CN102032880A - AC (alternating current) magneto-optical modulation wide angle detection device and method - Google Patents

Abstract

The invention discloses an AC (alternating current) magneto-optical modulation wide angle detection device and method. In the invention, detection of an AC magneto-optical modulation wide angle larger than pi/2 implemented with a spectrum analysis method is proposed for the first time based on the principle of AC magneto-optical modulation and spectrum analysis, the problem in AC magneto-optical modulation wide angle detection is solved, and the detection convenience is enhanced. The method comprises the following specific steps: 1) constructing a detection light path shown in figure; 2) electrifying an AC magneto-optical modulator 3 with AC to realize AC magneto-optical modulation; 3) displaying the spectrum structure of a light intensity signal received by a photoelectric detector on a spectrum analyzer; 4) reading the amplitude value of each spectrum component in a monotonically decreasing area in a spectrum structure chart; and 5) finding a spectrum component in figure 2 corresponding to each spectrum component in the monotonically decreasing area so that a final unique modulation angle can be determined according to the read amplitude value of each spectrum component.

Description

AC magnetism optical modulation wide-angle pick-up unit and method

Technical field

The present invention relates to a kind of AC magnetism optical modulation wide-angle pick-up unit and method, belong to the technical field of Photoelectric Detection, photoelectric sensing and optical information processing.

Background technology

Magnetooptics is an ancient and unfailing subject, and it in the application in optical detection and photoelectric sensing field more and more widely; Wherein using maximum is Faraday magnetooptical effect, comprises current sensor, magnetic field sensor, magneto-optic modulator, magneto optic isolator, magneto-optic circulators etc. ^[1]Spread all over a plurality of optical fields such as light detection, light sensing, optical communication.

At present, magneto-optic ac modulation technology is widely used in fields such as angular detection, current senses.In the angular detection field, mainly be that the AC magnetism light modulation techniques is detected the variation of small angle of rotation as a kind of signal detection means, accuracy of detection can reach 10 ^-4Degree ^[2], but generally do not need bigger ac modulation angular width degree in the field.In the current sense field, often utilize the AC magnetism light modulation techniques to detect the size of high-tension current ^[3]Because the magnetic field that high-tension current produces is bigger, therefore be easy to produce greater than pi/2 to the magneto-optic memory technique of high Verdet constant even surpass the ac modulation angle of 2 π, and also do not have the relevant detection technology can detect at present greater than pi/2 and even greater than this big ac modulation angle of 2 π.This has just seriously limited the application of the magneto-optic memory technique of high Verdet constant in this field, and the magneto-optic memory technique of high Verdet constant is being better than the very little diamagnetism magneto-optic glass of Verdet constant greatly aspect the current sense detection sensitivity.Therefore the magneto-optic memory technique of high Verdet constant is applied to the high-tension current sensory field and can improves current detecting sensitivity greatly, just depend on and to detect the wide-angle that the AC magnetism optical modulation is produced greater than pi/2 and can use.This paper adopts the method for spectrum analysis, has realized this AC magnetism optical modulation wide-angle greater than pi/2 is detected, and this technology will obtain to use preferably in association areas such as detection of AC magnetism optical modulation wide-angle and high-tension current sensings.

The present invention is based on the principle of AC magnetism optical modulation and spectrum analysis, propose first to utilize the method for spectrum analysis to realize the AC magnetism optical modulation wide-angle greater than pi/2 is detected, the angular detection scope does not have the upper limit in theory, has solved AC magnetism optical modulation wide-angle a difficult problem that detects and the convenience that has strengthened detection.The invention of this patent achievement can well be applied to fields such as high-tension current sensing, magnetic field detection, the detection of magneto-optic memory technique Verdet constant, has effectively expanded the range of application of AC magnetism optical modulation.

List of references

[1] Liu Gongqiang, happy will is strong, Shen Defang etc. magnetooptics [M]. and Shanghai: Shanghai science tech publishing house, 2001:36,192 ~ 229

[2] Qian Xiaoling, normal pleasing. the application [J] of magneto-optic modulation technique in the small rotation angle precision measurement of light polarization. Capital Normal University's journal (natural science edition), 2001,22 (1): 46 ~ 49

[3] Liu Gongqiang, Zhu Liangen defends Bamda etc. dynamic Faraday effect and loss mechanism [J] thereof. and Acta Physica Sinica, 1997,46 (3): 604 ~ 611

[4] Wei Yanyu, Gong Yubin, Wang Wenxiang. the numerical evaluation [J] of the multiple argument Bessel's function in any rank. University of Electronic Science and Technology's journal, 1998,27 (2): 171 ~ 176.

Summary of the invention

Technical matters: the objective of the invention is to propose a kind of AC magnetism optical modulation wide-angle pick-up unit and method, solve the AC magnetism optical modulation wide-angle greater than pi/2 is detected problem.

Technical scheme: AC magnetism optical modulation wide-angle detection method equipment therefor of the present invention as shown in Figure 1.The light that light source sends among the figure is incident to the AC magnetism photomodulator after becoming linearly polarized light through the polarizer.The AC magnetism photomodulator is made up of the energization solenoid of built-in magnet-optical medium, and solenoid link is with alternating current i=i ₀Sin ω t is in order to produce alternating magnetic field, and magnet-optical medium is the magneto-optic memory technique of high Verdet constant, can produce the big AC magnetism optical modulation angle greater than pi/2.Be incident to analyzer through the light signal behind the AC magnetism photomodulator, the polarization direction of analyzer is vertical with the polarizer, receive by photodetector by the light intensity behind the analyzer, photodetector inputs to spectrum analyzer with the light intensity signal that obtains, and spectrum analyzer is used for analyzing and showing each spectrum component of light intensity signal and amplitude thereof.

AC magnetism photomodulator 3 passes to alternating current i=i ₀Sin ω t is as modulation signal, thus generation alternating magnetic field H=H in the solenoid ₀Sin ω t, the rotation angle that produces under the effect of alternating magnetic field by the linearly polarized light behind the polarizer 2 is (θ ₀Be AC magnetism optical modulation angle):

θ＝θ ₀?sin?ωt (1)

If through the incident intensity behind the polarizer 2 is I ₀, then according to Malus law, receiving light power is:

I＝I ₀sin ²θ＝I ₀sin ²(θ ₀sinωt) (2)

By formula (2) relative light intensity be:

$I^{\′}=I/I_0={\sin }^2\left({\mathrm{\θ}}_0\sin \mathrm{\ωt}\right)=\frac{1-\cos \left(2{\mathrm{\θ}}_0\sin \mathrm{\ωt}\right)}{2}---\left(3\right)$

Utilize Bessel's function ^[4]Formula (3) abbreviation is obtained:

$\cos \left(2{\mathrm{\&theta;}}_0\sin \mathrm{\&omega;t}\right)=J_0\left(2{\mathrm{\&theta;}}_0\right)+2\underset{n=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{J}_{2n}\left(2{\mathrm{\&theta;}}_0\right)\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000349417800011.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{n\&omega;t}---\left(4\right)$

Wherein, $J_n\left(x\right)=\underset{m=0}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{{(-1)}^m{\left(\frac{x}{2}\right)}^{2m+n}}{m!\mathrm{\&Gamma;}(m+n+1)}---\left(5\right)$

Therefore:

$\cos \left(2{\mathrm{\&theta;}}_0\sin \mathrm{\&omega;t}\right)=\underset{m=0}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{{(-1)}^m{\left({\mathrm{\&theta;}}_0\right)}^{2m}}{m!\mathrm{\&Gamma;}(m+1)}+2\underset{n=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{{(-1)}^m{\left({\mathrm{\&theta;}}_0\right)}^{2m+2n}}{m!\mathrm{\&Gamma;}(m+2n+1)}\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000349417800011.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{n\&omega;t}---\left(6\right)$

Thereby (3) formula becomes:

$I^{\&prime;}=[(\frac{1}{2}-\frac{1}{2}\underset{m=0}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{{(-1)}^m{\left({\mathrm{\&theta;}}_0\right)}^{2m}}{m!\mathrm{\&Gamma;}(m+1)})-\underset{n=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\underset{m=0}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{{(-1)}^m{\left({\mathrm{\&theta;}}_0\right)}^{2m+2n}}{m!\mathrm{\&Gamma;}(m+2n+1)}\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000349417800011.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{n\&omega;t}]---\left(7\right)$

By formula (7) as seen, comprising DC component and frequency in the light intensity signal is 2n ω (n=1,2,3 ...) a series of AC compounent, the amplitude of AC compounent is the absolute value of AC compounent coefficient.Now get modulation angle θ ₀In 14 radian scopes, the amplitude of making each spectrum component is with θ ₀Variation relation as shown in Figure 2.

As shown in Figure 2, angle θ ₀One regularly, and the amplitude of each spectrum component corresponding with it is also certain, angle θ ₀Not not simultaneously, the amplitude of each spectrum component is also different, and the frequency spectrum composition that comprises among the concrete spectrum structure figure is 2n ω (n=1,2,3 ...).With θ ₀=8 radians and θ ₀=13 radians are example, make spectrum structure figure as shown in Figure 3 and Figure 4, by Fig. 3 and Fig. 4 as seen, and θ ₀Difference, corresponding spectrum structure are also different, and θ ₀Big more, frequency spectrum is wide more.

Concrete detection step is as follows:

1) builds as shown in Figure 1 detection light path, the light that laser or collimated light source 1 send becomes linearly polarized light through the polarizer 2, this linearly polarized light is incident to AC magnetism photomodulator 3, reenter afterwards and be incident upon analyzer 4, the direction of shaking thoroughly of analyzer 4 is vertical with the polarizer 2, photodetector 5 is used for receiving light power, and spectrum analyzer 6 is used to analyze the spectrum structure that shows light intensity signal.

2) pass to alternating current in order to produce alternating magnetic field for the AC magnetism photomodulator, realize the AC magnetism optical modulation.

3) the light intensity signal spectrum structure that receives by spectrum analyzer display light electric explorer, the spectrum structure (shown in Fig. 3,4) that different AC magnetism optical modulation angles is corresponding different.Angle is big more, and frequency spectrum is wide more.And in the front end marginarium of spectrum structure figure, the range value of each spectrum component is dull downtrending with the increase of frequency, is claiming in this patent that this subregion is " the dull zone that descends " (shown in a mark among Fig. 3,4).

4) read the range value of each spectrum component in " dull descend to zone " in spectrum structure figure (shown in Fig. 3,4).

5) in Fig. 2, find with " dull descend to zone " in the corresponding spectrum component of each spectrum component, the range value of each spectrum component all has certain corresponding relation with the modulation angle, thereby can be according to the final unique controlling angle of setting the tone really of the range value of each spectrum component that has read.

Beneficial effect: according to above narration as can be known, the present invention has following characteristics:

Patent of the present invention is based on the principle of AC magnetism optical modulation and spectrum analysis, proposition utilizes the method for spectrum analysis to realize the AC magnetism optical modulation wide-angle greater than pi/2 is detected, and the angular detection scope does not have the upper limit in theory, and the invention of this patent achievement can effectively solve AC magnetism optical modulation wide-angle and detect problem and strengthened the convenience that detects.Can well be applied to fields such as high-tension current sensing, magnetic field detection, the detection of magneto-optic memory technique Verdet constant, and help to improve relevant detection sensitivity, effectively expand the range of application of AC magnetism optical modulation.

Description of drawings

Fig. 1 AC magnetism optical modulation wide-angle detection method device synoptic diagram.

Have among the figure: laser or collimated light source 1, the polarizer 2, AC magnetism photomodulator 3, analyzer 4, photodetector 5, spectrum analyzer 6.

Fig. 2 spectrum amplitude is with θ ₀Variation relation,

Fig. 3 θ ₀=8 radian time-frequency spectrum structural drawing,

Fig. 4 θ ₀=13 radian time-frequency spectrum structural drawing.

Embodiment

AC magnetism optical modulation wide-angle pick-up unit of the present invention and method equipment therefor are as shown in Figure 1.The light that laser or collimated light source 1 send among the figure is incident to AC magnetism photomodulator 3 after becoming linearly polarized light through the polarizer 2.AC magnetism photomodulator 3 is made up of the energization solenoid of built-in magnet-optical medium, and in order to produce alternating magnetic field, magnet-optical medium is the magneto-optic memory technique of high Verdet constant to solenoid link, can produce the AC magnetism optical modulation angle greater than pi/2 with alternating current.Be incident to analyzer 4 through the light signal after 3, the polarization direction of analyzer 4 is vertical with the polarizer 2, receive by photodetector 5 by the light intensity behind the analyzer 4, photodetector 5 inputs to spectrum analyzer 6 with the light intensity signal that obtains, and spectrum analyzer 6 is used for analyzing and showing each spectrum component of light intensity signal and amplitude thereof.

AC magnetism optical modulation wide-angle pick-up unit of the present invention and method, it is as follows that it specifically detects step:

1) builds as shown in Figure 1 detection light path, the light that laser or collimated light source 1 send becomes linearly polarized light through the polarizer 2, this linearly polarized light is incident to AC magnetism photomodulator 3, reenter afterwards and be incident upon analyzer 4, the direction of shaking thoroughly of analyzer 4 is vertical with the polarizer 2, photodetector 5 is used for receiving light power, and spectrum analyzer 6 is used to analyze the spectrum structure that shows light intensity signal.

2) pass to alternating current in order to produce alternating magnetic field for AC magnetism photomodulator 3, realize the AC magnetism optical modulation.

3) the light intensity signal spectrum structure that receives by spectrum analyzer display light electric explorer, the spectrum structure (shown in Fig. 3,4) that different AC magnetism optical modulation angles is corresponding different.Angle is big more, and frequency spectrum is wide more.And in the front end marginarium of spectrum structure figure, the range value of each spectrum component is dull downtrending with the increase of frequency, is claiming in this patent that this subregion is " the dull zone that descends " (shown in a mark among Fig. 3,4).

4) read the range value of each spectrum component in " dull descend to zone " in spectrum structure figure (shown in Fig. 3,4).

5) in Fig. 2, find with " dull descend to zone " in the corresponding spectrum component of each spectrum component, the range value of each spectrum component all has certain corresponding relation with the modulation angle, thereby can be according to the final unique controlling angle of setting the tone really of the range value of each spectrum component that has read.Below in conjunction with description of drawings embodiments of the invention are described in further detail, but present embodiment is not limited to the present invention, every employing similarity method of the present invention and similar variation thereof all should be listed protection scope of the present invention in.

Determine that the modulation Angle Method is as follows:

In the spectrum structure figure as Fig. 3, the spectrum component that comprises in " the dull zone that descends " is 14 ω, 16 ω, 18 ω, 20 ω, 22 ω, and their amplitude is about 0.27,0.18,0.07,0.02,0.005 respectively.In Fig. 2, find the frequency spectrum of 16 ω components, on 16 ω spectrum curves range value be 0.18 approximately just like figure in a, b, four points such as c, d, corresponding different respectively modulation angles, but b, c, pairing 18 ω of three points of d, 20 ω, three spectrum component range values of 22 ω are not 0.07,0.02,0.005, therefore b, c, three points of d can be foreclosed; And b, c, d also may occur other point later on and satisfy condition, but 24 ω and higher more spectrum component will appear in the each point afterwards, and their amplitude no longer satisfies the dull condition that descends, and therefore the each point that may occur later also will be left out.Then only remaining a point satisfies condition among Fig. 2, therefore can determine that the modulation angle is 8 radians by a point.

Claims (2)

1. AC magnetism optical modulation wide-angle pick-up unit is characterized in that this pick-up unit comprises order and the laser that is coaxially set or collimated light source (1), the polarizer (2), AC magnetism photomodulator (3), analyzer (4), photodetector (5), spectrum analyzer (6); Wherein, AC magnetism photomodulator (3) is made up of the energization solenoid of built-in magnet-optical medium, and magnet-optical medium is high Verdet constant, makes AC magnetism optical modulation angle greater than pi/2, and energization solenoid passes to alternating current i=i ₀Sin ω t is in order to produce alternating magnetic field; Analyzer (4) and the polarizer (2) polarization direction are orthogonal.

2. the detection method of an AC magnetism optical modulation wide-angle pick-up unit as claimed in claim 1, it is as follows to it is characterized in that detecting step:

1). the light that laser or collimated light source (1) send becomes linearly polarized light through the polarizer (2), this linearly polarized light is incident to AC magnetism photomodulator (3), reenter afterwards and be incident upon analyzer (4), the direction of shaking thoroughly of analyzer (4) is vertical with the polarizer (2), photodetector (5) is used for receiving light power, and spectrum analyzer (6) is used to analyze the spectrum structure that shows light intensity signal;

2). pass to alternating current in order to produce alternating magnetic field for AC magnetism photomodulator (3), realize the AC magnetism optical modulation;

3). by the light intensity signal spectrum structure of spectrum analyzer display light electric explorer reception, the spectrum structure that different AC magnetism optical modulation angles is corresponding different, angle is big more, frequency spectrum is wide more, and front end marginarium at spectrum structure figure, the range value of each spectrum component is dull downtrending with the increase of frequency, claims this subregion to be " the dull zone that descends ";

4) read the range value of each spectrum component in " dull descend to zone " in spectrum structure figure;

5) the spectrum component amplitude find in modulation angle variation relation figure with " dull descend regional " in the corresponding spectrum component of each spectrum component, the range value of each spectrum component all has certain corresponding relation with the modulation angle, thereby can be according to the final unique controlling angle of setting the tone really of the range value of each spectrum component that has read.

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