CN107727638B - Laser Raman spectrum gas analyzer with resonant cavity enhancement - Google Patents
Laser Raman spectrum gas analyzer with resonant cavity enhancement Download PDFInfo
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- CN107727638B CN107727638B CN201711067255.XA CN201711067255A CN107727638B CN 107727638 B CN107727638 B CN 107727638B CN 201711067255 A CN201711067255 A CN 201711067255A CN 107727638 B CN107727638 B CN 107727638B
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/65—Raman scattering
- G01N21/658—Raman scattering enhancement Raman, e.g. surface plasmons
Abstract
The invention provides a laser Raman spectrum gas analyzer with resonant cavity enhancement, which changes the angle of a tube head by utilizing thermal expansion by adjusting the temperature difference of the tube wall, so that a resonant cavity reflector aligns to a laser beam to achieve the laser enhancement in a cavity, and changes the temperature and the length of the tube by adjusting the integral temperature of a heating film on the tube wall to form standing waves in the resonant cavity to achieve the effect of the laser enhancement in the cavity; the reflector plate is integrated in the hollow reflector tube, the resonant cavity is subjected to mode locking operation through the conductive film, and compared with the external reflector plate and a structure for performing mode locking through piezoelectric ceramics in the prior art, the novel point can realize a more compact structure and is integrated and convenient to carry; the inserted electro-optical crystal is used for changing the refractive index and influencing the optical path of light to carry out phase modulation on the light, so that the purpose of mode locking is achieved, and resonance is enhanced.
Description
Technical Field
The invention relates to the technical field of gas chemical component analysis and detection, in particular to a laser Raman spectrum gas analyzer with a resonant cavity for enhancement.
Background
Laser raman spectroscopy gas composition analysis is a technique that has been developed in recent years. The technology has the characteristics of high detection speed, less sampling, capability of analyzing various components simultaneously, small volume, simple maintenance, long service time and the like, and is very suitable for on-line analysis and measurement of the gas component content in the industrial process. The laser Raman spectrum gas analysis technology can be applied to the fields of gas logging in petroleum engineering, natural gas component detection and heat value analysis, heat treatment atmosphere control, coal-fired control in power plants, coal gas online analysis in iron-making, steel-making and coking processes of steel plants, gas monitoring in oil refining processes, gas detection control in fermentation processes, coal chemical industry, fertilizer production, methanol and ethanol production, refinement and the like.
The resonant cavity is used as an important component in a laser Raman spectrum gas analyzer, and when the resonant cavity is subjected to resonant adjustment at present, the piezoelectric ceramic generates micro displacement under driving voltage, so that the distance between reflecting mirrors at two ends of the resonant cavity is adjusted, the resonant cavity locks a longitudinal mode of a laser beam, and the energy of the laser beam in the cavity is enhanced. However, the piezoelectric ceramic is used for resonance adjustment, the piezoelectric ceramic needs to be installed on the resonant cavity, the installation and the debugging are complex, the size of a product is large, and the cost is high. The laser resonant cavity reflector collimation degree requires highly, and under the influence of temperature and atmospheric pressure, the bending of different degree can appear at the both ends of resonant cavity, and then brings the angular migration of reflector for emergent laser intensity weakens, influences the effect of detection analysis.
Carry out resonance through piezoceramics and adjust, the design size of sample room is great, adopts external speculum simultaneously, and the design that also can bring the sample room size is inconvenient, and is inconvenient to carry, has restricted the application scene of product.
Disclosure of Invention
The invention provides a laser Raman spectrum gas analyzer with a resonant cavity enhancement, which adjusts the temperature and the cavity length of a resonant cavity tube through a heating film or an inserted electro-optical crystal, and adjusts the angle of a tube head of the resonant cavity through temperature difference to achieve the effect of enhancing resonance.
In order to solve the technical problems, the invention adopts the following technical scheme:
the utility model provides a take laser raman spectroscopy gas analysis appearance of resonant cavity reinforcing, includes resonant cavity, scattered light collection device and the spectrum appearance that the light path connects gradually, the resonant cavity embeds there is hollow reflection tube, and the laser instrument end of this resonant cavity is provided with the incident reflector, and the detector end of resonant cavity is provided with the outgoing reflector, the resonant cavity outer wall coats and is stamped the film that generates heat, and the film that should generate heat is connected with external temperature controller electricity.
The utility model provides a take laser raman spectroscopy gas analysis appearance of resonant cavity reinforcing, includes resonant cavity, scattered light collection device and the spectrum appearance that the light path connects gradually, the resonant cavity is hollow reflection tube, and this hollow reflection tube is provided with the incident reflector for the one end of incident laser, and hollow reflection tube is provided with the outgoing reflector for the other end of outgoing laser, the hollow reflection tube outer wall coats and is stamped the film that generates heat, and the film that should generate heat is connected with external temperature controller electricity.
The utility model provides a take laser raman spectroscopy gas analysis appearance of resonant cavity reinforcing, includes resonant cavity, scattered light collection device and the spectrum appearance that the light path connects gradually, the resonant cavity embeds there is hollow reflection tube, and the laser instrument end of this resonant cavity is provided with the incident reflector, and the detector end of resonant cavity is provided with the outgoing reflector, the laser beam light path between incident reflector and the outgoing reflector is provided with the electro-optic crystal, and this electro-optic crystal carries out the refracting index through external voltage driver and adjusts, the outgoing reflector is connected with external detector light path, voltage driver and this detector signal connection.
Furthermore, scattered light collection device includes reflective filter, and this reflective filter includes incident lens, filtering component and the exit lens that light path connects in proper order, filtering component is including forming a plurality of filter plates that light path reflection connects in proper order.
Preferably, the filter assembly comprises one or more nitrogen filters, and one or more oxygen filters.
Preferably, the filter assembly further comprises one or more water filter plates.
Further, the scattered light collection device comprises an incident lens, a light filtering component, an emergent lens and a signal light receiving end which are connected in sequence through light paths, wherein the light filtering component comprises one or more dichroic mirrors and a plurality of band-stop filters arranged on the transmission side and the reflection side of the dichroic mirrors, the signal light receiving end is arranged on the transmission light path of each band-stop filter, and the scattered light is divided into signal light of a plurality of spectral bands through the transmission light and the reflection light after passing through the dichroic mirrors.
Furthermore, the spectrometer comprises an incident lens, a grating, a camera lens and a sensor array which are connected in sequence through a light path, wherein a Mask filter is arranged on a receiving surface of the sensor array, and the Mask filter can absorb or shield one or more strong light spectral lines of nitrogen, oxygen, carbon dioxide and water.
Furthermore, the spectrometer comprises an incident lens, a grating, a camera lens and a sensor array which are connected in sequence through a light path, and is characterized in that a Mask filter and an imaging lens are arranged on the light path between the camera lens and the sensor array, and the Mask filter can absorb one or more strong light spectral lines of nitrogen, oxygen, carbon dioxide and water.
Further, the heating film comprises two pairs of first temperature module groups circumferentially arranged on the outer wall of the laser end of the resonant cavity and two pairs of second temperature module groups circumferentially arranged on the outer wall of the detector end of the resonant cavity, wherein one pair of first temperature module groups is used for detecting and controlling the temperature difference between the two sides of the laser end in the horizontal direction, the other pair of first temperature module groups is used for detecting and controlling the temperature difference between the two sides of the laser end in the vertical direction, one pair of second temperature module groups is used for detecting and controlling the temperature difference between the two sides of the detector end in the horizontal direction, and the other pair of second temperature module groups is used for detecting and controlling the temperature difference between the two sides of the detector end in the vertical direction.
Preferably, the thickness of the heating film and the required heating power P have a relationship of L × ρ '× P/(U × w), where L is the total length of the film, ρ' is the resistivity of the conductive film, U is the heating voltage, and w is the width of the cross section of the conductive film.
Preferably, a stable mode locking region is formed in the resonant cavity, and the required heating power P has a relation of P ═ c × ρ × v × λ/(2 α × l × t), where v is the volume of the resonant cavity, ρ is the density of the resonant cavity material, α is the linear thermal expansion coefficient of the resonant cavity material, c is the specific heat capacity, l is the length of the resonant cavity, and t is the mode locking stabilization time.
Preferably, the lens inclination angle θ of the incident mirror and the exit mirror has
Wherein α is the linear thermal expansion coefficient of the resonant cavity material, L is the length of a single temperature module, h is the lens mounting diameter, and T' are the temperatures of the outer walls of the resonant cavity at both sides in the horizontal direction or both sides in the vertical direction, respectively.
According to the technical scheme, the temperature difference of the pipe wall is adjusted, the angle of the pipe head is changed by thermal expansion, the resonant cavity reflector is aligned with the laser beam to achieve the laser enhancement in the cavity, and the temperature and the length of the pipe are changed by adjusting the overall temperature of the heating film on the pipe wall to form standing waves in the resonant cavity to achieve the effect of the laser enhancement in the cavity; the reflector plate is integrated in the hollow reflector tube, and the resonant cavity is subjected to mode locking operation through the conductive film, so that compared with an external reflector plate and a structure for performing mode locking through piezoelectric ceramics in the prior art, the novel point can realize a more compact structure, and the reflector plate is integrated, convenient to carry, more standardized and high in production efficiency; the inserted electro-optical crystal is used for changing the refractive index and influencing the optical path of light to carry out phase modulation on the light, so that the purpose of mode locking is achieved, and resonance is enhanced.
Drawings
FIG. 1 is an axial cross-sectional view of a resonant cavity in accordance with an embodiment of the present invention;
FIG. 2 is an axial cross-sectional view of a resonant cavity according to an embodiment of the present invention;
FIG. 3 is an axial cross-sectional view of a triple cavity resonator in accordance with an embodiment of the present invention;
FIG. 4 is an end view of a resonator laser end according to one embodiment;
FIG. 5 is an end view of a probe end of a resonant cavity according to one embodiment;
FIG. 6 is a schematic diagram illustrating an angular offset of a mirror according to an embodiment;
FIG. 7 is a schematic structural diagram of a preferred embodiment of the scattered light collection apparatus of the present invention;
FIG. 8 is a schematic structural diagram of another preferred embodiment of the scattered light collection apparatus according to the present invention;
FIG. 9 is a schematic diagram of an embodiment of a grating spectrometer;
FIG. 10 is a schematic diagram of another embodiment of a grating spectrometer;
FIG. 11 is a schematic view of a Mask filter;
FIG. 12 shows a preferred embodiment of the heat-generating film of the present invention.
Detailed Description
A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.
The laser Raman spectrum gas analyzer comprises a resonant cavity, a scattered light collecting device and a spectrometer which are connected in sequence through optical paths, wherein in order to realize the function of enhancing the resonant cavity, the resonant cavity is improved, and the structure of the laser Raman spectrum gas analyzer is explained by adopting three embodiments.
Example one
In the embodiment, the temperature difference of the tube wall is adjusted, the angle of the tube head is changed by thermal expansion, the resonant cavity reflector is aligned with a laser beam to achieve the laser enhancement in the cavity, and the temperature and the length of the tube are changed by adjusting the overall temperature of a heating film on the tube wall to form standing waves in the resonant cavity to achieve the effect of the laser enhancement in the cavity.
As shown in fig. 1, the resonant cavity 10 includes a resonant cavity 20 and a hollow reflection tube 30 disposed in the resonant cavity, an incident mirror 21 is disposed at a laser end of the resonant cavity, an exit mirror 22 is disposed at a detector end of the resonant cavity, and a temperature controller 40 is disposed outside the resonant cavity.
The outer wall of the resonant cavity 20 is covered with a heating film 50, the heating film is electrically connected with an external temperature controller 40, the heating film is a power-on heating material, and can be realized by adopting but not limited to nickel, complex, graphene, nickel complex alloy and constantan and adopting a vacuum coating, etching or printing mode.
The heating film 50 has a large distribution adjustable space and a diversity of distribution, as shown in fig. 12, in this embodiment, the heating film is in an S-shaped structure connected in sequence after being unfolded, and the two ends of the heating film are respectively provided with an electrode 51 for connecting a temperature controller, so that the structural design is favorable for the uniformity of heating. The heating film can also adopt other various structural forms as long as the heating film is basically uniformly and symmetrically distributed.
The thickness of the heat generating film 50 is determined by the required heat generating power, and the required heat generating power is expressed by the formula of R ═ L ×/(w) >, and P ═ U/R, and the required film thickness is obtained by the above two formulas: l ρ '. P/(U × w), where L is the total length of the film, ρ' is the resistivity of the conductive film, U is the heating voltage, and w is the width of the cross section of the conductive film.
The upper surface and the lower surface of the heating film 50 are both provided with insulating films, the insulating films can be organic materials or inorganic materials, the insulating film materials include but are not limited to silicon oxide, aluminum oxide, polyimide and polytetrafluoroethylene, the breakdown voltage of the insulating film materials is more than 12V, and the thickness of the insulating film materials is more than 100 nm. Adopts a film forming means of vacuum coating or spraying.
The resonant cavity has the advantages of high temperature controllability, wide temperature range (-20 ℃ -200 ℃), capability of realizing the testing of high-boiling-point VOC gas, capability of monitoring gas with higher water content, such as flue gas and the like, no need of additionally installing a filter device, and wider application range.
In the embodiment, the integral temperature of the heating film on the tube wall is adjusted, so that the tube temperature and the cavity length of the resonant cavity are changed, standing waves are formed in the resonant cavity, a mode locking effect is formed, and the effect of enhancing laser in the cavity is achieved. In order to form a stable mode locking region, the length variation Δ l of the cavity needs to be slightly larger than half of the laser wavelength, i.e., Δ l ═ λ/2, the laser wavelength is related to other parameters of the cavity, Δ l ═ λ/2 ═ α ═ Δ T, and Δ T ═ λ/(2 α ×, is obtained, so that stable mode locking is maintained, and the required heating power P has the relationship of P ═ ρ ═ v ═ Δ T/T ═ c ρ ═ ρ v × (× /) 2 α ×, T, where v is the cavity volume, ρ is the cavity material density, α is the cavity material linear thermal expansion coefficient, c is the cavity volume, l is the cavity length, and T is the mode locking stabilization time.
The resonant cavity materials include but are not limited to quartz, aluminum, copper, invar, different requirements for mode locking time, and different resonant cavity materials, different power requirements can be obtained. The invention has the advantages of integrated mode locking design and mechanical stability, and can realize monitoring in a complex environment.
This embodiment can also satisfy the requirement of auto-collimation through the angle of the pipe head of pipe temperature regulation resonant cavity both sides, and this needs cut apart heating film 50, controls the temperature difference of resonant cavity both ends outer wall horizontal direction both sides or vertical direction both sides respectively, controls the angle of pipe head according to expend with heat and contract with cold's principle. In this embodiment, the heating film is uniformly divided into 8 heating strips, and 4 heating strips are respectively arranged at both ends of the heating film, which are symmetrical to each other.
As shown in fig. 4 and 5, two pairs of first temperature modules are formed by four heat bars circumferentially arranged on the outer wall 23 of the laser end of the resonant cavity, and two pairs of second temperature modules are formed by four heat bars circumferentially arranged on the outer wall 24 of the detector end of the resonant cavity, wherein one pair of first temperature module groups 521 is used for detecting and controlling the temperature difference on both sides of the laser end in the horizontal direction, the other pair of first temperature module groups 522 is used for detecting and controlling the temperature difference on both sides of the laser end in the vertical direction, one pair of second temperature module groups 531 is used for detecting and controlling the temperature difference on both sides of the detector end in the horizontal direction, and the other pair of second temperature module groups 532 is used for detecting and controlling the temperature difference on both sides of the detector end in the vertical direction.
The temperature modules are combined together, and the cavity length of the resonant cavity can be controlled through the whole temperature change.
Each pair of temperature module groups can control the angle of the elbow, and particularly, the angle can be controlled by controlling the tiny temperature difference between two oppositely arranged heating strips in the temperature module groups.
As shown in fig. 6, when the incident reflector 21 and the exit reflector 22 are dislocated due to the influence of the ambient temperature and the air pressure on the resonant cavity, the lens dislocation at one end is Δ d α × L (T-T '), where α is the linear thermal expansion coefficient of the resonant cavity material, L is the length of a single temperature module, and T ' are the temperatures of the two sides of the outer wall of the resonant cavity in the horizontal direction or the two sides of the outer wall in the vertical direction, respectively, so the tilt angle of the lens has the relationship of sin θ Δ d/h α × L (T-T ')/h, where h is the mounting diameter of the lens, and the tilt angle of the lens is obtained
The control of the lens angle can be realized by controlling the micro temperature difference of the heating module.
Fig. 1 only shows the electric connection mode of the temperature controller when the heating film is used for overall temperature control, each pair of temperature module groups in the heating film for controlling the angle of the elbow are electrically connected with the temperature controller 40 independently, the temperature controller controls each pair of temperature module groups independently, and the temperature controller dynamically scans the small temperature difference through the temperature to find the maximum signal intensity so as to detect and control the angle of the pipe head.
Example two
Use hollow reflector tube to replace all functions of resonant cavity in this embodiment, with the reflector plate integration in hollow reflector tube to carry out the mode locking operation through conductive film to the resonant cavity, for external reflector plate and the structure that carries out the mode locking through piezoceramics among the prior art, this innovation point can realize more small and exquisite structure, integrated form portable, and more standardized, production efficiency is high.
As shown in fig. 2, a temperature controller 30 is disposed outside the hollow reflection tube, a heating film 50 is covered on the outer wall of the hollow reflection tube 20, the heating film is electrically connected to the external temperature controller 30, the heating film is a power-on heating material, and can be realized by, but not limited to, nickel, copper, graphene, nickel-copper alloy, constantan, and by vacuum coating, etching, or printing.
By adjusting the overall temperature of the heating film on the tube wall, the tube temperature and the cavity length are changed, standing waves are formed in the hollow reflecting tube, the effect of enhancing laser in the cavity is achieved, and mode locking operation is carried out on the resonant cavity. In this example, the heat generating film was the same as that of example 1.
An incident reflector 21 is arranged at one end of the hollow reflection tube 20 opposite to the incident laser, an emergent reflector 22 is arranged at the other end of the hollow reflection tube opposite to the emergent laser, the laser beam enters the hollow reflection tube from the incident reflector, propagates in the hollow reflection tube and reacts with gas molecules to be analyzed in the hollow reflection tube to generate scattered light, and the scattered light is reflected for multiple times by the tube wall in the hollow reflection tube and then is emitted from one end or two ends of the hollow reflection tube. The hollow reflection tube is provided with an air inlet 23 and can also be provided with another air outlet.
The embodiment embeds incident mirror 21 and emergent mirror 22 into the two ends of the hollow reflection tube, greatly reduces the volume of the sample chamber, is convenient to carry, and can be used in more complex environment.
EXAMPLE III
As shown in fig. 3, a hollow reflection tube 30 is disposed in the resonator, an incident mirror 21 is disposed at a laser end of the resonator, and an exit mirror 22 is disposed at a detector end of the optical resonator.
In this embodiment, the electro-optical crystal 40 is inserted into the resonant cavity, and an external voltage driver 50 is used in combination with a feedback signal sensed by the detector 60 to adjust the refractive index of the electro-optical crystal, so as to affect the optical path of light to perform phase modulation on the light, thereby achieving the purpose of mode locking.
Wherein, the detector 60 is arranged at the detector end of the optical resonant cavity, is optically connected with the emergent reflector 22, and can use a photodiode as the detector for detecting the intensity of the laser emergent end as the feedback signal for adjusting the refractive index of the electro-optical crystal.
The electro-optic crystal 40 is disposed between the entrance mirror 21 and the exit mirror 22 with its horizontal centerline in the laser beam path within the optical resonator to reduce mechanical errors. The electro-optical crystal is connected with the inner wall of the optical resonant cavity through the supporting part, and the electro-optical crystal is arranged at both the detector end and the laser end of the optical resonant cavity.
The electro-optical crystal 40 is subjected to refractive index adjustment through an external voltage driver 50, the voltage driver is in signal connection with the detector 60, the detector is located on a laser emergent light path, when the detector detects that the signal intensity requirement is a maximum signal, peak value control is dynamically searched through scanning voltage, and the specific principle is as follows:
the refractive index n ═ n of the electro-optic crystal after the electric field is applied0+ m U/L, where L is the length of the electro-optic crystal, U is the voltage applied along the Z-axis of the electro-optic crystal, and n0M is a constant, which is related to the electro-optic coefficient of the electro-optic crystal.
The invention provides two specific embodiments for filtering and collecting scattered light signals emitted by a resonant cavity through a scattered light collecting device.
In one embodiment, as shown in fig. 7, the scattered light collection device comprises a modified reflective filter comprising an entrance lens 10, a filter assembly 20 and an exit lens 30 optically connected in sequence, the filter assembly comprising one or more nitrogen filters, one or more oxygen filters and one or more water filters optically connected in sequence. The quantity of nitrogen gas filter, oxygen filter and water filter plate designs according to the content of the gas kind that awaits measuring in the mist, and the content is lower, and the number of times that need filter nitrogen gas, oxygen and water is just more, and the quantity of the filter that corresponds is just more.
In this embodiment, the content of oxygen in the air is 21%, and the content of nitrogen is 78%, therefore needs two nitrogen gas filters, filtering subassembly 20 includes first nitrogen gas filter 21, second nitrogen gas filter 22, first oxygen filter 23 and first water filter 24, and the light source enters from penetrating lens 10, passes through and penetrates lens 30 after first nitrogen gas filter, second nitrogen gas filter, first oxygen filter and the first water filter reflect in proper order. Wherein the first nitrogen filter 21 and the first oxygen filter 23 are located on the same side, and the second nitrogen filter 22 and the first water filter 24 are located on the other side in parallel.
Through two nitrogen filters, an oxygen filter and a water filter, the strong spectral line is effectively eliminated, the noise can be reduced to a great extent, and the signal-to-noise ratio is improved.
A notch filter 40 and a band-pass filter 50 can be arranged between the incident lens 10 and the first nitrogen filter 21, the optical signal passes through the two filters after entering the sample chamber, and edge stray light, Rayleigh scattered light and laser in the signal are filtered, so that the influence of strong light on the spectrum is reduced, and the signal-to-noise ratio and the detection limit of measurement are improved.
Compared with the existing collection system, the present embodiment not only integrates the advantages of the front collection chamber and the filter, but also improves the collection efficiency of Raman light, reduces the signal light loss by 5%, and reduces the volume of the collection system.
In another embodiment shown in fig. 8, the scattered light collecting device includes an incident lens 10, a filter assembly 20, an exit lens 30 and a signal light receiving end 40, which are connected in sequence by an optical path, and the scattered light from the scattering exit of the resonant cavity enters from the incident lens, is filtered by the filter assembly for strong light spectrum, and then exits from the exit lens to enter the signal light receiving end, which uses an array detector.
The invention has the innovation points that the light filtering component adopts one or more dichroic mirrors and a plurality of band elimination filters arranged on the transmission side and the reflection side of the dichroic mirrors, the signal light receiving end is arranged on the transmission light path of each band elimination filter, the scattered light passes through the transmission light and the reflected light of the dichroic mirrors and is divided into signal light of a plurality of spectral sections through the plurality of band elimination filters, the signal light of each spectral section enters the corresponding signal light receiving end, the signal light receiving end is connected with the input end of a spectrometer through an optical fiber bundle to segment the spectrum, the resolution of spectral analysis is favorably improved, and the effect of extending the spectral response range can be achieved by using a plurality of small-size light array detector groups only having narrow spectral response, so that a single wide-spectral response large-size light array detector with high cost or difficult acquisition is replaced.
As shown in fig. 8, the optical filtering component 20 includes a first dichroic mirror 21, a second dichroic mirror 22, a first band-stop filter 23, a second band-stop filter 24, and a third band-stop filter 25, where the first dichroic mirror and the second dichroic mirror are located on the same optical path straight line, the first band-stop filter is disposed on the reflective side of the first dichroic mirror, the second band-stop filter is disposed on the reflective side of the second dichroic mirror, the third band-stop filter is disposed on the transmissive side of the second dichroic mirror, and the refraction directions of the first dichroic mirror and the second dichroic mirror may be opposite or the same. And signal light receiving ends 40 are arranged on the transmission light paths of the first band elimination filter 23, the second band elimination filter 24 and the third band elimination filter 25.
When the method is applied to gas Raman detection, the wave number range of 200-4200 can be divided into three sections. The signal light with the wave number of 200-1545 is screened out by the first dichroic mirror and the first band-resistance filter; screening out signal light with the wave number of 1605-2335 through a second section of dichroic lens and a second band elimination filter; and finally, screening out signal light with the wave number of 2380-4200 by a third band elimination filter. The spectrometer for receiving the plurality of signal lights with different wave number ranges can be a plurality of independent spectrometers or an integrated spectrometer.
The invention provides two specific embodiments of a spectrometer, and the two specific embodiments of the spectrometer comprise that signal light after being filtered and collected by a scattered light collecting device finally enters the spectrometer for signal analysis.
In one embodiment shown in fig. 9, the grating spectrometer includes an incident lens 10, a grating 20, a camera lens 30 and a sensor array 40, which are connected in sequence, and the incident lens may be an achromatic lens. A Mask filter 50 is provided on the receiving surface of the sensor array 40, and is capable of absorbing one or more strong light lines of nitrogen, oxygen, carbon dioxide and water. Strong raman signals can be suppressed using a Mask filter, which may be a glass substrate, that is scribed to block the peak of the strong light line, as shown in fig. 11. Hollow structures formed by metal bottom layers can also be adopted.
In another embodiment shown in fig. 10, this embodiment is different from the previous embodiment in that a Mask filter 50 and an imaging lens 60 are disposed on the optical path between the camera lens 30 and the sensor array 40, and the Mask filter is separated from the sensor array, so that compared to the grating spectrometer of embodiment 1, the scattered light of the strong light lines on the Mask filter is imaged on the non-imaging area and the edge zone of the sensor through the lens, and the influence of the stray light on the spectrum is further reduced.
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements made to the technical solution of the present invention by those skilled in the art without departing from the spirit of the present invention are intended to fall within the scope of the present invention defined by the claims.
Claims (21)
1. The utility model provides a take laser raman spectroscopy gas analysis appearance of resonant cavity reinforcing, includes resonant cavity, scattered light collection device and the spectrum appearance that the light path connects in proper order, the resonant cavity embeds there is hollow reflection tube, and the laser instrument end of this resonant cavity is provided with the incident reflector, and the detector end of resonant cavity is provided with the outgoing reflector, its characterized in that, the resonant cavity outer wall coats and is stamped the film that generates heat, and the film that should generate heat is connected with external temperature controller electricity, cuts apart the film that should generate heat, controls the temperature difference of resonant cavity both ends outer wall horizontal direction both sides or vertical direction both sides respectively, and the film that should generate heat can adjust the angle of resonant cavity both sides.
2. The laser raman spectroscopy gas analyzer of claim 1, wherein the heating film comprises two pairs of first temperature module groups circumferentially disposed on an outer wall of a laser end of the resonator, one pair of the first temperature module groups for detecting and controlling a temperature difference across a horizontal direction of the laser end, and another pair of the first temperature module groups for detecting and controlling a temperature difference across a vertical direction of the laser end, and two pairs of the second temperature module groups circumferentially disposed on an outer wall of a detector end of the resonator, one pair of the second temperature module groups for detecting and controlling a temperature difference across a horizontal direction of the detector end, and the other pair of the second temperature module groups for detecting and controlling a temperature difference across a vertical direction of the detector end.
3. The laser raman spectroscopy gas analyzer of claim 2, wherein the first temperature module set and the second temperature module set include heat bars disposed at two sides of the outer wall of the resonator in a horizontal direction or two sides of the outer wall of the resonator in a vertical direction.
4. The laser Raman spectrum gas analyzer of claim 3, wherein the heating strips are S-shaped structures connected in sequence, and electrodes for connecting a temperature controller are respectively arranged at two ends of the heating strips.
5. The laser raman spectroscopy gas analyzer of any one of claims 2 or 3, wherein the lens tilt angles θ of the entrance mirror and the exit mirror have
Wherein α is the linear thermal expansion coefficient of the resonant cavity material, L is the length of a single temperature module, h is the installation diameter of the lens, and T' are respectively the two sides of the outer wall of the resonant cavity in the horizontal direction or the two sides of the outer wall of the resonant cavity in the vertical directionThe temperature of the wall.
6. The utility model provides a take laser raman spectroscopy gas analysis appearance of resonant cavity reinforcing, includes resonant cavity, scattered light collection device and the spectrum appearance that the light path connects in proper order, its characterized in that, the resonant cavity is hollow reflection pipe, and this hollow reflection pipe is provided with the incident reflector for the one end of incident laser, and hollow reflection pipe is provided with the outgoing reflector for the other end of outgoing laser, the hollow reflection pipe outer wall coats and is stamped the film that generates heat, and the film that should generate heat is connected with external temperature controller electricity, cuts apart the film that should generate heat, controls the temperature difference of resonant cavity both ends outer wall horizontal direction both sides or vertical direction both sides respectively, and the film that should generate heat can be through the angle of managing temperature regulation resonant cavity both.
7. The laser raman spectroscopy gas analyzer of claim 6, wherein the hollow reflection tube is provided with an air inlet.
8. The laser raman spectroscopy gas analyzer of claim 1 or 6, wherein the scattered light collecting means comprises a reflective filter including an entrance lens, a filter assembly and an exit lens optically connected in sequence, the filter assembly including a plurality of filters forming an optical path reflective connection in sequence.
9. The laser raman spectroscopy gas analyzer of claim 8, wherein the filter assembly includes one or more nitrogen filters and one or more oxygen filters.
10. The laser raman spectroscopy gas analyzer of claim 9, wherein the filter assembly further comprises one or more water filter plates.
11. The laser raman spectroscopy gas analyzer of any one of claims 9 to 10, wherein a notch filter and a band pass filter are disposed between the incident lens and the nitrogen filter.
12. The laser raman spectroscopy gas analyzer according to claim 1 or 6, wherein the scattered light collecting means includes an incident lens, a filter assembly, an exit lens, and a signal light receiving end, which are optically connected in sequence, the filter assembly includes one or more dichroic mirrors, and a plurality of band-stop filters provided on transmission sides and reflection sides of the dichroic mirrors, the signal light receiving end is disposed on a transmission optical path of each of the band-stop filters, and transmitted light and reflected light of scattered light passing through the dichroic mirrors are divided into signal light of a plurality of spectral bands by the plurality of band-stop filters.
13. The laser raman spectroscopy gas analyzer of claim 12, wherein the dichroic mirror comprises a first dichroic mirror and a second dichroic mirror positioned on a same optical path straight line, a reflective side of the first dichroic mirror is provided with a first band stop filter, a reflective side of the second dichroic mirror is provided with a second band stop filter, and a transmissive side of the second dichroic mirror is provided with a third band stop filter.
14. The laser raman spectroscopy gas analyzer of claim 13, wherein the first-stage dichroic mirror refracts in an opposite direction to the second-stage dichroic mirror.
15. The laser raman spectroscopy gas analyzer of any one of claims 13 or 14, wherein the signal light receiving end employs an array detector.
16. The laser raman spectroscopy gas analyzer according to claim 1 or 6, wherein the spectrometer includes an incident lens, a grating, a camera lens and a sensor array which are connected in sequence by an optical path, a receiving surface of the sensor array is provided with a Mask filter which can absorb or shield one or more strong light lines of nitrogen, oxygen, carbon dioxide and water.
17. The laser raman spectroscopy gas analyzer of claim 16, wherein the entrance lens is an achromatic lens.
18. The laser raman spectroscopy gas analyzer according to claim 1 or 6, wherein the spectrometer comprises an incident lens, a grating, a camera lens and a sensor array which are connected in sequence by an optical path, wherein a Mask filter and an imaging lens are arranged on the optical path between the camera lens and the sensor array, and the Mask filter can absorb or shield one or more strong light lines of nitrogen, oxygen, carbon dioxide and water.
19. The laser raman spectroscopy gas analyzer according to any one of claims 1, 2, or 6, wherein both upper and lower surfaces of the heat generating film are provided with an insulating film.
20. The laser raman spectroscopy gas analyzer of any one of claims 1, 2, or 6, wherein the thickness of the heat generating film has a relationship with the required heating power P of L ρ '/U/w, where L is the total film length, ρ' is the conductive film resistivity, U is the heating voltage, and w is the width of the conductive film cross section.
21. A laser raman spectroscopy gas analyzer according to any one of claims 1, 2 or 6, wherein a stable mode-locked region is formed within the cavity, and the required heating power P has a relationship of P ═ c ρ ν λ/(2 α ρ Ι τ), where v is the cavity volume, ρ is the cavity material density, α is the cavity material linear thermal expansion coefficient, c is the specific heat capacity, l is the cavity length, t is the mode-locking stabilization time, and λ is the laser wavelength.
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| CN112986160B (en) * | 2021-01-16 | 2022-05-20 | 西安交通大学 | Multispectral high-speed imaging device for realizing scanning deflection based on DKDP crystal |
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