A device and method for measuring compressed sensing spectrum with electro-optical control transmittance coding

Abstract

The present invention belongs to the technical field of spectral measurement, and specifically relates to a compressed sensing spectral measurement device with electro-optically controlled transmittance coding. The device comprises a collimating lens, a polarizer, an electro-optical modulator, an analyzer, a converging lens, and a photodetector arranged in sequence. The photodetector is connected to an FPGA control and data acquisition module. The FPGA control and data acquisition module is connected to the electro-optical modulator via an LC resonant high-voltage drive circuit. The FPGA control and data acquisition module is connected to a computer. Based on the basic theory of compressed sensing, a high-performance electro-optical modulator is designed and developed to achieve spectral transmittance coding, overcome the need for aperture-coded compressed spectral measurement technology to use a dispersive spectroscopic element to achieve coding conversion from the spectral dimension to the spatial dimension, reduce the complexity of the optical system and the cost of spectral measurement, and combine FPGA-based drive control and digital phase-locked amplification data processing technology to achieve high-speed spectral measurement signal acquisition.

Description

Technical Field

[0001] The present invention belongs to the technical field of spectral measurement, and in particular relates to a compressed sensing spectral measurement device and method for electro-optical transmittance coding. Background Art

[0002] Existing typical spectral measurement technologies are divided into the following categories: the first category is dispersive spectral measurement technology. Dispersive spectral measurement technology is divided into prism spectral measurement technology and grating spectral measurement technology. The advantage of prism spectroscopy is that it is less affected by ambient temperature, humidity and vibration and has low cost. The disadvantages are the introduction of slits, small light flux, low sensitivity, and nonlinear prism dispersion. Grating spectroscopy has a simple structure, short measurement time, and a wide range of applications, but it also requires the introduction of slits, and grating diffraction has multiple levels, which limits the spectral measurement range. The second category is interference spectral measurement technology, which includes spatial interference type and time modulation type.

[0003] Spatial interferometry spectroscopy is mainly based on structures such as the Sagnac triangular common-path interferometer and the birefringence Fourier transform of the Wollaston prism. It has the advantages of simple and compact structure, small size, and good vibration resistance. However, its disadvantages are small optical path difference, limited spectral resolution, and high manufacturing cost.

[0004] Internationally, representative products for time-modulated Fourier transform spectroscopy include those from Bruker in Germany and ABB in the United States. Both utilize a modified Michelson interferometer structure, resulting in high light energy utilization, excellent signal-to-noise ratio, a wide spectral range, and high spectral resolution. However, their drawbacks include difficulty in miniaturization, limited vibration resistance, and limited measurement speed.

[0005] Other types of spectral measurement technologies, such as those based on acousto-optic tunable filters, liquid crystal tunable filters, and MEMS technology, can also be applied to the research of small-scale, integrated spectral measurement technologies. With the increasing demand for spectral measurement technology and instrument performance, spectral measurement speed, instrument size, manufacturing cost, and spectral resolution are facing severe challenges. Therefore, researchers have been actively exploring new spectral measurement technologies. In 2004, Chinese-American scientist Terence Tao, Candes and Romberg of California Institute of Technology, and Donoho of Stanford University proposed the compressed sensing sampling theory, demonstrating the feasibility of simultaneous signal sampling and compression, providing new ideas for the development of high-speed, high-resolution spectral measurement technologies and instruments.

[0006] Currently, there are two main spectral measurement technologies based on compressed sensing theory: aperture coding and transmission coding. The key technical features of aperture coding compressed sensing spectral measurement technology are the use of a two-dimensional aperture coding plate to achieve spatial encoding and the use of a dispersion prism to achieve the conversion from spatial to spectral encoding. The advantage is a large clear aperture, making it suitable for spectral imaging detection. However, the encoding requires a conversion from spatial to spectral dimensions, which results in a relatively large system structure.

[0007] Another approach is transmittance-encoded compressed sensing spectroscopy. This type of spectral measurement technology features a liquid crystal variable phase retarder placed between orthogonal polarizers to adjust spectral transmittance. By applying varying voltages to adjust the transmittance of the spectral signal, encoding can be performed directly in the spectral dimension. This technology offers high spectral resolution, compact design, low power consumption, and low system cost. However, existing devices such as liquid crystal variable phase retarders and liquid crystal tunable filters are significantly affected by ambient temperature, and FP resonators are sensitive to vibration interference and have limited operational stability. Consequently, the application of spectral measurement technology in these new technological fields places increasingly stringent requirements on spectral resolution, measurement speed, and sensitivity. In particular, the miniaturization and integrated design of spectral instruments face unprecedented challenges. How to further improve the speed, resolution, and sensitivity of spectral measurement while also balancing the miniaturization and automated integration of spectral analysis instruments is a critical technical challenge that must be addressed in the development of spectral measurement technology. Summary of the Invention

[0008] In response to the above technical problems, the present invention provides a compressed sensing spectral measurement device and method with electro-optical control transmittance coding, which can realize spectral transmittance coding, improve spectral measurement speed, and reduce the complexity of the optical system and the cost of spectral measurement.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0010] A compressed sensing spectrum measurement device with electro-optically regulated transmittance coding comprises a collimating lens, a polarizer, an electro-optical modulator, an analyzer, a converging lens, and a photodetector, which are sequentially arranged. The photodetector is connected to an FPGA control and data acquisition module, which is connected to the electro-optical modulator via an LC resonant high-voltage drive circuit. The FPGA control and data acquisition module is connected to a computer. After the input of a light source to be measured is collimated, the incident light is converted into linearly polarized light after passing through the polarizer, and then electro-optically modulated and then emitted through the analyzer, thereby achieving transmittance modulation with electro-optical modulation. The FPGA control and data acquisition module collects compressed spectrum measurement signals output by the photodetector and coded drive signals output by the LC resonant high-voltage drive circuit.

[0011] The FPGA control and data acquisition module includes an FPGA core chip, a first signal acquisition unit, and a second signal acquisition unit. The photodetector is connected to the FPGA core chip through the first signal acquisition unit, and the LC resonant high-voltage drive circuit is connected to the FPGA core chip through the second signal acquisition unit. The FPGA core chip controls the operation of the first signal acquisition unit and the second signal acquisition unit to achieve one-to-one synchronous acquisition of the measurement light signal and the encoded drive control voltage signal, thereby achieving synchronous measurement of the drive voltage and the compressed spectrum signal.

[0012] The electro-optic modulator is a lithium niobate transverse electro-optic modulator, whose electro-optic crystal uses an X-cut lithium niobate electro-optic crystal and is placed between orthogonal polarizers. It uses the transverse electro-optic effect under the action of an external electric field to achieve intensity regulation and direct encoding of compressed sensing spectral measurement in the spectral dimension.

[0013] The size of the X-cut lithium niobate electro-optical crystal is 2×4×40 mm, and an electric field is applied along the x-direction of the crystal, and light is transmitted along the z-axis direction of the crystal.

[0014] It also includes a fiber coupler 1 and a fiber coupler 2. The fiber coupler 1 is arranged in front of the collimating lens, and the fiber coupler 2 is arranged behind the converging lens. The light source to be measured is input through the fiber coupling, and the compressed measurement spectrum signal is output through the fiber coupling.

[0015] A measurement method comprising the following steps:

[0016] S1. Build a spectrum measurement device;

[0017] S2. Select an appropriate sparse basis and, based on the measurement spectral range and resolution requirements, use sequential floating forward selection, sequential forward selection, or sequential backward selection to implement transmittance measurement matrix encoding and determine the encoding voltage;

[0018] S3, according to the driving voltage requirements of S2, traverse all coded driving voltages;

[0019] S4, collecting the encoding voltage and the compressed spectrum measurement signal in a one-to-one correspondence;

[0020] S5. Apply the orthogonal matching pursuit algorithm, the sparsity adaptive matching pursuit algorithm or the iterative soft threshold algorithm, and the two-step iterative shrinkage algorithm to achieve high compression ratio, high speed and high precision spectral reconstruction.

[0021] Spectral signal sparsification is achieved using discrete cosine basis, wavelet basis and learning dictionary, and the spectral signal sparsification ratio of the original spectral signal is better than 3%.

[0022] The spectrum measurement device in S1 collimates the light source to be measured, and then the incident light becomes linearly polarized light after passing through the polarizer, and the angle between the direction of the linear polarized light and the principal axis of the electro-optical refractive index is 45°. After electro-optical modulation, it is emitted through the analyzer; the electro-optic modulator is a lithium niobate transverse electro-optic modulator, and the electro-optic crystal adopts an x-cut crystal. Light is passed along the optical axis z-axis, and an electric field is applied along the x-axis. Under the action of the transverse electro-optic effect, the two refractive index principal axes of the lithium niobate electro-optic crystal rotate 45° and change in size; the transmittance control system composed of orthogonal polarizers and electro-optic modulators is combined with a photodetector to form a compressed spectrum measurement device.

[0023] A periodic AC voltage is used to drive the electro-optic modulator, and the driving voltage required for all non-correlated measurements is traversed in a short time. A dual-channel AD acquisition system is used, and the dual-channel AD operation is controlled by FPGA.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] Starting from the basic theory of compressed sensing, we design and develop a high-performance electro-optical modulator to achieve spectral transmittance encoding, overcome the aperture coding compressed spectral measurement technology that requires the use of dispersive spectroscopic elements to achieve encoding conversion from spectral dimension to spatial dimension, reduce the complexity of the optical system and the cost of spectral measurement, and combine FPGA-based drive control and digital phase-locked amplification data processing technology to achieve high-speed spectral measurement signal acquisition, and give full play to the application advantages in the field of high-speed, miniaturized, stable operation and high-resolution spectral detection applications.

[0026] The transmittance control achieved by electro-optical modulation is applied to compressed sensing spectral measurement coding, which provides a theoretical basis for the measurement application of wide spectrum transmittance coding with fast compression, low power consumption and small measurement data. The modulation device that realizes electro-optical transmittance coding has good environmental adaptability.

[0027] The spectral signal is sparsely compressed with a high sparsity ratio using discrete cosine, wavelet basis and learning dictionary. The transmittance coding measurement matrix can achieve non-correlated, pseudo-random coding using algorithms such as sequential floating forward selection (SFFS), sequential forward selection (SFS) and sequential backward selection (SBS).

[0028] The orthogonal matching pursuit algorithm (OMP), the sparsity adaptive matching pursuit algorithm (SAMP), the iterative soft threshold algorithm (IST), and the two-step iterative shrinkage algorithm (TwIST) can be applied to optimize the reconstruction algorithm to realize spectral signal reconstruction, thereby achieving spectral compressed sensing measurement with a larger compression ratio and higher accuracy.

[0029] A dual-channel data acquisition solution based on FPGA control is adopted to realize the synchronous acquisition of driving voltage signals and spectral measurement signals. The transmittance coding corresponds to the compressed measurement signal one-to-one, which is conducive to the realization of high spectral resolution, high speed and high precision spectral measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural schematic diagram of the spectrum measuring device of the present invention;

[0031] Figure 2 Schematic diagram of electro-optical transmittance control according to the present invention;

[0032] Figure 3 This is a schematic diagram of the electro-optical transmittance coding principle of the present invention;

[0033] Among them: 1 is the light source to be measured, 2 is the first fiber coupler, 3 is the collimating lens, 4 is the polarizer, 5 is the electro-optic modulator, 6 is the analyzer, 7 is the converging lens, 8 is the second fiber coupler, 9 is the photodetector, 10 is the LC resonant high-voltage driving circuit, 11 is the computer, and 12 is the FPGA control and data acquisition module. DETAILED DESCRIPTION

[0034] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0035] like Figure 1 As shown, a compressed sensing spectroscopy measurement device with electro-optically modulated transmittance coding includes a collimating lens 3, a polarizer 4, an electro-optical modulator 5, an analyzer 6, a converging lens 7, a photodetector 9, an LC resonant high-voltage drive circuit 10, a computer 11, and an FPGA control and data acquisition module 12. After the light source to be measured is collimated, the incident light passes through the polarizer and becomes linearly polarized light, with the direction of the linearly polarized light forming an angle of 45° with the principal axis of the electro-optical refractive index. After electro-optical modulation, the linearly polarized light is then analyzed and emitted, achieving transmittance modulation with electro-optical modulation. The FPGA control and data acquisition module collects the compressed spectrum measurement signal output by the photodetector and the coded drive signal output by the LC resonant high-voltage drive circuit.

[0036] Specifically: the collimating lens 3 and the converging lens 7 are both K9 glass plano-convex lenses with a focal length of f = 6 mm and a diameter of D = 6 mm. The polarizer 4 and the analyzer 6 use Glan-Taylor polarizers with a high extinction ratio of up to 10 5 :1.

[0037] Furthermore, the FPGA control and data acquisition module 12 includes an FPGA core chip, a first signal acquisition unit AD1 and a second signal acquisition unit AD2. The photodetector is connected to the FPGA core chip through the first signal acquisition unit AD1, and the LC resonant high-voltage drive circuit is connected to the FPGA core chip through the second signal acquisition unit AD2. The FPGA core chip controls the operation of the first signal acquisition unit AD1 and the second signal acquisition unit AD2 to realize one-to-one synchronous acquisition of the measurement light signal and the encoded drive control voltage signal, thereby achieving synchronous measurement of the drive voltage and the compressed spectrum signal.

[0038] Furthermore, two fiber couplers are provided (fiber coupler 1 2 and fiber coupler 2 8), which are respectively arranged before the collimating lens and after the converging lens. The light source to be measured is input through fiber coupling, and the compressed measurement spectrum signal is output through fiber coupling.

[0039] Furthermore, the electro-optic modulator is a lithium niobate transverse electro-optic modulator, and its electro-optic crystal uses an X-cut lithium niobate electro-optic crystal and is placed between orthogonal polarizers. It uses the transverse electro-optic effect under the action of an external electric field to achieve intensity regulation and direct encoding of compressed sensing spectral measurements in the spectral dimension.

[0040] Furthermore, the size of the X-cut lithium niobate electro-optical crystal is 2×4×40 mm, and an electric field is applied along the x-direction of the crystal, and light is transmitted along the z-axis direction of the crystal.

[0041] A method for measuring compressed sensing spectrum with electro-optical transmittance coding includes the following steps:

[0042] S1. Build a spectrum measurement device;

[0043] S2. Select an appropriate sparse basis and, based on the measurement spectral range and resolution requirements, use sequential floating forward selection, sequential forward selection, or sequential backward selection to implement transmittance measurement matrix encoding and determine the encoding voltage;

[0044] S3, according to the driving voltage requirements of S2, traverse all coded driving voltages;

[0045] S4, collecting the encoding voltage and the compressed spectrum measurement signal in a one-to-one correspondence;

[0046] S5. Apply the orthogonal matching pursuit algorithm, the sparsity adaptive matching pursuit algorithm or the iterative soft threshold algorithm, and the two-step iterative shrinkage algorithm to achieve high compression ratio, high speed and high precision spectral reconstruction.

[0047] Based on the transverse electro-optic effect of lithium niobate, a transmittance modulation device with flexible modulation is designed, which utilizes the transformation of the optical properties of the crystal caused by the electro-optic effect under the action of an external electric field. Under the action of an external electric field, lithium niobate changes from a uniaxial crystal to a biaxial crystal, and the refractive index difference on the two main refractive index axes is proportional to the external electric field. The electro-optic modulator is a lithium niobate transverse electro-optic modulator. The electro-optic crystal adopts an x-cut crystal. Light is transmitted along the optical axis z-axis, and an electric field is applied along the x-axis direction. Under the action of the transverse electro-optic effect, the two refractive index main axes of the lithium niobate electro-optic crystal rotate , and the size changes. The two polarization components decomposed along the two refractive index main axis directions produce a phase difference as the refractive index changes, and can be described as

[0048]

[0049] Among them, L x and L z are the lengths of the electro-optic crystal sample in the x-axis direction and the z-axis direction of the crystal, respectively. The electric field of the electro-optic crystal in the x-direction is E=V / L x Proportional to the voltage V applied to the electro-optical crystal and the thickness of the crystal L x Inversely proportional. Figure 1 As shown, the electro-optic modulator is placed between two orthogonal polarizers, with the transmission axes of the polarizer and analyzer at 0° and 90° respectively. The Stokes vector of the incident light after passing through the 0° polarizer is denoted as S in =(I0,I0,0,0) T , where I0 is the total light intensity. According to the light polarization transmission theory, the Stokes vector of the outgoing light can be described as

[0050] S out =M A M EOM S in (2)

[0051] In the above formula, M A and M EOM The Muller matrices of the 90° analyzer and electro-optic modulator are respectively. When an electric field is applied to the x-cut transverse lithium niobate electro-optic modulator, the refractive index axis deflects 45°, which is equivalent to a phase retarder with a modulation fast axis of 45°. Considering that the total light intensity is the first component of the Stokes vector, the light intensity after the electro-optic modulation is

[0052]

[0053] Therefore, the transmittance of the system modulated by the electro-optic modulator can be calculated as

[0054]

[0055] It can be seen from the above formula that the incident spectrum transmittance is completely determined by the phase difference of the electro-optic modulator, and when the geometric size of the electro-optic modulator is designed, the transmittance is closely related to the wavelength of the incident light and the external electric field voltage. By placing the lithium niobate transverse electro-optic modulator between orthogonal polarizers and setting the external electric field voltage, the transmittance of incident light of different wavelengths can be controlled, thereby realizing spectral transmittance encoding. Therefore, the optical transmittance of the transmittance control system after the electro-optic device can be further described as

[0056] T (λ,V) =I (λ,V) / I 0(λ) ∝sin 2 (δ (λ,V) / 2) (5)

[0057] Where λ is the wavelength of the incident light, V is the external electric field voltage applied to the electro-optical device, and I 0(λ) and I (λ,V) are the light intensities before and after the incident light passes through the electro-optical control system, δ (λ,V) is the phase difference between the two polarization components of the incident light passing through the electro-optic device under the action of the external electric field. It can be seen from formula (1) that when the size of the electro-optic crystal is determined, the spectral transmittance is only determined by the external electric field voltage V, and different external field voltages show different transmittances. The transmittance control curve is as follows: Figure 2 shown.

[0058] Therefore, the transmittance can be controlled by using different external electric field voltages through electro-optical devices. Figure 2 As can be seen, the transmittance of the incident spectrum can be flexibly adjusted using electro-optical devices through an external electric field. Different drive voltages can produce multiple transmittance peaks across the entire spectral range. Furthermore, varying the external electric field voltage can separate the transmittance peak wavelengths with minimal overlap, which facilitates compressed spectrum measurement. A transmittance control system consisting of crossed polarizers and an electro-optic modulator, coupled with a photodetector, can form a compressed spectrum measurement device.

[0059] Assume that the spectral power distribution of the object to be measured is X (λ) When detected by the detector, the transmittance T of the electro-optic modulator (λ,V) The jth regulated spectral signal is detected by the detector, forming a special coded measurement, which can be described as

[0060]

[0061] Since the sensor samples discrete values, according to the principle of compressed sensing measurement, in order to perform compressed measurement analysis and inversion reconstruction, it is more convenient and easier to understand to express the sensing measurement process of Equation (6) in matrix form. The spectral signal is represented by x, and the number of spectral channels is set to N, so x satisfies x∈R N×1 ; The multiple measurement spectral signals are represented by y, and according to M measurements, the spectral measurement signal y satisfies y∈R M×1 Using these matrices, the measurement process can be described as:

[0062] y=Φx (7)

[0063] Where Φ∈R M×N Represents the measurement matrix. Based on compressed sensing theory, spectral signals can be reconstructed from M measurement data, which is less than the number of signal channels N. The key lies in utilizing the spectral transmittance characteristics under different external electric field voltages and the non-correlation of these spectral characteristics.

[0064] The design and implementation of the measurement matrix must consider the selection of a sparse basis. Once the sparse basis is determined, a suitable spectral transmittance encoding measurement matrix is ​​designed and selected in conjunction with non-correlation research. Electro-optical devices built using the electro-optic effect can achieve spectral transmittance control through an external electric field, thereby realizing flexible spectral transmittance encoding. Existing sparse methods include discrete cosine transform basis, wavelet transform basis, and learning dictionary. For spectral signal sparsity, wavelet transform bases such as Coif3, db4, sym2, and bior3.3 all exhibit good compression and sparsity performance. In the visible light range (0.38-0.78μm), based on the piecewise smoothness of the spectral signal, the wavelet sparse basis can achieve a compression and sparsity ratio of better than 3% for the spectral signal. Optimizing the sparse transform basis to minimize sparsity, and then optimizing the design of the measurement matrix to minimize the correlation of the measurement matrix, realizes compressed sensing measurement.

[0065] In order to select a pseudo-random measurement matrix with a small correlation coefficient that satisfies non-correlated measurement, this method adopts algorithms such as sequential floating forward selection (SFFS), sequential forward selection (SFS) and sequential backward selection (SBS) to select the most uncorrelated transmittance values ​​from the spectral electro-optical transmittance values ​​to form the measurement matrix.

[0066] Reasonable design of the non-correlation feature selection of the spectral transmittance encoding matrix is ​​the key to achieving this type of compressed spectral measurement. The spectral transmittance of the Mth most uncorrelated external electric field voltage is selected and used as the Mth measurement of the compressed spectral measurement. The transmittance measurement matrix Φ can be described as

[0067]

[0068] For the spectra to be measured with N channels, M external electric field voltages are used to obtain measurement data, where M < N. Therefore, it is necessary to measure the M external electric field voltages to make the measurement matrix as uncorrelated as possible. Combining Figure 3 with the transmittance encoding situation shown, it can be seen from Equation (8) that the measurement matrix Φ contains a large number of non-diagonal non-zero terms, which is particularly beneficial for uncorrelated random measurements. The measurement matrix in Equation (8) is very similar to a partial Fourier matrix in a typical compressive sensing measurement matrix. According to the actually selected electro-optic modulation device, an experiment for accurately calibrating the transmittance of the electro-optic device is carried out, and the transmittances with the least correlation in columns are selected from the calibration results under M external electric field voltages to achieve M highly uncorrelated measurements. In the visible light range, when the number of spectral measurement channels is selected as 1024 and the spectral resolution is about 0.4 nm, generally, the number of measurements M not less than 35 times can ensure high-precision reconstruction of the spectral signal and recovery of the original spectral signal with a high compression ratio.

[0069] The size (x, y, z) of the electro-optic modulator is selected as (2, 4, 40) mm, and the maximum driving voltage is about 2000 V, so that larger uncorrelated measurements can be obtained. The driving control of the electro-optic modulator uses an FPGA as a signal source to generate a square wave signal, which is amplified into a high-voltage driving signal by an LC resonant high-voltage driving circuit and drives the electro-optic modulator to work. In order to achieve high compression ratio and fast compressive sensing spectral measurement, the electro-optic modulator needs to perform transmittance encoding control dozens of times within a short time, that is, it needs to provide a driving voltage from 0 to thousands of volts to the electro-optic modulator within a short time, and at the same time, it is necessary to collect the corresponding output optical signals under each modulation voltage. By driving the electro-optic modulator with a periodic alternating voltage, it is easy to traverse all the driving voltages required for uncorrelated measurements within a short time (half of the driving period), and efficient driving control can also be achieved. At the same time, a dual-channel AD acquisition system design is used to realize the corresponding measurement and acquisition of the driving voltage and its transmittance-encoded optical signal, ensuring efficient and high-precision compressive spectral measurement.

[0070] AD1 and AD2 are respectively used for collecting the compressive spectral measurement signal and the encoded driving signal. The compressive spectral measurement signal after AD1 conversion is represented by y. The original spectral signal x of the radiation target can be sparse, and the spectral signals of N channels are sparsely represented as x = Ψα, where α is the K-sparse vector (containing K << N non-zero elements) after the spectral signal is sparse, and Ψ is the sparse matrix. According to the theoretical framework of compressive sensing, Equation (7) can be rewritten as

[0071] y = Φx = ΦΨα = Aα (9)

[0072] In the above formula, the sensing matrix A = ΦΨ is determined by the sparse matrix Ψ and the measurement matrix Φ. According to the compressed sensing theory, the determined sparse matrix Ψ is combined with the measurement signal y, and then the inverse problem of formula (9) is solved. By finding the optimal spectral sparse signal Then the spectrum signal to be measured is correctly recovered from the sparse signal Among them, the spectral reconstruction algorithm uses the reconstruction time, reconstruction error, number of measurements and reconstruction probability as evaluation indicators to optimize the spectral reconstruction method. The orthogonal matching pursuit method (OMP), spectral sparsity K-adaptive matching pursuit (SAMP) optimization algorithm, and iterative soft threshold algorithm (IST) and two-step iterative shrinkage algorithm (TwIST) can be used for compressed sensing spectral reconstruction to achieve a larger compression ratio and higher precision spectral compressed sensing measurement.

[0073] The above only describes in detail the preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the purpose of the present invention, and various changes should be included in the scope of protection of the present invention.

Claims

1. A compressed sensing spectroscopy measurement device with electro-optical transmittance coding, characterized by: The invention comprises a collimating lens (3), a polarizer (4), an electro-optical modulator (5), an analyzer (6), a converging lens (7) and a photodetector (9) which are arranged in sequence, wherein the photodetector (9) is connected to an FPGA control and data acquisition module (12), the FPGA control and data acquisition module (12) is connected to the electro-optical modulator (5) via an LC resonant high-voltage drive circuit (10), and the FPGA control and data acquisition module (12) is connected to a computer (11); after the input of the light source to be measured is collimated, the incident light is converted into linearly polarized light after passing through the polarizer (4), and after being electro-optically modulated, it is emitted through the analyzer to achieve transmittance modulation with electro-optical modulation, and the compressed spectrum measurement signal output by the photodetector (9) and the coded drive signal output by the LC resonant high-voltage drive circuit (10) are collected by the FPGA control and data acquisition module (12); the FPGA control and data acquisition module (12) comprises an FPGA core chip, a first signal acquisition unit and a second signal acquisition unit, and the light The electric detector (9) is connected to the FPGA core chip through the first signal acquisition unit, and the LC resonant high-voltage driving circuit (10) is connected to the FPGA core chip through the second signal acquisition unit. The FPGA core chip controls the operation of the first signal acquisition unit and the second signal acquisition unit, thereby realizing one-to-one synchronous acquisition of the measurement light signal and the coded drive control voltage signal, and achieving synchronous measurement of the drive voltage and the compressed spectrum signal. The electro-optical modulator (5) is a lithium niobate transverse electro-optical modulator, and its electro-optical crystal adopts an X-cut lithium niobate electro-optical crystal and is placed between orthogonal polarizers. The transverse electro-optical effect under the action of an external electric field is used to realize intensity regulation and direct encoding of the compressed sensing spectrum measurement in the spectral dimension. The optical fiber coupler (2) and the optical fiber coupler (8) are also included. The optical fiber coupler (2) is arranged in front of the collimating lens (3), and the optical fiber coupler (8) is arranged behind the converging lens (7). The light source to be measured is input through optical fiber coupling, and the compressed measurement spectrum signal is output through optical fiber coupling.

2. The compressed sensing spectroscopy measurement device with electro-optical transmittance coding according to claim 1, characterized in that: The size of the X-cut lithium niobate electro-optical crystal is 2×4×40 mm, and an electric field is applied along the x-direction of the crystal, and light is transmitted along the z-axis direction of the crystal.

3. The measuring method adopted by the measuring device according to claim 1, characterized in that: The following steps are involved: S1. Build a spectrum measurement device; S2. Select an appropriate sparse basis and, based on the measurement spectral range and resolution requirements, use sequential floating forward selection, sequential forward selection, or sequential backward selection to implement transmittance measurement matrix encoding and determine the encoding voltage; S3, according to the driving voltage requirements of S2, traverse all coded driving voltages; S4, collecting the encoding voltage and the compressed spectrum measurement signal in a one-to-one correspondence; S5. Apply the orthogonal matching pursuit algorithm, the sparsity adaptive matching pursuit algorithm or the iterative soft threshold algorithm, and the two-step iterative shrinkage algorithm to achieve high compression ratio, high speed and high precision spectral reconstruction.

4. The measuring method according to claim 3, wherein: Spectral signal sparsification is achieved using discrete cosine basis, wavelet basis and learning dictionary, and the spectral signal sparsification ratio of the original spectral signal is better than 3%.

5. The measurement method according to claim 3, wherein: The spectrum measurement device in S1 collimates the light source to be measured, and the incident light is converted into linearly polarized light after passing through the polarizer. The angle between the direction of the linearly polarized light and the principal axis of the electro-optical refractive index is 45°. After electro-optical modulation, the light is emitted through the analyzer. The electro-optic modulator is a lithium niobate transverse electro-optic modulator. The electro-optic crystal is an x-cut crystal. Light is transmitted along the z-axis and an electric field is applied along the x-axis. Under the action of the transverse electro-optic effect, the two refractive index principal axes of the lithium niobate electro-optic crystal rotate 45 degrees and change in size. A transmittance control system consisting of orthogonal polarizers and an electro-optical modulator is used to form a compressed spectrum measurement device together with a photodetector.

6. The measurement method according to claim 3, wherein: A periodic AC voltage is used to drive the electro-optic modulator, and the driving voltage required for all non-correlated measurements is traversed in a short time. A dual-channel AD acquisition system is used, and the dual-channel AD operation is controlled by FPGA.

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