CN105954014B - A kind of middle infrared waveplate bit phase delay accurate measurement method based on double PEM - Google Patents

A kind of middle infrared waveplate bit phase delay accurate measurement method based on double PEM Download PDF

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Publication number
CN105954014B
CN105954014B CN201610560092.8A CN201610560092A CN105954014B CN 105954014 B CN105954014 B CN 105954014B CN 201610560092 A CN201610560092 A CN 201610560092A CN 105954014 B CN105954014 B CN 105954014B
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waveplate
infrared
modulators
middle infrared
difference frequency
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CN105954014A (en
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张瑞
王志斌
李克武
李晓
张志勇
解琨阳
薛鹏
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North University of China
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North University of China
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/02—Testing optical properties

Abstract

The present invention relates to the field of measuring technique of middle infrared waveplate bit phase delay, more particularly to a kind of middle infrared waveplate bit phase delay accurate measurement method based on double PEM, be it is a kind of modulated using two bullet optical modulator difference frequencies, can be achieved low speed, it is high-precision in infrared bit phase delay measuring method；By mid-infrared laser device, the polarizer, PEM1 modulators, infrared waveplate in tested, PEM2 modulators, analyzer, infrared point probe is arranged in order composition optical path, PEM1 modulators and the modulation of PEM2 modulators difference frequency are reduced modulating frequency by double PEM drive control circuits, infrared point probe is set effectively to be detected, and difference frequency signal is supplied to digital lock-in amplifier, digital lock-in amplifier amplifies the modulated signal that infrared point probe obtains into horizontal lock, obtain the amplitude of frequency of phase locking signal, the bit phase delay of tested middle infrared waveplate is obtained finally by computer digital animation；Present invention is mainly applied in terms of middle infrared waveplate.

Description

A kind of middle infrared waveplate bit phase delay accurate measurement method based on double PEM
Technical field
The present invention relates to the field of measuring technique of middle infrared waveplate bit phase delay, more specifically, is related to a kind of based on double The middle infrared waveplate bit phase delay accurate measurement method of PEM, is that one kind is modulated using two bullet optical modulator difference frequencies, is achievable low Infrared bit phase delay measuring method in fast, high-precision.
Background technology
Wave plate plays an important role in many fields, and wave plate retardation measurement accuracy directly determines to be measured Measurement accuracy.But in middle infrared waveplate also without the higher feasible method of measurement accuracy, but middle infrared waveplate is in some fields There is very big application potential, for example solar magnetic field observation in recent years is extended to infrared band in 8~14 μm, it is expected infrared in utilizing Wave band can obtain the advantage of the Zeeman split separations of bigger, and Magnetic Field is obtained by directly measuring split separation.But middle infrared band Accurately measurement facing challenges first are the problem of middle infrared band wave plate retardation accurately measure to solar magnetic field.The wave band Polarization measurement method is at home or foreign countries all rarely have report, thus currently without ripe e measurement technology method as ginseng Examine.Due to middle infrared band also not as visible ray and near infrared band have maturation compensating device and electro-optical modulation device, because The test system can only rely on rotating wave plate method and spectral scanning method to carry out bit phase delay measurement at present for this.Wherein spectral scanning method Usually there is degree of precision when measuring 1/2 wave plate, and rotating wave plate method has many do not know in element rotary course Factor can cause the error of luminous intensity measurement, so as to influence the precision of measurement.And middle infrared band is there are light signal is weaker, background Noise is high, and the detectivity of detector is low, the unfavorable factors such as naked eyes are invisible in addition so that error analysis is more difficult.
In recent years progressively development and perfect bullet light modulation techniques (photoelastic-modulator, PEM), in being Mutually measuring method provides new thinking to infrared band high precision position late.But high precision position phase retardation survey is carried out using PEM at present Amount method mainly uses single PEM, and tested bit phase delay is mutually obtained by locking, but due to fast (the tens of KHz- numbers of PEM modulating frequencies Hundred KHz), modulated optical signal frequency is the several times of PEM modulating frequencies again, so in infrared detector can not effectively detect, this It also limit detected with high accuracy of this method in middle infrared waveplate bit phase delay.The advantages of present invention considers PEM for this is with The problems such as speed of infrared detector, propose to reduce modulating frequency using the method for two PEM difference frequencies modulation, while red in realization The high-acruracy survey of outer wave plate retardation.
The content of the invention
It is fast for existing list PEM modulating speeds, it can not be applied in the measurement of middle infrared waveplate bit phase delay, propose for this Modulating frequency is reduced using the method for two PEM difference frequencies modulation, by the high accuracy for locking infrared waveplate bit phase delay in mutually realization Measurement.
In order to solve the above-mentioned technical problem, the technical solution adopted in the present invention is：
A kind of middle infrared waveplate bit phase delay accurate measurement method based on double PEM, by mid-infrared laser device, the polarizer, PEM1 modulators, tested middle infrared waveplate, PEM2 modulators, analyzer, infrared point probe are arranged in order composition optical path, PEM1 modulators and the modulation of PEM2 modulators difference frequency are reduced modulating frequency by double PEM drive control circuits, make infrared point probe It can effectively be detected, and difference frequency signal is supplied to digital lock-in amplifier, digital lock-in amplifier is to infrared point probe The modulated signal of acquisition is amplified into horizontal lock, is obtained the amplitude of frequency of phase locking signal, is obtained finally by computer digital animation The bit phase delay of infrared waveplate in tested.
The amplitude for obtaining frequency of phase locking signal refers to obtain 1 times of difference frequency amplitudeWith 2 times of difference frequency amplitudes In above-mentioned, f1And f2The respectively modulation driving frequency of PEM1 modulators and PEM2 modulators.
By 1 times of difference frequency amplitudeWith 2 times of difference frequency amplitudesIt is divided by unstable to surveying to eliminate mid-infrared light source itself The influence of amount.
When not being put into tested middle infrared waveplate, pass through optical path and obtain 1 times of difference frequency amplitude and 2 times of difference frequency amplitudesAfter tested middle infrared waveplate is added, pass through optical path and obtain 1 times of difference frequency amplitudeWith 2Times difference frequency width ValueWith reference to be not put into it is tested in infrared waveplate and being put into be tested in infrared waveplate 1 times of difference frequency amplitude and 2 times of difference frequencies Amplitude can accurately obtain tested middle infrared waveplate bit phase delay, to overcome PEM1 modulators and the phase modulation of PEM2 modulators to prolong Slow amplitude δ0PEM1And δ0PEM2The defects of can not accurately measuring.
Specially：
Step 1, measure when not placing tested middle infrared waveplate first：
Step 2, the tested middle infrared waveplate of addition measure 1 times of difference frequency amplitudeWith 2 times of difference frequency amplitudes
Step 3, byObtain tested middle infrared waveplate bit phase delay.
The bullet luminescent crystal of the PEM1 modulators and PEM2 modulators uses zinc selenide crystal.
Compared with prior art, the advantageous effect of present invention is that：
1st, modulating frequency is reduced by two PEM difference frequencies modulation so that infrared detector can be detected effectively in common；
2nd, using the PEM of zinc selenide, ensure there is good transmitance in middle infrared band；
3rd, by the way of 1 times of difference frequency amplitude of phase and 2 times of difference frequency amplitudes are locked at the same time, by being divided by, elimination mid-infrared light is derived from Influence of the body shakiness to measurement；
4th, the method by measuring 1 times of difference frequency amplitude and 2 times of difference frequency amplitudes when not placing tested middle infrared waveplate, accurately MeasureSolve δ0PEM1And δ0PEM2The influence to measurement can not accurately be obtained.
Brief description of the drawings
The embodiment of the present invention is described in further detail below by attached drawing.
Fig. 1 is the connection diagram of the present invention.
In figure：1 be mid-infrared laser device, 2 be the polarizer, 3 be PEM1 modulators, 4 be it is tested in infrared waveplate, 5 be PEM2 modulators, 6 be analyzer, 7 be infrared point probe, 8 be digital lock-in amplifier, 9 be double PEM drive control circuits, 10 be computer.
Embodiment
The invention will be further described for example below combination attached drawing.
Refering to Fig. 1, a kind of middle infrared waveplate bit phase delay device for accurately measuring based on double PEM, it is red in test system Outer laser 1, the polarizer 2, PEM1 modulators 3, tested middle infrared waveplate 4, PEM2 modulators 5, analyzer 6, infrared point detection Device 7, digital lock-in amplifier 8, double PEM drive control circuits 9 and computer 10 are formed.Mid-infrared laser device 1 has passed sequentially through Inclined device 2, PEM1 modulators 3, tested middle infrared waveplate 4, PEM2 modulators 5, analyzer 6 and infrared point probe 7 form measurement Light path；The double PEM difference frequency signals provided according to double PEM drive control circuits 9, digital lock-in amplifier 8 is to infrared point probe 7 The modulated signal of acquisition is amplified into horizontal lock, and the position that tested middle infrared waveplate is obtained finally by 10 data processing of computer is mutually prolonged Late.
In this embodiment, the higher zinc selenide crystal of infrared transmittivity in the bullet luminescent crystal use of PEM1 and PEM2.
In this embodiment, the modulating frequency of PEM1 and PEM2 are respectively f1=50.1KHz, f2=50.0KHz, 1 times of difference frequency (f1-f2)=100Hz, 2 times of 2 (f of difference frequency1-f2)=200Hz, more former PEM1 and PEM2 various driving frequencies reduces by 2 quantity Level.
In addition, the modulating frequency of PEM1 and PEM2 can be reasonably selected according to explorer response speed and actual requirement.
In x-axis method to be as follows with reference to 0 ° of direction, specific scheme：
Mid-infrared laser 1 is by the modulated Stokes parameters S of whole optical pathoutFor：
Sout=MP2MPEM2MXMPEM1MP1Sin (3)
Wherein, Sin=[Iin,Qin,Uin,Vin,]T,Sout=[Iout,Qout,Uout,Vout,]T；MP1、MPEM1、MX、MPEM2With MP2The respectively polarizer 2, PEM1 modulators 3,6 corresponding mueller matrix of tested wave plate 4, PEM2 modulators 5 and analyzer：
Wherein, δxFor tested middle infrared waveplate bit phase delay amount, δ0PEM1And δ0PEM2The modulation phase of respectively PEM1 and PEM2 Position Peak retardation, f1And f2The modulation driving frequency of respectively PEM1 and PEM2.
Since detector can only obtain Stokes parameters SoutIn IOUT, therefore detector detection light intensity and Bessel functions Expand into：
Wherein, m is odd number, and n is even number, Jx(y) it is xth level Bessel functions under corresponding y, A=0.5@n1=n2= 0, other situations A=1.
Since infrared detector 7 is difficult to detect in high-frequency modulation signal, and double PEM are measured and high frequency section is not required, because This (4) are after saving high frequency：
From (5), 1 times of difference frequency (f after modulation1-f2) amplitudeWith 2 times of 2 (f of difference frequency1-f2) amplitudeRespectively For：
In this embodiment, modulated 1 times of difference frequency (f1-f2)=100Hz amplitudes are I100Hz, 2 times of 2 (f of difference frequency1-f2)= The amplitude of 200Hz is I200Hz。
Wherein, it is 1 times of difference frequency (f of raising as far as possible1-f2) amplitudeWith 2 times of 2 (f of difference frequency1-f2) amplitudeInto And detectivity and signal-to-noise ratio are improved, measurement accuracy is improved, δ in this method0PEM1And δ0PEM2Value preferably 2~3 between Value.
According to (6) formula, can be obtained by digital lock-in amplifier 8WithIt is derived to eliminate mid-infrared light Influence of the body shakiness to measurement, is divided by using 1 times of difference frequency amplitude and 2 times of difference frequency amplitudes to eliminate, by (6) Shi Ke get：
Formula (7) is the formula of infrared waveplate bit phase delay in measurement.
But due to δ0PEM1And δ0PEM2Can not accurately it obtain, therefore in formula (7)Can not Accurately obtain, in order to eliminate the influence, first measure when not placing tested middle infrared waveplate 4, can be obtained not according to (7) formula When having tested middle infrared waveplate 4：
Wherein,With1 times of difference frequency amplitude and 2 times of difference frequency width when not placing tested middle infrared waveplate 4 respectively Value.
Being tested middle infrared waveplate bit phase delay according to (7) formula and (8) Shi Ke get is：
, can be according to formula in this embodimentTested middle infrared waveplate position is obtained mutually to prolong Late.
Only presently preferred embodiments of the present invention is explained in detail above, but the present invention is not limited to above-described embodiment, Within the knowledge of a person skilled in the art, can also be made on the premise of present inventive concept is not departed from each Kind change, various change should all be included in the protection scope of the present invention.

Claims (3)

  1. A kind of 1. middle infrared waveplate bit phase delay accurate measurement method based on double PEM, it is characterised in that：By mid-infrared laser Device, the polarizer, PEM1 modulators, tested middle infrared waveplate, PEM2 modulators, analyzer, infrared point probe are arranged in order structure Into optical path, PEM1 modulators and the modulation of PEM2 modulators difference frequency are reduced modulating frequency by double PEM drive control circuits, are made red Outer point probe can be detected effectively, and difference frequency signal is supplied to digital lock-in amplifier, and digital lock-in amplifier is to red The modulated signal that outer point probe obtains is amplified into horizontal lock, the amplitude of frequency of phase locking signal is obtained, finally by computer number The bit phase delay of tested middle infrared waveplate is obtained according to processing；
    The amplitude for obtaining frequency of phase locking signal includes not being put into the amplitude obtained during tested middle infrared waveplate and adds tested The amplitude obtained after middle infrared waveplate；
    When not being put into tested middle infrared waveplate, pass through optical path and obtain 1 times of difference frequency amplitudeWith 2 times of difference frequency amplitudesAfter tested middle infrared waveplate is added, pass through optical path and obtain 1 times of difference frequency amplitudeWith 2 times of difference frequency amplitudesWith reference to be not put into it is tested in infrared waveplate and being put into be tested in infrared waveplate 1 times of difference frequency amplitude and 2 times of difference frequency width Value can accurately obtain tested middle infrared waveplate bit phase delay, to overcome the phase modulation of PEM1 modulators and PEM2 modulators to postpone Amplitude δ0PEM1And δ0PEM2The defects of can not accurately measuring；
    Specially：
    Step 1, measure when not placing tested middle infrared waveplate first：
    Step 2, the tested middle infrared waveplate of addition measure 1 times of difference frequency amplitudeWith 2 times of difference frequency amplitudes
    Step 3, byObtain tested middle infrared waveplate bit phase delay；
    In above-mentioned,f 1 Withf 2 The respectively modulation driving frequency of PEM1 modulators and PEM2 modulators.
  2. 2. a kind of middle infrared waveplate bit phase delay accurate measurement method based on double PEM according to claim 1, its feature It is：By 1 times of difference frequency amplitudeWith 2 times of difference frequency amplitudesIt is divided by eliminate mid-infrared light source itself shakiness to measurement Influence.
  3. 3. a kind of middle infrared waveplate bit phase delay accurate measurement method based on double PEM according to claim 1, its feature It is：The bullet luminescent crystal of the PEM1 modulators and PEM2 modulators uses zinc selenide crystal.
CN201610560092.8A 2016-07-15 2016-07-15 A kind of middle infrared waveplate bit phase delay accurate measurement method based on double PEM Expired - Fee Related CN105954014B (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110261070A (en) * 2019-07-05 2019-09-20 北京航空航天大学 A kind of light ball modulator caliberating device and method based on compound Bezier calibration function

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
"光弹调制差频偏振测量及误差分析";王志斌等;《光学精密仪器》;20130430;877-883 *
"弹光调制器准单色光波偏振测量与仿真";高婷婷;《光学散射学报》;20131230;404-409 *
"弹光调制型成像光谱偏振仪中的高精度偏振信息探测研究";陈友华;《物理学报》;20130219;第2页左栏第2段，第3部分，以及图2 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110261070A (en) * 2019-07-05 2019-09-20 北京航空航天大学 A kind of light ball modulator caliberating device and method based on compound Bezier calibration function
CN110261070B (en) * 2019-07-05 2020-07-03 北京航空航天大学 Photoelastic modulator calibration device and method based on composite Bessel calibration function

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