CN102565725A - Device and method for measuring alternating Faraday magnetic declination angle by using signal spectrum - Google Patents
Device and method for measuring alternating Faraday magnetic declination angle by using signal spectrum Download PDFInfo
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- CN102565725A CN102565725A CN2012100729506A CN201210072950A CN102565725A CN 102565725 A CN102565725 A CN 102565725A CN 2012100729506 A CN2012100729506 A CN 2012100729506A CN 201210072950 A CN201210072950 A CN 201210072950A CN 102565725 A CN102565725 A CN 102565725A
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Abstract
The invention relates to a device and a method for measuring an alternating Faraday magnetic declination angle by using a signal spectrum. The method comprises the following steps of: theoretically calculating a one-to-one corresponding relation curve between ratios of signal amplitude values at the base frequency to signal amplitude values at the dual frequency and amplitude values of Faraday magnetic declination angles; supplying a fixed optical rotary angle by using an output of an alternating Faraday coil through a standard optical rotary pipe, acquiring a changed optical signal subjected to photoelectric conversion after a fixed angle change is produced, performing spectrum analysis on the acquired signal, and calculating the ratio of the signal amplitude value at the base frequency to the signal amplitude value at the dual frequency; searching an amplitude value of the corresponding Faraday magnetic declination angle on the determined relation curve according to the determined ratio, and precisely determining the Faraday magnetic declination angle. The device has a simple structure; and according to the method, one-time positioning is realized, and repeated adjustment for a mechanical structure is not required. The alternating Faraday magnetic declination angle can be measured in real time, the measurement range is large, influence of high-frequency harmonic on a measurement result is eliminated completely, and a possibility is supplied to development of a novel current sensor.
Description
Technical field
The present invention relates to a kind of measuring technique, particularly a kind of device and method that utilizes signal frequency spectrum measuring alternation faraday magnetic declination.
Background technology
Faraday effect propose nearly 1 in half a century, obtained widely using, especially in current sensor, optoisolator and fields such as magneto-optic modulator, chemical composition analysis.In it was used, the measurement of faraday's magnetic declination was the core and the basis of technology always.
When a branch of linearly polarized light during through the magneto-optic material in the magnetic field; Its polarization direction can deflect; Its yawing moment is only relevant with magnetic direction and irrelevant with the direction of propagation of light; The size of deflection angle is calculated by Faraday effect:
; Wherein Φ is faraday's magnetic declination; V is the Field constant, and B is a magnetic field intensity, and L is the effective length that light is propagated along magnetic direction in medium.
So far, the method for measuring faraday's magnetic declination mainly contains 3 kinds, is respectively angle compensation method, method of approximation and double beam interferometry.The angle compensation method is simple in structure, but measuring accuracy is low, and it is bigger influenced by the mechanical rotation precision; The method of approximation measurement range is little, only is applicable to small angle measurement, and limitation is big, can't eliminate the influence of higher hamonic wave fully; The double beam interferometry complex structure, cost is high, and is high to the light path accuracy requirement.
Summary of the invention
The method precision that The present invention be directed to present measurement faraday magnetic declination is low, and the problem that measurement range is little has proposed a kind of device and method that utilizes signal frequency spectrum measuring alternation faraday magnetic declination, realizes the measurement to faraday's magnetic declination from a new angle.To faraday's magnetic declination of alternation, through the frequency spectrum of analytic signal, the relation between binding signal frequency spectrum and the faraday's magnetic declination reaches the purpose of measuring faraday's magnetic declination.This method is simple in structure, and measuring accuracy is high, and measurement range is big, has eliminated the error that high-frequency harmonic causes measurement result fully.
Technical scheme of the present invention is: a kind of device that utilizes signal frequency spectrum measuring alternation faraday magnetic declination; Comprise light source, the polarizer, faraday's coil, standard polarization tube, analyzer, photodetector, amplifier, signals collecting and signal processing unit, display successively; The optical axis of the polarizer and analyzer transfers to mutually orthogonal position, and faraday's coil is the alternating current driving of ω by frequency.
Said light source is a semiconductor laser light resource.
The said method of utilizing signal frequency spectrum measuring alternation faraday magnetic declination comprises the device that utilizes signal frequency spectrum measuring alternation faraday magnetic declination, specifically comprises the steps:
1) Theoretical Calculation goes out the amplitude relation curve one to one of ratio and faraday's magnetic declination of fundamental frequency and two frequency multiplication place signal amplitudes, opening relationships curve map;
2) utilize in the device of signal frequency spectrum measuring alternation faraday magnetic declination; The linearly polarized light of the fixedly direction of vibration that obtains behind the process polarizer; Under the modulation of faraday's coil; The direction of vibration of linearly polarized light produces swing, again through a standard polarization tube, through obtaining the light signal of an alternation behind the analyzer;
The light signal of the alternation that obtains 3) step 2) becomes the electric signal of alternation through photodetector; After the electric signal of alternation amplifies signal through amplifier again; By signals collecting and signal processing unit collection and carry out Fourier transform (FFT); Obtain the frequency spectrum of signal, and calculate the ratio of the signal amplitude at fundamental frequency and two frequency multiplication places;
4) according to the ratio of step 3) gained amplitude, at ratio A and faraday's magnetic declination Φ of the signal amplitude of fundamental frequency shown in the step 1) and two frequencys multiplication
0Graph of a relation in, find the faraday magnetic declination Φ corresponding with the ratio of this amplitude
0, realize the measurement of faraday's magnetic declination.
Said step 2) the standard polarization tube in can make polarization direction rotational fixation angle [alpha]=6.46 degree through the linearly polarized light of faraday's coil outgoing.
Beneficial effect of the present invention is: the present invention utilizes the device and method of signal frequency spectrum measuring alternation faraday magnetic declination; Technology through digital signal processing improves measuring accuracy; Eliminated the error that high-frequency harmonic causes measurement result fully, measuring method is simple in structure, and measurement range is big.
Description of drawings
Fig. 1 utilizes the schematic diagram of device of signal frequency spectrum measuring alternation faraday magnetic declination for the present invention;
Fig. 2 for fundamental frequency of the present invention and two frequency-doubled signal amplitudes than A and faraday's magnetic declination φ
0Graph of relation;
Fig. 3 measures electric signal analogous diagram in the device of alternation faraday magnetic declination for the present invention utilizes signal spectral analysis;
Fig. 4 measures the spectrogram of simulate signal in the device of alternation faraday magnetic declination for the present invention utilizes signal spectral analysis.
Embodiment
The schematic diagram of device that utilizes signal frequency spectrum measuring alternation faraday magnetic declination as shown in Figure 1, device comprises light source 1, the polarizer 2, faraday's coil 4, standard polarization tube 5, analyzer 6, photodetector 7, amplifier 8, signals collecting and signal processing unit 9, display 10 successively.Light source is a semiconductor laser light resource.The optical axis of the polarizer 2 and analyzer 6 transfers to mutually orthogonal position.Faraday's coil 4 is alternating current 3 drivings of ω by frequency.It is polarization direction rotation alpha=6.46 degree of the linearly polarized light of 534nm that standard polarization tube 5 can make wavelength.
In this device, the magnetic declination that faraday's coil produces can be expressed as:
，（1）
Φ wherein
0Be the maximum magnetic flux drift angle.Can know that by Malus law when the deflection angle that departs from quadrature position when the polarizer and analyzer was θ, emergent light I light intensity was:
I wherein
0For passing through analyzer light intensity before.
In this device, the light signal of output can be expressed as:
This signal is carried out the FFT conversion, obtain the spectrogram of signal shown in the formula (3), calculate the ratio of the signal amplitude of its fundamental frequency and two frequencys multiplication, the signal ratio A that promptly ω/2 Π and 2 ω/(2 Π) locates.Different in theory Φ
0Corresponding different A values, Φ
0And the relation curve between the A is as shown in Figure 2.Photodetector 7 converts light signal into electric signal, and electric signal is gathered by signals collecting and signal processing unit 9.The analogous diagram of the electric signal that arrives for system acquisition shown in Figure 3; Simulate signal among Fig. 3 is carried out the spectrogram (as shown in Figure 4) that spectrum analysis obtains this signal; The ratio of the signal amplitude of fundamental frequency and two frequencys multiplication in the signal calculated frequency spectrum finds the corresponding faraday's magnetic declination Φ of ratio of this amplitude then in Fig. 2
0, realize the measurement of faraday's magnetic declination.
A kind of method of utilizing signal spectral analysis to measure alternation faraday magnetic declination, at first Theoretical Calculation goes out the amplitude relation curve one to one of ratio and faraday's magnetic declination of fundamental frequency and two frequency multiplication place signal amplitudes; Through opto-electronic conversion, convert light signal into electric signal, gather electric signal and signal is carried out spectrum analysis, try to achieve the ratio of the signal amplitude at fundamental frequency and two frequency multiplication places; According to the ratio of confirming that obtains, on the relation curve of confirming, seek the amplitude of corresponding faraday's magnetic declination.
Claims (4)
1. device that utilizes signal frequency spectrum measuring alternation faraday magnetic declination; It is characterized in that; Comprise light source (1), the polarizer (2), faraday's coil (4), standard polarization tube (5), analyzer (6), photodetector (7), amplifier (8), signals collecting and signal processing unit (9), display (10) successively; The optical axis of the polarizer (2) and analyzer (6) transfers to mutually orthogonal position, and faraday's coil (4) is alternating current (3) driving of ω by frequency.
2. according to the said device that utilizes signal frequency spectrum measuring alternation faraday magnetic declination of claim 1, it is characterized in that said light source (1) is a semiconductor laser light resource.
3. according to the said method of utilizing signal frequency spectrum measuring alternation faraday magnetic declination of claim 1, comprise the device that utilizes signal frequency spectrum measuring alternation faraday magnetic declination, it is characterized in that, specifically comprise the steps:
1) Theoretical Calculation goes out the amplitude relation curve one to one of ratio and faraday's magnetic declination of fundamental frequency and two frequency multiplication place signal amplitudes, opening relationships curve map;
2) utilize in the device of signal frequency spectrum measuring alternation faraday magnetic declination; The linearly polarized light of the fixedly direction of vibration that obtains behind the process polarizer (2); Under the modulation of faraday's coil (4); The direction of vibration of linearly polarized light produces swing, again through a standard polarization tube (5), through obtaining the light signal of an alternation behind the analyzer (6);
The light signal of the alternation that obtains 3) step 2) becomes light signal through photodetector (7) electric signal of alternation; After the electric signal of alternation amplifies signal through amplifier again; Gathered and carry out Fourier transform (FFT) by signals collecting and signal processing unit (9); Obtain the frequency spectrum of signal, and calculate the ratio of the signal amplitude at fundamental frequency and two frequency multiplication places;
4) according to the ratio of step 3) gained amplitude, at ratio A and faraday's magnetic declination Φ of the signal amplitude of fundamental frequency shown in the step 1) and two frequencys multiplication
0Graph of a relation in, find the faraday magnetic declination Φ corresponding with the ratio of this amplitude
0, realize the measurement of faraday's magnetic declination.
4. according to the said method of utilizing signal frequency spectrum measuring alternation faraday magnetic declination of claim 3; It is characterized in that said step 2) in standard polarization tube (5) can make polarization direction rotational fixation angle [alpha] through the linearly polarized light of faraday's coil (4) outgoing=6.46 degree.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106052594A (en) * | 2016-05-10 | 2016-10-26 | 河南师范大学 | Method of measuring magneto optic fiber rotation angle by utilizing fiber grating laser optical beat frequency |
| CN107643438A (en) * | 2017-09-14 | 2018-01-30 | 重庆大学 | Optical current sensor and its current measuring method based on Faraday magnetooptical effect |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN200993639Y (en) * | 2006-12-19 | 2007-12-19 | 中国海洋大学 | Faraday effect measuring instrument |
| WO2008065196A2 (en) * | 2006-11-30 | 2008-06-05 | North Sensor A/S | Faraday effect current sensor |
| CN102158284A (en) * | 2011-03-17 | 2011-08-17 | 电子科技大学 | Light signal polarization direction determination and power equalization system |
| CN102253350A (en) * | 2011-05-03 | 2011-11-23 | 西安交通大学 | Switching arc magnetic field measurement device and method based on magneto-optic imaging |
-
2012
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2008065196A2 (en) * | 2006-11-30 | 2008-06-05 | North Sensor A/S | Faraday effect current sensor |
| WO2008065196A3 (en) * | 2006-11-30 | 2008-12-11 | North Sensor As | Faraday effect current sensor |
| CN200993639Y (en) * | 2006-12-19 | 2007-12-19 | 中国海洋大学 | Faraday effect measuring instrument |
| CN102158284A (en) * | 2011-03-17 | 2011-08-17 | 电子科技大学 | Light signal polarization direction determination and power equalization system |
| CN102253350A (en) * | 2011-05-03 | 2011-11-23 | 西安交通大学 | Switching arc magnetic field measurement device and method based on magneto-optic imaging |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106052594A (en) * | 2016-05-10 | 2016-10-26 | 河南师范大学 | Method of measuring magneto optic fiber rotation angle by utilizing fiber grating laser optical beat frequency |
| CN107643438A (en) * | 2017-09-14 | 2018-01-30 | 重庆大学 | Optical current sensor and its current measuring method based on Faraday magnetooptical effect |
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