CN100495118C - Electrically-controlled super-resolution pupil filter - Google Patents

Abstract

The invention is an electric controlled super-resolution pupil filter, comprising polarizer, electro-optic crystal, radially symmetrical birefringent and analyzer, where the electro-optic crystal and the radially symmetrical birefringent crystal are arranged between the polarizer and the analyzer; optical axes of the polarizer and the analyzer are in parallel; azimuth angle of the electro-optic crystal is determined by principal axis of electric induction, included angle theta between slow axis of electric induction and the polarizer = 45 deg. or 135 deg.; directions of slow axes of the radially symmetrical birefringent crystal and the electro-optic crystal are consistent. By electro-optic modulation on the electro-optic crystal, it can realize real-time control of horizontal super-resolution performance parameters and expansion of axial focal depth.

Description

Electrically-controlled super-resolution pupil filter

Technical field

The present invention is a kind of electrically-controlled super-resolution pupil filter.This invention is mainly used in technical fields such as uranology, Flame Image Process, cofocus scanning imaging, optical storage, laser printing, and the extended focal depth of Huo Deing makes it can be applicable to fields such as microscope imaging, optical correction and tomography simultaneously.

Background technology

Two kinds of effects of optical ultra-discrimination and axial expansion depth of focus have all been carried out research extensively and profoundly independently of one another.Super resolution technology provides a kind of method for surmounting classical diffraction limit, and the iris filter of wherein using super-resolution is the main method that realizes optical ultra-discrimination at present, and the method for traditional design super-resolution pupil filter is the phase-plate design.In recent years, realize that by polarization effect the method for super-resolution is subjected to extensive concern.On the other hand, because extended focal depth launches in succession in the research of applications such as microscope imaging, optical correction and tomography, the research that obtains extended focal depth by polarization effect also just receives publicity.

Formerly technology [1] is (referring to Andrew I.Whiting, " Polarization-AssistedTransverse and Axial Optical Superresolution ", Opt.Express, 11 (5): 1714-1723,2003) be a kind of technology of utilizing polarization effect to realize optical ultra-discrimination.This technology has been utilized the stack of the coaxial crossed polarized light of two bundles, when two-beam has different space distributions, polarization state after the stack can change (gouy phase shift) with the variation of locus, thereby cause redistribution with the spatial position change light intensity, cause near the focal spot focus radially with axial restriction, thereby obtained laterally and axial super resolution.The shortcoming of this technology is that the super-resolution performance parameter is non-adjustable, and is subjected to the influence of light source fluctuation very big.

Formerly technology [2] is (referring to S.Sanyal, " Imaging characteristics of birefringencelenses under focused and defocused condition ", Optik, 110 (11): 513-510,1999) with technology [3] formerly (referring to Maojin Yun, Liren Liu, Jianfeng Sun, " Transverse or axial superresolution with radial birefringent filter ", J.Opt.Soc.Am.A, 21 (10): 1869-1874,2004) all utilized birefringece crystal to realize optical ultra-discrimination.Wherein, mention in the technology [2], can be used for realizing transverse super-resolution birefringent lens selection of parameter different value (comprising birefraction and lens center thickness); What utilize in the technology [3] is specific radial symmetry birefringence element (single face lens, the difference of center and edge crystal thickness satisfies the difference phase difference of half wavelength of orthogonal polarization components retardation), be placed between two polariscopes that transmission optical axis parallels, rotate radially the position angle of birefringence element (by its optical axis direction decision), under the different angles, can obtain transverse super-resolution or axial super resolution respectively.

Formerly technology [4] is (referring to S.Sanyal and A.Ghosh, " High focal depth with aquasi-bifocus birefringent lens ", App.Opt., 39 (14): 2321-2325,2000) proposed to obtain big depth of focus down at specific birefringence lens parameter (lens center thickness α=0.3142 λ or 0.6044 λ).But so accurate lens parameter is difficult to control in practice; Formerly technology [5] is (referring to Xinping Liu, Xianyang Cai, Shoude Chang, " Chander P.GroverCemented doublet lens with an extended focal depth ", Opt.Express., 13 (2): 552-557,2005) compound lens that a kind of birefringent lens is glued to conventional lenses has been proposed, by selecting the suitable birefringent lens and the structural parameters of conventional lenses, also obtained extended focal depth.

Technology [2] [3] [4] is very strict to the requirement of birefringent lens parameter, has seriously limited this The Application of Technology.Compare with above technology, the severity to the birefringent lens parameter request in [5] decreases, but owing to be a kind of very complicated compound lens structure, needs very special matching condition and strict manufacture craft when making in the reality.The super-resolution parameter of above iris filter all can not real-time regulated, thereby its application is restricted.

Summary of the invention

The technical problem to be solved in the present invention is the defective of above-mentioned prior art, and a kind of electrically-controlled super-resolution pupil filter is provided.This iris filter not only can be realized the transverse super-resolution parameter control easily, and can realize transverse super-resolution and axial expansion depth of focus simultaneously under the specific electric field.Near the accurately light distribution control focus.

Basic thought of the present invention is:

By the modulation of electro-optic crystal control two polarized components vertically on phasic difference, control this phasic difference distribution in the horizontal by birefringence element radially, the stack of the light of different polarization states in the space can make that spatial light intensity distributes according to certain rules.

Technical solution of the present invention is as follows:

A kind of electrically-controlled super-resolution pupil filter, it is characterized in that it is made up of the polarizer, electro-optic crystal, radial symmetry birefringece crystal and analyzer, described electro-optic crystal and radial symmetry birefringece crystal place between the polarizer and the analyzer, and the described polarizer is parallel with the light transmission shaft of analyzer; The position angle of described electro-optic crystal is determined according to the orientation of electro-induction main shaft, the angle of the light transmission shaft of the electro-induction slow axis and the polarizer is θ=45 ° or 135 °, the slow-axis direction of radial symmetry birefringece crystal is consistent with the slow-axis direction of electro-optic crystal, the added electric field size is determined according to the half-wave voltage of electro-optic crystal outside the electro-optic crystal, and the change in voltage scope is zero between 2 times the half-wave voltage.

The formation of described electrically-controlled super-resolution pupil filter is: along the optical propagation direction polarizer, electro-optic crystal, radial symmetry birefringece crystal and analyzer successively, also can change into along the optical propagation direction polarizer, radial symmetry birefringece crystal, electro-optic crystal and analyzer successively.

The described polarizer and analyzer are the Glan-Taylor prism of icelandspar making or polariscope, the polaroid of other types.

Described electro-optic crystal is selected LiNbO for use ₃Or other have the electro-optic crystal of Pockels effect, the electro-optic crystal utilization be LiNbO ₃Electrooptical coefficient γ ₂₂Cross electro-optical effect, if adopt other crystal then to determine to utilize cross electro-optical effect or longitudinal electro-optic effect according to its crystal class.

Described radial symmetry birefringece crystal is the uniaxial crystal of quartz crystal or other types.

The present invention compares with technology formerly, has following outstanding characteristics and advantage:

(1) realized the real-time control of transverse super-resolution performance parameter (G and S), the continuous variation of transmissivity realizes by extra electric field;

(2) under the prerequisite that does not change former radial symmetry birefringece crystal structural parameters, the extended focal depth on having obtained axially, and can obtain transverse super-resolution simultaneously;

(3) because the center bit phase delay of radial symmetry birefringece crystal can be adjusted by the electric light bit phase delay of electro-optic crystal, therefore, more help practical application to its manufacturing process being required very strictness.

Description of drawings

Fig. 1 is the structural representation of electrically-controlled super-resolution pupil filter specific embodiment among the present invention

Fig. 2 is the structural parameters of electro-optic crystal and radial symmetry birefringece crystal among the present invention

Fig. 2-the 1st, the structural parameters of electro-optic crystal 2

Fig. 2-the 2nd, the structural parameters of radial symmetry birefringece crystal 3

Fig. 3 be among the present invention transverse super-resolution factor G and S with the change curve of electric light bit phase delay

Fig. 4 is the automatically controlled realization of transverse super-resolution in electric light bit phase delay area I and the Π among the present invention

Fig. 4-the 1st, г=π in the area I/3, π/4, π/6, π/12,0 o'clock horizontal light distribution

Horizontal light distribution when Fig. 4-the 2nd, г in the regional Π=7 π/4,11 π/6,46 pi/2s, 4,2 π

Fig. 5 is the realization of axial expansion depth of focus and transverse super-resolution in the electric light bit phase delay area I II among the present invention

Depth of focus is with the variation of electric light bit phase delay in Fig. 5-the 1st, area I II

Fig. 5-the 2nd, the light distribution on some out of focus face of г=58 π/32

Embodiment

The invention will be further described below in conjunction with embodiment and accompanying drawing.

See also Fig. 1 earlier, Fig. 1 is the structural representation of a specific embodiment of electrically-controlled super-resolution pupil filter among the present invention, as seen from the figure, electrically-controlled super-resolution pupil filter embodiment of the present invention is by forming along the optical propagation direction polarizer 1, electro-optic crystal 2, radial symmetry birefringece crystal 3 and analyzer 4 successively, described electro-optic crystal 2 and radial symmetry birefringece crystal 3 place between the polarizer 1 and the analyzer 4, and the described polarizer 1 is parallel with the light transmission shaft of analyzer 4; The position angle of described electro-optic crystal 2 is determined according to the orientation of electro-induction main shaft, the angle of the light transmission shaft of the electro-induction slow axis and the polarizer 1 is θ=45 ° or 135 °, the slow-axis direction of radial symmetry birefringece crystal 3 is consistent with the slow-axis direction of electro-optic crystal 2, the added electric field size is determined according to the half-wave voltage of electro-optic crystal outside the electro-optic crystal 2, and the change in voltage scope is zero between 2 times the half-wave voltage.

The described polarizer 1 and analyzer 4 are the Glan-Taylor prism of icelandspar making or polariscope, the polaroid of other types.

Described electro-optic crystal 2 is selected LiNbO for use ₃Or other have the electro-optic crystal of Pockels effect, and that electro-optic crystal 2 utilizes is LiNbO ₃Electrooptical coefficient γ ₂₂Cross electro-optical effect, if adopt other crystal then to determine to utilize cross electro-optical effect or longitudinal electro-optic effect according to its crystal class.

Described radial symmetry birefringece crystal 3 is the uniaxial crystal of quartz crystal or other types.

Make following regulation for sake of convenience in Fig. 1: coordinate is xyz; The light transmission shaft direction of the polarizer 1 is along the y direction of principal axis; Electro-optic crystal 2 is according to primary light direction of principal axis and the parallel placement of optical propagation direction z; Radial symmetry birefringece crystal 3 is a uniaxial crystal, and its optical axis is in the plane perpendicular to optical propagation direction z; The light transmission shaft direction of analyzer 4 is along the y direction of principal axis, and is consistent with the light transmission shaft direction of the polarizer 1.

The effect of the polarizer 1 is to make the input light wave be strict linearly polarized light; It is linearly polarized light that the one side of the effect of analyzer 4 makes emergent light, and the light wave component is interfered on the light transmission shaft direction.Electro-optic crystal 2 adopts the uniaxial crystal with linear electrooptical effect, and its effect is by extra electric field the light that passes through to be modulated, and changes the phasic difference of two polarized components; Radially birefringece crystal 3 is uniaxial crystals, and optical axis adopts center half-wave retardation structure, shown in Fig. 2-2: d in lateral cross section ₀Be center thickness, the effect (being actually the bulk delay effect of a plurality of integral multiple wavelength and a half-wavelength) of half-wave retardation is played in the center to incident light; Edge ρ ₀Place's thickness is d _{ρ 0}, with the difference of the retardation at center be half wavelength, promptly retardation is the wavelength of integral multiple, gets this multiple m=50 among the present invention.

The optical principle of this technical scheme institute foundation is as follows:

Electric birefringence to electro-optic crystal 2 is analyzed as follows (with LiNbO ₃Crystal is an example):

Optical axis is along the z direction of principal axis, and electric field is added in the xy plane and along x direction (one of crystal crystallographic axis), behind the added electric field, light wave by the phasic difference of electro-optic crystal 2 is

$\mathrm{\Γ}=2\mathrm{\π}\frac{{n_o}^3{\mathrm{\γ}}_{22}\mathrm{lV}}{\mathrm{\λd}}=\mathrm{kV}---\left(1\right)$

n _oOrdinary light refractive index in the crystal; γ ₂₂The crystal electrooptical coefficient; L/d crystal z is to length and the ratio of x to thickness.Its Jones matrix is $B=\left[\begin{array}{cc}\cos \frac{\mathrm{\&Gamma;}}{2}+i\sin \frac{\mathrm{\&Gamma;}}{2}\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="C200610024485E00111.png,C200610024485E00131.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&theta;}& i\sin \frac{\mathrm{\&Gamma;}}{2}\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="C200610024485E00111.png,C200610024485E00131.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&theta;}\\ i\sin \frac{\mathrm{\&Gamma;}}{2}\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="C200610024485E00111.png,C200610024485E00131.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&theta;}& \cos \frac{\mathrm{\&Gamma;}}{2}-i\sin \frac{\mathrm{\&Gamma;}}{2}\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="C200610024485E00111.png,C200610024485E00131.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&theta;}\end{array}\right].$ Incide radial symmetry birefringece crystal 3 from the light of electro-optic crystal 2 outgoing.With the radially increase of birefringece crystal 3 from the center to the edge thickness, the also corresponding increase of polarization of incident light component bit phase delay amount.From the center to the edge, the bit phase delay difference of two polarized components be changed to half of lambda1-wavelength, i.e. λ/2.Its Jones matrix is

$L=\left[\begin{array}{cc}\cos \left(\frac{\mathrm{\&delta;}\left(\mathrm{\&rho;}\right)}{2}\right)+i\sin \left(\frac{\mathrm{\&delta;}\left(\mathrm{\&rho;}\right)}{2}\right)\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="C200610024485E00111.png,C200610024485E00131.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&theta;}& i\sin \left(\frac{\mathrm{\&delta;}\left(\mathrm{\&rho;}\right)}{2}\right)\sin 2\mathrm{\&theta;}\\ i\sin \left(\frac{\mathrm{\&delta;}\left(\mathrm{\&rho;}\right)}{2}\right)\sin 2\mathrm{\&theta;}& \cos \left(\frac{\mathrm{\&delta;}\left(\mathrm{\&rho;}\right)}{2}\right)-i\sin \left(\frac{\mathrm{\&delta;}\left(\mathrm{\&rho;}\right)}{2}\right)\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="C200610024485E00111.png,C200610024485E00131.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&theta;}\end{array}\right].$

Herein $\mathrm{\&delta;}\left(\mathrm{\&rho;}\right)=\frac{2\mathrm{\&pi;\&Delta;n}}{\mathrm{\&lambda;}}({\mathrm{<figure-callout\; id="0"\; label="d"\; filenames="C200610024485E00131.png"\; state="\{\{state\}\}">d</figure-callout>}}_0+\frac{{\mathrm{\&rho;}}^2}{2R})$ Be the phasic difference of two polarized components in radius ρ place on the lateral cross section, d ₀Be center thickness, R is a radius-of-curvature.

If the light vector of incident directional light

Can obtain pupil function by Jones's theory

$P(\mathrm{\&rho;},\mathrm{\&Gamma;},\mathrm{\&theta;})=\cos \frac{\mathrm{\&delta;}\left(\mathrm{\&rho;}\right)+\mathrm{\&Gamma;}}{2}+i\sin \frac{\mathrm{\&delta;}\left(\mathrm{\&rho;}\right)+\mathrm{\&Gamma;}}{2}\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="C200610024485E00111.png,C200610024485E00131.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&theta;}---\left(2\right)$

If on the viewing plane radially be with axial coordinate $v=\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}\sin \mathrm{\&alpha;}\sqrt{{\mathrm{<figure-callout\; id="2"\; label="x"\; filenames="C200610024485E00111.png,C200610024485E00131.png"\; state="\{\{state\}\}">x</figure-callout>}}^2+{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="C200610024485E00111.png,C200610024485E00131.png"\; state="\{\{state\}\}">y</figure-callout>}}^2},$ $u=\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}\mathrm{<figure-callout\; id="2"\; label="z\; sin"\; filenames="C200610024485E00111.png,C200610024485E00131.png"\; state="\{\{state\}\}">z</figure-callout>}{\sin }^{}{}^2\mathrm{\&alpha;},$ Wherein sin α is the system value aperture, and in θ=45 when ° (or 135 °), laterally v goes up light distribution with axial u and is respectively

$I_v(v,\mathrm{\&Gamma;})={\left|\underset{0}{\overset{{\mathrm{\&rho;}}_0}{\&Integral;}}\left[\cos (\frac{\mathrm{\&delta;}\left(\mathrm{\&rho;}\right)}{2}+\frac{\mathrm{\&Gamma;}}{2})\right]J_0\left(\mathrm{v\&rho;}\right)\mathrm{\&rho;d\&rho;}\right|}^2---\left(3\right)$

$I_u(u,\mathrm{\&Gamma;}={\left|\underset{0}{\overset{{\mathrm{\&rho;}}_0}{\&Integral;}}\left[\cos (\frac{\mathrm{\&delta;}\left(\mathrm{\&rho;}\right)}{2}+\frac{\mathrm{\&Gamma;}}{2})\right]\exp (-\frac{{\mathrm{iu\&rho;}}^2}{2})\mathrm{\&rho;}\mathrm{d\&rho;}\right|}^2$

Light distribution on the out of focus face of focus Δ u distance is

$I_{\mathrm{\&Delta;u}}(v,\mathrm{\&Gamma;})={\left|\underset{0}{\overset{{\mathrm{\&rho;}}_0}{\&Integral;}}\left[\cos (\frac{\mathrm{\&delta;}\left(\mathrm{\&rho;}\right)}{2}+\frac{\mathrm{\&Gamma;}}{2})\right]J_0\left(\mathrm{v\&rho;}\right)\exp (-\frac{{\mathrm{i\&Delta;u\&rho;}}^2}{2})\mathrm{\&rho;}\mathrm{d\&rho;}\right|}^2---\left(4\right)$

(3) and (4) formula show I _v, I _uAnd I _{Δ U}Be the function that electricity causes bit phase delay г, in fact the introducing of electro-optic crystal plays the effect that changes the radial members structural parameters, has provided the method for the redistribution that how to realize near the light intensity of focus.

Technique effect of the present invention is as follows:

Definition super-resolution performance parameter G is the light intensity first zero position ratio of system during with unfiltered Airy disk diffraction mode after the iris filter filtering, and Si Teer is than the ratio of S main lobe intensity of system when accordingly iris filter being arranged and during the Airy disk diffraction.Fig. 3 be the transverse super-resolution factor G of iris filter and S with the variation of electric light phase delay Γ, wherein marked corresponding different horizontal light intensity distribution character zone, different Γ zone.Area I among the figure (0≤г≤pi/2) and the corresponding zone that can realize transverse super-resolution of area I I (7 π/4≤г≤2 π).Area I II (7 π/4≤г≤60 π/32) is included in the area I I, the corresponding zone that can realize axial depth of focus expansion simultaneously.

The real-time control of transverse super-resolution performance parameter.Fig. 4 has provided the horizontal light distribution in I and II two zones respectively, and O is not for adding the light distribution of iris filter.Among Fig. 4-1, in the I zone power taking light bit phase delay г=0, π/12, and π/6, π/4, π/3, G is 0.81～0.92 variation, and S is 0.4～0.75 variation; Among Fig. 4-2, get г=7 π/4,11 π/6,46 pi/2s, 4,2 π in the II zone, G is 0.66～0.81 variation, and S is 0.12～0.40 variation.All realized horizontal super-resolution in two electric light bit phase delay zones.In above zone, can adjust horizontal light intensity distribution character, G and S are realized control in real time by extra electric field.

The realization of axial expansion depth of focus.Definition during light intensity peak variable quantity to be no more than 10% axial distance be the size of depth of focus.Axial and horizontal light intensity normalization distribution character in Γ=58 π/32 near zones in the area I II in Fig. 5-1 and Fig. 5-2 difference corresponding diagram 3.Among Fig. 5-1, in area I II, get г=57 π/32,58 π/32,59 π/32 o'clock obtain axial light distribution, and O is unfiltered axial light distribution, can find out filtering after the depth of focus after the expansion is 2.60 times of depth of focus before the filtering approximately, and o'clock have best extended focal depth in Γ=58 π/32; Fig. 5-the 2nd, the horizontal light distribution in the extended focal depth scope on the out of focus face, wherein out of focus is apart from getting Δ u=0 respectively, and 0.5,1.2, in Γ=58 π/32 o'clock, all obtained transverse super-resolution in the whole focal depth range.Thereby, o'clock can realize axial expansion depth of focus and transverse super-resolution simultaneously in Γ=58 π/32.

Experiment shows that the present invention has realized the real-time control of transverse super-resolution performance parameter (G and S), and the continuous variation of transmissivity realizes by extra electric field; Under the prerequisite that does not change former radial symmetry birefringece crystal structural parameters, the extended focal depth on having obtained axially, and can obtain transverse super-resolution simultaneously; Because the center bit phase delay of radial symmetry birefringece crystal can be adjusted by the electric light bit phase delay of electro-optic crystal, therefore its manufacturing process is required very strictness, more help practical application.

Claims (6)

1, a kind of electrically-controlled super-resolution pupil filter, it is characterized in that it is made up of the polarizer (1), electro-optic crystal (2), radial symmetry birefringece crystal (3) and analyzer (4), described electro-optic crystal (2) and radial symmetry birefringece crystal (3) place between the polarizer (1) and the analyzer (4), and the described polarizer (1) is parallel with the light transmission shaft of analyzer (4); The position angle of described electro-optic crystal (2) is determined according to the orientation of electro-induction main shaft, the angle of the light transmission shaft of the electro-induction slow axis and the polarizer (1) is θ=45 ° or 135 °, the slow-axis direction of radial symmetry birefringece crystal (3) is consistent with the slow-axis direction of electro-optic crystal (2), the added electric field size is determined according to the half-wave voltage of electro-optic crystal outside the electro-optic crystal (2), and the change in voltage scope is zero between 2 times the half-wave voltage.

2, electrically-controlled super-resolution pupil filter according to claim 1 is characterized in that its formation is: along the optical propagation direction polarizer (1), electro-optic crystal (2), radial symmetry birefringece crystal (3) and analyzer (4) successively.

3, electrically-controlled super-resolution pupil filter according to claim 1 is characterized in that it constitutes along optical propagation direction and is successively: the polarizer (1), radial symmetry birefringece crystal (3), electro-optic crystal (2) and analyzer (4).

4, electrically-controlled super-resolution pupil filter according to claim 1 is characterized in that Glan-Taylor prism that the described polarizer (1) and analyzer (4) are made for icelandspar, or is the polariscope or the polaroid of other types.

5, electrically-controlled super-resolution pupil filter according to claim 1 is characterized in that described electro-optic crystal (2) selects LiNbO for use ₃Or other have the electro-optic crystal of Pockels effect, and that electro-optic crystal (2) utilizes is LiNbO ₃Electrooptical coefficient γ ₂₂Cross electro-optical effect, if adopt other crystal then to determine to utilize cross electro-optical effect or longitudinal electro-optic effect according to its crystal class.

6, electrically-controlled super-resolution pupil filter according to claim 1 is characterized in that the uniaxial crystal of described radial symmetry birefringece crystal (3) for quartz crystal or other types.

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