Raman spectroscopic imaging apparatus and method for gas detection

Abstract

The application provides a Raman spectrum imaging device and method for gas detection, wherein the device comprises: a common-path interferometer, a moving mirror for generating a time-varying optical path difference is arranged in the common-path interferometer; the common-path interferometer comprises: a beam splitter for transmitting and reflecting light beams; first and second mirror groups for reflecting and changing the optical path of the light beams; the first mirror group comprises oppositely arranged first concave mirrors and first reflecting mirrors, and the second mirror group comprises oppositely arranged second concave mirrors and second reflecting mirrors; and an optical path adjusting assembly arranged between the first and second mirror groups, the optical path adjusting assembly is used for adjusting the optical path based on time. The Raman spectrum imaging device for gas detection has the beneficial effects of high adjustment precision and strong stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical technology, in particular to a Raman spectrum imaging device and method for gas detection. BACKGROUND

[0002] The basic principle of Raman spectrum is that the incident photons interact with molecules (or atoms), non-elastic scattering occurs, and light with a specific frequency shift is generated, i.e. Raman scattering light, the frequency shift matches the vibration-rotation energy level of the molecule, and therefore can be used for detection of hydrogen and other gases. Due to the low Raman scattering cross section of the gas, the application of Raman spectrum in gas sensing is limited, and the use of Fourier spectrometer can improve the intensity of the Raman signal.

[0003] The Fourier Raman spectrum method can realize full-band simultaneous scanning, greatly shortening the spectrum scanning time, and the Fourier transform spectrometer also has the advantages of high wave number accuracy, high resolution, large light flux, high signal-to-noise ratio, and low stray light, which can quickly, simply and repeatedly perform non-destructive qualitative analysis. For the characteristics of low Raman signal intensity, the Fourier transform spectrum method can obtain higher quality spectrum. The core of the Fourier transform Raman spectrum imaging technology is the interferometer. The existing interference spectrum (imaging) technology mainly has three types: time modulation type (dynamic) based on Michelson interferometer, space modulation type (static) based on transverse shear interferometer, and time-space combined modulation type (static) based on transverse shear interferometer. Based on these technologies, a variety of interference spectrum (imaging) instruments have emerged, but they often have their own defects. The time modulation type interference spectrum (imaging) instrument generates a changing optical path difference through the movement of the moving mirror in the Michelson interferometer, and obtains the spectral information by Fourier transforming the interference fringes obtained at different optical path differences. This technology has high light flux and high signal-to-noise ratio, and in particular, the spectral resolution can be very high by generating a large optical path difference through the linear motion of the moving mirror, but because the speed and attitude control of the moving mirror in the motion requires high calibration accuracy of the interferometer, the optical-mechanical stability is poor, and it is difficult to apply to motion platforms such as vehicle, airborne, shipborne, mobile robot, and satellite.

[0004] The space modulation type relies on the common-path transverse shear interferometer, and has high stability, good real-time performance, and simple structure, but because the two beams emitted by the beam splitter in the common-path interference spectroscopy technology travel along the same route, they cannot produce a changing optical path difference, and thus cannot obtain the interference patterns at different optical path differences, and thus cannot perform Fourier transformation to obtain the spectrum.

[0005] The time-space combined modulation type has similar structure to the space modulation type, high stability, and higher detection sensitivity than the space modulation interference spectrometer and the dispersive spectrometer, but requires high stability of the platform, and the spectral resolution is similar to the space modulation type and is relatively low. SUMMARY

[0006] In view of the above, the present application proposes a Raman spectrum imaging device and method for gas detection to solve the above problems.

[0007] The present application provides a Raman spectrum imaging device for gas detection, comprising:

[0008] A common-path interferometer, wherein a moving mirror is arranged in the common-path interferometer for generating a time-varying optical path difference;

[0009] The common-path interferometer comprises a beam splitter for transmitting and reflecting a light beam;

[0010] A first mirror group and a second mirror group are arranged for reflecting and changing the optical path of the light beam; the first mirror group

[0011] The first mirror group comprises a first concave mirror and a first reflecting mirror arranged oppositely, and the second mirror group comprises a second concave mirror and a second reflecting mirror arranged oppositely;

[0012] An optical path adjustment assembly is arranged between the first mirror group and the second mirror group, and the optical path adjustment assembly is used for adjusting the optical path based on time.

[0013] In at least one embodiment, the optical path adjustment assembly comprises a third mirror group, a fourth mirror group, and a plane mirror;

[0014] The third mirror group comprises a pair of first mirror surface and second mirror surface arranged parallel to each other, and the fourth mirror group comprises a pair of third mirror surface and fourth mirror surface arranged parallel to each other;

[0015] The light beam enters the common-path interferometer, and is divided into a first transmitted light beam and a first reflected light beam after passing through the beam splitter. The first transmitted light beam is reflected by the first mirror group, the third mirror group, the plane mirror, and the second mirror group in sequence, and then returns to the beam splitter, and is divided into a second transmitted light beam and a second reflected light beam. The first reflected light beam is reflected by the second mirror group, the fourth mirror group, the plane mirror, and the first mirror group in sequence, and then returns to the beam splitter, and is divided into a third transmitted light beam and a third reflected light beam. The second transmitted light beam and the third reflected light beam are emitted in the same direction, and the third transmitted light beam and the second reflected light beam are emitted in the same direction.

[0016] In at least one embodiment, the optical path adjustment assembly further comprises a motor, and the motor drives the third mirror group to move.

[0017] In at least one embodiment, the third mirror group moves in one of rotation, swing, and linear movement.

[0018] In at least one embodiment, a pre-component is further included, arranged at an entrance of the common-path interferometer, including a laser and a parabolic mirror, the laser is arranged towards a focal point of the parabolic mirror, for emitting laser to the gas to be detected and exciting scattered light; the parabolic mirror is used for converging the scattered light to the same direction and emitting to the common-path interferometer.

[0019] In at least one embodiment, the pre-component further includes an optical filter arranged between the parabolic mirror and the common-path interferometer, for selecting light of a specific waveband.

[0020] In at least one embodiment, a converging module, a detection module and a processing module are further included, the converging module is used for converging the light beams emitted from the common-path interferometer and forming interference imaging to the detection module; the detection module collects the interference fringe signals and converts them into electrical signals, and sends them to the processing module; the processing module restores the spectral information according to the electrical signals.

[0021] The embodiments of the present application further provide a Raman spectrum imaging method for gas detection, which is implemented by using the Raman spectrum imaging device for gas detection as described above, and the Raman spectrum imaging device for gas detection is used in a time-modulated working mode by arranging the optical path adjusting component based on time-varying optical path in the common-path interferometer.

[0022] In at least one embodiment, the following steps are included:

[0023] S10: the pre-component emits laser to the gas to be detected, excites light beams and emits them to the common-path interferometer;

[0024] S20: the light beams are divided into a first transmitted light beam and a first reflected light beam after passing through the beam splitter, the first transmitted light beam is reflected by the first mirror group, the third mirror group, the plane mirror and the second mirror group in sequence and then returns to the beam splitter, and is divided into a second transmitted light beam and a second reflected light beam; the first reflected light beam passes through the second mirror group, the fourth mirror group, the plane mirror and the first mirror group in sequence and then returns to the beam splitter, and is divided into a third transmitted light beam and a third reflected light beam; the second transmitted light beam and the third reflected light beam are emitted in the same direction, and the third transmitted light beam and the second reflected light beam are emitted in the same direction;

[0025] S30: the converging module forms interference of the light beams emitted from the common-path interferometer and images them to the detection module;

[0026] S40: the detection module converts the interference fringes into electrical signals and sends them to the processing module;

[0027] S50: the processing module restores the electrical signal into a spectrum signal.

[0028] In at least one embodiment, the step S50 further comprises:

[0029] S51: the processing module restores the electrical signal into a spectrum signal based on a Fourier transform algorithm.

[0030] Compared with the prior art, the Raman spectrum imaging device for gas detection provided in the application has the beneficial effects of high stability and adjustable optical path difference by means of a common-path interferometer, so that two light beams pass through the same mirror surface, thereby reducing the interference caused by external factors, and a concave mirror is used to maintain the stability of the optical path. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is an optical principle diagram of an embodiment of the Raman spectrum imaging device for gas detection in the application;

[0032] Figure 2 is Figure 1 a structural schematic diagram of an optical path adjusting assembly in the Raman spectrum imaging device for gas detection shown in the figure;

[0033] Figure 3 is an optical principle diagram of another embodiment of the Raman spectrum imaging device for gas detection in the application;

[0034] Figure 4 is a step flowchart of an embodiment of the Raman spectrum imaging method for gas detection in the application.

[0035] Reference signs: 100 - Raman spectrum imaging device for gas detection; 1 - beam splitter; 2 - first concave mirror; 3 - first reflecting mirror; 4 - second concave mirror; 5 - second reflecting mirror; 6 - plane mirror; 7 - third mirror surface; 8 - fourth mirror surface; 9 - first mirror surface; 10 - second mirror surface; 11 - incident light beam; 12 - first outgoing light beam; 13 - second outgoing light beam; 14 - laser; 15 - parabolic mirror; 16 - gas to be detected; 17 - optical filter; 18 - condenser; 19 - motor; 20 - first notch filter; 21 - second notch filter; 22 - first converging lens; 23 - second converging lens; 24 - first photoelectric converter; 25 - second photoelectric converter; 26 - processing module. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0037] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0038] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0039] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0040] The following disclosure provides many different embodiments, or examples, for implementing different structures of the present application. For the purpose of simplification, the elements and arrangements of the particular examples are described in the following disclosure. Of course, they are merely examples and are not intended to limit the present application. Moreover, the present application can repeatedly refer to reference numerals and / or reference letters in different examples, and such repetition is for the purpose of simplification and clarity, and does not itself indicate a relationship between the various embodiments and / or arrangements being discussed. In addition, the present application provides examples of various specific processes and materials, but those of ordinary skill in the art can realize the application of other processes and / or the use of other materials.

[0041] Referring to Figure 1 The present application provides a Raman spectrum imaging device 100 for gas detection, comprising:

[0042] A common-path interferometer, wherein a moving mirror is arranged for generating a time-varying optical path difference;

[0043] The common-path interferometer comprises a beam splitter 1 for transmitting and reflecting a light beam;

[0044] A first mirror group and a second mirror group for reflecting and changing the optical path of the light beam; the first mirror group comprises a first concave mirror 2 and a first mirror 3 arranged oppositely, and the second mirror group comprises a second concave mirror 4 and a second mirror 5 arranged oppositely;

[0045] An optical path adjusting assembly arranged between the first mirror group and the second mirror group, for adjusting the optical path based on time.

[0046] It should be explained that the beam splitter 1 is a semi-transparent and semi-reflective beam splitter 1, which can divide the incident light beam 11 into transmitted and reflected light beams. The first mirror group and the second mirror group are cat-eye mirrors, i.e. each of them comprises a concave mirror and a mirror, and the mirror is arranged at the focal point of the concave mirror, so that any light beam incident on the concave mirror will be emitted from the axisymmetric position of the concave mirror. Similarly, a hollow structure or a solid structure composed of mirror-coated surfaces can also be used. In this way, when multiple light beams pass through the mirror group at the same time, they can still complete the optical path transformation without interfering with each other. The size of the mirror should be limited so as not to affect the emission and incidence of the light beam. In the present embodiment, the first mirror group is arranged in the target direction of the incident light beam 11, and the second mirror group is arranged in the direction perpendicular to the incident light beam 11.

[0047] The optical path adjusting assembly is arranged between the first mirror group and the second mirror group, and the light beam passes through the optical path adjusting assembly after being emitted from the first mirror group or the second mirror group, so as to adjust the optical path difference. Referring to Figure 2 Some specific structures of the optical path adjusting assembly that can be used are shown in the following figures.

[0048] In one embodiment, the optical path adjustment assembly comprises a third mirror group, a fourth mirror group and the plane mirror 6, the third mirror group comprises a pair of mutually parallel first mirror surface 9 and second mirror surface 10, the fourth mirror group comprises a pair of mutually parallel third mirror surface 7 and fourth mirror surface 8:

[0049] The incident light beam 11 enters the common-path interferometer, and is divided into a first transmitted light beam and a first reflected light beam after passing through the beam splitter 1. The first transmitted light beam is returned to the beam splitter 1 after being reflected by the first mirror group, the third mirror group, the plane mirror 6 and the second mirror group in sequence, and is divided into a second transmitted light beam and a second reflected light beam. The first reflected light beam is returned to the beam splitter 1 after being reflected by the second mirror group, the fourth mirror group, the plane mirror 6 and the first mirror group in sequence, and is divided into a third transmitted light beam and a third reflected light beam. The second transmitted light beam and the third reflected light beam exit in the same direction, and the third transmitted light beam and the second reflected light beam exit in the same direction.

[0050] It needs to be explained that the first mirror surface 9 and the second mirror surface 10 in the optical path adjustment assembly are mutually parallel, the third mirror surface 7 and the fourth mirror surface 8 are mutually parallel, and the two groups of mirrors are strictly parallel. In this embodiment, the included angle is controlled within 5". In this way, the incident surface and the exit surface also remain strictly parallel after the light beam passes through the third mirror group or the fourth mirror group.

[0051] In this embodiment, the position of the fourth mirror group is fixed, and the attitude is inclined relative to the initial incident direction of the light beam, so as to avoid the dispersion of light at the zero-crossing position. The position of the third mirror group is relatively fixed, and can be adjusted synchronously. During the adjustment process, the first mirror surface 9 and the second mirror surface 10 remain strictly parallel, and the second mirror surface 10 can compensate for the light beam deviation caused by the first mirror surface 9, so as to compensate for the light beam deviation caused by the transmission shaft vibration during the rotation process, ensure that the direction of the exit light beam does not produce deflection, realize the self-compensation structure of the attitude error caused by the shaft system vibration during the rotation of the moving mirror, and ensure the collimation of the two interference light beams of the interferometer. The third mirror group is located at the moving arm of the interferometer, and the fourth mirror group is located at the static arm of the interferometer. The two pairs of mirror groups eliminate the dispersion at the zero optical path difference position and make the two light beams for interference pass through the same path in space, thereby realizing the high stability of the interferometer. In other embodiments, the positions of the third mirror group and the fourth mirror group on the two arms can be exchanged.

[0052] The rotation of the first mirror surface 9 and the second mirror surface 10 realizes the change of the optical path, and the combination of the third mirror surface 7 and the fourth mirror surface 8 forms a periodically changed optical path difference near the zero optical path difference position. The optical path difference changes from -L to 0 and then from 0 to +L, and passes through the position of the zero optical path difference, wherein L is the maximum optical path difference. The adjustable setting of the third mirror group and the fourth mirror group realizes the adjustment near the zero optical path difference, thereby realizing the zero adjustment of the optical path difference, and solving the defect that the traditional interferometer cannot adjust the optical path difference to zero.

[0053] Please refer to Figure 3In one embodiment, the optical path adjustment assembly is further provided with a motor 19, which drives the third mirror group to move, so as to change the optical path. In this embodiment, the movement of the third mirror group is generated by the rotation of the motor 19, so that the interference patterns corresponding to different optical path differences at different moments can be obtained. The motor 19 drives the first mirror 9 and the second mirror 10 in the third mirror group to rotate synchronously. The output shaft of the motor 19 can be periodically rotated or periodically swung.

[0054] In one embodiment, the movement of the third mirror group is in the form of rotation, swinging or linear movement. In this embodiment, the movement is in the form of rotation, which does not mean that the movement form is limited.

[0055] In one embodiment, the apparatus further comprises a pre-assembly arranged at the entrance of the common-path interferometer, which comprises a laser 14 and a parabolic mirror 15. The laser 14 is arranged towards the focal point of the parabolic mirror 15, and is used to emit laser to the gas 16 to be measured and excite scattered light. The parabolic mirror 15 is used to converge the scattered light to the same direction and emit the light to the common-path interferometer. The gas 16 to be measured is arranged at the focal point of the parabolic mirror 15, so that when the gas is irradiated by the laser, the light beams emitted by the gas are reflected by the parabolic mirror 15 to the same direction, which is convenient for subsequent processing.

[0056] In one embodiment, the pre-assembly further comprises a filter 17 arranged between the parabolic mirror 15 and the common-path interferometer, which is used to select light of a specific waveband. The filter 17 is arranged to prevent excitation light and ambient stray light from entering the common-path interferometer, so as to ensure the accuracy of the spectrum obtained by the interferometer.

[0057] In one embodiment, the apparatus further comprises a converging module, a detection module and a processing module 26. The converging module is used to converge the light beams emitted from the common-path interferometer and form an interference image to the detection module. The detection module collects the interference fringe signals and converts the signals into electrical signals, which are sent to the processing module 26. The processing module 26 restores the spectrum information according to the electrical signals.

[0058] In this embodiment, the converging module includes a first converging mirror 22, a second converging mirror 23, a first notch filter 20 and a second notch filter 21. The second transmitted light beam and the third reflected light beam have the same exit direction to form a second exit light beam 13. After passing through the second notch filter 21, the interference fringes are formed at the second converging mirror 23. The second reflected light beam and the third transmitted light beam have the same exit direction to form a first exit light beam 12. After being turned by the folding mirror 18, the interference fringes are formed at the first converging mirror 22 after passing through the first notch filter 20, forming interference signals, which are respectively imaged on the first photoelectric converter 24 and the second photoelectric converter 25 of the detection module. After being collected, amplified, denoised and processed, the interference signals are transmitted to the processing module 26. The processing module 26 is inverted to obtain two spectral imaging images of the incident light beam 11. Superimposing the two spectral imaging images, a target spectral imaging image with higher signal-to-noise ratio can be obtained.

[0059] The first notch filter 20 and the second notch filter 21 filter the Rayleigh scattering signals and the possible fluorescent signals to avoid interference with the spectrum. -3 In order to avoid the Rayleigh scattering from submerging the Raman signal and affecting the detection of the Raman spectrum, the light beam must be filtered before the exit signal enters the detector.

[0060] The first converging mirror 22 and the second converging mirror 23 converge the interference fringes of the interferometer to be imaged on the detection module.

[0061] The detection module collects the interference fringe signals at different times, converts them into electrical signals, and performs amplification, filtering and other processing to collect the original measurement data for the inversion of the spectral, image and other parameters of the target light beam. In this embodiment, the detection module includes a first photoelectric converter 24 and a second photoelectric converter 25. According to the different detection light sources, the detector can be a CCD or other photoelectric conversion device.

[0062] The processing module 26 is used for data processing and analysis of the electrical signals collected by the detection module, including but not limited to pre-processing of interference image raw data, error correction, radiometric calibration correction, Fourier transform and the like, completing the recovery process of the spectrum, and obtaining the target spectrum or high-resolution spectral image.

[0063] The embodiment of the application also provides a Raman spectral imaging method for gas detection, which is realized by using the above Raman spectral imaging device 100 for gas detection. The optical path adjustment assembly based on time-varying optical path is arranged in the common-path interferometer, and the Raman spectral imaging device 100 for gas detection is used in the time-modulated working mode.

[0064] Please refer to Figure 4In an embodiment, the method comprises the following steps:

[0065] S10: The pre-assembly component emits laser to the gas to be detected 16, and the light beam is emitted and incident to the common-path interferometer;

[0066] S20: After the light beam passes through the beam splitter 1, it is divided into a first transmitted light beam and a first reflected light beam. The first transmitted light beam is reflected by the first mirror group, the third mirror group, the plane mirror 6, and the second mirror group in sequence and then returns to the beam splitter 1, and is divided into a second transmitted light beam and a second reflected light beam. The first reflected light beam passes through the second mirror group, the fourth mirror group, the plane mirror 6, and the first mirror group in sequence and then returns to the beam splitter 1, and is divided into a third transmitted light beam and a third reflected light beam. The second transmitted light beam and the third reflected light beam are emitted in the same direction, and the third transmitted light beam and the second reflected light beam are emitted in the same direction.

[0067] S30: The converging module forms interference from the light beam emitted from the common-path interferometer and images on the detection module;

[0068] S40: The detection module converts the interference fringes into an electrical signal and sends it to the processing module 26;

[0069] S50: The processing module 26 restores the electrical signal to a spectral signal.

[0070] Because in step S20, both light beams emitted from the interferometer have experienced the same reflection path, subtle changes in the interferometer do not affect the optical path difference, achieving structural stability.

[0071] In an embodiment, step S50 further comprises:

[0072] S51: The processing module 26 restores the electrical signal to a spectral signal based on the Fourier transform algorithm.

[0073] The method for restoring the electrical signal to a spectral image in this embodiment is the Fourier transform algorithm, and other algorithms that can restore the spectrum are not limited.

[0074] The Raman spectrum imaging device 100 and method for gas detection of the present application have the following advantages:

[0075] (1) Wide application range. Traditional Fourier Raman is based on a Michelson interferometer, and the two arms of the core interferometer component are relatively independent, that is, a non-common-path interferometer. The non-common-path interferometer has poor anti-interference ability. The present application adopts a common-path splitting method, which greatly improves the stability of the Raman interferometer spectrometer and has strong anti-interference ability. Therefore, the traditional basic application cannot be applied to vehicle-mounted motion platforms, airborne platforms, ship-mounted platforms, mobile robots, and satellite-mounted platforms. Therefore, the application occasions are more, and the application fields will be wider.

[0076] (2) Continuously varying optical path difference can be obtained. In traditional common-path interferometers, the optical path lengths of the two arms are always fixed or the same, so the optical path difference between the two arms is fixed and cannot achieve time modulation mode. This application generates different optical path differences at different times by moving the moving mirror in the common-path interferometer, and then obtains the time integral interferogram, thereby retrieving the spectral information of the target.

[0077] (3) It can realize the optical path difference from -L to +L. In this application, optical path adjustment devices are set in both arms of the interferometer, and the attitude of the optical path adjustment devices in the moving arm can be rotated and changed. Therefore, it can realize the optical path difference from -L to 0 and then from 0 to +L, and pass through the position of zero optical path difference, thus providing the prerequisite for achieving the spectral restoration of the target and realizing time modulation.

[0078] (4) It can achieve self-compensation for the wobbling error of the rotating mirror axis, realizing permanent collimation of the interferometer. By setting the beam path, the incident surface and the exit surface of the beam passing through the optical path adjustment device are made strictly parallel.

[0079] This ensures that even if the optical path adjustment device tilts to a certain extent due to the shaking of the rotating shaft, the emitted beam remains parallel to the incident beam, and the beam propagation direction is not deflected, thus achieving the effect of controlling the shaking of the axis system when the moving mirror rotates.

[0080] The self-compensation of the attitude error caused by the interference is achieved, thus realizing immunity to the interferometer wobbling error and permanent collimation of the two interference beams.

[0081] (5) High interference modulation can be achieved. A pair of instruments with consistently aligned postures are installed in the moving arm of the interferometer.

[0082] If optical path adjustment devices are used, and the incident and exit surfaces of the beams of each optical path adjustment device are strictly parallel, then according to the principle of optical path reversibility, the beam incident on the previous optical path adjustment device will be compensated by the next optical path adjustment device even if its spatial position shifts due to the change in the attitude of the optical path adjustment device. This ensures that the beam not only maintains the ideal propagation direction when the attitude has not changed, but also that its spatial position when returning to the beam splitter is also the ideal position when the attitude has not changed. This makes the interfering beams completely coincide in space, thus avoiding the image plane interference problem caused by the non-coincidence of beams in space.

[0083] (6) High stability. This interferometric beam splitting technique is based on common optical path technology, and the common optical path interferometer has high stability.

[0084] The interferometer of the traditional Fourier Raman interference spectrometer adopts the non-common optical path technology, is easily disturbed by external thermodynamic changes, causes the change of the optical path difference, and further causes the movement of the interference fringes and the instability of the phase, thereby a larger instrument error is brought, and the high-precision measurement is inaccurate.

[0085] External thermodynamic changes act on two arms of the interferometer at the same time, so the optical path difference generated can be offset, the interference fringes formed are more stable, and the interferometer and the instrument are high in stability.

[0086] (7) Simple structure, easy to miniaturize. The Raman spectrum imaging device for gas detection provided in the application can be composed of only a beam splitter, a plane mirror and a concave mirror, the compensating plate in the traditional Raman interferometer is removed, the overall optical path design is reasonable, the whole structure is very compact, and the device is still convenient for miniaturization without loss of light flux, and is easy to be carried on various platforms.

[0087] (8) Suitable for high-speed measurement. Since the parallel plane mirror for generating the optical path difference adopts the 360° continuous rotation

[0088] mode, the acceleration and deceleration processes in the traditional linear or swinging process are avoided in the measurement process, the time utilization rate is improved, and therefore the measurement frequency is improved. Meanwhile, the parallel plane mirror for generating the optical path difference can generate more than 8 zero-crossing points in a 360° period, that is, more than 8 interference patterns and spectrum patterns can be generated in one rotation of the parallel plane mirror, so that the ultra-high-speed spectrum measurement is possible. The realization of this function not only improves the environmental interference resistance of the interferometer, but also enables the interferometer to be further applied to the high-speed spectrum measurement field, such as flying targets, flames or chemical reactions.

[0089] (9) High energy utilization rate and high system sensitivity. The interferometer in the application adopts an asymmetric design, so that all the two-way interference light output by the interferometer can be utilized, the condition that only one-way interference output is utilized in the traditional spectrum / imaging instrument is avoided, the utilization rate is increased to close to 100%, the transmittance of the whole system is greatly increased, and therefore the sensitivity of the system is improved.

[0090] It is obvious for those skilled in the art that the application is not limited to the details of the above exemplary embodiments, and the application can be implemented in other specific forms without departing from the spirit or essential characteristics of the application. Therefore, the embodiments should be regarded as exemplary and non-limiting, the scope of the application is defined by the appended claims rather than the above description, and all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the application.

[0091] The above examples are only used to illustrate the technical solutions of the present application but not limit the present application. Although the present application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalent replaced without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A Raman spectroscopic imaging device for gas detection, characterized in that Comprise; A common-path interferometer, wherein a moving mirror is arranged for generating a time-varying optical path difference; The common-path interferometer comprises a beam splitter for transmitting and reflecting beams; A first mirror group and a second mirror group for reflecting and changing the optical path of the beams; the first mirror group comprises a first concave mirror and a first mirror arranged oppositely, and the second mirror group comprises a second concave mirror and a second mirror arranged oppositely; An optical path adjustment assembly arranged between the first mirror group and the second mirror group, for adjusting the optical path based on time.

2. The Raman spectroscopic imaging device for gas detection according to claim 1, characterized in that, The optical path adjustment assembly comprises a third mirror group, a fourth mirror group and a plane mirror, the third mirror group comprises a pair of first mirror surface and second mirror surface arranged parallel to each other, and the fourth mirror group comprises a pair of third mirror surface and fourth mirror surface arranged parallel to each other: The beam enters the common-path interferometer and is divided into a first transmitted beam and a first reflected beam after the beam splitter; the first transmitted beam is reflected by the first mirror group, the third mirror group, the plane mirror and the second mirror group in turn and returns to the beam splitter, and is divided into a second transmitted beam and a second reflected beam; the first reflected beam is reflected by the second mirror group, the fourth mirror group, the plane mirror and the first mirror group in turn and returns to the beam splitter, and is divided into a third transmitted beam and a third reflected beam; the second transmitted beam and the third reflected beam are emitted in the same direction, and the third transmitted beam and the second reflected beam are emitted in the same direction.

3. The Raman spectroscopic imaging device for gas detection according to claim 2, wherein, The optical path adjustment assembly is further provided with a motor, and the motor drives the third mirror group to move.

4. The Raman spectroscopic imaging device for gas detection according to claim 3, wherein, The third mirror group moves in the form of rotation, swing or linear movement.

5. The Raman spectroscopic imaging device for gas detection according to claim 1, wherein, It also comprises a pre-assembly arranged at the entrance of the common-path interferometer, which comprises a laser and a parabolic mirror; the laser is arranged towards the focal point of the parabolic mirror, for emitting laser to the gas to be measured and exciting scattered light; the parabolic mirror is used for converging the scattered light to the same direction and shooting towards the common-path interferometer.

6. The Raman spectroscopic imaging device for gas detection according to claim 5, wherein, The pre-assembly further comprises a filter, which is arranged between the parabolic mirror and the common-path interferometer, for selecting light of a specific waveband.

7. The Raman spectroscopic imaging device for gas detection of claim 1, wherein, It also comprises a converging module, a detection module and a processing module; the converging module is used for converging the light beams emitted from the common-path interferometer and forming interference imaging to the detection module; the detection module collects the interference fringe signals and converts them into electrical signals, which are sent to the processing module; The processing module restores the spectral information according to the electrical signals.

8. A Raman spectroscopic imaging method for gas detection, characterized in that The Raman spectrum imaging device for gas detection is realized by arranging the optical path adjustment assembly for changing the optical path based on time in the common-path interferometer, so that the Raman spectrum imaging device for gas detection works in a time-modulated mode.

9. The Raman spectroscopic imaging method for gas detection according to claim 8, wherein, Comprise the following steps: S10: the pre-assembly emits laser to the gas to be measured, excites light beams and enters the common-path interferometer; S20: the light beam is split into a first transmitted light beam and a first reflected light beam after passing through the beam splitter, the first transmitted light beam is reflected by a first mirror group, a third mirror group, a plane mirror, and a second mirror group in sequence and then returns to the beam splitter, and is split into a second transmitted light beam and a second reflected light beam; the first reflected light beam passes through the second mirror group, a fourth mirror group, the plane mirror, and the first mirror group in sequence and then returns to the beam splitter, and is split into a third transmitted light beam and a third reflected light beam; the second transmitted light beam and the third reflected light beam exit in the same direction, and the third transmitted light beam and the second reflected light beam exit in the same direction; S30: the converging module forms interference of the light beams emitted from the common-path interferometer and images on the detection module; S40: the detection module converts the interference fringes into an electrical signal and sends the electrical signal to the processing module; S50: the processing module restores the electrical signal to a spectrum signal.

10. The Raman spectroscopic imaging method for gas detection according to claim 9, wherein, The step S50 further includes: S51: the processing module restores the electrical signal to a spectrum signal based on a Fourier transform algorithm.

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