CN104296875A - Light beam polarization degree measuring device and method - Google Patents

Abstract

The invention discloses a light beam polarization degree measuring device and method. The measuring device comprises an optical element substrate, a rotary table and two light beam intensity detectors. An optical element is placed on the rotary table. Light to be measured is emitted into the optical element substrate, the light beam incidence angle is adjusted through the rotary table, the reflecting and transmission light intensity of the optical element at different incidence angles is measured, and according to the Fresnel formula, the polarization degree of an incidence light beam is obtained by calculating. The device and method have the advantages of being simple, low in cost, high in measuring accuracy, wide in application range and the like.

Description

A kind of beam polarization degree measurement mechanism and method

Technical field

The present invention relates to the technical field that beam polarization degree is measured, be specifically related to a kind of light beam polarization characteristic measuring device and method.

Background technology

Light wave is a kind of shear wave, and the direction of vibration of its light wave vector is perpendicular to the direction of propagation of light.According to the situation of change of light wave vector direction of vibration, light can be divided into natural light and polarized light, polarized light can be further divided into line polarisation, circularly polarized light, elliptically polarized light again.For linearly polarized light, usually the component vibrated perpendicular to the plane of incidence is called s component (s light), and the component being parallel to plane of incidence vibration is called p component (p light).Polarization characteristic is one of key property of light beam, and polarisation of light information detection is used widely in fields such as atural object remote sensing, uranology, medical science and Military Application.

Polarisation of light characteristic measurement method is also a lot, such as patent CN 102243104 A, a kind of device of measuring properties of polarized light in real time, it adopts unpolarized Amici prism, half-wave plate, 2 polarization splitting prisms and No. 4 photo-detectors, realized the real-time measurement of incident polarization light characteristic by the measurement of 4 tunnel luminous powers, comprise position angle and the polarization extinction ratio information of polarized light.Patent CN102435418 A, ArF laser optics thin-film component versatile polarimeter and method, this device is made up of ArF excimer laser, ArF excimer laser beam-expanding collimation device, iris, the polarizer, beam splitter, sample stage pivotal support arm, can measure the polarized reflectance of difform optical thin film element when different incidence angles, transmissivity, reflection Untwisting Effect and transmission Untwisting Effect, and measurement of polarization characteristic method wherein is also adopt analyzer (Rochon prism polaroid) and detector integrated processes to measure simultaneously.Patent CN 102933944 A proposes a kind of system and method for measuring beam polarization.This optical system comprises polarization beam splitting assembly and picture element matrix, and polarization beam splitting assembly is made up of polarization beam apparatus and birefringence element, for input beam is divided into predetermined number, the beam component each other with predetermined polarisation relation.Picture element matrix, for detecting the intensity distributions in the light beam incided on it, analyzes the intensity distributions in each output beam component, determines the Stokes' parameter of the expression polarization profile of input beam, thus determines the polarization characteristic of input beam.

Light beam polarization characteristic measurement method in sum all adopts multiple polarimetry optical element and complicated measurement structure, has measurement cost high, measures the shortcomings such as slow.

Summary of the invention

The object of the invention is to design a kind of beam polarization degree measurement mechanism and method, realized the high-acruracy survey of beam polarization degree by simple mechanism.

The technical solution used in the present invention is: a kind of beam polarization degree measurement mechanism, and described measurement mechanism comprises optical element, angle controller, the first Light-Intensity Detector, the second Light-Intensity Detector and data handling system; Described optical element is arranged on angle controller, is regulated the incident angle of light beam to be measured by angle controller, measures the beam intensity through optical element transmittance and reflectance respectively, use E respectively by the first Light-Intensity Detector and the second Light-Intensity Detector _tand E _rrepresent; Data handling system is carried out process to measurement result and is obtained incident light polarization degree information.

Described optical element should be selected to reflect the optical base-substrate treating light-metering with transmission, absorption and the scattering loss for the treatment of light-metering are known, optical base-substrate should be thin to reduce absorption loss, can be that 3mm is thick or thinner, optical base-substrate size should be greater than treats that light-metering is incident to three times of the spot size on optical element.

Described angle controller is mainly used in regulating beam incident angle to be measured, except employing turntable, other also can be adopted can to change the device of incident angle of light, as with the stand for optical lens of angular adjustment or fixed angle stand for optical lens.

The first described Light-Intensity Detector and the second Light-Intensity Detector are for measuring the transmitted light after optical element and intensity of reflected light, thus calculate polarization degree to be measured, Light-Intensity Detector can be energy meter also can be laser powermeter or other can the detector of measuring beam intensity, as photodiode, photomultiplier etc.

Incident angle auxiliary conditioning unit is provided with before described optical element, when the incident illumination through small holes is incident upon on optical element, reflected light equally when small holes incident angle of light be zero degree, except employing aperture, also additive method can be adopted to make incident angle accurately be positioned to zero degree, if incident angle is zero degree when not having an interference fringe by the transmitted light after optical element, or after light-metering, adding two apertures, incident light is through two apertures, optical element is added between incident light and contiguous aperture, if optical element transmitted light is equally through two apertures, incident angle of light is zero degree.

Can take multiple measurements during identical incident angle, to effectively reduce degree of polarization measuring error, namely general three measurements can meet the demands.

By regulating the angle controller being provided with optical element, different incidence angles is taken multiple measurements, thus the polarization degree to be measured that when calculating different incidence angles, measurement obtains, to effectively reduce degree of polarization measuring error.

In addition, the present invention also provides a kind of beam polarization degree measuring method, it is characterized in that measuring process is as follows:

Step 1, adjustment treat that light-metering is with incidence angle θ ₁be incident on optical element, θ ₁scope be 0 ° of < θ ₁< 90 °, selects incident angle determined value according to actual conditions;

Step 2, to measure optical element transmittance and reflectance respectively by the first Light-Intensity Detector and the second Light-Intensity Detector treat measured light intensity;

Step 3, data handling system are according to incidence angle θ ₁the optical element transmittance and reflectance obtained with the first Light-Intensity Detector and the second Light-Intensity Detector measurement treat that measured light intensity is in conjunction with degree of polarization computing formula, calculates polarization degree to be measured;

Step 4, judging whether to increase the transmitted light of once treating light-metering and intensity of reflected light is measured, is return step 3, no, continues next step;

Step 5, judging whether the measurement of increase by angle of light degree to be measured, is return step 1, no, terminates.

Further, described incidence angle θ ₁controlled by angle controller and regulate, refraction angle θ ₂obtained by following formulae discovery:

${\mathrm{\&theta;}}_2={\sin }^{-1}\left(\frac{n}{n_{\mathrm{\&lambda;}}}\sin \left({\mathrm{\&theta;}}_1\right)\right).$

Polarization degree computing method to be measured are as follows:

(1) will treat that the component vibrated perpendicular to the plane of incidence and the component being parallel to plane of incidence vibration are resolved in light-metering, usually the component vibrated perpendicular to the plane of incidence is called s light, and the component being parallel to plane of incidence vibration is called p light, then treat that measured light intensity is expressed as:

I＝I _s+I _p

(2) calculating incident angle is θ ₁time optical element treat the reflection and transmission coefficients of light-metering, described optical wavelength to be measured is λ, and optical element refractive index is at that wavelength n _λ, beam propagation medium refraction index to be measured is n, and the incident angle that light beam is incident to optical element is θ ₁, refraction angle is θ ₂, then according to fresnel's law, treat that the s light of light-metering and p light are expressed as in the transmissivity of the optical element plane of incidence and reflectivity:

$r_s=\frac{{\sin }^2({\mathrm{\&theta;}}_1-{\mathrm{\&theta;}}_2)}{{\sin }^2({\mathrm{\&theta;}}_1+{\mathrm{\&theta;}}_2)}$

$r_p=\frac{{\tan }^2({\mathrm{\&theta;}}_1-{\mathrm{\&theta;}}_2)}{{\tan }^2({\mathrm{\&theta;}}_1+{\mathrm{\&theta;}}_2)}$

$t_s=\frac{\sin {2\mathrm{\&theta;}}_1\sin {2\mathrm{\&theta;}}_2}{{\sin }^2({\mathrm{\&theta;}}_1+{\mathrm{\&theta;}}_2)}$

$t_p=\frac{\sin {2\mathrm{\&theta;}}_1\sin {2\mathrm{\&theta;}}_2}{{\sin }^2({\mathrm{\&theta;}}_1+{\mathrm{\&theta;}}_2){\cos }^2({\mathrm{\&theta;}}_1-{\mathrm{\&theta;}}_2)}$

Wherein, t _sfor the transmissivity at the optical element plane of incidence of s light; t _pfor p light is in the transmissivity of the optical element plane of incidence; Rs is the reflectivity of s light at the optical element plane of incidence; r _pfor p light is at the reflectivity of the optical element plane of incidence;

(3) calculating incident angle is θ ₁time optical element treat total reflectivity and the transmissivity of light-metering, optic thickness is d, according to the propagation principle of light, is expressed as through the total transmittance of optical element and reflectivity:

$R_s=r_s+t_s^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_s^{2i-1}$

$R_p=r_p+t_p^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_p^{2i-1}$

$T_s=t_s^2+t_s^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_s^{2i}$

$T_p=t_p^2+t_p^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_p^{2i}$

R _s+T _s＝1

R _p+T _p＝1

Wherein, T _sfor s light is through the total transmittance of optical element; T _pfor p light is through the total transmittance of optical element; R _sfor s light is through the total reflectivity of optical element; R _pfor p light is through the total reflectivity of optical element;

(4) incident angle that basis calculates is θ ₁time optical element treat light-metering reflectivity and transmissivity, and measure the energy of reflection light that obtains and transmitted light energy, obtain polarization degree to be measured; Beam intensity through optical element transmittance and reflectance is expressed as:

E _T＝I _s×T _s+I _p×T _p

E _R＝I _s×R _s+I _p×R _p

Wherein, E _tthrough the beam intensity of optical element transmission; E _rthrough the beam intensity of optical element reflection;

Therefore obtain incident light polarization degree P according to degree of polarization definition to be expressed as:

$P=\frac{|I_s-I_p|}{I}=\left|\frac{E_T(R_s+R_p)-E_R(T_s+T_p)}{(R_p-R_s)(E_T+E_R)}\right|.$

Further, can consider surface scattering loss S and the optical absorption loss A of optical element in degree of polarization computation process, then the s light after considering optical element loss and p light total transmittance and total reflectivity are expressed as:

$R_s=r_s(1-S)+t_s^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_s^{2i-1}{(1-S)}^{2i+1}{(1-A)}^{2i}$

$R_p=r_p(1-S)+t_p^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_p^{2i-1}{(1-S)}^{2i+1}{(1-A)}^{2i}$

$T_s=t_s^2(1-A){(1-S)}^2+t_s^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_s^{2i}{(1-S)}^{2(i+1)}{(1-A)}^{2i+1}$

$T_p=t_p^2(1-A){(1-S)}^2+t_p^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_p^{2i}{(1-S)}^{2(i+1)}{(1-A)}^{2i+1}$

R _s+T _s+S+A＝1

R _p+T _p+S+A＝1

Then beam polarization degree P computing formula is as follows:

$P=\frac{|I_s-I_p|}{I}=\left|\frac{[E_T(R_s+R_p)-E_R(T_s+T_p)](1-S-A)}{(R_s{T}_p-R_p{T}_s)(E_T+E_R)}\right|.$

The present invention compared with prior art tool has the following advantages:

(1) the present invention only adopts a slice optical element and two beam intensity detectors namely can realize the measurement of beam polarization degree, and measurement mechanism is simple;

(2) degree of polarization that namely the present invention can realize the incident beam of different wave length by the replacing optical element corresponding with light beam wavelength to be measured and detector is measured, and measurement range is wide;

(3) measuring accuracy of the present invention depends primarily on the relative accuracy of optical element incident angle degree of regulation and beam intensity detection, and angular adjustment absolute precision is more than 1 ‰, the relative detection precision of intensity detector is also more than 1 ‰, and therefore degree of polarization absolute measurement precision of the present invention can reach 1 ‰ levels;

Accompanying drawing explanation

Fig. 1 is beam polarization degree measurement mechanism light path schematic diagram of the present invention;

Fig. 2 is beam polarization degree measuring method process flow diagram of the present invention.

Embodiment

Below will be described in further detail a kind of beam polarization degree measurement mechanism of the present invention and method.

Be illustrated in figure 1 the optical path figure of degree of polarization measurement mechanism, comprise light source 0, optical element 1, angle demodulator 2, adopts turntable in this example, the first Light-Intensity Detector 3, second Light-Intensity Detector 4, data handling system 5 and incident angle auxiliary conditioning unit 6, adopt aperture in the present embodiment.Aperture is positioned at the light path rear of light source 0, for regulating incident angle of light to angle on target; Optical element 1 is positioned on turntable, and light beam incides on optical element 1 after small holes, and a part of light beam is transmitted on the first Light-Intensity Detector 3 through optical element 1, and another part light beam is reflexed on the second Light-Intensity Detector 4 by optical element 1.Data handling system 5 receives the data from the first Light-Intensity Detector 3 and the second Light-Intensity Detector 4, after the routine processes of inside, reads degree of polarization measured value.

In this example, light beam to be measured is 193nm excimer laser output beam, and known laser device output beam is complete nonpolarized light, i.e. beam polarization degree P=0; Laser Output Beam is incident on the optical element 1 that is arranged on turntable, and optical element 1 is calcium fluoride substrate, is 1.5015, absorption loss A=1% in the refractive index at 193nm wavelength place, scattering loss S=0.9%; Turntable adopts precision to be 0.023 °, the NEWPORT turntable URS75BCC of carryover 360 °; Aperture adopts the adjustable aperture of Thorlabs company, and hole diameter is minimum can be adjusted to 1mm; The transmittance and reflectance beam intensity of optical element 1 is measured by the first Light-Intensity Detector 3 of same model and the second Light-Intensity Detector 4, Light-Intensity Detector selects the J-25MT-10kHz pyroelectricity energy meter of Coherent company, can represent with the first energy meter and the second energy meter respectively; Data handling system adopts computing machine.In order to convenience of calculation, regulate calcium fluoride substrate to make incident angle equal Brewster angle, under Brewster angle calcium fluoride substrate reflected light in without p polarized light, i.e. R _p=0; Define according to Brewster angle:

$\tan {\mathrm{\&theta;}}_b=\frac{n_{\mathrm{\&lambda;}}}{n}---\left(1\right)$

In air, the Brewster angle of calcium fluoride substrate under the incident light of 193nm is 56.3 °, i.e. incidence angle θ ₁=56.3 °, the s light in calcium fluoride substrate-incident face and p light reflectivity under this angle, transmittance calculation are as follows:

$r_s=\frac{{\sin }^2({\mathrm{\&theta;}}_1-{\mathrm{\&theta;}}_2)}{{\sin }^2({\mathrm{\&theta;}}_1+{\mathrm{\&theta;}}_2)}$

$r_p=\frac{{\tan }^2({\mathrm{\&theta;}}_1-{\mathrm{\&theta;}}_2)}{{\tan }^2({\mathrm{\&theta;}}_1+{\mathrm{\&theta;}}_2)}---\left(2\right)$

$t_s=\frac{\sin {2\mathrm{\&theta;}}_1\sin {2\mathrm{\&theta;}}_2}{{\sin }^2({\mathrm{\&theta;}}_1+{\mathrm{\&theta;}}_2)}$

$t_p=\frac{\sin {2\mathrm{\&theta;}}_1\sin {2\mathrm{\&theta;}}_2}{{\sin }^2({\mathrm{\&theta;}}_1+{\mathrm{\&theta;}}_2){\cos }^2({\mathrm{\&theta;}}_1-{\mathrm{\&theta;}}_2)}$

Wherein, t _sfor the transmissivity at optical element 1 plane of incidence of s light; t _pfor p light is in the transmissivity of optical element 1 plane of incidence; r _sfor s light is at the reflectivity of optical element 1 plane of incidence; r _pfor p light is at the reflectivity of optical element 1 plane of incidence;

Refraction angle ${\mathrm{\&theta;}}_2={\sin }^{-1}\left(\frac{n}{n_{\mathrm{\&lambda;}}}\sin \left({\mathrm{\&theta;}}_1\right)\right),$ Then result of calculation is:

r _s＝14.86％,t _s＝85.14％,r _p＝0,tp＝100％

After two-sided multiple reflections and transmission, reflectivity when not considering optical element loss and transmissivity are expressed as:

$R_s=r_s+t_s^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_s^{2i-1}$

$R_p=r_p+t_p^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_p^{2i-1}---\left(3\right)$

$T_s=t_s^2+t_s^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_s^{2i}$

$T_p=t_p^2+t_p^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_p^{2i}$

Wherein, T _sfor s light is through the total transmittance of optical element 1; T _pfor p light is through the total transmittance of optical element 1; R _sfor s light is through the total reflectivity of optical element 1; R _pfor p light is through the total reflectivity of optical element 1;

Result of calculation is: R _s=25.88%, T _s=74.12%, R _p=0, T _p=100%;

When considering that the absorption of calcium fluoride substrate and scattering loss back reflection rate and transmissivity are expressed as:

$R_s=r_s(1-S)+t_s^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_s^{2i-1}{(1-S)}^{2i+1}{(1-A)}^{2i}$

$R_p=r_p(1-S)+t_p^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_p^{2i-1}{(1-S)}^{2i+1}{(1-A)}^{2i}---\left(4\right)$

$T_s=t_s^2(1-A){(1-S)}^2+t_s^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_s^{2i}{(1-S)}^{2(i+1)}{(1-A)}^{2i+1}$

$T_p=t_p^2(1-A){(1-S)}^2+t_p^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_p^{2i}{(1-S)}^{2(i+1)}{(1-A)}^{2i+1}$

Result of calculation is: R _s=25.4%, T _s=72.7%, R _p=0, T _p=98.1%;

Degree of polarization measuring process is as follows:

Step 1. regulates and treats that light-metering is with incidence angle θ ₁be incident on optical element 1, θ ₁scope be 0 ° of < θ ₁< 90 °, selects the concrete numerical value of incident angle according to actual conditions;

What step 2. measured optical element 1 transmittance and reflectance respectively by the first Light-Intensity Detector 3 and the second Light-Intensity Detector 4 treats measured light intensity;

Step 3. data handling system 5 is according to incidence angle θ ₁that measures with the first Light-Intensity Detector 3 and the second Light-Intensity Detector 4 optical element 1 transmittance and reflectance obtained treats that measured light intensity is in conjunction with degree of polarization computing formula, calculates polarization degree to be measured;

Step 4. judges whether to increase the transmitted light and intensity of reflected light measurement of once treating light-metering, is return step 3, no, continues next step;

Step 5. judges whether the measurement of increase by angle of light degree to be measured, is return step 1, no, terminates.

This degree of polarization optical path control method is as follows:

As shown in Figure 1, Laser Output Beam exposes on optical element 1 i.e. calcium fluoride substrate after aperture, calcium fluoride substrate be arranged on can regulate inclination and pitching stand for optical lens on, turntable is adjusted to zero degree, regulate the inclination of mirror holder and pitching that the reflected light of calcium fluoride substrate is overlapped with aperture incident light, namely the reflected light of calcium fluoride substrate passes through aperture, the inclination of calcium fluoride substrate and pitching can be regulated by turntable, or regulate by other means, as having the stand for optical lens of inclination and pitch regulation function; Now the incident angle of calcium fluoride substrate is zero degree, then turntable is regulated to make incident angle be 56.3 °, remove aperture, measured transmitted light and the energy of reflection light of calcium fluoride substrate by the first Light-Intensity Detector 3 and the second Light-Intensity Detector 4 (all adopting energy meter in this embodiment), use E respectively _tand E _rrepresent, transfer to data handling system 5 (adopting computing machine in this embodiment), according to the incident angle in measuring process, reflected light and transmitted light energy, by the degree of polarization of the program file in computing machine by following formulae discovery incident light:

$P=\frac{|I_s-I_p|}{I}=\left|\frac{[E_T(R_s+R_p)-E_R(T_s+T_p)](1-S-A)}{(R_s{T}_p-R_p{T}_s)(E_T+E_R)}\right|---\left(5\right)$

Four kinds of Model Selection are had during calculating:

Model 1) consider the absorption of calcium fluoride and scattering loss, by absorption loss A, scattering loss S and the R calculated _st _sr _pt _psubstitute in formula (5) and calculate incident light polarization degree;

Model 2) only consider the absorption loss of calcium fluoride, then S=0 in computation process; By absorption loss A and the R calculated _st _sr _pt _psubstitute in formula (5) and calculate incident light polarization degree;

Model 3) only consider the scattering loss of calcium fluoride, then A=0 in computation process; By scattering loss S and the R calculated _st _sr _pt _psubstitute in formula (5) and calculate incident light polarization degree;

Model 4) do not consider any optical loss of calcium fluoride, then A=0, S=0 in computation process; By the R calculated _st _sr _pt _psubstitute in formula (5) and calculate incident light polarization degree.

Tester can select according to actual conditions, and such as, the absorption of the optical base-substrate of employing and scattering loss are very little, as being less than 1%, and less demanding to measuring accuracy, as measuring accuracy require to be 1% time, preference pattern 4 can be considered); If require very high to measuring accuracy, and the absorption of optical base-substrate and scattering loss can not be ignored, and need preference pattern 1).

In the present embodiment, pendulous frequency is set to 6, and the measurement result of preference pattern 1 and model 4 exports simultaneously.Degree of polarization measurement result as shown in table 1 below is obtained through 6 measurements:

Table 1

In this example, optical base-substrate 2 selects calcium fluoride substrate, also the optical element melting low absorption that the deep ultraviolet optical material such as quartz substrate, magnesium fluoride substrate makes and low scattering loss can be changed into, if light beam wavelength to be measured changes, then need corresponding adjustment optical base-substrate 2, the principle of adjustment to reflect the optical base-substrate treating light-metering with transmission, and absorption and the scattering loss for the treatment of light-metering are known, and little, optical base-substrate should be thin to reduce absorption loss, and 3mm is thick or thinner; Optical base-substrate size should be greater than treats that light-metering is incident to three times of on-chip spot size; First energy meter and the second energy meter can be replaced with the detector of laser powermeter or other energy measuring beam intensity, as photodiode, photomultiplier etc.; In this example, aperture 6 is mainly used in regulating incident angle of light to angle on target, additive method also can be adopted to make incident angle accurately be positioned to angle on target, such as, fix the stand for optical lens etc. of incident angle.Data handling system 5 can be computing machine, also manually can record E _tand E _rvalue, calculates degree of polarization by Excel, counter, also can calculate polarization angle value by software programmings such as Matlab, Labview, C language.The incident angle of pendulous frequency and light beam to be measured adjusts according to actual user demand.

Adopt beam polarization degree measurement mechanism of the present invention and method can realize the measurement of incident light polarization degree fast and accurately, have measurement mechanism and method simple, cost is low, measuring accuracy advantages of higher.

Claims (11)

1. a beam polarization degree measurement mechanism, it is characterized in that, this measurement mechanism comprises optical element (1), angle controller (2), first Light-Intensity Detector (3), the second Light-Intensity Detector (4) and data handling system (5); Described optical element (1) is arranged on angle controller (2), the incident angle of light beam to be measured is regulated by angle controller (2), measure the beam intensity through optical element (1) transmittance and reflectance respectively by the first Light-Intensity Detector (3) and the second Light-Intensity Detector (4), use E respectively _tand E _rrepresent; Data handling system (5) is carried out process to measurement result and is obtained incident light polarization degree information.

2. a kind of beam polarization degree measurement mechanism according to claim 1, it is characterized in that, described optical element (1) should be selected to reflect the optical base-substrate treating light-metering with transmission, absorption and the scattering loss for the treatment of light-metering are known, optical base-substrate should be thin to reduce absorption loss, can be that 3mm is thick or thinner, optical base-substrate size should be greater than treats that light-metering is incident to three times of the spot size on optical element (1).

3. a kind of beam polarization degree measurement mechanism according to claim 1, it is characterized in that, described angle controller (2) is mainly used in regulating beam incident angle to be measured, except employing turntable, also other can be adopted can to change the device of incident angle of light, be specially the stand for optical lens with angular adjustment or fixed angle stand for optical lens.

4. a kind of beam polarization degree measurement mechanism according to claim 1, it is characterized in that, described the first Light-Intensity Detector (3) and the second Light-Intensity Detector (4) are for measuring the transmitted light after optical element (1) and intensity of reflected light, thus calculate polarization degree to be measured, Light-Intensity Detector can be energy meter also can be laser powermeter or other can the detector of measuring beam intensity, be specially photodiode or photomultiplier.

5. a kind of beam polarization degree measurement mechanism according to claim 1, it is characterized in that, described optical element (1) is front is provided with incident angle auxiliary conditioning unit (6), when the incident illumination through small holes is incident upon on optical element (1), reflected light equally when small holes (6) incident angle of light be zero degree, except employing aperture, also additive method can be adopted to make incident angle accurately be positioned to zero degree, if incident angle is zero degree when not having an interference fringe by the transmitted light after optical element (1), or after light-metering, adding two apertures, incident light is through two apertures, optical element (1) is added between incident light and contiguous aperture, if optical element (1) transmitted light is equally through two apertures, incident angle of light is zero degree.

6., according to the arbitrary described a kind of beam polarization degree measurement mechanism of claim 1-5, it is characterized in that, can take multiple measurements when identical incident angle, to effectively reduce degree of polarization measuring error, namely concrete three measurements can meet the demands.

7. according to the arbitrary described a kind of beam polarization degree measurement mechanism of claim 1-5, it is characterized in that, the angle controller (2) of optical element (1) is being installed by adjustment, different incidence angles is taken multiple measurements, thus the polarization degree to be measured that when calculating different incidence angles, measurement obtains, to effectively reduce degree of polarization measuring error.

8. a beam polarization degree measuring method, is characterized in that, measuring process is as follows:

Step 1, adjustment treat that light-metering is with incidence angle θ ₁be incident on optical element (1), θ ₁scope be 0 ° of < θ ₁< 90 °, selects incident angle determined value according to actual conditions;

Step 2, to measure optical element (1) transmittance and reflectance respectively by the first Light-Intensity Detector (3) and the second Light-Intensity Detector (4) treat measured light intensity;

Step 3, data handling system (5) are according to incidence angle θ ₁that measures with the first Light-Intensity Detector (3) and the second Light-Intensity Detector (4) optical element (1) transmittance and reflectance obtained treats that measured light intensity is in conjunction with degree of polarization computing formula, calculates polarization degree to be measured;

Step 4, judging whether to increase the transmitted light of once treating light-metering and intensity of reflected light is measured, is return step 3, no, continues next step;

Step 5, judging whether the measurement of increase by angle of light degree to be measured, is return step 1, no, terminates.

9. a kind of beam polarization degree measuring method according to claim 8, is characterized in that, described incidence angle θ ₁controlled by angle controller (2) and regulate, refraction angle θ ₂obtained by following formulae discovery:

${\mathrm{\&theta;}}_2={\sin }^{-1}\left(\frac{n}{n_{\mathrm{\&lambda;}}}\sin \left({\mathrm{\&theta;}}_1\right)\right).$

10. a kind of beam polarization degree measuring method according to claim 9, is characterized in that, polarization degree computing method to be measured are as follows:

(1) will treat that the component vibrated perpendicular to the plane of incidence and the component being parallel to plane of incidence vibration are resolved in light-metering, usually the component vibrated perpendicular to the plane of incidence is called s light, and the component being parallel to plane of incidence vibration is called p light, then treat that measured light intensity is expressed as:

I＝I _s+I _p

(2) calculating incident angle is θ ₁time optical element 1 treat the reflection and transmission coefficients of light-metering, described optical wavelength to be measured is λ, and optical element (1) refractive index is at that wavelength n _λ, beam propagation medium refraction index to be measured is n, and the incident angle that light beam is incident to optical element (1) is θ ₁, refraction angle is θ ₂, then according to fresnel's law, treat that the s light of light-metering and p light are expressed as in the transmissivity of optical element (1) plane of incidence and reflectivity:

$r_s=\frac{{\sin }^2({\mathrm{\&theta;}}_1-{\mathrm{\&theta;}}_2)}{{\sin }^2({\mathrm{\&theta;}}_1+{\mathrm{\&theta;}}_2)}$

$r_p=\frac{{\tan }^2({\mathrm{\&theta;}}_1-{\mathrm{\&theta;}}_2)}{{\tan }^2({\mathrm{\&theta;}}_1+{\mathrm{\&theta;}}_2)}$

$t_s=\frac{\sin {2\mathrm{\&theta;}}_1\sin {2\mathrm{\&theta;}}_2}{{\sin }^2({\mathrm{\&theta;}}_1+{\mathrm{\&theta;}}_2)}$

$t_p=\frac{\sin {2\mathrm{\&theta;}}_1\sin {2\mathrm{\&theta;}}_2}{{\sin }^2({\mathrm{\&theta;}}_1+{\mathrm{\&theta;}}_2){\cos }^2({\mathrm{\&theta;}}_1-{\mathrm{\&theta;}}_2)}$

Wherein, t _sfor the transmissivity at optical element (1) plane of incidence of s light; t _pfor p light is in the transmissivity of optical element (1) plane of incidence; r _sfor s light is at the reflectivity of optical element (1) plane of incidence; r _pfor p light is at the reflectivity of optical element (1) plane of incidence;

(3) calculating incident angle is θ ₁time optical element (1) treat total reflectivity and the total transmittance of light-metering, optical element (1) thickness is d, according to the propagation principle of light, is expressed as through the total transmittance of optical element (1) and total reflectivity:

$R_s=r_s+t_s^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_s^{2i-1}$

$R_p=r_p+t_p^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_p^{2i-1}$

$T_s=t_s^2+t_s^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_s^{2i}$

$T_p=t_p^2+t_p^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_p^{2i}$

R _s+T _s＝1

R _p+T _p＝1

Wherein, T _sfor s light is through the total transmittance of optical element (1); T _pfor p light is through the total transmittance of optical element (1); R _sfor s light is through the total reflectivity of optical element (1); R _pfor p light is through the total reflectivity of optical element (1);

(4) incident angle that basis calculates is θ ₁time optical element (1) treat light-metering reflectivity and transmissivity, and measure the energy of reflection light that obtains and transmitted light energy, obtain polarization degree to be measured; Beam intensity through optical element (1) transmittance and reflectance is expressed as:

E _T＝I _s×T _s+I _p×T _p

E _R＝I _s×R _s+I _p×R _p

Wherein, E _tthrough the beam intensity of optical element (1) transmission; E _rthrough the beam intensity that optical element (1) reflects;

Therefore obtain incident light polarization degree P according to degree of polarization definition to be expressed as:

$P=\frac{|I_s-I_p|}{I}=\left|\frac{E_T(R_s+R_p)-E_R(T_s+T_p)}{(R_p-R_s)(E_T+E_R)}\right|.$

11. a kind of beam polarization degree measuring methods according to claim 10, it is characterized in that surface scattering loss S and the optical absorption loss A that can consider optical element (1) in degree of polarization computation process, then the s light after considering optical element loss and p light total transmittance and total reflectivity are expressed as:

$R_s=r_s(1-S)+t_s^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_s^{2i-1}{(1-S)}^{2i+1}{(1-A)}^{2i}$

$R_p=r_p(1-S)+t_p^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_p^{2i-1}{(1-S)}^{2i+1}{(1-A)}^{2i}$

$T_s=t_s^2(1-A){(1-S)}^2+t_s^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_s^{2i}{(1-S)}^{2(i+1)}{(1-A)}^{2i+1}$

$T_p=t_p^2(1-A){(1-S)}^2+t_p^2\underset{i=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{r}_p^{2i}{(1-S)}^{2(i+1)}{(1-A)}^{2i+1}$

R _s+T _s+S+A＝1

R _p+T _p+S+A＝1

Then beam polarization degree P computing formula is as follows:

$P=\frac{|I_s-I_p|}{I}=\left|\frac{[E_T(R_s+R_p)-E_R(T_s+T_p)](1-S-A)}{(R_s{T}_p-R_p{T}_s)(E_T+E_R)}\right|.$