CN102680117A - Common-path radial cutting liquid crystal phase shift interference wave-front sensor - Google Patents

Abstract

The invention discloses a common-path radial cutting liquid crystal phase shift interference wave-front sensor. The common-path radial cutting liquid crystal phase shift interference wave-front sensor is composed of a polarizer, a radial cutting system, an LC (Liquid Crystal Phase Modulator), a polarization analyzer, an imaging system and a computer. After a light beam to be detected enters into the wave-front sensor, the polarizer can be rotated, and the polarization direction of the incident light beam can be adjusted; then, two bundles of cutting light beams are formed after the incident light beam passes through the radial cutting system, the two bundles of the cutting light beams share the same light axis, the polarization directions of the two bundles of the cutting light beams are orthogonal, and the apertures of the two bundles of the cutting light beams are zoomed according to the same proportion; the two bundles of the cutting light beams can be directly irradiated to the LC, and the polarization directions of the LC and the enlarged light beams are kept the same; the computer drives the LC to introduce into N (N is larger than or equal to 3) different phase shifts between the cutting light beams, a polarized component, of which the polarization direction is consistent with that of the polarization analyzer, is obtained in the two bundles of the cutting light beams after passing through the polarization analyzer, and interference is generated; interference images are collected by the imaging system and are sequentially input into the computer in a time-division way, and the wave-front phase of the light beam to be detected can be reconstructed by analyzing and calculating. The common-path radial cutting liquid crystal phase shift interference wave-front sensor disclosed by the invention has the advantages that the structure of an optical system is simple, the impact of environmental vibration and non-common-path error can be restrained, the visibility of interference fringes is continuous and adjustable, and the wave-front detection accuracy is high.

Description

Be total to light path radial shear liquid crystal movable phase interfere Wavefront sensor

Technical field

The present invention relates to the Primary Component in a kind of adaptive optics, the Wavefront detecting technical field, refer in particular to a kind of light path radial shear liquid crystal movable phase interfere Wavefront sensor altogether.

Background technology

Wavefront sensor is the important Primary Component in the adaptive system, is used for surveying the Wave-front phase of incident beam.Can Wavefront sensor be divided into three major types according to the relation between measuring-signal and the corrugated: the first kind is to restore Wave-front phase, for example Hartmann wave front sensor, shearing interferometer etc. through measuring wavefront slope; Second type is to restore Wave-front phase, for example curvature Wavefront sensor through measuring wavefront curvature; The 3rd type is directly to restore Wave-front phase, and typical case's representative is a point-diffraction interferometer.

In all Wavefront sensors, Hartmann wave front sensor is the most commonly used.Its ultimate principle is: adopt microlens array that incident beam is cut apart, find the solution wavefront slope through the center-of-mass coordinate of each image patch on the measurement of Lens array focal plane and the difference of reference wavefront center-of-mass coordinate.Also can use the pyramid of a plurality of faceted pebbles that incident beam is carried out beam splitting, and then measure Wave-front phase (" Optical wavefront sensing system ", U.S. Pat 4399356).The Wavefront sensor of these two kinds of branch wavefront, sub-aperture number decision spatial sampling rate in order to improve measuring accuracy, thereby needs to increase sub-aperture number.Yet the increase of sub-aperture number purpose will propose higher requirement to the resolution of photoelectric detector.

The interference wave front sensor can be thought corresponding sub-aperture of each pixel in the interferogram so both can reduce the requirement to photoelectric detector resolution, can also effectively improve the spatial resolution of measurement result.Wherein a kind of interference wave front sensor is a point-diffraction interferometer, owing to adopt pin hole filtering, thereby the efficiency of light energy utilization is low, has so greatly limited the measurement range and detection accuracy (the Optics Express.15 (21): 13745-13756) of this device.Another kind of interference wave front sensor is a shearing interferometer, wherein, and the different multiframe lateral shear interferograms of shearing displacement on two mutual vertical direction of lateral shearing interference Technology Need, and require high to the validity of wave front restoration algorithm; And the radial shear interference technology is through enlarging incident beam and dwindle, thereby two light beams produce radial shear interference and solve Wave-front phase to be measured then, so the defective that does not have lateral shearing interference on the principle and run into.

At present, most radial shear interference technology adopt Mach-Zehnder interference structure (Appl.Opt.2008,47 (3): 372-376; Appl.Opt.2002,41 (19): 4013-4023), so that use phase shifter between two light beams, to introduce phase modulation (PM) (Opt.Letts.2007,32 (3): 232-234; Appl.Opt.2006,45 (15): 3409-3414).The advantage of this optical system is to adopt phase shift technology to find the solution Wave-front phase, and shortcoming is to shear light beam not to be total to the road, can not avoid the influence to measurement result of air turbulence and other environment labile factor.(Appl.Opt.1964,3 (7): 853-857), this optical system is because employing is total to the light path optical texture and compact conformation has simply obtained good application to propose loop radial shear interference system by Murty in 1964.To this optical system, existing solution is to produce the carrier wave interference striped through shearing in the light beam two after the introducing linear tilt, and the fourier transform method that adopts Takeda to propose is then found the solution (J.Opt.Soc.Am.1982,72 (1): 156-160; Opt.Letts.2005,30 (5): 492-494; Appl.Opt.2007,46 (34): 8305-8314).Because the boundary effect of fourier transform method makes the measuring accuracy of this method receive certain limitation; Simultaneously, owing to need to introduce than high carrier frequency, thereby the dynamic range of wavefront measurement is also lower.A kind of in addition " based on the common light path radial-shear interferometer of four steps space phase shift " (number of patent application: 201010034142.1), adopt two diverse locations of two photodetector CCD or four diverse locations of a photodetector CCD to gather four frame phase-shift interferences.Thereby need location matches exactly between a plurality of interferograms, and require to have consistent light transfer characteristic between the diverse location of same photodetector CCD or the different photodetector CCD; The optical system structure that relates to is complicated; Produce four groups of different optical device of light path experience of four interferograms, thereby inconsistent optical characteristics will cause problems such as beam split is inhomogeneous, phase shift is inaccurate between the similar optical device, thereby influence detection accuracy.

Summary of the invention

The technical matters that the present invention will solve provides a kind of light path radial shear liquid crystal movable phase interfere Wavefront sensor altogether; This Wavefront sensor is introduced light path radial shear interference system altogether with the liquid crystal phase modulation technique, has the characteristics of common light path and high measurement accuracy simultaneously; In addition,, can obtain maximum interference fringe contrast easily, further guarantee the precision of Wavefront detecting through the rotation polarizer owing to adopt the polarization spectro technology.It is low and based on the non-problem of light path shear interference system poor anti jamming capability altogether of phase shift wave front restoration technology that this sensor can solve present altogether light path shear interference commercial measurement precision; It has merged common light path, shear interference, liquid crystal phase modulation (PM), phase shift wave front restoration technology advantage separately well, has efficiency of light energy utilization height, interference fringe contrast height, anti-ambient vibration and characteristics such as the atmospheric interference ability is strong, self-reference interference, wave front restoration precision height.

The technical matters that the present invention will solve is realized by following scheme: be total to light path radial shear liquid crystal movable phase interfere Wavefront sensor, by polarizer P ₁, polarizing beam splitter mirror PBS, mirror M ₁And M ₂, lens L ₁And L ₂, liquid crystal phase-modulator LC, analyzer P ₂, lens L ₃And L ₄, photodetector CCD and computing machine form, wherein, polarizing beam splitter mirror PBS, mirror M ₁And M ₂, lens L ₁And L ₂Form the radial shear system; Liquid crystal phase-modulator LC, mirror M ₃With analyzer P ₂Form the movable phase interfere system; Lens L ₃And L ₄And photodetector CCD forms imaging system, the collection of completion interferogram.Lens L ₁And L ₂Can use public focus to form, also can use two positive lenss of public focus between two lens to form at the positive lens and the negative lens of the same side of lens.Said polarizer P ₁Place before the said radial shear system said polarizing beam splitter mirror PBS, mirror M ₁And M ₂Optical axis constitute a flat square triangle, lens L ₁And L ₂Place between this right-angle triangle, and the optical axis conllinear of the optical axis of two lens and this right-angle triangle formation, lens L ₁Near mirror M ₁, lens L ₂Near mirror M ₂, liquid crystal phase-modulator LC is perpendicular to direction of beam propagation and place after the radial shear system, and the polarization direction of LC is parallel with the polarization direction of amplifying light beam, analyzer P ₂Place between liquid crystal phase-modulator LC and the imaging system, its polarization direction all becomes 45 ° with amplification and the polarization direction that dwindles light beam.Two positive lenss constitute the 4f system in the imaging system, are used for the interferogram that produces is imaged in photodetector CCD target surface, can select rational focal length of lens ratio according to the physics size of photodetector CCD target surface size, image resolution ratio, interferogram.Computing machine is used to control liquid crystal phase-modulator LC and produces specific phase shift, and carries out wave front restoration and result's demonstration.Simultaneous computer links to each other with photodetector CCD through the A/D card and accomplishes the interferogram collection; Adopt the phase shift algorithm that phase-shift interference is carried out analytical calculation then and obtain twining phase place, further adopt phase-unwrapping algorithm to obtain expanded light beam and dwindle the phase differential of light beam in overlapping share zone; Adopt Zernike fitting process or cyclic iterative reconstruct Wave-front phase to be measured at last.

In the radial shear system, lens L ₁With lens L ₂Focal length be respectively f ₁And f ₂, and f ₁＞f ₂Df ₁/ f ₂The bore of decision expanded light beam, Df ₂/ f ₁The bore of light beam, (f are dwindled in decision ₂/ f ₁) ²Determine two light beams to shear ratio, wherein, D is the incident beam bore.

In the radial shear system, negative lens L ₁With positive lens L ₂Optical axis coincidence and focus coincide with the outside of two lens; Lens L ₁And L ₂Also can realize that at this moment the two optical axis coincidence and focus coincide with between two lens by two positive lenss.

Can be through rotation polarizer P ₁The interference fringe contrast of the maximum that obtains of angle.

Liquid crystal phase-modulator LC phase shift N time in wavefront measurement, N>=3, phase-shift phase is used δ _nExpression, n=1,2 ..., N, and maximum phase-shift phase δ _N＜2 π.The most frequently used phase shift algorithm has three step phase shift algorithms and four step phase shift algorithm, i.e. N=3 or N=4.

Light beam to be measured at first passes through polarizer P after getting into Wavefront sensor ₁Form linearly polarized light.The linearly polarized light that is divided into two bundle polarization direction quadratures then through polarizing beam splitter mirror PBS.Wherein, transmitted light beam is through mirror M ₂After pass through lens L successively ₂And L ₁Realize expanding bundle, promptly beam size enlarges.If lens L ₁, L ₂Focal length be respectively f ₁And f ₂, the incident beam bore is D, then the bore of expanded light beam is D ₁=Df ₁/ f ₂Expanded light beam is through mirror M ₂After incide PBS, all reflection gets into the movable phase interfere systems then.Folded light beam is through mirror M ₁After pass through lens L successively ₁And L ₂The realization bundle that contracts, promptly beam size dwindles, and the bore that dwindles light beam is D ₂=Df ₂/ f ₁Dwindle light beam through mirror M ₁After incide PBS, all transmissions get into the movable phase interfere system then.So light beam to be measured outgoing two after the radial shear system is restrainted common optical axis, bore respectively by the orhtogonal linear polarizaiton light that enlarges and dwindle.

The liquid crystal phase-modulator LC normal beam direction of propagation and placing after the radial shear system, its polarization direction is consistent with the polarization direction of expanded light beam.

Computer drives LC phase shift N (N>=3) is inferior, thereby can between two light beams, produce N different phase shifts δ successively _n(n=1,2 ..., N).Then through analyzer P ₂Obtain the polarized component that two light beams correspond respectively to the analyzer polarization direction, thereby interfere, and form N frame radial shear phase-shift interference thus.Through rotation polarizer P ₁Angle can obtain the interferogram of high-contrast.The timesharing of N frame radial shear phase-shift interference process imaging system is imaged on the same position of photodetector CCD successively, imports computing machine then and carries out the Wave-front phase that analytical calculation obtains light beam to be measured.

The present invention compared with prior art has following advantage:

1) compares with Hartmann wave front sensor; Light path radial shear liquid crystal movable phase interfere Wavefront sensor altogether of the present invention adopts interferometric method to survey Wave-front phase; Each pixel can be regarded a sub-aperture as among the photodetector CCD, thereby its detection accuracy and spatial resolution are high.

2) compare with a diffraction-type self-reference interference wave front sensor, the light path radial shear liquid crystal movable phase interfere Wavefront sensor efficiency of light energy utilization is high altogether, and the interference fringe contrast is high.

3) the radial shear interference technology based on the Mach-Zehnder interference structure belongs to non-light path system altogether; Though can easily adopt phase shift technology to find the solution Wave-front phase, it can not avoid the influence to measurement result of air turbulence and other environment labile factor.Light path radial shear liquid crystal movable phase interfere Wavefront sensor altogether of the present invention adopts light path optical texture altogether, and the anti-vibration ability is good, and range of application is wider.

4) tradition is total to light path shear interference technology and forms the carrier frequency interferogram through introducing the space linear modulation; Use the Fourier transform method to find the solution then, its measuring accuracy is low, to measure dynamic range little, high to the photodetector resolution requirement because the influence of boundary effect causes.Light path radial shear liquid crystal movable phase interfere Wavefront sensor altogether of the present invention adopts phase shift technology to restore Wave-front phase, has overcome the existing problem of fourier transform method fully, and algorithm is simple and measuring accuracy is high.

5) altogether light path radial shear liquid crystal movable phase interfere Wavefront sensor of the present invention adopts the liquid crystal phase-modulator as phase shifting device, phase-shift phase accurately and good reproducibility, thereby further guaranteed the precision of Wavefront detecting.

6) with " based on the common light path radial-shear interferometer of four steps space phase shift " (number of patent application: 201010034142.1) compare; That altogether light path radial shear liquid crystal movable phase interfere Wavefront sensor of the present invention has is simple in structure, phase shift accurately, to advantages such as photoelectric detector are less demanding, thereby measuring accuracy is high, the problem that do not have location matches between the inhomogeneous and interferogram of beam split.

Description of drawings

Fig. 1 is for adopting the common light path radial shear liquid crystal movable phase interfere Wavefront sensor structural principle synoptic diagram of transmission-type liquid crystal phase-modulator.

Fig. 2 is for adopting the common light path radial shear liquid crystal movable phase interfere Wavefront sensor structural principle synoptic diagram of reflection type liquid crystal phase-modulator.

Embodiment

As shown in Figure 1, this sensor is by polarizer P ₁1, polarizing beam splitter mirror PBS2, mirror M ₁3 and M ₂4, lens L ₁5 and L ₂6, liquid crystal phase-modulator LC7, mirror M ₃8, analyzer P ₂9, lens L ₃10 and L ₄11, photodetector CCD12 and computing machine 13 are formed, wherein, and polarizing beam splitter mirror PBS2, mirror M ₁3 and M ₂4, lens L ₁5 and L ₂6 form the radial shear system; Liquid crystal phase-modulator LC7, mirror M ₃8 with analyzer P ₂9 form the movable phase interfere system; Lens L ₃10 and L ₄11 and photodetector CCD12 form imaging system.Polarizer P ₁1 places before the said radial shear system polarizing beam splitter mirror PBS2, mirror M ₁3 and M ₂4 optical axis constitutes a flat square triangle, lens L ₁5 and L ₂6 place between this right-angle triangle, and the optical axis conllinear of the optical axis of two lens and this right-angle triangle formation, lens L ₁5 near mirror M ₁3, lens L ₂6 near mirror M ₂4, liquid crystal phase-modulator LC7 is perpendicular to direction of beam propagation and place after the radial shear system, and the polarization direction of liquid crystal phase-modulator LC7 is parallel with the polarization direction of amplifying light beam, analyzer P ₂9 place between liquid crystal phase-modulator LC7 and the imaging system, and its polarization direction all becomes 45 ° with amplification and the polarization direction that dwindles light beam.Light beam to be measured is through polarizer P ₁1 forms linearly polarized light, is divided into the linearly polarized light of two bundle polarization direction quadratures then through polarizing beam splitter mirror PBS2.Wherein, the reflected ray light beam is through mirror M ₁Pass lens L after 3 successively ₁5 and L ₂6 realize contracting bundle (beam size dwindles); And the radioparent light beam is through mirror M ₂Pass lens L after 4 successively ₂6 and L ₁5 realize expanding bundle (beam size expansion).

As shown in Figure 2, liquid crystal phase-modulator LC7 can be transmission-type LC, also can be reflective LC.The two difference is that when using reflective LC, needing increases a beam splitter BS14 between LC7 and radial shear system, will lose a part of luminous energy in this case.

If lens L ₁5 and L ₂6 focal length is respectively f ₁And f ₂, and f ₁＞f ₂, the incident beam bore is D, then the bore of expanded light beam is D ₁=Df ₁/ f ₂, the bore that dwindles light beam is D ₂=Df ₂/ f ₁Expanded light beam with dwindle light beam and incide PBS2 respectively after, all reflection or transmission get into the movable phase interfere system.The result is by radial shear system outgoing two bundle common optical axis, a branch of by a branch of orhtogonal linear polarizaiton light that is dwindled of expansion.If two light beams are sheared than being s, then have:

s ²＝D ₂/D ₁＝(f ₂/f ₁) ²……………………………(1)

Liquid crystal phase-modulator LC7 is placed on after the radial shear system, and the polarization direction of LC7 is consistent with the polarization direction of expanded light beam.It is inferior that computing machine 13 drives LC7 phase shift N (N>=3), produces N different phase shifts amount δ successively thereby can shear between the light beam two _n(n=1,2 ..., N).Then through analyzer P ₂9 obtain two light beams corresponds respectively to P ₂The polarized component of 9 polarization directions, thus interfere, and form N frame radial shear phase-shift interference I thus _n, be expressed as

I _n(x/s，y/s)＝a(x/s，y/s)+b(x/s，y/s)cos[ΔΦ(x/s，y/s)-δ _n]……………(2)

Wherein (x/s, y/s) the light beam phase differential is sheared in expression to ΔΦ.

Than s, rotate polarizer P according to known shearing ₁1 makes the contrast of interferogram reach the highest, contrast K and P ₁Relation between 1 the anglec of rotation θ (θ ∈ (0, pi/2)) is shown in (3) formula:

$K=\frac{2\sqrt{{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HSA00000726402800011.png,HSA00000726402800012.png"\; state="\{\{state\}\}">D</figure-callout>}}_2/{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="HSA00000726402800011.png,HSA00000726402800012.png"\; state="\{\{state\}\}">D</figure-callout>}}_1\tan \mathrm{\&theta;}}}{{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HSA00000726402800011.png,HSA00000726402800012.png"\; state="\{\{state\}\}">D</figure-callout>}}_2/{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="HSA00000726402800011.png,HSA00000726402800012.png"\; state="\{\{state\}\}">D</figure-callout>}}_1+\tan \mathrm{\&theta;}}=\frac{2{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="HSA00000726402800011.png,HSA00000726402800012.png"\; state="\{\{state\}\}">f</figure-callout>}}_2/{\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="HSA00000726402800011.png,HSA00000726402800012.png"\; state="\{\{state\}\}">f</figure-callout>}}_1\sqrt{\tan \mathrm{\&theta;}}}{{({\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="HSA00000726402800011.png,HSA00000726402800012.png"\; state="\{\{state\}\}">f</figure-callout>}}_2/f_1)}^2+\tan \mathrm{\&theta;}}=\frac{2s\sqrt{\tan \mathrm{\&theta;}}}{{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="HSA00000726402800011.png,HSA00000726402800012.png"\; state="\{\{state\}\}">s</figure-callout>}}^2+\tan \mathrm{\&theta;}}...\left(3\right)$

As θ=arctan (s ²) time, interference fringe contrast the highest (equaling 1).The radial shear phase-shift interference is gathered by photodetector CCD12 through imaging system, imports the phase shift algorithm shown in the computing machine 13 and (4) formula of use then and finds the solution the winding phase differential:

$\mathrm{\&Delta;\&Phi;}(x/s,y/s)=\arctan \left[\frac{\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{I}_n(x/s,y/s)\sin \left({\mathrm{\&delta;}}_n\right)}{\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{I}_n(x/s,y/s)\cos \left({\mathrm{\&delta;}}_n\right)}\right]....\left(4\right)$

Further adopt document " Robust phase-unwrapping techniques:a comparison " (J.Opt.Soc.Am.A.1996; 13 (12): the method 2355-2366) is carried out phase unwrapping to the result of calculation of (4) formula; Obtain separating after the winding expanded light beam with dwindle the shearing phase difference ΔΦ of light beam in the overlapping region (x/s, y/s).

(x/s y/s) restores original wavefront Φ to be measured by shearing phase difference ΔΦ to use any one algorithm in following two kinds of algorithms ₀(x, y).

1) first kind of algorithm is the Zernike fitting process.Original wavefront uses the linear expression of Zernike orthogonal basis to be:

${\mathrm{\&Phi;}}_0(x,y)=\underset{k=0}{\overset{N}{\mathrm{\&Sigma;}}}{a}_k{Z}_k(x,y)...\left(5\right)$

Wherein, Z _k(x, y) expression Zernike orthogonal basis, a _kRepresent k rank Zernike coefficient.

Can draw (6) formula according to (5) formula:

$\mathrm{\&Delta;\&Phi;}(x/s,y/s)=\underset{k=0}{\overset{M}{\mathrm{\&Sigma;}}}{a}_k{Z}_k(x/s,y/s)...\left(6\right)$

Wherein,

ΔZ _k(x/s，y/s)＝Z _k(x/s，y/s)-Z _k(x·s，y·s)……………………(7)

Utilize least square method to obtain a to (6) formula _k(k=0,1 ... M) bring into after in (5) formula, can obtain original phase Φ to be measured ₀(x, y).

2) second kind of algorithm is cyclic iterative.The polar form of shearing phase difference is expressed as:

ΔΦ(r/s，φ)＝Φ ₀(r/s，φ)-Φ ₀(r·s，φ)………………………(8)

Wherein, Φ ₀(r/s, φ) and Φ ₀(rs, φ) light beam and expanded light beam Wave-front phase are dwindled in expression respectively.With s ²Multiply by the radially variable r of (8) formula the right and left, have:

ΔΦ(r·s，φ)＝Φ ₀(r·s，φ)-Φ ₀(r·s ³，φ)………………………(9)

Repeat above step M time, and add up about all equalities that will obtain, obtain (10) formula:

${\mathrm{\&Phi;}}_0(r/s,\mathrm{\&phi;})=\underset{k=0}{\overset{M}{\mathrm{\&Sigma;}}}\mathrm{\&Delta;\&Phi;}(r\&CenterDot;s^{2k-1},\mathrm{\&phi;})+{\mathrm{\&Phi;}}_0(r\&CenterDot;s^{2M+1},\mathrm{\&phi;})...\left(10\right)$

Carry out to obtain original wavefront phase place to be measured after the repeatedly loop iteration computing according to (10) formula.

Polarizer P ₁1, analyzer P ₂9, polarizing beam splitter mirror PBS2, catoptron and lens are optical element commonly used, need not particular design.

Claims (1)

1. be total to light path radial shear liquid crystal movable phase interfere Wavefront sensor, it is characterized in that: by polarizer P ₁, polarizing beam splitter mirror PBS, mirror M ₁And M ₂, lens L ₁And L ₂, liquid crystal phase-modulator LC, analyzer P ₂, lens L ₃And L ₄, photodetector CCD and computing machine form.Wherein, polarizing beam splitter mirror PBS, mirror M ₁And M ₂, lens L ₁And L ₂Form the radial shear system; Liquid crystal phase-modulator LC, mirror M ₃With analyzer P ₂Form the movable phase interfere system; Lens L ₃And L ₄And photodetector CCD forms imaging system.Said polarizer P ₁Place before the said radial shear system; Said polarizing beam splitter mirror PBS, mirror M ₁And M ₂Optical axis constitute a flat square triangle, lens L ₁And L ₂Place between this right-angle triangle, and the optical axis conllinear of the optical axis of two lens and this right-angle triangle formation, lens L ₁Near mirror M ₁, lens L ₂Near mirror M ₂, lens L ₁With lens L ₂Focus overlap lens L ₁Focal length greater than lens L ₂Focal length; Liquid crystal phase-modulator LC is perpendicular to direction of beam propagation and place after the radial shear system, and the polarization direction of LC is parallel with the polarization direction of amplifying light beam; Analyzer P ₂Place between liquid crystal phase-modulator LC and the imaging system, its polarization direction all becomes 45 ° with amplification and the polarization direction that dwindles light beam.

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