CN108318420A - A kind of light channel structure for high-precision gas refractometry - Google Patents
A kind of light channel structure for high-precision gas refractometry Download PDFInfo
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- CN108318420A CN108318420A CN201711404648.5A CN201711404648A CN108318420A CN 108318420 A CN108318420 A CN 108318420A CN 201711404648 A CN201711404648 A CN 201711404648A CN 108318420 A CN108318420 A CN 108318420A
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- G—PHYSICS
- 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
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
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- G—PHYSICS
- 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
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
- G01N21/45—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods
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Abstract
The invention belongs to gas refracting index field of measuring technique, and in particular to a kind of light channel structure for high-precision gas refractometry.Laser light source sends out the linearly polarized light of frequency stabilization, is divided into optical path and reference path by beam splitter；Reference path carries out frequency modulation(PFM) by frequency modulator, and modulating frequency is far below laser frequency, and reference path is divided into two-way through beam splitter：All the way with converging all the way after optical path beam splitting, be incident on the photoelectric detector PD of signal processing unit0In, reference when being handled as interference signal；Another way, which first passes through half-wave plate, makes the polarization direction of light be rotated by 90 °, and 4 multiple road is then divided by several beam splitters and speculum, the photoelectric detector PD for being incident on signal processing unit is converged with optical path1~PDnIn, n=4i, i are integer.The present invention eliminates influence of all kinds of errors to measurement result, realizes the high-acruracy survey of gas refracting index by the way that multichannel measurement light path is symmetrical and the method for multiple heterodyne.
Description
Technical field
The invention belongs to gas refracting index field of measuring technique, and in particular to one kind being used for high-precision gas refractometry
Light channel structure.
Background technology
Gas refracting index is the physical quantity paid special attention in all kinds of Optical System Designs, the accurate survey of gas refracting index
Amount is to carry out the basis of optical precision measurement.In the field that precision manufactureing etc. needs high-precision optical to measure, gas refracting index
High-acruracy survey be scene to high-precision optical measuring instrument carry out error compensation work effective way, be improve optics survey
One of the important means of measuring appratus measurement accuracy.
Currently, common gas refracting index measurement method can be divided into two classes：The indirect method of measurement and the direct method of measurement.It is wherein straight
Connect the measurement that mensuration is applicable to multiple gases refractive index, it mainly utilize electromagnetic wave characteristic directly to gas refracting index into
Row measures.Under normal conditions, realize that the refractometry of gas is most common using the transmission characteristic combination vacuum chamber of laser
One of direct measuring method.
However, presently, there are the light channel structure measured for gas refracting index, be commonly present that operating process is cumbersome, error suppression
The weaker disadvantage of effect processed brings inconvenience to the high-precision gas refracting index measurement of realization.
Patent of invention CN103558185A and CN104062266B use the light channel structure of single channel Michelson's interferometer,
In light channel structure, influence of the environment to reference path will be updated in final measurement result, and environmental suitability is poor, difficult
To realize that high-precision gas refracting index measures.
Two-way is used in patent of invention CN102221535A to turn back light channel structure, keeps two-way laser true by three respectively
The vacuum section of blank pipe and under test gas part calculate gas refracting index by comparing the phase difference of two-way light.The light channel structure
Mobile vacuum pipe device is needed when switching vacuum tube, inconvenience is brought to using.Meanwhile laser light source, environment and vacuum tube
The factors such as inclination can introduce the error of measurement result, become the bottleneck for realizing high-precision gas refractometry.
Invention content
Place in view of the deficiency of the prior art, it is a kind of for high-precision gas it is an object of the invention to propose
The light channel structure of refractometry improves the measurement accuracy of gas refracting index to reduce the error source of measuring system.
In order to achieve the above objectives, the technical solution used in the present invention is：
A kind of light channel structure for high-precision gas refractometry, laser light source send out the linear polarization of frequency stabilization
Light is divided into optical path and reference path by beam splitter；
The reference path carries out frequency modulation(PFM) by frequency modulator, and modulating frequency is far below laser frequency, reference light
Road is divided into two-way through beam splitter：All the way with converging all the way after optical path beam splitting, the photoelectricity for being incident on signal processing unit is visited
Survey device PD0In, reference when being handled as interference signal；Another way, which first passes through half-wave plate, makes the polarization direction of light be rotated by 90 °, so
It is divided into 4 multiple road by several beam splitters and speculum afterwards, the light for being incident on signal processing unit is converged with optical path
Electric explorer PD1~PDnIn, n=4i, i are integer；
The optical path carries out frequency modulation(PFM) by frequency modulator, and modulating frequency is far below laser frequency, and with ginseng
The modulating frequency of light path is examined there are frequency difference Δ f, optical path is divided into two-way through beam splitter：All the way with after reference path beam splitting
Converge all the way, be incident on the photoelectric detector PD of signal processing unit0In, reference when being handled as interference signal；It is another
Road is divided into 4 multiple road, the optical path quantity after beam splitting and reference path quantity phase by several beam splitters and speculum
Together, then optical path injects vacuum chamber by polarizing beam splitter mirror, after the speculum reflection in vacuum chamber, by polarizing beam splitter mirror
Reflection, converges with reference path, is ultimately incident upon the photoelectric detector PD of signal processing unit1~PDnIn, n=4i, i are whole
Number.
The frequency difference Δ f should enable interference signal by photoelectricity within the scope of the response frequency of photodetector
Detector responds.
4 tunnel of optical path being injected into vacuum chamber is one group, and the respective optical path between each group is with vacuum chamber
It is axisymmetricly distributed centered on axis, to reduce the error of vacuum chamber mirror deformation introducing.
The signal processing unit includes interference signal processing module, heterodyne signal processing module, phase processing module.
The interference signal processing module is by photodetector and processing circuit to reference path and optical path
Interference signal is handled, photoelectric detector PD0Directly measure the interference signal 0 of reference path and optical path, photodetection
Device PD1~PDnMeasure the roads 4i through the interference signal 1 between the reflected optical path of vacuum chamber and corresponding reference path~
4i；1~4i of interference signal is done difference frequency operation by the heterodyne signal processing module with the interference signal of reference 0 respectively, is rejected
Fall the error that laser light source unstability is brought, then resolves the relative phase values for obtaining each road optical path；The phase
Position processing module according to gas refracting index measuring principle, calculate the phase difference between each optical path, weed out due to environment,
Then the error that vacuum chamber introduces calculates and obtains gas refracting index value.
It is obtained by the present invention to have the beneficial effect that：
The present invention eliminates all kinds of errors to measuring by the way that multichannel measurement light path is symmetrical and the method for multiple heterodyne
As a result influence realizes the high-acruracy survey of gas refracting index.
Description of the drawings
Fig. 1 is a kind of light channel structure functional block diagram for high-precision gas refractometry；
Fig. 2 is the functional block diagram of signal processing unit；
Fig. 3 is a kind of light channel structure embodiment figure for high-precision gas refractometry.
Specific implementation mode
The present invention is described in detail with specific embodiment below in conjunction with the accompanying drawings.
As shown in Figure 1 and Figure 2, the light channel structure of the present invention for high-precision gas refractometry includes laser light
Source, optical path, reference path and signal processing unit；
The laser light source can send out the linearly polarized light of frequency stabilization, be divided into optical path and reference by beam splitter
Light path；The reference path carries out frequency modulation(PFM) by frequency modulation(PFM) device (such as acousto-optic modulator), and modulating frequency is far below
Laser frequency.Reference path is divided into two-way through beam splitter, all the way directly with measure light beam splitting after converging all the way, be incident on signal
The photoelectric detector PD of processing unit0In, reference when being handled as interference signal；Another way, which first passes through half-wave plate, makes the inclined of light
The direction that shakes is rotated by 90 °, and then passes through several beam splitters and speculum (or the 4 multiple) road that is divided into 4, with optical path converge into
It is mapped to the photoelectric detector PD of signal processing unit1~PDnIn (n=4i, i are integer).
The optical path carries out frequency modulation(PFM) by frequency modulation(PFM) device (such as acousto-optic modulator), and modulating frequency is far low
In laser frequency, and with the modulating frequency of reference path there are the signal frequencies of small frequency difference Δ f, Δ f should be in photoelectricity
Within the scope of the response frequency of detector, interference signal is enable to be responded by photodetector.Optical path is divided into two through beam splitter
Road.All the way with converging all the way after reference light beam splitting, be incident on the photoelectric detector PD of signal processing unit0In, as interference
Reference when signal processing.Another way is divided into 4 by several beam splitters and speculum (or 4 multiple) road, the survey after beam splitting
It is identical as reference path quantity to measure light path quantity.Then optical path injects vacuum chamber by polarizing beam splitter mirror, through in vacuum chamber
Speculum reflection after, reflected by polarizing beam splitter mirror, converged with reference path, be ultimately incident upon signal processing unit photoelectricity visit
Survey device PD1~PDnIn (n=4i, i are integer).
4 tunnel of measurement light being incident in vacuum chamber is one group, during the respective optical path between each group is with the axis of vacuum chamber
The heart is axisymmetricly distributed, to reduce the error of vacuum chamber mirror deformation introducing.
The signal processing unit includes interference signal processing module, heterodyne signal processing module, Phase Processing mould
Block and data calculation module.
The interference signal processing module mainly to reference light and measures light by photodetector and processing circuit
Interference signal is handled.Photodetector is functionally divided into two classes, one kind directly measurement reference path and optical path
Interference signal 0, i.e., foregoing photoelectric detector PD0.Another kind of measurement 4i (i is integer) road is reflected through vacuum chamber
Measure 1~4i of interference signal between light and corresponding reference light, i.e., foregoing photoelectric detector PD1~PDn(n=4i, i
For integer).
1~4i of interference signal is done difference frequency operation by the heterodyne signal processing module with the interference signal of reference 0 respectively,
The error that laser unstability is brought can be weeded out.Then the relative phase values for obtaining each road optical path are resolved.
The phase processing module calculates the phase between each optical path according to the measuring principle of gas refracting index
Difference weeds out the error due to environment, vacuum chamber introducing, then calculates and obtain gas refracting index value.
As shown in figure 3, the laser that stabilizing He Ne laser sends out horizontal polarization is divided into two bundles by Amici prism, respectively
As with reference to light and measurement light.
Reference light carries out frequency modulation(PFM), modulating frequency 60MHz by acousto-optic modulator.Later, reference light is by light splitting
Prism is divided into two bundles, a branch of to be directly incident in photoelectric detector PD 0 by speculum.Another beam makes polarization side by half-wave plate
To being rotated by 90 °, then passes through three groups of Amici prisms and speculum is divided into four beams, be incident on 1~PD4 of photoelectric detector PD respectively.
It measures light and carries out frequency modulation(PFM), modulating frequency 60.05MHz by acousto-optic modulator.In this way, measuring light and reference
The heterodyne frequency of light is 50kHz.Light is measured to be divided into two bundles by Amici prism, it is a branch of to converge with reference light by Amici prism,
It is incident in photoelectric detector PD 0.Another beam is divided into four beams by three groups of Amici prisms and speculum, then passes through polarization spectro
Prism and quarter-wave plate inject vacuum chamber.It after vacuum cavity reflection, is turned back by polarization splitting prism, with reference path
Converge, injects photodetector PD1~PD4 respectively.
Signal processing unit handles the interference signal of PD0~PD4 respectively first, obtains interference frequencies f0~f4.Then by f1
~f4Interference signal and f1Outer difference operation is carried out, relative phase is obtainedAccording to gas refracting index measuring principle, foundationBetween phase difference, gas refracting index n can be calculated.
Claims (5)
1. a kind of light channel structure for high-precision gas refractometry, it is characterised in that：Laser light source sends out frequency stabilization
Linearly polarized light, be divided into optical path and reference path by beam splitter；
The reference path carries out frequency modulation(PFM) by frequency modulator, and modulating frequency is far below laser frequency, reference path warp
Beam splitter is divided into two-way：All the way with converging all the way after optical path beam splitting, be incident on the photodetector of signal processing unit
PD0In, reference when being handled as interference signal；Another way, which first passes through half-wave plate, makes the polarization direction of light be rotated by 90 °, and then passes through
Cross several beam splitters and speculum be divided into 4 multiple road, converge with optical path and be incident on the photoelectricity of signal processing unit and visit
Survey device PD1~PDnIn, n=4i, i are integer；
The optical path carries out frequency modulation(PFM) by frequency modulator, and modulating frequency is far below laser frequency, and and reference light
There are frequency difference Δ f, optical paths to be divided into two-way through beam splitter for the modulating frequency on road：All the way with one after reference path beam splitting
Road is converged, and the photoelectric detector PD of signal processing unit is incident on0In, reference when being handled as interference signal；Another way passes through
Cross several beam splitters and speculum be divided into 4 multiple road, the optical path quantity after beam splitting is identical as reference path quantity, and
Optical path injects vacuum chamber by polarizing beam splitter mirror afterwards, after the speculum reflection in vacuum chamber, is reflected by polarizing beam splitter mirror,
Converge with reference path, is ultimately incident upon the photoelectric detector PD of signal processing unit1~PDnIn, n=4i, i are integer.
2. the light channel structure according to claim 1 for high-precision gas refractometry, it is characterised in that：Described
Frequency difference Δ f should enable interference signal to be responded by photodetector within the scope of the response frequency of photodetector.
3. the light channel structure according to claim 1 for high-precision gas refractometry, it is characterised in that：Described
4 tunnel of optical path being injected into vacuum chamber is one group, and the respective optical path between each group is in axis centered on the axis of vacuum chamber
It is symmetrical, to reduce the error of vacuum chamber mirror deformation introducing.
4. the light channel structure according to claim 1 for high-precision gas refractometry, it is characterised in that：Described
Signal processing unit includes interference signal processing module, heterodyne signal processing module, phase processing module.
5. the light channel structure according to claim 4 for high-precision gas refractometry, it is characterised in that：Described
Interference signal processing module by photodetector and processing circuit to the interference signal of reference path and optical path at
Reason, photoelectric detector PD0Directly measure the interference signal 0 of reference path and optical path, photoelectric detector PD1~PDnMeasure 4i
Road is through 1~4i of interference signal between the reflected optical path of vacuum chamber and corresponding reference path；The heterodyne letter
1~4i of interference signal is done difference frequency operation by number processing module with the interference signal of reference 0 respectively, and it is unstable to weed out laser light source
Property the error brought, then resolve the relative phase values for obtaining each road optical path；The phase processing module is according to gas
The measuring principle of body refractive index calculates the phase difference between each optical path, weeds out the mistake due to environment, vacuum chamber introducing
Then difference calculates and obtains gas refracting index value.
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| CN201711404648.5A CN108318420A (en) | 2017-12-22 | 2017-12-22 | A kind of light channel structure for high-precision gas refractometry |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110044847A (en) * | 2019-05-16 | 2019-07-23 | 南开大学 | It is a kind of not by the total internal reflection type refractive index sensing method of light source drift effect |
| CN110058217A (en) * | 2019-01-25 | 2019-07-26 | 北京航天计量测试技术研究所 | A kind of link air refraction real-time compensation distance measuring method altogether |
| CN110702607A (en) * | 2019-09-03 | 2020-01-17 | 西安电子科技大学 | High-cost-performance wide-spectrum photoacoustic spectrum gas detection device |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110058217A (en) * | 2019-01-25 | 2019-07-26 | 北京航天计量测试技术研究所 | A kind of link air refraction real-time compensation distance measuring method altogether |
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| CN110702607A (en) * | 2019-09-03 | 2020-01-17 | 西安电子科技大学 | High-cost-performance wide-spectrum photoacoustic spectrum gas detection device |
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Application publication date: 20180724 |