Reflection-type Fabry-Perot etalon array snapshot interference imaging spectrometer

Abstract

The invention relates to the field of spectral imaging, in particular to a reflective Fabry-Perot etalon array snapshot interference imaging spectrometer, which comprises a telescopic system, a micro-lens array, a beam splitter, a reflective Fabry-Perot etalon array and a detection system, and is characterized in that the telescopic system is used for collecting a target light field and carrying out view field limitation and collimation on the target light field; the micro lens array is used for performing array imaging on the straightened target light field; the beam splitter is used for transmitting the array imaging light beam; the reflective Fabry-Perot etalon array is composed of a substrate and a plurality of Fabry-Perot etalon units, wherein the thicknesses of medium cavities of the Fabry-Perot etalon units are in two-dimensional linear increase, and the step height differences between any two adjacent Fabry-Perot etalon units are the same. And the detection system is used for imaging the interference light field modulated by the reflective Fabry-Perot etalon array to obtain an interference image array. The invention has the advantages of small volume, light weight, compact structure, static state, stability, reliability and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of spectral imaging, and in particular relates to a reflective Fabry-Perot etalon array snapshot interferometric imaging spectrometer. Background Art

[0002] Fourier transform spectroscopy is a widely used measurement method for obtaining infrared spectra of target scenes. Its application range is very broad and has extended from the laboratory to the field of remote sensing. Most Fourier transform spectrometers use a time-modulated Michelson interferometer system to measure the time-modulated interference signal generated by the interaction between the incident spectrum and the Michelson interferometer system, and perform spectral demodulation through Fourier transform. In a Fourier transform infrared spectrometer based on a Michelson interferometer system, a moving mirror is used to sample the interference pattern in time. The moving mirror generates a time-varying optical path difference between the two beams by splitting the input beam. Under the illumination of monochromatic light, the detector responds to this time-varying optical path difference as a sinusoidal signal that changes with the optical path difference. By accurately measuring the change in the optical path difference, a reference laser signal is usually used to recover the wavelength information of the incident light from the sampled interference signal. The illumination of multiple wavelengths produces an added synthetic interference pattern, and the intensity of each wavelength, that is, the spectral information, can be recovered using Fourier transform. Since the Michelson interferometer system uses a high-precision precision moving mirror scanning mechanism to perform fine scanning of the optical path difference, the Fourier transform spectrometer based on the Michelson interferometer system is large in size, heavy in weight, difficult to integrate, and easily affected by the external environment. It is difficult to adapt to the application needs of new scientific and technological fields such as drones, micro-nano satellites, etc.

[0003] Compared with the Michelson interferometer system, the Fabry-Perot interferometer system has the advantages of compact structure, small size and light weight, so it is particularly suitable for applications such as drone-mounted and micro-nano satellite-mounted. Traditional Fabry-Perot interferometer systems are usually used as very narrow bandpass filters, and narrowband filtering is achieved by using very high reflectivity coatings. If a lower reflectivity coating is used on the surface of the Fabry-Perot cavity, the spectral transmission is essentially a sinusoidal curve, and the spectrum can be restored by Fourier transform. However, if the reflectivity of the coating is too low, the fringe contrast will be reduced, resulting in interference failure. Summary of the invention

[0004] In view of this, the present invention aims to provide a reflective Fabry-Perot etalon array snapshot interferometric imaging spectrometer to solve the technical problems of the existing Fourier transform spectrometer based on the Michelson interferometer system, such as large size, heavy weight, great integration difficulty and being easily affected by the external environment.

[0005] To achieve the above object, the technical solution created by the present invention is implemented as follows: A reflective Fabry-Perot etalon array snapshot interferometric imaging spectrometer comprises a telescope system, a microlens array, a beam splitter, a reflective Fabry-Perot etalon array and a detection system; wherein: The telescope system is used to collect the target light field and to limit and collimate the target light field; The microlens array is located in the collimation direction of the telescope system. The micro-imaging mirror array adopts an image-side telecentric optical path structure and is composed of M×N microlens units. The micro-imaging mirror array is used to perform array imaging on the collimated target light field. The beam splitter is located in the imaging light path of the microlens array and is used to transmit the array imaging light beam; The reflective Fabry-Perot etalon array is located on the image focal plane of the microlens. The reflective Fabry-Perot etalon array is composed of a substrate and M×N Fabry-Perot etalon units whose dielectric cavity thickness increases linearly in two dimensions. The thickness of each dielectric cavity corresponds to an optical path difference. The step height difference between any two adjacent Fabry-Perot etalon units in one direction is d, and the step height difference between any two adjacent Fabry-Perot etalon units in another direction is Md. Each Fabry-Perot etalon unit corresponds to a microlens unit. The detection system is located in the reflection direction of the beam splitter and is used to image the interference light field modulated by the reflective Fabry-Perot etalon array to obtain an interference image array.

[0006] Furthermore, the reflectivity of the two reflection interfaces of the dielectric cavity is 30% to 40%.

[0007] Furthermore, the substrate adopts a low-refractive index substrate or a metal substrate, and the Fabry-Perot etalon unit adopts a high-refractive index transparent medium layer; or, the substrate adopts a high-refractive index substrate or a metal substrate, and the Fabry-Perot etalon unit adopts a low-refractive index transparent medium layer, and a reflective film is plated on the upper surface of the low-refractive index transparent medium layer; or, the substrate adopts an opaque glass or plastic substrate, and a reflective film is plated on the upper surface of the opaque glass or plastic substrate, and the Fabry-Perot etalon unit adopts a low-refractive index transparent medium layer, and a reflective film is plated on the upper surface of the low-refractive index transparent medium layer.

[0008] Furthermore, the low refractive index substrate is a quartz, calcium fluoride, magnesium fluoride or sapphire dielectric material; the high refractive index transparent dielectric layer is a silicon dielectric material or a germanium dielectric material; the high refractive index substrate is a silicon dielectric material or a germanium dielectric material, the low refractive index transparent dielectric layer is any one of silicon dioxide, aluminum oxide, calcium fluoride, magnesium fluoride, yttrium fluoride, thorium fluoride, and cerium fluoride, and the reflective film is a silicon film or a germanium film.

[0009] Furthermore, the dielectric cavity thickness h(m,n) of the (m,n)th Fabry-Perot etalon unit is: .

[0010] Furthermore, for the incident broadband spectrum, the step height difference d satisfies the following relationship: ; Among them, λ min is the minimum wavelength of the broadband spectrum, θ max is the incident angle corresponding to the maximum aperture angle light in the dielectric cavity, J is the spectral harmonic order, and n0 is the dielectric refractive index of the Fabry-Perot etalon unit; For an incident narrowband spectrum, the step height difference d satisfies the following relationship: ; Among them, λ S is the shortest wavelength of the narrowband spectrum, λ L is the longest wavelength of the narrowband spectrum, k is the order of spectrum folding, and can be any integer less than or equal to .

[0011] Furthermore, the preparation process of the reflective Fabry-Perot etalon array is as follows: S1: providing a substrate with a lateral width of a and a longitudinal width of b, and polishing and cleaning the substrate; S2: evaporating a zero optical path difference medium layer of the medium cavity on the substrate, the thickness of the zero optical path difference medium layer is close to zero, and the lateral width and longitudinal width of the zero optical path difference medium layer are respectively the same as the lateral width and longitudinal width of the substrate; S3: vapor-depositing a longitudinal two-step dielectric layer of the dielectric cavity on the zero optical path difference dielectric layer, wherein the thickness of the longitudinal two-step dielectric layer is NMd / 2, the longitudinal width of the longitudinal two-step dielectric layer is b / 2, and the transverse width of the longitudinal two-step dielectric layer is a; S4: vapor-depositing a longitudinal four-step dielectric layer of the dielectric cavity on the longitudinal two-step dielectric layer, the thickness of the longitudinal four-step dielectric layer is NMd / 4, the longitudinal width of the longitudinal four-step dielectric layer is b / 4, and the transverse width of the longitudinal four-step dielectric layer is a, repeating step S4, in each vapor deposition process of the longitudinal step dielectric layer, the thickness of the longitudinal step dielectric layer is 1 / 2 of the previous time, and the longitudinal width of the longitudinal step dielectric layer is 1 / 2 of the previous time, until the step height difference of the longitudinal step dielectric layer is Md, and the longitudinal width of the longitudinal step dielectric layer is b / N; S5: evaporating a transverse two-step dielectric layer of the dielectric cavity on the longitudinal step dielectric layer, the thickness of the transverse two-step dielectric layer is Md / 2, the transverse width of the transverse two-step dielectric layer is a / 2, and the longitudinal width of the transverse two-step dielectric layer is b; S6: evaporate a transverse four-step dielectric layer of the dielectric cavity on the transverse two-step dielectric layer, the thickness of the transverse four-step dielectric layer is Md / 4, the transverse width of the transverse four-step dielectric layer is a / 4, and the longitudinal width of the transverse four-step dielectric layer is b. Repeat step S6. In each evaporation process of the transverse step dielectric layer, the thickness of the transverse step dielectric layer is 1 / 2 of the previous time, and the transverse width of the transverse step dielectric layer is 1 / 2 of the previous time, until the step height difference of the transverse step dielectric layer is d, and the transverse width of the transverse step dielectric layer is a / M.

[0012] Furthermore, the telescope system includes a telescope objective lens, a field stop and a collimator lens; wherein, The telescope objective is used to collect the target light field and image the target light field at the field aperture; The field diaphragm is located on both the image-side focal plane of the telescope objective and the object-side focal plane of the collimator. The field diaphragm is used to limit the field of view of the imaging of the target light field. The collimator is used to collimate the divergent light emitted by the target light field located at the field stop into parallel light.

[0013] Furthermore, the detection system includes a relay imaging mirror, a cold screen aperture and an array detector; wherein, The relay imaging mirror is located in the reflection direction of the beam splitter and adopts an object-side telecentric optical path structure, and is used to image the interference light field modulated by the reflective Fabry-Perot etalon array onto the area array detector; The cold screen diaphragm is located on the image-side focal plane of the relay imaging mirror and is used to limit the object-side numerical aperture; The area array detector is located at the image plane of the relay imaging mirror and is used to perform photoelectric conversion on the interference light field to obtain an interference image array.

[0014] Furthermore, the planar array detector is also used to perform image segmentation on the interference image array, dividing the interference image array into interference image units corresponding to each Fabry-Perot etalon unit; and arranging the interference image units in the order of the thickness of each Fabry-Perot etalon unit to form an interference image data cube, and performing a discrete Fourier transform operation on the interference image data cube with the optical path difference as the axis to obtain a spectral image data cube that varies with wavelength.

[0015] Compared with the prior art, the invention can achieve the following beneficial effects: The present invention adopts a Fabry-Perot etalon unit whose dielectric cavity thickness increases linearly in two dimensions to construct a reflective Fabry-Perot etalon array, replaces the precision moving mirror scanning mechanism in the traditional Fourier transform imaging spectrometer, simplifies and lightens the optical-mechanical structure of the Fourier transform imaging spectrometer, improves the stability and robustness of the Fourier transform imaging spectrometer, and has the advantages of small size, light weight, compact structure, static, stable, reliable, etc. At the same time, the incident interface of the reflective Fabry-Perot etalon array adopts a medium-low reflectivity, and the spectrum can be restored by Fourier transform, which reduces the difficulty of spectrum restoration in the traditional Fabry-Perot interference system. Through the coupled modulation transmission of the light field by the reflective Fabry-Perot etalon array and the microlens array, the synchronous measurement of the interference image data cube can be realized, thereby realizing the snapshot-type effective detection of the target scene image information and the spectral information, and improving the real-time performance of the multi-dimensional information detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings: Figure 1 It is a schematic diagram of the structure of the reflective Fabry-Perot etalon array snapshot interferometric imaging spectrometer according to the first embodiment of the present invention.

[0017] Figure 2 It is a schematic structural diagram of a reflective Fabry-Perot etalon array based on a high-refractive-index medium cavity as described in Example 1 of the present invention.

[0018] Figure 3 Schematic diagram of the spatial distribution of the dielectric cavity thickness of the reflective Fabry-Perot etalon array described in Example 1 of the present invention.

[0019] Figure 4 It is a schematic diagram of the preparation process of the reflection type Fabry-Perot etalon array described in Example 1 of the present invention.

[0020] Figure 5 It is a schematic diagram of the process of image spectrum inversion described in Example 1 of the present invention.

[0021] Figure 6 It is a schematic structural diagram of a reflective Fabry-Perot etalon array based on a low-refractive-index medium cavity as described in Example 2 of the present invention.

[0022] Figure 7 1 is a schematic diagram of the structure of a reflective Fabry-Perot etalon array snapshot interferometric imaging spectrometer according to Example 3 of the present invention.

[0023] Description of the accompanying drawings of Example 1: telescope objective 10, field aperture 20, collimator 30, microlens array 40, beam splitter 50, reflective Fabry-Perot etalon array 60, substrate 601, high refractive index transparent medium layer 602, relay imaging mirror 70, cold screen aperture 80, and area array detector 90.

[0024] Description of the reference numerals of Example 2: substrate 603 , low refractive index transparent medium layer 604 , and reflective film 605 .

[0025] Description of the reference numerals of Example 3: substrate 606 , low refractive index transparent medium layer 607 , and reflective film 608 . DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the invention more clear, the invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the invention and do not constitute a limitation of the invention.

[0027] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0028] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0029] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0030] The present invention will be described in detail below with reference to the drawings and in combination with embodiments.

[0031] The present invention provides a reflective Fabry-Perot etalon array snapshot interferometric imaging spectrometer, comprising a telescope system, a microlens array, a beam splitter, a reflective Fabry-Perot etalon array and a detection system; wherein the telescope system is used to collect a target light field, and to limit and collimate the target light field; the microlens array is located in the collimation direction of the telescope system, the micro-imaging mirror array adopts an image-side telecentric optical path structure, and is composed of M×N microlens units, and the micro-imaging mirror array is used to perform array imaging on the collimated target light field; the beam splitter is located in the imaging optical path of the microlens array, and is used to limit and collimate the array imaging light field; The reflective Fabry-Perot etalon array is located on the image focal plane of the microlens, and is composed of a substrate and M×N Fabry-Perot etalon units with dielectric cavities having a two-dimensional linearly increasing thickness. The thickness of each dielectric cavity corresponds to an optical path difference, and the step height difference between any two adjacent Fabry-Perot etalon units is the same, and each Fabry-Perot etalon unit corresponds to a microlens unit. The detection system is located in the reflection direction of the beam splitter, and is used to image the interference light field modulated by the reflective Fabry-Perot etalon array to obtain an interference image array.

[0032] The telescope system includes a telescope objective, a field diaphragm and a collimator; wherein the telescope objective is used to collect a target light field and image the target light field at the field diaphragm; the field diaphragm is located on the image-side focal plane of the telescope objective and on the object-side focal plane of the collimator at the same time, and the field diaphragm is used to limit the field of view of the imaging of the target light field; the collimator is used to collimate the divergent light emitted by the target light field located at the field diaphragm into parallel light.

[0033] The detection system includes a relay imaging mirror, a cold screen aperture and an array detector; wherein the relay imaging mirror is located in the reflection direction of the beam splitter, and the relay imaging mirror adopts an object-side telecentric optical path structure, and is used to image the interference light field modulated by the reflective Fabry-Perot etalon array onto the array detector; the cold screen aperture is located on the image-side focal plane of the relay imaging mirror, and is used to limit the object-side numerical aperture; the array detector is located at the image plane of the relay imaging mirror, and is used to perform photoelectric conversion on the interference light field to obtain an interference image array.

[0034] The present invention images the target light field onto the field diaphragm through a telescope objective lens. The field diaphragm limits the imaging field of view and then collimates it into parallel light through a collimator. The light is incident on a microlens array. The microlens array performs array focusing on the incident light field and transmits it through a beam splitter. Multiple arrays are imaged onto a reflective Fabry-Perot etalon array. The reflective Fabry-Perot etalon array is composed of a substrate and a plurality of Fabry-Perot etalon units located on the substrate. Each Fabry-Perot etalon unit is equivalent to a phase plate. The plurality of phase plates and the substrate at the bottom form a checkerboard-shaped and step-distributed phase reflection plate. Each step corresponds to an imaging channel, that is, corresponds to a microlens unit. By designing the height of each step, the step height distribution is in a checkerboard-shaped two-dimensional linear incremental change, that is, the thickness of the medium cavity of the reflective Fabry-Perot etalon array is in a two-dimensional linear incremental change. Each thickness of the medium cavity corresponds to a specific optical path difference, thereby modulating the optical path difference of the incident imaging light field to produce a change in the intensity of the interference image. Therefore, the imaging light field array is modulated by the reflective Fabry-Perot etalon array to form an interference light field array, and each interference light field unit corresponds to a specific optical path difference. The interference light field array is imaged onto the area array detector after being reflected by the beam splitter and transmitted by the relay imaging mirror, and an interference image array corresponding to the optical path difference array is obtained on the area array detector. By performing image segmentation and image registration on the interference image array and performing discrete Fourier transform along the optical path difference, the spectral information of each object point in the target scene can be restored, and snapshot measurement of the image information and spectral information of the target scene can be achieved. The present invention reduces the size of the Fourier transform infrared imaging spectrometer and has the advantages of compact structure, static, stable, and reliable.

[0035] Example 1 like Figure 1-Figure 5 As shown, the reflective Fabry-Perot etalon array snapshot interferometric imaging spectrometer provided in Example 1 of the present invention includes a telescope objective 10, a field aperture 20, a collimator 30, a microlens array 40, a beam splitter 50, a reflective Fabry-Perot etalon array 60, a relay imaging mirror 70, a cold screen aperture 80 and a planar array detector 90.

[0036] The target light field is first imaged onto the field stop 20 through the telescope objective 10. The field stop 20 limits the imaging field of the target light field, thereby controlling the spatial sampling on the array detector 90 and the size of the imaging field, and suppressing the crosstalk of the imaging field between adjacent interference channels. Then it is collimated into parallel light by the collimator 30 and incident on the microlens array 40. The microlens array 40 is composed of M×N microlens units, which performs aperture segmentation and array imaging on the incident parallel light field. The microlens array 40 adopts an image-side telecentric optical path structure so that the main light of the array imaging beam is parallel to the optical axis. The microlens array 40 divides the incident light field into M×N sub-apertures, and after transmission through the beam splitter 50, the array is imaged onto the reflective Fabry-Perot etalon array 60. The reflective Fabry-Perot etalon array 60 is located on the image focal plane of the microlens array 40 . Each Fabry-Perot etalon unit corresponds to a specific microlens unit, and performs interference modulation on each image field unit of the microlens array 40 .

[0037] The reflective Fabry-Perot etalon array 60 is composed of a substrate 601 and Fabry-Perot etalon units at different heights on the substrate 601. Steps are formed between the multiple Fabry-Perot etalon units at different heights and arranged in a checkerboard pattern. Each step corresponds to a Fabry-Perot etalon unit. Each Fabry-Perot etalon unit forms a dielectric cavity. Each dielectric cavity has a specific thickness, thereby forming a two-dimensional thickness distribution that changes in a checkerboard-like manner between the reflection interfaces on both sides of the dielectric cavity, thereby forming an optical path difference that changes with the spatial position. The thickness of the first step is controlled to be close to zero optical path difference. The reflective Fabry-Perot etalon array 60 uses the medium reflectivity of Fresnel reflection of a high-refractive-index medium to form a low-fineness interference cavity, which is close to double-beam interference, so that spectral restoration can be performed through Fourier transform.

[0038] A distributed FP resonant cavity is formed between the reflective interfaces on both sides of the dielectric cavity, and each FP resonant cavity has a specific cavity length and thus has a fixed optical path difference. Light incident on the front and rear reflective interfaces will be reflected multiple times in the FP resonant cavity, and interference will occur between the light beams that pass through the FP resonant cavity at different times. The intensity of the interference signal emitted by the light through the FP resonant cavity depends on the thickness of the medium between the front and rear reflective interfaces of the dielectric cavity, the reflectivity of the reflective interface, the incident angle of the light, and the refractive index of the medium in the FP resonant cavity between the reflective interfaces. The medium in the FP resonant cavity can be a low refractive index medium or a high refractive index medium, and different medium types correspond to different reflective interface structures. The reflective interface of the traditional Fabry-Perot interference system usually adopts a very high reflectivity to produce a narrow transmission band, while the reflective interface of the reflective Fabry-Perot etalon array 60 in the present invention adopts a medium reflectivity to produce a quasi-cosine interference signal that can be demodulated by Fourier transform.

[0039] The interference image signal formed by the FP resonant cavity corresponding to the (m, n)th step in the reflective Fabry-Perot etalon array 60 can be expressed as: ; Among them, R1 and R2 are the reflectivities of the two reflection interfaces of the dielectric cavity; ν is the wave number, ν=1 / λ, λ is the wavelength, and δ(m,n) is the optical path difference of the FP resonant cavity corresponding to the (m,n)th step, and its expression is: ; Among them, n0 is the refractive index of the medium in the FP resonant cavity; θ is the incident angle of the light in the FP resonant cavity, corresponding to different aperture angles of the target light field; h(m,n) is the thickness of the medium in the FP resonant cavity, and the thickness of the medium in the FP resonant cavity varies with different spatial positions.

[0040] It can be seen from the interference image signal formula that when the reflectivity of the reflection interface is very low, the interference signal is a cosine function, but the modulation of the interference fringes is also very low; when the reflectivity of the reflection interface is very high, the interference fringes have a very high modulation, but the interference signal is an extremely narrow comb function. The traditional Fabry-Perot interferometer uses a reflection interface with a very high reflectivity and uses resonance to produce very narrow interference features. These very narrow comb-shaped interference signals will produce side lobes in the Fourier transform spectrum, which will take away the signal from the main frequency and cause the restored spectrum to be distorted. In order to suppress the spectral distortion caused by harmonic signals and reduce the interference caused by the side lobe signal extending to the main frequency signal, the maximum wave number of the incident spectrum should be less than or equal to twice the minimum wave number, that is, the maximum wavelength is less than or equal to twice the minimum wavelength, that is, the wavelength bandwidth of the incident spectrum should be less than or equal to the minimum wavelength, or less than or equal to half of the maximum wavelength. For short-wave infrared 1μm-2μm, medium-wave infrared 3μm-5μm, and long-wave infrared 8μm-14μm, they can basically meet the application requirements.

[0041] Therefore, the present invention uses a reflective interface with medium reflectivity to generate a cosine-like interference signal. At this time, the spectral fineness is low, and the reflective Fabry-Perot etalon array 60 is close to double-beam interference. The interference pattern function can be approximately expressed as: ; Therefore, the spectral information of the incident light signal can be restored from the interference signal through Fourier transform.

[0042] Although the lower the reflectivity, the closer the interference signal is to the cosine function, and thus the higher the spectral restoration accuracy, too low a reflectivity will also reduce the modulation of the interference fringes. Therefore, in order to achieve effective demodulation of the spectrum through Fourier transform, it is necessary to balance the fringe modulation and spectral sidelobe suppression. By balancing the interference pattern modulation and the cosine degree of the interference signal, the reflectivity of the reflection interface is determined, the spectral sidelobes are minimized and the interference pattern modulation is maximized. In other words, by optimizing the reflectivity of the reflection interface, the maximum trade-off between the interference fringe modulation and the cosine characteristic is achieved. In the present invention, the reflectivity of the two reflection interfaces of the dielectric cavity is set at 30% to 40%, which can achieve the best trade-off between the interference pattern modulation and the cosine characteristic. Therefore, each Fabry-Perot etalon unit in the present invention is a low-fineness Fabry-Perot cavity that modulates the interference intensity of the interference image under a given optical path difference.

[0043] For infrared materials, silicon and germanium materials have a higher refractive index and thus have a relatively moderate reflectivity. For silicon material, its refractive index is 3.4 and its surface reflectivity is 30%; for germanium material, its refractive index is 4.0 and its surface reflectivity is 36%. Therefore, the substrate 601 can be a low-refractive-index substrate made of low-refractive-index media such as quartz, calcium fluoride, magnesium fluoride, sapphire, etc. The low-refractive-index substrate supports the Fabry-Perot etalon unit above. A high-refractive-index transparent medium layer 602 (i.e., Fabry-Perot etalon unit) with a two-dimensional step-shaped checkerboard distribution is made of high-refractive-index medium materials such as silicon or germanium on the low-refractive-index substrate. The upper surface of the high-refractive-index transparent medium layer 602 is not coated, and the thickness of the first step is controlled to make it close to zero optical path difference. The substrate 601 can also be a metal substrate. A high refractive index transparent medium layer 602 with a two-dimensional stepped checkerboard distribution is made on a metal substrate using high refractive index medium materials such as silicon or germanium. Similarly, the upper surface of the high refractive index transparent medium layer 602 is not coated, and the thickness of the first step is controlled to make it close to zero optical path difference.

[0044] The dielectric thickness distribution between the two reflection interfaces of the two-dimensional step phase plate with a checkerboard distribution constitutes the spatially distributed modulation of the optical path difference. The total height of each step corresponds to the dielectric thickness in the FP resonant cavity. Assuming that the step height difference of the two-dimensional step phase plate with a checkerboard distribution is d and the number of steps is M×N, in order to form continuous optical path difference sampling, the dielectric thickness of the (m,n)th FP resonant cavity is: ; In order to achieve effective spectral restoration, the step height d should satisfy the Nyquist sampling theorem. In order to suppress the spectral aliasing caused by the Fourier transform of high-order sidelobe signals, the sampled signal cutoff frequency is extended to J Subharmonics (generally, JFor the incident broadband spectrum, the step height difference d should satisfy the following relationship: ; Among them, λ min is the minimum wavelength of the broadband spectrum, θ max is the incident angle of the maximum aperture angle light in the FP resonant cavity, J is the spectral harmonic order, and n0 is the medium refractive index of the Fabry-Perot etalon unit.

[0045] For incident narrowband spectra, especially for gas detection, in order to achieve high spectral resolution, the step height difference d should satisfy the following relationship: ; Among them, λ S is the shortest wavelength of the narrowband spectrum, λ L is the longest wavelength of the narrowband spectrum, k is the spectral folding order, which is less than or equal to Any integer of .

[0046] The height difference between any two adjacent steps in one direction of the two-dimensional step phase plate is a constant d, and the height difference between any two adjacent steps in the other direction is a constant Md. The two-dimensional step phase plate is composed of M×N steps and is manufactured by a coating method. The manufacturing process is as follows: S1: providing a substrate with a lateral width of a and a longitudinal width of b, and polishing and cleaning the substrate; S2: evaporating a zero optical path difference medium layer of the medium cavity on the substrate, the thickness of the zero optical path difference medium layer is close to zero, and the lateral width and longitudinal width of the zero optical path difference medium layer are respectively the same as the lateral width and longitudinal width of the substrate; S3: vapor-depositing a longitudinal two-step dielectric layer of the dielectric cavity on the zero optical path difference dielectric layer, wherein the thickness of the longitudinal two-step dielectric layer is NMd / 2, the longitudinal width of the longitudinal two-step dielectric layer is b / 2, and the transverse width of the longitudinal two-step dielectric layer is a; S4: vapor-depositing a longitudinal four-step dielectric layer of the dielectric cavity on the longitudinal two-step dielectric layer, the thickness of the longitudinal four-step dielectric layer is NMd / 4, the longitudinal width of the longitudinal four-step dielectric layer is b / 4, and the transverse width of the longitudinal four-step dielectric layer is a, repeating step S4, in each vapor deposition process of the longitudinal step dielectric layer, the thickness of the longitudinal step dielectric layer is 1 / 2 of the previous time, and the longitudinal width of the longitudinal step dielectric layer is 1 / 2 of the previous time, until the step height difference of the longitudinal step dielectric layer is Md, and the longitudinal width of the longitudinal step dielectric layer is b / N; S5: evaporating a transverse two-step dielectric layer of the dielectric cavity on the longitudinal step dielectric layer, the thickness of the transverse two-step dielectric layer is Md / 2, the transverse width of the transverse two-step dielectric layer is a / 2, and the longitudinal width of the transverse two-step dielectric layer is b; S6: evaporate a transverse four-step dielectric layer of the dielectric cavity on the transverse two-step dielectric layer, the thickness of the transverse four-step dielectric layer is Md / 4, the transverse width of the transverse four-step dielectric layer is a / 4, and the longitudinal width of the transverse four-step dielectric layer is b. Repeat step S6. In each evaporation process of the transverse step dielectric layer, the thickness of the transverse step dielectric layer is 1 / 2 of the previous time, and the transverse width of the transverse step dielectric layer is 1 / 2 of the previous time, until the step height difference of the transverse step dielectric layer is d, and the transverse width of the transverse step dielectric layer is a / M.

[0047] The imaging light field is modulated by the reflective Fabry-Perot etalon array 60 and then reflected back to the beam splitter 50 and reflected by the beam splitter 50, and then imaged onto the area array detector 90 at a certain reduction ratio through the relay imaging mirror 70. The relay imaging mirror 70 samples the object-side telecentric optical path structure, and its image-side focal plane matches the cold screen aperture 80 of the area array detector 90. In other words, the cold screen aperture 80 of the area array detector 90 is located on the image-side focal plane of the relay imaging mirror 70. The reflective Fabry-Perot etalon array 60 and the area array detector 90 satisfy the object-image conjugate relationship relative to the relay imaging mirror 70. The relay imaging mirror 70 relays the interference light field modulated by the reflective Fabry-Perot etalon array 60 onto the area array detector 90 to obtain a set of interference image arrays, and each interference image unit corresponds to a Fabry-Perot etalon unit of a specific medium thickness of the reflective Fabry-Perot etalon array 60, thereby corresponding to an inherent optical path difference δ. In the present invention, each interference image unit in the interference image array is a copy of the same field of view, and intensity modulated by the corresponding Fabry-Perot etalon unit. The area array detector 90 performs image segmentation on the interference image array, divides the interference image array into interference image units corresponding to each specific Fabry-Perot etalon unit, and arranges the divided interference image units into an interference image data cube according to the thickness order of the Fabry-Perot etalon unit. The thickness of each Fabry-Perot etalon unit corresponds to a specific optical path difference δ, and after image registration, the interference image of each target point can be extracted. Each spatial pixel of the two-dimensional image plane in the interference image data cube is extracted, and the interference light intensity of each optical path difference corresponding to the spatial pixel is extracted along the optical path difference δ axis, so as to obtain the interference image sequence corresponding to each spatial pixel. Discrete Fourier transform operation is performed on the interference image sequence of each spatial pixel, and the spectral information corresponding to each spatial pixel is obtained, thereby obtaining a spectral image data cube that changes with the wavelength λ, thereby demodulating the spectral information of each point of the target scene, and realizing the snapshot measurement of the image information and spectral information of the target scene.

[0048] Example 2 The difference between Example 2 and Example 1 is only that the structure of the reflection Fabry-Perot etalon array is different. Figure 6 As shown, the substrate 603 of the reflective Fabry-Perot etalon array of Example 2 adopts a high refractive index substrate made of a high refractive index dielectric material such as silicon and germanium, and the upper surface of the high refractive index substrate is used as the lower reflection interface of the Fabry-Perot etalon unit. A low refractive index transparent dielectric layer 604 with a checkerboard distribution and two-dimensional step shape is made of a low refractive index transparent material such as silicon dioxide, aluminum oxide, calcium fluoride, magnesium fluoride, yttrium fluoride, thorium fluoride, and cerium fluoride on the high refractive index substrate, and a silicon film or a germanium film of a certain thickness is evaporated on the upper surface of the low refractive index transparent dielectric layer 604 as a reflective film 605, and the reflective film 605 is used as the upper reflection interface of the Fabry-Perot etalon unit, and the thickness of the first step is controlled to make it close to zero optical path difference. Alternatively, a two-dimensional stepped low-refractive index transparent medium layer 604 with a checkerboard distribution can be made of a low-refractive index transparent material such as silicon dioxide, aluminum oxide, calcium fluoride, magnesium fluoride, yttrium fluoride, thorium fluoride, or cerium fluoride on a metal reflective substrate, and a silicon film or germanium film of a certain thickness can be evaporated on the upper surface of the low-refractive index transparent medium layer 604 as a reflective film 605, and the thickness of the first step can be controlled to make it close to zero optical path difference.

[0049] Example 3 The difference between Example 3 and Example 1 and Example 2 is only that the structure of the reflection Fabry-Perot etalon array is different. Figure 7 As shown, the substrate 606 of the reflective Fabry-Perot etalon array of Example 3 adopts an opaque glass or plastic substrate, and a silicon film or a germanium film of a certain thickness is evaporated on the surface of the opaque glass or plastic substrate as a lower metal film 608. The silicon film or the germanium film can also be replaced by a metal film such as silver, gold, or aluminum. The lower metal film 608 is used as the lower reflection interface of the Fabry-Perot etalon unit, and then a low-refractive-index transparent medium layer 607 with a checkerboard distribution and a two-dimensional stepped shape is made of a low-refractive-index transparent material such as silicon dioxide, aluminum oxide, calcium fluoride, magnesium fluoride, yttrium fluoride, thorium fluoride, or cerium fluoride on the lower metal film 608, and a silicon film or a germanium film of a certain thickness is evaporated on the upper surface of the low-refractive-index transparent medium layer 607 as an upper reflection film 609, and the upper reflection film 609 is used as the upper reflection interface of the Fabry-Perot etalon unit, and the thickness of the first step is controlled to make it close to zero optical path difference.

[0050] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the disclosure of the present invention can be performed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.

[0051] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A reflective Fabry-Perot etalon array snapshot interferometric imaging spectrometer, characterized in that: It includes a telescope system, a microlens array, a beam splitter, a reflective Fabry-Perot etalon array and a detection system; among which, The telescope system is used to collect the target light field and to limit and collimate the target light field; The microlens array is located in the collimation direction of the telescope system. The micro-imaging mirror array adopts an image-side telecentric optical path structure and is composed of M×N microlens units. The micro-imaging mirror array is used to perform array imaging on the collimated target light field. The beam splitter is located in the imaging light path of the microlens array and is used to transmit the array imaging light beam; The reflective Fabry-Perot etalon array is located on the image focal plane of the microlens. The reflective Fabry-Perot etalon array is composed of a substrate and M×N Fabry-Perot etalon units whose dielectric cavity thickness increases linearly in two dimensions. The thickness of each dielectric cavity corresponds to an optical path difference. The step height difference between any two adjacent Fabry-Perot etalon units in one direction is d, and the step height difference between any two adjacent Fabry-Perot etalon units in another direction is Md. Each Fabry-Perot etalon unit corresponds to a microlens unit. The detection system is located in the reflection direction of the beam splitter and is used to image the interference light field modulated by the reflective Fabry-Perot etalon array to obtain an interference image array.

2. The reflective Fabry-Perot etalon array snapshot interferometric imaging spectrometer according to claim 1, characterized in that: The reflectivity of the two reflection interfaces of the dielectric cavity is 30%~40%.

3. The reflective Fabry-Perot etalon array snapshot interferometric imaging spectrometer according to claim 2, characterized in that: The substrate adopts a low-refractive index substrate or a metal substrate, and the Fabry-Perot etalon unit adopts a high-refractive index transparent medium layer; or, the substrate adopts a high-refractive index substrate or a metal substrate, and the Fabry-Perot etalon unit adopts a low-refractive index transparent medium layer, and a reflective film is plated on the upper surface of the low-refractive index transparent medium layer; or, the substrate adopts an opaque glass or plastic substrate, and a reflective film is plated on the upper surface of the opaque glass or plastic substrate, and the Fabry-Perot etalon unit adopts a low-refractive index transparent medium layer, and a reflective film is plated on the upper surface of the low-refractive index transparent medium layer.

4. The reflective Fabry-Perot etalon array snapshot interferometric imaging spectrometer according to claim 3, characterized in that: The low refractive index substrate is made of quartz, calcium fluoride, magnesium fluoride or sapphire dielectric material; the high refractive index transparent dielectric layer is made of silicon dielectric material or germanium dielectric material; the high refractive index substrate is made of silicon dielectric material or germanium dielectric material, the low refractive index transparent dielectric layer is any one of silicon dioxide, aluminum oxide, calcium fluoride, magnesium fluoride, yttrium fluoride, thorium fluoride and cerium fluoride, and the reflective film is a silicon film or a germanium film.

5. The reflective Fabry-Perot etalon array snapshot interferometric imaging spectrometer according to claim 1, characterized in that: The dielectric cavity thickness h(m,n) of the (m,n)th Fabry-Perot etalon unit is: 。 6. The reflective Fabry-Perot etalon array snapshot interferometric imaging spectrometer according to claim 1, characterized in that: For an incident broadband spectrum, the step height difference d satisfies the following relationship: ； Among them, λ min is the minimum wavelength of the broadband spectrum, θ max is the incident angle corresponding to the maximum aperture angle light in the dielectric cavity, J is the spectral harmonic order, and n0 is the dielectric refractive index of the Fabry-Perot etalon unit; For an incident narrowband spectrum, the step height difference d satisfies the following relationship: ； Among them, λs is the shortest wavelength of the narrowband spectrum, λ L is the longest wavelength of the narrowband spectrum, k is the spectral folding order, which is less than or equal to Any integer of .

7. The reflective Fabry-Perot etalon array snapshot interferometric imaging spectrometer according to claim 1, characterized in that: The preparation process of the reflection Fabry-Perot etalon array is as follows: S1: providing a substrate with a lateral width of a and a longitudinal width of b, and polishing and cleaning the substrate; S2: evaporating a zero optical path difference medium layer of the medium cavity on the substrate, the thickness of the zero optical path difference medium layer is close to zero, and the lateral width and longitudinal width of the zero optical path difference medium layer are respectively the same as the lateral width and longitudinal width of the substrate; S3: vapor-depositing a longitudinal two-step dielectric layer of the dielectric cavity on the zero optical path difference dielectric layer, the thickness of the longitudinal two-step dielectric layer is NMd / 2, the longitudinal width of the longitudinal two-step dielectric layer is b / 2, and the transverse width of the longitudinal two-step dielectric layer is a; S4: vapor-depositing a longitudinal four-step dielectric layer of the dielectric cavity on the longitudinal two-step dielectric layer, the thickness of the longitudinal four-step dielectric layer is NMd / 4, the longitudinal width of the longitudinal four-step dielectric layer is b / 4, and the transverse width of the longitudinal four-step dielectric layer is a, repeating step S4, in each vapor deposition process of the longitudinal step dielectric layer, the thickness of the longitudinal step dielectric layer is 1 / 2 of the previous time, and the longitudinal width of the longitudinal step dielectric layer is 1 / 2 of the previous time, until the step height difference of the longitudinal step dielectric layer is Md, and the longitudinal width of the longitudinal step dielectric layer is b / N; S5: evaporating a transverse two-step dielectric layer of the dielectric cavity on the longitudinal step dielectric layer, the thickness of the transverse two-step dielectric layer is Md / 2, the transverse width of the transverse two-step dielectric layer is a / 2, and the longitudinal width of the transverse two-step dielectric layer is b; S6: evaporate a transverse four-step dielectric layer of the dielectric cavity on the transverse two-step dielectric layer, the thickness of the transverse four-step dielectric layer is Md / 4, the transverse width of the transverse four-step dielectric layer is a / 4, and the longitudinal width of the transverse four-step dielectric layer is b. Repeat step S6. In each evaporation process of the transverse step dielectric layer, the thickness of the transverse step dielectric layer is 1 / 2 of the previous time, and the transverse width of the transverse step dielectric layer is 1 / 2 of the previous time, until the step height difference of the transverse step dielectric layer is d, and the transverse width of the transverse step dielectric layer is a / M.

8. The reflective Fabry-Perot etalon array snapshot interferometric imaging spectrometer according to claim 1, characterized in that: The telescope system includes a telescope objective lens, a field stop and a collimator lens; among them, The telescope objective is used to collect the target light field and image the target light field at the field aperture; The field diaphragm is located on both the image-side focal plane of the telescope objective and the object-side focal plane of the collimator. The field diaphragm is used to limit the field of view of the imaging of the target light field. The collimator is used to collimate the divergent light emitted by the target light field located at the field stop into parallel light.

9. The reflective Fabry-Perot etalon array snapshot interferometric imaging spectrometer according to claim 1, characterized in that: The detection system includes a relay imaging mirror, a cold screen aperture and an array detector; among them, The relay imaging mirror is located in the reflection direction of the beam splitter and adopts an object-side telecentric optical path structure, and is used to image the interference light field modulated by the reflective Fabry-Perot etalon array onto the area array detector; The cold screen diaphragm is located on the image-side focal plane of the relay imaging mirror and is used to limit the object-side numerical aperture; The area array detector is located at the image plane of the relay imaging mirror and is used to perform photoelectric conversion on the interference light field to obtain an interference image array.

10. The reflective Fabry-Perot etalon array snapshot interferometric imaging spectrometer according to claim 9, characterized in that: The area array detector is also used to perform image segmentation on the interference image array, dividing the interference image array into interference image units corresponding to each Fabry-Perot etalon unit; and arranging the interference image units in the order of the thickness of each Fabry-Perot etalon unit to form an interference image data cube, and performing discrete Fourier transform operation on the interference image data cube with the optical path difference as the axis to obtain a spectral image data cube that varies with wavelength.

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