Miniature Fourier Transform Spectrometer and Its Measurement Method

Abstract

The present invention provides a micro Fourier transform spectrometer and a measurement method thereof. The spectrometer includes: a light source system, an optical path delay device, a digital micromirror array, and a detector system; the light source system is used to emit a parallel light beam, and after the distributed phase modulation of the optical path delay device, the parallel light beam obtains an optical field array composed of N×N optical field units. The digital micromirror array is used to gate the optical field array, so that at least two light beams corresponding to at least two optical field units are incident on the detector system to generate interference, obtaining an interference pattern signal and acquiring the spectral information of the parallel light beam. The present invention realizes the precise modulation of the optical path difference and the precise sampling of the interference signal. It avoids the problems of difficult fabrication and control of the scanning moving mirror, reduces the volume and weight of the system, and improves the energy utilization rate of the system at the same time.

Description

Technical Field

[0001] The present invention relates to the field of spectroscopy, and particularly to a micro Fourier transform spectrometer and a measurement method thereof. Background Art

[0002] Spectroscopy can obtain the composition and content information of target substances, and has been increasingly widely used in fields such as physical experiments, chemical analysis, biological characterization, medical tests, ecological environment protection, etc., and has played an important role in the exploration and discovery of new materials, new energy sources, and the unknown world. In order to obtain the spectral characteristics of the target, it is necessary to decompose the detected polychromatic light spectroscopically. Currently, the commonly used spectroscopic instruments mainly adopt technologies such as filter spectroscopy, prism spectroscopy, grating spectroscopy, and interference spectroscopy. Among them, the Fourier transform spectroscopy technology using interference spectroscopy has become a high-end instrument and equipment in many application fields due to its advantages such as multi-channel, high throughput, accurate wave number, 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 exploration, atmospheric monitoring, and military reconnaissance, due to their special application fields and usage environments, there is an urgent need for miniaturized and static Fourier transform spectrometers. And with the continuous upgrading of the demand, it has made it difficult for traditional Fourier transform spectrometers to overcome technical bottlenecks. Currently, the Fourier transform spectrometers commonly used in laboratories adopt a time-modulated structure. The interferometer generates an optical path difference through the scanning of a moving mirror to obtain spectral information. It contains a set of high-precision moving mirror scanning mechanisms, and precise sampling of the interference pattern is carried out through the high-precision moving mirror scanning mechanism. This mechanism is very complex to manufacture, sensitive to vibration, relatively demanding on the usage environment, and the moving mirror scanning mechanism has a large volume and weight; at the same time, due to the use of a beam splitter for spectroscopy, there will be an energy loss of half, reducing the stability and reliability of the system, which is not conducive to aerospace applications such as meteorological observation and atmospheric remote sensing. Thus, it 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 problems, the object of the present invention is to propose a micro Fourier transform spectrometer and a measurement method thereof. By adjusting four stepped micromirrors and a digital micromirror, spatial division of the transverse light field and gated interference of the light field units are carried out, thereby obtaining the interference pattern signals of each sampling optical path difference, avoiding the moving mirror scanning mechanism and beam splitting system of the traditional Fourier transform spectrometer, reducing the volume and weight of the system, and improving the energy utilization rate. The micro spectrometer structure proposed by this invention has the characteristics of miniaturization, light weight, and high energy utilization rate.

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

[0006] The present invention provides a micro Fourier transform spectrometer, comprising: a light source system, an optical path delay device, a digital micromirror array, and a detector system;

[0007] The light source system is used to emit a parallel light beam. After the distributed phase modulation of the parallel light beam by the optical path delay device, an optical field array composed of N×N optical field units is obtained. The digital micromirror array is used to gate the optical field array, so that at least two light beams corresponding to at least two optical field units are incident into the detector system to generate interference, obtaining an interference pattern signal and acquiring the spectral information of the parallel light beam.

[0008] Preferably, the light source system comprises: a light source and a collimating mirror;

[0009] The light source is used to emit a divergent light beam. After the divergence light beam is collimated by the collimating mirror, a parallel light beam is formed, and the parallel light beam is incident into the optical path delay device.

[0010] Preferably, the optical path delay device comprises: a longitudinal optical path delay device and a transverse optical path delay device;

[0011] The longitudinal optical path delay device comprises a longitudinal stepped mirror and a longitudinal stepped compensating mirror; the longitudinal stepped mirror and the longitudinal stepped compensating mirror are mirror-symmetrical in the propagation direction of the parallel light beam;

[0012] The parallel light beam is first incident into the longitudinal stepped mirror, and after being reflected by the longitudinal stepped mirror and the longitudinal stepped compensating mirror in sequence, it is incident into the transverse optical path delay device;

[0013] The longitudinal stepped mirror is used to perform distributed phase modulation on the parallel light beam in the horizontal direction, and the longitudinal stepped compensating mirror is used to compensate for the beam transverse shift caused by the longitudinal stepped mirror;

[0014] The transverse optical path delay device comprises a transverse stepped mirror and a transverse stepped compensating mirror; the transverse stepped mirror and the transverse stepped compensating mirror are mirror-symmetrical in the propagation direction of the parallel light beam;

[0015] The longitudinal stepped compensating mirror is parallel to the transverse stepped mirror;

[0016] The parallel light beam is first incident into the transverse stepped mirror, and after being reflected by the transverse stepped mirror and the transverse stepped compensating mirror in sequence, it is incident into the digital micromirror array;

[0017] The transverse stepped mirror is used to perform distributed phase modulation on the parallel light beam in the vertical direction, and the transverse stepped compensating mirror is used to compensate for the beam transverse shift caused by the transverse stepped mirror.

[0018] Preferably, the longitudinal stepped mirror is composed of N column stepped units with the stepped direction perpendicular to the horizontal plane, and the longitudinal stepped compensating mirror has the same structure as the longitudinal stepped mirror;

[0019] The horizontal stepped mirror is composed of N row stepped units with the stepped directions parallel to the horizontal plane. The horizontal stepped compensation mirror has the same structure as the horizontal stepped mirror.

[0020] Preferably, the relative optical path delay generated by the i-th column stepped unit of the parallel light beam in the horizontal direction is OP 1 (i) = 4idcosθ;

[0021] The relative optical path delay generated by the j-th row stepped unit of the parallel light beam in the vertical direction is OP 2 (j) = 4jhcosθ;

[0022] Wherein, i = 0, 1, 2, …, N - 1; j = 0, 1, 2, …, N - 1; θ is the incident angle of the parallel light beam on the surface of the row stepped unit or column stepped unit.

[0023] Preferably, the digital micromirror array is parallel to the horizontal stepped compensation mirror, and the digital micromirror array includes N×N digital micromirror units;

[0024] The process of the digital micromirror array gating the light field array is as follows: by controlling the driving voltage of the digital micromirror array, and then controlling the rotation angle of the digital micromirror unit, so that at the same moment, two light beams of the light field units in the light field array corresponding to the digital micromirror unit (0, 0) and the digital micromirror unit (i, j) are incident on the detector system, where i and j are not both 0 at the same time.

[0025] Preferably, the two light beams gated by the digital micromirror array have a preset optical path difference, and two light beams with linearly increasing optical path differences are sequentially gated by controlling the digital micromirror array and incident on the detector system.

[0026] Preferably, the detector system includes: a focusing mirror and a photodetector;

[0027] The two light beams gated by the digital micromirror array are incident on the photodetector after being converged by the focusing mirror and interfere;

[0028] Define the two light beams gated by the digital micromirror array as a group of light beams;

[0029] When the digital micromirror array gates the first group of light beams with the first preset optical path difference, the first group of interference pattern signals is obtained;

[0030] When the digital micromirror array gates the second group of light beams with the second preset optical path difference, the second group of interference pattern signals is obtained;

[0031] Until all the interference pattern signals are acquired, the spectral information of the parallel light beam is obtained by performing a discrete Fourier transform on all the interference pattern signals.

[0032] The present invention also provides a measurement method for a micro Fourier transform spectrometer, comprising the following steps:

[0033] S1. A light source system is used to emit a parallel light beam incident on an optical path delay device;

[0034] S2. After the parallel light beam undergoes distributed phase modulation by a longitudinal optical path delay device and a transverse optical path delay device in the optical path delay device, an optical field array composed of N×N optical field units is obtained and incident on a digital micromirror array;

[0035] S3. By controlling the N×N digital micromirror units in the digital micromirror array, the gating of different optical field units in the optical field array is realized;

[0036] S4. After the light beams corresponding to at least two optical field units with a preset optical path difference gated by the digital micromirror array enter a detector system and interfere, an interference pattern signal is obtained, and then the spectral information of the parallel light beam is acquired.

[0037] Preferably, the step unit height d of the longitudinal stepped mirror and the step unit height h of the transverse stepped mirror satisfy the following relationship:

[0038]

[0039] where λ min is the minimum wavelength in the parallel light beam.

[0040] Compared with the existing technologies, the present invention uses stepped mirrors for aperture segmentation and distributed phase modulation of the spatial optical field, and performs gating interference on the segmented optical field units through digital micromirrors, realizing precise modulation of the optical path difference and precise sampling of the interference signal. The present invention patent proposes precise scanning without optical path difference and energy splitting of the Fourier transform spectrometer based on stepped mirrors and digital micromirrors, avoiding the problems of difficult fabrication and control of the scanning moving mirror, reducing the volume and weight of the system, and improving the energy utilization rate of the system simultaneously. Description of the Drawings

[0041] Figure 1 is a schematic structural diagram of a micro Fourier transform spectrometer according to an embodiment of the present invention.

[0042] Figure 2 is a schematic structural diagram of a longitudinal stepped mirror in a micro Fourier transform spectrometer according to an embodiment of the present invention.

[0043] Figure 3 is a schematic structural diagram of a transverse stepped mirror in a micro Fourier transform spectrometer according to an embodiment of the present invention.

[0044] Figure 4It is a schematic flowchart of a measurement method of a micro Fourier transform spectrometer according to an embodiment of the present invention.

[0045] Figure 5 It is a program block diagram of a measurement method of a micro Fourier transform spectrometer according to an embodiment of the present invention.

[0046] The reference numerals therein include: light source 1, collimator 2, longitudinal stepped mirror 3, longitudinal stepped compensating mirror 4, transverse stepped mirror 5, transverse stepped compensating mirror 6, digital micromirror array 7, focusing mirror 8, and photodetector 9. Detailed implementation manners

[0047] In the following, embodiments of the present invention will be described with reference to the drawings. In the following description, the same modules are denoted by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, their detailed descriptions will not be repeated.

[0048] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the 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 to the present invention.

[0049] Figure 1 It shows the structure of a micro Fourier transform spectrometer according to an embodiment of the present invention.

[0050] As Figure 1 shown, the micro Fourier transform spectrometer provided by the embodiment of the present invention includes: a light source system, an optical path delay device, a digital micromirror array 7, and a detector system.

[0051] The light source system is used to emit a parallel light beam. The light source system includes: a light source 1 and a collimator 2.

[0052] The light source 1 emits a divergent light beam with a certain spectral radiation range. The divergent light beam is collimated by the collimator 2 to form a parallel light beam. The parallel light beam is incident into the optical path delay device.

[0053] The optical path delay device includes: a transverse optical path delay device and a longitudinal optical path delay device.

[0054] Among them, the longitudinal optical path delay device includes a longitudinal stepped mirror 3 and a longitudinal stepped compensating mirror 4; the transverse optical path delay device includes a transverse stepped mirror 5 and a transverse stepped compensating mirror 6;

[0055] The parallel light beam is first incident on the longitudinal stepped mirror 3. After being reflected by the longitudinal stepped mirror 3, it is incident on the longitudinal stepped compensating mirror 4. After being reflected by the longitudinal stepped compensating mirror 4, the parallel light beam is incident on the transverse stepped mirror 5. After being reflected by the transverse stepped mirror 5, it is incident on the transverse stepped compensating mirror 6. After being reflected by the transverse stepped compensating mirror 6, the parallel light beam is incident on the digital micromirror array 7.

[0056] Figure 2 Fig. shows the structure of the longitudinal stepped mirror in the micro Fourier transform spectrometer provided by an embodiment of the present invention.

[0057] As Figure 2 shown, the longitudinal stepped mirror 3 is composed of N column stepped units with the stepped direction perpendicular to the horizontal plane. The longitudinal stepped mirror 3 is placed at an angle of 45° with the optical axis of the parallel light beam. During the placement process, it is necessary to ensure that the parallel light beam is all incident on the upper surface of the longitudinal stepped mirror 3 and does not irradiate the side surface of the longitudinal stepped mirror 3, that is, the high-step side of the longitudinal stepped mirror 3 is close to the collimator, and the low-step side is far from the collimator.

[0058] After the parallel light beam is reflected by the surfaces of each column stepped unit of the longitudinal stepped mirror 3, the outgoing light beam is turned by 90° for parallel transmission and is incident on the longitudinal stepped compensating mirror 4. The longitudinal stepped compensating mirror 4 has the same structure as the longitudinal stepped mirror 3 and has the same structure and parameters, which is to compensate for the beam transverse shift caused by the longitudinal stepped mirror 3 in space. The longitudinal stepped compensating mirror 4 is also placed at an angle of 45° with the optical axis of the parallel light beam and is perpendicular to the longitudinal stepped mirror 3 in space, and is mirror-symmetric with respect to the vertical plane of the optical axis of the longitudinal stepped mirror 3. That is, the longitudinal stepped mirror 3 and the longitudinal stepped compensating mirror 4 are orthogonally arranged at 90°, and the heights of each column stepped unit in the longitudinal stepped mirror 3 and the longitudinal stepped compensating mirror 4 correspond one by one, that is, the low column stepped unit of the longitudinal stepped mirror 3 corresponds to the low column stepped unit of the longitudinal stepped compensating mirror 4; the high column stepped unit of the longitudinal stepped mirror 3 corresponds to the high column stepped unit of the longitudinal stepped compensating mirror 4.

[0059] Suppose the number of steps of the stepped units of the longitudinal stepped mirror 3 and the longitudinal stepped compensating mirror 4 is both N, the width of the stepped unit is a, the height of the stepped unit is d, and the stepped unit direction is perpendicular to the horizontal plane. For the longitudinal stepped mirror 3, after the parallel light beam is reflected by the longitudinal stepped mirror 3, the optical path delay introduced between adjacent column stepped units for the parallel light beam is 2dcosθ.

[0060] Where, θ is the incident angle of the parallel light beam on the surface of each column stepped unit. In one of the embodiments provided by the present invention, θ = 45°.

[0061] Therefore, after the parallel light beam is reflected by the longitudinally stepped micro-mirror 3 and the longitudinally stepped compensating mirror 4 which are symmetric to each other, the optical path delay introduced between adjacent column stepped units for the parallel light beam is 4dcosθ.

[0062] Thus, the relative optical path delay generated by the i-th (i = 0, 1, 2, …, N - 1) column stepped unit in the horizontal direction is OP 1 (i) = 4idcosθ.

[0063] Since the surface of the longitudinally stepped micro-mirror 3 is inclined along the optical axis, the light passing aperture of each longitudinally stepped unit becomes acosθ - dsinθ. Since the step height d is a very small quantity relative to the step width a, the light passing aperture of each longitudinally stepped micro-mirror unit is approximately acosθ.

[0064] The parallel light beam reflected by the longitudinally stepped compensating mirror 4 is incident on the transversely stepped micro-mirror 5.

[0065] Figure 3 Fig. shows the structure of the transversely stepped micro-mirror in the micro Fourier transform spectrometer according to an embodiment of the present invention.

[0066] The transversely stepped micro-mirror 5 is composed of N row stepped units with the step direction parallel to the horizontal plane. The transversely stepped micro-mirror 5 is placed at an angle of 45° with respect to the optical axis and is parallel to the longitudinally stepped compensating mirror 4. After the parallel light beam is reflected by the surfaces of each row stepped unit of the transversely stepped micro-mirror 5, the outgoing light beam is turned by 90° for parallel transmission and is incident on the transversely stepped compensating mirror 6. The transversely stepped compensating mirror 6 has the same structure and parameters as the transversely stepped micro-mirror 5, and is used to compensate for the beam lateral shift caused by the transversely stepped micro-mirror 5 in space. The transversely stepped compensating mirror 6 is also placed at an angle of 45° with respect to the optical axis of the parallel light beam, and is perpendicular to the transversely stepped micro-mirror 5 in space, and is mirror symmetric with respect to the vertical plane of the transversely stepped micro-mirror 5 with respect to the optical axis. That is, the transversely stepped micro-mirror 5 and the transversely stepped compensating mirror 6 are orthogonally arranged at 90°, and the heights of the respective row stepped units in the transversely stepped micro-mirror 5 and the transversely stepped compensating mirror 6 correspond one by one. The low row stepped unit of the transversely stepped micro-mirror 5 corresponds to the low row stepped unit of the transversely stepped compensating mirror 6, and the high row stepped unit of the transversely stepped micro-mirror 5 corresponds to the high row stepped unit of the transversely stepped compensating mirror 6.

[0067] Assume that the number of steps of the stepped units of the transversely stepped micro-mirror 5 and the transversely stepped compensating mirror 6 is both N, the width of the stepped unit is both b, the height of the stepped unit is both h, and the direction of the stepped unit is parallel to the horizontal plane. For the transversely stepped micro-mirror 5, after the parallel light beam is reflected by the transversely stepped micro-mirror 5, the optical path delay introduced between adjacent row stepped units for the parallel light beam is 2hcosθ.

[0068] Among them, θ is the incident angle of the parallel light beam on the surface of each stepped unit. In one of the embodiments provided by the present invention, θ = 45°.

[0069] Therefore, after the parallel light beam is reflected by the mutually symmetric transverse stepped mirror 5 and the transverse stepped compensating mirror 6, the optical path delay introduced to the parallel light beam between adjacent row stepped units is 4hcosθ.

[0070] Thus, the relative optical path delay generated by the j-th (j = 0, 1, 2,..., N - 1) row stepped unit in the vertical direction is OP 2 (j) = 4jhcosθ.

[0071] Since the surface of the transverse stepped mirror 5 is inclined along the optical axis, the light passing aperture of each transverse stepped mirror unit becomes bcosθ - hsinθ. Since the stepped height h is a very small quantity relative to the stepped width b, the light passing aperture of each transverse stepped mirror unit is approximately bcosθ.

[0072] The stepped directions of the transverse stepped mirror 5 and the longitudinal stepped mirror 3 are orthogonal in the transverse space, thereby dividing the light field of the parallel light beam into N×N light field units in the transverse space. Each light field unit corresponds to a specific row stepped unit of the transverse stepped mirror 5 and a specific column stepped unit of the longitudinal stepped mirror 3. The size of any light field unit in the obtained light field array of the parallel light beam is acosθ × bcosθ.

[0073] The parallel light beam reflected by the transverse stepped compensating mirror 6 is incident on the digital micromirror array 7. The digital micromirror array 7 is composed of N×N digital micromirror units, and each digital micromirror unit corresponds to a specific light field unit formed by the row stepped unit of the transverse stepped mirror 5 and the column stepped unit of the longitudinal stepped mirror 3.

[0074] The digital micromirror array 7 can be placed perpendicular to the optical axis or tilted at a certain angle.

[0075] Each digital micromirror unit of the digital micromirror array 7 can rotate a certain angle along its rotation axis, so as to realize the gating interference of any light field unit in the light field array of the spatial parallel light beam.

[0076] The digital micromirror unit in the digital micromirror array 7 corresponding to the light field unit formed by the row stepped unit of the i = 0 row of the transverse stepped mirror 5 and the column stepped unit of the j = 0 column of the longitudinal stepped mirror 3 is in the open state, that is, the digital micromirror unit (i, j) = (0, 0) is in the open state, and at the same time, the remaining digital micromirror units are kept in the closed state.

[0077] Turn on the remaining digital micromirror cells in the N×N digital micromirror array 7 one by one in the row-by-row and column-by-column direction, and only keep one digital micromirror cell with (i,j)≠(0,0) in the on state at each moment.

[0078] At the same moment, only the light beams passing through the digital micromirror cell (0,0) and the digital micromirror cell (i,j) are incident on the detector system, where i and j are not both 0 at the same time.

[0079] The detector system includes: a focusing mirror 8 and a photodetector 9.

[0080] After the light beams of two different light field units are focused by the focusing mirror 8, they are incident on the photodetector 9 to interfere, obtaining the interference pattern signals of parallel light beams with different optical path differences, and further obtaining the spectral information of the parallel light beams.

[0081] When the light beams corresponding to the (i,j)th light field unit and the (0,0)th light field unit interfere, the optical path difference between the two coherent light beams is:

[0082] δ(i,j) = 4jhcosθ + 4idcosθ = 4cosθ(jh + id)

[0083] Therefore, the intensity of the (i,j)th interference pattern signal is:

[0084]

[0085] By performing discrete Fourier transform demodulation on the interference pattern sequence, the spectral information of the parallel light beam can be restored.

[0086] In order to form a continuous optical path difference sequence, the longitudinal stepped mirror 3 and the transverse stepped mirror 5 must achieve optical path compensation for each other. By matching the step unit heights of the longitudinal stepped mirror 3 and the transverse stepped mirror 5, optical path complementarity can be achieved, making the step unit height of the transverse stepped mirror 5 N times that of the longitudinal stepped mirror 3, that is, h = Nd.

[0087] When the relationship between the step unit heights of the longitudinal stepped mirror 3 and the transverse stepped mirror 5 is h = Nd, the optical path difference sampling array of the parallel light beam is:

[0088] δ(i,j) = 4cosθ(jNd + id) = 4dcosθ(jN + i)

[0089] In order not to produce spectral aliasing during the spectral restoration process, the sampling interval of the optical path difference of the parallel light beam must be less than or equal to twice the minimum wavelength in the parallel light beam, that is:

[0090]

[0091] Therefore, the height d of the stepped unit of the longitudinal stepped mirror 3 and the height h of the stepped unit of the transverse stepped mirror 5 must satisfy the following relationship:

[0092]

[0093] At this time, the form of the parallel beam restored spectrum is:

[0094]

[0095] In the formula, ν is the wave number of the interference light signal. For light with a wavelength of λ, ν = 1 / λ.

[0096] According to the discrete Fourier transform theory, the spectral resolution of the system is:

[0097] Figure 4 It is a schematic flowchart of the measurement method of the micro Fourier transform spectrometer provided by the embodiment of the present invention.

[0098] Figure 5 It is a program block diagram of the measurement method of the micro Fourier transform spectrometer provided by the embodiment of the present invention.

[0099] As Figure 4 and Figure 5 shown, the measurement method of the micro Fourier transform spectrometer provided by the embodiment of the present invention includes the following steps:

[0100] S1. The light source system is used to emit a parallel beam of light and incident it on the optical path delay device.

[0101] Fix the collimating mirror on the platform base; use a divergent laser beam with a wavelength within the spectral band as the incident beam, place the light source at the front focal plane of the collimating mirror, and ensure that the emitted light is a parallel beam. Replace the laser light source with a broadband light source.

[0102] S2. After the parallel beam passes through the distributed phase modulation of the longitudinal optical path delay device and the transverse optical path delay device in the optical path delay device, an optical field array composed of N×N optical field units is obtained and incident on the digital micromirror array.

[0103] Step S2 includes the following sub-steps:

[0104] Place the longitudinal stepped mirror in the parallel optical path of the collimating mirror at an angle of 45° with the optical axis and perform central alignment;

[0105] Place the longitudinal stepped compensating mirror in the reflection optical path of the longitudinal stepped mirror at an angle of 45° with the optical axis and perform central alignment;

[0106] Adjust the direction of the longitudinal stepped compensating mirror so that the longitudinal stepped compensating mirror and the longitudinal stepped mirror are mirror-symmetrical along the propagation direction of the parallel beam.

[0107] Place the transverse stepped mirror in the reflection optical path of the longitudinal stepped compensator at an angle of 45° with respect to the optical axis, and perform central alignment.

[0108] Adjust the direction of the transverse stepped mirror so that the transverse stepped mirror is parallel to the longitudinal stepped compensator.

[0109] Place the transverse stepped compensator in the reflection optical path of the transverse stepped mirror at an angle of 45° with respect to the optical axis, and perform central alignment.

[0110] Adjust the direction of the transverse stepped compensator so that the transverse stepped compensator is mirror-symmetrical to the transverse stepped mirror along the propagation direction of the parallel light beam.

[0111] S3. By controlling N×N digital micromirror cells in the digital micromirror array, the gating of different light field units in the light field array is realized.

[0112] Place the digital micromirror array in the reflection optical path of the transverse stepped compensator and perform central alignment.

[0113] Adjust the angle of the digital micromirror array so that the digital micromirror array cells correspond one by one to the surfaces of the stepped mirror stepped cells.

[0114] S4. At least two light field units with a preset optical path difference selected by the digital micromirror array enter the detector system and interfere to obtain an interference pattern signal, and then the spectral information of the parallel light beam is acquired.

[0115] Place the focusing mirror in the outgoing optical path of the digital micromirror array.

[0116] Place the single-point detector at the focal plane of the focusing mirror; adjust the driving voltage of the digital micromirror array so that it can gate any two light field units in the spatial light field array.

[0117] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

[0118] The above specific embodiments of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and deformations made according to the technical concept of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A micro Fourier transform spectrometer, characterized in that, it includes: a light source system, an optical path delay device, a digital micromirror array and a detector system; the light source system is used to emit a parallel light beam, and after the distributed phase modulation of the optical path delay device, the parallel light beam obtains an optical field array composed of N×N optical field units. The digital micromirror array is used to gate the optical field array, so that at least two light beams corresponding to at least two optical field units are incident on the detector system to generate an interference pattern signal, and the spectral information of the parallel light beam is obtained; the light source system includes: a light source and a collimating mirror; the light source is used to emit a divergent light beam, and the divergent light beam forms a parallel light beam after being collimated by the collimating mirror, and the parallel light beam is incident on the optical path delay device; the optical path delay device includes: a longitudinal optical path delay device and a transverse optical path delay device; the longitudinal optical path delay device includes a longitudinal stepped mirror and a longitudinal stepped compensating mirror; the longitudinal stepped mirror and the longitudinal stepped compensating mirror are mirror-symmetrical in the propagation direction of the parallel light beam; the parallel light beam is first incident on the longitudinal stepped mirror, and after being reflected by the longitudinal stepped mirror and the longitudinal stepped compensating mirror in sequence, it is incident on the transverse optical path delay device; the longitudinal stepped mirror is used to perform distributed phase modulation on the parallel light beam in the horizontal direction, and the longitudinal stepped compensating mirror is used to compensate for the beam transverse shift caused by the longitudinal stepped mirror; the transverse optical path delay device includes a transverse stepped mirror and a transverse stepped compensating mirror; the transverse stepped mirror and the transverse stepped compensating mirror are mirror-symmetrical in the propagation direction of the parallel light beam; the longitudinal stepped compensating mirror is parallel to the transverse stepped mirror; the parallel light beam is first incident on the transverse stepped mirror, and after being reflected by the transverse stepped mirror and the transverse stepped compensating mirror in sequence, it is incident on the digital micromirror array; the transverse stepped mirror is used to perform distributed phase modulation on the parallel light beam in the vertical direction, and the transverse stepped compensating mirror is used to compensate for the beam transverse shift caused by the transverse stepped mirror.

2. The micro Fourier transform spectrometer according to claim 1, characterized in that, the longitudinal stepped mirror is composed of N column stepped units with the stepped direction perpendicular to the horizontal plane, and the longitudinal stepped compensating mirror has the same structure as the longitudinal stepped mirror; the transverse stepped mirror is composed of N row stepped units with the stepped direction parallel to the horizontal plane, and the transverse stepped compensating mirror has the same structure as the transverse stepped mirror.

3. The micro Fourier transform spectrometer according to claim 2, characterized in that, The relative optical path delay generated by the $i$-th column step unit along the horizontal direction of the parallel light beam is ; The relative optical path delay generated by the j-th row-step unit of the parallel light beam in the vertical direction is ; wherein, i = 0, 1, 2, …, N−1; j = 0, 1, 2, …, N−1; θ is the incident angle of the parallel light beam on the surface of the row stepped unit or the column stepped unit.

4. The micro Fourier transform spectrometer according to claim 3, characterized in that, the digital micromirror array is parallel to the transverse stepped compensating mirror, and the digital micromirror array includes N×N digital micromirror units; The process of the digital micromirror array gating the light field array is as follows: By controlling the driving voltage of the digital micromirror array, the rotation angle of the digital micromirror unit is further controlled, so that at the same moment, two light beams of the light field units in the light field array corresponding to the digital micromirror unit (0, 0) and the digital micromirror unit (i, j) are incident on the detector system, where i and j are not both 0 at the same time.

5. The micro Fourier transform spectrometer according to claim 4, wherein, The two light beams gated by the digital micromirror array have a preset optical path difference, and two light beams with linearly increasing optical path differences are sequentially gated by controlling the digital micromirror array and incident on the detector system.

6. The micro Fourier transform spectrometer according to claim 5, wherein, The detector system includes: a focusing mirror and a photodetector; The two light beams gated by the digital micromirror array are incident on the photodetector after being converged by the focusing mirror to generate interference; Define the two light beams gated by the digital micromirror array as a group of light beams; When the digital micromirror array gates the first group of light beams with a first preset optical path difference, a first group of interferogram signals is obtained; When the digital micromirror array gates the second group of light beams with a second preset optical path difference, a second group of interferogram signals is obtained; Until all the interferogram signals are acquired, the spectral information of the parallel light beam is obtained by performing a discrete Fourier transform on all the interferogram signals.

7. A measurement method of the micro Fourier transform spectrometer according to any one of claims 1-6, wherein, it includes the following steps: S1. The light source system is used to emit a parallel light beam and incident it on the optical path delay device; S2. After the parallel light beam undergoes distributed phase modulation by the longitudinal optical path delay device and the transverse optical path delay device in the optical path delay device, a light field array composed of N×N light field units is obtained and incident on the digital micromirror array; S3. By controlling the N×N digital micromirror units in the digital micromirror array, gating of different light field units in the light field array is achieved; S4. After the light beams corresponding to at least two light field units with a preset optical path difference gated by the digital micromirror array enter the detector system to generate interference, interferogram signals are obtained, and then the spectral information of the parallel light beam is acquired.

8. The measurement method of the micro Fourier transform spectrometer according to claim 7, wherein, The step unit height d of the longitudinal stepped mirror and the step unit height h of the transverse stepped mirror satisfy the following relationship: ， where λ min is the minimum wavelength in the parallel light beam.

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