CN113280916A - Fourier transform spectrometer - Google Patents
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Abstract
The invention provides a Fourier transform spectrometer, which realizes spectrum division by using a double grating system on one dimension, so that an optical axis is not folded, the difficulty of adjusting and correcting each element of the system is reduced, and the complexity of the system is reduced. And the band-pass sampling is realized by using a spatial modulation interference system in the other dimension, so that the orthogonal coupling modulation of the dispersion and the interference of the incident light field is realized in two orthogonal directions. The dispersion spectrometer avoids a narrow slit and a large array refrigeration detector which are necessary to be adopted for realizing the infrared high spectral resolution, gets rid of the limitation of a core device, has relatively high luminous flux and signal-to-noise ratio, adopts a static structure, avoids the difficulty in manufacturing and controlling caused by moving parts, and has better reliability, stability and real-time property; the measurement mechanism of spectral segmentation and band-pass sampling is adopted, so that the contradiction of mutual restriction between spectral bandwidth and spectral resolution is solved.
Description
Technical Field
The invention belongs to the technical field of spectral measurement, and particularly relates to a Fourier transform spectrometer based on diffraction interference orthogonal coupling modulation of a double grating.
Background
With the progress of society and the development of science and technology, the infrared spectrum technology has been increasingly widely applied in the fields of physics, chemistry, life, geology, medicine and the like, and plays an important role in the discovery of new materials, new energy sources and unknown world. In recent years, with the appearance and development of high and new technical fields such as meteorological observation, environmental monitoring, space remote sensing detection, military ground object reconnaissance and analysis and the like, higher requirements on the infrared spectrum detection technology and instruments in the aspects of volume and performance are provided due to special application environments and use conditions of the infrared spectrum detection technology and instruments.
For high and new technical fields such as meteorological observation, environmental monitoring, space detection and the like, the limitation of the use environment requires that an infrared spectrum instrument has the characteristics of microminiaturization and staticization, and the detection precision requires that the instrument has the detection performance of wide spectrum range and high resolution. With the continuous upgrading of information requirements, the traditional spectrum measurement technology has a technical bottleneck which is difficult to exceed. For conventional dispersive spectrometers, narrow entrance slits must be used in the mid-wavelength infrared to achieve high resolution, thus limiting the radiant flux received by the instrument. Meanwhile, a large-area array infrared detector array is required to be adopted, and the preparation and refrigeration of the large-area array infrared detector have great difficulty. The Fourier transform infrared spectrometer adopts an interference light splitting mode, has a series of advantages of high luminous flux, multi-spectral channels, high wave number precision and the like, and is a preferred instrument of a high-performance infrared spectrum technology. At present, a time modulation type structure is adopted in a Fourier transform spectrometer which is conventionally applied in a laboratory, and an interferometer generates a large optical path difference through moving mirror scanning so as to obtain high spectral resolution. However, the high-precision moving mirror scanning mechanism and the precise reference light source sampling control system increase the volume and the weight of the instrument, so that the application of the instrument in high and new technical fields such as space detection, meteorological remote sensing, military reconnaissance and the like is limited.
Disclosure of Invention
The invention provides a Fourier transform spectrometer, aiming at overcoming the technical problems of the traditional dispersion spectrometer, a time modulation Fourier transform spectrometer and a space modulation Fourier transform spectrometer. In order to achieve the purpose, the invention adopts the following specific technical scheme:
a Fourier transform spectrometer comprises a spatial modulation interference system for forming an interference light field, and is characterized by further comprising an incident light path arranged on the spatial modulation interference system and a double grating system for dividing a broadband spectrum of the incident light field;
the double-grating system comprises a first grating and a second grating which have the same grating period and are parallel to each other, the first grating and the second grating enable an incident light field to be dispersed into M narrow-band sliced beams in parallel in the direction of an optical axis of the double-grating system, and M is greater than 1;
the dispersion direction of the double grating system and the modulation direction of the spatial modulation interference system are orthogonal in the transverse space, so that the incident light field is orthogonally coupled and modulated by the double grating system and the spatial modulation interference system.
Preferably, the first grating and the second grating are diffraction gratings, and the optical axis of the first diffraction grating is not overlapped with the optical axis of the second diffraction grating, so that the light beam emitted by the first diffraction grating and the N-order diffraction order is incident on the-N-order diffraction order of the second diffraction grating; or the light beam emitted from the first diffraction grating-N diffraction order is incident on the second diffraction grating + N diffraction order to form M narrow-band slice light beams.
Preferably, the first and second diffraction gratings each achieve parallel dispersion by means of a series of equal width, equal period parallel slit structures inscribed on respective opaque substrates; or a series of parallel wire grid structures with equal width and equal period which are all evaporated on respective transparent substrates to realize parallel dispersion.
Preferably, the first grating and the second grating are both prism gratings, and the first prism grating and the second prism grating are oppositely and coaxially arranged, so that an incident light field is parallelly dispersed into M narrow-band sliced beams in a straight line direction along an optical axis of the double grating system.
Preferably, the first prism grating and the second prism grating are both integrated prism gratings, the surfaces of which are engraved with grating structures, or are both integrated gratings formed by gluing a prism and a transmission grating.
Preferably, the incident surface of the prism of the integrated grating is parallel to one groove of the transmission grating, and the included angle between the groove surface of the transmission grating and the bottom surface of the transmission grating is equal to the wedge angle of the prism.
Preferably, the spatial modulation interference system comprises a plane mirror disposed on a reflection optical path of the beam splitter and a multi-stage micro-mirror disposed on a transmission optical path of the beam splitter;
the beam splitter equally divides the M narrow-band slice beams into a first beam and a second beam according to energy; the first light beam is reflected to the plane mirror and then reflected to the beam splitter for the second time, and the second light beam is transmitted to the multi-stage micro mirror and then reflected to the beam splitter;
the reflected light of the first light beam and the reflected light of the second light beam are superposed on the beam splitter to form an interference light field.
Preferably, the multi-stage micro-mirror is of a step-type structure with the same step height d, and the step direction of the multi-stage micro-mirror is orthogonal to the reticle direction of the double grating system, and is used for performing distributed synchronous phase modulation on narrow-band slice light beams with different central wavelengths.
Preferably, the step height d satisfies the following relation:
wherein k is the folding order of the spectral band corresponding to any narrow-band slice beam,
λmaxfor the maximum wavelength in this spectral region,
λminthe minimum wavelength in this spectral range.
Preferably, the fourier transform spectrometer further comprises a collimating mirror arranged in an incident light path of the double grating system, a beam shrinking system and an area array detector which are sequentially arranged in an emergent light path of the plane reflecting mirror;
the collimating lens is used for collimating an incident light field into parallel light;
the area array detector is used for performing photoelectric conversion on the interference light field to form a diffraction interference image.
The invention can obtain the following technical effects:
1. by adopting the diffraction grating with the linear optical axis to carry out dispersion compensation, the double grating system has no optical axis folding phenomenon, the difficulty of adjusting and correcting each element of the system is reduced, the diffraction grating is easy to manufacture, and the manufacturing cost is effectively reduced.
2. By adopting the prism grating for dispersion compensation, the incident light field is subjected to parallel dispersion in the linear direction along the optical axis of the system, so that the whole light path is shorter, the complexity of the system is reduced, the system has smaller volume, and the miniaturization of the system is more facilitated. And the diffraction efficiency is limited by the diffraction order without the grating, so that the utilization rate of the spectrometer on the light energy is increased.
3. Compared with the traditional dispersive spectrometer, the dispersive spectrometer avoids the narrow slit and the large array refrigeration detector which are necessary to be adopted for realizing the infrared high spectral resolution, gets rid of the limitation of core devices, and has relatively high luminous flux and signal-to-noise ratio.
4. Compared with a time modulation Fourier transform spectrometer, the time modulation Fourier transform spectrometer adopts a static structure, avoids the difficulty in manufacturing and controlling caused by moving parts, and has better reliability, stability and real-time performance.
5. Compared with the traditional spatial modulation Fourier transform spectrometer, the spectral spectrum division and band-pass sampling measurement mechanism is adopted, the contradiction of mutual restriction between spectral bandwidth and spectral resolution is solved, and the spectral spectrum and the high spectral resolution can be achieved at the same time.
Drawings
FIG. 1 is an optical path diagram of a Fourier spectrometer using diffraction grating dispersion according to one embodiment of the present invention;
FIG. 2 is a schematic diagram of a dual diffraction grating structure and parallel dispersive optical paths according to one embodiment of the present invention;
FIG. 3 is an optical diagram of distributed phase modulation of a slicing beam by a multi-stage micro-mirror according to one embodiment of the present invention;
FIG. 4 is a schematic diagram of the step heights of the stages of a multi-level micro mirror according to one embodiment of the present invention;
FIG. 5 is a flow chart of a process for fabricating a Fourier spectrometer using diffraction grating dispersion according to an embodiment of the present invention;
FIG. 6 is an optical diagram of a Fourier spectrometer using prism grating dispersion according to one embodiment of the present invention;
FIG. 7 is a flow chart of a process for fabricating a Fourier spectrometer using prism grating dispersion according to an embodiment of the present invention;
FIG. 8 is a schematic view of a unitary prism grating structure according to one embodiment of the present invention;
FIG. 9 is a schematic diagram of an integrated prism grating structure according to one embodiment of the present invention;
FIG. 10 is a schematic diagram of a dual prism grating structure and parallel dispersive optical paths according to one embodiment of the present invention.
Reference numerals:
a double grating system 1, a first diffraction grating 11, a second diffraction grating 12, a first prism grating 13, a prism 131, a transmission grating 132, a second prism grating 14,
The system comprises a spatial modulation interference system 2, a beam splitter 21, a plane mirror 22, a multi-stage micro-mirror 23, a beam shrinking system 3, an area array detector 4, a collimating mirror 5 and a light source 6.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention.
The invention aims to provide a Fourier transform spectrometer, which adopts a double diffraction grating or a double prism grating for dispersion compensation, can utilize the energy of incident light to the maximum extent and realizes the light and small size of the spectrometer. The following will describe a fourier transform spectrometer provided by the present invention in detail by way of specific embodiments.
Referring to the optical path diagram of the fourier spectrometer for dispersion by using a diffraction grating shown in fig. 1, after parallel light enters a double grating system 1, the parallel light is divided into M color-dispersed narrow-band sliced light beams which are arranged in parallel according to the wavelength sequence along the incident direction, wherein M > 1; m narrow-band slice light beams enter a spatial modulation interference system 2 positioned in an emergent light path of the double grating system 1, and are subjected to parallel interference in the spatial modulation interference system 2 to form an interference light field; after the interference light field passes through the beam-shrinking system 3, the diffraction interference image of the respective spectral band corresponding to each narrow-band slice light beam is obtained through the area array detector 4.
The two-grating system 1 includes two first diffraction gratings 11 and two second diffraction gratings 12 having the same grating period. The first diffraction grating 11 is used for performing spectral dispersion on a broadband spectrum of an incident light field according to a wavelength sequence to form M narrow-band divergent light beams; the second diffraction grating 12 is configured to collimate the M dispersed narrow-band diverging light beams to form M parallel narrow-band sliced light beams arranged in a wavelength order.
As shown in fig. 2, the first diffraction grating 11 and the second diffraction grating 12 are arranged in parallel, and the optical axes of the first diffraction grating 11 and the second diffraction grating 12 are not overlapped, so that divergent light beams having different wavelengths and dispersed by the first diffraction grating 11 are incident on the second diffraction grating 12, collimated by the second diffraction grating 12, and then incident in parallel to the spatial modulation interference system 2.
In a preferred embodiment of the present invention, the diverging light beams with respective wavelengths corresponding to the +1 st order diffraction order of the first diffraction grating 11 are incident on the second diffraction grating 12, the second diffraction grating 12 performs secondary diffraction on the incident diverging light beam with +1 st order diffraction order, the light beams with respective wavelengths of the-1 st order diffraction order of the outgoing light beam from the second diffraction grating 12 are adjusted to be parallel light, that is, the light beams with-1 st order diffraction order outgoing from the second diffraction grating 12 are a set of parallel light beams arranged in a wavelength sequence, and each light beam, that is, each narrow-band sliced light beam corresponds to a specific spectral band.
In a preferred embodiment of the present invention, the first diffraction grating 11 and the second diffraction grating 12 implement parallel dispersion by patterning a series of parallel slit structures of equal width and equal period on their opaque substrates or by evaporating a series of parallel wire grid structures of equal width and equal period on their transparent substrates. Therefore, the parallel transmission of each wavelength beam can also be achieved using the + N order diffraction order of the first diffraction grating 11 and the-N order diffraction order of the second diffraction grating 12, or using the-N order diffraction order of the first diffraction grating 11 and the + N order diffraction order of the second diffraction grating 12.
The physical distance between each narrow-band sliced beam corresponds to the spectral spacing of the spectral bands, so that by adjusting the relative distance between the first diffraction grating 11 and the second diffraction grating 12, adjustments of the spectral spacing and the spectral band bandwidth can be made.
In another preferred embodiment of the present invention, reference is made to the optical diagram of a fourier spectrometer with dispersion using a double diffraction grating shown in fig. 6:
after parallel light enters the double grating system 1, the parallel light is divided into M narrow-band slice light beams which are dispersed in color and arranged in parallel according to the wavelength sequence along the incident direction; m narrow-band slice light beams enter a spatial modulation interference system 2 positioned in an emergent light path of the double grating system 1, and are subjected to parallel interference in the spatial modulation interference system 2 to form an interference light field; after the interference light field passes through the beam-shrinking system 3, the diffraction interference image of the respective spectral band corresponding to each narrow-band slice light beam is obtained through the area array detector 4.
The two-grating system 1 includes two first prism gratings 13 and a second prism grating 14 having the same structure. The first prism grating 13 is used for performing spectral dispersion on a broadband spectrum of an incident light field according to a wavelength sequence to form M narrow-band divergent light beams; the second prism grating 14 is used for collimating the M dispersed narrow-band diverging light beams to form M parallel narrow-band sliced light beams arranged in a wavelength order.
As shown in fig. 10, the first prism grating 13 and the second prism grating 14 are arranged coaxially and in an antiparallel manner, so that divergent light beams having different wavelengths and dispersed by the first prism grating 13 are incident on the second prism grating 14, collimated by the second prism grating 14, and then incident in parallel to the spatial modulation interference system 2.
In a preferred embodiment of the present invention, the first prism grating 13 and the second prism grating 14 may be an integrated prism grating as shown in fig. 8, or an integrated prism grating as shown in fig. 9.
For the integrated prism grating, a grating structure is carved on the incident surface of the prism base, and each notch surface of the grating structure is parallel to the bottom surface of the prism base;
for the integrated prism grating, one surface of the prism 131 and the bottom surface of the transmission grating 132 are glued. The prism 131 and the transmission grating 132 are made of the same base material, an incident surface of the prism 131 and a grooved surface of the transmission grating 132 are parallel to each other, and an included angle between the grooved surface of the transmission grating 132 and a bottom surface of the transmission grating 132 and a wedge angle of the prism 131 are equal to each other.
Therefore, the prism 131 and the transmission grating 132 are combined to balance the nonlinear dispersion in opposite directions from the prism 131 and the transmission grating 132, respectively, so that the light beam of a certain central wavelength passing through the first prism grating 13 is not deflected, and the light beams on both sides of the central wavelength are deflected to both sides with respect to the central wavelength.
And because the first prism grating 13 and the second prism grating 14 are oppositely arranged in parallel, the broadband spectrum incident in parallel is collimated by the second prism grating 14 after being dispersed by the first prism grating 13, the emergent beam is modulated into a group of parallel narrow-band sliced beams according to the wavelength sequence, and each narrow-band sliced beam corresponds to a specific spectrum section.
In a preferred embodiment of the invention, a wavelength beam in the first diffraction order of the first prism grating 13 is selected as the "unbiased" beam, and the spectral spacing between each of the narrowband sliced beams in the outgoing beam can be varied by varying the spacing between the first prism grating 13 and the second prism grating 14.
With continued reference to either FIG. 1 or FIG. 6, the spatially modulated interference system 2 is configured to perform parallel interference on each of the narrowband sliced beams to form an interference light field, and includes a plane mirror 22 disposed in the reflected optical path of the beam splitter 21 and a multi-stage micro-mirror 23 disposed in the transmitted optical path of the beam splitter 21.
The beam splitter 21 is placed in the exit light path of the second diffraction grating 12 along a direction forming an angle of 45 degrees with the optical axis, the parallel narrow-band sliced light beams of the M spectral bands exiting from the double grating system 1 are equally divided into two light beams according to energy, the first light beam is reflected to the plane mirror 6, and the second light beam is incident to the multistage micromirror 23 through the beam splitter 21.
Each narrow-band slice beam with different spectral bands in the first light beam is reflected by the plane mirror 6 and reflected after being modulated by the multi-stage micro-mirror 23, and each narrow-band slice beam in the second light beam is superposed on the beam splitter 21 to form an interference light field.
In a preferred embodiment of the present invention, the step direction of the multi-stage micromirror 23 is orthogonal to the scribe line direction of the double grating system 1, so that the incident light field can be orthogonally coupled and modulated by the double grating system 1 and the spatial modulation interference system 2. Therefore, for the narrow-band slice light beam of each spectral band, the optical path difference corresponding to the interference light field is subjected to distributed modulation of different steps of the multi-stage micro-mirror 23, the diffraction interference image obtained on the area array detector 4 has two dimensions, one dimension corresponds to the spectral division of parallel dispersion, the other dimension corresponds to the band-pass sampling of spatial modulation, and finally, the spectral information of the wide spectral band is obtained through spectral restoration and spectral splicing.
Therefore, compared with the traditional spatial modulation Fourier transform spectrometer, the method solves the contradiction of mutual restriction between the spectral bandwidth and the spectral resolution, and can simultaneously combine a wide spectral range and high spectral resolution.
As shown in the phase modulation optical path diagram of fig. 3, the multi-level micro-mirrors 23 perform distributed synchronous phase modulation on the narrowband sliced light beams with different center wavelengths by using different step heights of each micro-mirror thereon, and because the multi-level micro-mirrors 23 have a step-type structure with the same step height d, the general step height d of the multi-level micro-mirrors 23 is obtained by combining the step height diagrams of each level shown in fig. 4:
B1the corresponding broken line region is corresponding to the first spectral band lambda1Corresponding step height distribution region in the lossless sampling of narrow-band slice beam bandwidth, B2The corresponding break line region is for the second spectral band λ2The narrow-band slice beam bandwidth of (2) is a corresponding step height distribution area when sampling is not damaged. The same can obtain the lambda3，λ4，…，λMAnd overlapping the distribution areas of all the step heights in the step height distribution areas corresponding to the narrow-band slice light beams, and taking the intersection of the step height distribution areas, namely the general step sampling height when the narrow-band slice light beams of all the spectral bands are parallelly sampled and no spectrum aliasing occurs. The step height d at this time satisfies the following equation:
wherein k is the folding order of the spectral band corresponding to any narrow-band slice beam,
λmaxfor the maximum wavelength in this spectral region,
λminthe minimum wavelength in this spectral range.
With continued reference to fig. 1 or fig. 6, in another preferred embodiment of the present invention, a collimating mirror 5 is further included in the incident light path of the dual grating system 1, and the collimating mirror 5 may be a cylindrical collimating mirror for collimating the incident light field with a certain divergence angle from the light source 6 into a parallel light beam, which is incident into the dual grating system 1.
Fig. 5 shows a manufacturing process of a fourier spectrometer using a double diffraction grating for dispersion according to an embodiment of the present invention, and the manufacturing process is shown in fig. 5:
divergent laser with the wavelength of the central wavelength of the system is used as a light source 6, the distance between the laser and a collimating mirror 5 is adjusted, and the collimation of emergent light is ensured;
placing a first diffraction grating 11 in a collimation light path, placing a second diffraction grating 12 in a transmission light path of the first diffraction grating 11 in parallel along the +1 st order diffraction angle direction, and performing center alignment;
adjusting the relative position between the two diffraction gratings to ensure that the transmission direction of the laser beam emitted by the second diffraction grating 12 does not deflect relative to the transmission direction of the incident beam of the first diffraction grating 11;
placing a beam splitter 21 in an emergent light path of the second diffraction grating 12 along a direction forming an angle of 45 degrees with an optical axis, placing a plane mirror 22 in a reflection light path of the beam splitter 21, placing a multi-stage micro-mirror 23 in a transmission light path of the beam splitter 21, making the step direction of the multi-stage micro-mirror be vertical to the reticle direction of the double grating system 1, and aligning the center of the multi-stage micro-mirror;
adjusting the relative position between the plane mirror 22 and the multi-stage micro-mirror 23 to make the laser narrow-band slicing beam perpendicular to the step direction of the multi-stage micro-mirror 23 and generate stable interference fringes;
placing the beam-shrinking system 3 in the emergent light path of the plane mirror 22, and performing center alignment;
placing the area array detector 4 at the image plane position of the beam-shrinking system 3, and adjusting the position of the area array detector 4 relative to the beam-shrinking system 3 to enable the interference fringes to be clearly imaged, namely forming a diffraction interference image;
and finally, replacing the laser light source with a broadband light source.
FIG. 7 shows a flow chart for making a Fourier spectrometer using prism grating dispersion according to another preferred embodiment of the present invention, see FIG. 7;
divergent laser with the wavelength of the central wavelength of the system is used as a light source 6, the distance between the laser and a collimating mirror 5 is adjusted, and the collimation of emergent light is ensured;
placing the first prism grating 13 in a collimation light path, placing the second prism grating 14 in an emergent light path of the first prism grating 13 coaxially and in an anti-parallel manner, and performing center alignment;
adjusting the relative position between the two prism gratings to ensure that the transmission direction of the laser beam emitted by the double grating system 1 has no deflection;
placing a beam splitter 21 in an emergent light path of the second prism grating 14 along a direction forming an angle of 45 degrees with an optical axis, placing a plane mirror 22 in a reflection light path of the beam splitter 21, placing a multi-stage micro-mirror 23 in a transmission light path of the beam splitter 21, making the step direction of the multi-stage micro-mirror be vertical to the groove line direction of the double grating system 1, and aligning the centers of the multi-stage micro-mirror and the transmission light path;
adjusting the relative position between the plane mirror 22 and the multi-stage micro-mirror 23 to make the laser narrow-band slicing beam perpendicular to the step direction of the multi-stage micro-mirror 23 and generate stable interference fringes;
placing the beam-shrinking system 3 in the emergent light path of the plane mirror 22, and performing center alignment;
placing the area array detector 4 at the image plane position of the beam-shrinking system 3, and adjusting the position of the area array detector 4 relative to the beam-shrinking system 3 to enable the interference fringes to be clearly imaged, namely forming a diffraction interference image;
and finally, replacing the laser light source with a broadband light source.
According to the invention, the two transmission type diffraction gratings which are easier to manufacture are used for carrying out spectrum diffraction dispersion on the incident beam, so that the manufacturing cost of the spectrometer can be reduced to a certain extent; the use of the double-prism grating for the spectral division of the incident beam is superior to the use of the double-diffraction grating in the aspects of improving the utilization rate of light energy and lightening the spectrometer.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
The above embodiments of the present invention should not be construed as limiting the scope of the present invention. Any other corresponding changes and modifications made according to the technical idea of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. A fourier transform spectrometer comprising a spatially modulated interference system for forming an interference light field, characterized in that the fourier transform spectrometer further comprises a double grating system disposed in an incident light path of the spatially modulated interference system for splitting a broadband spectrum of the incident light field;
the double grating system comprises a first grating and a second grating which have the same grating period and are parallel to each other, the first grating and the second grating enable the incident light field to be dispersed into M narrow-band sliced beams in parallel in the direction of an optical axis of the double grating system, and M is greater than 1;
the dispersion direction of the double grating system and the modulation direction of the spatial modulation interference system are orthogonal to each other in a transverse space, so that the incident light field is subjected to orthogonal coupling modulation by the double grating system and the spatial modulation interference system.
2. The fourier transform spectrometer of claim 1, wherein the first grating and the second grating are diffraction gratings, and an optical axis of the first diffraction grating is not coincident with an optical axis of the second diffraction grating, so that the beam emitted from the first diffraction grating + N-th diffraction order is incident on the second diffraction grating-N-th diffraction order; or the light beams emitted from the first diffraction grating to the N-order diffraction order are made to enter the second diffraction grating and the + N-order diffraction order to form M narrow-band slice light beams.
3. The fourier transform spectrometer of claim 2, wherein the first and second diffraction gratings each achieve parallel dispersion by a series of equal width, equal period parallel slit structures inscribed on respective opaque substrates; or a series of parallel wire grid structures with equal width and equal period which are all evaporated on respective transparent substrates to realize parallel dispersion.
4. The fourier transform spectrometer of claim 1, wherein the first and second gratings are prism gratings, the first and second prism gratings being oppositely and coaxially positioned such that the incident light field is dispersed in parallel into M of the narrowband sliced beams in a straight direction along the optical axis of the dual grating system.
5. The Fourier transform spectrometer of claim 4, wherein the first prism grating and the second prism grating are both integral prism gratings formed by engraving grating structures on the surface of a prism base, or are both integrated gratings formed by gluing a prism and a transmission grating.
6. The fourier transform spectrometer of claim 5, wherein the entrance surface of the prism base of the integrated grating is parallel to one of the grooves of the transmission grating, and the included angle between the groove surface of the transmission grating and the bottom surface of the transmission grating is equal to the wedge angle of the prism base.
7. The fourier transform spectrometer of claim 1, wherein the spatially modulated interference system comprises a planar mirror disposed in a reflected optical path of a beam splitter and a multi-stage micro-mirror disposed in a transmitted optical path of the beam splitter;
the beam splitter divides the M narrow-band slice beams into a first beam and a second beam according to energy; the first light beam is reflected to the plane mirror and then reflected to the beam splitter for the second time, and the second light beam is transmitted to the multi-stage micro mirror and then reflected to the beam splitter;
and the reflected light of the first light beam and the reflected light of the second light beam are superposed on the beam splitter to form the interference light field.
8. The fourier transform spectrometer of claim 7, wherein the multi-stage micro-mirrors are stepped structures having the same step height d, and the step direction of the multi-stage micro-mirrors is orthogonal to the reticle direction of the dual grating system for distributed synchronous phase modulation of the narrow-band sliced beams of different center wavelengths.
9. The fourier transform spectrometer of claim 8, wherein the step height d satisfies the following relationship:
wherein k is the folding order of the spectral band corresponding to any one of the narrow-band sliced beams,
λmaxfor the maximum wavelength in this spectral region,
λminthe minimum wavelength in this spectral range.
10. The fourier transform spectrometer of claim 1, further comprising a collimating mirror disposed in an incident optical path of the double grating system, a beam reduction system disposed in an exit optical path of the plane mirror in sequence, and an area array detector;
the collimating lens is used for collimating the incident light field into parallel light;
the area array detector is used for performing photoelectric conversion on the interference light field to form a diffraction interference image.
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| CN101251484A (en) * | 2008-04-10 | 2008-08-27 | 中国科学院长春光学精密机械与物理研究所 | Miniature fourier transform spectrometer based on modulation |
| CN103913231A (en) * | 2014-03-10 | 2014-07-09 | 中国科学院长春光学精密机械与物理研究所 | Spatial-temporal union modulation Fourier transform imaging spectrometer based on light beam splitter |
| CN107101722A (en) * | 2017-04-06 | 2017-08-29 | 西安交通大学 | A kind of broadband linear polarization imaging method based on Mach Zehnder interferometer |
| CN112129409A (en) * | 2020-08-19 | 2020-12-25 | 中国科学院西安光学精密机械研究所 | Interference spectrum system based on band-pass sampling technology and target spectrum information acquisition method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101251484A (en) * | 2008-04-10 | 2008-08-27 | 中国科学院长春光学精密机械与物理研究所 | Miniature fourier transform spectrometer based on modulation |
| CN103913231A (en) * | 2014-03-10 | 2014-07-09 | 中国科学院长春光学精密机械与物理研究所 | Spatial-temporal union modulation Fourier transform imaging spectrometer based on light beam splitter |
| CN107101722A (en) * | 2017-04-06 | 2017-08-29 | 西安交通大学 | A kind of broadband linear polarization imaging method based on Mach Zehnder interferometer |
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