CN104296875B - 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 apparatus and method

Technical field

The present invention relates to the technical field of beam polarization degree measurement and in particular 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.Shaken according to light wave vector The situation of change in dynamic direction, can split the light into natural light and polarized light, and polarized light can be further divided into line polarisation, circle partially again Shake light, elliptically polarized light.For line polarized light, generally the component perpendicular to incident surface vibration is referred to as s component (s light), and handle Component parallel to incident surface vibration is referred to as p-component (p light).Polarization characteristic is one of key property of light beam, the polarization letter of light Breath detects and is used widely in fields such as atural object remote sensing, astronomy, medical science and Military Application.

The measurement of polarization characteristic method of light is also a lot, such as patent cn 102243104 a, a kind of measurement polarized light in real time The device of characteristic, it adopts unpolarized Amici prism, half-wave plate, 2 polarization splitting prisms and No. 4 photo-detectors, by 4 road light The measurement of power is realizing the real-time measurement of incident polarization light characteristic, the azimuth including polarized light and polarization extinction ratio information. Patent cn 102435418 a, arf laser optics thin-film component versatile polarimeter and method, this device is divided by arf is accurate Sub- laser instrument, arf excimer laser beam-expanding collimation device, iriss, the polarizer, beam splitter, sample stage pivotal support arm group Become, the polarized reflectance in different incidence angles for the optical thin film element of different shapes can be measured, absorbance, reflection are moved back simultaneously The degree of bias and transmission Untwisting Effect, and measurement of polarization characteristic method therein is also using analyzer (rochon prism polaroid) and to visit Survey device integrated processes to measure.Patent cn 102933944 a proposes a kind of system for measuring beam polarization and side Method.This optical system includes polarization beam splitting assembly and picture element matrix, and polarization beam splitting assembly is by polarization beam apparatus and birefringence element Composition, for being divided into beam component predetermined number, having predetermined polarisation relation each other by input beam.Picture element matrix For detecting the intensity distributions in light beam incident thereon, intensity distributions in each output beam component for the analysis, determine The Stokes' parameter of the expression polarization profile of input beam, so that it is determined that the polarization characteristic of input beam.

Light beam polarization characteristic measurement method in sum all adopts multiple polarimetry optical elements and complicated measurement Structure, has the shortcomings of measurement cost is high, and measurement is slow.

Content of the invention

The purpose of the present invention is to design a kind of beam polarization degree measurement apparatus and method, realizes light beam by simple mechanism inclined The high-acruracy survey of degree of shaking.

The technical solution used in the present invention is: a kind of beam polarization degree measurement device, and described measurement apparatus include optics unit Part, angle controller, the first Light-Intensity Detector, the second Light-Intensity Detector data processing system；Described optical element peace It is contained on angle controller, adjusts the incident angle of light beam to be measured by angle controller, by the first Light-Intensity Detector and Two Light-Intensity Detectors measure the beam intensity through optical element transmission and reflection respectively, use e respectively_tAnd e_rRepresent；Data processing System carries out process to measurement result and obtains incident light polarization degree information.

Described optical element should be selected to reflect the optical base-substrate treating light-metering with transmission, treat the absorption of light-metering and dissipate Penetrate loss it is known that optical base-substrate should thin can be that 3mm is thick or thinner to reduce absorption loss, optical base-substrate size should greatly In treating that light-metering is incident to three times of the spot size on optical element.

Described angle controller is mainly used in adjusting beam incident angle to be measured, in addition to using turntable, it would however also be possible to employ its He can change the device of incident angle of light, such as the stand for optical lens with angular adjustment or fixed angle stand for optical lens.

The first described Light-Intensity Detector and the second Light-Intensity Detector are used for transmitted light after optical element for the measurement And intensity of reflected light, thus calculating polarization degree to be measured, Light-Intensity Detector can be energy meter can also be laser power meter Or the detector of other energy measuring beam intensity, such as photodiode, photomultiplier tube etc..

It is provided with angle of incidence auxiliary conditioning unit, when the incident illumination through small holes is incident upon optics unit before described optical element On part, it is zero degree that reflected light also passes through during aperture incident angle of light, in addition to using aperture, it would however also be possible to employ additive method make into Firing angle degree is accurately positioned to zero degree, if it is zero degree that the transmitted light after optical element does not have incident angle during interference fringe, Or adding two apertures after light-metering, incident illumination, through two apertures, adds optics unit between incident illumination and neighbouring aperture Part, if optical element transmitted light also passes through two apertures, incident angle of light is zero degree.

Can take multiple measurements during identical angle of incidence, to effectively reduce degree of polarization measurement error, general three measurements are Requirement can be met.

By adjusting the angle controller being provided with optical element, different incidence angles are taken multiple measurements, thus calculating The polarization degree to be measured that during different incidence angles, measurement obtains, to effectively reduce degree of polarization measurement error.

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

Step 1, regulation treat light-metering with incidence angle θ₁It is incident on optical element, θ₁Scope be 0 ° of ＜ θ₁90 ° of ＜, according to Practical situation selects angle of incidence determination value；

Step 2, pass through the first Light-Intensity Detector and the second Light-Intensity Detector respectively and measure optical element transmission and anti- That penetrates treats measured light intensity；

Step 3, data handling system are according to incidence angle θ₁Survey with the first Light-Intensity Detector and the second Light-Intensity Detector With reflection, the optical element transmission measuring treats that measured light intensity combines degree of polarization computing formula, be calculated light polarization to be measured Degree；

Step 4, judge whether to increase the transmitted light once treating light-metering and intensity of reflected light measurement, be, return to step 3, no, Continue next step；

Step 5, judge whether to increase the measurement of an angle of light degree to be measured, be, return to step 1, no, terminate.

Further, described incidence angle θ₁By angle controller control and regulation, refraction angle θ₂Calculated by below equation Obtain:

${\mathrm{\θ}}_2={\sin }^{-1}\left(\frac{n}{n_{\mathrm{\λ}}}\sin \left({\mathrm{\θ}}_1\right)\right).$

Polarization degree computational methods to be measured are as follows:

(1) photolysis to be measured are become perpendicular to the component of incident surface vibration and the component parallel to incident surface vibration, generally Component perpendicular to incident surface vibration is referred to as s light, and the component parallel to incident surface vibration is referred to as p light, then light intensity to be measured Degree is expressed as:

I=i_s+i_p

(2) calculating angle of incidence is θ₁When optical element treat the reflection and transmission coefficients of light-metering, described light wave to be measured A length of λ, optical element refractive index at that wavelength is n_λ, beam propagation medium refraction index to be measured is n, and light beam is incident to optics The incident angle of element is θ₁, refraction angle is θ₂, then according to fresnel's law, treat that the s light of light-metering and p light are incident in optical element The absorbance in face and reflectance are expressed as:

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

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

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

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

Wherein, t_sFor s light the optical element plane of incidence absorbance；t_pFor p light the optical element plane of incidence transmission Rate；r_sFor s light the optical element plane of incidence reflectance；r_pFor p light the optical element plane of incidence reflectance；

(3) calculating angle of incidence is θ₁When optical element treat total reflectance and the absorbance of light-metering, optical element is thick Spend for d, according to the propagation principle of light, be expressed as through the total transmittance of optical element and reflectance:

$r_s=r_s+t_s^2\underset{i=1}{\overset{\∞}{\mathrm{\σ}}}{r}_s^{2i-1}$

$r_p=r_p+t_p^2\underset{i=1}{\overset{\∞}{\mathrm{\σ}}}{r}_p^{2i-1}$

$t_s=t_s^2+t_s^2\underset{i=1}{\overset{\∞}{\mathrm{\σ}}}{r}_s^{2i}$

$t_p=t_p^2+t_p^2\underset{i=1}{\overset{\∞}{\mathrm{\σ}}}{r}_p^{2i}$

r_s+t_s=1

r_p+t_p=1

Wherein, t_sFor s light through optical element total transmittance；t_pFor p light through optical element total transmittance；r_sFor s Light is through the total reflectivity of optical element；r_pFor p light through optical element total reflectivity；

(4) according to calculated angle of incidence be θ₁When optical element treat light-metering reflectance and absorbance, and measurement The energy of reflection light obtaining and transmitted light energy, obtain polarization degree to be measured；Light beam intensity through optical element transmission and reflection Degree 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_tBeam intensity through optical element transmission；e_rBeam intensity through 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 in degree of polarization calculating process that surface scattering loss s of optical element and optical absorption are damaged Consumption a, then consider that the s light after optical element loss and p light total transmittance are expressed as with total reflectivity:

$r_s=r_s(1-s)+t_s^2\underset{i=1}{\overset{\∞}{\mathrm{\σ}}}{r}_s^{2i-1}{(1-s)}^{2i+1}{(1-a)}^{2i}$

$r_p=r_p(1-s)+t_p^2\underset{i=1}{\overset{\∞}{\mathrm{\σ}}}{r}_p^{2i-1}{(1-s)}^{2i+1}{(1-a)}^{2i}$

$t_s=t_s^2(1-a){(1-s)}^2+t_s^2\underset{i=1}{\overset{\∞}{\mathrm{\σ}}}{r}_s^{2i}{(1-s)}^{2i+1}{(1-a)}^{2i+1}$

$t_p=t_p^2(1-a){(1-s)}^2+t_p^2\underset{i=1}{\overset{\∞}{\mathrm{\σ}}}{r}_p^{2i}{(1-s)}^{2(i+1)}{(1-a)}^{2i+1}$

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 has the advantage that

(1) present invention can realize beam polarization degree only with a piece of optical element and two beam intensity detectors Measurement, measurement apparatus are simple；

(2) present invention pass through to change the optical element corresponding from light beam wavelength to be measured and detector can realize different The degree of polarization measurement of the incident beam of wavelength, measurement range is wide；

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

Brief description

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

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

Specific embodiment

A kind of beam polarization degree measurement apparatus and method of the present invention will be described in further detail below.

It is illustrated in figure 1 the measuring light path diagram of degree of polarization measurement apparatus, including light source 0, optical element 1, angle demodulator 2, adopt turntable in this example, the first Light-Intensity Detector 3, the second Light-Intensity Detector 4, data handling system 5 and angle of incidence auxiliary Help adjusting means 6, in the present embodiment, adopt aperture.Aperture is located at the light path rear of light source 0, for adjusting incident angle of light to mesh Mark angle；Optical element 1 is located on turntable, and light beam incides on optical element 1 after small holes, and a part of light beam is through optics unit Part 1 is transmitted on the first Light-Intensity Detector 3, and another part light beam is reflexed to the second Light-Intensity Detector 4 by optical element 1 On.Data handling system 5 receives the data from the first Light-Intensity Detector 3 and the second Light-Intensity Detector 4, through internal After routine processes, read degree of polarization measured value.

In this example, light beam to be measured is 193nm excimer laser output beam it is known that Laser Output Beam is completely non- Polarized light, i.e. beam polarization degree p=0；Laser Output Beam is incident on the optical element 1 being arranged on turntable, optics unit Part 1 is calcirm-fluoride substrate, and the refractive index at 193nm wavelength is 1.5015, absorption loss a=1%, scattering loss s= 0.9%；Turntable adopts precision to be 0.023 °, the newport turntable urs75bcc of 360 ° of carryover；Aperture adopts thorlabs company Adjustable aperture, hole diameter minimum can adjust to 1mm；The first Light-Intensity Detector 3 and the second light intensity by same model Detector 4 measures transmission and the reflected light beam intensities of optical element 1, and Light-Intensity Detector selects the j- of coherent company 25mt-10khz pyroelectricity energy meter, can be represented with the first energy meter and the second energy meter respectively；Data handling system is using meter Calculation machine.For convenience of calculation, adjusting calcirm-fluoride substrate makes angle of incidence be equal to Brewster angle, calcirm-fluoride substrate under Brewster angle Reflected light in no p-polarization light, i.e. r_p=0；Defined according to Brewster angle:

${\tan \mathrm{\θ}}_b=\frac{n_{\mathrm{\λ}}}{n}---\left(1\right)$

Brewster angle under the incident illumination of 193nm for the in the air calcirm-fluoride substrate is 56.3 °, i.e. incidence angle θ₁= 56.3 °, under this angle, the s light of the calcirm-fluoride substrate plane of incidence and p luminous reflectance, transmittance calculation are as follows:

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

$\begin{array}{c}{r}_p=\frac{{\tan }^2({\mathrm{\θ}}_1-{\mathrm{\θ}}_2)}{{\tan }^2({\mathrm{\θ}}_1+{\mathrm{\θ}}_2)}\\ t_s=\frac{\sin {2\mathrm{\θ}}_1\sin {2\mathrm{\θ}}_2}{{\sin }^2({\mathrm{\θ}}_1+{\mathrm{\θ}}_2)}\end{array}---\left(2\right)$

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

Wherein, t_sFor s light optical element 1 plane of incidence absorbance；t_pFor p light optical element 1 plane of incidence transmission Rate；r_sFor s light optical element 1 plane of incidence reflectance；r_pFor p light optical element 1 plane of incidence reflectance；

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

r_s=14.86%, t_s=85.14%, r_p=0, t_p=100%

After two-sided multiple reflections and transmission, do not consider that reflectance during optical element loss and absorbance represent For:

$r_s=r_s+t_s^2\underset{i=1}{\overset{\∞}{\mathrm{\σ}}}{r}_s^{2i-1}$

$\begin{array}{c}{r}_p=r_p+t_p^2\underset{i=1}{\overset{\∞}{\mathrm{\σ}}}{r}_p^{2i-1}\\ t_s=t_s^2+t_s^2\underset{i=1}{\overset{\∞}{\mathrm{\σ}}}{r}_s^{2i}\end{array}---\left(3\right)$

$t_p=t_p^2+t_p^2\underset{i=1}{\overset{\∞}{\mathrm{\σ}}}{r}_p^{2i}$

Wherein, t_sFor s light through optical element 1 total transmittance；t_pFor p light through optical element 1 total transmittance；r_s For s light through optical element 1 total reflectivity；r_pFor p light through optical element 1 total reflectivity；

Result of calculation is: r_s=25.88%, t_s=74.12%, r_p=0, t_p=100%；

When the absorption considering calcirm-fluoride substrate and scattering loss back reflection rate and absorbance are expressed as:

$r_s=r_s(1-s)+t_s^2\underset{i=1}{\overset{\∞}{\mathrm{\σ}}}{r}_s^{2i-1}{(1-s)}^{2i+1}{(1-a)}^{2i}$

$\begin{array}{c}{r}_p=r_p(1-s)+t_p^2\underset{i=1}{\overset{\∞}{\mathrm{\σ}}}{r}_p^{2i-1}{(1-s)}^{2i+1}{(1-a)}^{2i}\\ t_s=t_s^2(1-a){(1-s)}^2+t_s^2\underset{i=1}{\overset{\∞}{\mathrm{\σ}}}{r}_s^{2i}{(1-s)}^{2(i+1)}{(1-a)}^{2i+1}\end{array}---\left(4\right)$

$t_p=t_p^2(1-a){(1-s)}^2+t_p^2\underset{i=1}{\overset{\∞}{\mathrm{\σ}}}{r}_p^{2i}{(1-s)}^{2(i+1)}{(1-a)}^{2i+1}$

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. is adjusted treats light-metering with incidence angle θ₁It is incident on optical element 1, θ₁Scope be 0 ° of ＜ θ₁90 ° of ＜, according to Practical situation selects angle of incidence concrete numerical value；

Step 2. pass through respectively the first Light-Intensity Detector 3 and the second Light-Intensity Detector 4 measure optical element 1 transmission and Reflect treats measured light intensity；

Step 3. data handling system 5 is according to incidence angle θ₁With the first Light-Intensity Detector 3 and the second Light-Intensity Detector 4 With reflection, optical element 1 transmission that measurement obtains treats that measured light intensity combines degree of polarization computing formula, be calculated and treat that light-metering is inclined Degree of shaking；

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

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

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

As shown in figure 1, it is calcium fluoride in calcirm-fluoride substrate that Laser Output Beam exposes to optical element 1 after aperture Substrate is arranged in the stand for optical lens that can adjust with pitching, turntable is adjusted and adjusts the inclination of mirror holder to zero degree and bow Face upward and so that the reflected light of calcirm-fluoride substrate is overlapped with aperture incident illumination, that is, the reflected light of calcirm-fluoride substrate passes through aperture, be fluorinated calcio The inclination of piece and pitching can be adjusted by turntable, or adjust by other means, such as have inclination and pitch regulation function Stand for optical lens；Now the angle of incidence of calcirm-fluoride substrate is zero degree, and then adjusting turntable and making angle of incidence is 56.3 °, removes aperture, By the first Light-Intensity Detector 3 and the second Light-Intensity Detector 4 (all using energy meter in this embodiment) measurement fluorination calcio The transmitted light of piece and energy of reflection light, use e respectively_tAnd e_rRepresent, transmit to data handling system 5 (using calculating in this embodiment Machine), according to the angle of incidence in measurement process, reflected light and transmitted light energy, passed through public as follows by the program file in computer The degree of polarization of formula calculating incident illumination:

$p=\frac{|i_s-i_p|}{i}=\left|\frac{[e_t(r_s+r_p)-e_r(t_s+t_p)](1-s-a)}{(r_s{t}_p-r_p{t}_s)(e_t+e_r)}\right|---\left(5\right)$

Four kinds of models are had to select during calculating:

Model 1) consider the absorption of calcium fluoride and scattering loss, by absorption loss a, scattering loss s and calculated r_s t_sr_pt_pSubstitute in formula (5) and be calculated incident light polarization degree；

Model 2) only consider the absorption loss of calcium fluoride, then s=0 in calculating process；By absorption loss a and calculated r_st_sr_pt_pSubstitute in formula (5) and be calculated incident light polarization degree；

Model 3) only consider the scattering loss of calcium fluoride, then a=0 in calculating process；By scattering loss s and calculated r_st_sr_pt_pSubstitute in formula (5) and be calculated incident light polarization degree；

Model 4) do not consider any optical loss of calcium fluoride, then a=0 in calculating process, s=0；By calculated r_s t_sr_pt_pSubstitute in formula (5) and be calculated incident light polarization degree.

Tester can be selected according to practical situation, for example, the absorption of the optical base-substrate of employing and scattering loss Very little, such as less than 1%, and less demanding to certainty of measurement, such as certainty of measurement require for when 1% it may be considered that preference pattern 4)；If require very high to certainty of measurement, 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, simultaneously the measurement result output of preference pattern 1 and model 4.Through 6 times Measure and obtain degree of polarization measurement result as shown in table 1 below:

Table 1

In this example optical base-substrate 2 from calcirm-fluoride substrate it is also possible to change the deep ultraviolets such as fused silica substrate, Afluon (Asta) substrate into Low absorption and the optical element of low scattering loss that optical material is made, if light beam wavelength to be measured changes, need accordingly to adjust Whole optical base-substrate 2, the principle of adjustment is to reflect the optical base-substrate treating light-metering with transmission, treats the absorption of light-metering and scattering is damaged Consumption it is known that and little, optical base-substrate should thin to reduce absorption loss, 3mm is thick or thinner；Optical base-substrate size should be greater than treating Light-metering is incident to three times of the spot size on substrate；First energy meter and the second energy meter can be replaced with laser power meter or The detector of other energy measuring beam intensity of person, such as photodiode, photomultiplier tube etc.；In this example, aperture 6 is mainly used in adjusting Section incident angle of light is to angle on target, it would however also be possible to employ additive method makes incident angle be accurately positioned to angle on target, for example solid Determine stand for optical lens of incident angle etc..Data handling system 5 can be computer it is also possible to manually recorded e_tAnd e_rValue, passes through Excel, computer are calculated degree of polarization it is also possible to be calculated partially by software programmings such as matlab, labview, c language Shake angle value.The angle of incidence of pendulous frequency and light beam to be measured is adjusted according to actually used demand.

Fast and accurately incident light polarization can be realized using beam polarization degree measurement apparatus and method of the present invention The measurement of degree, it is simple to have measurement apparatus and a method, low cost, the advantages of certainty of measurement is high.

Claims (8)

1. a kind of beam polarization degree measurement device is it is characterised in that this measurement apparatus includes optical element (1), angle controller (2), the first Light-Intensity Detector (3), the second Light-Intensity Detector (4) data processing system (5)；Described optical element (1) It is arranged on angle controller (2), adjusts the incident angle of light beam to be measured by angle controller (2), visited by the first light intensity Survey the beam intensity that device (3) and the second Light-Intensity Detector (4) measure respectively through optical element (1) transmission and reflect, use respectively e_tAnd e_rRepresent；Data handling system (5) carries out process to measurement result and obtains incident light polarization degree information；

Described optical element (1) is selected to reflect the optical base-substrate treating light-metering with transmission, treats absorption and the scattering of light-metering It is known that optical base-substrate is 3mm thickness, optical base-substrate size is more than treats the spot size that light-metering is incident on optical element (1) for loss Three times.

2. a kind of beam polarization degree measurement device according to claim 1 is it is characterised in that described angle controller (2) be used for adjusting beam incident angle to be measured, in addition to using turntable, it would however also be possible to employ stand for optical lens with angular adjustment or Fixed angle stand for optical lens.

3. a kind of beam polarization degree measurement device according to claim 1 is it is characterised in that the first described light intensity is visited Survey device (3) and the second Light-Intensity Detector (4) is used for transmitted light after optical element (1) for the measurement and intensity of reflected light, thus Calculate polarization degree to be measured, Light-Intensity Detector can be energy meter can also be laser power meter or photodiode or light Electric multiplier tube.

4. a kind of beam polarization degree measurement device according to claim 1 is it is characterised in that before described optical element (1) It is provided with angle of incidence auxiliary conditioning unit (6), angle of incidence auxiliary conditioning unit (6) is aperture, when the incident illumination through small holes It is incident upon on optical element (1), it is zero degree that reflected light also passes through incident angle of light during aperture；Or

In addition to using aperture, so that incident angle is accurately positioned to zero degree, bar is not interfered by the transmitted light after optical element (1) During stricture of vagina, incident angle is zero degree；Or

Adding two apertures after light-metering, incident illumination, through two apertures, adds optics unit between incident illumination and neighbouring aperture Part (1), if optical element (1) transmitted light also passes through two apertures, incident angle of light is zero degree.

5. according to a kind of arbitrary described beam polarization degree measurement device of claim 1-4 it is characterised in that in identical angle of incidence When take multiple measurements, to effectively reduce degree of polarization measurement error.

6. according to a kind of arbitrary described beam polarization degree measurement device of claim 1-4 it is characterised in that being pacified by regulation Different incidence angles are taken multiple measurements by the angle controller (2) equipped with optical element (1), thus when calculating different incidence angles Measure the polarization degree to be measured obtaining, to effectively reduce degree of polarization measurement error.

7. a kind of beam polarization degree measurement method is it is characterised in that measuring process is as follows:

Step 1, regulation treat light-metering with incidence angle θ₁It is incident on optical element (1), θ₁Scope be 0 ° of < θ₁< 90 °, according to reality Situation selects angle of incidence determination value；

Step 2, respectively pass through the first Light-Intensity Detector (3) and the second Light-Intensity Detector (4) measurement optical element (1) transmission With reflection treat measured light intensity；

Step 3, data handling system (5) are according to incidence angle θ₁With the first Light-Intensity Detector (3) and the second Light-Intensity Detector (4) optical element (1) transmission that obtains of measurement and reflection treat that measured light intensity combines degree of polarization computing formula, be calculated to be measured Polarization degree；

Step 4, judge whether to increase the transmitted light once treating light-metering and intensity of reflected light measurement, be, return to step 3, no, continue Next step；

Step 5, judge whether to increase the measurement of an angle of light degree to be measured, be, return to step 1, no, terminate；

Wherein, described incidence angle θ₁Controlled by angle controller (2) and adjust, refraction angle θ₂It is calculated by below equation:

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

Polarization degree computational methods to be measured are as follows:

(1) photolysis to be measured are become perpendicular to the component of incident surface vibration and the component parallel to incident surface vibration, generally vertical The straight component in incident surface vibration is referred to as s light, and the component parallel to incident surface vibration is referred to as p light, then treat measured light intensity table It is shown as:

I=i_s+i_p

(2) calculating angle of incidence is θ₁When optical element (1) treat the reflection and transmission coefficients of light-metering, described optical wavelength to be measured For λ, optical element (1) refractive index at that wavelength is n_λ, beam propagation medium refraction index to be measured is n, and light beam is incident to light The incident angle learning element (1) is θ₁, refraction angle is θ₂, then according to fresnel's law, treat the s light of light-metering and p light in optical element (1) absorbance of the plane of incidence and reflectance are expressed as:

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

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

$t_s=\frac{sin2{\mathrm{\&theta;}}_{1}sin2{\mathrm{\&theta;}}_2}{{\sin }^2({\mathrm{\&theta;}}_1+{\mathrm{\&theta;}}_2)}$

$t_p=\frac{sin2{\mathrm{\&theta;}}_{1}sin2{\mathrm{\&theta;}}_2}{{\sin }^2({\mathrm{\&theta;}}_1+{\mathrm{\&theta;}}_2){\cos }^2({\mathrm{\&theta;}}_1-{\mathrm{\&theta;}}_2)}$

Wherein, t_sFor s light optical element (1) plane of incidence absorbance；t_pFor p light optical element (1) plane of incidence transmission Rate；r_sFor s light optical element (1) plane of incidence reflectance；r_pFor p light optical element (1) plane of incidence reflectance；

(3) calculating angle of incidence is θ₁When optical element (1) treat total reflectance 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:

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

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

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

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

r_s+t_s=1

r_p+t_p=1

Wherein, t_sFor the total transmittance through optical element (1) for the s light；t_pFor the total transmittance through optical element (1) for the p light；r_s For the total reflectivity through optical element (1) for the s light；r_pFor the total reflectivity through optical element (1) for the p light；

(4) according to calculated angle of incidence be θ₁When optical element (1) treat light-metering reflectance and absorbance, and measure The energy of reflection light arriving and transmitted light energy, obtain polarization degree to be measured；Light beam intensity through optical element (1) transmission and reflection Degree 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_tBeam intensity through optical element (1) transmission；e_rThe beam intensity reflecting through optical element (1)；

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

$p=\frac{|i_s-i_p|}{i}=\left|\frac{e_t(r_s+r_p)-e_r(t_s+t_p)}{(r_p-r_s)(e_t+e_r)}\right|.$

8. a kind of beam polarization degree measurement method according to claim 7 is it is characterised in that can in degree of polarization calculating process To consider surface scattering loss s and optical absorption loss a of optical element (1), then consider the s light after optical element loss and p Light total transmittance and total reflectivity are expressed as:

$r_s=r_s(1-s)+t_s^2\underset{i=1}{\overset{\mathrm{\&infin;}}{\&sigma;}}{r}_s^{2i-1}{(1-s)}^{2i+1}{(1-a)}^{2i}$

$r_p=r_p(1-s)+t_p^2\underset{i=1}{\overset{\mathrm{\&infin;}}{\&sigma;}}{r}_p^{2i-1}{(1-s)}^{2i+1}{(1-a)}^{2i}$

$t_s=t_s^2(1-a){(1-s)}^2+t_s^2\underset{i=1}{\overset{\mathrm{\&infin;}}{\&sigma;}}{r}_s^{2i}{(1-s)}^{2(i+1)}{(1-a)}^{2i+1}$

$t_p=t_p^2(1-a){(1-s)}^2+t_p^2\underset{i=1}{\overset{\mathrm{\&infin;}}{\&sigma;}}{r}_p^{2i}{(1-s)}^{2(i+1)}{(1-a)}^{2i+1}$

r_s+t_s+ s+a=1

r_p+t_p+ s+a=1

Then beam polarization degree p computing formula is as follows:

$p=\frac{|i_s-i_p|}{i}=\left|\frac{\&lsqb;e_t(r_s+r_p)-e_r(t_s+t_p)\&rsqb;(1-s-a)}{(r_s{t}_p-r_p{t}_s)(e_t+e_r)}\right|.$