Phase-controlled array liquid crystal spectrometer and measurement method thereof

Abstract

The present invention provides a phase-modulation array liquid crystal spectrometer and a measurement method thereof, wherein the spectrometer comprises: a light source system, a phase modulation system, and a detector system; the phase modulation system comprises: a beam splitter, a row-oriented liquid crystal phase modulation array, and a column-oriented liquid crystal phase modulation array; the light source system is configured to emit a linearly polarized light beam, which is incident on the beam splitter and split into a reflected light beam and a transmitted light beam. The reflected light beam and the transmitted light beam are respectively incident on the row-oriented liquid crystal phase modulation array and the column-oriented liquid crystal phase modulation array, where they are reflected again to produce a preset optical path difference. The reflected light beam and the transmitted light beam return to the beam splitter, where they are superimposed and interfere with each other to produce an interference light beam; the interference light beam is incident on the detector system to obtain an interference image sequence, thereby acquiring spectral information of the linearly polarized light beam. The present invention solves the problems of low reliability, large size and weight, and poor real-time performance caused by mechanical scanning of moving mirror scanning Fourier transform spectrometers.

Description

Technical Field

[0001] The present invention relates to the field of spectral technology, and in particular to a phase-modulated array liquid crystal spectrometer and a measurement method thereof. Background Art

[0002] Spectroscopic technology can obtain information about the composition and content of target substances. It has been increasingly applied in fields such as physical experiments, chemical analysis, biological characterization, medical testing, and ecological and environmental protection, and has played a vital role in the exploration and discovery of new materials, new energy sources, and the unknown world. To obtain the spectral characteristics of the target, the detected complex light must be spectrally decomposed. Currently, commonly used spectroscopic instruments mainly use filter spectroscopy, prism spectroscopy, grating spectroscopy, and interference spectroscopy. Among them, Fourier transform spectroscopy, which uses interference spectroscopy, has become a high-end instrument in many application fields due to its advantages such as multi-channel, high throughput, accurate wavenumber, and low stray light.

[0003] In recent years, with the emergence and development of emerging scientific and technological fields such as space exploration, aerial remote sensing, Earth surveying, atmospheric monitoring, and military reconnaissance, the specialized applications and environments of these instruments have created an urgent need for miniaturized, static Fourier transform spectrometers. This escalating demand has led to insurmountable technical bottlenecks in conventional Fourier transform spectrometers. Currently, the Fourier transform spectrometers commonly used in laboratories employ a time-modulated interferometer structure, where a moving mirror scans the interferometer to generate an optical path difference to obtain spectral information. These instruments incorporate a high-precision moving mirror scanning mechanism for precise sampling of the interferogram. This mechanism is complex to manufacture, sensitive to vibration, and demanding in its operating environment. Furthermore, the moving mirror scanning mechanism is large and heavy. Furthermore, the use of a beam splitter for light separation results in half the energy loss, reducing system stability and reliability, making it unsuitable for aerospace applications such as meteorological observation and atmospheric remote sensing. This, in turn, limits its application in high-tech fields such as space exploration, meteorological remote sensing, and military reconnaissance. Summary of the Invention

[0004] In view of the above-mentioned problems, the present invention aims to provide a phase-modulated array liquid crystal spectrometer and its measurement method. By adjusting the row and column drive voltage distributions on two liquid crystal phase-modulated arrays, the long axis pointing angles of the liquid crystal molecules in each liquid crystal phase-modulated unit are changed, thereby regulating the row and column spatial distribution of the refractive index of each control unit in the two liquid crystal phase-modulated arrays, thereby forming an optical path difference array with a specific spatial distribution. The phase-modulated array liquid crystal spectrometer proposed by the present invention avoids the moving mirror scanning mechanism of traditional Fourier transform spectrometers, improves the stability and reliability of the system, reduces the system size and weight, and enhances the real-time performance of spectral detection. It is characterized by miniaturization, static operation, good real-time performance, and strong environmental adaptability.

[0005] To achieve the above objectives, the present invention adopts the following specific technical solutions:

[0006] The present invention provides a phase-modulated array liquid crystal spectrometer, comprising: a light source system, a phase modulation system, and a detector system; the phase modulation system comprises: a beam splitter, a row-direction liquid crystal phase-modulation array, and a column-direction liquid crystal phase-modulation array;

[0007] The light source system is used to emit a linearly polarized light beam, which is incident on a beam splitter and is divided into a reflected light beam and a transmitted light beam. The reflected light beam and the transmitted light beam are respectively incident on a row-direction liquid crystal phase control array and a column-direction liquid crystal phase control array, where they are reflected again to produce a preset optical path difference. The reflected light beam and the transmitted light beam return to the beam splitter, where they are superimposed and interfered to produce an interference light beam. After the interference light beam is incident on a detector system, an interference image sequence is obtained to acquire the spectral information of the linearly polarized light beam.

[0008] Preferably, the light source system comprises: a light source, a collimator and a polarizer;

[0009] The light source is used to emit a scattered light beam, which is collimated by a collimator and becomes a parallel light beam incident on a polarizer. The polarizer is used to convert the parallel light beam into a linearly polarized light beam incident on a phase modulation system.

[0010] Preferably, the row-direction liquid crystal phase control array or the column-direction liquid crystal phase control array is composed of N strip-shaped liquid crystal phase control units; the row-direction liquid crystal phase control array and the column-direction liquid crystal phase control array are placed orthogonally to the beam splitter;

[0011] The reflected light beam is reflected by the beam splitter and then incident on the row-direction liquid crystal phase control array;

[0012] The transmitted light beam is incident on the column-shaped liquid crystal phase control array after being transmitted through the beam splitter.

[0013] Preferably, the row-direction liquid crystal phase control array or the column-direction liquid crystal phase control array comprises, from top to bottom, a transparent cover plate, an upper transparent electrode, an upper alignment film, a liquid crystal layer, a lower alignment film, a strip-shaped transparent electrode array, a reflective substrate, electrode leads, and a pin array;

[0014] The transparent cover plate serves as an optical window for the row-direction liquid crystal phase control array or the column-direction liquid crystal phase control array, and together with the reflective substrate forms a liquid crystal cell to fix the liquid crystal layer;

[0015] The upper transparent electrode and the strip transparent electrode array together constitute the driving electrode of the liquid crystal layer, and drive the liquid crystal layer after applying voltage; the strip transparent electrode array includes N strip transparent electrodes;

[0016] The liquid crystal layer is a nematic liquid crystal, and the upper and lower alignment films are used to align the nematic liquid crystal molecules in the liquid crystal layer;

[0017] The pin array is pins led out from the strip transparent electrode array, and each pin is connected one-to-one with a strip transparent electrode in the strip transparent electrode array through an electrode lead.

[0018] Preferably, directions of the strip transparent electrodes in the strip transparent electrode arrays in the row-direction liquid crystal phase control array and the column-direction liquid crystal phase control array are perpendicular to each other.

[0019] Preferably, the nematic liquid crystal molecules in the liquid crystal layer of the stripe-shaped liquid crystal phase control unit loaded with different driving voltages have different long axis pointing inclination angles;

[0020] Different nematic liquid crystal molecule long axis pointing inclination angles correspond to different refractive indices;

[0021] The extraordinary light refractive index of the i-th row-direction stripe liquid crystal phase control unit in the row-direction liquid crystal phase control array is The equivalent refractive index is

[0022] The extraordinary refractive index of the jth columnar stripe liquid crystal phase control unit in the columnar liquid crystal phase control array is The equivalent refractive index is

[0023] Wherein, θ(i) is the long axis pointing inclination angle of the nematic liquid crystal molecules of the i-th strip-shaped liquid crystal phase control unit in the row-direction liquid crystal phase control array;

[0024] θ(j) is the long axis pointing inclination angle of the nematic liquid crystal molecules in the j-th stripe liquid crystal phase control unit of the nematic liquid crystal phase control array;

[0025] i=0, 1, 2…N-1; j=0, 1, 2…N-1;

[0026] n o 、n e are the refractive indices of ordinary light and extraordinary light in nematic liquid crystal when there is no voltage, respectively.

[0027] Preferably, the reflected light beam and the transmitted light beam travel through different optical paths when respectively transmitting in different strip-shaped liquid crystal phase control units in the row-direction liquid crystal phase control array and the column-direction liquid crystal phase control array:

[0028] The optical path of the reflected light beam in the i-th stripe liquid crystal phase control unit of the row-direction liquid crystal phase control array is OP x (i)=2n(i)L x ;

[0029] The optical path of the transmitted light beam in the jth stripe liquid crystal phase control unit of the column-oriented liquid crystal phase control array is OPy (j)=2n(j)L y .

[0030] Preferably, the detector system comprises: a beam reduction system and an area array detector;

[0031] The beam reduction system is a dual-telecentric relay imaging system. After the interfering beam is refracted by the beam reduction system, an interference image array is formed on the area array detector. In the interference image array, the optical path difference between the two beams corresponding to the (i, j)th image element when interference occurs is:

[0032] δ(i,j)=OP y (j)-OP x (i)=2[n(j)L y -n(i)L x ]

[0033] The spectral information of the linearly polarized light beam is obtained by performing discrete Fourier transform demodulation on the interference image array.

[0034] Preferably,

[0035] When the adjacent strip-shaped liquid crystal phase control units in the row-direction liquid crystal phase control array and the column-direction liquid crystal phase control array have the same refractive index difference Δn x =Δn y =Δn:

[0036] The liquid crystal layer thickness Lx of the row-direction liquid crystal phase control array and the liquid crystal layer thickness Ly of the column-direction liquid crystal phase control array satisfy the following relationship:

[0037]

[0038] When the row-direction liquid crystal phase control array and the column-direction liquid crystal phase control array have the same liquid crystal layer thickness L x =L y =L:

[0039] The refractive index difference Δn between adjacent strip-shaped liquid crystal phase control units in the row-oriented liquid crystal phase control array x The refractive index difference Δn between the adjacent stripe-shaped liquid crystal phase control units and the column-shaped liquid crystal phase control array y The following relationship is satisfied:

[0040]

[0041] Among them, λ min is the minimum wavelength in a linearly polarized beam.

[0042] The present invention also provides a measurement method for a phase-controlled array liquid crystal spectrometer, which is characterized by comprising the following steps:

[0043] S1. The light source system emits a linearly polarized beam which is incident on the beam splitter and is split into an identical reflected beam and a transmitted beam by the beam splitter.

[0044] S2, the reflected light beam and the transmitted light beam are respectively reflected by the row-direction liquid crystal phase control array and the column-direction liquid crystal phase control array and then return to the beam splitter, and superimpose interference on the output surface of the beam splitter to form an interference beam;

[0045] S3. The interference beam is incident on the detector system to obtain an interference image array, and then the spectral information of the linearly polarized beam is obtained.

[0046] Compared to existing technologies, the present invention utilizes two orthogonal one-dimensional liquid crystal phase control arrays. By adjusting the driving voltage on the strip-shaped transparent electrodes of each phase control unit, the long-axis pointing angle of the liquid crystal molecules in each phase control unit is changed, thereby modulating the refractive index of each phase control unit, thereby forming a two-dimensional distribution of optical path differences in the lateral space. An area array detector is used to acquire the interferogram signal of all sampled optical path differences, eliminating the need for time scanning. This achieves synchronous sampling of the interferogram information and improves the real-time performance of the system. This solves the problems of low reliability, large size and weight, and poor real-time performance associated with mechanical scanning in moving-mirror scanning Fourier transform spectrometers. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 3 is a structural diagram of a phase-modulated array liquid crystal spectrometer provided according to an embodiment of the present invention.

[0048] Figure 2 1 is a schematic structural diagram of a liquid crystal phase control array in a phase control array liquid crystal spectrometer provided according to an embodiment of the present invention.

[0049] Figure 3 1 is a schematic structural diagram of a liquid crystal phase control unit in a phase control array liquid crystal spectrometer provided according to an embodiment of the present invention.

[0050] Figure 4 Schematic diagram of the distribution of driving voltage applied to a row-wise liquid crystal phase control array in a phase control array liquid crystal spectrometer provided according to an embodiment of the present invention.

[0051] Figure 5 Schematic diagram of the distribution of driving voltage applied to a column-oriented liquid crystal phase control array in a phase control array liquid crystal spectrometer provided according to an embodiment of the present invention.

[0052] Figure 6 The figure is a flow chart of a measurement method of a phase-controlled array liquid crystal spectrometer provided according to an embodiment of the present invention.

[0053] Figure 7It is a flowchart of a phase-modulated array liquid crystal spectrometer measurement method provided according to an embodiment of the present invention.

[0054] The figures include: light source 1, collimator 2, polarizer 3, beam splitter 4, row-direction liquid crystal phase control array 5, column-direction liquid crystal phase control array 6, beam reduction system 7, area array detector 8, transparent cover 9, upper transparent electrode 10, upper orientation film 11, liquid crystal layer 12, lower orientation film 13, strip transparent electrode array 14, reflective substrate 15, electrode leads 16, pin array 17, driving voltage 18, reflected light wavefront distribution 19 and nematic liquid crystal molecules 20. DETAILED DESCRIPTION

[0055] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, identical modules are denoted by identical reference numerals. In the case of identical reference numerals, their names and functions are also identical. Therefore, their detailed description will not be repeated.

[0056] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0057] Figure 1 The structure of a phase-controlled array liquid crystal spectrometer provided according to an embodiment of the present invention is shown.

[0058] like Figure 1 As shown, the phase-modulated array liquid crystal spectrometer provided by the embodiment of the present invention includes: a light source system, a phase modulation system and a detector system.

[0059] The light source system is used to emit a linearly polarized light beam; the light source system includes: a light source 1, a collimator 2 and a polarizer 3.

[0060] Light source 1 emits a scattered light beam, which is collimated by collimator 2 and becomes a parallel light beam incident on polarizer 3. Polarizer 3 contains a polarizer whose polarization direction is parallel to the incident plane of the parallel light beam, converting the parallel light beam into a linearly polarized light beam incident on the phase modulation system.

[0061] The phase modulation system includes: a beam splitter 4 , a row-direction liquid crystal phase modulation array 5 , and a column-direction liquid crystal phase modulation array 6 .

[0062] The linearly polarized light beam is incident on the beam splitter 4 , which is placed at 45° to the optical axis of the linearly polarized light beam, and evenly splits the incident linearly polarized light beam into a reflected light beam and a transmitted light beam with equal energy.

[0063] The reflected light beam is reflected by the beam splitter 4 and then incident on the row-direction liquid crystal phase control array 5;

[0064] The transmitted light beam is incident on the column-oriented liquid crystal phase control array 6 after being transmitted by the beam splitter 4;

[0065] The row-direction liquid crystal phase control array 5 and the column-direction liquid crystal phase control array 6 are placed in a mirror-orthogonal manner relative to the beam splitter 4 .

[0066] Figure 2 A schematic structural diagram of a liquid crystal phase control array in a phase control array liquid crystal spectrometer provided according to an embodiment of the present invention is shown.

[0067] like Figure 2 As shown, both the row-oriented liquid crystal phase control array 5 and the column-oriented liquid crystal phase control array 6 include N strip-shaped transparent electrodes, and the thicknesses of the liquid crystal layer 12 are Lx and Ly, respectively. Each strip-shaped transparent electrode in the strip-shaped transparent electrode array 14 corresponds to a strip-shaped liquid crystal phase control unit. Therefore, both the row-oriented liquid crystal phase control array 5 and the column-oriented liquid crystal phase control array 6 are composed of N strip-shaped liquid crystal phase control units.

[0068] The effective width of each strip of transparent electrode corresponding to the strip of liquid crystal phase control unit is a, and the effective length of each strip of liquid crystal phase control unit is N×a. The liquid crystal layer thickness of the row-oriented liquid crystal phase control array is Lx, and the liquid crystal layer thickness of the column-oriented liquid crystal phase control array is Ly.

[0069] Figure 3 A schematic structural diagram of a liquid crystal phase control unit in a phase control array liquid crystal spectrometer provided according to an embodiment of the present invention is shown.

[0070] like Figure 3 As shown, the row-direction liquid crystal phase control array 5 or the column-direction liquid crystal phase control array 6 includes, from top to bottom, a transparent cover plate 9, an upper transparent electrode 10, an upper alignment film 11, a liquid crystal layer 12, a lower alignment film 13, a strip-shaped transparent electrode array 14, a reflective substrate 15, electrode leads 16, and a pin array 17;

[0071] The transparent cover plate 9 serves as an optical window for the row-oriented liquid crystal phase modulation array 5 or the column-oriented liquid crystal phase modulation array 6. Together with the reflective substrate 15, it forms a liquid crystal cell, securing the liquid crystal layer 12 therebetween. The transparent cover plate 9 is made of a transparent material such as glass, quartz, or sapphire, and is coated with an antireflection coating on both its top and bottom surfaces.

[0072] The upper transparent electrode 10 and the strip-shaped transparent electrode array 14 together form a driving electrode of the liquid crystal layer 12, and apply voltage to drive the liquid crystal layer 12. The material of the upper transparent electrode 10 is indium tin oxide.

[0073] The upper alignment film 11 aligns the nematic liquid crystal molecules 20 and can be formed by printing on a transparent cover plate using a polyimide polymer film.

[0074] The material of the liquid crystal layer 12 is nematic liquid crystal. When no driving voltage is applied, the nematic liquid crystal molecules 20 are arranged horizontally in the liquid crystal layer 12. When a driving voltage is applied, the long axis of the nematic liquid crystal molecules 20 points to the direction of the electric field and appears upright in the liquid crystal layer 12.

[0075] The lower alignment film 13 has the same function as the upper alignment film 11 , which is to orient the nematic liquid crystal molecules 20 . The lower alignment film 13 can be formed by printing on a transparent substrate using a polyimide polymer film.

[0076] The stripe transparent electrode array 14, together with the upper transparent electrode 10, forms the driving electrodes for the liquid crystal layer 12, applying a voltage to the liquid crystal layer 12 for distributed drive. The number of stripe transparent electrodes in the stripe transparent electrode array 14 is N, with a width b slightly smaller than a and a length of N × a. The electrodes of the stripe transparent electrode array 14 are made of indium tin oxide and are formed on a reflective substrate 15 by photolithography and etching.

[0077] The strip transparent electrodes in the strip transparent electrode arrays 14 within the row-direction liquid crystal phase control array 5 and the column-direction liquid crystal phase control array 6 are oriented perpendicularly to each other. That is, the strip transparent electrodes in the row-direction liquid crystal phase control array 5 are oriented along the x-direction, while the strip transparent electrodes in the column-direction liquid crystal phase control array 6 are oriented along the y-direction.

[0078] The reflective substrate 15 and the transparent cover 9 together form a liquid crystal cell, fixing the liquid crystal layer 12 in the middle and reflecting the light beam. It is made of transparent materials such as glass, quartz, and sapphire, with an anti-reflection film evaporated on the upper surface and a high-reflection film evaporated on the lower surface.

[0079] The electrode leads 16 are used to lead out the strip-shaped transparent electrode array 14 , and each lead corresponds to a strip-shaped transparent electrode in the strip-shaped transparent electrode array 14 .

[0080] The pin array 17 is a pin array for leading out pins of the strip-shaped transparent electrode array. Each pin is connected to a strip-shaped transparent electrode in the strip-shaped transparent electrode array 14 through an electrode lead 16 .

[0081] The driving voltage 18 is the applied voltage loaded on each pin.

[0082] The reflected light wavefront 19 is the wavefront distribution of the light beam reflected after the driving voltage 18 is applied.

[0083] Figure 4 A schematic diagram of the distribution of the applied driving voltage of the row-direction liquid crystal phase control array in the phase control array liquid crystal spectrometer provided according to an embodiment of the present invention is shown.

[0084] Figure 5 A schematic diagram of the distribution of the applied driving voltage of the column-oriented liquid crystal phase control array in the phase control array liquid crystal spectrometer provided according to an embodiment of the present invention is shown.

[0085] like Figure 4 and 5 As shown, different driving voltages V are applied to the strip transparent electrodes of each strip liquid crystal phase control unit; the driving voltage applied to the strip transparent electrodes of the i-th strip liquid crystal phase control unit in the row-direction liquid crystal phase control array 5 is V(i), and the driving voltage applied to the strip transparent electrodes of the j-th strip liquid crystal phase control unit in the column-direction liquid crystal phase control array 6 is V(j);

[0086] The nematic liquid crystal molecules in the liquid crystal layer of the strip liquid crystal phase control unit loaded with different driving voltages have different long-axis pointing inclination angles. The long-axis pointing inclination angle of the nematic liquid crystal molecules of the i-th strip liquid crystal phase control unit in the row-direction liquid crystal phase control array is θ(i), and the long-axis pointing inclination angle of the nematic liquid crystal molecules of the j-th strip liquid crystal phase control unit in the column-direction liquid crystal phase control array is θ(j).

[0087] Different nematic phase liquid crystal molecule long axis pointing inclination angles correspond to different refractive indices. Therefore, the extraordinary light refractive index of the i-th row-direction strip liquid crystal phase control unit in the row-direction liquid crystal phase control array is The equivalent refractive index is The extraordinary refractive index of the jth columnar stripe liquid crystal phase control unit in the columnar liquid crystal phase control array is The equivalent refractive index is

[0088] Among them, n o 、n e are the refractive indices of ordinary light and extraordinary light in nematic liquid crystal when there is no voltage, respectively.

[0089] Therefore, the reflected light beam and the transmitted light beam travel through different optical path lengths when they are transmitted in different strip-shaped liquid crystal phase control units in the row-direction liquid crystal phase control array 5 and the column-direction liquid crystal phase control array 6, respectively. The optical path length traveled by the reflected light beam in the i-th strip-shaped liquid crystal phase control unit in the row-direction liquid crystal phase control array is OP x (i)=2n(i)L x The optical path of the transmitted light beam in the jth stripe liquid crystal phase control unit of the column-oriented liquid crystal phase control array is OP y (j)=2n(j)L y .

[0090] The reflected light beam and the transmitted light beam are respectively reflected by the row-direction liquid crystal phase control array 5 and the column-direction liquid crystal phase control array 6 and then return to the beam splitter 4. After superposition interference occurs at the output surface of the beam splitter 4, an interference light beam is formed and incident on the detector system.

[0091] The detector system includes: a beam reduction system 7 and an array detector 8.

[0092] The beam reduction system 7 is a dual telecentric relay imaging system.

[0093] After being refracted by the beam reduction system 7, the interference light beam forms an interference image array on the area array detector, thereby obtaining the spectral information of the linearly polarized light beam.

[0094] In the interference image array, the optical path difference between the two beams when interference occurs corresponding to the (i, j)th image unit is:

[0095] δ(i,j)=OP y (j)-OP x (i)=2[n(j)L y -n(i)L x ]

[0096] Therefore, the interference intensity corresponding to the (i, j)th image unit is:

[0097]

[0098] By performing discrete Fourier transform demodulation on the interference image array, the spectral information of the linearly polarized light beam can be restored.

[0099] In order to achieve equal-interval sampling, the adjacent strip-shaped liquid crystal phase control units in the row-direction liquid crystal phase control array have the same refractive index difference Δn x , and the adjacent strip-shaped liquid crystal phase control units in the column-oriented liquid crystal phase control array also have the same refractive index difference Δn y .

[0100] In order to form a continuous optical path difference sequence, the two liquid crystal phase control arrays must satisfy the mutual compensation of optical paths, which can be achieved in two ways.

[0101] One way is to achieve optical path complementarity by matching the thickness of the liquid crystal layers of the two liquid crystal phase control arrays, so that the thickness of the liquid crystal layer of one liquid crystal phase control array is N times the thickness of the liquid crystal layer of the other liquid crystal phase control array, that is, L y =NL x At this time, the adjacent strip-shaped liquid crystal phase control units of the two liquid crystal phase control arrays have the same refractive index difference Δn x =Δn y=Δn; Another way is to keep the two liquid crystal phase control arrays with the same liquid crystal layer thickness L x =L y =L, optical path complementation is achieved by matching the refractive index difference of adjacent strip-shaped liquid crystal phase control units of two liquid crystal phase control arrays, so that the refractive index difference of adjacent strip-shaped liquid crystal phase control units of one liquid crystal phase control array is N times the refractive index difference of adjacent strip-shaped liquid crystal phase control units of the other liquid crystal phase control array, that is, Δn y =NΔn x .

[0102] When the first optical path complementation method is adopted, the adjacent strip-shaped liquid crystal phase control units of the two liquid crystal phase control arrays have the same refractive index difference Δn x =Δn y =Δn, the relationship between the thickness of the liquid crystal layer of the two liquid crystal phase control arrays is L y =NL x , at this time the optical path difference sampling array is:

[0103] δ(i,j)=2(jΔnL y -iΔnL x )=2ΔnL x (jN-i)

[0104] In order to avoid spectral aliasing during the spectrum restoration process, the optical path difference sampling interval must be less than or equal to twice the minimum wavelength of the optical signal, that is:

[0105]

[0106] Therefore, the refractive index difference between adjacent strip-shaped liquid crystal phase control units of two liquid crystal phase control arrays must satisfy the following relationship:

[0107]

[0108] At this point, the restored spectrum is in the form of:

[0109]

[0110] According to the discrete Fourier transform theory, the spectral resolution is the inverse of the maximum optical path difference, that is, Therefore, the thickness of the liquid crystal layer of the two liquid crystal phase control arrays satisfies the following relationship:

[0111]

[0112] At the same time, the number of sampling points needs to satisfy the relationship where n max 、n min are the maximum and minimum refractive index values ​​that the liquid crystal material can achieve, respectively.

[0113] When the second optical path complementary method is adopted, the two liquid crystal phase control arrays have the same liquid crystal layer thickness L x =L y = L, the relationship between the refractive index difference between adjacent strip-shaped liquid crystal phase control units in two liquid crystal phase control arrays is Δn y =NΔn x , at this time the optical path difference sampling array is:

[0114] δ(i,j)=2(jΔn y L-iΔn x L)=2Δn x L(jN-i)

[0115] In order to avoid spectral aliasing during the spectrum restoration process, the optical path difference sampling interval must be less than or equal to twice the minimum wavelength of the optical signal, that is:

[0116]

[0117] Therefore, the refractive index difference between adjacent strip-shaped liquid crystal phase control units of two liquid crystal phase control arrays must satisfy the following relationship:

[0118]

[0119] At this point, the restored spectrum is in the form of:

[0120]

[0121] Where ν is the wave number of the interference light signal. For light with a wavelength of λ, ν = 1 / λ.

[0122] According to the discrete Fourier transform theory, the spectral resolution is the inverse of the maximum optical path difference, that is, Therefore, the thickness of the liquid crystal layer of the two liquid crystal phase control arrays satisfies the following relationship:

[0123]

[0124] At the same time, the number of sampling points needs to satisfy the relationship where n max 、 n min are the maximum and minimum refractive index values ​​that the liquid crystal material can achieve, respectively.

[0125] Figure 6 A schematic flow chart of a phase-modulated array liquid crystal spectrometer measurement method according to an embodiment of the present invention is shown.

[0126] Figure 7 A flowchart of a phase-modulated array liquid crystal spectrometer measurement method according to an embodiment of the present invention is shown.

[0127] like Figure 6 and 7 As shown, the phase control array liquid crystal spectrometer measurement method provided by the embodiment of the present invention includes the following steps:

[0128] S1. A linearly polarized light beam emitted by the light source system is incident on the beam splitter and is split into an identical reflected beam and a transmitted beam by the beam splitter.

[0129] Fix the collimating mirror in the light source system on the platform base; use a divergent laser light source with a wavelength within the system's operating spectrum band as the incident light, and adjust the distance between the laser light source and the collimating mirror so that the laser light source emission point is located at the front focus of the collimating mirror to ensure that the output light is collimated and parallel;

[0130] Place the light source system polarizer in the parallel light path of the collimator and align it centrally. Adjust the polarization direction of the polarizer in the polarizer and use an analyzer to detect the polarization direction of the outgoing laser beam. If the polarization direction of the outgoing laser beam is not parallel to the light incident plane, continue to adjust the polarizer in the polarizer until the polarization direction of the outgoing laser beam is parallel to the light incident plane. Replace the laser light source with a broadband light source.

[0131] S2, the reflected light beam and the transmitted light beam are respectively reflected by the row-direction liquid crystal phase control array and the column-direction liquid crystal phase control array and then return to the beam splitter, and form an interference beam after superposition interference occurs on the output surface of the beam splitter.

[0132] Place the beam splitter in the output light path of the polarizer at an angle of 45° to the optical axis and align the center.

[0133] Place the row-direction liquid crystal phase control array in the reflected light path of the beam splitter and perform center alignment;

[0134] Place the columnar liquid crystal phase control array in the transmission light path of the beam splitter and perform center alignment;

[0135] Adjust the relative position between the row-directional liquid crystal phase control array and the column-directional liquid crystal phase control array, observe whether the row-directional liquid crystal phase control array and the column-directional liquid crystal phase control array are mirror-symmetrical relative to the beam splitter, and whether interference fringes are generated; if they are not in a mirror-symmetrical position or no interference fringes are generated, continue to adjust the relative position between the row-directional liquid crystal phase control array and the column-directional liquid crystal phase control array until the two liquid crystal phase control arrays are mirror-symmetrical relative to the beam splitter and stable interference fringes are generated.

[0136] Adjusting the driving voltage applied to each row unit of the row-wise liquid crystal phase control array so that adjacent row units have an equal refractive index difference;

[0137] Adjusting the driving voltage applied to each column of the column-oriented liquid crystal phase control array so that adjacent columns of the array have an equal refractive index difference;

[0138] The driving voltage distribution on each strip unit of the two liquid crystal phase control arrays is fixed.

[0139] S3. The interference beam is incident on the detector system to obtain an interference image array, and then the spectral information of the linearly polarized beam is obtained.

[0140] Place the beam reduction system in the detector system in the outgoing light path of the row-direction liquid crystal phase control array and perform center alignment; place the area array detector in the detector system at the image plane position of the beam reduction system, and adjust the position of the area array detector relative to the beam reduction system so that the interference fringes can be clearly imaged.

[0141] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

[0142] The above specific embodiments of the present invention do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A phase-controlled array liquid crystal spectrometer, characterized in that: include: Light source system, phase modulation system and detector system; The phase modulation system includes: a beam splitter, a row-direction liquid crystal phase modulation array, and a column-direction liquid crystal phase modulation array; The light source system is configured to emit a linearly polarized light beam, which is incident on the beam splitter and split into a reflected light beam and a transmitted light beam. The reflected light beam and the transmitted light beam are respectively incident on the row-direction liquid crystal phase control array and the column-direction liquid crystal phase control array, where they are reflected again to generate a preset optical path difference. The reflected light beam and the transmitted light beam return to the beam splitter, where they are superimposed and interfere with each other to generate an interference light beam. The interference light beam is incident on a detector system to obtain an interference image sequence, thereby acquiring spectral information of the linearly polarized light beam. The row-direction liquid crystal phase control array or the column-direction liquid crystal phase control array is composed of N strip-shaped liquid crystal phase control units; the row-direction liquid crystal phase control array and the column-direction liquid crystal phase control array are placed orthogonally to the beam splitter; the reflected light beam is incident on the row-direction liquid crystal phase control array after being reflected by the beam splitter; the transmitted light beam is incident on the column-direction liquid crystal phase control array after being transmitted by the beam splitter; The nematic phase liquid crystal molecules in the liquid crystal layer of the strip-shaped liquid crystal phase control unit loaded with different driving voltages have different long axis pointing inclination angles; Different nematic liquid crystal molecule long axis pointing inclination angles correspond to different refractive indices; The extraordinary light refractive index of the i-th row-direction stripe liquid crystal phase control unit in the row-direction liquid crystal phase control array is , the equivalent refractive index is ; The extraordinary refractive index of the jth columnar stripe liquid crystal phase control unit in the columnar liquid crystal phase control array is , the equivalent refractive index is ; Wherein, θ(i) is the long axis pointing tilt angle of the nematic phase liquid crystal molecules of the i-th strip liquid crystal phase control unit of the row-oriented liquid crystal phase control array; θ(j) is the long axis pointing tilt angle of the nematic phase liquid crystal molecules of the j-th strip liquid crystal phase control unit of the column-oriented liquid crystal phase control array; i=0, 1, 2…N-1; j=0, 1, 2…N-1; n o 、n e are the refractive indices of ordinary light and extraordinary light in nematic liquid crystal when there is no voltage, respectively; When the adjacent strip-shaped liquid crystal phase control units in the row-direction liquid crystal phase control array and the column-direction liquid crystal phase control array have the same refractive index difference hour: The liquid crystal layer thickness Lx of the row-direction liquid crystal phase control array and the liquid crystal layer thickness Ly of the column-direction liquid crystal phase control array satisfy the following relationship: ， When the row-direction liquid crystal phase control array and the column-direction liquid crystal phase control array have the same liquid crystal layer thickness hour: The refractive index difference between adjacent strip-shaped liquid crystal phase control units in the row-direction liquid crystal phase control array The refractive index difference between the stripe-shaped liquid crystal phase control unit adjacent to the column-shaped liquid crystal phase control array The following relationship is satisfied: ， Among them, λ min is the minimum wavelength in the linearly polarized light beam.

2. The phase-controlled array liquid crystal spectrometer according to claim 1, characterized in that: The light source system includes: a light source, a collimator and a polarizer; The light source is used to emit a scattered light beam, which is collimated by the collimator and becomes a parallel light beam incident on the polarizer. The polarizer is used to convert the parallel light beam into a linearly polarized light beam incident on the phase modulation system.

3. The phase-controlled array liquid crystal spectrometer according to claim 1, characterized in that: The row-direction liquid crystal phase control array or the column-direction liquid crystal phase control array comprises, from top to bottom, a transparent cover plate, an upper transparent electrode, an upper alignment film, a liquid crystal layer, a lower alignment film, a strip-shaped transparent electrode array, a reflective substrate, electrode leads and a pin array; The transparent cover plate serves as an optical window of the row-direction liquid crystal phase modulation array or the column-direction liquid crystal phase modulation array, and together with the reflective substrate constitutes a liquid crystal cell to fix the liquid crystal layer; The upper transparent electrode and the strip-shaped transparent electrode array together constitute the driving electrode of the liquid crystal layer, and drive the liquid crystal layer after applying voltage; the strip-shaped transparent electrode array includes N strip-shaped transparent electrodes; The liquid crystal layer is a nematic liquid crystal, and the upper alignment film and the lower alignment film are used to align the nematic liquid crystal molecules in the liquid crystal layer; The pin array is pins led out from the strip-shaped transparent electrode array, and each pin is connected one-to-one with a strip-shaped transparent electrode in the strip-shaped transparent electrode array through the electrode lead.

4. The phase-controlled array liquid crystal spectrometer according to claim 3, characterized in that: The directions of the strip transparent electrodes in the row-direction liquid crystal phase regulation array and the strip transparent electrode array in the column-direction liquid crystal phase regulation array are perpendicular to each other.

5. The phase-controlled array liquid crystal spectrometer according to claim 1, characterized in that: The reflected light beam and the transmitted light beam travel through different optical paths when they are transmitted in different strip-shaped liquid crystal phase control units in the row-direction liquid crystal phase control array and the column-direction liquid crystal phase control array respectively. The optical path of the reflected light beam in the i-th strip-shaped liquid crystal phase control unit of the row-oriented liquid crystal phase control array is ; The optical path of the transmitted light beam in the j-th strip-shaped liquid crystal phase control unit of the column-shaped liquid crystal phase control array is .

6. The phase-modulated array liquid crystal spectrometer according to claim 5, characterized in that: The detector system includes: a beam reduction system and an array detector; The beam reduction system is a dual-telecentric relay imaging system. After the interference beam is refracted by the beam reduction system, an interference image array is formed on the area array detector. In the interference image array, the optical path difference between the two beams corresponding to the (i, j)th image element when interference occurs is: The spectrum information of the linearly polarized light beam is obtained by performing discrete Fourier transform demodulation on the interference image array.

7. A measurement method for a phase-modulated array liquid crystal spectrometer according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. The light source system emits a linearly polarized light beam which is incident on the beam splitter and is split by the beam splitter into an identical reflected light beam and a transmitted light beam; S2, the reflected light beam and the transmitted light beam are respectively reflected by the row-direction liquid crystal phase control array and the column-direction liquid crystal phase control array and then return to the beam splitter, and form an interference beam after superposition interference occurs on the exit surface of the beam splitter; S3. The interference light beam is incident on the detector system to obtain an interference image array, thereby acquiring spectral information of the linearly polarized light beam.

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