CN106247930B - The residual compensation method of phase carrier formula laser interferometer closed loop demodulating algorithm - Google Patents

The residual compensation method of phase carrier formula laser interferometer closed loop demodulating algorithm Download PDF

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CN106247930B
CN106247930B CN201610821010.0A CN201610821010A CN106247930B CN 106247930 B CN106247930 B CN 106247930B CN 201610821010 A CN201610821010 A CN 201610821010A CN 106247930 B CN106247930 B CN 106247930B
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phase
closed loop
formula laser
signal
laser interferometer
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CN106247930A (en
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温强
刘鹏飞
廖为桂
李立
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Harbin Engineering University
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Harbin Engineering University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02055—Reduction or prevention of errors; Testing; Calibration

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Abstract

The present invention is to provide a kind of residual compensation methods of phase carrier formula laser interferometer closed loop demodulating algorithm.Interference light signal is multiplied with additional carrier signal, low-pass filtering, is removed, arc tangent obtains system residual error, the phase signal weighted sum that system residual error and closed loop are demodulated corrects measurement result with this.In phase carrier formula laser interferometer closed loop demodulating process, system can have different degrees of residual error because of the limitation of disturbance factor or tracking ability.The present invention has the advantages that phase-modulation high-ranking military officer's interference signal closed loop demodulation method, while also having higher demodulation accuracy.

Description

The residual compensation method of phase carrier formula laser interferometer closed loop demodulating algorithm
Technical field
The present invention relates to a kind of optical interferometry method, specifically a kind of phase carrier laser interference signal Residual compensation method.
Background technique
The phase demodulation algorithm for being widely used in optical interference type sensor is PGC algorithm, and principle is to utilize input letter Number carry out difference frequency processing with local phase-modulated wave, obtain the quadrature value that two-way is tested phase, recycle quadrature value and original signal into Row cross derivative is multiplied, and obtains tested phase value by trigonometric function relationship and Integral Processing.The eighties digital circuit be not In the case where very flourishing the problem of the proposition very good solution of algorithm engineering practicalization.But the algorithm is asked there are several Topic, is that the dynamic range of its work is very big by phase-modulated wave effect of signals first, and in addition system work does not have under open loop situations The long-term working stability of feedback loop guarantee system.In PGC algorithm there are one more serious problem be exactly be easy to by To the influence of association amplitude modulation, since PGC algorithm needs a phase-modulated wave signal to be modulated interferometer, laser is directly being modulated The amplitude for inducing one adjoint variation is easy during device phase, which can make final data result generate biggish harmonic distortion. On the other hand, the closed loop demodulating algorithm of phase carrier laser interference signal can also be limited because of disturbance factor or tracking ability, And there is different degrees of residual error.
Summary of the invention
The phase carrier formula laser interferometer closed loop with higher demodulation accuracy that the purpose of the present invention is to provide a kind of The residual compensation method of demodulating algorithm.
The object of the present invention is achieved like this:
Phase carrier formula laser interference signal after photoelectric conversion respectively with G cos ω0T and H cos2 ω0T makees multiplication Operation, in which: ω0For phase modulation frequency, G, H are respectively the amplitude of additional carrier wave；
It is filtered out using low-pass filter containing ω0AC compounent, obtainWithWherein: B is the AC compounent of light intensity after interference, J1(C)、J2(C) it is respectively and modulation of source depth Related Bessel function expansion coefficient, the ratio of the two are
The system residual error of closed loop demodulating algorithm is obtained through arctangent computationFor compensating closed loop phase demodulation result.
The present invention may also include:
When the phase change range that measured signal generates is less than or equal to positive and negative 45 degree, obtained residual error item is tested letter Number generate phase.
The present invention introduces closed loop residual compensation on the basis of phase carrier tries laser interference signal closed loop demodulating algorithm Mechanism.
Specifically, the interference signal after photodetector are as follows:
Wherein: I1,I2Respectively two beam interferometer light light intensity, A are the DC component of light intensity after interference, and B is light intensity after interference AC compounent,For interferometric phase changing value, expression formula are as follows:
Wherein in above formulaRespectively interfere initial phase, phase change caused by modulation of source,.Light Phase change caused by source is modulatedIt is related with modulation of source frequency ν.
Wherein n is optical fibre refractivity, and l is two-arm arm length difference, and c is the light velocity, and modulation electric current is i=i0cosω0T, then light source Caused frequency variation is ν=Δ ν cos ω0T obtains phase changing capacity caused by modulated signal are as follows:
Wherein C is modulation depth, is Fixed constant relevant to fibre optic interferometer and modulation, then interference signal form Are as follows:
Bezier expansion is carried out to it, is obtained:
Wherein JmIt (C) is the higher order coefficient under a certain modulation depth C.
The additional carrier signal G cos ω that formula and signal generator after Bezier is unfolded generate0t、H cos2ω0t It is multiplied, and is utilized respectively low-pass filtering and gets rid of comprising ω0Exchange item, can obtain:
After making division arithmetic, obtain:
Removal constant term simultaneously obtains the system phase residual error of closed loop phase demodulating algorithm using arctangent computationIt should Residual error is added with closed loop demodulation result as final demodulation result.
Present invention has an advantage that having the advantages that phase-modulation high-ranking military officer's interference signal closed loop demodulation method, while also having There is higher demodulation accuracy.
Detailed description of the invention
Fig. 1 is the flow chart of the residual compensation method of phase carrier formula laser interference signal closed loop demodulation.
Fig. 2 is the structure drawing of device of the residual compensation method of phase carrier formula laser interference signal closed loop demodulation.
Specific embodiment
It illustrates with reference to the accompanying drawing and the present invention is described in more detail.
In conjunction with Fig. 2, the inventive system comprises: 1, laser light source, 2, fiber coupler, 3, fibre optical sensor arm, 4, Optical fiber reference arm, 5, pickup arm reflecting mirror, 6, reference arm reflecting mirror, 7, photodetector, 8, bandpass filter, 9, for it is outer The multiplier that carrier signal is multiplied, 10, multiplier, 11, low-pass filter, 12, low-pass filter, 13, divider, 14, anyway Cut operation, 15, extracting operation, 16, PID controller, 17, adder, 18, the phase signal finally demodulated exported, 19, pressure Electroceramics driver, 20, piezoelectric ceramics.The device of the invention can be divided into two parts, and first part is the production of laser fiber interferometer The interferometric phase signal of raw phase carrier, including laser light source, fiber coupler, reference arm and pickup arm；Second part is this Invent provide phase carrier formula laser interferometer closed loop demodulating algorithm residual compensation method, phase demodulation modules therein by Centre frequency ω0Bandpass filter, multiplier, low-pass filter, evolution summation operation constitute, system residual compensation module by Multiplier, low-pass filter, divider, arctangent cp cp operation are constituted, and closed loop control module is by PID controller and piezoelectric ceramics structure At.
Interference signal is sent into programmable logic device (FPGA) through photoelectric conversion and AD sampling, and the interference of light is completed in FPGA Signal bandpass filtering, involution, low-pass filtering, extracting operation and PID arithmetic generate closed loop command signal, i.e. phase compensation is believed Number, compensation phase feed-in optical path is generated after signal amplification.
The interference signal of photoelectric conversion does phase with single frequency multiplication, double frequency carrier signal also in FPGA after AD is sampled simultaneously Multiplication, division, low-pass filtering and the arctangent cp cp operation answered, obtain system residual error.Residual error phase in FPGA with phase compensation signal Add to obtain final phase demodulating as a result, the signal is exported by FPGA.
In phase carrier formula laser interferometer closed loop demodulating process, system can because of the limitation of disturbance factor or tracking ability, And there is different degrees of residual error.The present invention provides a kind of residual errors of phase carrier formula laser interference signal closed loop demodulating algorithm Compensation method, specifically include that interference light signal is multiplied with additional carrier signal, low-pass filtering, is removed, arc tangent is System residual error, the phase signal weighted sum that system residual error and closed loop are demodulated correct measurement result with this.
Phase carrier formula laser interference signal after photoelectric conversion respectively with G cos ω0T and H cos2 ω0T makees multiplication Operation (ω0For phase modulation frequency, G, H are respectively the amplitude of additional carrier wave), and filtered out using low-pass filter containing ω0's AC compounent obtainsWith(B is the AC compounent of light intensity after interference, J1(C)、 J2(C) it is respectively Bessel function expansion coefficient related with modulation of source depth), the ratio of the two is The system residual error of closed loop demodulating algorithm can be obtained through arctangent computation according to the formulaAnd for compensating closed loop phase demodulation knot Fruit；
It, can be in appropriate adjustment quiescent point when the phase change range that measured signal generates is little (45 degree such as positive and negative) Afterwards, closed-loop system is switched into open loop situations, then obtained residual error item is exactly the phase that measured signal generates.

Claims (2)

1. a kind of residual compensation method of phase carrier formula laser interferometer closed loop demodulating algorithm, it is characterized in that:
Phase carrier formula laser interference signal after photoelectric conversion respectively with G cos ω0T and H cos2 ω0T makees multiplying, Wherein: ω0For phase modulation frequency, G, H are respectively the amplitude of additional carrier wave；
It is filtered out using low-pass filter containing ω0AC compounent, obtainWith Wherein: B is the AC compounent of light intensity after interference, J1(C)、J2It (C) is respectively Bessel function exhibition related with modulation of source depth The ratio of open system number, the two isC is modulation depth；
The system residual error of closed loop demodulating algorithm is obtained through arctangent computationFor compensating closed loop phase demodulation result.
2. the residual compensation method of phase carrier formula laser interferometer closed loop demodulating algorithm according to claim 1, special Sign is: when the phase change range that measured signal generates is between minus 45 degree to positive 45 degree, obtained residual error item is tested The phase that signal generates.
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CN108007550B (en) * 2017-10-11 2020-03-24 中国船舶重工集团公司第七一五研究所 Improved PGC modulation-demodulation detection method
CN110307780B (en) * 2019-06-25 2021-01-26 浙江理工大学 PGC phase demodulation error real-time compensation method based on iterative computation
CN110836638A (en) * 2019-10-28 2020-02-25 哈尔滨工业大学 Carrier phase delay and associated amplitude modulation elimination method in phase generation carrier arc tangent
CN110836639A (en) * 2019-10-28 2020-02-25 哈尔滨工业大学 Method for eliminating differential cross multiplication carrier delay and associated amplitude modulation of phase generation carrier

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