CN110793444A - Two-stage all-fiber frequency domain interference ranging method and device - Google Patents
Two-stage all-fiber frequency domain interference ranging method and device Download PDFInfo
- Publication number
- CN110793444A CN110793444A CN201911014491.4A CN201911014491A CN110793444A CN 110793444 A CN110793444 A CN 110793444A CN 201911014491 A CN201911014491 A CN 201911014491A CN 110793444 A CN110793444 A CN 110793444A
- Authority
- CN
- China
- Prior art keywords
- light
- optical fiber
- frequency domain
- domain interference
- stage
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/026—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness by measuring distance between sensor and object
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Length Measuring Devices By Optical Means (AREA)
- Instruments For Measurement Of Length By Optical Means (AREA)
Abstract
The embodiment of the application provides a two-stage all-fiber frequency domain interference distance measuring method and device, and relates to the technical field of absolute distance precision measurement. The method comprises the following steps: the broadband light source generates two paths of detection light and two paths of reference light through two-stage cascaded frequency domain interference light paths, wherein the two-stage cascaded frequency domain interference light paths refer to a first-stage frequency domain interference light path and a second-stage frequency domain interference light path, the spectrometer integrates and records six frequency domain interference signals I (f) generated by superposition of the two paths of detection light and the two paths of reference light, a corresponding power spectrum function G (t) is obtained according to the I (f), and a maximum value point meeting conditions in the maximum value points of G (t) is selected to obtain a distance value d to be measured. The optical fiber probe is convenient and easy to operate, can measure the absolute distance between the surface of a measured object and the light emergent end surface of the optical fiber probe with high resolution, has the working distance of 200mm, has the precision superior to 5 mu m, and has the measuring range of 100 mm.
Description
Technical Field
The application relates to the technical field of absolute distance precision measurement, in particular to a two-stage all-fiber frequency domain interference distance measurement method and device.
Background
As the first basic physical quantity of physics, a range involved in distance (or length) measurement is quite wide, and among them, macro precision distance measurement relates to the fields of precision metrology, micro electro mechanical systems, precision machining, and the like. At present, sensors such as capacitance type and fiber bragg grating type are often used for precise micro-distance ranging. The capacitive sensor is a non-contact sensor, is not influenced by nonmetal factors such as dust and the like during working, has the characteristics of low power consumption and long service life, but a measuring object is required to be a metal conductor, and the measuring precision is poor and can only reach the micron order. The fiber Bragg grating type sensor is commonly used for gap measurement and is a contact type sensor, the measurement precision is generally in a micron level, but besides the change of grating intervals caused by the fact that the sensor is extruded by the change of a measured gap, the grating period is also influenced by the temperature, the uncertainty factor of measurement is more, the sensor needs to be calibrated before use, and the defect limits the wide application of the sensor.
In recent years, an all-fiber frequency domain interference absolute distance measurement technology for absolute distance measurement is disclosed, which adopts an all-fiber optical path with strong anti-interference capability and high reliability as a basic optical path framework and has the characteristics of non-contact, high precision and large measuring range. The working distance of the traditional frequency domain interference distance measurement technology is equal to the measuring range thereof, and the measuring range (working distance) is only tens of millimeters generally due to the limitation of the wavelength resolution of a spectrometer. In order to meet the typical machining and detection requirements, such as penetration measurement in laser welding, geometric parameter measurement of a workpiece with the size of hundreds of millimeters and the like, the working distance needs to be increased so as to reserve enough operating space and avoid the workpiece from being scratched and damaged by a measuring head. In conclusion, the conventional interferometric ranging technology has the problems of short measuring range and over-small working distance (hundreds of millimeters).
Disclosure of Invention
The device is convenient and easy to operate, can measure the absolute distance between the surface of a measured object and the light emergent end face of the optical fiber probe with high resolution, has the working distance of 200mm, has the precision superior to 5 mu m and the measuring range of 100mm, and greatly improves the working distance on the basis of the traditional coaxial frequency domain interference distance measuring technology.
The embodiment of the application is realized by the following steps:
a two-stage all-fiber frequency domain interference ranging method comprises the following steps: the broadband light source generates two paths of detection light and two paths of reference light through two-stage cascaded frequency domain interference light paths; integrating and recording six frequency domain interference signals I (f) generated by superposition of the two paths of detection light and the two paths of reference light by the spectrometer, obtaining a corresponding power spectrum function G (t) according to the I (f), and selecting a maximum value point meeting conditions from maximum value points of G (t) to obtain a distance value d to be measured; the two-stage cascade frequency domain interference optical path refers to a first-stage frequency domain interference optical path and a second-stage frequency domain interference optical path. According to the two-stage all-fiber frequency domain interference light path provided by the invention, a reference distance is introduced, and a high-frequency domain interference signal generated when the measurement distance is hundreds of millimeters is subjected to down-conversion, so that the number of frequency domain interference fringes is reduced, the frequency conversion signal can be recorded by a spectrometer with limited wavelength resolution, and a high-precision microspur measurement result is obtained. The invention effectively improves the working distance of the traditional frequency domain interference system, and makes the system become a new micrometer-level high-precision micro-distance measuring method.
Preferably, according to the limit relation between the reference distance dr and the distance d to be measured, selecting a maximum value point meeting the condition from the maximum value points of G (t); specifically, maximum value points satisfying the conditions among the maximum value points of G (t) are obtained, and the maximum value points are determined according to the limiting relationshipAnd G (t) selecting a characteristic time point which meets the condition in the power spectrum function, and interpreting the position of the characteristic time point on a time coordinate to obtain the distance d to be measured.
Preferably, the first-stage frequency domain interference optical path comprises a first optical fiber circulator and an optical fiber reflection cavity, a broadband light source generates light waves, the light waves enter the optical fiber reflection cavity through the first optical fiber circulator, reference light and corresponding detection light are returned through the optical fiber reflection cavity, the detection light is a light signal returned by irradiating the surface of an emitter with measurement light after passing through an optical fiber probe, when an optical fiber spectrometer with the wavelength resolution of △ lambda not less than 0.01nm is used, the cavity length of the optical fiber reflection cavity is 240mm at most, the measuring range can reach 120mm, the working distance can reach 120 mm-240 mm, and is 2 times of that of the traditional full-optical fiber frequency domain interference distance measurement technology (when the same spectrometer is used as recording equipment, the maximum working distance of the traditional technology is only 120 mm).
Preferably, the optical fiber reflection cavity comprises a first optical fiber probe, a reflection cavity body and a reflector; the first optical fiber probe and the reflector are respectively arranged on two end faces of the reflection cavity; light waves generated by the broadband light source are reflected by the first optical fiber probe to form reference light, and meanwhile, the light waves transmitted by the first optical fiber probe are reflected by the reflector to form detection light; the reference light and the detection light are emitted through the first circulator.
Preferably, the second-stage frequency domain interference optical path comprises a second optical fiber circulator, a second optical fiber probe and a measured object; after the reference light is emitted from the first optical fiber circulator, the reference light enters the second optical fiber probe through the second optical fiber circulator and returns to the first reference light and the corresponding first detection light; meanwhile, the detection light enters a second optical fiber probe through a second optical fiber circulator and returns first reference light and corresponding first detection light; the first detection light and the second detection light are detection light which is emitted by the second optical fiber probe and returns to the surface of the object to be detected; and the distance from the light emergent end surface of the second optical fiber probe to the surface of the object to be measured is the distance d to be measured.
Preferably, the broadband light source, the first optical fiber circulator, the second optical fiber circulator, the first optical fiber probe, the second optical fiber probe and the optical fiber pigtail of the optical fiber spectrometer are connected through flanges or a fusion method.
The first and second optical fiber probes are flat-head quartz optical fibers or optical fiber self-focusing lens rods, and the optical fiber probes are small in structure, can be used in extreme environments of complex electromagnetism, high temperature, high pressure and the like, and have strong applicability. The optical fiber probe irradiates light waves on the surface of the reflector and simultaneously receives the light waves reflected from the surface of the reflector, and the coaxial structure is adopted to eliminate the influence of external environment fluctuation on the measurement result. The light emergent end face of the flat-end quartz optical fiber is coated with an antireflection film so as to reduce the Fresnel reflection light intensity of the end face of the flat-end quartz optical fiber, and the coating medium and the reflectivity of the end face of the quartz optical fiber are determined according to the surface reflectivity of a reflector. The light emergent end face of the optical fiber self-focusing lens rod is plated with a reflection increasing film so as to improve the Fresnel reflection light intensity of the end face of the optical fiber self-focusing lens rod, 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 a reflector. The reflector is a reflector or a reflecting film, and the cavity material of the reflector is a low-thermal expansion coefficient material or a reflecting cavity with 2 refractive index distortion points inside.
Preferably, when the power spectrum G of the broadband spectrum0(t) t is 0, and the 6dB half-width of the characteristic peak is t6dBThen, the reference distance dr and the measured distance d in the optical fiber reflecting cavity should satisfy the following relationship:
preferably, the bandwidth λ s of the broadband light source should satisfy the following relationship:
a two-stage all-fiber frequency domain interferometric ranging device comprises:
the two-stage cascade frequency domain interference light path is used for generating two paths of detection light and two paths of reference light by the broadband light source through the two-stage cascade frequency domain interference light path; the spectrometer is used for integrating and recording frequency domain interference signals I (f) of the two paths of detection light and the two paths of reference light; and the processor is used for obtaining the corresponding power spectrum function G (t) according to the I (f), and selecting the maximum value points meeting the conditions from the maximum value points of the G (t) to obtain the distance value d to be measured. The system of the invention is a non-contact absolute distance measuring device, and can nondestructively and online measure the distance between the surface of the measured object and the end face of the probe.
Preferably, the two-stage cascaded frequency domain interference optical path refers to a first-stage and a second-stage frequency domain interference optical path: the first-stage frequency domain interference light path comprises a first optical fiber circulator and an optical fiber reflecting cavity; the broadband light source generates light waves which enter the optical fiber reflecting cavity through the first optical fiber circulator; returning the reference light and the corresponding detection light through the optical fiber reflection cavity; 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. The device adopts all-fiber components, has compact structure, vibration resistance and high reliability, is favorable for popularization and application, and is expected to provide accurate absolute micro-distance measurement for the fields of scientific research and engineering technology.
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 flow chart of a dual-stage all-fiber frequency-domain interferometric ranging method according to an embodiment of the present disclosure.
Fig. 2 is a schematic structural diagram of a dual-stage all-fiber frequency-domain interferometric ranging device according to an embodiment of the present disclosure.
Icon: 1-first level frequency domain interference optical path; 11-a first fiber optic circulator; 12-a fiber optic reflective cavity; 121-a first fiber optic probe; 122-a reflective cavity; 123-a reflector; 2-a second-stage frequency domain interference optical path; 21-a second fiber optic circulator; 22-a second fiber optic probe; 23-the object to be tested; 3-a spectrometer; 4-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. light waves generated by the broadband light source are reflected by the first optical fiber probe 121 to form reference light, and meanwhile, light waves transmitted by the first optical fiber probe 121 are reflected by the reflector 123 to form detection light;
2. the spectral line width of the broadband light source is more than 2nm, and the bandwidth ranges of the first optical fiber circulator 11, the second optical fiber circulator 21 and the spectrometer 3 are consistent with the bandwidth of the broadband light source.
3. The first optical fiber circulator 11 and the second optical fiber circulator 21 are three-port circulators, light input from an ① port is output from a ② port, light input from a ② port is output from a ③ port, the ① port and a ③ port are highly isolated, and the isolation is more than 60 dB;
4. the cavity material of the optical fiber reflective cavity 12 is a low thermal expansion coefficient material such as annealed quartz or invar.
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.
The working principle of the invention is as follows: referring to fig. 1 and fig. 2, in the embodiment of the present invention, the apparatus includes a two-stage cascade frequency domain interference optical path, a spectrometer 3 and a processor 4;
the two-stage cascade frequency domain interference light path is used for generating two paths of detection light and two paths of reference light by the broadband light source through the two-stage cascade frequency domain interference light path;
the spectrometer 3 is used for integrating and recording frequency domain interference signals I (f) of the two paths of detection light and the two paths of reference light;
and the processor 4 is used for obtaining the corresponding power spectrum function G (t) according to the I (f), and selecting the maximum value points meeting the conditions from the maximum value points of the G (t) to obtain the distance value d to be measured.
The two-stage cascaded frequency domain interference optical path refers to a first-stage frequency domain interference optical path 1 and a second-stage frequency domain interference optical path 2. The first-stage frequency domain interference optical path 1 comprises a first fiber circulator 11 and a fiber reflecting cavity 12. The fiber optic reflective cavity 12 includes a first fiber optic probe 121, a reflective cavity 122, and a reflector 123. The second-stage frequency domain interference optical path 2 comprises a second fiber-optic circulator 21, a second fiber-optic probe 22 and a measured object 23.
The measuring process of the invention, referring to fig. 1, includes:
step S1, the broadband light source generates two paths of detection light and two paths of reference light through two-stage cascade frequency domain interference light paths;
step S2, integrating and recording six frequency domain interference signals I (f) generated by superposition of the two paths of detection light and the two paths of reference light by a spectrometer;
step S3, obtaining a corresponding power spectrum function G (t) according to the I (f), and selecting a maximum value point meeting the conditions from the maximum value points of the G (t) to obtain a distance value d to be measured;
first embodiment, referring to fig. 2, the apparatus includes a broadband light source connected to the ① port of the first optical fiber circulator 11, the ② port of the first optical fiber circulator 11 connected to the first optical fiber probe 121, the ③ port of the first optical fiber circulator 11 connected to the ① port of the second optical fiber circulator 21, the ② port of the second optical fiber circulator 21 connected to the second optical fiber probe 22, the ③ port of the second optical fiber circulator 21 connected to the spectrometer 3, and the spectrometer 3 connected to the computer 4.
The broadband light source generates light waves, the light waves are incident into the first optical fiber circulator 11 through a ① port of the first optical fiber circulator 11 and then are emitted from a ② port of the first optical fiber circulator 11 and enter the optical fiber reflection cavity 12, the optical fiber reflection cavity 12 is composed of a first optical fiber probe 121, a reflection cavity 122 and a reflector 123, the first optical fiber probe 121 and the reflector 123 are mounted at two ends of the reflection cavity 122, the distance from the light emitting end face of the first optical fiber probe 121 to the surface of the reflector 123 is called as a reference distance dr., the emitting end of the first optical fiber probe 121 can reflect a part of the light waves through fresnel reflection to form reference light, the reflector 123 can reflect the light waves emitted from the first optical fiber probe 121 to form probe light, the reference light and the probe light are emitted from a ③ port of the first optical fiber circulator 11 and then enter a ① port of the second optical fiber circulator 21, the reference light and the probe light are emitted from a ② port of the second optical fiber circulator 21 and enter the second optical fiber circulator 22, the light emitting end face of the second optical fiber circulator 21 and the probe light is reflected into the second optical fiber probe 22, the optical fiber circulator 22, the light and the optical fiber probe light and the probe light can be reflected by a frequency domain interference spectrum, the second optical fiber probe 22, the interference light and the interference light of the second optical fiber circulator 22 can be reflected by the optical fiber circulator 22, the probe light and the probe light can be transmitted to form a frequency domain interference spectrum recording light, the reference light spectrum recording light, the interference spectrum recording light of the optical fiber probe light spectrum recording device, the interference spectrum recording device can be obtained by the interference light of the optical fiber probe light of the optical fiber probe.
Example two: on the basis of the first embodiment, the specific process of obtaining the measured distance value d from the light emitting end surface of the second fiber probe 22 to the surface of the measured object by obtaining the corresponding power spectrum function g (t) according to i (f) and selecting the maximum value point satisfying the condition from the maximum value points of g (t):
step S31, obtaining a corresponding power spectrum function g (t) according to i (f).
In particular, note I1(f)、I2(f)、I3(f)、I4(f)、I5(f) And I6(f) Light intensity divisions of six frequency domain interference signals respectivelyAnd (4) distributing the function. Recording the distance from the light emergent end surface of the second optical fiber probe 22 to the surface of the object 23 to be measured as the distance d to be measured, and the light wave transmission time as
The second optical fiber probe 22 can reflect part of the reference light and the detection light through fresnel reflection to form first reference light and first detection light; the surface of the object to be measured 23 can reflect the first reference light and the first detection light emitted from the second fiber probe 22 to form a second reference light and a second detection light, and the electric field intensity of the light source is set as E0(f) With a light intensity of I0(f) In that respect The electric field intensities of the four light beams, i.e. the first reference light, the first probe light, the second reference light and the second probe light, are respectively E1(f)、E2(f)、E3(f)、E4(f):
E1(f)＝a1a3E0(f) (1)
E2(f)＝a2a3(1-a1)E0(f) (2)
E3(f)＝a1a4(1-a3)E0(f) (3)
E2(f)＝a2a4(1-a3)(1-a1)E0(f) (4)
Coefficient A1、A2、A3、A4Is defined as:
A1＝a1a3(5)
A4＝a1a4(1-a3) (6)
A2＝a2a3(1-a1) (7)
A3＝a2a4(1-a1)(1-a3) (8)
a1is the reflectivity of the first fiber-optic probe 121, a2Is the reflectivity of the reflector 123, a3Is the reflectivity of the second fiber-optic probe 22, a4The reflectivity of the object 23 is the four light wavesAfter superposition, six frequency domain interference signals are generated, and the light intensity distribution function of the six frequency domain interference signals is as follows:
the six light waves are returned to the ② port of the second fiber optic circulator 21 through the pigtail of the second fiber optic probe 22 and then transmitted to the spectrometer 3 through the ③ port of the second fiber optic circulator 21.
Wherein, I0(f) The distribution function of the light intensity output by the broadband light source along with the light wave frequency f and the distribution function of the electric field intensity along with the light wave frequency f are E0(f) The relationship between the two is as follows:
I0(f)＝|E0(f)|2(15)
distribution function E of electric field intensity of reference light with light wave frequency fr1(f) Comprises the following steps:
Er1(f)＝a1E0(f) (16)
wherein a is1Is the reflectivity of the first fiber optic probe 121; when the distance between the light emitting end surface of the first fiber optic probe 121 and the surface of the reflector 123 is dr, the transmission time of the light wave in the reflection cavity isWhere c is the speed of light in vacuum, at which the intensity of the probe beam is relative to that of the reference beam
The phase delay, which can be expressed as:
wherein a is2In order to be the reflectivity of the reflector 123,
the two beams are superposed to form frequency domain interference fringes.
The frequency domain interference light intensity i (f) recorded by the spectrometer 3 is fourier transformed to obtain a power spectrum function g (t) of the frequency domain interference light:
in the formula, G0(t) is I0(f) A power spectrum function after Fourier transform;
step S32, obtaining the maximum value point meeting the conditions in the maximum value points of G (t), and according to the limited relation between the reference distance dr and the distance d to be measured
And G (t) selecting qualified characteristic time points in the power spectrum function.
When G is0(t) characteristic time peak position of the power spectral function, i.e. G0When the maximum point of (t) is located at t-0, the power spectrum function g (t) of the frequency-domain interference light appears in the power spectrum as a characteristic time point at the coordinate t-0,
The 5 maximum value points are sequentially called as the 1 st to 5 th characteristic time points.
When the wavelength resolution of the spectrometer is delta lambda, the central wavelength lambda of the wide-spectrum light source0And when the reference distance dr and the distance d to be measured satisfy the following relationship:
the spectrometer can only record the frequency domain interference signal shown in equation (13), with the remaining signals being filtered as high frequency signals. G (t) only appears in the power spectrum function
The 5 th characteristic time point of (1).
In step S33, the distance d to be measured can be obtained by interpreting the position of the 5 th feature time point on the time coordinate.
Third embodiment, the first fiber optic circulator 11 and the second fiber optic circulator 21 can also adopt a four-port fiber coupler, the ① port of the coupler is directly connected with the ② port, the coupler is coupled with the ② 3 port, the ② 5 port of the coupler is directly connected with the ② 4 port, and the coupler is coupled with the ② 0 port, namely, the combination of (1) the light input from the ② 1 port is output from the ② 7 port, and the light input from the ② port is output from the ② 6 port, (2) the light input from the ② port is output from the ② 2 port, and the light input from the ③ 1 port is output from the ② 9 port, (3) the light input from the ③ port is output from the ② 8 port, and the light input from the ④ port is output from the ② port, (4) the light input from the ④ port is output from the ③ 0 port, and the light input from the ③ port is output from the ① port, and the opposite direction is highly isolated, it should be understood that the selection of the specific connection mode can be realized according to the common connection mode of the first fiber optic ring coupler 11 and the second fiber optic coupler 21.
Example four: on the basis of the first to third embodiments, the first fiber-optic probe 121 and the reflector 123 are respectively installed on two end faces of the reflective cavity 122. The mounting mode can adopt the mode of bonding, clamping or threaded connection.
Example five: on the basis of the first to the fourth embodiments, the broadband light source, the first optical fiber circulator 11, the second optical fiber circulator 21, the first optical fiber probe 121, the second optical fiber probe 22 and the optical fiber pigtail of the spectrometer 3 are connected by flanges or fusion welding.
The first optical fiber probe 121 and the second optical fiber probe 22 are flat-head quartz optical fibers or optical fiber self-focusing lens rods, the light emergent end surfaces of the flat-head quartz optical fibers are plated with antireflection films, the light emergent end surfaces of the optical fiber self-focusing lens rods are plated with antireflection films, the reflector 123 is a reflector or a reflecting film, the cavity material of the reflector is made of a low-thermal expansion coefficient material such as annealed quartz, invar and the like, or is replaced by a quartz optical fiber with 2 refractive index distortion points inside, and the quartz optical fibers with 2 refractive index distortion points can be prepared in a laser processing mode and the like.
Example six: example one to five examples of the Power Spectrum G of the broadband Spectrum0(t) t is 0, and the 6dB half-width of the characteristic peak is t6dBThen, the reference distance dr and the measured distance d in the optical fiber reflecting cavity should satisfy the following relationship:
example seven: based on the first to sixth embodiments, the bandwidth λ s of the broadband light source should satisfy the following relationship:
in the eighth embodiment, based on the first to seventh embodiments, the first fiber probe 121 and the second fiber probe 22 are calibrated in the following manner: debugging the first optical fiber probe 121 in the optical fiber reflection cavity 12 to align the first optical fiber probe with the reflector 123 in the cavity until an interference fringe with a contrast ratio larger than 0.01 appears in the spectrometer 3, which indicates that the reference light reflected by the end face Fresnel of the first optical fiber probe 121 and the detection light reflected by the surface of the reflector 123 have a certain optical path difference to form a frequency domain interference fringe, and then bonding and curing the frequency domain interference fringe by using liquid glue; the second optical fiber probe 22 is debugged to make it face the object to be measured 23 until 6 interference fringes with the contrast ratio larger than 0.01 appear in the spectrometer 3, and in the same way, it indicates that the first reference light reflected from the end face fresnel of the second optical fiber probe 22, the second reference light and the first detection light reflected from the surface of the object to be measured 23, and the second detection light has a certain optical path difference between every two, so that 6 frequency domain interference fringes are formed.
Ninth embodiment, in addition to the first to eighth embodiments, the reference light fresnel-reflected from the end face of the first fiber-optic probe 121 and the probe light reflected from the surface of the reflector 123 are transmitted in the pigtail of the first fiber-optic probe 121 in a coaxial manner. The first reference light reflected from the fresnel on the end face of the second fiber probe 22, the second reference light and the first probe light reflected from the surface of the object to be measured 23 are transmitted in a coaxial manner in the pigtail of the second fiber probe 22.
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 two-stage all-fiber frequency domain interference distance measuring method is characterized in that:
the broadband light source generates two paths of detection light and two paths of reference light through two-stage cascaded frequency domain interference light paths;
integrating and recording six frequency domain interference signals I (f) generated by superposition of the two detection lights and the two reference lights by the spectrometer;
obtaining a corresponding power spectrum function G (t) according to the I (f), and selecting a maximum value point meeting the conditions from the maximum value points of the G (t) to obtain a distance value d to be measured;
the two-stage cascade frequency domain interference optical path refers to a first-stage frequency domain interference optical path and a second-stage frequency domain interference optical path.
2. The method of claim 1, wherein the maximum point satisfying the condition among the maximum points of g (t) is selected according to the limited relationship between the reference distance dr and the distance d to be measured;
specifically, maximum value points satisfying the conditions among the maximum value points of G (t) are obtained, and the maximum value points are determined according to the limiting relationship
And G (t) selecting a characteristic time point which meets the condition in the power spectrum function, and interpreting the position of the characteristic time point on a time coordinate to obtain the distance d to be measured.
3. The method of claim 1 or 2, wherein the first stage frequency domain interferometric optical path comprises a first fiber optic circulator and a fiber optic reflective cavity; the broadband light source generates light waves which enter the optical fiber reflecting cavity through the first optical fiber circulator; returning the reference light and the corresponding detection light through the optical fiber reflection cavity; 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.
4. The method of claim 3, wherein the fiber optic reflective cavity comprises a first fiber optic probe, a reflective cavity, and a reflector; the first optical fiber probe and the reflector are respectively arranged on two end faces of the reflection cavity; light waves generated by the broadband light source are reflected by the first optical fiber probe to form reference light, and meanwhile, the light waves transmitted by the first optical fiber probe are reflected by the reflector to form detection light; the reference light and the detection light are emitted through the first circulator.
5. The method of claim 1, 2 or 4, wherein the second-stage frequency domain interference optical path comprises a second fiber optic circulator, a second fiber optic probe and the object to be measured;
after the reference light is emitted from the first optical fiber circulator, the reference light enters the second optical fiber probe through the second optical fiber circulator and returns to the first reference light and the corresponding first detection light; meanwhile, the detection light enters a second optical fiber probe through a second optical fiber circulator and returns first reference light and corresponding first detection light; the first detection light and the second detection light are detection light which is emitted by the second optical fiber probe and returns to the surface of the object to be detected; and the distance from the light emergent end surface of the second optical fiber probe to the surface of the object to be measured is the distance d to be measured.
6. The method of claim 5, wherein the broadband light source, the first optical fiber circulator, the second optical fiber circulator, the first optical fiber probe, the second optical fiber probe and the fiber pigtail of the fiber spectrometer are connected by flanges or fusion welding;
the first and second fiber probes are flat-head quartz fibers or fiber self-focusing lens rods; plating an anti-reflection film on the light emergent end surface of the flat-end quartz optical fiber, and plating an anti-reflection film on the light emergent end surface of the optical fiber self-focusing lens rod; the reflector is a reflector or a reflecting film; the cavity material of the reflector is a low thermal expansion coefficient material or a reflecting cavity with 2 refractive index distortion points inside.
7. The method of claim 6, wherein the broadband spectrum has a power spectrum G0(t) t is 0, and the 6dB half-width of the characteristic peak is t6dBThen, the reference distance dr and the measured distance d in the optical fiber reflecting cavity should satisfy the following relationship:
8. the method of claim 6, wherein the bandwidth λ s of the broadband light source satisfies the following relationship:
9. the utility model provides a doublestage full optical fiber frequency domain interference range unit which characterized in that includes:
the two-stage cascade frequency domain interference light path is used for generating two paths of detection light and two paths of reference light by the broadband light source through the two-stage cascade frequency domain interference light path;
the spectrometer is used for integrating and recording frequency domain interference signals I (f) of the two paths of detection light and the two paths of reference light;
and the processor is used for obtaining the corresponding power spectrum function G (t) according to the I (f), and selecting the maximum value points meeting the conditions from the maximum value points of the G (t) to obtain the distance value d to be measured.
10. The apparatus of claim 11, wherein the two-stage cascade of frequency domain interference optical paths refers to a first stage and a second stage of frequency domain interference optical paths:
the first-stage frequency domain interference light path comprises a first optical fiber circulator and an optical fiber reflecting cavity; the broadband light source generates light waves which enter the optical fiber reflecting cavity through the first optical fiber circulator; returning the reference light and the corresponding detection light through the optical fiber reflection cavity; 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.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911014491.4A CN110793444B (en) | 2019-10-24 | 2019-10-24 | Two-stage all-fiber frequency domain interference ranging method and device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911014491.4A CN110793444B (en) | 2019-10-24 | 2019-10-24 | Two-stage all-fiber frequency domain interference ranging method and device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN110793444A true CN110793444A (en) | 2020-02-14 |
| CN110793444B CN110793444B (en) | 2021-05-18 |
Family
ID=69441029
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201911014491.4A Active CN110793444B (en) | 2019-10-24 | 2019-10-24 | Two-stage all-fiber frequency domain interference ranging method and device |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN110793444B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114966724A (en) * | 2022-07-27 | 2022-08-30 | 深圳市深视智能科技有限公司 | Distance measuring device and distance measuring method |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20110310395A1 (en) * | 2010-06-18 | 2011-12-22 | National Taiwan University | Three-dimensional optical coherence tomography confocal imaging apparatus |
| CN102645168A (en) * | 2012-05-16 | 2012-08-22 | 中国工程物理研究院流体物理研究所 | System for measuring nanometer micrometric displacement based on full-fiber frequency domain interference |
| CN104197844A (en) * | 2014-09-18 | 2014-12-10 | 中国工程物理研究院流体物理研究所 | All optical fiber frequency domain interference absolute distance measurement method and device |
| CN104501731A (en) * | 2014-12-15 | 2015-04-08 | 哈尔滨工程大学 | Low-coherence multiplexing quasi-distribution optical fiber strain measurement system |
| CN107917669A (en) * | 2017-11-15 | 2018-04-17 | 苏州润桐专利运营有限公司 | A kind of optical fibre displacement sensor demodulation method |
| CN110132138A (en) * | 2019-05-14 | 2019-08-16 | 宁波核芯光电科技有限公司 | Double swept light source range-measurement systems and method based on cascade interferometer |
-
2019
- 2019-10-24 CN CN201911014491.4A patent/CN110793444B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20110310395A1 (en) * | 2010-06-18 | 2011-12-22 | National Taiwan University | Three-dimensional optical coherence tomography confocal imaging apparatus |
| CN102645168A (en) * | 2012-05-16 | 2012-08-22 | 中国工程物理研究院流体物理研究所 | System for measuring nanometer micrometric displacement based on full-fiber frequency domain interference |
| CN104197844A (en) * | 2014-09-18 | 2014-12-10 | 中国工程物理研究院流体物理研究所 | All optical fiber frequency domain interference absolute distance measurement method and device |
| CN104501731A (en) * | 2014-12-15 | 2015-04-08 | 哈尔滨工程大学 | Low-coherence multiplexing quasi-distribution optical fiber strain measurement system |
| CN107917669A (en) * | 2017-11-15 | 2018-04-17 | 苏州润桐专利运营有限公司 | A kind of optical fibre displacement sensor demodulation method |
| CN110132138A (en) * | 2019-05-14 | 2019-08-16 | 宁波核芯光电科技有限公司 | Double swept light source range-measurement systems and method based on cascade interferometer |
Non-Patent Citations (1)
| Title |
|---|
| 刘盛刚 等: "基于白光频域干涉的大台阶高度测量方法", 《强激光与粒子束》 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114966724A (en) * | 2022-07-27 | 2022-08-30 | 深圳市深视智能科技有限公司 | Distance measuring device and distance measuring method |
| CN114966724B (en) * | 2022-07-27 | 2022-12-02 | 深圳市深视智能科技有限公司 | Distance measuring device and distance measuring method |
Also Published As
| Publication number | Publication date |
|---|---|
| CN110793444B (en) | 2021-05-18 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5381229A (en) | Sapphire optical fiber interferometer | |
| Lawson et al. | Specification of optical components using the power spectral density function | |
| US5633712A (en) | Method and apparatus for determining the thickness and index of refraction of a film using low coherence reflectometry and a reference surfaces | |
| Thurner et al. | Fabry-Pérot interferometry for long range displacement sensing | |
| JP2008180736A (en) | Method and apparatus for measuring optical and physical thickness of optically transparent target | |
| CN102778306A (en) | Refractive index and temperature sensor of photonic crystal fiber, manufacturing method and measuring system | |
| CN105388128A (en) | Michelson interferometric optical-fiber hydrogen sensor based on PM-PCF | |
| US5642196A (en) | Method and apparatus for measuring the thickness of a film using low coherence reflectometry | |
| CN110793444B (en) | Two-stage all-fiber frequency domain interference ranging method and device | |
| US7308162B2 (en) | Intrinsic Fabry-Perot optical fiber sensors and their multiplexing | |
| US4820049A (en) | Coating and method for testing plano and spherical wavefront producing optical surfaces and systems having a broad range of reflectivities | |
| CN110530466B (en) | Intensity modulation type liquid level sensing detection method based on double-coreless optical fiber cascade connection | |
| CN112179537A (en) | Fabry-Perot interferometer optical fiber sensor based on optical fiber surface waveguide | |
| US5303033A (en) | Gradient index measuring apparatus | |
| CN109141487B (en) | Distributed optical fiber sensor | |
| CN116026244A (en) | System for measuring lens group lens surface spacing and refractive index | |
| Li et al. | Multipoint displacement measurement based on low intracavity-loss FLRD method | |
| CN110793445A (en) | Multi-channel synchronous absolute distance measuring method and device based on all-fiber frequency domain interference | |
| CN113494890A (en) | Fiber bragg grating strain sensor precision measuring device and method based on FPI interferometer | |
| Imran et al. | Measurement of the group-delay dispersion of femtosecond optics using white-light interferometry | |
| CN112731584A (en) | Core-free optical fiber Michelson structure based on femtosecond laser processing and preparation method | |
| JPH0432336B2 (en) | ||
| Liu et al. | HCPCF-based in-line fiber Fabry-Perot refractometer and high sensitivity signal processing method | |
| CN202710208U (en) | Photonic crystal optical fiber refractive index temperature sensor and measurement system | |
| Lu et al. | Thin-film thickness absolute measurement by differential optic-fiber white light interferometry |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |