CN203178064U - A measuring apparatus for phase delay spectrum characteristics of wave plates - Google Patents

Abstract

The utility model discloses a measuring apparatus for phase delay spectrum characteristics of wave plates. The measuring apparatus comprises a broadband light source, wherein continuous light emitted from the broadband light source is received by a multi-wavelength photodetector, after passing through a collimator, a polarizer, two wave plates to be measured, an analyzer and an optical splitter sequentially. The two wave plates to be measured are both connected with a motor; data received by the multi-wavelength photodetector is uploaded to a data collecting card which further transmits the data to a computer, and the computer is connected with the motor. With a measuring method of the utility model, the phase delay spectrum characteristics of two unknown wave plates can be automatically measured at the same time within the range of a broad spectrum; the measuring method can not only be used for measuring the phase delay spectrum characteristics of two rotating wave plates in a rotary dual-compensator type spectroscopic ellipsometer so as to eliminate system errors caused by inaccurate calibration, but also be used for a direct calibration for the phase delay amount spectrum characteristics of the two unknown wave plates at the same time in the actual productions and researches, with the measurement results being free from influences of spectrum characteristics of the light source and the detector.

Description

The measurement mechanism of wave plate phase delay spectral characteristic

Technical field

The utility model belongs to the polarization optics detection range, particularly a kind of measurement mechanism of wave plate phase delay spectral characteristic.

Background technology

Wave plate is commonly used for the transformation device of light signal polarization state in ellipsometry or the optical measurement.The phase delay error of wave plate can produce very big influence to measurement result.Therefore, making and using in the process of wave plate, often need accurately to measure the phase delay spectral characteristic of wave plate.For example in rotation double compensation device formula wide spectrum ellipsometer (PCSCA type ellipsometer), the precise calibration of two compensator C1, C2 retardation is to realize the prerequisite of high-acruracy survey, and the operating wavelength range of two whirl compensators has material impact to the complete machine characteristic.

As everyone knows, though the whirl compensator C1 in the PCSCA type ellipsometer and C2 are designed to the broadband quarter wave plate, actual broadband quarter wave plate in the bandwidth range of considering, not always strict 90 ° of its phase-delay quantities, but certain error range is arranged; Be example with the compound zero-th order waveplates of magnesium fluoride, when spectral range was 200～1000nm, the phase-delay quantity of this wave plate is fluctuations in 60 °～130 ° scopes just.

In manufacturing and designing in the process of PCSCA type ellipsometer, the step that at first needs to carry out is exactly to wherein two compensator C1 and C2 calibrates and self calibration, namely accurately measure two compensators in the phase delay at each wavelength place, to eliminate the inaccurate systematic error of bringing of spectrometer receiving end calibration.Common calibration mode such as document [the R.W.Collins and J.Koh that adopts, J.Opt.Soc.Am.A, 16,1997 (1999)] described, namely at first measure the output photocurrent of CCD pixel, then it is done Fourier analysis, find the solution wherein each fourier coefficient respectively, apply mechanically the phase-delay quantity that certain formula is tried to achieve each compensator in the ellipsometer then.

But this scheme is subjected to the measurement wavelength coverage restriction (this instrument is applied in infrared band usually) of used fourier transform analysis instrument, the many and solution procedure relative complex of source of error.Can certainly adopt other instrument (as other commercial ellipsometer) that two compensators of rotation double compensation device formula ellipsometer are measured respectively, and then assemble, the greatest problem of this scheme is that the phase delay spectral property of compensator is restricted by the measure spectrum scope of used ellipsometer, and process is more complicated.

The method of measurement wave plate phase delay has a variety of, but often only is applicable to the wave plate phase-delay quantity of measuring under a certain specific monochromatic wavelength, can not measure the phase delay spectral characteristic of wave plate under the multi-wavelength situation simultaneously.And the measuring method that has, can but be merely able to measure the phase delay spectral characteristic of single wave plate, can not measure the phase delay spectral characteristic of two wave plates to be measured simultaneously.

Though Chinese patent CN1743796 and CN100340838C etc. all can once read the measurement data of multi-wavelength simultaneously, can't measure the phase delay spectral characteristic of two wave plates simultaneously.

The method of Chinese patent CN1632501, CN201032473Y and CN102589850A etc. also needs by the single wavelength of the each selection of monochromator, carry out the feature measurement of single wave plate to be measured, more limited in the occasion of the ease for operation that requires to measure and measuring speed.

Chinese patent (application number: 201110344206, patent name: method and Polarization Controller that broadband waveplate and realization phase delay equate), the content of this patent is how to utilize dispersion element with wideband spectrum spatially separately and be implemented in and obtain the phase delay that equates in the broad frequency range, and how to utilize this wide wave plate combined to become Polarization Controller, do not relate to the measurement problem of broadband waveplate phase delay spectral characteristic at all.

The utility model content

The purpose of this utility model is exactly in order to address the above problem, and a kind of measurement mechanism of wave plate phase delay spectral characteristic is provided, and it belongs to non-cpntact measurement, can measure two unknown wave plate phase delay spectrums in wide spectral range simultaneously automatically; Easy to use efficient, both can be used for measuring the phase delay spectral characteristic of rotating two rotating wave plates in the double compensation device formula wide spectrum ellipsometer, eliminate the inaccurate systematic error of bringing of its calibration; Can be used for carrying out simultaneously in actual production and the research work the direct calibration of the phase-delay quantity spectral characteristic of two unknown wave plates again, and measurement result is not subjected to the influence of light source and detector spectrum characteristic.

To achieve these goals, the utility model adopts following technical scheme:

A kind of measurement mechanism of wave plate phase delay spectral characteristic, comprise a wideband light source, the multi-wavelength continuous light of its outgoing is successively by behind collimating apparatus, the polarizer, first wave plate to be measured, second wave plate to be measured, analyzer and the optical splitter, receive through the multi-wavelength light electric explorer, transfer data to data collecting card after the reception, the data transmission of data collecting card is given computing machine, and described first wave plate to be measured and second wave plate to be measured are installed on the precise rotating platform of manual control.

A kind of measurement mechanism of wave plate phase delay spectral characteristic, comprise a wideband light source, the multi-wavelength continuous light of its outgoing by behind collimating apparatus, the polarizer, first wave plate to be measured, second wave plate to be measured, analyzer and the optical splitter, receives through the multi-wavelength light electric explorer successively; Described first wave plate to be measured all is connected with same motor with second wave plate to be measured or is connected respectively with two motors; The data upload that described multi-wavelength light electric explorer receives is in data collecting card, and data collecting card transfers data to computing machine, and computing machine connects motor.

Described light source is output characteristics stable continuous spectrum light source, and the spectral range of this light source can cover the phase delay spectral characteristic scope of wave plate to be measured.

Described collimating apparatus adopts by tail optical fiber and GRIN Lens and accurately locatees the optical fiber collimator that forms, and the light that is used for wideband light source is sent is transformed into collimated light.

The described polarizer and analyzer all adopt a kind of in the dichroism polarizer or the birefringence polarizer.

Described two wave plates to be measured are true zero-th order waveplates or the compound zero-th order waveplates by crystalline material or polymeric material for the delay scope is 0 °～180 ° zero-th order waveplates, especially broadband zero-th order waveplates.

Described optical splitter can adopt satisfactory color dispersion-type optical splitters such as Amici prism or grating, be used for the wavelength of multi-wavelength composite light beam is launched, and each wavelength signals that will launch is sent into the multi-wavelength light electric explorer and detected.

Described multi-wavelength light electric explorer is multi-wavelength photodiode array, photomultiplier tube array or CCD(Charge-coupled Device) linear array or area array sensor, be preferably CCD linear array or area array sensor, the multi-wavelength light current signal that is used for detecting reaches computing machine through data collecting card and carries out the data processing.

Described motor and motor driver are selected servomotor, p-m step motor or reaction stepping motor and corresponding driver thereof for use.

Described first wave plate to be measured and second wave plate to be measured are by manually rotating or being rotated by driven by motor.

Described computing machine sends pulse signal is adjusted motor through motor driver rotation status by data collecting card.

The measuring method that a kind of measurement mechanism of wave plate phase delay spectral characteristic adopts mainly comprises the steps:

Step 1: the quick shaft direction of regulating first wave plate to be measured is parallel with analyzer with the polarizer, and the quick shaft direction of second wave plate to be measured is vertical with first wave plate to be measured;

Step 2: open wideband light source, the parallel beam of the continuous wavelength of outgoing by behind collimating apparatus, the polarizer, first and second wave plates to be measured, analyzer and the optical splitter, receives through the multi-wavelength light electric explorer successively; Computing machine rotates with same angular velocity w in the same way by two wave plates to be measured of Data Control driven by motor of analyzing the data collecting card collection;

Step 3: wave plate to be measured is come with respect to the photoelectricity flow valuve collection under several absolute anglecs of rotation of reference position, by obtained the phase-delay quantity δ of any af at wavelength lambda first wave plate to be measured by phase-delay quantity formula and measuring system overall performance formula ₁, second wave plate to be measured phase-delay quantity δ ₂, and the parameter η that characterizes this wavelength place measuring system overall performance, and then obtain the phase delay spectral characteristic of two wave plates to be measured;

Step 4: according to all δ in the measurement wavelength coverage of described measurement mechanism ₁, δ ₂With the η data, corresponding δ draws ₁(λ), δ ₂(λ) and η (λ) curve, the smoothing processing of at last curve that obtains being removed " burr " further reduces error.

The concrete steps of described step 3 are: wave plate to be measured is made α and α=wt is arranged with respect to the absolute anglec of rotation note of reference position, and the initial moment of t=0 is corresponding to α=0, every anglec of rotation step delta θ, wherein 0＜Δ θ≤π/4; Data collecting card is gathered primary photoelectric current and is passed to computing machine, when driven by motor wave plate to be measured rotates a circle, all obtains at least eight group photocurrent data at each wavelength place like this; Because under the stable situation of system performance, photocurrent I(α) be to be the periodic function of π in the cycle about independent variable α; So at arbitrary wavelength place, consider emphatically that all α gets several special angle, described special angle is α=k π, k π+π/4, k π+pi/2, the value of k π+3 π/4 photocurrent I of place, k is integer and k 〉=0, is obtained the phase-delay quantity δ of random wave strong point first wave plate to be measured then by phase-delay quantity formula and measuring system overall performance formula ₁, second wave plate to be measured phase-delay quantity δ ₂, and the parameter η that characterizes this wavelength place measuring system overall performance, and then obtain the phase delay spectral characteristic of two wave plates to be measured.

The phase-delay quantity δ of first wave plate to be measured in the described step 3 ₁, second wave plate to be measured phase-delay quantity δ ₂, and the parameter η that characterizes this wavelength place measuring system overall performance, shown in following formula;

$\mathrm{\η}=\frac{1}{8}\·\left\{\begin{array}{c}I\left(\mathrm{k\π}\right)+I(\mathrm{k\π}+\frac{\mathrm{\π}}{4})+I(\mathrm{k\π}+\frac{\mathrm{\π}}{2})+I(\mathrm{k\π}+\frac{3\mathrm{\π}}{4})+\\ \sqrt{{[I\left(\mathrm{k\π}\right)+I(\mathrm{k\π}+\frac{\mathrm{\π}}{4})+I(\mathrm{k\π}+\frac{\mathrm{\π}}{2})+I(\mathrm{k\π}+\frac{3\mathrm{\π}}{4})]}^2-16\·I\left(\mathrm{k\π}\right)\·I(\mathrm{k\π}+\frac{\mathrm{\π}}{2})}\end{array}\right\}$

${\mathrm{\δ}}_1={\cos }^{-1}[I(\mathrm{k\π}+\frac{\mathrm{\π}}{2})/\mathrm{\η}-1]$

δ ₂＝cos ^-1[I(kπ)/η-1]。

The beneficial effects of the utility model:

1) measuring method of the present utility model belongs to non-cpntact measurement, can measure the phase delay spectral characteristic of two unknown broadband waveplates simultaneously, easy to use efficient, both can be used for measuring the phase delay spectrum of two rotating wave plates in the PCSCA type ellipsometer, eliminated the inaccurate systematic error of bringing of its calibration; Can be used for carrying out simultaneously in actual production and the research work the direct calibration of the phase-delay quantity of two unknown zero-th order waveplates again, and measurement result is not subjected to the influence of light source and analyzer spectral characteristic.

2) in the multi-wavelength light electric explorer under the characteristic of each probe unit and the incident intensity condition of unknown, do not need complicated Fourier analysis and find the solution and to demarcate two zero-th order waveplates to be measured rapidly and accurately simultaneously in the phase delay spectrum of waiting to investigate wave band; Simultaneously, also can obtain measuring system at the parameter η that waits to investigate the wave band serviceability, the analysis of this parameter is helped to investigate the fault of measuring system described in the utility model, and the serviceability of each building block in the analysis, calibration measurements system; For example, known and under the multi-wavelength light electric explorer spectral characteristic condition of unknown, can utilize η (λ) characteristic to demarcate, analyze the spectral characteristic of multi-wavelength light electric explorer in the spectral characteristic of wideband light source and each device loss characteristic.

3) can utilize forward and reverse rotation of motor and corresponding measurement to eliminate the measuring error that element orientation angular displacement causes, and further utilize the error correction measure to realize the quick high accuracy measurement of any zero-th order waveplates.

4) the utility model can be measured the phase delay spectral characteristic of two zero-th order waveplates simultaneously, and with respect to other measuring method, measured zero-th order waveplates phase delay is wider, both can be quarter wave plate, can not be quarter wave plate also.

Description of drawings

Fig. 1 is the device synoptic diagram of the related wave plate phase delay spectral characteristic measurement mechanism of the utility model when adopting Electric Machine Control wave plate to be measured to rotate;

Fig. 2 is the universal architecture synoptic diagram of the measurement mechanism of the related wave plate phase delay spectral characteristic of the utility model.

Wherein, 1, wideband light source, 2, collimating apparatus, 3, the polarizer, 4, first wave plate to be measured, 5, second wave plate to be measured, 6, analyzer, 7, optical splitter, 8, the multi-wavelength light electric explorer, 9, data collecting card, 10, computing machine, 11, motor.

Embodiment

The utility model is described in further detail below in conjunction with accompanying drawing and embodiment.

Innovative point of the present utility model is to adopt method for self-calibrating to realize the real-time measurement of the phase delay spectral characteristic of two unknown wave plates simultaneously.Its embodiment is as follows:

At first, the utility model need be built the measurement mechanism of wave plate phase delay spectral characteristic, realizes the purpose of this utility model by technical schemes such as method for self-calibrating and forward and reverse mensurations then.

As shown in Figure 1, a kind of measurement mechanism of wave plate phase delay spectral characteristic, comprise a wideband light source 1, the multi-wavelength continuous light of its outgoing receives through multi-wavelength light electric explorer 8 successively by behind collimating apparatus 2, the polarizer 3, first wave plate 4 to be measured, second wave plate 5 to be measured, analyzer 6 and the optical splitter 7; Described first wave plate 4 to be measured is connected with motor 11 with second wave plate 5 to be measured, and the data upload that described multi-wavelength light electric explorer 8 receives is in data collecting card 9, and data collecting card 9 transfers data to computing machine 10, computing machine 10 control motors 11.

As shown in Figure 2, a kind of measurement mechanism of wave plate phase delay spectral characteristic, comprise a wideband light source 1, the multi-wavelength continuous light of its outgoing is successively by behind collimating apparatus 2, the polarizer 3, first wave plate 4 to be measured, second wave plate 5 to be measured, analyzer 6 and the optical splitter 7, receive through multi-wavelength light electric explorer 8, described first wave plate 4 to be measured and second wave plate 5 to be measured are installed on the precise rotating platform of manual control.The data upload that described multi-wavelength light electric explorer 8 receives is in data collecting card 9, and data collecting card 9 transfers data to computing machine 10.

Described collimating apparatus 2 can adopt by tail optical fiber and GRIN Lens accurately the optical fiber collimator that forms of location etc. all the light that wideband light source 1 sends can be transformed into the optical device of collimated light (directional light) function.

Described wideband light source 1 is output characteristics stable continuous spectrum light source, and the spectral range of this light source can cover the phase delay spectral range of wave plate to be measured.

The described polarizer 3 and analyzer 6 all adopt a kind of in the dichroism polarizer or the birefringence polarizer.

Described two wave plates to be measured are true zero-th order waveplates or the compound zero-th order waveplates by crystalline material or polymeric material for the delay scope is 0 °～180 ° zero-th order waveplates, especially broadband zero-th order waveplates.

Described multi-wavelength light electric explorer 8 is multi-wavelength photodiode array, photomultiplier tube array or CCD linear array or area array sensor, is preferably CCD linear array or area array sensor.

Described motor 11 is selected servomotor, p-m step motor or reaction stepping motor and corresponding driver thereof for use.

Described optical splitter 7 can adopt satisfactory color dispersion-type optical splitters such as Amici prism or grating, be used for the wavelength of multi-wavelength composite light beam is launched, and each wavelength signals that will launch is sent into detector array and detected.

The rotation of described two wave plates to be measured except adopting motor 11 controls, also can realize by manual or alternate manner.

Type and model that described computing machine 10 and data collecting card 9 adopt are not limit, and coupling gets final product mutually.

Described computing machine 10 is by data collecting card 9 collections, computational data, and the driver of transmission pulse signal to two motor 11 is to control motor 11 with the fixed step size rotating wave plate.

Principle of work of the present utility model and the course of work are specific as follows:

Step 1: first wave plate 4 to be measured and second wave plate 5 to be measured are placed successively among the light path of the polarizer 3 of the parallel placement of direction of shaking and analyzer 6, the quick shaft direction of regulating first wave plate 4 to be measured is parallel with analyzer 6 with the polarizer 3, and the quick shaft direction of second wave plate 5 to be measured is vertical with first wave plate to be measured 4;

Step 2: open wideband light source 1, the parallel beam of the continuous wavelength of outgoing receives through multi-wavelength light electric explorer 8 successively by behind collimating apparatus 2, the polarizer 3, first wave plate 4 to be measured and second wave plate 5 to be measured, analyzer 6 and the spectroscope; Computing machine 10 drives two wave plates to be measured by data collecting card 9 control motors 11 and rotates in the same way with same angular velocity w, the initial moment of wave plate being made α with respect to the absolute anglec of rotation note of reference position and α=wt(t=0 being arranged is corresponding to α=0), every anglec of rotation step delta θ, data collecting card 9 is gathered primary photoelectric current and is passed to computing machine 10, wherein 0＜Δ θ≤π/4; When motor 11 drives wave plate to be measured rotates a circle, all can obtain at least eight group photocurrent data at each wavelength place like this.According to the correlation theory of polarization optics, the Stokes of the input in Fig. 1 or the device shown in Figure 2 and output light signal represents i.e. S _InAnd S _OutBetween satisfy following relation:

$S_{\mathrm{out}}=M_{A}R\left({-C}_2\right)M_{C2}\left({\mathrm{\δ}}_2\right)R\left(C_2\right)R\left({-C}_1\right)M_{C1}\left({\mathrm{\δ}}_1\right)R\left(C_1\right)M_p{S}_{\mathrm{in}}$

$=\left(\begin{array}{cccc}1& 1& 0& 0\\ 1& 1& 0& 0\\ 0& 0& 0& 0\\ 0& 0& 0& 0\end{array}\right)\·\left(\begin{array}{cccc}1& 0& 0& 0\\ 0& \cos C_2& -\sin C_2& 0\\ 0& \sin C_2& \cos C_2& 0\\ 0& 0& 0& 1\end{array}\right)\·\left(\begin{array}{cccc}1& 0& 0& 0\\ 0& 1& 0& 0\\ 0& 0& \cos {\mathrm{\δ}}_2& \sin {\mathrm{\δ}}_2\\ 0& 0& -\sin {\mathrm{\δ}}_2& \cos {\mathrm{\δ}}_2\end{array}\right)\·\left(\begin{array}{cccc}1& 0& 0& 0\\ 0& \cos C_2& \sin C_2& 0\\ 0& -{\sin C}_2& {\cos C}_2& 0\\ 0& 0& 0& 1\end{array}\right)\·---\left(1\right)$

$\&CenterDot;\left(\begin{array}{cccc}1& 0& 0& 0\\ 0& {\cos C}_1& -{\mathrm{<figure-callout\; id="1"\; label="sin\; C"\; filenames="HDA00003074973700011.png,HDA00003074973700012.png"\; state="\{\{state\}\}">sin</figure-callout>}C}_1& 0\\ 0& {\mathrm{<figure-callout\; id="1"\; label="sin\; C"\; filenames="HDA00003074973700011.png,HDA00003074973700012.png"\; state="\{\{state\}\}">sin</figure-callout>}C}_1& {\mathrm{<figure-callout\; id="1"\; label="cos\; C"\; filenames="HDA00003074973700011.png,HDA00003074973700012.png"\; state="\{\{state\}\}">cos</figure-callout>}C}_1& 0\\ 0& 0& 0& 1\end{array}\right)\&CenterDot;\left(\begin{array}{cccc}1& 0& 0& 0\\ 0& 1& 0& 0\\ 0& 0& {\cos \mathrm{\&delta;}}_1& \sin {\mathrm{\&delta;}}_1\\ 0& 0& {-\sin \mathrm{\&delta;}}_1& {\cos \mathrm{\&delta;}}_1\end{array}\right)\&CenterDot;\left(\begin{array}{cccc}1& 0& 0& 0\\ 0& {\mathrm{<figure-callout\; id="1"\; label="cos\; C"\; filenames="HDA00003074973700011.png,HDA00003074973700012.png"\; state="\{\{state\}\}">cos</figure-callout>}C}_1& {\mathrm{<figure-callout\; id="1"\; label="sin\; C"\; filenames="HDA00003074973700011.png,HDA00003074973700012.png"\; state="\{\{state\}\}">sin</figure-callout>}C}_1& 0\\ 0& {-\mathrm{<figure-callout\; id="1"\; label="sin\; C"\; filenames="HDA00003074973700011.png,HDA00003074973700012.png"\; state="\{\{state\}\}">sin</figure-callout>}C}_1& {\mathrm{<figure-callout\; id="1"\; label="cos\; C"\; filenames="HDA00003074973700011.png,HDA00003074973700012.png"\; state="\{\{state\}\}">cos</figure-callout>}C}_1& 0\\ 0& 0& 0& 1\end{array}\right)\&CenterDot;\left(\begin{array}{cccc}1& 1& 0& 0\\ 1& 1& 0& 0\\ 0& 0& 0& 0\\ 0& 0& 0& 0\end{array}\right)\&CenterDot;\left(\begin{array}{c}{S}_0\\ S_1\\ S_2\\ {\mathrm{<figure-callout\; id="3"\; label="S"\; filenames="HDA00003074973700012.png"\; state="\{\{state\}\}">S</figure-callout>}}_3\end{array}\right)$

In the formula (1), M _P, M _A, M _C1, M _C2Be respectively the Muller matrix of the polarizer 3, analyzer 6, first wave plate 4 to be measured and second wave plate 5 to be measured; R (C ₁), R (C ₂), R (C ₁) and R (C ₂) corresponding transformation matrix of coordinates when being first wave plate 4 to be measured, 5 rotations of second wave plate to be measured, δ ₁Be the phase-delay quantity of first wave plate 4 to be measured, δ ₂It is the phase-delay quantity of second wave plate 5 to be measured.Because the direction of shaking thoroughly of the quick shaft direction of first wave plate 4 to be measured and the polarizer 3, analyzer 6 is parallel to each other (being 0), the quick shaft direction of second wave plate 5 to be measured is vertical with first wave plate to be measured 4, and both rotate in the same way with same angular velocity w, the anglec of rotation C of first wave plate 4 to be measured ₁=wt=α, the anglec of rotation C of second wave plate 5 to be measured ₂=pi/2+α, (w is the angular velocity of wave plate rotation, and t represents Measuring Time, measures initial moment t=0 corresponding to α=0), the Stokes expression formula of then exporting light signal can further turn to:

$S_{\mathrm{out}}=\left(\begin{array}{cccc}A& A& 0& 0\\ A& A& 0& 0\\ 0& 0& 0& 0\\ 0& 0& 0& 0\end{array}\right)\&CenterDot;\left(\begin{array}{c}{S}_0\\ S_1\\ S_2\\ {\mathrm{<figure-callout\; id="3"\; label="S"\; filenames="HDA00003074973700012.png"\; state="\{\{state\}\}">S</figure-callout>}}_3\end{array}\right)=B\&CenterDot;\left(\begin{array}{c}{S}_0+S_1\\ S_0+{\mathrm{<figure-callout\; id="1"\; label="S"\; filenames="HDA00003074973700011.png,HDA00003074973700012.png"\; state="\{\{state\}\}">S</figure-callout>}}_1\\ 0\\ 0\end{array}\right)---\left(2\right)$

Wherein B is α and δ ₁, δ ₂Function, it is as follows that it embodies formula:

$B(\mathrm{\&alpha;},{\mathrm{\&delta;}}_1,{\mathrm{\&delta;}}_2)=1+({\sin }^2\mathrm{\&alpha;}+{\cos }^2\mathrm{\&alpha;}\&CenterDot;\cos {\mathrm{\&delta;}}_2)\&CenterDot;({\cos }^2\mathrm{\&alpha;}+{\sin }^2\mathrm{\&alpha;}\&CenterDot;{\cos \mathrm{\&delta;}}_1)$

$+[\frac{1}{4}\&CenterDot;{\sin }^{2}2\mathrm{\&alpha;}\&CenterDot;(1-{\cos \mathrm{\&delta;}}_1)\&CenterDot;(1-{\cos \mathrm{\&delta;}}_2)]-\frac{1}{2}\sin 2\mathrm{\&alpha;}\&CenterDot;{\sin \mathrm{\&delta;}}_1\&CenterDot;{\sin \mathrm{\&delta;}}_2---\left(3\right)$

Because at any wavelength place, the output photocurrent of the receiving end photodetector unit of measurement mechanism described in the utility model is proportional to this wavelength place output light signal S ₀The light intensity of component, namely

$I\left(\mathrm{\&alpha;}\right)=\frac{1}{4}\&CenterDot;K\&CenterDot;(S_0+S_1)\&CenterDot;B(\mathrm{\&alpha;},{\mathrm{\&delta;}}_1,{\mathrm{\&delta;}}_2)$

$=\frac{1}{2}\&CenterDot;K\&CenterDot;{\left|E_p\right|}^2\&CenterDot;B(\mathrm{\&alpha;},{\mathrm{\&delta;}}_1,{\mathrm{\&delta;}}_2)---\left(4\right)$

$=\mathrm{\&eta;}\&CenterDot;B(\mathrm{\&alpha;},{\mathrm{\&delta;}}_1,{\mathrm{\&delta;}}_2)\mathrm{\&eta;}=\frac{1}{2}\&CenterDot;K\&CenterDot;{\left|E_p\right|}^2$

Wherein K for consider that factor affecting such as detective quantum efficiency introduce less than 1 scale-up factor, E _pBe shake the thoroughly light amplitude of direction of analyzer 6.Photocurrent I is actually α herein, δ ₁, δ ₂And the function of wavelength X, be follow-up formula (6.a～6.d) and (convenience of expression of 7.a～7.c) is abbreviated as I (α) herein.This shows that the output photocurrent of detector is directly related with the light intensity of measurement mechanism receiving end light signal (this light intensity is determined by the loss of each device of measurement mechanism and the factors such as spectral characteristic of light source) and the characteristics such as quantum efficiency of detector itself.All there is certain insertion loss owing to respectively form device in the actual measurement device that the utility model relates to, and the spectral characteristic of this loss and actual wideband light source 1 possibility and uneven, so be difficult to directly obtain by simple theoretical calculating the E at each wavelength place _pValue (but these influence factors pass in time hardly change).And for the sensitive detection parts of reality, the spectral response curve of its output photocurrent is also also uneven, and namely the K value becomes with wavelength variations.Spectral response curve (no glass vision panel, 25 ℃) with the Hamamatsu company ultraviolet area array CCD of current international mainstream is example, and in the wavelength coverage of 200nm-400nm, quantum efficiency changes in the 35-65% scope.Accordingly by in the formula (4) As can be known, be difficult to directly obtain a η value accurately by the index of each device.So in the process of measuring two wave plate phase delay spectral characteristics to be measured, if can avoid the influence of η, directly record δ ₁, δ ₂Ideal; Certainly, if can record η simultaneously, and come duty and the investigation fault of further analysis measuring device with its, achieve many things at one stroke especially.Further study formula (4) and (5) for this reason, can get following regular formula:

B(α,δ ₁,δ ₂)＝B(kπ+α,δ ₁,δ ₂)＝I(α)/η＝I(kπ+α)/η （5）

This shows under the stable situation of system performance, at any one wavelength place that determines, photocurrent I(α) and B(α, δ ₁, δ ₂) all be to be the function (k is integer and k 〉=0) of π in the cycle about independent variable α, and have following relation to occur in several special angle:

B(0,δ ₁,δ ₂)＝B(kπ,δ ₁,δ ₂)＝I(0)/η＝1+cosδ ₂ （6.a）

$B(\frac{\mathrm{\&pi;}}{2},{\mathrm{\&delta;}}_1,{\mathrm{\&delta;}}_2)=B(\mathrm{k\&pi;}+\frac{\mathrm{\&pi;}}{2},{\mathrm{\&delta;}}_1,{\mathrm{\&delta;}}_2)=I\left(\frac{\mathrm{\&pi;}}{2}\right)/\mathrm{\&eta;}=1+\cos {\mathrm{\&delta;}}_1---(6.b)$

$B(\frac{\mathrm{\&pi;}}{4},{\mathrm{\&delta;}}_1,{\mathrm{\&delta;}}_2)=B(\mathrm{k\&pi;}+\frac{\mathrm{\&pi;}}{4},{\mathrm{\&delta;}}_1,{\mathrm{\&delta;}}_2)=I\left(\frac{\mathrm{\&pi;}}{4}\right)/\mathrm{\&eta;}=\frac{3}{2}+\frac{1}{2}\cos ({\mathrm{\&delta;}}_1+{\mathrm{\&delta;}}_2)---(6.c)$

$B(\frac{3\mathrm{\&pi;}}{4},{\mathrm{\&delta;}}_1,{\mathrm{\&delta;}}_2)=B(\mathrm{k\&pi;}+\frac{3\mathrm{\&pi;}}{4},{\mathrm{\&delta;}}_1,{\mathrm{\&delta;}}_2)=I\left(\frac{3\mathrm{\&pi;}}{4}\right)/\mathrm{\&eta;}=\frac{3}{2}+\frac{1}{2}\cos ({\mathrm{\&delta;}}_1-{\mathrm{\&delta;}}_2)---(6.d)$

So it is that several special angle are (as α=k π that the starting point of measuring method described in the utility model is measured exactly at arbitrary wavelength α of place, k π+π/4, k π+pi/2, k π+3 π/4 o'clock) photocurrent numerical value (k is integer and k 〉=0), (6.a～6.d) obtains the phase-delay quantity δ of this wavelength place first wave plate 4 to be measured by formula then ₁, second wave plate 5 to be measured phase-delay quantity δ ₂, and the parameter η that characterizes this wavelength place measuring system overall performance is as formula (shown in the 7.a～7.c).

$\mathrm{\&eta;}=\frac{1}{8}\&CenterDot;\left\{\begin{array}{c}I\left(\mathrm{k\&pi;}\right)+I(\mathrm{k\&pi;}+\frac{\mathrm{\&pi;}}{4})+I(\mathrm{k\&pi;}+\frac{\mathrm{\&pi;}}{2})+I(\mathrm{k\&pi;}+\frac{3\mathrm{\&pi;}}{4})+\\ \sqrt{{[I\left(\mathrm{k\&pi;}\right)+I(\mathrm{k\&pi;}+\frac{\mathrm{\&pi;}}{4})+I(\mathrm{k\&pi;}+\frac{\mathrm{\&pi;}}{2})+I(\mathrm{k\&pi;}+\frac{3\mathrm{\&pi;}}{4})]}^2-16\&CenterDot;I\left(\mathrm{k\&pi;}\right)\&CenterDot;I(\mathrm{k\&pi;}+\frac{\mathrm{\&pi;}}{2})}\end{array}\right\}---(7.a)$

${\mathrm{\&delta;}}_1={\cos }^{-1}[I(\mathrm{k\&pi;}+\frac{\mathrm{\&pi;}}{2})/\mathrm{\&eta;}-1]---(7.b)$

δ ₂＝cos ^-1[I(kπ)/η-1] （7.c）

Step 3: consider influence of measurement error, several groups of δ can calculate more in the place at same wavelength ₁, δ ₂With the η data, and get its average respectively.At last, can be according to all δ in the measurement wavelength coverage of measurement mechanism described in the utility model ₁, δ ₂With the η data, corresponding δ draws ₁(λ), δ ₂(λ) and η (λ) curve, certain algorithmic rule is set at last, the smoothing processing to the curve that obtains removes " burr " further reduces error.

The specific algorithm flow process of measuring method described in the utility model is exemplified below:

At first, configure measuring system described in the utility model according to above-mentioned measuring process, and open light source and other each building block of system.Then, etc. each parts of system stable after, can begin to measure.Setting wave plate anglec of rotation step-length is π/4; At first read the I (0) at each wavelength place in the initial moment of measurement; Then two wave plates to be measured are all rotated π/4, read the I (π/4) at each wavelength place; Again two wave plates to be measured are rotated π/4, read the I (pi/2) at each wavelength place; By that analogy, under the situation that wave plate began to rotate a circle from the initial moment, can obtain I (3 π/4), I (π), I (5 π/4), I (3 pi/2), I (7 π/4) and the I (2 π) at each wavelength place subsequently successively.For eliminating the influence of two wave plate anglec of rotation deviations to be measured etc., send to drive signal and circle by wave plate is counter, I ' (7 π/4), I ' (3 pi/2), I ' (5 π/4), the I ' that obtains each wavelength place respectively successively (π), I ' (3 π/4), I ' (pi/2), I ' (π/4) and I ' (0).For further reducing error, can calculate following root-mean-square valve AvaI (π), AvaI (π/4), AvaI (3 π/4), the AvaI (pi/2) of each wavelength place photocurrent respectively, (7.a～7.c) obtains corresponding δ by formula then ₁, δ ₂With the η data and be saved in computing machine 10.At last, δ 1(λ in the measurement wavelength coverage of measurement mechanism described in the utility model of drawing), δ 2(λ) and η (λ) curve, and carry out curve fitting, the curve that obtains is gone the smoothing processing of " burr ", further reduce error, preserve data and end operation.

$\mathrm{AvaI}\left(\mathrm{\&pi;}\right)=\sqrt{\frac{{\left[I\left(0\right)\right]}^2{\left[I\left(\mathrm{\&pi;}\right)\right]}^2+{\left[I\left(2\mathrm{\&pi;}\right)\right]}^2+{\left[I^{\&prime;}\left(\mathrm{\&pi;}\right)\right]}^2+{\left[I^{\&prime;}\left(0\right)\right]}^2}{5}}$

$\mathrm{AvaI}\left(\frac{\mathrm{\&pi;}}{4}\right)=\sqrt{\frac{{\left[I\left(\frac{\mathrm{\&pi;}}{4}\right)\right]}^2+{\left[I\left(\frac{5\mathrm{\&pi;}}{4}\right)\right]}^2+{\left[I^{\&prime;}\left(\frac{5\mathrm{\&pi;}}{4}\right)\right]}^2+{\left[I^{\&prime;}\left(\frac{\mathrm{\&pi;}}{4}\right)\right]}^2}{4}}$

$\mathrm{AvaI}\left(\frac{3\mathrm{\&pi;}}{4}\right)=\sqrt{\frac{{\left[I\left(\frac{3\mathrm{\&pi;}}{4}\right)\right]}^2+{\left[I\left(\frac{7\mathrm{\&pi;}}{4}\right)\right]}^2+{\left[I^{\&prime;}\left(\frac{7\mathrm{\&pi;}}{4}\right)\right]}^2+{\left[I^{\&prime;}\left(\frac{3\mathrm{\&pi;}}{4}\right)\right]}^2}{4}}$

$\mathrm{AvaI}\left(\frac{\mathrm{\&pi;}}{2}\right)=\sqrt{\frac{{\left[I\left(\frac{\mathrm{\&pi;}}{2}\right)\right]}^2+{\left[I\left(\frac{3\mathrm{\&pi;}}{4}\right)\right]}^2+{\left[I^{\&prime;}\left(\frac{3\mathrm{\&pi;}}{2}\right)\right]}^2+{\left[I^{\&prime;}\left(\frac{\mathrm{\&pi;}}{2}\right)\right]}^2}{4}}$

In fact, whether need to draw and match η (λ) curve can depend on actual need and decides actually herein.Because mainly be in order to investigate the fault of measuring system described in the utility model to the analysis of this parameter, and the serviceability of each building block in the analysis, calibration measurements system.For example, known and under the multi-wavelength light electric explorer 8 spectral characteristic condition of unknown, can utilize η (λ) curve and formula (4) to demarcate, analyze the spectral characteristic of multi-wavelength light electric explorer 8 in the spectral characteristic of wideband light source 1 and each device loss characteristic.

Utilize the measuring method of wave plate spectral characteristic described in the utility model, also can directly in PCSCA type ellipsometer, realize the measurement certainly of two broadband quarter wave plate phase delay spectral characteristics.At first, PCSCA type ellipsometer is set to direct mode operation, regulate the initial orientation angle α (quick shaft direction) and the polarizer 3 and analyzer 6 parallel (α=0) of first wave plate 4 to be measured, the initial orientation angle of second wave plate 5 to be measured is vertical with first wave plate to be measured 4, and both with speed, etc. step-length rotate in the same way; At arbitrary wavelength place, consider emphatically that all α gets several special angle, as α=k π, k π+π/4, k π+pi/2, the photocurrent numerical value (k is integer and k 〉=0) of k π+3 π/4 o'clock is obtained the phase-delay quantity δ of random wave strong point first wave plate 4 to be measured then by formula ₁, second wave plate 5 to be measured phase-delay quantity δ ₂, and the parameter η that characterizes this wavelength place measuring system overall performance, and then obtain the phase delay spectral characteristic of two wave plates to be measured.

The utility model is also noted that in the specific implementation the operating wavelength range that guarantees all optical components (as wideband light source 1, the polarizer 3, analyzer 6, multi-wavelength light electric explorer 8 etc.) in the measuring system described in the utility model can cover the operating wavelength range of wave plate to be measured.This realizes than being easier in actual applications.Be example with the wave plate that often adopts in the ellipsometer, the operation wavelength of such wave plate substantially all within 200nm～1100nm scope, can adopt for this reason operation wavelength at 190nm～2500nm, be furnished with the xenon lamp of high-precision regulated power supply as wideband light source 1; Adopting operation wavelength is that the quartzy wollaston prism of 200～2300nm is as the polarizer 3 and analyzer 6; Adopting operation wavelength is that the back-illuminated type area array CCD (for example shore pine FFT-CCD detector) of 200～1100nm is as multi-wavelength light electric explorer 8; Etc..

Though above-mentionedly by reference to the accompanying drawings embodiment of the present utility model is described; but be not the restriction to the utility model protection domain; one of ordinary skill in the art should be understood that; on the basis of the technical solution of the utility model, those skilled in the art do not need to pay various modifications that creative work can make or distortion still in protection domain of the present utility model.

Claims (10)

1. the measurement mechanism of a wave plate phase delay spectral characteristic, it is characterized in that, comprise a wideband light source, the multi-wavelength continuous light of its outgoing is successively by behind collimating apparatus, the polarizer, first wave plate to be measured, second wave plate to be measured, analyzer and the optical splitter, receive through the multi-wavelength light electric explorer, transfer data to data collecting card after the reception, the data transmission of data collecting card is given computing machine, and described first wave plate to be measured and second wave plate to be measured are installed on the precise rotating platform of manual control.

2. the measurement mechanism of a wave plate phase delay spectral characteristic, it is characterized in that, a kind of measurement mechanism of wave plate phase delay spectral characteristic, comprise a wideband light source, the multi-wavelength continuous light of its outgoing by behind collimating apparatus, the polarizer, first wave plate to be measured, second wave plate to be measured, analyzer and the optical splitter, receives through the multi-wavelength light electric explorer successively; Described first wave plate to be measured all is connected with same motor with second wave plate to be measured, or is connected respectively with two motors; The data upload that described multi-wavelength light electric explorer receives is in data collecting card, and data collecting card transfers data to computing machine, the computer control motor.

3. the measurement mechanism of a kind of wave plate phase delay spectral characteristic as claimed in claim 1 or 2 is characterized in that,

Described two wave plates to be measured are 0 °～180 ° zero-th order waveplates for the delay scope, and described zero-th order waveplates is by the true zero-th order waveplates of crystalline material or polymeric material or compound zero-th order waveplates.

4. the measurement mechanism of a kind of wave plate phase delay spectral characteristic as claimed in claim 1 or 2 is characterized in that,

Described collimating apparatus adopts by tail optical fiber and GRIN Lens and accurately locatees the optical fiber collimator that forms.

5. the measurement mechanism of a kind of wave plate phase delay spectral characteristic as claimed in claim 1 or 2 is characterized in that,

The described polarizer and analyzer all adopt a kind of in the dichroism polarizer or the birefringence polarizer.

6. the measurement mechanism of a kind of wave plate phase delay spectral characteristic as claimed in claim 1 or 2 is characterized in that,

Described optical splitter adopts Amici prism or grating dispersion type optical splitter.

7. the measurement mechanism of a kind of wave plate phase delay spectral characteristic as claimed in claim 1 or 2 is characterized in that,

Described wideband light source is output characteristics stable continuous spectrum light source.

8. the measurement mechanism of a kind of wave plate phase delay spectral characteristic as claimed in claim 1 or 2 is characterized in that,

Described multi-wavelength light electric explorer is multi-wavelength photodiode array, photomultiplier tube array or CCD linear array or area array sensor.

9. the measurement mechanism of a kind of wave plate phase delay spectral characteristic as claimed in claim 8 is characterized in that, described multi-wavelength light electric explorer is preferably CCD linear array or area array sensor.

10. the measurement mechanism of a kind of wave plate phase delay spectral characteristic as claimed in claim 2 is characterized in that,

Described motor is selected motor and the corresponding driver thereof of servomotor, p-m step motor or reaction stepping motor for use.

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