CN105651493A - Wave aberration detecting system and method with knife edge as detection marker - Google Patents

Abstract

The invention discloses a wave aberration detecting system with a knife edge as a detection marker and a wave aberration detecting method based on the knife-edge testing technology and the Ptychography technology. The wave aberration detecting system comprises a coherent point light source, a knife-edge graph serving as the detection marker, a detection-marker adjusting displacement platform for fixing the knife-edge graph and a two-dimensional photoelectric sensor. As the wave aberration of a to-be-detected projection lens is detected through the wave aberration detecting system, the system structure can be simplified, the collecting times of an observation surface pattern are decreased, and the detecting speed and the detecting accuracy of the system are increased.

Description

Utilize the edge of a knife as the wave aberration detection system and the detection method that detect labelling

Technical field

The present invention relates to wave aberration detection system and detection method, particularly a kind of utilize the edge of a knife as the wave aberration detection system of detection labelling and based on the wave aberration detection method of edge of a knife measuring technology and scanning coherent diffraction imaging (Ptychography) technology.

Background technology

Wave aberration detection technique substantially can be divided into two big classes: a class is based on the wave aberration detection technique of pupil planar survey, including Shack-Hartmann sensor, point-diffraction interferometer and shearing interferometer etc.; The another kind of wave aberration detection technique being based on aerial image measurement. Two class technical style totally different each aobvious eternal lasting. From technological means, the former extracts wavefront information (as Shack-Hartmann sensor extracts the differential data of wave aberration from ray aberration, shearing interferometer extracts the differential data of wave aberration from interference strength) by certain technological means from present detection results; The latter then utilizes light propagation process by the wave aberration in the aerial image inverting emergent pupil face recorded. From Numerical Implementation, the former generally first obtains the differential data of wave aberration, then adopts certain numerical method (such as RimmerMethod) to be obtained wave aberration data by the differential data of wave aberration again; The latter then looks for optimal solution by the iteration optimization of light propagation process, directly obtains wave aberration data. From range of application, the process of iteration optimization it is absent from based on the wave aberration detection technique of pupil planar survey, thus calculating, speed and stability are better than the wave aberration detection technique measured based on aerial image, but the former system structure relative complex, and it is increasingly difficult to overcome systematic error when being applied to the optical system of large-numerical aperture and low photon flux; Although and the wave aberration detection technique measured based on aerial image is limited to, in calculating speed and stability, the iterative algorithm and iterations that adopt, but its advantage is in that system structure is relatively easy, to systematic error relative insensitivity, this particularly embodies when being applied to the optical system of large-numerical aperture and low photon flux. What the present invention relates to utilizes the edge of a knife as the wave aberration detection technique being namely based on aerial image measurement of the wave aberration detection system employing of detection labelling, and it inherits the simple advantage of this technical pattern, does not lose accuracy of detection simultaneously.

The wave aberration detection technique based on aerial image measurement that the present invention relates to has used for reference edge of a knife measuring technology and the thought of scanning coherent diffraction imaging (Ptychography) technology.Edge of a knife measuring technology is (referring in first technology 1, L.M.Foucault, Descriptiondesprocedesemployespourreconnaitrelaconfigura tiondessurfacesoptiques, C.R.Acad.Sci.Paris, 47,958,1858) principle is to treat focal plane or the image planes of examining system with edge of a knife cutting, inspection surface after focal plane or image planes can obtain between all light and complete dark between near uniform echo, be distributed according to the light and shade of echo and can determine whether to treat the wave aberration of examining system. the advantage of this measuring method is simple in construction, easy to operate, highly sensitive, it is simple to Site Detection, but comparison of ingredients is big qualitatively. the edge of a knife measuring technology improved is (referring in first technology 2, DonaldE.Vandenberg, WilliamD.Humbel, AlanWertheimer, " QuantitativeevaluationofopticalsurfacesusinganimprovedFo ucaulttestapproach ", Proc.SPIE1542, ActiveandAdaptiveOpticalSystems, 534, December1, 1991) quantitative analysis can be carried out, but need to gather a series of echo to determine the knife-edge positions corresponding to the details in a play not acted out on stage, but told through dialogues threshold value of each pixel at inspection surface, this not only needs extra equipment and operation, add the complexity of detection equipment and the testing time of system, and accuracy of detection is also limited by the mobile accuracy of the edge of a knife and the collecting quantity of echo. Ptychography technology is (referring in first technology 3, J.M.RodenburgandH.M.L.Faulkner, " Aphaseretrievalalgorithmforshiftingillumination ", AppliedPhysicsLetters85, 4795, 2004) it is a kind of phase recuperation technique, corresponding Phase Retrieve Algorithm is called PIE (PtychographicIterativeEngine) algorithm, its principle is to be irradiated to by lighting light wave on detection labelling, detection is marked at and is perpendicular in the plane of optical axis and does step-scan, the scanning of each step all overlaps with previous step, the diffraction pattern that the detection of inspection surface record is formed when being marked at often step scanning, by detecting the computing that iterates of light propagation process between labelling place plane and inspection surface, obtain lighting light wave or the phase information of detection labelling. owing to the result when recovering often step scanning respectively also to meet the constraint of other scanning results simultaneously, last restoration result will be the common solution of all scanning results, and this is also that the recovery precision of PIE algorithm compares to the reason that conventional phase recovery algorithms (such as GS algorithm, input/output method) is high. PIE algorithm is initially applied to recover detection labelling when known lighting light wave, and it is also feasible (referring in first technology 4 in fact recovering lighting light wave by known detection labelling, AntoineWojdylaa, RyanMiyakawaa, PatrickNaulleaua, " Ptychographicwavefrontsensorforhigh-NAEUVinspectionandex posuretools ", Proc.ofSPIE, Vol.9048,9048392014SPIE), so the method may apply in projection objective wave aberration detection field. Though Ptychography technology can realize high-precision measurement in being applied to wave aberration detection field, but have the disadvantage that 1) introduce the complicated detection labelling of pattern and needs take multiple scan operation, add the complexity of detection equipment and the testing time of system, 2) spatial distribution detecting labelling is difficult to accurate measurement, 3) the detection labelling under Multiple-Scan is difficult to accurately determine relative to the position of lighting light wave.

Summary of the invention

It is an object of the invention in conjunction with the above-mentioned advantage in first technology, overcome the above-mentioned deficiency in first technology, it is provided that a kind of utilize the edge of a knife wave aberration detection system as detection labelling and the wave aberration detection method based on edge of a knife measuring technology and Ptychography technology. This wave aberration detection system can simplied system structure, reduce the times of collection of inspection surface pattern, improve the detection speed of system and precision.

The technical solution of the present invention is as follows:

A kind of utilize the edge of a knife as detection labelling wave aberration detection system, including coherent point light sources, along the edge of a knife figure that this coherent point light sources direction of beam propagation is as detection labelling successively, the detection labelling fixing this edge of a knife figure regulates displacement platform and two-dimension photoelectric sensor, projection objective to be measured is placed between described coherent point light sources and described edge of a knife figure, described coherent point light sources is positioned on the object plane of described projection objective to be measured, described edge of a knife figure is fixed on described detection labelling and regulates on displacement platform, and it is placed in the image planes of described projection objective to be measured by detecting labelling adjustment displacement platform, described two-dimension photoelectric sensor is positioned on the inspection surface after projection objective image planes to be measured, distance between inspection surface and image planes makes on inspection surface the diameter of effective light spot less than the diameter of two-dimension photoelectric sensor photosurface,

The output numerical aperture of described coherent point light sources is more than the object-side numerical aperture of described projection objective to be measured;

The two-value figure that described edge of a knife figure is made up of lightproof part and light transmission part, this two-value figure contains n bar edge of a knife demarcation line, n >=3, and the marginal length of the edge of a knife is more than the diameter of projection objective image planes hot spot to be measured; It is XYZ three-shaft displacement platform that described detection labelling regulates displacement platform, edge of a knife figure is fixed in the image planes of projection objective to be measured by it, and make edge of a knife figure wherein edge of a knife demarcation line cut the image planes hot spot of projection objective to be measured, and make this edge of a knife demarcation line distance with optical axis at 0.5 ��/NA_iWithin, wherein NA_iIt it is the image-side numerical aperture of projection objective to be measured.

Described two-dimension photoelectric sensor is CCD, CMOS, or 2 D photoelectric detector array.

The described method utilizing the edge of a knife to carry out wave aberration detection as the wave aberration detection system detecting labelling, comprises the steps of

1. the output numerical aperture coherent point light sources more than the object-side numerical aperture of projection objective to be measured is selected, this coherent point light sources is placed on the object plane of projection objective to be measured, the coherent light that coherent point light sources sends is made to image in the image planes of projection objective to be measured after entering projection objective to be measured, two-dimension photoelectric sensor is placed on the inspection surface after projection objective image planes to be measured, distance between these inspection surface and image planes can make on inspection surface the diameter of effective light spot less than the diameter of two-dimension photoelectric sensor photosurface, diffraction pattern I on inspection surface when described two-dimension photoelectric sensor record is without the edge of a knife₀(u, v), wherein u, v are system coordinate on inspection surface;

2. edge of a knife figure is fixed on detection labelling and regulates on displacement platform, adjust described detection labelling along optical axis direction and regulate the position of displacement platform, edge of a knife figure is made to be positioned in the image planes of described projection objective to be measured, in the plane of vertical optical axis, adjust detection labelling regulate the position of displacement platform, make the image planes hot spot of an edge of a knife figure wherein edge of a knife demarcation line cutting projection objective to be measured, and the distance of edge of a knife demarcation line and optical axis is at 0.5 ��/NA_iWithin, the diffraction pattern I on two-dimension photoelectric sensor record now inspection surface₁(u, v);

3. optimize following object function, obtain the edge of a knife demarcation line function a under current direction₁x+b₁Two parameter a of y=1₁,b₁:

$\underset{a_1,b_1}{\min }\frac{\underset{x,y}{\Σ}{P}_0(x,y)P_0^{*}(x,y)B_1(x,y)}{\underset{x,y}{\Σ}{P}_0(x,y)P_0^{*}(x,y)}-\frac{\underset{u,v}{\Σ}{I}_1(u,v)}{\underset{u,v}{\Σ}{I}_0(u,v)}$

Wherein P₀(x, y) for system optical field distribution in projection objective image planes to be measured in aberrationless situation,For P₀(x, conjugation y), B₁(x, y) for the edge of a knife function under current direction, it is by edge of a knife demarcation line function a₁x+b₁The two-valued function that y=1 determines:

$B_1(x,y)=\left\{\begin{array}{cc}0& a_{1}x+b_{1}y\≤1\\ 1& a_{1}x+b_{1}y>1\end{array}\right.$

X, y are system coordinate in projection objective image planes to be measured;

4. in the plane of vertical optical axis, adjust detection labelling regulate the position of displacement platform, make other n-1 bar edge of a knife demarcation line of edge of a knife figure cut the image planes hot spot of projection objective to be measured successively, and make the edge of a knife demarcation line distance with optical axis at 0.5 ��/NA_iWithin, two-dimension photoelectric sensor records edge of a knife diffraction pattern I on inspection surface under other n-1 direction_i(u, v), wherein i=2 ..., n; Repeat step 3., obtain the edge of a knife function B under other n-1 direction_i(x, y), wherein i=2 ..., n; The selection principle of n is: making the overlapping rate of adjacent edge of a knife function light transmission part on the one hand more than 30%, making all edge of a knife functions logic sum in each position on the other hand is 1, namely

B₁(x,y)��B₂(x,y)�š���B_n(x, y) �� 1, wherein �� represents logic add;

5. following iterative process is performed:

By the grading function P guessed_g(x, y) with edge of a knife function B_i(x, product y) obtains the outgoing light field of conjecture:

Wherein the grading function of initial guess is system optical field distribution P in projection objective image planes to be measured in aberrationless situation₀(x, y), B₀(x, y) �� 1;

Outgoing light field to conjectureDo fresnel diffraction conversion and obtain the diffractive light field of conjecture:

Wherein FST{ } represent fresnel diffraction conversion;

By I_i(u, v) the diffractive light field �� to conjecture_g,i(u, v) carries out the diffractive light field that amplitude constraint obtains updating:

${\mathrm{\ψ}}_{c,i}(u,v)=\sqrt{I_i(u,v)}\frac{{\mathrm{\ψ}}_{g,i}(u,v)}{\left|{\mathrm{\ψ}}_{g,i}(u,v)\right|},i=0,1,2,\mathrm{...},n$

To the diffractive light field �� updated_{C, i}(u, v) makes the outgoing light field that fresnel diffraction inverse transformation obtains updating:

Wherein FST^-1{ } represents fresnel diffraction inverse transformation;

Update grading function:

Above-mentioned iterative process reaches abundant hour to terminate with the error sum of squares SSE between diffractive light field and the diffractive light field of conjecture of renewal, and SSE expression formula is as follows:

$SSE=\frac{\underset{u,v}{\Σ}{\left(\right|{\mathrm{\ψ}}_c(u,v)|-|{\mathrm{\ψ}}_g(u,v)\left|\right)}^2}{MN}$

Wherein MN is sampling number total in exit wave function matrix;

6. the grading function P 5. finally given by step_c(x, y) cast to the pupil plane of projection objective to be measured (2) through light field adverse transference and remove a quadratic phase factor being equivalent to perfect lens and obtain the pupil function of projection objective to be measured (2), extract the phase place of pupil function, the wave aberration of projection objective to be measured (2) can be obtained.

The operation principle of the present invention is as follows:

Projection objective pupil function H (X, Y) to be measured can be represented by pupil transmittance function t (X, Y) and wavefront aberration function W (X, Y):

H (X, Y)=t (X, Y) exp (jkW (X, Y))

Wherein, X, Y is system coordinate on projection objective pupil plane to be measured;

It is pupil function H (X from the wave function of pupil plane outgoing, Y) and one quadratic phase factor L (X being equivalent to perfect lens, Y) long-pending, this wave function propagate to projection objective back focal plane to be measured, form PIE algorithm lighting light wave P (x, y):

P (x, y)=FST{H (X, Y) L (X, Y) }

Due to diffraction effect, (x, y) is not ideal image point, but diffraction pattern, and the radius of zero level bright spot of view-field center is at least 0.61 ��/NA for the light field P of projection objective back focal plane to be measured_i(due to the existence of wave aberration, the radius of actual zero level bright spot of view-field center can more than 0.61 ��/NA_i), edge of a knife figure is placed in the image planes of projection objective to be measured, and makes the image planes hot spot of an edge of a knife figure wherein edge of a knife demarcation line cutting projection objective to be measured, and make the edge of a knife demarcation line distance with optical axis at 0.5 ��/NA_iWithin, now edge of a knife function be B (x, y), inspection surface formed between all light and complete dark between near uniform visual field I (u v), is arranged on 0.5 ��/NA the distance of edge of a knife demarcation line Yu optical axis_iWithin be to ensure that the visual field that inspection surface is formed will not be too light or too dark.

The communication process of light field meets preservation of energy, it may be assumed that

�ҡ�P(x,y)P^*(x, y) B (x, y) dxdy=�� �� I (u, v) dudv

After above formula discretization, it is represented by:

$\mathrm{\δ}x\mathrm{\δ}y\underset{x,y}{\Σ}P(x,y)P^{*}(x,y)B(x,y)=\mathrm{\δ}u\mathrm{\δ}v\underset{u,v}{\Σ}I(u,v)$

Eliminate detection tag plane and the impact in inspection surface sampling interval, have:

$\frac{\underset{x,y}{\Σ}P(x,y)P^{*}(x,y)B(x,y)}{\underset{x,y}{\Σ}P(x,y)P^{*}(x,y)}=\frac{\underset{u,v}{\Σ}I(u,v)}{\underset{u,v}{\Σ}{I}_0(u,v)}$

Edge of a knife function B (x, y) is determined by two parameter a, the b of edge of a knife demarcation line function ax+by=1, with system in aberrationless situation the optical field distribution in projection objective image planes to be measured as the grading function P of initial guess₀(x, y)=FST{t (X, Y) L (X, Y) } (x y), and optimizes following object function to substitute the P in above formula

$\underset{a,b}{min}\frac{\underset{x,y}{\Σ}{P}_0(x,y)P_0^{*}(x,y)B(x,y)}{\underset{x,y}{\Σ}{P}_0(x,y)P_0^{*}(x,y)}-\frac{\underset{u,v}{\Σ}I(u,v)}{\underset{u,v}{\Σ}{I}_0(u,v)}$

Can try to achieve relatively accurate edge of a knife function B (x, y).

The image planes hot spot of projection objective to be measured is cut in other edge of a knife demarcation line making edge of a knife figure successively, and makes the edge of a knife demarcation line distance with optical axis at 0.5 ��/NA_iWithin, obtain n edge of a knife function and n corresponding diffraction pattern, the selection principle of n is: make the overlapping rate of adjacent edge of a knife function light transmission part on the one hand more than 30%, making all edge of a knife functions logic sum in each position on the other hand is 1, the former is to ensure that the restoration result obtained by a certain diffraction pattern is subject to the constraint of the restoration result obtained by next diffraction pattern, and the latter is to ensure that all regions of grading function can be returned to by following iterative algorithm.

Perform following iterative process:

By the grading function P guessed_g(x, y) with edge of a knife function B_i(x, product y) obtains the outgoing light field of conjecture:

Wherein the grading function of initial guess is P₀(x, y), B₀(x, y) �� 1;

Outgoing light field to conjectureDo fresnel diffraction conversion and obtain the diffractive light field of conjecture:

Wherein FST{ } represent fresnel diffraction conversion;

By I_i(u, v) the diffractive light field �� to conjecture_g,i(u, v) carries out the diffractive light field that amplitude constraint obtains updating:

${\mathrm{\ψ}}_{c,i}(u,v)=\sqrt{I_i(u,v)}\frac{{\mathrm{\ψ}}_{g,i}(u,v)}{\left|{\mathrm{\ψ}}_{g,i}(u,v)\right|},i=0,1,2,...,n$

To the diffractive light field �� updated_c,i(u, v) makes the outgoing light field that fresnel diffraction inverse transformation obtains updating:

Wherein FST^-1{ } represents fresnel diffraction inverse transformation;

By the outgoing light field updatedUpdate grading function:

Above-mentioned iterative process reaches abundant hour to terminate with the error sum of squares SSE between diffractive light field and the diffractive light field of conjecture of renewal, and SSE expression formula is as follows:

$SSE=\frac{\underset{u,v}{\Σ}{\left(\right|{\mathrm{\ψ}}_c(u,v)|-|{\mathrm{\ψ}}_g(u,v)\left|\right)}^2}{MN}$

Wherein MN is sampling number total in exit wave function matrix;

Owing to edge of a knife restoration result under each direction also to meet edge of a knife constraint of restoration result under other direction, last restoration result P simultaneously_c(x will be y) the common solution of all restoration results, therefore have significantly high precision.

By the grading function P recovered_c(x, y) cast to the pupil plane of projection objective to be measured through light field adverse transference and remove a quadratic phase factor L (X being equivalent to perfect lens, Y) the pupil function H (X of projection objective to be measured is obtained, Y), extract the phase place of pupil function, the wave aberration W (X, Y) of projection objective to be measured can be obtained.

With compared with first technology, the invention have the advantages that

1. with compared with first technology [1], both inherited this technical pattern simple, easy to operate advantage, achieve again high-precision detection by quantitative.

2. with compared with first technology [2], it is not necessary to repeatedly move the edge of a knife, it is not necessary to inspection surface gather a series of diffraction patterns, the impact by edge of a knife mobile accuracy and diffraction pattern collecting quantity is smaller, improves detection speed and the precision of system.

3. with compared with first technology [3] and [4], it is not necessary to complicated detection labelling, it is not necessary to detection labelling is taken multiple scan, simplifies system structure, improve the detection speed of system. Due to the two-valued function that edge of a knife function is made up of lightproof part and light transmission part, can accurately obtain the spatial distribution of detection labelling as detection labelling with the edge of a knife; Owing to edge of a knife function is only determined by edge of a knife demarcation line function, can accurately obtain the detection labelling position relative to lighting light wave according to the law of conservation of energy in light propagation process; By having exact space distribution and having the detection labelling of higher registration accuracy to be applied in recovery algorithms with lighting light wave, improve the recovery precision of lighting light wave, and then improve the accuracy of detection of system wave aberration.

Accompanying drawing explanation

Fig. 1 is that the present invention utilizes the edge of a knife as the wave aberration detection system index path of detection labelling;

Fig. 2 is a kind of implementation of coherent point light sources of the present invention;

Fig. 3 is the schematic diagram that the present invention realizes the filtering aperture of coherent point light sources;

Fig. 4 A is the present invention a kind of implementation containing four edge of a knife marginal edge of a knife figures;

Fig. 4 B is the present invention another kind of implementation containing four edge of a knife marginal edge of a knife figures;

Fig. 5 is the present invention a kind of implementation containing five edge of a knife marginal edge of a knife figures.

Detailed description of the invention

Below in conjunction with embodiment and accompanying drawing, the invention will be further described, but should not limit the scope of the invention with this embodiment.

Fig. 1 is that the present invention utilizes the edge of a knife as the wave aberration detection system index path of detection labelling, including coherent point light sources 1, along this point source 1 direction of beam propagation be projection objective 2 to be measured successively, detection labelling as the edge of a knife figure 3 of detection labelling, fixing edge of a knife figure regulate displacement platform 4 and two-dimension photoelectric sensor 5. Described coherent point light sources 1 is positioned on the object plane of described projection objective to be measured 2, described edge of a knife figure 3 is fixed on described detection labelling and regulates on displacement platform 4, and it is placed in the image planes of described projection objective to be measured 2 by detecting labelling adjustment displacement platform 4, described two-dimension photoelectric sensor 5 is positioned on the inspection surface after projection objective 2 image planes to be measured, and the distance between inspection surface and image planes makes the diameter of effective light spot on inspection surface be slightly less than the diameter of two-dimension photoelectric sensor 5 photosurface;

Described coherent point light sources 1 (referring to Fig. 2) is made up of coherent source 101, focus lamp 102 and filtering aperture 103, and its output numerical aperture is more than the object-side numerical aperture of described projection objective to be measured 2; Described filtering aperture 103 (referring to Fig. 3) is the diameter logical light circular hole less than projection objective 2 thing side to be measured resolution, and its diameter is less than 0.5 ��/NA_O, wherein NA_OObject-side numerical aperture for projection objective 2 to be measured;

The two-value figure that described edge of a knife figure 3 is made up of lightproof part and light transmission part, and containing at least three edge of a knife demarcation line, described detection labelling regulates displacement platform 4 and is fixed in the image planes of projection objective 2 to be measured by described edge of a knife figure 3, and make edge of a knife figure 3 wherein edge of a knife demarcation line cut the image planes hot spot of projection objective 2 to be measured, and make the edge of a knife demarcation line distance with optical axis at 0.5 ��/NA_iWithin, wherein NA_iImage-side numerical aperture for projection objective 2 to be measured;

Described two-dimension photoelectric sensor 5 is CCD, CMOS, or 2 D photoelectric detector array;

In the present embodiment, the output numerical aperture of coherent point light sources 1 is 0.1, and wherein the wavelength of coherent source 101 is 532nm, and the diameter of filtering aperture 103 is 1um; Edge of a knife figure 3 (referring to Fig. 4 A and Fig. 4 B) is containing four edge of a knife demarcation line, article four, edge of a knife demarcation line is 301,302,303,304 respectively, they achieve the edge of a knife under four direction, and four edge of a knife demarcation line length are 10mm, much larger than the diameter of projection objective 2 image planes hot spot to be measured; The object-side numerical aperture of projection objective 2 to be measured is NA_O=0.06, image-side numerical aperture is NA_i=0.3; Two-dimension photoelectric sensor 5 is CCD, and pixel count is 1200*1600, and pixel resolution is 7.4um.

The described method utilizing the edge of a knife to carry out wave aberration detection as the wave aberration detection system detecting labelling, comprises the steps of

1. the coherent light that described coherent point light sources 1 sends images in the image planes of projection objective 2 to be measured after entering described projection objective to be measured 2, described two-dimension photoelectric sensor 5 is positioned on the inspection surface after projection objective 2 image planes to be measured, the diffraction pattern I on inspection surface when two-dimension photoelectric sensor 5 record is without the edge of a knife₀(u, v), wherein u, v are system coordinate on inspection surface;

2. described edge of a knife figure 3 is fixed on described detection labelling and regulates on displacement platform 4, the position detecting labelling adjustment displacement platform 4 along optical axis direction adjustment makes edge of a knife figure 3 be positioned in the image planes of described projection objective to be measured 2, the position adjusting detection labelling adjustment displacement platform 4 in the plane of vertical optical axis makes the image planes hot spot of an edge of a knife figure 3 wherein edge of a knife demarcation line cutting projection objective 2 to be measured, and makes the edge of a knife demarcation line distance with optical axis at 0.5 ��/NA_iWithin, two-dimension photoelectric sensor 5 records the diffraction pattern I on now inspection surface₁(u, v);

3. optimize following object function, obtain the edge of a knife demarcation line function a under current direction₁x+b₁Two parameter a of y=1₁,b₁:

$\underset{a_1,b_1}{\min }\frac{\underset{x,y}{\Σ}{P}_0(x,y)P_0^{*}(x,y)B_1(x,y)}{\underset{x,y}{\Σ}{P}_0(x,y)P_0^{*}(x,y)}-\frac{\underset{u,v}{\Σ}{I}_1(u,v)}{\underset{u,v}{\Σ}{I}_0(u,v)}$

Wherein P₀(x, y) for system optical field distribution in projection objective 2 image planes to be measured in aberrationless situation, is also the grading function of step 5. middle initial guess,For P₀(x, conjugation y), B₁(x, y) for the edge of a knife function under current direction, it is by edge of a knife demarcation line function a₁x+b₁The two-valued function that y=1 determines:

$B_1(x,y)=\left\{\begin{array}{cc}0& a_{1}x+b_{1}y\≤1\\ 1& a_{1}x+b_{1}y>1\end{array}\right.$

X, y are system coordinate in projection objective image planes to be measured;

4. the position adjusting detection labelling adjustment displacement platform 4 in the plane of vertical optical axis makes other three edge of a knife demarcation line of edge of a knife figure 3 cut the image planes hot spot of projection objectives 2 to be measured successively, and makes the edge of a knife demarcation line distance with optical axis at 0.5 ��/NA_iWithin, two-dimension photoelectric sensor 5 records edge of a knife diffraction pattern I on inspection surface under other three directions_i(u, v), wherein i=2,3,4; Repeat step 3., obtain the edge of a knife function B under other three directions_i(x, y), wherein i=2,3,4;

5. following iterative process is performed:

By the grading function P guessed_g(x, y) with edge of a knife function B_i(x, product y) obtains the outgoing light field of conjecture:

Wherein the grading function of initial guess is P₀(x, y), B₀(x, y) �� 1;

Outgoing light field to conjectureDo fresnel diffraction conversion and obtain the diffractive light field of conjecture:

Wherein FST{ } represent fresnel diffraction conversion;

By I_i(u, v) the diffractive light field �� to conjecture_g,i(u, v) carries out the diffractive light field that amplitude constraint obtains updating:

${\mathrm{\ψ}}_{c,i}(u,v)=\sqrt{I_i(u,v)}\frac{{\mathrm{\ψ}}_{g,i}(u,v)}{\left|{\mathrm{\ψ}}_{g,i}(u,v)\right|},i=0,1,2,4$

To the diffractive light field �� updated_c,i(u, v) makes the outgoing light field that fresnel diffraction inverse transformation obtains updating:

Wherein FST^-1{ } represents fresnel diffraction inverse transformation;

By the outgoing light field updatedUpdate grading function:

Above-mentioned iterative process reaches abundant hour to terminate with the error sum of squares SSE between diffractive light field and the diffractive light field of conjecture of renewal, and SSE expression formula is as follows:

$SSE=\frac{\underset{u,v}{\Σ}{\left(\right|{\mathrm{\ψ}}_c(u,v)|-|{\mathrm{\ψ}}_g(u,v)\left|\right)}^2}{MN}$

Wherein MN is sampling number total in exit wave function matrix;

6. the grading function P 5. recovered by step_c(x, y) cast to the pupil plane of projection objective 2 to be measured through light field adverse transference and remove a quadratic phase factor being equivalent to perfect lens and obtain the pupil function of projection objective 2 to be measured, extract the phase place of pupil function, the wave aberration of projection objective 2 to be measured can be obtained.

The wave aberration of examining system is treated in the present embodiment detection, it is possible to simplied system structure, reduces the times of collection of inspection surface pattern, improves detection speed and the precision of system.

Claims (3)

1. one kind utilizes the edge of a knife as the wave aberration detection system of detection labelling, it is characterized in that, including coherent point light sources (1), it is the edge of a knife figure (3) as detection labelling, detection labelling adjustment displacement platform (4) fixing this edge of a knife figure (3) and two-dimension photoelectric sensor (5) successively along this coherent point light sources (1) direction of beam propagation, projection objective to be measured (2) is placed between described coherent point light sources (1) and described edge of a knife figure (3), described coherent point light sources (1) is positioned on the object plane of described projection objective to be measured (2), described edge of a knife figure (3) is fixed on described detection labelling and regulates on displacement platform (4), and it is placed in the image planes of described projection objective to be measured (2) by detecting labelling adjustment displacement platform (4), described two-dimension photoelectric sensor (5) is positioned on the inspection surface after projection objective to be measured (2) image planes, distance between inspection surface and image planes makes on inspection surface the diameter of effective light spot less than the diameter of two-dimension photoelectric sensor (5) photosurface,

The output numerical aperture of described coherent point light sources (1) is more than the object-side numerical aperture of described projection objective to be measured (2);

The two-value figure that described edge of a knife figure (3) is made up of lightproof part and light transmission part, this two-value figure contains n bar edge of a knife demarcation line, n >=3, and the marginal length of the edge of a knife is more than the diameter of projection objective to be measured (2) image planes hot spot; It is XYZ three-shaft displacement platform that described detection labelling regulates displacement platform (4), edge of a knife figure (3) is fixed in the image planes of projection objective to be measured (2) by it, and make edge of a knife figure (3) wherein edge of a knife demarcation line cut the image planes hot spot of projection objective to be measured (2), and make this edge of a knife demarcation line distance with optical axis at 0.5 ��/NA_iWithin, wherein NA_iIt it is the image-side numerical aperture of projection objective to be measured (2).

2. according to claim 1 utilize the edge of a knife as detection labelling wave aberration detection system, it is characterised in that described two-dimension photoelectric sensor (5) is CCD, CMOS or 2 D photoelectric detector array.

3. utilize the method that the wave aberration detection system described in claim 1 or 2 carries out wave aberration detection, it is characterised in that the method comprises the steps of

1. the output numerical aperture coherent point light sources (1) more than the object-side numerical aperture of projection objective to be measured (2) is selected, this coherent point light sources (1) is placed on the object plane of projection objective to be measured (2), the coherent light that coherent point light sources (1) sends is made to image in the image planes of projection objective to be measured (2) after entering projection objective to be measured (2), two-dimension photoelectric sensor (5) is placed on the inspection surface after projection objective to be measured (2) image planes, distance between these inspection surface and image planes can make on inspection surface the diameter of effective light spot less than the diameter of two-dimension photoelectric sensor (5) photosurface, diffraction pattern I on inspection surface when described two-dimension photoelectric sensor (5) record is without the edge of a knife₀(u, v), wherein u, v are system coordinate on inspection surface;

2. edge of a knife figure (3) is fixed on detection labelling and regulates on displacement platform (4), adjust described detection labelling along optical axis direction and regulate the position of displacement platform (4), edge of a knife figure (3) is made to be positioned in the image planes of described projection objective to be measured (2), in the plane of vertical optical axis, adjust detection labelling regulate the position of displacement platform (4), make the image planes hot spot of edge of a knife figure (3) wherein edge of a knife demarcation line cutting projection objective to be measured (2), and the distance of edge of a knife demarcation line and optical axis is at 0.5 ��/NA_iWithin, two-dimension photoelectric sensor (5) records the diffraction pattern I on now inspection surface₁(u, v);

3. optimize following object function, obtain the edge of a knife demarcation line function a under current direction₁x+b₁Two parameter a of y=1₁,b₁:

Wherein P₀(x, y) for system optical field distribution in projection objective to be measured (2) image planes in aberrationless situation,For P₀(x, conjugation y), B₁(x, y) for the edge of a knife function under current direction, it is by edge of a knife demarcation line function a₁x+b₁The two-valued function that y=1 determines:

X, y are system coordinate in projection objective image planes to be measured;

4. in the plane of vertical optical axis, adjust detection labelling regulate the position of displacement platform (4), the image planes hot spot of projection objective to be measured (2) is cut in other n-1 bar edge of a knife demarcation line making edge of a knife figure (3) successively, and makes the edge of a knife demarcation line distance with optical axis at 0.5 ��/NA_iWithin, two-dimension photoelectric sensor (5) records edge of a knife diffraction pattern I on inspection surface under other n-1 direction_i(u, v), wherein i=2 ..., n; Repeat step 3., obtain the edge of a knife function B under other n-1 direction_i(x, y), wherein i=2 ..., n;The selection principle of n is: making the overlapping rate of adjacent edge of a knife function light transmission part on the one hand more than 30%, making all edge of a knife functions logic sum in each position on the other hand is 1, i.e. B₁(x,y)��B₂(x,y)�š���B_n(x, y) �� 1, wherein �� represents logic add;

5. following iterative process is performed:

By the grading function P guessed_g(x, y) with edge of a knife function B_i(x, product y) obtains the outgoing light field of conjecture:

Wherein the grading function of initial guess is system optical field distribution P in projection objective to be measured (2) image planes in aberrationless situation₀(x, y), B₀(x, y) �� 1;

Outgoing light field to conjectureDo fresnel diffraction conversion and obtain the diffractive light field of conjecture:

Wherein FST{ } represent fresnel diffraction conversion;

By I_i(u, v) the diffractive light field �� to conjecture_g,i(u, v) carries out the diffractive light field that amplitude constraint obtains updating:

To the diffractive light field �� updated_c,i(u, v) makes the outgoing light field that fresnel diffraction inverse transformation obtains updating:

Wherein FST^-1{ } represents fresnel diffraction inverse transformation;

Update grading function:

Above-mentioned iterative process reaches abundant hour to terminate with the error sum of squares SSE between diffractive light field and the diffractive light field of conjecture of renewal, and SSE expression formula is as follows:

Wherein MN is sampling number total in exit wave function matrix;

6. the grading function P 5. finally given by step_c(x, y) cast to the pupil plane of projection objective to be measured (2) through light field adverse transference and remove a quadratic phase factor being equivalent to perfect lens and obtain the pupil function of projection objective to be measured (2), extract the phase place of pupil function, the wave aberration of projection objective to be measured (2) can be obtained.