CN105866071B - A kind of fiber optic interferometric method surveys the device of refractive index - Google Patents
A kind of fiber optic interferometric method surveys the device of refractive index Download PDFInfo
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- CN105866071B CN105866071B CN201610383317.7A CN201610383317A CN105866071B CN 105866071 B CN105866071 B CN 105866071B CN 201610383317 A CN201610383317 A CN 201610383317A CN 105866071 B CN105866071 B CN 105866071B
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- refractive index
- sample cell
- collimator
- faraday
- rotating mirror
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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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- 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
- G01N2021/458—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods using interferential sensor, e.g. sensor fibre, possibly on optical waveguide
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Abstract
The invention discloses a kind of device of optical fibre interference refractive index, including laser light source, circulator, sample cell, photodetector, demodulation module, collimators.One end of sample cell is equipped with collimator, there is 10% reflection, 90% transmission-type lens in collimator, and the rear end of sample cell is faraday's rotating mirror.The light that laser issues becomes directional light incidence into sample cell after collimator, and is reflected in rear end by faraday's rotating mirror.Faraday's rotating mirror avoids the interference in sample cell between incident light and reflected light.The reflected light of collimator and the reflected light two-way light of faraday's rotating mirror can interfere phenomenon.Measurement accuracy of the present invention is high, and structure is simply easily achieved miniaturization, can measure to gas, a variety of samples of liquid, and the range for measuring refractive index is wide, and digitlization automatic measurement may be implemented.
Description
Technical field
The present invention relates to a kind of fiber optic interferometric method survey refractive index device, by optical fibre interference principle for gas,
The refractive index of liquid carries out the measurement of high-precision digital.
Background technique
Currently, the method for traditional measurement refractive index mainly passes through Abbe refractometer measuring instrument, Abbe refractometer measurement
Instrument is mainly the total reflection principle by light, full transmitting phenomenon is formed on the surface of fluid to be measured and prism, thus with critical angle
Position be region that axis forms light and shade boundary, the refractive index to sample is realized in the position by detecting light and shade border region
Measurement.Due to the principle with total reflection, the range for measuring refractive index is subject to certain restrictions, it is higher for refractive index or
Lower sample can not measure.Abbe refractometer measuring instrument is built by pure physical optics device, optical path build with adjustment difficulty,
Instrument integrated operation is complicated, and volume is big, is not easy to realize miniaturization and digitized measurement.Abbe refractometer measuring instrument is chiefly used in liquid
The measurement of the refractive index of body has certain limitation for the measurement of gas refracting index.
It is pungent superintend and direct it is strong et al. (a kind of measuring device for liquid refractive index based on fiber optic interferometric, the patent No.:
201520180701.5) measuring device for liquid refractive index of fiber optic interferometric a kind of is reported, it is not mended between fiber optic interferometric two-arm
It repays, extraneous vibration and temperature influence can bring additional optical path difference, and cause measurement inaccurate, device entirety poor anti jamming capability,
Accuracy and precision decline.
Summary of the invention
In order to overcome traditional refractive index measuring instrument optical path to build difficulty, use is complicated for operation, and it is automatic to can not achieve digitlization
The deficiencies of measurement, the ranges of indices of refraction of measurement is smaller, the present invention provides a kind of instrument of optical fibre interference refractive index, passes through light
Fine interferometry technology carries out high-acruracy survey to the refractive index of sample, and strong antijamming capability, refractometry range is wide, detection
Digitlization real-time measurement function may be implemented in specimen types multiplicity, instrument.
The technical solution adopted by the present invention to solve the technical problems is: three ends of circulator respectively with laser, sample
Pond is connected with photodetector.The laser that laser issues reaches sample cell by circulator, and sample cell is a transparent glass
Glass hole capital after selling all securities has injection port and outlet, and different samples can be injected by injection port, and the sample for detecting completion can lead to
Outlet is crossed to be discharged.The front end of sample cell is equipped with optical fiber collimator, and collimator is provided with the saturating of 10% reflection 90% transmission
Mirror, lens can be by a part of the reflection of generation incident light back into optical fibers, and a part of light is injected into sample cell by collimator.In addition,
The incident light of optical fiber can be converted into directional light injection by collimator, faraday's rotating mirror is housed in the rear end of sample cell, on mirror surface
There is etch-proof plated film, corrosion of the sample to faraday's rotating mirror can be prevented.Sample cell is passed through by the directional light of collimator outgoing
Afterwards, it is reflected on faraday's rotating mirror of rear end, the reflected light in the reflected light and collimator of sample cell can interfere existing
As.The polarization state of incident light can be rotated by 90 ° by faraday's rotating mirror, incident light and faraday's rotating mirror in this way in sample cell
Reflected light would not interfere, avoid the variation of the additional striped caused by interfering.When in sample pool be vacuum state
When, optical path difference is constant between the reflected light of front collimation device and the reflected light of rear end faraday's rotating mirror, and interference fringe is stablized.
When being filled with sample, refractive index can occur to change accordingly in sample pool, and corresponding optical path difference can be generated between two-way reflected light,
Interference fringe can also generate corresponding variation.Device sheet is as all optical fibre structure, and measurement accuracy is high, and corresponding speed is fast, avoids
The complicated process that conventional light path is built.
When in use, for gas and liquid sample, first sample cell can be evacuated, at this moment the refraction in sample pool
Rate is n=1, then tested gas or liquid sample are injected into sample pool, and corresponding refractive index changes, and optical path difference will
Corresponding change occurs, while interference fringe will generate corresponding variation, the another of circulator terminates on photodetector
Face can detect the corresponding phase change of interference fringe, and demodulation module is demodulated it can be concluded that corresponding interference information later,
From which further follow that the refractive index of sample to be tested.
A kind of fiber optic interferometric method surveys the device of refractive index, including laser, circulator, optical fiber collimator, injection port, farad
The laser of rotating mirror, outlet, sample cell, photodetector and demodulation module, laser output passes through circulator incidence sample introduction
There are collimator in product pond, the front end of sample cell, there is reflection/transmission formula lens in collimator, and there is faraday's rotating mirror in the rear end of sample cell,
The reflected light of collimator and the reflected light of faraday's rotating mirror can interfere phenomenon, and the another of circulator is terminated with photodetection
Device can convert optical signals to electric signal and pass to demodulation module again, corresponding refractive index value is obtained after being demodulated.
The laser that the laser need to use monochromaticjty good, selects the semiconductor laser of 1550nm.
The wavelength of the laser can choose 1310nm, 1064nm, 780nm or 650nm.
The sample cell is made of transparent glass, length 250mm, internal diameter 10mm, outer diameter 20mm.
The sample cell can be changed to the form of cuboid according to the actual situation.
The sample cell front end is equipped with collimator, the lens equipped with 10% reflection, 90% transmission in collimator.
Lens in the collimator can choose 20% reflection 80% transmission lens, 30% reflection 70% transmission it is saturating
Mirror, light transmittance can be selected by different Refractive Index Samples.
The rear end of the sample cell is equipped with faraday's rotating mirror, the polarization state of incident light can be rotated by 90 °.
The host computer should use relevant demodulating algorithm, to obtain the value of corresponding refractive index.
The demodulation module, which can connect PC machine terminal, also can connect embedded system, as Portable type measurement unit.
Compared with existing apparatus for measuring refractive index, the present invention is had the advantage that
(1) all optical fibre structure, instead of building for traditional optical path, the optical path for avoiding complexity is built and calibration procedures,
And it can be increased with electromagnetism interference, stability.
(2) optical fibre interference principle is used, measurement accuracy is high, and responding range is big.
(3) light path design can offset the influence of external environment temperature and vibration, improve measurement accuracy and anti-interference
Ability.
(4) refractive index of liquids and gases sample can be measured, measurement specimen types are more, refractometry range
Greatly.
Detailed description of the invention
Fig. 1 is optical fibre interference refractive index device system diagram.
Fig. 2 is sample cell sectional view.
Specific embodiment
As depicted in figs. 1 and 2, the device that a kind of fiber optic interferometric method surveys refractive index has laser (1), circulator (2), optical fiber
Collimator (3), injection port (4), faraday's rotating mirror (5), outlet (6), sample cell (7), photodetector (8) and demodulation module
(9) it forms.
A kind of fiber optic interferometric apparatus for measuring refractive index, overall structure are as shown in Figure 1.The laser that semiconductor laser issues
It is incident in circulator by optical fiber, circulator will be inside laser irradiation to sample cell further through optical fiber.The front end of sample cell is
Optical fiber collimator, the lens for thering is in collimator 10% reflection 90% to transmit.Lens can be by a part of the reflection of generation incident light back into optical fibers
Interior, a part of light is injected into sample cell by collimator.In addition, the incident light of optical fiber can be converted into directional light by collimator
It projects, faraday's rotating mirror is housed in the rear end of sample cell.By method of the directional light of collimator outgoing after sample cell, in rear end
It draws and is reflected on rotating mirror.The polarization state of incident light is rotated by 90 ° outgoing by faraday's rotating mirror, is avoided and is entered in sample cell
Penetrate the interference between light and reflected light.In use, collimator is tuned into level first, then being transmitted into sample cell by collimator
In light by rear end faraday's rotating mirror reflection and again may be coupled in collimator, in the reflected light and collimator of sample cell
Reflected light will interfere phenomenon.
Here the length for enabling connection circulator optical fiber is l1, the length of sample cell is l2.Optical fibre refractivity is n1, sample cell
The refractive index of interior sample is n2Light path for collimator reflected light isLight path for sample cell reflected light isThe optical path difference of two-way interference light is
The optical path difference of interference is related with the length in Refractive Index Sample pond of sample unrelated with the length of incident optical.So for
Extraneous vibration interference, temperature change all will not influence the variation of optical path difference, so that device overall stability improves, anti-interference energy
Power is strong.
Sample cell can be evacuated by stock layout hole when use, at this moment form stable interference fringe.Later by sample
Product are injected into sample cell by infusing sample hole, are injected the refractive index after sample in sample cell and are occurred corresponding variation, refractive index from
Vacuum n=1 changes to n=n2, optical path difference also has corresponding variationInterference fringe will appear movement.Annular
The other end of device has also connected photodetector, and photodetector can convert optical signals to electric signal and be transmitted to demodulation module,
Demodulating algorithm operation is carried out, the quantity of stripe order recognition is obtained, passes through formula: It can obtain
The refractive index of respective sample out.
Claims (6)
1. a kind of fiber optic interferometric method surveys the device of refractive index, including laser (1), circulator (2), optical fiber collimator (3), sample introduction
Mouth (4), faraday's rotating mirror (5), outlet (6), sample cell (7), photodetector (8) and demodulation module (9), laser output
Laser by circulator incidence into sample cell, there is collimator in the front end of sample cell, have reflection/transmission formula lens in collimator,
There is faraday's rotating mirror in the rear end of sample cell, and the reflected light of collimator and the reflected light of faraday's rotating mirror can interfere phenomenon, ring
The another of shape device is terminated with photodetector, can convert optical signals to electric signal and pass to demodulation module again, after being demodulated
Obtain corresponding refractive index value.
2. the device that a kind of fiber optic interferometric method according to claim 1 surveys refractive index, it is characterised in that: the laser
Select the semiconductor laser of 1550nm.
3. the device that a kind of fiber optic interferometric method according to claim 1 surveys refractive index, it is characterised in that: the sample cell
(7) it is made of transparent glass, length 250mm, internal diameter 10mm, outer diameter 20mm.
4. the device that a kind of fiber optic interferometric method according to claim 1 surveys refractive index, it is characterised in that: sample cell front end dress
There are collimator, the lens equipped with 10% reflection, 90% transmission in collimator.
5. the device that a kind of fiber optic interferometric method according to claim 1 surveys refractive index, it is characterised in that: the rear end of sample cell
Equipped with faraday's rotating mirror, the polarization state of incident light can be rotated by 90 °.
6. the device that a kind of fiber optic interferometric method according to claim 1 surveys refractive index, it is characterised in that: demodulation module can be with
Connection PC machine terminal also can connect embedded system, as Portable type measurement unit.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106990413B (en) * | 2017-06-02 | 2023-04-18 | 吉林大学 | System and method for heterodyne type full-coherent terahertz three-dimensional high-resolution imaging |
| CN107957407B (en) * | 2017-11-22 | 2023-12-26 | 盘锦雨源新创意开发推广有限公司 | Probe type digital display refractometer |
| CN114112994B (en) * | 2021-11-29 | 2023-10-20 | 广东电网有限责任公司广州供电局 | Portable refractive index measuring device |
| CN115219562A (en) * | 2022-07-14 | 2022-10-21 | 湖北工程学院 | Solution concentration detection method, device, equipment and storage medium |
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| WO2004088290A1 (en) * | 2003-04-02 | 2004-10-14 | Rand Afrikaans University | A fibre optic sensor for measurement of refractive index |
| CN103134775A (en) * | 2011-11-30 | 2013-06-05 | 中国计量学院 | Optical fiber liquid refractive index and temperature sensor |
| CN103412371A (en) * | 2013-07-29 | 2013-11-27 | 华中科技大学 | Faraday rotary mirror capable of simultaneously carrying out polarization state conversion on multiple paths of optical signals |
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2016
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| WO2004088290A1 (en) * | 2003-04-02 | 2004-10-14 | Rand Afrikaans University | A fibre optic sensor for measurement of refractive index |
| CN103134775A (en) * | 2011-11-30 | 2013-06-05 | 中国计量学院 | Optical fiber liquid refractive index and temperature sensor |
| CN103412371A (en) * | 2013-07-29 | 2013-11-27 | 华中科技大学 | Faraday rotary mirror capable of simultaneously carrying out polarization state conversion on multiple paths of optical signals |
| CN104535534A (en) * | 2014-12-15 | 2015-04-22 | 哈尔滨工程大学 | Device and method for measuring refractive index distribution profile of optical fiber preform rod based on white light interferometry absolute optical path comparison method |
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| CN205719967U (en) * | 2016-06-02 | 2016-11-23 | 吉林大学 | A kind of fiber optic interferometric method surveys the device of refractive index |
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Inventor after: Chen Jiandong Inventor after: Gao Wenzhi Inventor after: Cui Hongliang Inventor after: Li Ya Inventor before: Chen Jiandong Inventor before: Gao Wenzhi Inventor before: Cui Hongliang Inventor before: Li Ya |
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