboard area provided in an embodiment of the present invention. Further, as... Figure 7 As shown, the second chessboard area includes N×N chessboard squares, and each chessboard square contains a transmitting antenna.

[0117] Specifically, the third optical waveguide extending along the first direction X intersects with the fifth sub-section extending along the second direction Y to form a checkerboard pattern, and is coupled to the transmitting antenna through a directional coupler, thereby enabling the transmitting antenna to emit light from the chip into space.

[0118] Optionally, step S4, which involves correcting the voltage timing based on the difference in intensity feature distribution between the second pre-imaging result and the image to be imaged, to obtain the second modulation voltage, includes:

[0119] S401. Calculate the weights based on the second pre-imaging result and the image to be imaged.

[0120] S402. Randomly generate an N×N dimensional random phase matrix, and use the random phase matrix as the phase of the transmitting antenna in the second chessboard area.

[0121] S403, based on phase For the second pre-imaging result I originalPerforming an inverse Fourier transform yields the strength of the transmitting antenna:

[0122]

[0123] In the formula, j is the imaginary unit;

[0124] S404, Let l = 1;

[0125] S405, Based on the strength A and weight of the transmitting antenna. Calculate intermediate parameters B, C, and D sequentially:

[0126]

[0127]

[0128] D = I original ·e jph(C) ;

[0129] Where ph(·) represents the imaginary part;

[0130] S406. Update the strength of the transmitting antenna by performing an inverse Fourier transform on the intermediate parameter D:

[0131]

[0132] S407. Update the phase of the transmitting antenna based on the updated intensity A':

[0133]

[0134] S408, based on the updated intensity A' and the updated phase And determine whether the intensity of the light output by the transmitting antenna at this time meets the preset conditions;

[0135] S409. If so, then use the updated magnitude |A'| of the intensity A' and the updated phase. Correct the voltage timing to obtain the second modulation voltage; conversely, let l = l + 1, A' = A, And return the strength A and weights based on the transmitting antenna mentioned above. The steps for calculating intermediate parameters B, C, and D in sequence.

[0136] It should be understood that the image on the image plane corresponding to the complex amplitude light field generated by the wavefront encoding device can be represented by the Fourier transform of the output light field. Let the complex amplitude of the output light field of the integrated optical waveguide phased array be expressed as: E s (x,y)=S·e iφs Then the light field on the image plane at a distance Z from the emitting end face can be described as:

[0137]

[0138] Existing digital holographic imaging technology uses discrete antenna arrays to encode light beams and forms holographic images through diffraction effects. The output light field distribution of the antenna array can be expressed as:

[0139] U(θ x ,θ y )=S(θ x ,θ y )·M(θ x ,θ y (2)

[0140] The far-field distribution of the output light from a diffractive antenna array is determined by two factors: the diffraction envelope S(θ) of a single antenna. x ,θ y The array factor M(θ) determined by the antenna arrangement x ,θ y Using MATLAB and substituting relevant parameters, we can obtain... Figure 8 The single-slit diffraction envelope shown restricts the amplitude distribution in holographic imaging. Figure 8 Analysis shows that the far-field beam generated by the diffraction array is naturally limited by an envelope determined by a single antenna. This phenomenon leads to contrast distortion in the holographic image, causing wavefront coding devices to only be able to reproduce the image at the center or focal point of the holographic image with high quality. This phenomenon greatly limits the application prospects of diffraction antenna wavefront coding devices in holographic imaging.

[0141] Specifically, this embodiment uses equation (1) for calculation. By controlling the amplitude and phase of the transmitting end face of the antenna array, the complex amplitude of the light field on the image plane can be changed. For the complex amplitude holographic imaging involved in this embodiment, it can be equivalent to calculating the amplitude and phase of the transmitting end face, so that the field distribution of this part of the light field after far-field interference superposition matches the target to be imaged. Specifically, the following formula can be used:

[0142]

[0143] in, This is the error function, and its value can characterize the error between the reconstructed image and the original image.

[0144] Furthermore, solving the above optimization problem is actually an iterative optimization of the amplitude and phase values ​​of the output light field of each transmitting antenna on the transmitting end face, so as to minimize the error between the reconstructed hologram and the original image.

[0145] Based on the Bessel-weighted Gerchberg-Saxton iterative algorithm, this embodiment combines the amplitude characteristic distribution curve of the target to be imaged with the diffraction envelope of a single antenna of the encoding device to inversely deduce the weights of the antenna elements to the holographic image. The optimization problem shown in equation (3) is then solved based on these weights. The antenna envelope and the weights of the image to be imaged can be expressed as:

[0146]

[0147] Among them, M na (I ij M represents the light field distribution at position (x, y) of the output light field. cal (I ij ) represents the light field distribution at position (x,y) of the light field of the image to be imaged.

[0148] Figure 9 This is a schematic diagram of antenna feature weighting provided in an embodiment of the present invention. Specifically, image feature weights are used as the weighting method for an iterative algorithm to solve the optimization problem. Because there are always values ​​close to 0 under this weight, the algorithm will inevitably converge during the iteration process. The specific principle of the algorithm is as follows: Figure 9 As shown. Figure 9 In the image, the left side shows the amplitude distribution of the image to be imaged, the middle side shows the amplitude distribution of the hologram obtained by the traditional imaging method after single-slit envelope modulation, and the image clearly shows distortion in amplitude contrast; the right side shows the light field distribution obtained after weighting, and the amplitude contrast at each position in the image is consistent with that of the image to be imaged.

[0149] The algorithm works as follows:

[0150] Step 1: Input the image of the target to be imaged;

[0151] Step 2: Discretize the amplitude distribution features of the image based on the spatial resolution of the wavefront coding device;

[0152] Step 3: Compare the antenna element envelope of the wavefront coding device with the feature distribution of the target to be imaged; Step 4: Solve for the feature weights.

[0153] Step 5, Enter Figure 10 The iterative process is shown.

[0154] This method utilizes the overlay of multiple images, which can effectively improve image quality, specifically as follows: Figure 11As shown. Although the above process uses a multi-frame-frequency superposition imaging method, its modulation speed for integrated optical components is much higher than that of existing wavefront coding devices, thus fully meeting the application requirements of high frame-frequency holographic imaging. The weighting method proposed in this embodiment can effectively solve the problem of holographic image distortion caused by the antenna element envelope.

[0155] It should be noted that the present invention can be further adjusted using a time-division compensation algorithm. Figure 11 This is a schematic diagram illustrating the principle of the time-division compensation algorithm provided in this embodiment of the invention. The time-division compensation algorithm analyzes and solves the image to determine the light field intensity (amplitude) distribution curves under different viewing angles. By increasing the imaging frequency, it compensates for the poor imaging effect caused by the antenna diffraction envelope. The specific principle is as follows: Figure 11 As shown, the horizontal axis represents the spatial distribution location, and the vertical axis represents the light intensity. (From...) Figure 11 As can be seen, time-division compensation can compensate for the light contrast distortion problem in holograms. However, the closer the imaging position is to the edge, the more times compensation is required.

[0156] Although the algorithm can fully compensate for the holographic contrast distortion caused by the antenna envelope at each location, as the size of the antenna array increases and the resolution of the holographic image improves, the compensation method during traversal will increase the computational load on the computer and result in a lower frame rate for the holographic image.

[0157] This method utilizes the overlay of multiple images, which can effectively improve image quality, specifically as follows: Figure 12 As shown. Although this algorithm uses a multi-frame-frequency superposition imaging method, its modulation speed is much higher than that of existing wavefront coding devices for integrated optical components, thus fully meeting the application requirements of high frame-frequency holographic imaging. This embodiment can effectively solve the problem of holographic image distortion caused by the antenna element envelope.

[0158] In summary, the overall process of the multidimensional complex amplitude holographic imaging method based on wavelength division multiplexing optical waveguide chip provided by this invention is as follows:

[0159] Step A. Based on the capabilities of existing wavefront coding equipment, slice the image to be imaged I horizontally, where I = I TM +I TE And set the expected maximum light intensity I. M ;

[0160] Step B. Based on the capabilities of existing wavefront coding equipment, perform discretized three-dimensional slice classification on the image to be imaged I, where I = I TM +I TE ={I TM1 +…+I TMi}+{ITE1 +…+I TEj};

[0161] Step C. Perform pre-imaging analysis based on the sparse aperture imaging method, compare the pre-imaging results with the target to be imaged, and establish a new optimization problem: how to compensate and generate a high-quality holographic image with the fewest number of iterations;

[0162] Step D. For any slice I Tmi or I TEj Based on the analysis of the antenna element envelope and the features of the target to be imaged, the weights of the transmitting antenna array are determined, and the maximum light intensity I under these weights is calculated. n Comparison I n with I M Calculate the number of iterations N required to complete the slice. i or N j ;

[0163] Step E. Based on the results in Step C, perform pre-imaging of the target to be imaged, compare the spatial distribution characteristics of the target to be imaged with the results of the second pre-imaging, and analyze the locations that do not meet the set accuracy.

[0164] Step F. Optimize the images at these locations individually using a time-division compensation method based on sparse aperture imaging, and calculate the number of iterations N required to complete the slice using the time-division compensation method. ii or N jj ;

[0165] Step G. Repeat the above process for each slice in turn, and finally obtain the number of iterations and light field distribution required to complete each slice;

[0166] Step H. End.

[0167] As can be seen from the above embodiments, the beneficial effects of the present invention are as follows:

[0168] This invention provides a multidimensional complex amplitude holographic imaging method based on wavelength division multiplexing (WDM) optical waveguide chips. Through an image feature weight compensation algorithm, it solves the image distortion problem existing in diffractive wavefront coding devices. Furthermore, by forming a first and second checkerboard area through a bidirectional cross-shaped optical waveguide configuration, it effectively reduces the number of phase shifters used for phase modulation from N... 2 The power consumption has been reduced to 3N (including N dual-ring cascaded resonant cavities and 2N thermo-optical phase shifters), which can greatly reduce the modulation power consumption of the optical waveguide phased array.

[0169] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0170] Although this application has been described herein in conjunction with various embodiments, other variations of the disclosed embodiments can be understood and implemented by those skilled in the art in carrying out the claimed application by reviewing the accompanying drawings, the disclosure, and the appended claims.

[0171] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A multidimensional complex amplitude holographic imaging method based on wavelength division multiplexing optical waveguide chips, characterized in that, Applications in holographic imaging systems; The method includes: The image to be imaged, containing the target, is acquired and preprocessed to obtain multiple slices; The sparse aperture complex amplitude holographic imaging of each slice is performed using the Bessel weighted Geisberg-Saxton iterative algorithm to obtain the first pre-imaging result and the first modulation voltage corresponding to each slice. By stitching together the first pre-imaging results and the first modulation voltage of all slices, the second pre-imaging results and voltage timing sequence are obtained. Based on the difference in intensity feature distribution between the second pre-imaging result and the image to be imaged, the voltage timing is corrected to obtain the second modulation voltage; Holographic imaging of the image to be imaged is performed using the second modulation voltage to obtain the holographic imaging result of the target; The steps of acquiring and preprocessing the image containing the target to obtain multiple slices include: Acquire the image to be imaged, which contains the target; The image to be imaged is decomposed to obtain the TM component and the TE component; The TM and TE components are discretized into three-dimensional slices to obtain multiple slices. The holographic imaging system includes: a host computer, a control circuit, a laser, and a wavefront encoding device. The wavefront encoding device includes: a steplessly adjustable low-power complex amplitude optical waveguide chip. The steps of performing sparse aperture complex amplitude holographic imaging on each slice using the Geisenberg-Saxton iterative algorithm based on Bessel weighting to obtain the first pre-imaging result and the first modulation voltage for each slice include: make i =1; The input light is generated using a laser; Under the current modulation voltage of the control circuit, the input light is modulated using the continuously variable low-power complex amplitude optical waveguide chip to obtain the output light; The output light is collected to obtain the first... i The current imaging results for each slice; Input the current imaging result into the host computer and determine whether the current imaging result meets the preset conditions; If not, the current modulation voltage is adjusted according to the Geisberg-Saxton iterative algorithm based on Bessel weighting, and the step of modulating the input light using the wavefront coding device is returned under the adjusted current modulation voltage. If so, then the current imaging result will be used as the first... i The first pre-imaging result of the slice, using the current modulation voltage as the first... i The first modulation voltage of each slice, and further judgment i Is it less than K , K Number of slices; like i < K Then let i = i After +1, return to the step of generating input light using a laser; otherwise, obtain the first pre-imaging result and the first modulation voltage corresponding to all slices.

2. The multidimensional complex amplitude holographic imaging method based on wavelength division multiplexing optical waveguide chip according to claim 1, characterized in that, The continuously adjustable low-power complex amplitude optical waveguide chip includes: an input terminal, a polarization multiplexing unit, a dual-ring cascaded resonant cavity array, a phase shifter array, and a transmitting antenna array.

3. The multidimensional complex amplitude holographic imaging method based on wavelength division multiplexing optical waveguide chip according to claim 2, characterized in that, The steps of modulating the input light using the continuously variable low-power complex amplitude optical waveguide chip under the current modulation voltage of the control circuit to obtain the output light include: The polarization multiplexing unit converts the input light from the input terminal into a polarization signal based on the current modulation voltage applied by the control circuit. The polarization signal is either a TM polarization signal or a TE polarization signal. After the dual-ring cascaded resonant cavity array modulates the intensity of the polarization signal, the phase shifter array further modulates the phase of the polarization signal. The antenna array outputs modulated light.

4. The multidimensional complex amplitude holographic imaging method based on wavelength division multiplexing optical waveguide chip according to claim 2, characterized in that, The continuously adjustable low-power complex amplitude optical waveguide chip further includes: a 1×2 power divider array, which is connected to the phase shifter array via an optical waveguide; The 1×2 power divider array includes cascaded M-stage 1×2 multimode interference couplers. The M-stage 1×2 multimode interference coupler includes a first multimode interference coupler and a second multimode interference coupler. The phase shifter array includes a first phase shifter array and a second phase shifter array. The first multimode interference coupler is connected to the input end of the first phase shifter array through a first optical waveguide, and the second multimode interference coupler is connected to the input end of the second phase shifter array through a second optical waveguide. The first optical waveguide and the second optical waveguide intersect to form a first checkerboard region. The first checkerboard region includes a double-ring cascaded resonant cavity array. The output terminals of the first phase shifter array and the second phase shifter array are respectively connected to the third optical waveguide and the fourth optical waveguide, wherein the third optical waveguide and the fourth optical waveguide intersect to form a second chessboard area, and the second chessboard area includes the transmitting antenna array.

5. The multidimensional complex amplitude holographic imaging method based on wavelength division multiplexing optical waveguide chip according to claim 4, characterized in that, The transmitting antenna array includes N×N transmitting antennas, and the phase shifter array includes 2N thermo-optical phase shifters, wherein the first phase shifter array and the second phase shifter array contain the same number of thermo-optical phase shifters, N=2. M-1 .

6. The multidimensional complex amplitude holographic imaging method based on wavelength division multiplexing optical waveguide chip according to claim 5, characterized in that, The first chessboard area includes N×N chessboard squares, and the dual-ring cascaded resonant cavity array includes N dual-ring cascaded resonant cavities. The N dual-ring cascaded resonant cavities are respectively located in the N chessboard squares on the diagonal of the first chessboard area, and each dual-ring cascaded resonant cavity includes two micro-ring modulators.

7. The multidimensional complex amplitude holographic imaging method based on wavelength division multiplexing optical waveguide chip according to claim 6, characterized in that, The second chessboard area comprises N×N chessboard squares, and each chessboard square includes a transmitting antenna.

8. The multidimensional complex amplitude holographic imaging method based on wavelength division multiplexing optical waveguide chip according to claim 7, characterized in that, The step of correcting the voltage timing based on the difference in intensity feature distribution between the second pre-imaging result and the image to be imaged, to obtain the second modulation voltage, includes: Weights are calculated based on the second pre-imaging result and the image to be imaged. ; An N×N dimensional random phase matrix is ​​randomly generated, and this random phase matrix is ​​used as the phase of the transmitting antenna in the second chessboard area. ; Based on phase For the second pre-imaging results Performing an inverse Fourier transform yields the strength of the transmitting antenna: ； In the formula, The imaginary unit; make l =1; Based on the strength of the transmitting antenna Weight Calculate intermediate parameters sequentially , , : ； ； ； in, Indicates the imaginary part; By using intermediate parameters Perform an inverse Fourier transform to update the strength of the transmitting antenna: ； Based on the updated strength Update the phase of the transmitting antenna: ； Based on the updated strength and the updated phase And determine whether the intensity of the light output by the transmitting antenna at this time meets the preset conditions; If so, then utilize the updated strength. modulus and the updated phase Correct the voltage timing to obtain the second modulation voltage; otherwise, let l = l+ 1. , and return the strength based on the transmitting antenna. Weight Calculate intermediate parameters sequentially , , The steps.

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