CN201149541Y - Optical phase defer precision measurement system - Google Patents

Abstract

The utility model discloses a precise optical phase retardation measurement system comprising a laser, a polarizer, a light modulator, a modulation signal source, a phase retarder under measurement, a phase compensator, an analyzer, an optical detector and a result output unit. The utility model modulates detected polarized light by adding the light modulator into an optical path to produce modulated polarized light. The result shows the unit can change the measurement of direct current zero-point into the measurement of alternating current zero-point after the filtering treatment of receiving signals, thereby accurately judging the extreme point and improving the measurement precision. The measurement system has advantages of easy and convenient measurement and accurate and reliable results, the precision can achieve Lambda/300, and the measurement system can be applied to productions of optical retardation devices such as wave plates and product inspections of sales departments.

Description

A kind of optical phase put-off precision measurement system

Technical field

The utility model relates to a kind of optical phase put-off precision measurement system, particularly relates to a kind of optical phase put-off precision measurement system of measuring optical delay devices such as wave plate that is applicable to, belongs to field of optical measuring technologies.

Background technology

Because improving constantly of industrial generation technique, people have proposed more and more higher requirement to the precision of device, optical instrument has obtained widespread use with its high-precision characteristics, the precision measurement of optical device has obtained increasing concern, aspect the optical device phase-delay measurement, the technology that present existing precision measurement system adopts has the differential automatic measurement (Hao Dianzhong of beam splitting of wave plate phase delay, Song Lianke, the differential automatic measurement of the beam splitting of wave plate phase delay, photoelectron. laser, 16 (5), 2005:601-604), its know-why as shown in Figure 1, its principle be incident light through 3 of the polarizers partially after, pass through wave plate R to be measured successively _x4 and Wollaston (Wollaston) prism 5, two outgoing beams collect by two detectors 6 respectively, through differential amplifier 7 processing and amplifying, enter computer processing system 9.The polarizer 3 and wave plate R to be measured _xBe placed on respectively on the rotatable objective table that drives by stepper motor 8.The driving pulse of stepper motor is provided by control module 9, carries out close-loop feedback control by 10 pairs of angles of two scramblers.When the vector vibration direction (x, y axle) of incident ray polarized light electric vector vibration direction and two outgoing beams of Wollaston (Wollaston) prism when becoming miter angle respectively, the energy of the two-beam that prism is divided into equates that output signal is zero or minimum.Put into testing sample Rx, adjustment makes its fast axle (or a slow axis) become miter angle with the x axle, is an equilibrium position at this moment, and the reading of computing machine still is zero or minimum.Rx rotates a circle, and comes back to the equilibrium position.If it is zero or minimum that 8 readings are arranged, this sample is a quarter wave plate, otherwise is non-standard sample.On the basis of equilibrium position, the polarizer 3 anglec of rotation α can change the position that balance is exported, subsequently by rotation R _xA β angle obtains the equilibrium position again.Read β, and utilize following theoretical formula, can obtain the phase retardation δ of sample.

$\cos \mathrm{\δ}=-\frac{\mathrm{tg}2\mathrm{\β}}{\mathrm{tg}2(\mathrm{\α}-\mathrm{\β})}$

Also have in the prior art to adopt and calculate the technology (Xu Wendong that the wave plate phase-delay quantity carries out precision measurement, Li Xishan, wave plate phase-delay quantity precision measurement new method, the optics journal, 1994,14 (10), 1096-1101), its technical schematic diagram as shown in Figure 2, to be quasi-monochromatic light incide on the rotatable polarizer 3 behind collimation its principle.With the vertical direction is the x direction, and horizontal direction is the y direction, and a folk prescription of the polarizer is to being θ.Through behind machinery-optics optically-active modulator 4, the plane of polarization of light beam is that the center swings with θ.Such polarized light becomes two linearly polarized lights that phase place is modulated, polarization relation is parallel with the y axle with x respectively after becoming 45 quarter wave plates 5 of spending by optical axis orientation and x axle.If the optical axis of testing sample 6 is parallel with the y axle with x, two-beam will directly be superimposed upon on original phase differential the phase place of sample with the mode process sample of o light and e light so.Two-beam by the printing opacity direction be 45 the degree analyzers 7 after interfere.The square-wave signal that adjustment polarizer position angle obtains detector 8 is zero (available lock-in amplifier detects), this moment is not if add modulation, interference will occur in extreme point (bright spot or dim spot), and the substitution following formula can obtain the phase value δ of sample from the angle of polarizer rotation.

$\mathrm{\δ}=-2\mathrm{\θ}-\frac{\mathrm{\π}}{2}$ (bright spot), or $\mathrm{\δ}=-2\mathrm{\θ}+\frac{\mathrm{\π}}{2}$ (dim spot)

The problem and shortage that above-mentioned two prior aries exist is:

1, all be indirect metering system, measure the corner of compensating device when extreme point occurring earlier, be converted to relevant phase information again, measuring error is big, mechanism's complexity, instrument cost height;

2, measurement result is subjected to instrument collimation, the influence of debuging error such as coaxial is very big;

3. when measuring the extreme point light intensity, the differential automatic measurement system of the beam splitting of wave plate phase delay does not add modulation, directly measures the light intensity of direct current dim spot, and measuring accuracy is low; Wave plate phase-delay quantity precision measurement system adds a rotatable machinery-optics optically-active modulator, and complex structure is debug and required height, and error is bigger.

The utility model content

The purpose of this utility model is to provide a kind of optical phase put-off precision measurement system, the utility model is a kind of photoelectricity hybrid system, can be used for the phase delay of optical delay devices such as wave plate is carried out precision measurement, also can be used for producing optical phase put-off amount arbitrarily.The uniqueness of this utility model is the measurement that can directly measure the optical phase put-off amount, has compared its remarkable advantages with other measuring methods by indirect amount conversion.Adopt optical modulations to measure the extinction position, improved signal to noise ratio (S/N ratio), measuring accuracy is greatly improved.Not high, simple to operate to experiment condition and environment requirement, be easy to commercialization.

The purpose of this utility model realizes by technical schemes such as optical modulation and optical compensations, describes design proposal of the present utility model and technical characterictic thereof below in conjunction with accompanying drawing.

Fig. 3 is a schematic diagram of the present utility model.System by laser instrument L, polarizing prism P, photomodulator E, modulating signal source M, phase delay device S to be measured, tired (Soleil) compensator C of rope, analyzing prism A, photo-detector D, signal processing circuit and as a result output unit O etc. form.

The azimuthal coordinates of system is defined as: direction of beam propagation is the z axle, the direction of shaking thoroughly of polarizer P, analyzer A is along the x axle, ξ that inducts after photomodulator E powers up, the η direction is consistent with the fast and slow axis direction of phase delay device S to be measured and compensator C, becomes the miter angle (see figure 4) with the x axle.

The laser beam of laser instrument L radiation becomes linearly polarized light by polarizing prism P, injects photomodulator E.Photomodulator can adopt modulation systems such as electric light, magneto-optic or acousto-optic, adds sinusoidal voltage by modulating signal source M, and the phase delay of two orthogonal polarisation state of its emergent light will be subjected to the modulation of impressed voltage signal, forms to exchange to change.The outgoing polarized light of modulator has added the phase delay of device under test through phase delay device S to be measured in its polarization state, inject tired (Soleil) compensator C of rope again.The effect of tired (Soleil) compensator of rope is similar to a continuously adjustable zero-th order waveplates of phase-delay quantity.By regulating tired (Soleil) compensator of rope, can obtain phase delay arbitrarily.From the light beam of compensator outgoing again by analyzing prism A, thereby make the variation of polarized light phase place be converted to the energy variation of analyzer outgoing beam.The light intensity of outgoing beam can be expressed as

$I=I_0{\cos }^2\left(\frac{{\mathrm{\δ}}_C+{\mathrm{\δ}}_S+{\mathrm{\δ}}_E}{2}\right)=I_0-I_0{\sin }^2\left(\frac{{\mathrm{\δ}}_C+{\mathrm{\δ}}_S+{\mathrm{\δ}}_E}{2}\right)$

δ wherein _E, δ _S, δ _CBe respectively the phase delay of tired (Soleil) compensator C of photomodulator E, phase delay device S to be measured and rope, I ₀Be incident intensity.

The emergent light of analyzer is received by photo-detector D, and after the processing such as filtering amplification through signal processing circuit, the result is presented on the oscillograph O.If do not add modulation signal, i.e. δ _E=0 o'clock, when the phase delay sum of the phase delay of device under test and compensator equals π, i.e. δ _S+ δ _C=π, the luminous energy of outgoing is zero from analyzer, this is called full remuneration, also cries the extinction position.By regulating tired (Soleil) compensator of rope, seek the extinction position.Phase delay δ in this position by compensator _cCan obtain the phase-delay quantity δ of device under test _s=π-δ _c

The utility model utilization is carried out the mode that optical modulation adds optical compensation to polarized light and is carried out the precision measurement of device under test optical phase put-off.

In the measurement of device under test optical phase put-off, need carry out the judgement of extinction position, promptly seeking output intensity is zero position, this position can be described as the direct current zero point of output intensity.Owing to add the influence of parasitic light and the restriction of the responding range of power meter own, direct current is difficult to accurate mensuration zero point.The utility model adopts the mode of optical modulation, adds the sinusoidal modulation signal of certain frequency on modulator, and then the phase delay of photomodulator generation is

δ _E=Ksin ω t, wherein, K is a constant, ω is a frequency modulating signal

And output intensity correspondingly becomes

$I=I_0-I_0{\sin }^2(\frac{{\mathrm{\δ}}_C+{\mathrm{\δ}}_S}{2}+\frac{K}{2}\sin \mathrm{\ωt})$

$=\frac{I_0}{2}\{1+\cos ({\mathrm{\δ}}_S+{\mathrm{\δ}}_C)[J_0\left(K\right)+2\underset{n=1}{\overset{\∞}{\mathrm{\Σ}}}{J}_{2n}\left(K\right)\cos \left(2\mathrm{n\ωt}\right)]-\sin ({\mathrm{\δ}}_S+{\mathrm{\δ}}_C)[2\underset{n=1}{\overset{\∞}{\mathrm{\Σ}}}{J}_{2n-1}\left(K\right)\cos (2n-1)\mathrm{\ωt}\left]\right\}$

When full remuneration, δ _S+ δ _C=π, the 3rd is 0 in the following formula braces, promptly the odd harmonic component in the signal disappears, only remaining even-order harmonic composition, the interchange zero point of Here it is output intensity.Because the high order component value is very little, can neglect the high-order even-order harmonic usually during processing, only stays second harmonic, and the full remuneration condition is become: all the odd harmonic components in the signal disappear only remaining second harmonic component.Signal processing circuit detects the frequency spectrum of outgoing signal, and the position that disappears when fundamental component is the extinction position.Utilize this characteristic, the measurement at direct current zero point is converted to the measurement that exchanges zero point,, thereby accurately judge the extinction position, realize high-acruracy survey according to detected two frequency multiplication compositions.Because the frequency of signal source is highly stable, measuring system adds the arrowband frequency-selecting amplifier, obtains very high signal to noise ratio (S/N ratio), and the judgement precision of extinction position is improved greatly.

In the utility model, realize the optical compensation of phase place by regulating tired (Soleil) compensator of rope.

The effect of tired (Soleil) compensator of rope is similar to a zero-th order waveplates that phase-delay quantity is adjustable.Form with a parallel wafers B by paired crystal wedge A and A '.A and A ' two optical axises all are parallel to the refraction seamed edge, and crystal wedge A can make it to do parallel mobile with final motion screw, the optical axis of parallel wafers B and the vertical (see figure 5) of crystal wedge A.When crystal wedge A translation, in the Zone Full of their full contacts, the gross thickness of two crystal wedges is in increase and decrease, A and A ' form the piezoid of a variable thickness, can make between the thickness of this thickness and following thin slice and produce difference arbitrarily, produce in 0～2 π scope phase delay arbitrarily between o light and the e light thereby make.The phase-delay quantity that light produces after by compensator is proportional to thickness change amount Δ h, also is proportional to the translational movement Δ L of crystal wedge.Scale-up factor between phase delay and the translational movement is relevant with optical source wavelength, should be earlier to the compensator linear scaled before measurement.The translational movement that only need read tired (Soleil) compensator of extinction point rope during measurement can obtain corresponding phase-delay quantity according to calibration coefficient, and simple to operation, the result is stable.

For achieving the above object, the technical solution adopted in the utility model is:

A kind of optical phase put-off precision measurement system, comprise laser instrument, the polarizer, photomodulator, modulating signal source, phase delay device to be measured, phase compensator, analyzer, photo-detector, output unit as a result, it is characterized in that light that described laser instrument sends successively through showing the output result by output unit as a result after the described polarizer, photomodulator, phase delay device to be measured, phase compensator, analyzer, photo-detector, the signal processing circuit, described modulating signal source is connected by signal wire with described photomodulator.

Described photomodulator is a KD*P crystal current photomodulator, and modulation system is vertically modulation, and described modulating signal source is a sinusoidal modulation signal.

Described modulation signal source frequency is 2kHz, and described signal processing circuit frequency filtering is 4kHz.

Described phase compensator is a Soleil compensator.

The plane of incidence crystal wedge of described Soleil compensator is equipped with final motion screw, makes it to do parallel moving relative to the plane of incidence by regulating described final motion screw.

The beneficial effects of the utility model are:

1. what optical modulation of the present utility model added that in fact the optical compensation scheme carry out is the direct measurement of phase delay, compares with other measuring methods by indirect amount conversion, and measuring accuracy has remarkable advantages.And judge by using modulated polarized light to carry out extinction point in the scheme, use tired (Soleil) compensator of rope to carry out phase compensation, will modulate and compensate two kinds of mode of action separate processes, eliminated the measurement result problem of unstable that mutual interference brings.The integrated measurement accuracy of system reaches λ/300 (to the 632.8nm wavelength), and repeatable accuracy is in 0.3%.

2. measuring system has been given full play to the superiority of modulated polarized light, the measurement of direct current zero point (quadrature details in a play not acted out on stage, but told through dialogues), is converted to the measurement that exchanges zero point.Add the arrowband frequency-selecting amplifier, obtain very high signal to noise ratio (S/N ratio).

3. the utility model adopts tired (Soleil) compensator of rope, even have compensator fast and slow axis and ξ, the η axle does not overlap, with situations such as measuring beam out of plumb, by the calibration before measuring, these errors all do not exert an influence to measurement result, have improved the accuracy of measuring, and have reduced the difficulty of installing and locating yet.Compensator can provide in 0～2 π scope phase delay arbitrarily, therefore is applicable to the measurement of multiple wave plate phase-delay quantities such as standard wave plate such as 1/2 wave plate, quarter wave plate and various non-standard wave plates.

The optical phase put-off precision measurement system of making according to such scheme, can be used for the phase delay of optical delay is carried out precision measurement, also can be used for producing optical phase put-off amount arbitrarily, also can carry out the measurement of geometric sense such as thickness, position angle, refractive index and physical quantity after the expansion, and tired (Soleil) compensator of rope is demarcated.This utility model measuring accuracy height, not high, simple to operate to experiment condition and environment requirement, be easy to commercialization.

Description of drawings

The differential automatic measuring principle figure of the beam splitting of Fig. 1 wave plate phase delay;

1. laser instrument 2. diaphragms 3. polarizers 4. wave plate Rx5. Wollaston to be measured (Wollaston) prisms 6. detectors 7. differential amplifiers 8. stepper motors 9. computer processing systems 10. scramblers;

Fig. 2 wave plate phase-delay quantity precision measurement schematic diagram;

1. quasi-monochromatic source 2. collimating apparatuss 3. polarizers 4. machineries-optics optically-active modulator 5.1/4 wave plate 6. testing samples 7. analyzers 8. detectors;

Fig. 3 is the utility model schematic diagram;

Tired (Soleil) compensator of L-laser instrument, P-polarizing prism, E-photomodulator, M-modulating signal source, S-phase delay device to be measured, C-rope, A-analyzing prism, D-photo-detector, O-signal processing circuit and output unit as a result

Fig. 4 is the azimuthal coordinates regulation diagram of system in the utility model;

Fig. 5 is tired (Soleil) the compensator structure figure of rope.

Embodiment

Specific embodiment of the utility model is now described in conjunction with the accompanying drawings.Wherein the device of Fig. 3 employing is: it is 632.8nm that laser instrument L can adopt wavelength, and power is the He-Ne laser instrument of 2mw.It is 10 that polarizer P and analyzer A can adopt extinction ratio ⁵, the Glan of aperture＞10mm-Taylor's polarizing prism.Photomodulator E can adopt KD ^*The vertical modulation system of P crystal is as modulator.Modulation signal is a sinusoidal voltage, and the voltage-regulation scope is: 600～2000V, modulating frequency is: 2kHz.Tired (Soleil) compensator C of rope can adopt quartz material, and operating wavelength range is 200～2000nm, and the wedge scope of moving horizontally is 0～30mm, and mobile accuracy is 1 μ m, and clear aperture is more than 10mm.Photo-detector D can adopt photodiode to carry out opto-electronic conversion and detection.According to the signal processing circuit of modulating frequency design coupling, the modulating frequency frequency-doubled signal that photo-detector is received carries out sending into output unit as a result after the filter amplifying processing, and the frequency filtering of signal processing circuit is 4kHz.As shown in Figure 4, the azimuthal coordinates of system is defined as: direction of beam propagation is the z axle, and the direction of shaking thoroughly of polarizer P, analyzer A is along the x axle, the ξ that inducts after photomodulator E powers up, the η direction is consistent with the fast and slow axis direction of phase delay device S to be measured and compensator C, becomes miter angle with the x axle.

The laser beam of laser instrument L radiation becomes linearly polarized light by polarizing prism P, injects electrooptic modulator E.Electrooptic modulator is by the vertical modulation system of KD*P crystal by adopting, and M adds sinusoidal voltage by modulating signal source, and the phase delay of two orthogonal polarisation state of its emergent light will be subjected to the modulation of impressed voltage signal, forms to exchange to change.The outgoing polarized light of modulator has added the phase delay of device under test through phase delay device S to be measured in its polarization state, inject tired (Soleil) compensator C of rope again.The effect of tired (Soleil) compensator of rope as shown in Figure 5 is similar to a continuously adjustable zero-th order waveplates of phase-delay quantity.By regulating tired (Soleil) compensator of rope, can obtain phase delay arbitrarily.From the light beam of compensator outgoing again by analyzing prism A, thereby make the variation of polarized light phase place be converted to the energy variation of analyzer outgoing beam.The emergent light of analyzer is received by photo-detector D, and after the processing such as filtering amplification through signal processing circuit, the result is presented on the oscillograph O.When the phase delay sum of the phase delay of device under test and compensator equaled π, the luminous energy of outgoing was zero from analyzer, and this is called full remuneration, also cries the extinction position.By regulating tired (Soleil) compensator of rope, seek the extinction position.The position that fundamental component disappears in output signal is the extinction position.Phase delay δ in this position by compensator _cCan obtain the phase-delay quantity δ of device under test _s=π-δ _c

Realization of the present utility model is described for example, has described above-mentioned instantiation.But other variations of the present utility model and modification; it will be apparent to those skilled in the art that, in the essence of the disclosed content of the utility model and any modification/variation in the cardinal rule scope or imitate conversion all to belong to claim protection domain of the present utility model.

Claims (5)

1. optical phase put-off precision measurement system, comprise laser instrument, the polarizer, photomodulator, modulating signal source, phase delay device to be measured, phase compensator, analyzer, photo-detector, output unit as a result, it is characterized in that light that described laser instrument sends successively through showing the output result by display unit as a result after the described polarizer, photomodulator, phase delay device to be measured, phase compensator, analyzer, photo-detector, the signal processing circuit, described modulating signal source is connected by signal wire with described photomodulator.

2. the system as claimed in claim 1 is characterized in that described photomodulator is a KD*P crystal current photomodulator, and modulation system is vertically modulation, and described modulating signal source is a sinusoidal modulation signal.

3. system as claimed in claim 1 or 2 is characterized in that described modulation signal source frequency is 2kHz, and described signal processing circuit frequency filtering is 4kHz.

4. the system as claimed in claim 1 is characterized in that described phase compensator is a Soleil compensator.

5. system as claimed in claim 4 is characterized in that the plane of incidence crystal wedge of described Soleil compensator is equipped with final motion screw, makes it to do parallel moving relative to the plane of incidence by regulating described final motion screw.

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