CN103837077A - Composite wave interferometry ranging distance system with two femtosecond laser frequency combs - Google Patents
Composite wave interferometry ranging distance system with two femtosecond laser frequency combs Download PDFInfo
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Abstract
The invention relates to a composite wave interferometry ranging distance system with two femtosecond laser frequency combs. The composite wave interferometry ranging distance system is characterized in that a first femtosecond laser frequency comb emits an optical pulse to a first spectroscope, the optical pulse reflected by the first spectroscope is transmitted to a first corner reflector, and the optical pulse reflected by the first corner reflector is transmitted to a second spectroscope through the first spectroscope. The optical pulse transmitted by the first spectroscope is transmitted to a second corner reflector, and the optical pulse reflected by the second corner reflector is reflected to the second spectroscope through the first spectroscope. A second femtosecond laser frequency comb emits an optical pulse to the second spectroscope, the optical pulse transmitted by the second spectroscope and an optical pulse emitted by a Michelson interference system are mixed and transmitted to a third spectroscope, the optical pulse transmitted by the third spectroscope is received by a first photoelectric detector in a detection mode through a first narrow-band band-pass filter, and the optical pulse reflected by the third spectroscope is received by a second photoelectric detector in a detection mode through a second narrow-band band-pass filter. The first photoelectric detector and the second photoelectric detector are connected with an A/ D converter connected with a signal processing unit through a corresponding data interface to process the received signal to obtain the required distance measuring value.
Description
Technical field
The present invention relates to a kind of laser distance measuring system, particularly about a kind of two femtosecond laser frequency comb synthesis wave to interfere range measurement systems that are applicable to absolute distance measurement.
Background technology
Traditional laser interferometry is a kind of range observation mode of increment type, has the non-fuzzy distance of 1/2nd wavelength.When tested distance be greater than non-fuzzy apart from time, need between baseline and target object, set up guide rail, in measuring process, target object need to move continuously and then complete fringe count along guide rail, realizes range observation in a big way.Laser absolute distance measurement (without guide rail range observation) is the method for a kind of direct measurement baseline to distance between target object, there is applied widely, simple operation and other advantages with respect to the former, therefore it has very strong application demand and prospect in industry and space industry, in the big machinery change systems such as high-speed railway, large aircraft, nuclear power and wind-powered electricity generation, the geometric sense of high-accuracy large-scale is accurately measured on the one hand; For realizing high precision satellites formation, also need wide range, high-precision absolute distance measurement technology as guarantee on the other hand.In recent years, the appearance of femtosecond laser frequency comb has brought revolutionary breakthrough to laser absolute distance measurement.
Femtosecond laser frequency comb refers to the repetition frequency (f of femtosecond pulse laser
rep, be called for short repetition) and phase deviation frequency (f
ceo) with frequency reference source locking after device, the laser that it sends is made up of a series of equally spaced ultrashort laser pulses (pulsewidth is some femtoseconds) in time domain, on corresponding frequency domain, there are a series of equally spaced discrete light spectral lines, the frequency interval of adjacent spectrum line equals the repetition of femto-second laser, and the spectral range that these spectrum lines cover is tens nanometer.In existing femtosecond laser frequency comb range measurement system, range measurement system that poor femtosecond laser frequency tree structure builds that two of employings that Unite States Standard (USS) Weights and Measures Bureau (NIST) proposes that comparatively conventional is have small repetition, by the pulse of one of them femtosecond laser frequency comb, for reference and measurement, the pulse of another femtosecond laser frequency comb is for sampling.In measuring process, sampling pulse and reference pulse and ranging pulse generating period overlapping, then extract range information from overlapping signal.This measuring method is divided into bigness scale and accurate measurement two steps: bigness scale is that the femtosecond pulse flight time information by extracting from overlapping pulse signal obtains, and generally can realize the measuring accuracy of several microns; Accurate measurement is by the result of repeatedly bigness scale is averaged, precision is brought up in quarter-wave, thereby determine the integer level time (being commonly called as " several greatly " of interferometric phase) of interference fringe, then according to the interferometric phase extracting, tested distance is refined, realize high-acruracy survey.But it is not high enough to realize very high measuring speed precision when the problem of this method is only bigness scale, and need be undertaken by the method that repeatedly bigness scale is averaged during to accurate measurement transition in bigness scale, greatly reduce the speed of range observation.
Summary of the invention
For the problems referred to above, the object of this invention is to provide a kind of two femtosecond laser frequency comb synthesis wave to interfere range measurement system, it is to utilize the synthetic wavelength of dual wavelength formation as bridge, bigness scale and the interferometric phase of two femtosecond laser frequency combs are directly linked up, realized the direct transition of bigness scale to accurate measurement, thereby avoid repeatedly measuring on average, realize quick high accuracy and measure.
For achieving the above object, the present invention takes following technical scheme: a kind of two femtosecond laser frequency comb synthesis wave to interfere range measurement systems, is characterized in that: it comprises the first femtosecond laser frequency comb, the second femtosecond laser frequency comb, Michelson interference system, the second spectroscope, the 3rd spectroscope, the first narrow band filter, the second narrow band filter, the first photodetector, the second photodetector, A/D converter and signal processing unit; Wherein, described Michelson interference system comprises the first spectroscope, the first corner reflector and the second corner reflector; Described the first femtosecond laser frequency is combed as measuring-signal source, send light pulse to described the first spectroscope, light pulse through described the first spectroscope reflection is transmitted into described the first corner reflector, is transmitted to described the second spectroscope again through the light pulse of described the first corner reflector reflection through described the first spectroscope; Be transmitted into described the second corner reflector through the light pulse of described the first spectroscope transmission, after described the second corner reflector reflection, reflex to described the second spectroscope through described the first spectroscope again; Described the second femtosecond laser frequency is combed as oscillation signals according source, send light pulse to described the second spectroscope, through the light pulse of described the second spectroscope transmission with mix through the light pulse of described Michelson interference system outgoing, mixed light impulse ejection is to described the 3rd spectroscope; Light pulse through described the 3rd spectroscope transmission is surveyed and is received by described the first photodetector after described the first narrow band filter; Light pulse through described the 3rd spectroscope reflection is surveyed and is received by described the second photodetector after described the second narrow band filter; The output terminal of described the first photodetector and the second photodetector is connected respectively to the input end of described A/D converter, and the output terminal of described A/D converter is connected to described signal processing unit by corresponding data interface the signal of reception is processed and obtained required measuring distance value.
The spectral distribution of described the first femtosecond laser frequency comb and the second femtosecond laser frequency comb must have larger width, and must have larger overlapping region, and this overlapping region accounts for the over half of the two spectral width own.
The centre wavelength of described the first narrow band filter and the second narrow band filter is respectively λ
1and λ
2, λ
1and λ
2must be in described larger overlapping region, and λ
1and λ
2choose and need to meet following two conditions simultaneously: 1) choose according to bigness scale precision, make bigness scale precision be better than λ
s/ 4, λ
s=λ
1λ
2/ (λ
2-λ
1), be λ
1and λ
2composite wave wavelength; 2) choose according to interferometric phase measuring accuracy θ, make by composite wave λ
sthe precision of range finding is better than λ
1/ 4 or λ
2/ 4, wherein, composite wave λ
sthe precision of range finding is λ
s/ 2 ﹒ (θ/360).
Described the first narrow band filter and the second narrow band filter all adopt Fiber Bragg Grating FBG.
The present invention is owing to taking above technical scheme, it has the following advantages: 1, the present invention selects the centre wavelength of two femtosecond laser frequency combs by two narrow band filters, therefore through after two narrow band filters, Femtosecond Optical Pulses is broadening in time domain, sampling pulse can increase counting of sampling when reference and ranging pulse are sampled, and improves signal quality; In addition, by the centre wavelength of different narrow band filters is set, can obtain suitable composite wave as bridge, realize the direct transition (without average) of bigness scale to accurate measurement.2, the present invention utilizes the synthetic wavelength of dual wavelength formation as bridge, bigness scale and the interferometric phase of two femtosecond laser frequency combs are directly linked up, realized the direct transition of bigness scale to accurate measurement, thereby avoid repeatedly measuring average, known by the embodiment of the present invention, adopt the present invention not sacrificing under the condition of measuring speed, directly bigness scale (precision of several microns) is transitioned into accurate measurement (nano level precision), effectively guaranteed high measurement speed and high measurement accuracy.The present invention can be widely used in laser absolute distance measurement.
Accompanying drawing explanation
Below in conjunction with accompanying drawing, the present invention is carried out to detailed describing.But only the providing in order to understand better the present invention of accompanying drawing is provided, they not should be understood to limitation of the present invention.
Fig. 1 is the light path schematic diagram of the two femtosecond laser frequency comb of the present invention synthesis wave to interfere range measurement system;
Fig. 2 is light pulse schematic diagram of the present invention, and black is the first femtosecond laser frequency comb FLFC
1the light pulse of sending, grey is the second femtosecond laser frequency comb FLFC
2the light pulse of sending;
Fig. 3 is normalization spectral intensity schematic diagram of the present invention, wherein, (a) is the first femtosecond laser frequency comb FLFC
1spectral distribution, (b) be the second femtosecond laser frequency comb FLFC
2spectral distribution, be (c) through the first narrow band filter BPF
1rear center's wavelength is λ
1narrow-band spectrum, be (d) through the second narrow band filter BPF
2rear center's wavelength is λ
2narrow-band spectrum;
Fig. 4 is light pulse mixing schematic diagram of the present invention, and in lastrow, the hollow stick of fine line represents through the first corner reflector CR
1the light pulse of returning, the solid stick of heavy line represents through the second corner reflector CR
2the light pulse of returning, the hollow stick of heavy line of next line represents the second femtosecond laser frequency comb FLFC
2the light pulse of sending, empty wire frame representation optical pulse overlap position.
Embodiment
Below in conjunction with drawings and Examples, the present invention is described in detail.
As shown in Figure 1, of the present invention pair of femtosecond laser frequency comb synthesis wave to interfere range measurement system comprises the first femtosecond laser frequency comb FLFC
1, the second femtosecond laser frequency comb FLFC
2, Michelson interference system, the second spectroscope BS
2, the 3rd spectroscope BS
3, the first narrow band filter BPF
1, the second narrow band filter BPF
2, the first photoelectric detector PD
1, the second photoelectric detector PD
2, A/D converter 1 and signal processing unit 2; Wherein, Michelson interference system comprises the first spectroscope BS
1, the first corner reflector CR
1with the second corner reflector CR
2;
The first femtosecond laser frequency comb FLFC
1as measuring-signal source, send the first spectroscope BS of light pulse to Michelson interference system
1, through the first spectroscope BS
1the light pulse of reflection is transmitted into the first corner reflector CR
1, through the first corner reflector CR
1the light pulse of reflection is again through the first spectroscope BS
1be transmitted to the second spectroscope BS
2; Through the first spectroscope BS
1the light pulse of transmission is transmitted into the second corner reflector CR
2, through the second corner reflector CR
2after reflection again through the first spectroscope BS
1reflex to the second spectroscope BS
2; The second femtosecond laser frequency comb FLFC
2as oscillation signals according source, send light pulse to the second spectroscope BS
2, through the second spectroscope BS
2the light pulse of transmission with mix through the light pulse of Michelson interference system outgoing, mixed light impulse ejection to the three spectroscope BS
3; Through the 3rd spectroscope BS
3the light pulse of transmission is through the first narrow band filter BPF
1afterwards by the first photoelectric detector PD
1survey and receive; Through the 3rd spectroscope BS
3the light pulse of reflection is through the second narrow band filter BPF
2afterwards by the second photoelectric detector PD
2survey and receive.The first photoelectric detector PD
1with the second photoelectric detector PD
2output terminal be connected respectively to the input end of A/D converter 1, the output terminal of A/D converter 1 is connected to signal processing unit 2 by corresponding data interface the signal of reception is processed and obtained required measuring distance value L.
In a preferred embodiment, the first femtosecond laser frequency comb FLFC
1with the second femtosecond laser frequency comb FLFC
2the repetition of existing commercial optical fiber femtosecond laser and phase deviation Frequency Locking can be realized to atomic clock respectively, also can directly adopt existing commercial femtosecond laser frequency comb, both repetitions are in tens of MHz or hundred MHz magnitudes.It is poor that two femtosecond laser frequencies comb has small repetition, and their repetition periods (inverse of repetition) in time domain are designated as respectively T
r1and T
r2, the poor Δ T that is designated as of repetition period
r(as shown in Figure 2), two poor settings of femtosecond laser frequency comb repetition should meet Δ T
rbe less than two femtosecond laser frequency pulse time domain width.
In a preferred embodiment, as Fig. 3 (a) with (b), the first femtosecond laser frequency comb FLFC
1with the second femtosecond laser frequency comb FLFC
2spectral distribution must there is larger width (more than being conventionally chosen for 20nm, existing commercial femtosecond laser frequency comb can reach), and (overlapping region accounts for the over half of the two spectral width own must larger overlapping region, make like this selection of the centre wavelength of narrow band filter just have larger leeway), the first narrow band filter BPF
1with the second narrow band filter BPF
2centre wavelength be respectively λ
1and λ
2, light pulse is passed through these two narrow band filters spectral distribution afterwards as (c) in Fig. 3 with (d), λ
1and λ
2must be in above-mentioned larger overlapping region, and λ
1and λ
2choose and should meet two conditions simultaneously: 1) choose according to bigness scale precision (general several microns), make bigness scale precision be better than λ
s/ 4, wherein, λ
s=λ
1λ
2/ (λ
2-λ
1), be λ
1and λ
2composite wave wavelength; 2) choose according to interferometric phase measuring accuracy θ (being generally better than 0.5 °), make by composite wave λ
sprecision (the λ of range finding
s/ 2 ﹒ (θ/360)) be better than λ
1/ 4 or λ
2/ 4.Only have when meeting above-mentioned two conditions simultaneously and can guaranteeing bigness scale corresponding synthesis wave to interfere " several greatly " (interference fringe integer level time) fixed, and interfere corresponding " several greatly " to fix single wavelength according to the result of composite wave range finding.
In a preferred embodiment, two narrow band filters all can adopt Fiber Bragg Grating FBG, select the effect of narrow band filter to have 2 points: the one, after narrow band filter, femtosecond pulse is meeting broadening in time domain, current sampling pulse can increase counting of sampling when reference and ranging pulse are sampled, and improves signal quality; The 2nd, by the centre wavelength of different narrow band filters is set, can obtain suitable composite wave as bridge, realize the direct transition (without average) of bigness scale to accurate measurement.
Further illustrate the concrete measuring principle of laser distance measuring system of the present invention below by specific embodiment:
As shown in Fig. 1～4, the present invention is by the first corner reflector CR
1about the first spectroscope BS
1mirror Symmetry position be defined as in baseline BL(Fig. 1 shown in dot-and-dash line), the second corner reflector CR
2be measuring distance value to the distance L of baseline BL.In the time that L is greater than zero, from the first corner reflector CR
1with the second corner reflector CR
2τ is at certain time intervals deposited in the light pulse of returning, simultaneously will be through the first corner reflector CR
1the light pulse of returning is defined as reference arm light pulse (the hollow stick of fine line as shown in Figure 4), will be through the second corner reflector CR
2the light pulse of returning is defined as gage beam light pulse (the solid stick of heavy line as shown in Figure 4), will be through the second femtosecond laser frequency comb FLFC
2the light pulse of sending is defined as local oscillation light pulse (the hollow stick of heavy line as shown in Figure 4).
Through the reference arm light pulse of Michelson interference system outgoing and gage beam light pulse with through the second spectroscope BS
2the local oscillation light pulse of transmission mixes, due to two poor existence of femtosecond laser frequency comb repetition, each pulse in each light pulse and reference arm light pulse in local oscillation light pulse and each pulse in gage beam light pulse all can be experienced respectively from being separated to close gradually, then stack, again gradually away from process, and every through one section of T
update=T
r1t
r2Δ T
rtime, said process can repeat once, and by the first photoelectric detector PD
1with the second photoelectric detector PD
2survey.The first femtosecond laser frequency comb FLFC
1pulse interval interval can be expressed as T
r1c, the aerial light velocity of c pulse, the second femtosecond laser frequency comb FLFC
2pulse interval be spaced apart T
r2c, for the convenience of follow-up data processing, the present invention is calculating seasonal R
a1=T
r1c/2, R
a2=T
r2c/2.
When measuring distance, L is less than R
a1time, from the second corner reflector CR
2the light pulse meeting of returning is at the first corner reflector CR
1before the next pulse returning, arrive the first spectroscope BS
1, can not misplacing by pulsing, the distance L therefore measuring is actual distance value, and when measuring distance, L is greater than R
a1time, from the second corner reflector CR
2the light pulse of returning may be at the first corner reflector CR
1after the next pulse returning, just arrive, thus pulsing dislocation, and the distance L now measuring is not actual distance value, needs cumulative upper R
a1integral multiple can obtain actual range, below the concrete computation process of L is described in detail:
1) when measuring distance L is less than R
a1time, the present invention is as follows to the signal processing of measuring distance L:
As shown in Figure 4, at each T
updatein time, local oscillation light pulse respectively with reference arm light pulse and gage beam light pulse superposeed once (as shown in the dotted line frame in Fig. 4).For the first photoelectric detector PD
1the signal detecting, its centre wavelength is λ
1, corresponding centre frequency is ν
1.Known according to the theorem of the corresponding frequency domain phase shift of time domain translation, in the superposed signal of these two positions, frequency is ν
11phase delay (the ν of spectrum line
11centered by frequency ν
1near any spectrum line, its phase delay is (a) and (b) the spectrum line ν in position sensing signal in Fig. 4
11corresponding phase differential) Δ φ
11(ν
11) and reference arm light pulse and gage beam light pulse time delay τ between pass be:
Δφ
11(ν
11)=(2πτ)﹒ν
11 （1）
Can obtain twice optical pulse overlap by formula (1) time, the phase delay frequency corresponding with spectrum line of spectrum line is directly proportional, signal processing unit 2 by (a) position receiving and (b) interference light signal of position carry out Fourier transform, and the phase frequency spectrum of twice pulse overlap is done to difference operation, obtain the phase delay of different spectrum lines, the phase delay (φ that obtains a series of different light frequencies and answer in contrast
1i, ν
1i), i represents the sequence number of spectrum line, then some to (φ by what obtain
1i, ν
1i) carrying out fitting a straight line, the slope that obtains fitting a straight line is b
1(b
1=2 π τ), finally obtain tested distance L for (time delay τ correspondence light on measuring distance come and go):
L=cτ/2=b
1c/4π.（2）
In order further to improve measuring accuracy, can utilize the information of interferometric phase.First, for the signal detecting for the first photoelectric detector PD 1, the centre wavelength of interference light pulse is λ
1, central wavelength lambda
1corresponding interferometric phase Δ φ
1, according to principle of interference, light pulse central wavelength lambda
1at (a) of pulse overlap and (b) the interference phase difference Δ φ of position
1and the pass between tested distance L is:
L=(Δφ
1/2π+m
1)﹒λ
1/2 （3）
In formula, m
1that wavelength is λ
1integer level corresponding to the interference of light time (" several greatly "), be nonnegative integer.
Due to Δ φ
1can be according to formula (1) phase place that by (a) position and (b) interference light signal of position carries out Fourier transform subtract each other and obtain again.If therefore can accurately obtain m
1, can obtain accurate distance L, but conventionally will obtain m
1, be generally that the bigness scale distance value obtaining by formula (2) is removed with λ
1/ 2 rear rounds are asked.While rounding in order guaranteeing to calculate, not produce deviation, to need the bigness scale precision that meets L to be better than λ
1/ 4 condition, the criterion that in this and laser interferometry, precision is refined is step by step similar.In order to meet this condition, existing more conventional method is to carry out getting average to improve bigness scale precision after repeatedly bigness scale, is better than λ until the precision after average reaches
1when/4 condition, ask for again m
1but measuring speed reduces greatly.
For the second photoelectric detector PD
2the signal detecting, the centre wavelength of interference light pulse is λ
2, central wavelength lambda
2corresponding interferometric phase Δ φ
2, according to principle of interference, light pulse central wavelength lambda
2at (a) of pulse overlap and (b) the interference phase difference Δ φ of position
2and the pass between tested distance L is:
L=(Δφ
2/2π+m
2)﹒λ
2/2 （4）
In formula, m
2for wavelength is λ
2integer level corresponding to the interference of light time (" several greatly "), be nonnegative integer.By formula (3) and formula (4) simultaneous abbreviation, by formula (3) and λ
2the result multiplying each other deducts formula (4) and λ
1after the result multiplying each other, obtain:
L=(Δφ
s/2π+m
s)﹒λ
s/2 （5）
In formula, λ
s=λ
1λ
2/ (λ
2-λ
1), be λ
1and λ
2composite wave wavelength; Δ φ
s=Δ φ
1-Δ φ
2, be composite wave phase place; m
sfor the integer level time (" several greatly ") of composite wave, it is nonnegative integer.Due to λ
1, λ
2, Δ φ
1with Δ φ
2be known, so composite wave wavelength X
swith composite wave phase delta phi
sall can calculate, if can obtain m accurately
svalue, can obtain tested distance by formula (5) by composite wave wavelength and phase place.The bigness scale value substitution formula (5) of the L in the present embodiment, formula (2) being obtained calculates m
s, and to m
scarry out round.For the m that guarantees to calculate
sbe accurately, the bigness scale precision that only need to meet L is better than λ
s/ 4.Mention hereinbefore λ
1and λ
2choose time need meet this condition, this is easy to accomplish, illustrates below:
With λ
1=1.555 μ m, λ
2=1.565 μ m are example, composite wave wavelength X
s=243.36 μ m.And the precision of existing single bigness scale L is generally several microns, be far superior to λ
s/ 4, therefore enough guarantee to obtain m accurately
s, by m
sin generation, is got back to formula (5) again, and according to λ
swith Δ φ
scan calculate comparatively accurate distance L.Take phase accuracy 0.5 degree as example, the precision of the L now obtaining can reach λ
s/ 2 ﹒ (0.5/360)=0.17 μ m, has been better than existing measuring accuracy λ
1/ 4.Therefore now comparatively accurate L value is updated to formula (3), calculates m
1and round, can obtain m accurately
1value.Again by m
1in generation, is got back to formula (3), and according to λ
1with Δ φ
1can recalculate and obtain accurate L value.Still, take phase accuracy 0.5 degree as example, now the precision of L can reach λ
1/ 2 ﹒ (0.5/360)=1.1nm.Can see by above-mentioned example, can not sacrifice under the condition of measuring speed by this method, directly bigness scale (precision of several microns) is transitioned into accurate measurement (nano level precision).
2) when measuring distance L is greater than R
a1time, can measure by cursor principle, concrete grammar is:
1. when measuring distance L is greater than R
a1time, suppose that k (k is any positive integer, indicating impulse sequence number) pulse of gage beam light pulse is from the first spectroscope BS
1propagate into the second corner reflector CR
2turn back to again the first spectroscope BS
1period in, the k of reference arm light pulse, k+1 ..., k+m(m is positive integer) and individual pulse completed by the first spectroscope BS
1propagate into the first corner reflector CR
1turn back to again the first spectroscope BS
1process, in other words, there is the dislocation in m cycle in the shown reference arm light pulse train of lastrow and gage beam light pulse sequence as shown in Figure 4, the distance of the dislocation correspondence in each cycle is R
a1but, adopt the above-mentioned the 1st) plant the measuring method of situation, the periodicity m of dislocation cannot be come out, according to method 1) measure time delay corresponding be the Delay between k+m pulse of reference arm light pulse and k pulse of gage beam light pulse, by now survey distance be designated as D
1, actual tested distance L can be write as L=mR
a1+ D
1form, D
1<R
a1;
2. by measuring method 1 of the present invention) measure distance value D
1;
3. by the first femtosecond laser frequency comb FLFC of laser distance measuring system of the present invention
1with the second femtosecond laser frequency comb FLFC
2exchange, that is: the second femtosecond laser frequency comb FLFC
2as measuring-signal source, the first femtosecond laser frequency comb FLFC
1as oscillation signals according source, adopt measuring method 1 of the present invention) measure distance value D
2, D
2<R
a2;
4. due to measured before and after two femtosecond laser frequencies of exchange comb be same distance L, can be expressed as following form:
L=mR
A1+D
1=mR
A2+D
2 （6）
In formula, the definition of m is the same, is the dislocation periodicity between reference arm pulse and gage beam pulse, R
a1and R
a2be known number, due to R
a1and R
a2there is small difference, and this difference can be embodied in D along with the difference of m value
1and D
2difference on.Therefore according to the D recording
1and D
2can obtain m, then by m substitution formula (6), can calculate actual distance value L.
In order to ensure formula (6) both sides R
a1and R
a2coefficient m identical, need to meet L/R
a1round and L/R
a2what round comes to the same thing, and therefore needs to meet L<R
a1r
a1/ (R
a1-R
a2).
The various embodiments described above are only for illustrating the present invention; wherein can to adopt conventional support to support fixing for each optical element; and the position of optical element etc. all can change to some extent; as long as meet light path propagation conditions of the present invention; every equivalents of carrying out on the basis of technical solution of the present invention and improvement, all should not get rid of outside protection scope of the present invention.
Claims (4)
1. two femtosecond laser frequency comb synthesis wave to interfere range measurement systems, is characterized in that: it comprises the first femtosecond laser frequency comb, the second femtosecond laser frequency comb, Michelson interference system, the second spectroscope, the 3rd spectroscope, the first narrow band filter, the second narrow band filter, the first photodetector, the second photodetector, A/D converter and signal processing unit; Wherein, described Michelson interference system comprises the first spectroscope, the first corner reflector and the second corner reflector;
Described the first femtosecond laser frequency is combed as measuring-signal source, send light pulse to described the first spectroscope, light pulse through described the first spectroscope reflection is transmitted into described the first corner reflector, is transmitted to described the second spectroscope again through the light pulse of described the first corner reflector reflection through described the first spectroscope; Be transmitted into described the second corner reflector through the light pulse of described the first spectroscope transmission, after described the second corner reflector reflection, reflex to described the second spectroscope through described the first spectroscope again; Described the second femtosecond laser frequency is combed as oscillation signals according source, send light pulse to described the second spectroscope, through the light pulse of described the second spectroscope transmission with mix through the light pulse of described Michelson interference system outgoing, mixed light impulse ejection is to described the 3rd spectroscope; Light pulse through described the 3rd spectroscope transmission is surveyed and is received by described the first photodetector after described the first narrow band filter; Light pulse through described the 3rd spectroscope reflection is surveyed and is received by described the second photodetector after described the second narrow band filter; The output terminal of described the first photodetector and the second photodetector is connected respectively to the input end of described A/D converter, and the output terminal of described A/D converter is connected to described signal processing unit by corresponding data interface the signal of reception is processed and obtained required measuring distance value.
2. the two femtosecond laser frequency comb of one as claimed in claim 1 synthesis wave to interfere range measurement system, it is characterized in that: the spectral distribution of described the first femtosecond laser frequency comb and the second femtosecond laser frequency comb must have larger width, and must have larger overlapping region, this overlapping region accounts for the over half of the two spectral width own.
3. the two femtosecond laser frequency comb of one as claimed in claim 2 synthesis wave to interfere range measurement system, is characterized in that: the centre wavelength of described the first narrow band filter and the second narrow band filter is respectively λ
1and λ
2, λ
1and λ
2must be in described larger overlapping region, and λ
1and λ
2choose and need to meet following two conditions simultaneously:
1) choose according to bigness scale precision, make bigness scale precision be better than λ
s/ 4, λ
s=λ
1λ
2/ (λ
2-λ
1), be λ
1and λ
2composite wave wavelength;
2) choose according to interferometric phase measuring accuracy θ, make by composite wave λ
sthe precision of range finding is better than λ
1/ 4 or λ
2/ 4, wherein, composite wave λ
sthe precision of range finding is λ
s/ 2 ﹒ (θ/360).
4. the two femtosecond laser frequency comb of the one as described in claim 1 or 2 or 3 synthesis wave to interfere range measurement system, is characterized in that: described the first narrow band filter and the second narrow band filter all adopt Fiber Bragg Grating FBG.
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|---|---|---|---|
| CN201410106555.4A CN103837077B (en) | 2014-03-21 | 2014-03-21 | Composite wave interferometry ranging distance system with two femtosecond laser frequency combs |
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