CN104215176B - High accuracy optical interval measurement device and method - Google Patents
High accuracy optical interval measurement device and method Download PDFInfo
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- CN104215176B CN104215176B CN201410472652.5A CN201410472652A CN104215176B CN 104215176 B CN104215176 B CN 104215176B CN 201410472652 A CN201410472652 A CN 201410472652A CN 104215176 B CN104215176 B CN 104215176B
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Abstract
Disclosed are a high accuracy optical interval measurement device and a high accuracy optical interval measurement method. The high accuracy optical interval measurement device comprises a short coherent light source, a laser length measurement light source, an illumination indication light source, a first optical fiber coupler, a second optical fiber coupler, a measurement light path, a reference mirror light path, a delayed scanning light path, a wavelength division multiplexer, a first photoelectric detector, a second photoelectric detector, connection optical fibers and an environment sensor. According to the high accuracy optical interval measurement device and the high accuracy optical interval measurement method, a time domain optical coherence chromatographic technique is adopted, a broadband light source and the high accuracy delayed scanning light path are used to achieve noncontact measurement of optical element intervals, a common optical path length measurement technique is used to obtain accurate displacement of the delayed scanning light path, measurement errors are eliminated and measurement accuracy is improved by using an extraction algorithm enveloped with five step phase shift interference fringes and through environment compensation, the internal measurement accuracy in a measurement range can reach the submicron level, and simultaneously measurement can be performed in real time and measurement efficiency is improved during the installation adjustment process of an optical instrument.
Description
Technical field
The present invention relates to field of optical measurements and in particular to a kind of non-contacting based on optical fiber Michelson interference principle
Measurement apparatus and measuring method are measured with lens separation to lens center thickness.
Background technology
In optical field, lens are as the most basic optical element of composition optical system, the processing of its center thickness
Error will directly influence the image quality of whole optical system.During optical instrument is debug, position of optical element error
Larger on the assembling quality impact of whole machine optics, it is also error more rambunctious, particularly in exposure system of photo-etching machine, aerial survey mirror
In head, the assembling process of the high performance precision optical system such as interferometer standard lens, laserresonator, lens centre is spaced all
Very strict control is had to require, the little by little deviation at its lens centre interval all may lead to the deterioration of image quality.How to solve
Certainly the positional precision of optical element is to ensure that the key point of its optical property.
In traditional optical measurement, at present great majority using dial gauge or amesdial etc. carry out contact type measurement or and
The pure optical meanss of the formula that connects measure.The major defect of contact type measurement is the anti-reflection film of easy snag lens surface, measures power
Piece surface is easily made to damage, therefore certainty of measurement is relatively low.And indirect type measurement, so that its precision is reduced because needing reduced parameter.
And, above two method measures all more difficult practical center accurately finding lens, therefore certainty of measurement is not high, is not suitable for
The dress school of high-performance objective.
In the prior art, " optical lens center thickness measuring system and method " is (referring to Chinese patent CN
102435146 A) in, disclose a set of noncontact lens center thickness measuring system based on the confocal method of optics, its measurement letter
Single quick, but its measurement range is little, is limited it is adaptable to list is saturating by minimal wave length in light source and long wavelength's focal length
The measurement of mirror, its precision is restricted by measurement range and spectrogrph optical resolution.
Content of the invention
It is an object of the invention to the certainty of measurement of optical interval and efficiency in raising optical measurement, and provide a kind of base
In the high-precision optical interval measurement apparatus and method of optical fiber Michelson interference principle, using Time Domain Optical coherent tomographic skill
Art, realizes the non-cpntact measurement at optical element interval using wideband light source and high accuracy delaying sweep light path, is swashed by common light path
The precise displacement of flash ranging long technical limit spacing optical delay circuit, using the extraction algorithm of five step phase shift interference fringe envelopes and by ring
Border compensates, and eliminates measurement error, improves certainty of measurement, interval measurement precision can reach submicron order in measurement range, simultaneously
Can realize measuring in real time during optical instrument is debug.
The technical solution of the present invention is specific as follows：
A kind of high-precision optical interval measurement device, for double fiber coupler structures, specifically includes：Short-coherence light source, swash
The long light source of flash ranging, illumination instruction light source, the first fiber coupler, the second fiber coupler, optical path, reference mirror light path,
Delaying sweep light path, wavelength division multiplexer, the first photodetector, the second photodetector, connection optical fiber, environmental sensor.
Short-coherence light source and the second fiber coupler are connected to two ports of the side of the first fiber coupler, swash
The long light source of flash ranging and optical path are connected to two ports of the opposite side of the first fiber coupler, illuminate instruction light source
It is connected with optical path；Reference mirror light path and delaying sweep light path are connected to two of the opposite side of the second fiber coupler
Port, wavelength division multiplexer is connected with a port of the side of the second fiber coupler, and the first and second photodetectors are respectively
It is connected with two output ports of wavelength division multiplexer.
Described short-coherence light source is super-radiance light emitting diode (Superluminescent LED), is wideband light source,
There is the coherence length of very little, the interference signal as device measures light source.
Described laser length measurement light source is distributed feedback laser (Distributed FeedBack Laser), has
Extraordinary monochromaticity, as the long positioned light source of survey of device.
Described illumination instruction light source is laser diode, sends visible ray in order to coordinate the tune of determinand optical axis position
Section.
Described optical path includes four-dimensional adjustment frame, adjustable focus optical fiber amasthenic lens, determinand and installing rack.Measurement light
Road is connected with the first fiber coupler by adjustable focus optical fiber amasthenic lens, and the measuring beam that short-coherence light source sends is through first
Fiber coupler enters the adjustable focus optical fiber amasthenic lens in optical path, and each surface in determinand is reflected, and returns to
The second fiber coupler is entered after first fiber coupler.Installing rack is used for adjusting and fix the position of determinand, four-dimensional adjustment
Frame is fixed to adjustable focus optical fiber amasthenic lens and is pointed to and position adjustments are it is ensured that the optical axis weight of its optical axis and determinand
Close.Adjustable focus optical fiber amasthenic lens is positioned over optical path foremost, can be gone out by adjusting adjustable focus optical fiber amasthenic lens
The focal position of irradiating light beam is it is ensured that the light beam major part that in determinand, each surface reflects returns to adjustable focus optical fiber amasthenic lens
In.
Described reference mirror light path includes an optical fiber retroeflector, by connecting optical fiber and the second fiber coupler phase
Even, the reflected beams on each surface in determinand in optical path are reflected.It is right that the position of optical fiber retroeflector should be located at
Answer the initial position (from the nearest position of fiber optic collimator camera lens) of removable scanning reflection mirror in delaying sweep light path, that is, after optical fiber
Initial position to reflector and scanning reflection mirror removable in delaying sweep light path is aplanatic.
It is mobile flat that described delaying sweep light path includes fiber optic collimator camera lens, removable scanning reflection mirror and Motor drive
Platform.Fiber optic collimator camera lens is positioned over delaying sweep light path foremost, and delaying sweep light path passes through fiber optic collimator camera lens and second
Fiber coupler connection, short coherent measurement light beam and laser length measurement light beam are incided removable after fiber optic collimator camera lens collimation
On scanning reflection mirror and reflect, return in the second fiber coupler.Removable scanning reflection mirror is arranged on a Motor drive and moves
On moving platform, with certain speed uniform motion in measurement process, its position zinformation is existed respectively by laser length measurement light beam
Produced by the reflected beams of reference mirror light path and removable scanning reflection mirror, interference signal measurement obtains.
Described wavelength division multiplexer is 1310/1550nm wavelength division multiplexer, for by the interference signal of two kinds of different wave lengths
Carry out separating, be divided into two-way, respectively enter the first and second photodetectors.
First, second described photodetector is used for receiving short coherent measurement light beam and the ripple of wavelength 1310nm respectively
The interference signal produced by laser length measurement light beam of long 1550nm, and it is connected display with computer.
Described connection optical fiber is single-mode polarization maintaining fiber, it is to avoid the measurement error being caused due to polarization mode dispersion.
Described environmental sensor separately detects temperature under the present circumstances, air pressure, relative humidity and delaying sweep
Inside temperature in light path, is applied to the compensation of refractive index value of calculation in algorithm it is ensured that the precision of interval measurement.
Treat the measuring method at object test light interval using above-mentioned optical interval measurement device, the method includes following step
Suddenly：
1. illumination instruction light source is connected to optical path by optical fiber, light source is opened, is fixed by installing rack
Determinand, adjusts the position of adjustable focus optical fiber amasthenic lens by adjusting four-dimensional adjustment frame, according to each surface reflection in determinand
The luminous point returned, adjust adjustable focus optical fiber amasthenic lens outgoing beam to determinand) center, i.e. the optical axis of determinand
With in optical path measuring beam optical axis coincidence；
2. close illumination instruction light source, 4. the optical fiber of port is replaced illumination instruction and used by connecting the first fiber coupler the
Light source and the connection optical fiber of optical path, open short-coherence light source and laser length measurement light source, adjust the adjustable focus in optical path
Optical fiber amasthenic lens, makes the stiffness of coupling of each surface reflection in determinand as big as possible；
3. the Motor drive mobile platform in described delaying sweep light path is controlled at the uniform velocity to drive removable scanning reflection mirror
Move, the interference signal recording is inputted computer by the first photodetector and the second photodetector respectively；
4. computer carries out data processing, draws the optical interval of determinand：
Carry out the extraction of interference signal using the five step phase shift nonlinear algorithms interfered based on phase shift, calculate each as the following formula
The tangent value of the phase place of sampled point,
Wherein I1、I2、I3、I4、I5It is respectively the light intensity value of five neighbouring sample points,
Using edlen formula, the refractive index of air and group index are modified：
Comparison using optical path and optics group delay in delaying sweep light path draws the optical interval in determinand
Dmea,
In formula, nairWith ng,airRepresent refractive index and the group index of air respectively, they are by wavelength (λ1Or λ2), gas
Warm (the temperature T in delaying sweep light pathrefOr the temperature T in optical pathmea), air pressure p and relative humidity RH determined,
The computing formula of its refractive index is edlen formula：
n15- 1=[8342.13+2406030 (130- σ2)-1+15997(38.9-σ2)-1]×10-8
nt,p,f=nt,p-f(5.7224-0.0457σ2)×10-8
In formula：(n15- 1) be in the air at a normal atmosphere, 15 DEG C refractive index, σ be vacuum in wave number, be
The inverse of wavelength X, unit be μm-1, (nt,p- 1) it is the refractive index being subject to temperature and effects of air pressure in normal air, nt,p,fFor mark
The refractive index that quasi- in the air is affected by temperature, air pressure and water vapor partial pressure, t is temperature DEG C, and p is air pressure Torr, and f divides for steam
Pressure Torr, by nt,p,fRefractive index n can be obtainedairAnd its dispersion relation of wavelength, using the formula of group indexCorresponding group index n can be drawng,air.
Compared with formerly technology, the present invention has following technological merit：
1) the high-precision optical interval measurement apparatus and method based on optical fiber Michelson interference principle proposed by the present invention
Belong to non-contact measurement, contact can be efficiently solved and indirect type measures the shortcoming that optical interval is brought, measure model
Enclose big, measurement efficiency is high, can disposably complete the measurement at multigroup interval in one group of optical system.
2) present invention, using double fiber coupler structures, makes the light path of generation interference signal two light beam be located at same in device
Under environment, eliminate reference path and optical path in single fiber coupler structure and be located at the environment in device and outside device respectively
Influence factor.
3) present invention adopts optical interval measurement signal and the version of the common light path of laser length measurement signal, eliminates removable
It is achieved that the accurate measurement of its shift length, interval measurement precision can reach sub-micro for the errors in position measurement of dynamic scanning reflection mirror
Meter level.
Brief description
Fig. 1 is the high-precision optical interval measurement device total figure based on optical fiber Michelson interference principle of the present invention.
In figure：
1 is short-coherence light source；
2 is laser length measurement light source；
3 is illumination instruction light source；
4 is the first fiber coupler；
5 is the second fiber coupler；
6 is optical path；
601 is four-dimensional adjustment frame；
602 is adjustable focus optical fiber amasthenic lens；
603 is determinand；
604 is installing rack；
7 is reference mirror light path；
701 is optical fiber retroeflector；
8 is delaying sweep light path；
801 is fiber optic collimator camera lens；
802 is removable scanning reflection mirror；
803 is Motor drive mobile platform；
9 is wavelength division multiplexer；
10 is the first photodetector；
11 is the second photodetector；
12 is to connect optical fiber；
13 is environmental sensor.
Specific embodiment
With reference to the accompanying drawings and detailed description the present invention is described in further detail, but this should not be limited with this
Bright protection domain.
As shown in figure 1, the high-precision optical interval measurement device of the present invention mainly comprises the following steps：Short coherent light
Source 1, laser length measurement light source 2, illumination instruction light source 3, the first fiber coupler 4, the second fiber coupler 5, optical path 6,
Reference mirror light path 7, delaying sweep light path 8, wavelength division multiplexer 9, the first photodetector 10, the second photodetector 11, connection
Optical fiber 12, environmental sensor 13.
Short-coherence light source 1 and the second fiber coupler 5 are connected to two ends of the side of the first fiber coupler 4
Mouth, laser length measurement light source 2 and optical path 6 are connected to two ports of the opposite side of the first fiber coupler 4, and illumination refers to
Show and be connected with optical path 6 with light source 3；Reference mirror light path 7 and delaying sweep light path 8 are connected to the second fiber coupler 5
Opposite side two ports, wavelength division multiplexer 9 is connected with a port of the side of the second fiber coupler 5, the first photoelectricity
Detector and the second photodetector 10,11 are connected with two output ports of wavelength division multiplexer 9 respectively.
Described short-coherence light source 1 is super-radiance light emitting diode (SLED), minimum output power 15mW, central wavelength lambda1
=1310nm, half-peak band width Δ λ=50nm, coherence length is about 15 μm.
Described laser length measurement light source 2 is distributed feedback laser, central wavelength lambda2=1550nm, -3dB live width is
2MHz, output is up to 30mW.
Described illumination instruction light source 3 is laser diode, central wavelength lambda=655nm, half-peak band width δ λ=
30nm, output is 0.676mW.
The measuring beam that short-coherence light source 1 sends is coupled to and is connected with optical path 6 by the first described fiber coupler 4
Connection optical fiber 12 in, and make the reflected beams on each surface in determinand 603 be coupled to the company being connected with the second fiber coupler 5
Connect in optical fiber 12；The laser length measurement light beam coupling that laser length measurement light source 2 sends can be connected to the second fiber coupler 5 simultaneously
Connection optical fiber 12 in.
The second described fiber coupler 5 is respectively by the measuring beam reflecting through 603 kinds of each surfaces of determinand and laser
Survey long light beam, be beamed into two-beam respectively and respectively enter reference mirror light path 7 and delaying sweep light path 8, simultaneously also by reference mirror light
The light beam coupling that road 7 reflects with delaying sweep light path 8 is in the connection optical fiber 12 being connected with wavelength division multiplexer 9.
Described optical path 6 includes four-dimensional adjustment frame 601, adjustable focus optical fiber amasthenic lens 602, determinand 603 and peace
Shelve 604.Optical path 6 is connected with the first fiber coupler 4 by adjustable focus optical fiber amasthenic lens 602, short-coherence light source 1
The measuring beam going out enters the adjustable focus optical fiber amasthenic lens 602 in optical path 6 through the first fiber coupler 4, through treating
Survey each surface in thing 603 to be reflected, after returning to the first fiber coupler 4, enter the second fiber coupler 5.Installing rack 604 is used
In the position adjusting and fixing determinand 603, four-dimensional adjustment frame 601 is fixed to adjustable focus optical fiber amasthenic lens 602 and goes forward side by side
Row points to and position adjustments are it is ensured that the optical axis coincidence of optical axis and the determinand 603 of focusing optical fiber amasthenic lens 602.Adjustable focus light
Fine amasthenic lens 602 is positioned over optical path 6 foremost, by adjusting adjustable focus optical fiber amasthenic lens 602 outgoing beam
Focal position is it is ensured that the first photodetector 10 can obtain a very strong interference signal.
Described reference mirror light path 7 includes an optical fiber retroeflector 701, by connecting optical fiber 12 and the second optical fiber coupling
Clutch 5 is connected, and the reflected beams on each surface in determinand 603 in optical path 6 are reflected.Optical fiber retroeflector 701
Position should be located at the initial position of removable scanning reflection mirror 802 in corresponding delaying sweep light path 8 (from fiber optic collimator camera lens
801 nearest positions), may move the initial of scanning reflection mirror 802 in optical fiber retroeflector 701 and delaying sweep light path 8
Position is aplanatic.
Described delaying sweep light path 8 includes fiber optic collimator camera lens 801, removable scanning reflection mirror 802 and Motor drive
Mobile platform 803.Fiber optic collimator camera lens 801 is positioned over delaying sweep light path 8 foremost, and delaying sweep light path 8 passes through optical fiber
Collimation camera lens 801 is connected with the second fiber coupler 5, and short coherent measurement light beam and laser length measurement light beam pass through fiber optic collimator camera lens
Incide on removable scanning reflection mirror 802 after 801 collimations and reflect, return in the second fiber coupler 5.Removable scanning is anti-
Penetrate mirror 802 to be arranged on a Motor drive mobile platform 803, with certain speed uniform motion, its position in measurement process
Mobile message is produced in the reflected beams of reference mirror light path 7 and removable scanning reflection mirror 802 respectively by laser length measurement light beam
Raw interference signal measurement obtains.
Described wavelength division multiplexer 9 is 1310/1550nm wavelength division multiplexer, for by the interference signal of two kinds of different wave lengths
Carry out separating, be divided into two-way, respectively enter the first photodetector 10 and the second photodetector 11.
The first described photodetector 10 and the second photodetector 11 are two photodiodes, spectral response range
For 950～1650nm, receive the short coherent measurement light beam of wavelength 1310nm and the laser length measurement light beam of wavelength 1550nm respectively
Produced interference signal, and it is connected display with computer.
Described connection optical fiber 12 is single-mode polarization maintaining fiber, and cutoff wavelength is 1260nm.
Described environmental sensor 13 separately detects temperature under the present circumstances, air pressure, relative humidity and postpones to sweep
Retouch the inside temperature in light path 8, be applied to the compensation of refractive index value of calculation in algorithm it is ensured that the precision of interval measurement.
The short coherent measurement light beam that in device, short-coherence light source 1 sends enters into measurement light through the first fiber coupler 4
In road 6, the reflected light on each two surfaces in determinand 603, it is divided into two bundles through the second fiber coupler 5, light beam enters
Reference mirror light path 7, another light beam enters in delaying sweep light path 8.In delaying sweep light path 8, light beam is through fiber optic collimator mirror
Reflected by removable scanning reflection mirror 802 after 801.Each the reflected beams return in the second fiber coupler 5, enter wavelength-division
Multiplexer 9.Now, the reflected beams of removable scanning reflection mirror 802 and optical fiber retroeflector 701 in reference mirror light path 7
The reflected beams interfere generation interference signal, through algorithm process after being detected by the first photodetector 10, obtain interfering letter
Number intensity distributions.Meanwhile, the laser length measurement light beam that laser length measurement light source 2 sends, respectively through the first fiber coupler and
It is divided into two bundles after two fiber couplers 4,5, respectively enter reference mirror light path 7 and delaying sweep light path 8, by the second photodetection
Device 11 obtains interference signal produced by the reflected beams in two light paths, because it produces interference signal with short coherent measurement light beam
Sample frequency identical, you can produce the removable scanning corresponding to interference signal extreme value place to obtain short coherent measurement light beam
The relative position of reflecting mirror 802.Removable scanning reflection mirror 802 corresponding to maximum position occurs respectively by interference signal
The difference of the position in delaying sweep light path 8, you can to calculate the optical interval of determinand 603.
During systematic survey, the high-precision optical interval measurement device of the present invention and measuring method, including following step
Suddenly：
1. illumination instruction light source 3 is passed through connection optical fiber 12 and connect the adjustable focus optical fiber focus lamp to optical path 6
602, light source is opened, determinand 603 is fixed by installing rack 604, adjust adjustable focus light by adjusting four-dimensional adjustment frame 601
The position of fine amasthenic lens 602, the luminous point being reflected according to surface each in determinand 603, adjust adjustable focus optical fiber focus lamp
602 outgoing beam to determinand 603 center, i.e. the optical axis of determinand 603 and adjustable focus optical fiber amasthenic lens 602
The optical axis coincidence of outgoing measuring beam；
2. close illumination instruction light source 3, the connection optical fiber 12 connecting the first fiber coupler 4 the 4. port is replaced photograph
The bright instruction connection optical fiber 12 of light source 3 and adjustable focus optical fiber amasthenic lens 602 in optical path 6, opens short-coherence light source 1 He
Laser length measurement light source 2, adjusts the adjustable focus optical fiber amasthenic lens 602 of optical path 6, makes each surface reflection in determinand 603
Stiffness of coupling as big as possible；
3. the Motor drive mobile platform 803 in delaying sweep light path 8 is controlled at the uniform velocity to drive removable scanning reflection mirror 802
Mobile, the first photodetector 10 and the second photodetector 11 receive respectively wavelength 1310nm short coherent measurement light beam and
The input computer of interference signal produced by laser length measurement light beam of wavelength 1550nm；
4. described computer carries out, to interference signal, the optical interval that data processing draws determinand 603：
Whole device is actually with optical path 6 and relatively being surveyed of optics group delay in delaying sweep light path 8
Amount, optics group delay is defined as ngD, wherein ngFor group index, under setted wavelength, it is defined asD is physical distance.Removable scanning reflection mirror in systematic survey, in delaying sweep light path 8
802 carry out uniform rectilinear scanning along the direction parallel to optical axis with certain speed on electrically driven (operated) mobile platform, meanwhile, with
The computer that first photodetector 10 is connected with the second photodetector 11 constantly gathers and processes acquisition in scanning process
Wavelength 1310nm short coherent measurement light beam and interference signal produced by wavelength 1550nm laser length measurement light beam, using based on shifting
Five step phase shift nonlinear algorithms of interference carry out the extraction of interference signal, have good precision and weight under actual noise grade
Renaturation.In interference signal, the modulation degree of certain given sampled point can be defined by following formula：
Wherein I1、I2、I3、I4、I5It is respectively the light intensity value of five neighbouring sample points, the phase place of each sampled point can be calculated by following formula
Value,
Make the phase-shift phase in phase shift algorithmWherein v is removable scanning reflection in delaying sweep light path 8
The translational speed of mirror 802, fsFor system sampling frequency, it is also the sample frequency of laser length measurement beam interference signal simultaneously, v can be obtained
=30mm s-1, fs=180kHz.Then, when scanning reflection mirror 802 removable in delaying sweep light path 8 moves to a certain position
Put so as to when in the reflected beams and reference mirror light path 7, the reflected beams group delay difference of optical fiber retroeflector 701 is zero, interfere
Signal is peak value；Make its reflected beams and optical fiber retroreflection in reference mirror light path 7 when removable scanning reflection mirror 802 moves to
The reflected beams group delay difference of device 701 is ngDuring the position of D, an interference peak signal (wherein n will be obtained againgFor determinand
In 603 between each surface medium group index, D is the optical interval in determinand 603 between two surfaces).If determinand
603 include multigroup optical interval, then multiple peak values will occur, respectively in the first photodetector 10 during single pass
The position of removable scanning reflection mirror 802, as determinand in optical path 6 in delaying sweep light path 8 corresponding to individual peak value
Each optical mirror plane vertex position in 603.Hereinafter it is further described：Removable scanning reflection mirror 802 relative
Position ZrefCan be defined by below equation：WhereinFor in the second photodetector 11 to wavelength X2=
The laser length measurement beam interference signal measurement of 1550nm the phase value being obtained by algorithm process.Wavelength X1Measurement interfere letter
Number and wavelength X2Laser length measurement interference signal be with identical sample frequency fsObtain, therefore two in measurement interference signal
The distance between peak value is relative distance D of removable scanning reflection mirror 802 movement in delaying sweep light path 8ref, also just corresponding
The optical interval D of optical element in determinand 603 in the optical path 6mea.Can be represented with following two formula：
ng,air(λ1,Tref,p,RH)·Dref=ng,air(λ1,Tmea,p,RH)·Dmea(2)
In formula it is assumed that in optical path 6 medium of determinand 603 optical interval be air, otherwise this right of formula
ng,airShould be replaced with the group index of this medium.
In formula, nairWith ng,airRepresent refractive index and the group index of air respectively, they are by wavelength (λ1Or λ2), gas
Warm (the temperature T in delaying sweep light path 8refOr the temperature T in optical path 6mea), air pressure p and relative humidity RH determined
Fixed, here it is the reason in device, environmental sensor 13 exists.The computing formula of its refractive index is edlen formula：
n15- 1=[8342.13+2406030 (130- σ2)-1+15997(38.9-σ2)-1]×10-8
nt,p,f=nt,p-f(5.7224-0.0457σ2)×10-8
In formula：(n15- 1) be in the air at a normal atmosphere, 15 DEG C refractive index, σ be vacuum in wave number, be
The inverse of wavelength X, unit be μm-1, (nt,p- 1) it is the refractive index being subject to temperature and effects of air pressure in normal air, nt,p,fFor mark
The refractive index that quasi- in the air is affected by temperature, air pressure and water vapor partial pressure, t is temperature DEG C, and p is air pressure Torr, and f divides for steam
Pressure Torr.By nt,p,fRefractive index n can be obtainedairAnd its dispersion relation of wavelength, using the formula of group indexCorresponding group index n can be drawng,air.
So the optical interval D determinand 603 can be drawn from formula (1), (2)meaFormula：
Optical interval D from this formula it can be seen that in determinand 603meaIt is proportional to laser instrument in laser length measurement light source 2
Wavelength X2Divided by wavelength X2Under air refraction nair(λ2,Tref, p, RH), therefore need before measuring to this wavelength and
Its time stability is calibrated.Using a heat-staple gauged distance block, (thermal coefficient of expansion is about 0.05 × 10-6K-1) come
Measure calibration, if DexactFor the accurate distance of this gauged distance block, then the precision laser wavelength after calibrating isLaser wavelength lambda is assumed in this formula2It is in close proximity to (several nanometers) accurate wavelength X2,exact.
Claims (8)
1. a kind of high-precision optical interval measurement device is it is characterised in that for double fiber coupler structures, including short-coherence light source
(1), laser length measurement light source (2), illumination instruction light source (3), the first fiber coupler (4), the second fiber coupler (5), survey
Amount light path (6), reference mirror light path (7), delaying sweep light path (8), wavelength division multiplexer (9), the first photodetector (10), second
Photodetector (11), connection optical fiber (12) and environmental sensor (13), described optical path (6) includes four-dimensional adjustment frame
(601), adjustable focus optical fiber amasthenic lens (602), determinand (603) and installing rack (604), described adjustable focus optical fiber focus lamp
Head (602) is placed in four-dimensional adjustment frame (601), and described determinand (603) is placed on installing rack (604), described reference mirror
Light path (7) includes an optical fiber retroeflector (701), and described delaying sweep light path (8) includes fiber optic collimator camera lens
(801), may move scanning reflection mirror (802) and Motor drive mobile platform (803), described removable scanning reflection mirror
(802) it is placed on described Motor drive mobile platform (803), the position relationship of above-mentioned component is as follows：
1. the outfan of described short-coherence light source (1) passes through to connect optical fiber (12) and described first fiber coupler (4) the
Port is connected, and the outfan of described laser length measurement light source (2) passes through to connect the of optical fiber (12) and the first fiber coupler (4)
3. port be connected, adjustable focus optical fiber amasthenic lens (602) in described optical path (6) pass through connect optical fiber (12) with described
The first fiber coupler (4) the 4. port be connected, before measurement starts will first to described optical path (6) in measurement light
Bundle is aligned with the optical axis of determinand (603), and now described illumination instruction is passed through to connect optical fiber (12) and institute with light source (3)
Adjustable focus optical fiber amasthenic lens (602) in the optical path (6) stated are connected；
The of described the first fiber coupler (4) 2. port through connecting the of optical fiber (12) and the second fiber coupler (5) 1.
Port is connected, the second fiber coupler (5) the 3. port through connecting optical fiber (12) and described optical fiber retroeflector (701)
It is connected, the other end of the 4. connection optical fiber (12) of port of the second fiber coupler (5) is placed in described delaying sweep light path
(8) front focus of the fiber optic collimator camera lens (801) in, the second fiber coupler (5) the 2. port through connect optical fiber (12) with
The input of described wavelength division multiplexer (9) is connected, two outfans of this wavelength division multiplexer (9) respectively with the first described light
Electric explorer (10) is connected with the second photodetector (11), described the first photodetector (10) and the second photodetector
(11) outfan is connected with the input of computer.
2. high-precision optical interval measurement device according to claim 1 is it is characterised in that described short-coherence light source (1)
For super-radiance light emitting diode, central wavelength lambdaSLED=1310nm, coherence length is 15 μm.
3. high-precision optical interval measurement device according to claim 1 is it is characterised in that described laser length measurement light source
(2) it is distributed feedback laser, central wavelength lambdaLASER=1550nm, -3dB live width is 2MHz.
4. high-precision optical interval measurement device according to claim 1 is it is characterised in that described illumination instruction is used up
Source (3) is laser diode, central wavelength lambda=655nm.
5. high-precision optical interval measurement device according to claim 1 is it is characterised in that described wavelength division multiplexer (9)
For 1310/1550nm wavelength division multiplexer.
6. high-precision optical interval measurement device according to claim 1 is it is characterised in that described the first photodetection
The spectral response range of device (10) and the second photodetector (11) is 950～1650nm, receives the short of wavelength 1310nm respectively
The interference signal produced by laser length measurement light beam of coherent measurement light beam and wavelength 1550nm.
7. high-precision optical interval measurement device according to claim 1 is it is characterised in that described connection optical fiber (12)
For single-mode polarization maintaining fiber, cutoff wavelength is 1260nm.
8. treat the measuring method at object test light interval using the optical interval measurement device described in claim 1, its feature exists
Comprise the following steps in the method：
1. connection optical fiber (12) is passed through in illumination instruction light source (3) to connect to optical path (6), light source is opened, passes through
The fixing determinand (603) of installing rack (604), adjusts adjustable focus optical fiber amasthenic lens (602) by adjusting four-dimensional adjustment frame (601)
Position, the luminous point being reflected according to each surface in determinand (603), adjust the going out of adjustable focus optical fiber amasthenic lens (602)
Irradiating light beam to determinand (603) center, that is, in the optical axis of determinand (603) and optical path (6) measuring beam
Optical axis coincidence；
2. close illumination instruction with light source (3), will connect connection optical fiber (12) replacement of the first fiber coupler (4) the 4. port
The illumination instruction connection optical fiber (12) of light source (3) and optical path (6), opens short-coherence light source (1) and laser length measurement light source
(2), adjust adjustable focus optical fiber amasthenic lens (602) in optical path (6), make each surface reflection in determinand (603)
Stiffness of coupling is as big as possible；
3. the Motor drive mobile platform (803) in described delaying sweep light path (8) is controlled at the uniform velocity to drive removable scanning anti-
Penetrate mirror (802) mobile, the interference signal recording is inputted by the first photodetector (10) and the second photodetector (11) respectively
Computer；
4. computer carries out data processing, draws the optical interval of determinand (603)：
Carry out the extraction of interference signal using the five step phase shift nonlinear algorithms interfered based on phase shift, calculate each sampling as the following formula
The tangent value of the phase place of point,
Wherein I1、I2、I3、I4、I5It is respectively the light intensity value of five neighbouring sample points,
Using edlen formula, the refractive index of air and group index are modified：
n15- 1=[8342.13+2406030 (130- σ2)-1+15997(38.9-σ2)-1]×10-8,
nt,p,f=nt,p-f(5.7224-0.0457σ2)×10-8
Comparison using optical path (6) and optics group delay in delaying sweep light path (8) draws the light in determinand (603)
Learn interval Dmea,
In formula, DrefFor the distance between two peak values in measurement interference signal, i.e. removable scanning in delaying sweep light path (8)
The relative distance of reflecting mirror (802) movement, Zref,1And Zref,2Respectively in the first photodetector (10) during single pass
The relative position of removable scanning reflection mirror (802) in corresponding delaying sweep light path (8) during each peak value occurs,With
For in the second photodetector (11) to wavelength X2The laser length measurement beam interference signal measurement of=1550nm simultaneously passes through at algorithm
Manage the phase value obtaining, it corresponds respectively to relative position Z of removable scanning reflection mirror (802)ref,1And Zref,2, nairWith
ng,airRepresent refractive index and the group index of air respectively, they are by wavelength X1Or λ2, temperature, that is, in delaying sweep light path
Temperature TrefOr the temperature T in optical pathmea, air pressure p and relative humidity RH determined, the computing formula of its refractive index is
Edlen formula：
n15- 1=[8342.13+2406030 (130- σ2)-1+15997(38.9-σ2)-1]×10-8
nt,p,f=nt,p-f(5.7224-0.0457σ2)×10-8
In formula：(n15- 1) be in the air at a normal atmosphere, 15 DEG C refractive index, σ be vacuum in wave number, be wavelength
The inverse of λ, unit be μm-1, (nt,p- 1) it is the refractive index being subject to temperature and effects of air pressure in normal air, nt,p,fFor standard null
The refractive index being affected by temperature, air pressure and water vapor partial pressure in gas, t is temperature DEG C, and p is air pressure Torr, and f is water vapor partial pressure
Torr, by nt,p,fRefractive index n can be obtainedairAnd its dispersion relation of wavelength, using the formula of group indexCorresponding group index n can be drawng,air.
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