Air refractive index measuring device and method based on movable vacuum bellows
阅读说明：本技术 基于可移动真空波纹管的空气折射率测量装置和方法 (Air refractive index measuring device and method based on movable vacuum bellows ) 是由 崔建军 张鹏 陈恺 于 2021-08-10 设计创作，主要内容包括：本申请公开了基于可移动真空波纹管的空气折射率测量装置和方法,本装置包括：真空波纹管、第一谐振平面镜、第二谐振平面镜、反射镜、光源装置、控制模块、光电探测单元；光源系统同时产生两束波长不等的光束,谐振平面镜、真空波纹管和反射镜用于形成测量干涉光束,光电探测器用于生成测量干涉信号,控制模块控制真空波纹管的拉伸长度和反射镜的位置,同时对测量干涉信号进行解调,计算空气折射率。本方法包括：同时得到两束波长不等的光束的测量干涉光束,进而得到测量干涉信号,在真空波纹管的两种拉伸长度下分别对测量干涉信号进解调判断,计算空气折射率。本申请抗干扰能力强,且能够实现10～(-9)的测量精度。(The application discloses air refractive index measuring device and method based on movable vacuum bellows, this device includes: the device comprises a vacuum corrugated pipe, a first resonant plane mirror, a second resonant plane mirror, a reflector, a light source device, a control module and a photoelectric detection unit; the light source system simultaneously generates two beams of light beams with different wavelengths, the resonant plane mirror, the vacuum corrugated pipe and the reflector are used for forming a measuring interference light beam, the photoelectric detector is used for generating a measuring interference signal, the control module controls the stretching length of the vacuum corrugated pipe and the position of the reflector, and simultaneously demodulates the measuring interference signal and calculates the air refractive index. The method comprises the following steps: and simultaneously obtaining two measuring interference beams of beams with different wavelengths to further obtain measuring interference signals, demodulating and judging the measuring interference signals under two stretching lengths of the vacuum corrugated pipe respectively, and calculating the air refractive index. The method has strong anti-interference capability and can realize 10 ‑9 The measurement accuracy of (2).)
1. Air refractive index measuring device based on portable vacuum bellows, its characterized in that: the method comprises the following steps: the device comprises a vacuum corrugated pipe (11), a first resonant plane mirror (1), a second resonant plane mirror (2), a reflector, a light source device, a control module (22) and a photoelectric detection unit;
the light source device is used for generating a first light beam and a second light beam, and the wavelength of the first light beam is different from that of the second light beam;
the vacuum corrugated pipe (11) is used for generating interference peak value change for the first light beam, the first resonant plane mirror (1), the vacuum corrugated pipe (11) and the reflector are used for forming a main measurement interference light beam of the first light beam, one end of the vacuum corrugated pipe (11) close to the first resonant plane mirror (1) is fixed in position, and the other end of the vacuum corrugated pipe (11) generates displacement under the control of the control module (22);
the second resonant flat mirror (2) and the mirror are used to form a secondary measurement interference beam of the second beam;
the photoelectric detection unit is used for generating a main measurement interference signal according to the main measurement interference beam and generating a secondary measurement interference signal according to the secondary measurement interference beam;
the control module (22) is used for judging whether the main measurement interference signal and the auxiliary measurement interference signal reach a stable state or not, demodulating the main measurement interference signal and the auxiliary measurement interference signal, calculating the air refractive index, recording the interference peak value change number of the main measurement interference signal by the control module (22), and controlling the reflector to generate displacement by the control module (22).
2. The movable vacuum bellows-based air refractive index measurement device of claim 1, wherein: both ends of the vacuum corrugated pipe (11) are all lenses.
3. The movable vacuum bellows-based air refractive index measurement device of claim 1, wherein: the vacuum bellows (11) is located between the first resonant flat mirror (1) and the second resonant flat mirror (2), and the movable end of the vacuum bellows (11) moves between the first resonant flat mirror (1) and the second resonant flat mirror (2).
4. The movable vacuum bellows-based air refractive index measurement device of claim 1, wherein: the measuring device further comprises a first displacement table (6), the first displacement table (6) is fixedly connected with the movable end of the vacuum corrugated pipe (11), and the first displacement table (6) is used for driving the movable end to generate displacement under the control of the control module (22).
5. The movable vacuum bellows-based air refractive index measurement device of claim 1, wherein: the measuring device further comprises a second displacement table (7), the second displacement table (7) is fixedly connected with the reflecting mirror, and the second displacement table (7) is used for driving the reflecting mirror to generate displacement under the control of the control module (22).
6. The air refractive index measuring method based on the movable vacuum corrugated pipe is characterized by comprising the following steps of:
simultaneously generating a first laser and a second laser, wherein the wavelength of the first laser is not equal to that of the second laser;
a main measurement interference beam of the first laser is formed through a first resonant plane mirror (1), a vacuum corrugated pipe (11) and a reflecting mirror, and a secondary measurement interference beam of the second laser is formed through a second resonant plane mirror (2) and the reflecting mirror;
obtaining a main measurement interference signal according to the main measurement interference beam, and obtaining a secondary measurement interference signal according to the secondary measurement interference beam;
demodulating the main measurement interference signal and the auxiliary measurement interference signal, controlling the reflector to generate displacement according to the demodulation result, and obtaining the initial position of the reflector when the main measurement interference signal and the auxiliary measurement interference signal reach an interference peak point simultaneously;
controlling a movable end of a vacuum corrugated pipe (11) to generate preset displacement, and demodulating the main measurement interference signal to obtain the number of interference peak value changes of the main measurement interference signal in the displacement process;
moving the reflector, and obtaining the scanning position of the reflector when the main measurement interference signal and the auxiliary measurement interference signal reach the interference peak point simultaneously again;
and calculating the air refractive index based on the wavelength of the first laser, the wavelength of the second laser, the number of interference peak value changes, the displacement length generated by the movable end of the vacuum corrugated pipe (11), the initial position of the reflector and the scanning position, and finishing the measurement of the air refractive index.
7. The method for measuring the refractive index of the air based on the movable vacuum bellows as claimed in claim 6, wherein: the steps further include: before demodulating the main measurement interference signal and the auxiliary measurement interference signal, performing steady state detection on the main measurement interference signal and the auxiliary measurement interference signal, and when the main measurement interference signal and the auxiliary measurement interference signal reach a steady state simultaneously, beginning to demodulate the main measurement interference signal and the auxiliary measurement interference signal.
8. The method for measuring the refractive index of the air based on the movable vacuum bellows as claimed in claim 7, wherein: the calculation formula of the air refractive index is as follows:
wherein n is the refractive index of air, lambda0Is the wavelength, lambda, of the first laser light1Is the wavelength of the second laser,/0Is the initial position of the mirror,/1And delta l is the displacement length generated by the movable end of the vacuum corrugated pipe (11) for the scanning position of the reflector, and N is the number of interference peak value changes of the main measurement interference signal.
Technical Field
The application belongs to the field of air refractive index measurement, and particularly relates to an air refractive index measurement device and method based on a movable vacuum corrugated pipe.
Background
The refractive index of air plays an important role in the fields of optical precision measurement and the like, and the accuracy of the final measurement result is directly influenced.
At present, most of air refractive index measuring methods adopt sensors such as a temperature sensor, a humidity sensor and an atmospheric pressure sensor to measure and obtain parameters such as air temperature, humidity and atmospheric pressure, and then an Edlen formula is adopted to calculate and obtain the air refractive index, but the measuring precision of the method is limited by the measuring precision of the temperature, the humidity and the atmospheric pressure, particularly, the temperature sensor adopts a platinum resistor which needs to be supplied with power, the resistor can generate heat, the measuring accuracy is influenced, errors are brought to the measurement, and the measuring precision is generally lower than 5 multiplied by 10-8。
Disclosure of Invention
The application provides an air refractive index measuring device and method based on movable vacuum bellows, two beams of light beams with different wavelengths are adopted, interference influence of different lengths of the movable vacuum bellows on a light path is utilized to form a main measurement interference signal and an auxiliary measurement interference signal, the magnitude of optical path change is demodulated based on an optical vernier principle, high-precision measurement of the air refractive index is achieved, and the problem that the anti-interference capability in the prior art is poor is solved.
In order to achieve the above purpose, the present application provides the following solutions:
air refractive index measuring device based on portable vacuum bellows includes: the device comprises a vacuum corrugated pipe, a first resonant plane mirror, a second resonant plane mirror, a reflector, a light source device, a control module and a photoelectric detection unit;
the light source device is used for generating a first light beam and a second light beam, and the wavelength of the first light beam is different from that of the second light beam;
the vacuum corrugated pipe is used for generating interference peak value change to the first light beam, the first resonant plane mirror, the vacuum corrugated pipe and the reflector are used for forming a main measurement interference light beam of the first light beam, one end of the vacuum corrugated pipe close to the first resonant plane mirror is fixed, and the other end of the vacuum corrugated pipe is controlled by the control module to generate displacement;
the second resonant mirror and the mirror are used to form a secondary measurement interference beam of the second beam;
the photoelectric detection unit is used for generating a main measurement interference signal according to the main measurement interference beam and generating a secondary measurement interference signal according to the secondary measurement interference beam;
the control module is used for judging whether the main measurement interference signal and the auxiliary measurement interference signal reach a stable state or not, demodulating the main measurement interference signal and the auxiliary measurement interference signal, calculating the air refractive index, recording the interference peak value change number of the main measurement interference signal, and controlling the reflector to generate displacement.
Preferably, both ends of the vacuum bellows are all lenses.
Preferably, the vacuum bellows is located between the first resonant mirror and the second resonant mirror, and a movable end of the vacuum bellows moves between the first resonant mirror and the second resonant mirror.
Preferably, the measuring device further comprises a first displacement table, the first displacement table is fixedly connected with the movable end of the vacuum bellows, and the first displacement table is used for driving the movable end to generate displacement under the control of the control module.
Preferably, the measuring device further comprises a second displacement table, the second displacement table is fixedly connected with the reflecting mirror, and the second displacement table is used for driving the reflecting mirror to generate displacement under the control of the control module.
The application also discloses an air refractive index measuring method based on the movable vacuum corrugated pipe, which comprises the following steps:
simultaneously generating a first laser and a second laser, wherein the wavelength of the first laser is not equal to that of the second laser;
forming a main measurement interference beam of the first laser through a first resonant plane mirror, a vacuum corrugated pipe and a reflector, and forming a secondary measurement interference beam of the second laser through a second resonant plane mirror and the reflector;
obtaining a main measurement interference signal according to the main measurement interference beam, and obtaining a secondary measurement interference signal according to the secondary measurement interference beam;
demodulating the main measurement interference signal and the auxiliary measurement interference signal, controlling the reflector to generate displacement according to the demodulation result, and obtaining the initial position of the reflector when the main measurement interference signal and the auxiliary measurement interference signal reach an interference peak point simultaneously;
controlling a movable end of the vacuum corrugated pipe to generate preset displacement, and demodulating the main measurement interference signal to obtain the number of interference peak value changes of the main measurement interference signal in the displacement process;
moving the reflector, and obtaining the scanning position of the reflector when the main measurement interference signal and the auxiliary measurement interference signal reach the interference peak point simultaneously again;
and calculating the air refractive index based on the wavelength of the first laser, the wavelength of the second laser, the number of interference peak value changes, the displacement length generated by the movable end of the vacuum corrugated pipe, the initial position of the reflector and the scanning position, and finishing the measurement of the air refractive index.
Preferably, the steps further comprise: before demodulating the main measurement interference signal and the auxiliary measurement interference signal, performing steady state detection on the main measurement interference signal and the auxiliary measurement interference signal, and when the main measurement interference signal and the auxiliary measurement interference signal reach a steady state simultaneously, beginning to demodulate the main measurement interference signal and the auxiliary measurement interference signal.
Preferably, the calculation formula of the air refractive index is as follows:
wherein n is the refractive index of air, lambda0Is the wavelength, lambda, of the first laser light1Is the wavelength of the second laser,/0Is the initial position of the mirror,/1Is the place of the reflectorAnd in the scanning position, delta l is the displacement length generated by the movable end of the vacuum corrugated pipe, and N is the number of interference peak value changes of the main measurement interference signal.
The beneficial effect of this application does:
the application discloses air refracting index measuring device and method based on portable vacuum bellows, to two bundles of light beams of different wavelength, through the movable end that removes vacuum bellows, make vacuum bellows produce different length in order to produce different interference influence to light path, adopt the optics vernier principle to interfere decimal analysis, accomplish the air refracting index and measure, because the light path route of two bundles of light beams is different, consequently can to a great extent restrain other environment undulant influence, improved the interference killing feature by a wide margin. Meanwhile, by precisely controlling the displacement of the vacuum bellows and the reflecting mirror, 10 can be realized-9The measurement accuracy of (2).
Drawings
In order to more clearly illustrate the technical solution of the present application, the drawings needed to be used in the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without inventive exercise.
FIG. 1 is a schematic diagram showing the effect of the change of Fabry-Perot cavity on the interference peak generated by laser light of different wavelengths;
FIG. 2 is a schematic structural diagram of an air refractive index measuring device based on a movable vacuum bellows in the embodiment of the present application;
FIG. 3 is a schematic flow chart of an air refractive index measurement method based on a movable vacuum bellows in the embodiment of the present application.
Description of the drawings: 1. a first resonant mirror; 2. a second resonant mirror; 3. a pyramid reflector; 4. a first photodetector; 5. a second photodetector; 6. a first displacement stage; 7. a second displacement stage; 11. a vacuum bellows; 21. a laser generator; 22. and a control module.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In order to make the aforementioned objects, features and advantages of the present application more comprehensible, the present application is described in further detail with reference to the accompanying drawings and the detailed description.
The vernier effect was originally applied to improve the resolution of length measurement (e.g. vernier caliper), and its working principle lies in that the small scale difference between the main scale and the vernier is used to measure the length. The optical vernier principle is the application of vernier effect in optical interference, when two lasers with wavelength difference perform Fabry-Perot interference, two interference signals with small difference can be formed, and the interference signals have the same work as that of a main scale and a vernier of a vernier caliper. By demodulating these two interference signals, sub-micron resolution displacement readings can be obtained through the optical vernier and the optical main scale.
Fabry-Perot interference is multi-beam interference, according to the formula of multi-beam interference:
wherein, P is the light intensity of transmitted light, a is the amplitude of incident light, R is the light intensity reflectivity of the Fabry-Perot cavity resonator mirror, d is the Fabry-Perot cavity length, and lambda is the wavelength of the incident light. The relationship between the separation Δ d of the folded Fabry-Perot cavity interference peaks and the interference wavelength λ can be expressed as:
as shown in fig. 1, interference peaks with different pitches appear with the change of the Fabry-Perot cavity according to the wavelength of the interference laser. If the interference wavelengths of the two Fabry-Perot cavities are very close, the interference peak intervals formed after the two Fabry-Perot cavities respectively interfere are also very close. For example, the difference between the intervals of interference peaks formed by interference at a wavelength of 633nm and 632.996nm is 1 pm. The optical main scale and the optical vernier can be constructed by utilizing the two interference peaks with different equal intervals, and the optical vernier scales with different resolutions can be formed according to different wavelength differences.
According to the above principle, the present application designs an air refractive index measuring device based on a movable vacuum bellows, including: the device comprises a vacuum corrugated pipe 11, a first resonant plane mirror 1, a second resonant plane mirror 2, a reflector, a light source device, a control module 22 and a photoelectric detection unit, wherein the light source device adopts a laser generator 21 and simultaneously generates a first laser and a second laser, and higher accuracy can be obtained by adopting stable laser; the reflecting mirror adopts a pyramid reflecting mirror 3, so that the laser generator 21, the first resonant flat mirror 1, the vacuum corrugated pipe 11, the second resonant flat mirror 2 and the pyramid reflecting mirror 3 are sequentially arranged in a straight line, and the light paths of the two beams of laser are basically consistent.
In addition, the reflectivity of the first resonant plane mirror 1 is a first preset reflectivity, and the position is fixed; the reflectivity of the upper end 1/4 part and the reflectivity of the lower end 1/4 part of the second resonant plane mirror 2 are both second preset reflectivity, and the rest parts are hollowed out and fixed in position; the reflectivity of the two resonance plane mirrors is 2.5% -97.6%, and can be the same or different. The one end position that vacuum bellows 11 is close to first resonance level crossing 1 is fixed, marks as the stiff end, and the other end can produce the displacement under control system's control, marks as the movable end, and the both ends of vacuum bellows 11 are full lens, and vacuum bellows 11 moves between first resonance level crossing 1 and second resonance level crossing 2, produces the peak value of interference change to first laser. In addition, in order to ensure the displacement accuracy of the vacuum bellows 11 and the pyramid reflector 3, a first displacement stage 6 and a second displacement stage 7 are respectively added for respectively driving the vacuum bellows and the pyramid reflector 3 to generate accurate displacement under the control of the control module 22. Further, the photoelectric detection unit is divided into a first photoelectric detector 4 and a second photoelectric detector 5 to accurately obtain photoelectric signals of the two laser beams.
The laser generator 21 simultaneously generates a first laser beam and a second laser beam, which have different wavelengths and are respectively marked as lambda0、λ1(ii) a The first laser sequentially passes through the first resonant plane mirror 1 and the vacuum corrugated pipe 11, then passes through the hollow part of the second resonant plane mirror 2 to irradiate the pyramid reflector 3, and finally forms a main measurement interference beam after being reflected by the pyramid reflector 3, the main measurement interference beam also passes through the hollow part in the middle of the second resonant plane mirror 2, the vacuum corrugated pipe 11 and the first resonant plane mirror 1, the first photoelectric detector 4 receives the main measurement interference beam to generate a main measurement interference signal I0(ii) a The second laser beam partially passes through the upper end 1/4 of the second resonant plane mirror 2 and is reflected by the pyramid reflecting mirror 3 to finally form a secondary measurement interference beam, the secondary measurement interference beam partially passes through the lower end 1/4 of the second resonant plane mirror 2, and the second photodetector 5 receives the secondary measurement interference beam to generate a secondary measurement interference signal I1. The primary and secondary measurement interference signals both enter the control module 22.
The control module 22 is configured to detect whether both the main measurement interference signal and the sub measurement interference signal reach a stable state, and in addition, the control module 22 is further configured to demodulate the main measurement interference signal and the sub measurement interference signal, determine whether both the two interference signals reach an interference peak value, detect a change number of the interference peak values of the main measurement interference signal, obtain a change number of the interference peak values of the main measurement interference signal, and calculate an air refractive index.
The control module 22 is also connected with the first displacement table 6 and the second displacement table 7, and controls the two displacement tables to displace.
In the embodiment, a first resonant plane mirror 1, a vacuum corrugated pipe 11 and a pyramid reflecting mirror 3 are marked to form a main Fabry-Perot cavity, the first resonant plane mirror 1, the vacuum corrugated pipe 11, the pyramid reflecting mirror 3 and a second displacement stage 7 form a main Fabry-Perot interferometer, a second resonant plane mirror 2 and the pyramid reflecting mirror 3 are marked to form a sub Fabry-Perot cavity, and the second resonant plane mirror 2, the pyramid reflecting mirror 3 and the second displacement stage 7 form a sub Fabry-Perot interferometer; the auxiliary Fabry-Perot cavity is a common cavity of the main Fabry-Perot interferometer and the auxiliary Fabry-Perot interferometer. Therefore, two sets of interferometers are formed, the main measuring laser beam and the auxiliary measuring laser beam have a certain wavelength difference and move through the pyramid reflecting mirror 3 to form an optical vernier, and the air refractive index can be accurately calculated by combining the size and the number.
The embodiment also discloses an air refractive index measurement method based on optical vernier Fabry-Perot interference, which comprises the following steps of:
s102, the laser generator 21 outputs the wavelengths lambda respectively at the same time0、λ1The two laser beams are respectively denoted as a first laser beam and a second laser beam.
S104. wavelength is lambda0Is emitted to a main Fabry-Perot interferometer to form a main measuring interference beam with the wavelength lambda1The second laser is emitted to a secondary Fabry-Perot interferometer to form a secondary measurement interference light beam in an interference mode;
s106, receiving the main measurement interference light beam by the first photoelectric detector 4 to obtain a main measurement interference signal I0The secondary measurement interference beam is received by the second photodetector 5 to obtain a secondary measurement interference signal I1；
S108, the control module 22 measures interference signals I for the main and the auxiliary0、I1Whether the steady state is reached is judged, and within a certain time period t, I0、I1Mean value of drift values I0t、I1tWhile being smaller than a certain threshold value I00、I11Then represents the main and auxiliary measurement interference signals I0、I1Reaching a stable state;
s110. control module 22 is to I0、I1Performing demodulation judgment, and simultaneously controlling the second displacement stage 7 to drive the pyramid reflector 3 to move, when the control module 22 detects I0、I1When the interference peak point is reached, the second displacement table 7 is controlled to stop moving, and the initial position l of the second displacement table 7 at the moment is recorded0。
S112, the control module 22 controls the first displacement table 6 to drive the vacuum corrugated pipe 11 to generate displacement, the movement distance is delta l, and in the movement process, the demodulation system carries out main measurement interference signal I0And demodulating to obtain the number N of interference peak value changes.
S114, the control module 22 controls the second displacement table 7 to drive the pyramid reflector 3 to generate displacement, and when the control module 22 detects I again0、I1When the interference peak point is reached at the same time, the scanning position l of the second displacement table 7 at that time is recorded1。
S116, calculating the refractive index of air:
n is the refractive index of air, lambda0Is the wavelength, lambda, of the first laser light1Is the wavelength of the second laser,/0Is the initial position of the second displacement table 7,/1And the initial position of the second displacement stage 7 is delta l, the displacement length generated by the movable end of the vacuum bellows 11 is delta l, and N is the number of interference peak value changes of the main measurement interference signal.
Carry-in typical values: when the frequency difference of the two lasers is 1GHz, the positioning accuracy of the first displacement table 6 is 300nm, the positioning accuracy of the second displacement table 7 is 10nm, the decimal demodulation peak value discrimination is 750nm, and the moving length delta l of the vacuum corrugated pipe 11 is 100mm, the measurement accuracy of the air refractive index can reach 3.4 multiplied by 10-11. It can be seen that the calculation method of the present application can realize 10 by making a certain wavelength difference between the main and auxiliary measuring laser beams and adopting the optical vernier principle to perform interference decimal analysis-11The air refractive index measurement accuracy of (1).
In the description of the present application, it is to be understood that the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the present invention, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be considered limiting.
The above-described embodiments are merely illustrative of the preferred embodiments of the present application, and do not limit the scope of the present application, and various modifications and improvements made to the technical solutions of the present application by those skilled in the art without departing from the spirit of the present application should fall within the protection scope defined by the claims of the present application.