CN110793445A - Multi-channel synchronous absolute distance measuring method and device based on all-fiber frequency domain interference - Google Patents
Multi-channel synchronous absolute distance measuring method and device based on all-fiber frequency domain interference Download PDFInfo
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Abstract
The embodiment of the application provides a multichannel synchronous absolute distance measuring method and device based on all-fiber frequency domain interference, and relates to the technical field of absolute distance precision measurement. The method comprises the following steps: the broadband light source is divided into n paths of measuring light, and the n paths of measuring light return n paths of reference light and corresponding detecting light after passing through the optical fiber probe and the measuring target. Integrating the spectra after the frequency domain interference of all the n reference lights and the corresponding detection lights and recording the light intensityWherein Ii(f) For the light intensity after the interference of n reference lights and the corresponding detection light frequency domain, I (f) is processed in a segmented way to obtain a corresponding power spectrum function GiAnd (t) further obtaining the absolute distance between the end face of the optical fiber probe corresponding to each channel and the surface of the reflector. The method can synchronously measure the absolute distance between the surfaces of a plurality of measured objects and the light emergent end surface of the optical fiber probe with high precision, the measurement precision is superior to 5 mu m, and the measurement range can reach200mm。
Description
Technical Field
The application relates to the technical field of absolute distance precision measurement, in particular to a multichannel synchronous absolute distance measurement method and device based on all-fiber frequency domain interference.
Background
As the first fundamental physical quantity of physics, distance (or length) has a wide application in the fields of scientific research, engineering applications, and instrument manufacturing, and the range involved in the measurement of distance is quite wide. The frequency domain interference ranging technology is a novel ranging technology, and the technology demodulates frequency domain interference fringes formed by interference of two light waves in a frequency domain (a light intensity-frequency coordinate system) to obtain an optical path difference between the two light beams. The frequency domain interference distance measurement technology has the measurement range of micro-nanometer measurement precision of hundreds of millimeters, and can be used in the fields of precision thickness measurement, contour measurement and the like. The frequency domain interference ranging technology based on the all-fiber structure has the advantages of strong anti-interference capability, high reliability, small size of the front-end ranging probe, simple structure and good application prospect.
At present, a frequency domain interferometric ranging technology usually adopts a fiber optic spectrometer to record frequency domain signals, and only one measured distance can be obtained in a single measurement. For measuring a plurality of distances, an optical path switching device needs to be introduced, and because the scanning speed of a spectrum splitting mechanism (such as a grating and a tunable light source) in the optical fiber spectrometer is generally in the millimeter or second order, and the optical path switching device is in the hundred millisecond order, the overall measuring speed is in the hundred millisecond order, and the problems that the measuring speed is not high and the bandwidths of the light source and the spectrometer cannot be fully utilized exist.
Disclosure of Invention
The application provides a multichannel synchronous absolute distance measuring method and device based on all-fiber frequency domain interference, the device can synchronously measure the absolute distance between the surfaces of a plurality of reflectors and the emergent light end face of an optical fiber probe with high precision, the measuring precision is superior to 5 mu m, the measuring range can reach 200mm, and the problems that in the prior art, when the measurement of a plurality of distances is carried out, the measuring speed is not high, the bandwidth of a light source and a spectrometer is fully utilized, and the measuring efficiency is improved are solved.
The embodiment of the application is realized by the following steps:
a multi-channel synchronous absolute distance measuring method based on all-fiber frequency domain interference comprises the following steps: the broadband light source is divided into n paths of measuring light, the n paths of measuring light return n paths of reference light and corresponding detecting light after passing through the optical fiber probe and the measuring target, the reference light is an optical signal returned after the measuring light is reflected by the optical fiber probe, and the detecting light is an optical signal returned after the measuring light irradiates the surface of the measuring target after passing through the optical fiber probe. Integrating the spectra after the frequency domain interference of all the n reference lights and the corresponding detection lights and recording the light intensity
Wherein Ii(f) For the light intensity after the interference of n reference lights and the corresponding detection light frequency domain, I (f) is processed in a segmented way to obtain a corresponding power spectrum function GiAnd (t) further obtaining the absolute distance between the end face of the optical fiber probe corresponding to each channel and the surface of the reflector. The optical fiber probe 3 of the technical scheme can be a focusing optical fiber probe, and the distance from the front end of the probe to the reflector is 30-200 mm. The reflector (i.e. the object to be measured) can be metal or nonmetal, and breaks through the current situation that some sensors have noThe method measures this limitation of non-metallic objects.
Preferably, the specific process of obtaining the absolute distance between the end face of the fiber probe and the surface of the reflector corresponding to each channel according to the power spectrum function g (t) includes: when G is0Characteristic time points of the (t) function, i.e. G0When the maximum point of (t) is at t-0, it appears in the power spectrum that the characteristic time point is at the coordinate t-0,
And
the three maximum value points of (1) are sequentially called as a characteristic time point 1, a characteristic time point 2 and a characteristic time point 3; by interpreting the positions of the 2 nd and 3 rd characteristic time points on the time coordinate, the method can obtain
And then obtaining the distance d corresponding to the channel, wherein c is the speed of light.
Preferably, the probe light and the reference light are light sources transmitted by a coaxial structure. The structure has the advantages that except for the light path from the optical fiber probe to the measurement target, the light path of the reference light and the light path of the detection light are completely the same, and the structure can effectively reduce the measurement interference caused by the environmental fluctuation.
Preferably, n is 1 or more and 16 or less. In the structure, after the spectrometer performs single spectrum scanning, multipath frequency domain interference signals are superposed in the spectrum signals, multipath distance measurement results can be obtained simultaneously through processing, the bandwidth of the light source and the spectrometer is fully utilized, and the measurement efficiency is improved.
Preferably, the measuring light is transmitted to the fiber probe through a fiber optic circulator; the detection light and the reference light are transmitted continuously through the optical fiber circulator after passing through the optical fiber probe.
A multichannel synchronous absolute distance measuring device based on all-fiber frequency domain interference comprises:
the wavelength division multiplexer is used for dividing the broadband light source into n measuring light paths; n-path optical fiberA probe for irradiating the emitters with n paths of measuring light paths respectively to obtain n paths of reference light distribution function Ir(f) And corresponding probe light distribution function Id(f) (ii) a The spectrum integration device is used for performing spectrum integration on all n paths of reference light and corresponding detection light beams and recording the frequency domain interference light intensity of the reference light and the corresponding detection light beams
And the processor is used for obtaining a power spectrum function G (t) according to the I (f), and obtaining the absolute distance between the end face of the optical fiber probe corresponding to each channel and the surface of the reflector according to the power spectrum function G (t). The device is a non-contact absolute distance measuring device and can measure the distance between the surface of a measured object and the end face of the probe on line. The optical fiber probe 3 can be a focusing optical fiber probe, and the distance from the front end of the probe to the reflector is 30 mm-200 mm. The measurement target can be metal or nonmetal, and the limitation that some current sensors cannot measure nonmetal objects is overcome.
Preferably, the specific process of obtaining the absolute distance between the end face of the fiber probe and the surface of the reflector corresponding to each channel by the processor according to the power spectrum function g (t) is as follows: when G is0Characteristic time points of the (t) function, i.e. G0When the maximum point of (t) is at t-0, it appears in the power spectrum that the characteristic time point is at the coordinate t-0,
And
the three maximum value points of (1) are sequentially called as a characteristic time point 1, a characteristic time point 2 and a characteristic time point 3; by interpreting the positions of the 2 nd and 3 rd characteristic time points on the time coordinate, the method can obtain
And further obtaining the distance d corresponding to the channel.
Preferably, the measuring light is transmitted to the fiber probe through a fiber optic circulator; the detection light and the reference light are transmitted to the spectrum integration device continuously through the optical fiber circulator after passing through the optical fiber probe; the wavelength division multiplexer and the demultiplexer have the same number of wavelength multiplexing channels, namely the number of the outgoing ports of the wavelength division multiplexer is the same as the number of the incoming ports of the demultiplexer. The invention adopts the wavelength division multiplexer and the demultiplexer, can compress the frequency domain interference signals collected by the multi-channel probe into the same spectrum signal, and can obtain the distances measured by different channels by carrying out sectional processing on the corresponding wavelength range signals in the spectrum signal.
Preferably, the spectrum integration device comprises a demultiplexer 41 and a fiber optic spectrometer 42. And the wavelength division multiplexer 1, the optical fiber circulator 2, the n-path optical fiber probe 3 and the spectrum integration device 4 all adopt all-fiber devices, so that the whole device has compact structure, high vibration resistance and high reliability, and is favorable for popularization and application. In the structure, after the spectrometer performs single spectrum scanning, multipath frequency domain interference signals are superposed in the spectrum signals, multipath distance measurement results can be obtained simultaneously through processing, the bandwidth of the light source and the spectrometer is fully utilized, and the measurement efficiency is improved. n is not less than 1 and not more than 16. The broadband light source, the wavelength division multiplexer 1, the optical fiber circulator 2, the n optical fiber probes 3 and the tail fibers of the spectrum integration device 4 are connected through a flange plate or a fusion welding method, and the method can reduce the insertion loss when different optical fiber devices are connected.
Preferably, the probe light and the reference light are light sources transmitted by a coaxial structure. The coaxial structure is beneficial to avoiding the influence of factors such as environment temperature vibration and the like on measurement, and has strong anti-interference capability.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments of the present application will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and that those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.
Fig. 1 is a schematic flowchart of a multichannel synchronous absolute distance measurement method based on all-fiber frequency domain interference according to an embodiment of the present disclosure.
Fig. 2 is a schematic structural diagram of a multi-channel synchronous absolute distance measuring device based on all-fiber frequency domain interference according to an embodiment of the present disclosure.
Icon: 1-a wavelength division multiplexer; 2-a fiber optic circulator; 3-a fiber optic probe; 4-a spectrum integration device; 41-a demultiplexer; 42-fiber optic spectrometer; and 5, a processor.
Detailed Description
The technical solution in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application.
First, description of the invention:
1. the reference light is the light reflected and returned by the optical fiber probe; the detection light corresponding to the detection light refers to light which is irradiated to the reflector after passing through the optical fiber probe and then returns through the optical fiber probe.
2. The emergent end face of the optical fiber probe 3 is plated with a reflection increasing film to improve the Fresnel reflection light intensity of the end face, and the film plating medium and the reflectivity of the end face of the self-focusing lens rod are determined according to the surface reflectivity of the reflector.
3. The wavelength division multiplexer 1 and the demultiplexer 41 have the same number of wavelength multiplexing channels, i.e. the number of outgoing ports of the wavelength division multiplexer is the same as the number of incoming ports of the demultiplexer.
4. The spectrum of the broadband light source is a C-band spectrum (1528 nm-1570 nm) or a C + L-band spectrum (1528 nm-1604 nm). The wavelength response range of the fiber optic spectrometer 42 includes the spectral range of the broadband light source.
5. The invention relates to a non-contact absolute distance measuring device which can measure the distance between the surface of a measured object and the end surface of a probe on line. Non-contact refers to optical measurement means. The on-line measurement refers to actual environmental measurement.
The working principle of the invention is as follows: referring to fig. 1 and 2, in the embodiment of the present invention, the apparatus includes a wavelength division multiplexer 1, an n-way fiber probe 3, a spectrum integration apparatus 4 and a processor 5.
And the wavelength division multiplexer 1 is used for dividing the broadband light source into n measuring light paths.
n path lightA fiber probe 3 for irradiating the emitters with n measuring light paths respectively to obtain n reference light distribution functions Ir(f) And corresponding probe light distribution function Id(f)。
A spectrum integration device 4 for performing spectrum integration on all the n reference light paths and the corresponding detection light beams and recording the frequency domain interference light intensity
Wherein, Ir(f) As a function of the distribution of the reference light, Id(f) Is a distribution function of the probe light.
And the processor 5 is configured to obtain a power spectrum function g (t) according to the i (f), and obtain the absolute distance between the end face of the optical fiber probe 3 and the surface of the reflector corresponding to each channel according to the power spectrum function g (t).
Wherein the wavelength division multiplexer 1 is connected with the n paths of optical fiber probes 3 through the n paths of optical fiber circulators 2.
The measuring process of the invention, referring to fig. 1, includes:
step S1, the broadband light source is divided into n paths of measurement light by the wavelength division multiplexer 1.
In this embodiment, all the optical fiber devices are connected according to fig. 2, and power supplies of various parts, such as a broadband light source, the optical fiber spectrometer 42, the processor 5 and the like, are turned on; the broadband light source passes through n wavelength division multiplexing channels of the wavelength division multiplexer 1 according to the central wavelength and the working bandwidth to form n paths of measuring light.
Step S2, returning n paths of reference light and corresponding detection light after n paths of measurement light pass through the optical fiber probe; the detection light is a light signal returned by irradiating the surface of the emitter with the measuring light after passing through the optical fiber probe.
Step S3, performing spectrum integration on all n reference light paths and corresponding detection light beams and recording the frequency domain interference light intensity
Ir(f) As a function of the distribution of the reference light, Id(f) Is a distribution function of the probe light.
And step S4, obtaining the absolute distance between the end face of the optical fiber probe and the surface of the reflector corresponding to each channel according to the power spectrum function G (t) corresponding to I (f).
Embodiment one (implemented by a fiber optic circulator, one path of measuring light): referring to fig. 2, the device includes a broadband light source connected to an incident port of a wavelength division multiplexer 1, an exit port of the wavelength division multiplexer 1 connected to a first port of an optical fiber circulator 2, a second port of the optical fiber circulator 2 connected to an optical fiber probe 3, a third port of the optical fiber circulator 2 connected to an incident port of a demultiplexer 41, and an exit port of the demultiplexer 41 sequentially connected to an optical fiber spectrometer 42 and a computer 5.
The optical fiber circulator 2 is a three-port circulator, light input from the first port is output from the second port, light input from the second port is output from the third port, and the first port and the third port are highly isolated from each other.
When the measuring light is emitted from the light emergent end face of the optical fiber probe 3, due to the Fresnel effect, a part of the light is directly reflected from the light emergent end face to form a path of reference beam, and the other part of the light is irradiated on the surface of a measured object to be reflected and collected and returned by the optical fiber probe 3 to form a path of detection beam. Since the reference beam and the probe beam are both broadband beams and have a certain amount of optical path difference, interference fringes with light intensity varying with wavelength, i.e., frequency domain interference fringes, appear in the wavelength domain. The frequency domain interference fringe signal returns to the second port of the optical fiber circulator 2 through the optical fiber, and is transmitted to the spectrum integration device 4 through the third port of the optical fiber circulator 2, wherein in the spectrum integration device 4, the demultiplexer 41 performs spectrum integration on the frequency domain interference fringe signals collected by all channels, the integrated signals are transmitted to the optical fiber spectrometer 42 for recording, the processor 5 receives the integrated spectrum signals from the optical fiber spectrometer 42, performs fourier transform on the frequency domain interference light intensity i (f) of the spectrum signals to obtain a power spectrum function g (t) of the frequency domain interference light with time t as a horizontal coordinate, and finally obtains the absolute distance between the end face of the optical fiber probe 3 and the reflector surface corresponding to each channel according to the power spectrum function g (t).
Example two (multiplexed measurement light): on the basis of the first embodiment, the output light beam of the broadband light source is wavelength division multiplexed by the wavelength division multiplexer 1 according to the central wavelength and the working bandwidth into n paths of measuring light, and the n paths of measuring light are transmitted to the first port of the optical fiber circulator 2 corresponding to the channel and are transmitted to the optical fiber probe 3 through the second port of the optical fiber circulator 2.
When the n paths of measuring light pass through the n paths of optical fiber probes, the n paths of measuring light return to the n paths of reference light and the corresponding n paths of detecting light. In this embodiment, the value of n is greater than or equal to 1 and less than or equal to 8. And the center wavelength interval among the channels of the wavelength division multiplexer 1 is 20nm +/-3 nm, the channel isolation is not less than 50dB, the working bandwidth of the single channel is 13nm +/-1 nm, and the center wavelength interval is larger than the working bandwidth of the single channel. The wavelength division multiplexer 1 channel and the demultiplexer 41 connected to the same optical fiber circulator 2 have the same central wavelength. And the quantity of the wavelength division multiplexing channels of the two wavelength division multiplexing channels is the same, namely the quantity of the outgoing ports of the wavelength division multiplexing channels is the same as that of the incoming ports of the demultiplexer.
Example three: the optical fiber circulator can also adopt a four-port optical fiber coupler, wherein a first port of the four-port optical fiber coupler is directly connected with a second port and is coupled with a third port, and a fourth port of the four-port optical fiber coupler is directly connected with the third port and is coupled with the second port. Namely, the following combinations can be formed: (1) the light input from the first port is output from the second port, and the light input from the second port is output from the fourth port; (2) the light input from the second port is output from the first port, and the light input from the first port is output from the third port; (3) the light input from the third port is output from the fourth port, and the light input from the fourth port is output from the second port; (4) the light input from the fourth port is output from the third port, and the light input from the third port is output from the first port; the opposite direction is highly isolated. It should be understood that the connection mode can be selected by analogy with the connection mode of the three-port circulator, and the implementation modes include four modes of 1), 2), 3) and 4):
1) a first port of the optical fiber circulator 2 is connected with an emergent port of the wavelength division multiplexer 1, a second port of the optical fiber circulator 2 is connected with the optical fiber probe 3, and a fourth port of the optical fiber circulator 2 is connected with an incident port of the demultiplexer 41; the broadband light source reaches the optical fiber probe after passing through the first port of the optical fiber circulator 2 and the second port of the optical fiber circulator 2; when the light is emitted from the light emergent end face of the optical fiber probe 3, due to the Fresnel effect, a part of light is directly reflected from the light emergent end face to form a path of reference beam, and the other part of light irradiates on the surface of a measured object to be reflected and is collected and returned by the optical fiber probe 3 to form a path of detection beam. Since the reference beam and the probe beam are both broadband beams and have a certain amount of optical path difference, interference fringes with light intensity varying with wavelength, i.e., frequency domain interference fringes, appear in the wavelength domain. The frequency domain interference fringe signal returns to the second port of the optical fiber circulator 2 through the optical fiber, and is transmitted to the spectrum integration device 4 through the fourth port of the optical fiber circulator 2.
2) The second port of the optical fiber circulator 2 is connected with the emergent port of the wavelength division multiplexer 1, the first port of the optical fiber circulator 2 is connected with the optical fiber probe 3, and the third port of the optical fiber circulator 2 is connected with the incident port of the demultiplexer 41; the broadband light source reaches the optical fiber probe after passing through the second port of the optical fiber circulator 2 and the first port of the optical fiber circulator 2; when the light is emitted from the light emergent end face of the optical fiber probe 3, due to the Fresnel effect, a part of light is directly reflected from the light emergent end face to form a path of reference beam, and the other part of light irradiates on the surface of a measured object to be reflected and is collected and returned by the optical fiber probe 3 to form a path of detection beam. Since the reference beam and the probe beam are both broadband beams and have a certain amount of optical path difference, interference fringes with light intensity varying with wavelength, i.e., frequency domain interference fringes, appear in the wavelength domain. The frequency domain interference fringe signal returns to the first port of the optical fiber circulator 2 through the optical fiber, and is transmitted to the spectrum integration device 4 through the third port of the optical fiber circulator 2.
3) A third port of the optical fiber circulator 2 is connected with an emergent port of the wavelength division multiplexer 1, a fourth port of the optical fiber circulator 2 is connected with the optical fiber probe 3, and a second port of the optical fiber circulator 2 is connected with an incident port of the demultiplexer 41; the broadband light source reaches the optical fiber probe after passing through the third port of the optical fiber circulator 2 and the fourth port of the optical fiber circulator 2; when the light is emitted from the light emergent end face of the optical fiber probe 3, due to the Fresnel effect, a part of light is directly reflected from the light emergent end face to form a path of reference beam, and the other part of light irradiates on the surface of a measured object to be reflected and is collected and returned by the optical fiber probe 3 to form a path of detection beam. Since the reference beam and the probe beam are both broadband beams and have a certain amount of optical path difference, interference fringes with light intensity varying with wavelength, i.e., frequency domain interference fringes, appear in the wavelength domain. The frequency domain interference fringe signal returns to the fourth port of the optical fiber circulator 2 through the optical fiber, and is transmitted to the spectrum integration device 4 through the second port of the optical fiber circulator 2.
4) The fourth port of the optical fiber circulator 2 is connected with the emergent port of the wavelength division multiplexer 1, the third port of the optical fiber circulator 2 is connected with the optical fiber probe 3, and the first port of the optical fiber circulator 2 is connected with the incident port of the demultiplexer 41; the broadband light source reaches the optical fiber probe after passing through the fourth port of the optical fiber circulator 2 and the third port of the optical fiber circulator 2; when the light is emitted from the light emergent end face of the optical fiber probe 3, due to the Fresnel effect, a part of light is directly reflected from the light emergent end face to form a path of reference beam, and the other part of light irradiates on the surface of a measured object to be reflected and is collected and returned by the optical fiber probe 3 to form a path of detection beam. Since the reference beam and the probe beam are both broadband beams and have a certain amount of optical path difference, interference fringes with light intensity varying with wavelength, i.e., frequency domain interference fringes, appear in the wavelength domain. The frequency domain interference fringe signal returns to the third port of the optical fiber circulator 2 through the optical fiber, and is transmitted to the spectrum integration device 4 through the first port of the optical fiber circulator 2.
Example four: on the basis of the first embodiment and the third embodiment, the specific process of obtaining the absolute distance between the end face of the fiber probe and the surface of the reflector corresponding to each channel by the processor according to the power spectrum function g (t) is as follows:
s41: when G is0Characteristic time points of the (t) function, i.e. G0When the maximum point of (t) is at t-0, it appears in the power spectrum that the characteristic time point is at the coordinate t-0,
And
the three maximum value points of (1) are sequentially called as a characteristic time point 1, a characteristic time point 2 and a characteristic time point 3; specifically, the method comprises the following steps: taking Fourier transform to I (f) to obtain a power spectrum function G (t) of the frequency domain interference light with time t as an abscissa:
in the formula b1＝(a1+a2-a1a2) Andis a constant number, G0(t) is I0(f) A power spectrum function after fourier transformation.
S42: by interpreting the positions of the 2 nd and 3 rd characteristic time points on the time coordinate, the method can obtain
And then obtaining the distance d corresponding to the channel, wherein c is the speed of light.
The distance between the end face of the optical fiber probe 3 corresponding to the recording channel and the surface of the object to be measured is d, and the distribution function of the light intensity of the light wave output by the broadband light source 1 along with the light wave frequency f is I0(f) The distribution function of the electric field intensity with the light wave frequency f is E0(f) The two relations are as follows;
I0(f)＝|E0(f)|2(2)
according to the formula (2), obtaining a distribution function I of the light intensity of the reference beam along with the frequency f of the light waver(f) Comprises the following steps:
Ir(f)＝a1I0(f)＝a1|E0(f)|2(3)
wherein a is1(0<a1Not more than 1) is the reflectivity of the light emergent end face of the optical fiber probe 3.
Because the distance between the light emergent end surface of the optical fiber probe 3 and the surface of the measured object is d, the multi-propagation time of the detection beam relative to the reference beam is d
(c is the speed of light in vacuum), so that the electric field intensity is delayed relative to the phase of the reference beam to generate exp (2 π Tf), and according to equation (2), the distribution function I of light intensity with the frequency f of the light wave is obtainedd(f) Comprises the following steps:
wherein a is2(0<a2Not more than 1) is the reflection efficiency of the measured object, and the detection light beam and the reference light beam generate frequency domain interference after meeting in the optical fiber probe.
As can be seen from equations (3) and (4), I (f) ═ Id(f)+Ir(f)；
The mathematical expression for the frequency domain interference light intensity I (f) recorded by the fiber optic spectrometer 42 can be written as:
example five: on the basis of the first to fourth embodiments, the tuning method of the fiber probe 3 is as follows: the light emergent end face of the optical fiber probe 3 is aligned to the reflector, the alignment angle of the optical fiber probe 3 is adjusted until interference fringes with the contrast ratio larger than 0.01 appear in the optical fiber spectrometer 42, it is indicated that the reference light waves reflected by the fresnel on the end face of the optical fiber probe and the detection light waves reflected by the surface of the reflector have a certain optical path difference, frequency domain interference fringes are formed, and then the frequency domain interference light intensity i (f) is obtained by performing spectrum integration through the demultiplexer 41 and the optical fiber spectrometer 42.
Example six: on the basis of the first to the fifth embodiments, the broadband light source, the wavelength division multiplexer 1, the optical fiber circulator 2, the optical fiber probe 3, the demultiplexer 41 and the tail fiber of the optical fiber spectrometer 42 are connected through flanges or a fusion method.
Example seven: on the basis of the first to sixth embodiments, the optical fiber probe 3 irradiates the light wave on the reflector surface and simultaneously receives the reflected light wave returning from the reflector surface. The reference light waves reflected fresnel-ally from the end face of the fiber probe 3 and the probe light waves reflected from the reflector surface are transmitted in a coaxial manner in the pigtail of the fiber probe 3.
The above description is only an example of the present application and is not intended to limit the scope of the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
Claims (10)
1. A multi-channel synchronous absolute distance measuring method based on all-fiber frequency domain interference is characterized by comprising the following steps:
dividing a broadband light source into n paths of measuring light;
returning n paths of measuring light to n paths of reference light and corresponding detecting light after the n paths of measuring light pass through the optical fiber probe; the detection light is a light signal returned by irradiating the surface of the emitter with the measuring light after passing through the optical fiber probe;
performing spectrum integration on all n reference light paths and corresponding detection light beams and recording frequency domain interference light intensity of the reference light paths and the corresponding detection light beams
Ir(f) As a function of the distribution of the reference light, Id(f) Is a distribution function of the probe light;
and according to the power spectrum function G (t) corresponding to the I (f), obtaining the absolute distance between the end face of the optical fiber probe corresponding to each channel and the surface of the reflector.
2. The method of claim 1, wherein obtaining the absolute distance between the end face of the fiber-optic probe and the surface of the reflector corresponding to each channel according to the power spectrum function g (t) comprises:
when G is0Characteristic time points of the (t) function, i.e. G0When the maximum point of (t) is at t-0, it appears in the power spectrum that the characteristic time point is at the coordinate t-0,
And
the three maximum value points of (1) are sequentially called as a characteristic time point 1, a characteristic time point 2 and a characteristic time point 3;
by interpreting the positions of the 2 nd and 3 rd characteristic time points on the time coordinate, the method can obtainAnd then obtaining the distance d corresponding to the channel, wherein c is the speed of light.
3. The method of claim 1 or 2, wherein the probe light and the reference light are transmitted in a coaxial configuration.
4. The method of claim 3, wherein n is equal to or greater than 1 and equal to or less than 16.
5. The method of claim 1, 2 or 4, wherein the measurement light is transmitted to the fiber optic probe through a fiber optic circulator; the detection light and the reference light are transmitted continuously through the optical fiber circulator after passing through the optical fiber probe.
6. The utility model provides a synchronous absolute distance measuring device of multichannel based on full optical fiber frequency domain is interfered which characterized in that includes:
the wavelength division multiplexer is used for dividing the broadband light source into n measuring light paths;
n optical fiber probes for irradiating the n measuring light paths with the emitters respectively to obtain n reference light distribution functions Ir(f) And corresponding probe light distribution function Id(f)；
A spectrum integration device for performing spectrum integration on all n reference light beams and corresponding detection light beams and recording the frequency domain interference light intensity I (f) | Ir(f)+Id(f)|2；
And the processor is used for obtaining a power spectrum function G (t) according to the I (f), and obtaining the absolute distance between the end face of the optical fiber probe corresponding to each channel and the surface of the reflector according to the power spectrum function G (t).
7. The apparatus of claim 6, wherein the processor obtains the absolute distance between the end face of the fiber probe and the surface of the reflector corresponding to each channel according to the power spectrum function g (t) by the following specific steps:
when G is0Characteristic time points of the (t) function, i.e. G0When the maximum point of (t) is at t-0, it appears in the power spectrum that the characteristic time point is at the coordinate t-0,
And
the three maximum value points of (1) are sequentially called as a characteristic time point 1, a characteristic time point 2 and a characteristic time point 3;
by interpreting the positions of the 2 nd and 3 rd characteristic time points on the time coordinate, the method can obtain
And further obtaining the distance d corresponding to the channel.
8. The apparatus of claim 6 or 7, wherein the measuring light is transmitted to the fiber optic probe through a fiber optic circulator; the detection light and the reference light are transmitted to the spectrum integration device continuously through the optical fiber circulator after passing through the optical fiber probe; the wavelength division multiplexer and the demultiplexer have the same number of wavelength multiplexing channels, namely the number of the outgoing ports of the wavelength division multiplexer is the same as the number of the incoming ports of the demultiplexer.
9. The apparatus of claim 8, wherein said spectrum integration apparatus comprises a demultiplexer, a fiber optic spectrometer; the circulator, the wavelength division multiplexer, the n-path optical fiber probe and the spectrum integration device all adopt all-fiber devices; n is greater than or equal to 1 and less than or equal to 16; the broadband light source, the wavelength division multiplexer, the optical fiber circulator, the n-path optical fiber probe and the tail fiber of the spectrum integration device are connected through a flange plate or a welding method.
10. The apparatus of claim 6, 7 or 9 wherein the probe light and the reference light are transmitted as a source of light in a coaxial configuration.
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