CN109212550A - The FM-CW laser ranging method of integrated FP etalon - Google Patents
The FM-CW laser ranging method of integrated FP etalon Download PDFInfo
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- CN109212550A CN109212550A CN201811067690.7A CN201811067690A CN109212550A CN 109212550 A CN109212550 A CN 109212550A CN 201811067690 A CN201811067690 A CN 201811067690A CN 109212550 A CN109212550 A CN 109212550A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
- G01S17/32—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
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- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
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Abstract
The invention discloses the FM-CW laser ranging methods of integrated FP etalon.Equal optical frequency intervals resampling is carried out as auxiliary interference system using optical fiber mach Zeng Deer interferometer, includes one section of long optical fiber as measuring basis, stability is poor, and there are dispersion phenomenons.The present invention passes through in FM-CW laser ranging system, increase FP etalon as auxiliary measurement system, to the optical frequency intervals resampling such as sampled signal carries out, then resampling signal is handled using Hilbert transform algorithm, acquires the absolute distance of measured target.The present invention is long using the chamber of FP etalon rather than long optical fibers are as ranging benchmark, and overcoming the environmentally sensitive property of long optical fibers and fibre-optical dispersion influences range accuracy, and can realize the measurement of higher precision in the lesser situation of laser modulation range.
Description
Technical field
The invention belongs to laser three-D ranging technology fields, and in particular to a kind of CW with frequency modulation of integrated FP etalon is sharp
Ligh-ranging method.
Background technique
In recent years, FM-CW laser ranging is received more and more attention in laser ranging field, has and survey
Accuracy of measurement is high, the advantages that Models of Absolute Distance Measurement Based may be implemented, can directly be measured diffusing reflection target.CW with frequency modulation Laser Measuring
Away from measurement accuracy influenced by laser scans range and the laser scans linearity, it is therefore desirable to the optical frequency intervals such as utilize
Resampling method carries out processed offline to obtained interference signal to improve measurement accuracy.Currently in order to the optical frequency intervals weight such as using
Sampling method increases a set of optical fiber mach Zeng Deer interference system, usually in FM-CW laser ranging system to realize
Optical frequency interval resampling.But due to wherein containing one section of long optical fiber as measuring basis, stability is poor, and exists
Dispersion phenomenon causes measurement accuracy unsatisfactory.
Summary of the invention
In view of the deficiencies of the prior art, it is an object of the present invention to provide a kind of CW with frequency modulation laser of integrated FP etalon
Distance measuring method.The present invention is by the way that in FM-CW laser ranging system, increase FP etalon is right as auxiliary measurement system
The optical frequency intervals resamplings such as sampled signal carries out, then handle resampling signal using Hilbert transform algorithm, ask
Obtain the absolute distance of measured target.
Step of the invention is as follows:
Step 1, the FM-CW laser ranging system for building integrated FP etalon, it is adjustable in the laser ranging system
The narrow-linewidth laser of humorous laser controller control tunable laser transmitting optical frequency linear modulation, laser successively pass through optical isolation
After device, collimation lens set and half wave plate, it is divided into two-way using polarization splitting prism, respectively enters measurement interference system
With FP interference system, interference signal all the way is respectively obtained in measurement interference system and FP interference system.Wherein, FP interference system
FP etalon be placed in vacuum chamber.
Step 2, high-speed data acquistion system two paths done respectively to measurement interference system and with reference to interference system
It relates to signal and synchronizes data acquisition, obtain signal sig1 and sig2.After the modulation commencing signal of tunable laser is issued
First peak dot of signal sig2 is as starting point, and before the modulation termination signal of tunable laser issues, signal sig2 is most
The latter peak point is as terminating point, if signal sig2 shares k comprising starting point and ending point between starting point and ending point
A peak point.
Step 3 carries out double sampling to signal sig1 in each peak point position of signal sig2, obtains resampling letter
Number sig3.
The quantity of the maximum and minimum of signal sig1 point between step 4, the two neighboring peak point of tracer signal sig2
It Wei not Mi, M is calculated in (i=1,2 ... ..., k-1)iAverage value be Mmean。
Step 5, using Hilbert transform, acquire the instantaneous phase of resampling signal sig3, and to obtained instantaneous phase
After position carries out unwrapping, an incremental curve is obtained.Then, linear fit is carried out to the curve using least square method, asked
The slope of straight line is l after must being fitted.Enable fI=l/ (2 π), fIThe as frequency of resampling signal sig3.
Step 6, the distance L that measured target is calculated using following formula.
Wherein, m MmeanInteger part, dFPChamber for FP etalon is long, ngFor the refractive index of air.
Further, the narrow line of external cavity type that the tunable laser uses central wavelength to be 1nm for 633nm, modulation range
Wide tunable laser device.
The step 1 further describes are as follows: in measurement interference system, laser is divided into two by unpolarized Amici prism
Road is measured retroreflective prism and reflects with reference to retroreflective prism, respectively then in the semi-transparent semi-reflecting face of unpolarized Amici prism
Converge, then enter optical fiber via collimation lens, is divided into two-way by 50:50 fiber coupler, respectively enters balanced detector
Two detection mouths form interference signal.
The step 1 further describes are as follows: in FP interference system, laser is successively laggard through reflecting mirror and No.1 convex lens
Enter FP etalon；The shoot laser of FP etalon focuses after No. two convex lenses in photodetector surfaces, obtains interference letter
Number.
Further, by adjusting the angle of polarization splitting prism and reflecting mirror, enable laser along FP etalon central axis
Direction enter FP etalon, by adjusting the position of No.1 convex lens, enable laser in the centre focus of FP etalon.
Method with existing processing FM-CW laser ranging signal is (using optical fiber mach Zeng Deer interferometer as auxiliary
Help the optical frequency intervals resamplings such as interference system carries out) it compares, the beneficial effects of the present invention are: the present invention passes through in CW with frequency modulation
In laser ranging system, increase FP etalon as auxiliary measurement system, to the optical frequency intervals resampling such as sampled signal carries out, so
Resampling signal is handled using Hilbert transform algorithm afterwards, acquires the absolute distance of measured target；Wherein, FP is marked
The chamber of quasi- tool is long rather than long optical fibers overcome the environmentally sensitive property of long optical fibers and fibre-optical dispersion to ranging essence as ranging benchmark
Degree influences, and can realize the measurement of higher precision in the lesser situation of laser modulation range.
Detailed description of the invention
Fig. 1 is the schematic diagram that the FM-CW laser ranging system of FP etalon is integrated in the present invention；
Fig. 2 is the collected signal segment schematic diagram of high-speed data acquistion system of the invention；
Fig. 3 is the schematic diagram of resampling signal sig3；
Fig. 4 is the instantaneous phase figure of the resampling signal sig3 acquired using Hilbert transform；
Fig. 5 is the phase diagram after the instantaneous phase unwrapping of resampling signal sig3；
In figure: 1, tunable laser, 2, optoisolator, 3, collimation lens set, 4, half wave plate, 5, polarization spectro
Prism, 6, measurement retroreflective prism, 7, with reference to retroreflective prism, 8, unpolarized Amici prism, 9, fiber collimating lenses, 10,50:
50 fiber couplers, 11, balanced detector, 12, reflecting mirror, 13, No.1 convex lens, 14, FP etalon, 15, vacuum chamber, 16,
No. two convex lenses, 17, photodetector, 18, tunable laser controller, 19, high-speed data acquistion system, 20, computer.
Specific embodiment
Present invention will be further explained below with reference to the attached drawings and examples.
The FM-CW laser ranging method of integrated FP etalon, the specific steps are as follows:
Step 1, as shown in Figure 1, build the FM-CW laser ranging system of integrated FP etalon, the laser ranging system
In system, control 1 emission center wavelength of tunable laser of tunable laser controller 18 is 633nm, modulation range is 1nm's
Optical frequency linear modulation laser, laser is successively after optoisolator 2, collimation lens set 3 and half wave plate 4, using inclined
Vibration Amici prism 5 divides for two-way, respectively enters measurement interference system and FP interference system.In measurement interference system, laser quilt
Unpolarized Amici prism 8 divides for two-way, measured retroreflective prism 6 and the reference reflection of retroreflective prism 7 respectively, then non-inclined
The semi-transparent semi-reflecting face of vibration Amici prism 8 is converged, then enters optical fiber via collimation lens 9, divides by 50:50 fiber coupler 10 and is
Two-way, two detection mouths for respectively enteing balanced detector 11 form interference signal.In FP interference system, laser is successively through reflecting
Enter FP etalon 14 after mirror 12 and No.1 convex lens 13, FP etalon 14 is placed in vacuum chamber 15；By adjusting polarization point
The angle of light prism 5 and reflecting mirror 12 enables laser enter FP etalon 14 along the direction of 14 central axis of FP etalon；Pass through
The position for adjusting No.1 convex lens 13, enables laser in the centre focus of FP etalon.The shoot laser of FP etalon passes through No. two
It is focused after convex lens 16 on 17 surface of photodetector, forms interference signal.
Step 2, the channel one of high-speed data acquistion system 19 and channel two are respectively to measurement interference system and FP interference system
The interference signal of system synchronizes data acquisition, obtains signal sig1 (bold portion in Fig. 2) and sig2 (dotted line part in Fig. 2
Point).The signal sig1 and sig2 that collect deposit computer 20 are handled；The modulation of tunable laser is started into letter
Number issue after signal sig2 first peak dot as starting point；Before the modulation termination signal of tunable laser issues, signal
The last one peak point of sig2 is as terminating point, if signal sig2 includes starting point and termination between starting point and ending point
Point shares k peak point.
Step 3 carries out double sampling to signal sig1 in each peak point position of signal sig2, obtains resampling letter
Number sig3, as shown in Figure 3.
The maximum and minimum quantity of signal sig1 point between step 4, tracer signal sig2 each adjacent two peak point
It Wei not Mi, M is calculated in (i=1,2 ... ..., k-1)iAverage value be Mmean。
Step 5, using Hilbert transform, acquire the instantaneous phase of resampling signal sig3, as shown in Figure 4.To obtaining
Instantaneous phase carry out unwrapping after, obtain an incremental curve, as shown in Figure 5.Then, using least square method to the song
Line carries out linear fit, and the slope for acquiring straight line after being fitted is l.In Fig. 5, open circles are instantaneous phase data point, and straight line is most
Small two multiply the straight line that fitting obtains.Enable fI=l/ (2 π), fIThe as frequency of resampling signal sig3.
Step 6, the distance L that measured target is calculated using following formula.
Wherein, m MmeanInteger part, dFPChamber for FP etalon is long, ngFor the refractive index of air.
Claims (5)
1. the FM-CW laser ranging method of integrated FP etalon, it is characterised in that: this method is specific as follows:
Step 1, the FM-CW laser ranging system for building integrated FP etalon, it is tunable to swash in the laser ranging system
Light device controller control tunable laser transmitting optical frequency linear modulation narrow-linewidth laser, laser successively pass through optoisolator,
After collimation lens set and half wave plate, be divided into two-way using polarization splitting prism, respectively enter measurement interference system and
FP interference system respectively obtains interference signal all the way in measurement interference system and FP interference system；Wherein, FP interference system
FP etalon is placed in vacuum chamber；
Step 2, high-speed data acquistion system two paths respectively to measurement interference system and with reference to interference system interference believe
Data acquisition number is synchronized, signal sig1 and sig2 are obtained；Signal after the modulation commencing signal of tunable laser is issued
First peak dot of sig2 is as starting point, before the modulation termination signal of tunable laser issues, signal sig2 last
A peak point is as terminating point, if signal sig2 shares k peak comprising starting point and ending point between starting point and ending point
Value point；
Step 3 carries out double sampling to signal sig1 in each peak point position of signal sig2, obtains resampling signal
sig3；
The maximum of signal sig1 and the quantity of minimum are respectively between step 4, the two neighboring peak point of tracer signal sig2
Mi, M is calculated in (i=1,2 ... ..., k-1)iAverage value be Mmean；
Step 5, using Hilbert transform, acquire the instantaneous phase of resampling signal sig3, and to obtained instantaneous phase into
After row unwrapping, an incremental curve is obtained；Then, linear fit is carried out to the curve using least square method, acquired quasi-
The slope of straight line is l after conjunction；Enable fI=l/ (2 π), fIThe as frequency of resampling signal sig3；
Step 6, the distance L that measured target is calculated using following formula；
Wherein, m MmeanInteger part, dFPChamber for FP etalon is long, ngFor the refractive index of air.
2. the FM-CW laser ranging method of integrated FP etalon according to claim 1, it is characterised in that: described
Tunable laser uses the external cavity type narrow line width regulatable laser that central wavelength is 1nm for 633nm, modulation range.
3. the FM-CW laser ranging method of integrated FP etalon according to claim 1 or 2, it is characterised in that:
The step 1 further describes are as follows: measurement interference system in, laser is divided into two-way by unpolarized Amici prism, respectively by
It measures retroreflective prism and is reflected with reference to retroreflective prism, then converged in the semi-transparent semi-reflecting face of unpolarized Amici prism, then pass through
Optical fiber is entered by collimation lens, is divided into two-way by 50:50 fiber coupler, respectively enters two detection mouths of balanced detector
Form interference signal.
4. the FM-CW laser ranging method of integrated FP etalon according to claim 1 or 2, it is characterised in that:
The step 1 further describes are as follows: in FP interference system, laser successively enters FP standard after reflecting mirror and No.1 convex lens
Tool；The shoot laser of FP etalon focuses after No. two convex lenses in photodetector surfaces, obtains interference signal.
5. the FM-CW laser ranging method of integrated FP etalon according to claim 4, it is characterised in that: pass through
The angle for adjusting polarization splitting prism and reflecting mirror, enables laser enter FP etalon along the direction of FP etalon central axis,
By adjusting the position of No.1 convex lens, enable laser in the centre focus of FP etalon.
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Cited By (3)
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| CN109945778A (en) * | 2019-04-15 | 2019-06-28 | 中国航空工业集团公司北京长城计量测试技术研究所 | Optical frequency modulation method micromicron grade resolving power large stroke laser measuring device |
| CN110716202A (en) * | 2019-10-23 | 2020-01-21 | 浙江理工大学 | Frequency modulation continuous wave sonar ranging method and device based on resampling |
| CN111781607A (en) * | 2020-08-07 | 2020-10-16 | 中国计量大学 | Forward and reverse tuning dispersion cancellation method and device based on laser frequency modulation continuous wave |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111781607A (en) * | 2020-08-07 | 2020-10-16 | 中国计量大学 | Forward and reverse tuning dispersion cancellation method and device based on laser frequency modulation continuous wave |
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