CN110375864A - A method of expanding CW with frequency modulation laser interferometry range - Google Patents
A method of expanding CW with frequency modulation laser interferometry range Download PDFInfo
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- CN110375864A CN110375864A CN201910648286.7A CN201910648286A CN110375864A CN 110375864 A CN110375864 A CN 110375864A CN 201910648286 A CN201910648286 A CN 201910648286A CN 110375864 A CN110375864 A CN 110375864A
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- 238000000034 method Methods 0.000 title claims abstract description 15
- 238000004556 laser interferometry Methods 0.000 title claims abstract description 14
- 230000035559 beat frequency Effects 0.000 claims abstract description 34
- 230000003287 optical effect Effects 0.000 abstract description 14
- 238000005305 interferometry Methods 0.000 abstract description 3
- 238000005259 measurement Methods 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000004065 semiconductor Substances 0.000 description 2
- 241000208340 Araliaceae Species 0.000 description 1
- 235000005035 Panax pseudoginseng ssp. pseudoginseng Nutrition 0.000 description 1
- 235000003140 Panax quinquefolius Nutrition 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 235000008434 ginseng Nutrition 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
- G01J9/02—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
- G01J9/02—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
- G01J2009/0249—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods with modulation
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- Spectroscopy & Molecular Physics (AREA)
- General Physics & Mathematics (AREA)
- Instruments For Measurement Of Length By Optical Means (AREA)
Abstract
The present invention relates to optics CW with frequency modulation interferometry technical fields, expand the method for CW with frequency modulation laser interferometry range.What CW with frequency modulation laser interference obtained is a dynamic beat signal, its frequency and initial phase are all related with the optical path difference in interferometer between signal light and reference light, when optical path difference is smaller or larger, it normally can not accurately identify initial phase or optical path difference, so there are two " dead zones " for CW with frequency modulation laser interference.Present invention provide the technical scheme that change the laser frequency modulation degree of CW with frequency modulation laser light source by the beat frequency rate for measuring current interference signal, being in the beat frequency rate of interference signal always can be effectively in the frequency range of phase demodulation.The invention has the advantages that not only can reduce optical path difference it is smaller when " preceding dead zone ", but also can eliminate optical path difference it is larger when " rear dead zone ", thus significantly expand CW with frequency modulation laser interferometry range.
Description
Technical field:
The present invention relates to optics CW with frequency modulation interferometry technical fields, and in particular to a kind of expansion CW with frequency modulation is sharp
The method of optical interferometry range.
Background technique:
Optics CW with frequency modulation (FMCW) interference is a new Technology of Precision Measurement.This optical interference techniques use one
The laser light source of a periodically continued linear modulation of light frequency.When in interference device signal light and reference light meet when interfering,
Generated interference signal is a dynamic beat signal, the light path of frequency and initial phase all between signal light and reference light
Difference is related.When optical path difference is smaller, since beat frequency rate is lower, initial phase and its change direction, theory point possibly can not be identified
Analysis points out that only beat frequency rate is greater than or equal to 2.5 times of laser modulation frequency, could normally identify initial phase.Frequency modulation connects
There are two " dead zones " for continuous wave laser interference, corresponding when optical path difference is smaller to be known as " preceding dead zone ", when optical path difference is larger, beat frequency frequency
Rate is higher, since the ADC sample frequency in digital signal processing circuit is that state is fixed constant, the signal number in each beat period
It is necessarily reduced according to amount, seriously affecting measurement can not accurately, even measure, referred to as " rear dead zone ".The presence in dead zone, limits
The measuring range of CW with frequency modulation laser interference.
Summary of the invention:
The present invention proposes a kind of method for expanding CW with frequency modulation laser interferometry range, to overcome the prior art to exist
CW with frequency modulation laser interference the limited problem of measuring range.
In order to reach the purpose of the present invention, present invention provide the technical scheme that a kind of expansion CW with frequency modulation laser is dry
The method for relating to measuring range, it is characterised in that: by measuring the beat frequency rate of current interference signal, the beat frequency rate is linear
Modulation changes the laser frequency modulation degree of CW with frequency modulation laser light source, the beat frequency rate of interference signal is made to be in can have always
In the frequency range for imitating phase demodulation, so as to initial phase and its variation of interference signal accurately be measured, to significantly expand
CW with frequency modulation laser interferometry range.
When beat frequency rate≤3 × modulating frequency, increases laser drive signal according to 2/3 geometric progression and modulate straight line
Slope updates linear modulated data table, until beat frequency rate > 3 × modulating frequency.
When beat frequency rate >=10 × modulating frequency, reducing interpolation straight slope according to 2/3 geometric progression is k, more new line
Property modulation data table, until beat frequency rate < 10 × modulating frequency.
Compared with prior art, the invention has the advantages that
1, it is in the beat frequency rate of interference signal always in a suitable frequency range,
So as to accurately measure initial phase and its variation of interference signal.
2, this method not only can reduce " preceding dead zone ", but also can eliminate " rear dead zone ", adjust to significantly expand
Frequency continuous wave laser interferometry range.
3, this method is applicable not only to the interference of saw wave modulator CW with frequency modulation, and it is continuous to be also applied for triangular modulation frequency modulation
Wave interference.
Detailed description of the invention:
Fig. 1 be semiconductor laser driving signal be sawtooth waveform when, the waveform of different value of K driving current.
Specific embodiment:
The present invention is described in detail below in conjunction with drawings and examples.
According to optics CW with frequency modulation interference theory, if laser frequency is linear modulation (such as saw wave modulator or three
The modulation of angle wave), for any dual beam optical CW with frequency modulation interference system, the luminous intensity I (τ, t) of interference signal can be indicated
For
I (τ, t)=I0[1+Vcos(ατt+ω0τ)] (1)
Wherein, I0For the average luminous intensity (I of interference signal0=I1+I2, I1For reference light intensity, I2For signal light intensity),
V is the contrast of interference signalω0For filters center angular frequency, τ is signal light relative to ginseng
The delay time (τ=OPD/c, OPD are optical path difference of the signal light relative to reference light, and c is the light velocity) of light is examined, α is laser angle
Frequency modulation rate (α=Δ ω/Tm, Δ ω is laser angular frequency modulation range, TmFor the modulated signal period).
Above formula indicates that linear frequency modulation continuous wave interference signal is a Dynamic Signal, beat frequency rate and initial phase all with
Signal light is proportional relative to the delay time τ (or both between optical path difference) of reference light.But beat frequency rate and laser
Device angular frequency modulation rate α is related, and initial phase and filters center angular frequency0It is related.This means that changing laser angle
Frequency modulation rate α, thus it is possible to vary the beat frequency rate of interference signal, but not influence the measurement of initial phase (i.e. optical path difference).
Based on above-mentioned theory, a kind of method expanding CW with frequency modulation laser interferometry range provided by the invention is led to
The beat frequency rate for measuring current interference signal is crossed, the beat frequency rate is linear modulation, changes CW with frequency modulation laser light source
Laser frequency modulation degree, make the beat frequency rate of interference signal be in always can effectively phase demodulation frequency range in, so as to smart
The initial phase of true measurement interference signal and its variation, to significantly expand CW with frequency modulation laser interferometry range.
When beat frequency rate≤3 × modulating frequency, increases laser drive signal according to 2/3 geometric progression and modulate straight line
Slope updates linear modulated data table, until beat frequency rate > 3 × modulating frequency.
When beat frequency rate >=10 × modulating frequency, reducing interpolation straight slope according to 2/3 geometric progression is k, more new line
Property modulation data table, until beat frequency rate < 10 × modulating frequency.
Described laser driving circuit and interferometer signal processing circuit is all using digital circuit, laser driving letter
It number is to be obtained by microcomputer reads data form by DA circuit conversion, the laser frequency modulation degree and laser that laser issues
The modulation degree of device driving signal is directly proportional；Data form is average value and linear modulated data two parts composition, linear modulation number
It is obtained according to by the linear interpolation that a slope is k, interference signal is that electric signal is converted by photodetector using AD electricity
The digital signal that road is converted to.
Embodiment: a method of expanding CW with frequency modulation laser interferometry range, includes the following steps:
Step 1: for digital semiconductor laser CW with frequency modulation interference modulations and demodulating system, laser driving letter
It number is to be obtained by microcomputer reads data form using DA circuit conversion, data include average value and linear modulated data two
Part, linear modulated data are obtained according to the linear interpolation that a slope is k.Interference signal is that light is believed by photodetector
Number digital signal that is obtained using AD circuit conversion of transformation electric signal, by measuring interference signal waveform in each modulation period
Minimum point (or maximum point) position on a timeline can calculate the beat frequency rate of interference signal.Referring to Fig. 1, originally
The driving signal gone out given in embodiment is sawtooth waveform.
When beat frequency rate≤3 × modulating frequency, increasing interpolation straight slope according to 2/3 geometric progression is k, more new line
Property modulation data table, until beat frequency rate > 3 × modulating frequency.
The beat frequency rate of CW with frequency modulation interference in this way can be in the frequency range of 3 to 10 times of modulating frequencies always, for height
Precision identifies initial phase and provides good condition.
Note: the maximum value k of kmaxIt is determined by laser threshold current and operating current and modulating frequency, if k increases
To maximum value kmaxWhen, the corresponding OPD of beat frequency rate≤3 × modulating frequency is known as " remaining preceding dead zone ", and measurement should when being displaced
Avoid " remaining preceding dead zone ".
Claims (3)
1. a kind of method for expanding CW with frequency modulation laser interferometry range, it is characterised in that: by measuring current interference letter
Number beat frequency rate, change CW with frequency modulation laser light source laser frequency modulation degree, make the beat frequency rate of interference signal always
Be in can effectively phase demodulation frequency range in, so as to accurately measure interference signal initial phase and its variation, thus greatly
Amplitude expands CW with frequency modulation laser interferometry range.
2. a kind of method for expanding CW with frequency modulation laser interferometry range as described in claim 1, it is characterised in that: when
When beat frequency rate≤3 × modulating frequency, increases laser drive signal according to 2/3 geometric progression and modulate straight slope, more new line
Property modulation data table, until beat frequency rate > 3 × modulating frequency.
3. a kind of method for expanding CW with frequency modulation laser interferometry range as described in claim 1, it is characterised in that: when
When beat frequency rate >=10 × modulating frequency, reducing interpolation straight slope according to 2/3 geometric progression is k, updates linear modulated data
Table, until beat frequency rate < 10 × modulating frequency.
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101031814A (en) * | 2004-09-28 | 2007-09-05 | 秦内蒂克有限公司 | Frequency modulated continuous wave (FMCW) radar having improved frequency sweep linearity |
| US20090251361A1 (en) * | 2005-03-29 | 2009-10-08 | Beasley Patrick D L | Coherent Frequency Modulated Continuous Wave Radar |
| CN105006736A (en) * | 2015-05-08 | 2015-10-28 | 上海交通大学 | Frequency modulated continuous wave (FMCW) frequency sweep non-leaner calibration system based on closed loop control and FMCW frequency sweep non-leaner calibration method based on closed loop control |
| CN108050941A (en) * | 2017-12-25 | 2018-05-18 | 西安工业大学 | A kind of CW with frequency modulation laser interference optical fiber displacement sensor and its displacement detecting method |
| CN108444381A (en) * | 2018-05-15 | 2018-08-24 | 西安工业大学 | One kind is for eliminating the nonlinear bearing calibration of semiconductor laser frequency modulation interference signal |
| CN109557547A (en) * | 2018-12-27 | 2019-04-02 | 武汉万集信息技术有限公司 | Laser radar, range measurement and/or method for determining speed and storage medium |
-
2019
- 2019-07-18 CN CN201910648286.7A patent/CN110375864B/en active Active
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|---|---|---|---|---|
| CN101031814A (en) * | 2004-09-28 | 2007-09-05 | 秦内蒂克有限公司 | Frequency modulated continuous wave (FMCW) radar having improved frequency sweep linearity |
| US20090251361A1 (en) * | 2005-03-29 | 2009-10-08 | Beasley Patrick D L | Coherent Frequency Modulated Continuous Wave Radar |
| CN105006736A (en) * | 2015-05-08 | 2015-10-28 | 上海交通大学 | Frequency modulated continuous wave (FMCW) frequency sweep non-leaner calibration system based on closed loop control and FMCW frequency sweep non-leaner calibration method based on closed loop control |
| CN108050941A (en) * | 2017-12-25 | 2018-05-18 | 西安工业大学 | A kind of CW with frequency modulation laser interference optical fiber displacement sensor and its displacement detecting method |
| CN108444381A (en) * | 2018-05-15 | 2018-08-24 | 西安工业大学 | One kind is for eliminating the nonlinear bearing calibration of semiconductor laser frequency modulation interference signal |
| CN109557547A (en) * | 2018-12-27 | 2019-04-02 | 武汉万集信息技术有限公司 | Laser radar, range measurement and/or method for determining speed and storage medium |
Non-Patent Citations (4)
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|---|
| SERDAL AYHAN等: "FMCW Radar System with Additional Phase Evaluation for High Accuracy Range Detection", 《PROCEEDINGS OF THE 8TH EUROPEAN RADAR CONFERENCE》 * |
| SERDAL AYHAN等: "Frequency Estimation Algorithm for an Extended FMCW Radar System with Additional Phase Evaluation", 《PROCEEDINGS OF THE 6TH GERMAN MICROWAVE CONFERENCE》 * |
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