CN104111592A - Method for realizing variable free lighting pupil based on micro-reflector array - Google Patents

Abstract

The invention provides a method for realizing a variable free lighting pupil based on a micro-reflector array. The method comprises the steps of measuring a light spot position, optimizing the light spot position, correcting the light spot position and the like, and specifically comprises the steps of measuring a position parameter of a reflected light spot through a CCD (charge coupled device) camera when each micro-reflector unit is static; substituting the parameters into a grid search ant colony algorithm for optimization to obtain a micro-reflector array rotation angle matrix for generating the shape of the required pupil; measuring a light spot position difference between the light intensity distribution and the required light intensity distribution on a target surface loaded with the rotation angle matrix, and correcting a micro-reflector array rotation angle obtained by optimization by taking the light spot position difference as a feedback to enable a result to finally meet a lighting requirement on the target surface. The method can realize various lighting modes including the non-circumferential symmetric complicated lighting pupil, is high in optimization speed, high in convergence and high in accuracy, and has high practicability.

Description

A kind of method that realizes variable free illumination iris based on micro reflector array

Technical field

The invention belongs to micro-lithography field, relate to the implementation method of free illumination iris in a kind of lithography illuminating system, be specifically related to a kind of method that realizes variable free illumination iris based on micro reflector array.

Background technology

Micro-lithography is manufacturing integration circuit, the technology of liquid crystal display and other micro structural components, in photoetching, two factors that picture quality is played a crucial role are resolution and depth of focus, so should obtain the figure that better resolution forms critical size, keep again suitable depth of focus.Development along with photoetching process, constantly dwindling of lithography node, except reducing the numerical aperture NA of exposure wavelength lambda and projection objective, the shape that changes exposure light source is one of important channel of improving photoetching resolution, on this basis, the off-aixs illumination proposing from the nineties develops into the multistage lighting engineering of recent polarization, and along with further reducing of process factor k1, light source-mask optimisation technique becomes the core of resolution enhance technology of future generation gradually.Utilize light source-mask optimisation technique (Source and Mask Optimization), adopt lighting engineering able to programme (Programmable Illumination) to realize, as traditional lighting, what off-axis illumination was even comparatively complicated freely throws light on, and obtains more suitably illumination iris shape of exit pupil.Free lighting engineering able to programme is compared with off-axis illumination, and the chips wire strip to more complicated, can increase process window, reduces mask dilution of precision MEEF.

In existing technology, in order to obtain instantaneous variable illumination iris shape flexibly, micro reflector array (the MMA of employing based on MEMS, Micro Mirror Array) come illumination iris surface, each micro-reflector is driven by the electrostatic equipment that is similar to Digital Micromirror Device (DMD, Digtal Micro Device), and can tilt to two quadrature sloping shafts, each micro-reflector produces an illumination hot spot on target illumination face, along with the variation of the micro-reflector anglec of rotation.Illumination hot spot can move freely on target illumination face, forms needed perfect light source and distributes.

In the structure shown in international monopoly WO2005/02684, micro-reflective array comprises the micro reflector array of 10000 above plated surface highly reflecting films, the various reflection angle that Quasi-straight light-focusing mirror group between micro-reflector and target illumination face produces catoptron is converted to the diverse location in pupil plane, in said process, core is exactly the anglec of rotation that will calculate each micro-reflector unit, makes the hot spot distribution on target illumination face approach needed perfect light source distribution.In US Patent No. 2010/0265482A1, take and realize ring illumination as example, a kind of position optimization algorithm of definite micro reflector array anglec of rotation has been proposed, first calculate and incide the intensity distribution function on micro reflector array, and obtain its complementary distribution function, make the flare of micro-reflector to the rule variation of complementary distribution function, unevenness with compensation incident beam each several part light intensity, realizes Uniform Illumination.

But it is simple that this method is only applicable to produce, evenly the off-axis illumination of light distribution, no longer applicable for generation light intensity and the complicated free illumination iris changing of shape while.Simultaneously, impact due to the various aberrations of illuminator able to programme and optical element bias in actual use procedure, the actual hot spot obtaining is distributed with certain difference with optimizing the desirable hot spot drawing, these differences can affect the homogeneity of hot spot on output pupil plane and the score quality on CD.

Summary of the invention

The object of the invention is to overcome the deficiencies in the prior art, a kind of method that realizes variable free illumination iris based on micro reflector array is provided, the method can be applied in the occasion that produces complicated on-circular symmetric illumination pupil, further compensated facula position difference, pupil distribution reconstruction accuracy is high.

The technical solution used in the present invention is: a kind of method that realizes the free illumination iris of continuous variable based on micro reflector array, described method comprises the steps:

Step (1), with CCD camera, measure each micro-reflector unit location parameter of flare on illumination target face when static;

Step (2), the location parameter that step (1) is measured to gained flare are brought in grid search ant group algorithm, and optimization produces the micro reflector array anglec of rotation matrix of required light distribution;

Step (3), the anglec of rotation matrix that utilizes step (2) to obtain, generate the control signal of each micro-reflector driver and control micro-reflector and carry out angle rotation, measure now light distribution on illumination target face, using the facula position difference of itself and required light distribution as evaluation index, system is carried out to FEEDBACK CONTROL, until facula position difference meets design requirement.

Further, the method is applicable to utilize micro reflector array to realize the system of any illumination profile, wherein each micro-reflector unit can two-dimentional continuous rotation, and micro reflector array is imaged onto on target illumination face by a collimation condenser group, and micro reflector array position becomes Fourier's relation with target illumination face.

Further, by closed loop feedback system, micro reflector array is demarcated carrying out before flare position measurement, made each mirror unit of micro reflector array in above-mentioned steps (1), (2), all can normally work in (3) three processes.

Further, in described step (1), each micro-reflector unit is when static state, and the detailed process of measuring its flare location parameter on illumination target face with CCD camera is as follows:

If micro reflector array unit adds up to M, provide anglec of rotation matrix α of micro reflector array, in this anglec of rotation matrix, remove micro-reflector to be measured unit M _k(k is mirror unit subscript sequence number, and k=1,2, ..., anglec of rotation M) is outside 0, controls other mirror units take array center as boundary line by control module, comprise that mirror unit more than boundary line upward deflects γ angle, following mirror unit deflects down γ angle, and α is:

The maximum anglec of rotation that wherein γ is each mirror unit, on target illumination face, form one long be the white space of H, and:

H＝2×f _collimator×tan(2γ) (1-2)

Wherein, f _collimatorfocal length for collimation condenser group.

The center position that CCD camera is placed on to target illumination face is accepted the outgoing hot spot of Quasi-straight light-focusing mirror group, light spot image on computer acquisition CCD camera also carries out data processing to it, each micro-reflector unit is repeated to above step, until obtain the centroid position measured value matrix D of each micro-reflector unit corresponding flare when static state ⁰(k).

Further, mirror unit deflection angle more than micro reflector array center also can be got the value that other are less than γ, and the mirror unit deflection angle below center also can be got the value of other be greater than-γ, makes to only have flare to be measured on effective receiving plane of CCD.

Further, in step (2), the step of grid search ant group algorithm is:

Step S11: divide Searching Resolution Space region;

Using each micro-reflector unit Two Dimensional Rotating angle as solution space set, by illumination target face grid division, according to the target light intensity distribution situation of required generation, determine the two-dimentional initial rotation angle degree θ of each micro-reflector unit ¹(k)=(θ _x ¹(k), θ _y ¹(k) scope) is as follows:

0＜|θ _x ¹(k)|＜θ _upper

0＜|θ _y ¹(k)|＜θ _upper (1-3)

Wherein, θ _x ¹(k), θ _y ¹(k) be respectively micro-reflector unit along x direction of principal axis and the axial initial rotation angle degree of y, δ _cfor producing the maximum external coherence system factor under required target illumination pattern, Φ _objarea for illumination target face;

By each θ _x ¹(k), θ _y ¹(k) be divided into N decile, if the sequence number in certain corresponding solution space in micro-reflector unit is (p, q), when algorithm starts, each micro-reflector finite element rotation angle random is dispersed in solution space etc. somewhere, subregion, obtain initial rotation angle degree as follows:

${{\mathrm{\θ}}_x}^1\left(k\right)=0+\frac{{\mathrm{\θ}}_{\mathrm{upper}}}{N}\×(p+\mathrm{rand})$

${{\mathrm{\θ}}_y}^1\left(k\right)=0+\frac{{\mathrm{\θ}}_{\mathrm{upper}}}{N}\×(q+\mathrm{rand}),(p,q=\mathrm{1,2},...,N)---(1-4)$

Wherein, rand is the random number between [0,1];

Step S12: initialization population and individual information element distribute;

Iteration is initial, sets ant and adds up to M, and in optimization, maximum cycle is NC _maxinformation degree volatilization parameter is ρ (0 < ρ < 1), convergence precision is ε (0 < ε < 1), makes objective function G equal the difference of the light distribution of target illumination region and the target light distribution of intending producing after the loaded and optimized gained anglec of rotation of micro reflector array matrix.The position measurement matrix of each flare of gained in step (1) when correction iteration is initial, each ant k in the position of target illumination face is:

${D_x}^1\left(k\right)=f_{\mathrm{collimator}}\&times;\tan \left(2{{\mathrm{\&theta;}}_x}^1\left(k\right)\right)+D_x^0\left(k\right)$

${D_y}^1\left(k\right)=f_{\mathrm{collimator}}\&times;\tan \left(2{{\mathrm{\&theta;}}_y}^1\left(k\right)\right)+D_y^0\left(k\right)---(1-5)$

The evaluation function of definition ant k is the objective function G that on its residing target illumination face, u is ordered _uwith the objective function G that in its field, ant l v of living in is ordered _vand, that is:

ΔG _uv＝G _u+G _v (1-6)

By position u point, to position v point mobile status transition probability formula, be:

${P_{\mathrm{uv}}}^k=\frac{{\mathrm{\&tau;}}_{\mathrm{uv}}/d_{\mathrm{uv}}}{\underset{v\&Element;{\mathrm{allowed}}_k}{\mathrm{\&Sigma;}}{\mathrm{\&tau;}}_{\mathrm{uv}}/d_{\mathrm{uv}}},u\&NotEqual;v---(1-7)$

Wherein, d _uvfor the distance between u point in target face and v point, τ _uvfor the pheromones intensity of ant k on mobile route, allowed _knext step space networks lattice point set of paths allowing away for ant k, the initial information element concentration that every ant k position u is ordered is:

τ _u ⁰＝e ^-G(u) (1-8)

Step S13: elitist ants and general ant are determined in grouping;

Load after the micro reflector array initial rotation angle degree matrix as shown in (1-4) formula, select satisfied | the elitist ants of G|≤ε also adds its present position on target illumination face in taboo list to, press mobile each ant of formula (1-7), adopt unidirectional search mechanism that ant is moved to the little position of objective function from the large position of objective function, when once circulation finishes, the pheromones intensity on ant k institute mobile route is pressed following formula and is upgraded:

${{\mathrm{\&tau;}}_{\mathrm{uv}}}^{\mathrm{new}}=\mathrm{\&rho;}\&times;{\mathrm{\&tau;}}_{\mathrm{uv}}^{\mathrm{old}}+e^{-G_{\mathrm{uv}}}---(1-9)$

Pheromones strength range possible on each optimizing path is limited in to [τ _min, τ _max]:

${{\mathrm{\&tau;}}_{\mathrm{uv}}}^{\mathrm{new}}=\left\{\begin{array}{c}{\mathrm{\&tau;}}_{\min },{{\mathrm{\&tau;}}_{\mathrm{uv}}}^{\mathrm{new}}\&le;{\mathrm{\&tau;}}_{\min }\\ {{\mathrm{\&tau;}}_{\mathrm{uv}}}^{\mathrm{new}},{\mathrm{\&tau;}}_{\min }\&le;{{\mathrm{\&tau;}}_{\mathrm{uv}}}^{\mathrm{new}}\&le;{\mathrm{\&tau;}}_{\max }\\ {\mathrm{\&tau;}}_{\max },{{\mathrm{\&tau;}}_{\mathrm{uv}}}^{\mathrm{new}}\&GreaterEqual;{\mathrm{\&tau;}}_{\max }\end{array}\right.---(1-10)$

Step S14:NC>NC _max, continue to optimize, otherwise go to step S15.Every, take turns after iteration finishes, upgrade ant group's target function value G and taboo list, if the target function value of every ant is less than the convergence precision value ε of definition, goes to step S15, otherwise go to step S13, start next round iterative search;

Step S15: stop optimizing the two-dimensional position matrix D according to current ant k on target illumination face ^optimal(k) calculate best displacement matrix h ^optimaland corresponding Two Dimensional Rotating angle matrix θ (k) ^optimal(k).Wherein,

$\begin{array}{cc}{h_x}^{\mathrm{optimal}}\left(k\right)=D_x^{\mathrm{optimal}}\left(k\right)-D_x^1\left(k\right)& {{\mathrm{\&theta;}}_x}^{\mathrm{optimal}}\left(k\right)=\frac{1}{2}\arctan \left(\frac{{h_x}^{\mathrm{optimal}}\left(k\right)}{f_{\mathrm{collimator}}}\right)\end{array}$

$\begin{array}{cc}{h_y}^{\mathrm{optimal}}\left(k\right)=D_y^{\mathrm{optimal}}\left(k\right)-D_y^1\left(k\right)& {{\mathrm{\&theta;}}_y}^{\mathrm{optimal}}\left(k\right)=\frac{1}{2}\arctan \left(\frac{{h_y}^{\mathrm{optimal}}\left(k\right)}{f_{\mathrm{collimator}}}\right)\end{array}---(1-11)$

Further, anglec of rotation matrix θ after the optimization of the middle correction of step (3) grid search ant group algorithm ^optimal(k) step is:

Step S21: provide anglec of rotation matrix β of micro reflector array, remove tested micro-reflector M in this angle matrix _ktwo Dimensional Rotating angle be θ ^optimal(k) outside, other mirror units are controlled by control module, take array center position as boundary line, and the mirror unit comprising more than boundary line upward deflects γ angle, and following mirror unit deflects down γ angle, and matrix β is:

Step S22: CCD camera is placed on to D on target illumination face ^optiaml(k) position, measures each micro-reflector M _kthe physical location of flare barycenter, calculates precalculated position D on itself and target illumination ^optimal(k) the position difference d locating _diff, select d _diffbe greater than the catoptron set M to be corrected that target illumination region allows maximum facula deviation amount Δ L _s(s<k, and M _s∈ M _k), in these catoptrons, its anglec of rotation θ is got to n point (n>=20) from 0～γ, measure respectively micro-reflector unit M _sfacula position parameter at this n some place, is designated as P ' (θ, s), uses nonlinear function f _s(θ) it is carried out to data fitting, is expressed as:

$f_s\left(\mathrm{\&theta;}\right)=\underset{j=0}{\overset{n}{\mathrm{\&Sigma;}}}{a}_j{f}_j\left(\mathrm{\&theta;}\right)$

|f _s(θ)-P′(θ,s)|≤δ ₁ (1-13)

Wherein, a _jfor the coefficient of polynomial fitting, δ ₁for data fitting low precision, from formula (1-13), obtain S function expression, the flare M to be corrected that the optimization of grid ant group algorithm is drawn _sposition D ^optiaml(s) substitution f _s(θ) in expression formula, that is:

$D^{\mathrm{optimal}}\left(s\right)=\underset{j=0}{\overset{n}{\mathrm{\&Sigma;}}}{a}_j{f}_j\left(\mathrm{\&theta;}\right)---(1-14)$

From above formula, solve θ (s), replaced θ ^optimal(k) value at same position place in.

Step S23: repeating step S22, until being all less than target illumination region, the position difference of each mirror unit flare allows maximum facula deviation amount, export the last micro-reflector Two Dimensional Rotating angle matrix θ that actual optical system requires that meets ^finnal(k).

Beneficial effect of the present invention is:

The present invention compares with previous free illumination iris implementation method, has improved the practicality of optimization method, and itself and light source mask optimizing process are better combined, and improves the resolution of etching system, is specifically:

(1) location parameter of flare when the present invention adopts each micro-reflector unit of CCD cameras record static, has guaranteed to input in subsequent algorithm the accuracy of data;

(2) the present invention utilizes grid search ant group algorithm to obtain micro reflector array anglec of rotation matrix, and algorithm speed is fast, and convergence is good, can produce and comprise traditional lighting, off-axis illumination and the light illumination mode such as multiple that freely throws light on;

(3) anglec of rotation that the present invention proposes algorithm optimization to draw compensates, and adopts first screening, and the mode of rear measurement, has simplified measuring process, proofreaies and correct the position of flare, has reduced the difference with desirable emergent pupil.

Accompanying drawing explanation:

With reference to the detailed description to embodiment below in conjunction with accompanying drawing, various feature and advantage of the present invention can be easier to understand, wherein:

Fig. 1 is that application the present invention is based on the method flow diagram that micro reflector array is realized variable free illumination iris;

Fig. 2 is free lamp optical system schematic diagram able to programme in the applicable photolithographic exposure system of the present invention; Wherein, excimer laser 1, single micro-compound eye array 2, micro reflector array mirror unit 31, micro reflector array substrate 32, turnover catoptron 4, Quasi-straight light-focusing mirror group 5, CCD camera 6, computing machine 7 and control module 8;

Fig. 3 is each micro-reflector unit flare schematic diagram on illumination target face under the CCD collected by camera static state the present invention relates to; 6 is CCD camera, and B represents flare region, and O is illumination target Mian center, and H is the length of the formed white space of flare;

Fig. 4 is the process flow diagram based on grid search ant colony optimization algorithm of the present invention;

Fig. 5 is micro reflector array flare position correction front and back schematic diagram on target illumination region, the flare that the micro reflector array of take is listed in target face at the center one of Y-direction is example, and Fig. 5 (a) is the position difference curve of light distribution before proofreading and correct and desirable light distribution; Fig. 5 (b) is the position difference curve of light distribution after proofreading and correct and desirable light distribution;

Fig. 6 is the free light illumination mode pupil simulate effect figure realizing according to the present embodiment; Fig. 6 (a), 6 (b) are that realized free illumination iris distributes; Fig. 6 (c), 6 (d) are realized freely throwing light on and the RMS difference curve of intending the desirable illumination intensity distribution of generation.

Embodiment

For making object of the present invention, technical scheme and advantage are clearer, and below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in more detail.

Embodiment 1:

Fig. 1 is the method flow diagram of realizing the free illumination iris of continuous variable based on micro reflector array of the present invention, comprises facula position measurement, facula position optimization, and facula position is proofreaied and correct three processes, and concrete steps are as follows:

Step (1), with CCD camera, measure each micro-reflector unit location parameter of flare on illumination target face when static;

Step (2), the location parameter that step (1) is measured to gained flare are brought in grid search ant group algorithm, and optimization produces the micro reflector array anglec of rotation matrix of required light distribution;

Step (3), the anglec of rotation matrix that utilizes step (2) to obtain, the control signal that generates each micro-reflector is controlled it and is carried out angle rotation, measure now light distribution on illumination target face, using the facula position difference of itself and required light distribution as evaluation index, system is carried out to FEEDBACK CONTROL, until facula position difference meets design requirement, trimming process finishes.

As shown in Figure 2, the optical system that is applicable to this free illumination iris implementation method is by excimer laser 1, single micro-compound eye array 2, and micro reflector array 3, turnover catoptron 4, Quasi-straight light-focusing mirror group 5, CCD camera 6, computing machine 7 and control module 8 form.Wherein, before excimer laser 1 is positioned at single micro-compound eye array 2, turnover catoptron 4 is between micro reflector array 3 and Quasi-straight light-focusing mirror group 5, CCD camera 6 is positioned at the center of illumination target face, and be connected with computing machine 7, control module 8, micro reflector array 3 is connected with control module 8, and CCD camera 6 is fixed on an accurate translation stage and moves thereupon.The Gaussian beam that excimer laser 1 sends is incident on single micro-compound eye array 2, single micro-compound eye array 2 segments incident beam focus on micro reflector array 3, micro reflector array 3 is positioned on the front focal plane of Quasi-straight light-focusing mirror group 5, it comprises single micro-reflector unit 31 and substrate 32, light beam after reflection shines in Quasi-straight light-focusing mirror group 5 after catoptron 4 by turnover, and is focused on the CCD camera 6 that is positioned at its position of focal plane by it.In the present embodiment, the number of micro reflector array is 10000, and the maximum Two Dimensional Rotating angle of each mirror unit is 5 °.

Before measurement starts in step (1), whole micro-reflectors unit is corrected by closed loop feedback system, made it in step (1), (2), all can normally work in (3) three processes.When switching on power, once reset first to micro reflector array, make each little micro-reflector unit 31 parallel with substrate 32, define now micro reflector array 3 and be operated in static state, the process that CCD camera 6 gathers the flare of single micro-reflector unit 31 under its static state is as follows:

Be located in micro reflector array 3, micro-reflector unit adds up to M, and the maximum Two Dimensional Rotating angle of each mirror unit is γ, with tested micro-reflector M _k(k is mirror unit subscript sequence number, and k=1,2 ..., M) be example, provide 3 one anglec of rotation matrix α of micro reflector array, make in this anglec of rotation matrix except tested micro-reflector M _kthe anglec of rotation is outside 0, and other mirror units are controlled by control module 8, take array center position as boundary line, and the mirror unit comprising more than boundary line upward deflects γ angle, and following mirror unit deflects down γ angle, that is:

Along with the rotation of mirror unit, as shown in Figure 3, flare on target illumination face form one long be the white space of H, in this region, only have mirror unit M to be measured _kflare, when optical aberration and other alignment errors hour, have:

H＝2×f _collimator×tan(2γ) (1-2)

Wherein, f _collimatorfor the focal length of collimation condenser group 5, the displacement H of hot spot becomes approximate Fourier transform relation with the anglec of rotation γ of micro-reflector unit.CCD camera 6, in the present embodiment its effective feeling light area are placed in center at illumination target face the position that regulates CCD camera 6 with accurate translation stage, makes the center of its effective feeling light area and the center superposition of target illumination face, and computing machine 7 gathers the light spot image on CCD camera 6 and it is carried out to data processing, obtains tested micro-reflector M _kthe centroid position of corresponding flare in target face.Each micro-reflector unit is repeated to above step, until obtain the centroid position measured value matrix D of each micro-reflector unit corresponding flare when static state ⁰(k).

Fig. 4 is the process flow diagram of grid search ant group algorithm of the present invention, and wherein, the step of described grid search ant group algorithm is as follows:

Step S11: divide Searching Resolution Space region.By target illumination face grid division, on the net point in space corresponding to a residing state of ant, if every ant in ant group algorithm is corresponding to each flare of micro-reflector unit on target illumination face, along with mirror unit Two Dimensional Rotating, ant is moved between each space networks lattice point, according to the target function value of each net point, leave different information concentration, the moving direction of ant when affecting next iteration.In this process, every corresponding unknown variable of ant k is micro-reflector unit M _ktwo Dimensional Rotating angle, each solution all contains in x direction, two variablees of the anglec of rotation in y direction, according to the light distribution situation of required light illumination mode in target face, determine that the initial rotation angle degree scope of micro reflector array is as follows:

0＜|θ _x ¹(k)|＜θ _upper

0＜|θ _y ¹(k)|＜θ _upper

${\mathrm{\&theta;}}_{\mathrm{upper}}=\frac{1}{2}\arctan \left(\frac{{\mathrm{\&delta;}}_c{\mathrm{\&Phi;}}_{\mathrm{obj}}}{2f_{\mathrm{collimator}}}\right)---(1-3)$

Wherein, θ _x ¹(k), θ _y ¹(k) the initial rotation angle degree that is respectively micro-reflector unit in x direction and in y direction, δ _outerfor intending the maximum external coherence system factor of the target illumination pattern of generation, Φ _objarea for target face illuminated area.

By each θ _x ¹(k), θ _y ¹(k) be divided into N decile, solution space has 2N node, and the sequence number of establishing in certain corresponding solution space in micro-reflector unit is (p, q), when algorithm starts, each micro-reflector finite element rotation angle random is dispersed in solution space etc. somewhere, subregion, obtain the anglec of rotation as follows:

${{\mathrm{\&theta;}}_x}^1\left(k\right)=0+\frac{{\mathrm{\&theta;}}_{\mathrm{upper}}}{N}\&times;(p+\mathrm{rand})$

${{\mathrm{\&theta;}}_y}^1\left(k\right)=0+\frac{{\mathrm{\&theta;}}_{\mathrm{upper}}}{N}\&times;(q+\mathrm{rand}),(p,q=\mathrm{1,2},...,N)---(1-4)$

Wherein, rand is the random number between [0,1].

Step S12: initialization population and individual information element distribute.Iteration is initial, sets ant and adds up to M, and in optimization, maximum cycle is NC _max, information degree volatilization parameter ρ (0 < ρ < 1).If each ant k loads after the initial rotation angle degree as shown in step S11, consider the position measurements matrix D that has measured each micro-reflector unit corresponding flare when the static state with CCD camera 6 ⁰(k), wherein when iteration is initial, the position correction of each ant k on target illumination face is:

${D_x}^1\left(k\right)=f_{\mathrm{collimator}}\&times;\tan \left(2{{\mathrm{\&theta;}}_x}^1\left(k\right)\right)+D_x^0\left(k\right)$

${D_y}^1\left(k\right)=f_{\mathrm{collimator}}\&times;\tan \left(2{{\mathrm{\&theta;}}_y}^1\left(k\right)\right)+D_y^0\left(k\right)---(1-5)$

Make objective function G equal the difference of the light distribution in target face and the target light distribution of intending producing after the loaded and optimized gained anglec of rotation of micro reflector array matrix, and work as | during G|≤ε (ε is algorithm convergence accuracy value, and 0 < ε < 1), optimize and stop.The evaluation function value of definition ant k is the objective function G that on its residing target illumination face, u is ordered _uwith the objective function G that in its field, ant l v of living in is ordered _vand, that is:

ΔG _uv＝G _u+G _v (1-6)

In the process in the loaded and optimized anglec of rotation obtaining of micro reflector array, the anglec of rotation is larger, in target face, mobile spot distance is larger, the error of the facula position producing is larger, therefore the search direction of setting ant not only with its mobile route (u, v) the pheromone concentration evaluation function on is relevant, distance dependent also and between ant, ant is selected the path optimizing nearest with it as far as possible, to reduce micro-reflector unit flare deviation in moving process when carrying out two dimension angular rotation.Make k ant adopt the mode of roulette mobile to position v point by position u point according to state transition probability formula below:

${P_{\mathrm{uv}}}^k=\frac{{\mathrm{\&tau;}}_{\mathrm{uv}}/d_{\mathrm{uv}}}{\underset{v\&Element;{\mathrm{allowed}}_k}{\mathrm{\&Sigma;}}{\mathrm{\&tau;}}_{\mathrm{uv}}/d_{\mathrm{uv}}},u\&NotEqual;v---(1-7)$

Wherein, d _uvfor the distance between u point in position in target face and position v point, τ _uvfor the pheromones intensity of ant k on mobile route, allowed _knext step space networks lattice point set of paths allowing away for ant k, wherein, the initial information element concentration that every ant k position u is ordered can determine according to objective function, that is:

τ _u ⁰＝e ^-G(u) (1-8)

Step S13: ant packet, determine elitist ants and general ant: select satisfied | the elitist ants of G|≤ε and by its current on target illumination face present position add in taboo list, by the described optimizing probability of formula (1-7), move each ant, and adopt unidirectional search machine-processed, ant is moved to the little position of objective function from the large position of objective function, guarantee that a plurality of targets reach its optimal value.When once circulation finishes, the pheromones intensity on ant k institute mobile route is pressed following formula and is upgraded:

${{\mathrm{\&tau;}}_{\mathrm{uv}}}^{\mathrm{new}}=\mathrm{\&rho;}\&times;{\mathrm{\&tau;}}_{\mathrm{uv}}^{\mathrm{old}}+e^{-G_{\mathrm{uv}}}---(1-9)$

The stagnation and the diffusion problem that due to ant group algorithm, in optimizing process, are prone to are not easy to ignore, and for fear of algorithm Premature Convergence in non-globally optimal solution, pheromones strength range possible on each optimizing path are limited in to [τ _min, τ _max] in, wherein, τ _mincan effectively avoid algorithm to stagnate, τ _maxcan avoid pheromone concentration on certain paths much larger than other paths, further, for fear of a plurality of ants are all focused on same path, limit algorithm diffusion, each circulation finishes rear reservation optimal path, in a circulation, only has the ant of shortest path just to have weight update τ _uv ^new, on the basis of above-mentioned (1-9) formula, add following formula and carry out threshold decision selection, that is:

${{\mathrm{\&tau;}}_{\mathrm{uv}}}^{\mathrm{new}}=\left\{\begin{array}{c}{\mathrm{\&tau;}}_{\min },{{\mathrm{\&tau;}}_{\mathrm{uv}}}^{\mathrm{new}}\&le;{\mathrm{\&tau;}}_{\min }\\ {{\mathrm{\&tau;}}_{\mathrm{uv}}}^{\mathrm{new}},{\mathrm{\&tau;}}_{\min }\&le;{{\mathrm{\&tau;}}_{\mathrm{uv}}}^{\mathrm{new}}\&le;{\mathrm{\&tau;}}_{\max }\\ {\mathrm{\&tau;}}_{\max },{{\mathrm{\&tau;}}_{\mathrm{uv}}}^{\mathrm{new}}\&GreaterEqual;{\mathrm{\&tau;}}_{\max }\end{array}\right.---(1-10)$

Step S14: if cycle index NC>NC _max, continue to optimize, otherwise go to step S15.Every, take turns after iteration finishes, recalculate ant group's target function value G, the position of the elitist ants obtaining is added in taboo list, if the target function value of every ant is less than defined convergence precision value ε, go to step S15, otherwise go to step S13, start next round iterative search;

Step S15: stop optimizing, obtain the location matrix D of current each ant k on target illumination face ^optimal(k) (D ^optimal(k)=(D _x ^optimal(k), D _y ^optimal(k))), the initial position two-dimensional matrix D on target illumination face in conjunction with ant k ¹(k), obtain the two-dimensional matrix h with respect to initial position displacement ^optimal(k), be defined as the best shift position matrix after optimizing, and calculated corresponding Two Dimensional Rotating angle matrix θ according to formula (1-11) ^optimal(k), wherein,

$\begin{array}{cc}{h_x}^{\mathrm{optimal}}\left(k\right)=D_x^{\mathrm{optimal}}\left(k\right)-D_x^1\left(k\right)& {{\mathrm{\&theta;}}_x}^{\mathrm{optimal}}\left(k\right)=\frac{1}{2}\arctan \left(\frac{{h_x}^{\mathrm{optimal}}\left(k\right)}{f_{\mathrm{collimator}}}\right)\end{array}$

$\begin{array}{cc}{h_y}^{\mathrm{optimal}}\left(k\right)=D_y^{\mathrm{optimal}}\left(k\right)-D_y^1\left(k\right)& {{\mathrm{\&theta;}}_y}^{\mathrm{optimal}}\left(k\right)=\frac{1}{2}\arctan \left(\frac{{h_y}^{\mathrm{optimal}}\left(k\right)}{f_{\mathrm{collimator}}}\right)\end{array}---(1-11)$

Algorithm finishes.

In the present embodiment, as maximum cycle NC _maxget 2000, convergence precision value ε is 0.05 o'clock, and algorithm is that 1000 left and right reach convergence in cycle index.

In above-mentioned ant colony optimization algorithm solution procedure, do not consider in actual optical system the aberration due to fourier lense group, the position deviation of micro-reflector unit and the change of reflected spot size in Two Dimensional Rotating process thereof, now on target illumination face, the displacement of flare does not meet the relation shown in formula (1-11), affected the positional accuracy of outgoing hot spot, further, producing traditional lighting and off-axis illumination occasion, if require beam uniformity in target face more than 95%, must be proofreaied and correct the hot spot deviation in above-mentioned situation, to optimizing the micro mirror anglec of rotation matrix obtaining, compensated.

But the position of each micro-reflector flare and size all with the position at place, micro-reflector unit, it is the anglec of rotation on two-dimensional directional, the centre deviation of single micro-compound eye array, the factors such as aberration of fourier lense group are relevant, cannot express by concrete analytical function expression formula, in order to reduce computation complexity, the present invention adopts and first filters out the hot spot that does not meet position offset requirement, then the mode of these hot spots being measured to the position of the anglec of rotation of micro-reflector unit and corresponding measurement hot spot thereof and dimensional data by certain algorithm (as least square method, genetic algorithm etc.) data fitting, draw the position of each flare and the functional relation that size changes with anglec of rotation θ.Adopt following step to proofread and correct the gained anglec of rotation after ant colony optimization algorithm:

Step S21: the micro reflector array anglec of rotation obtaining after the optimization of grid ant group algorithm is loaded on each micro-reflector unit one by one, provides anglec of rotation matrix β of micro reflector array, remove tested micro-reflector M in this anglec of rotation matrix _ktwo Dimensional Rotating angle be θ ^optimal(k) outside, other mirror units are controlled by control module 8, take array center position as boundary line, and the mirror unit comprising more than boundary line upward deflects γ angle, and following mirror unit deflects down γ angle, and CCD camera 6 is placed on to target illumination face D ^optimal(k) position is measured, and now only has flare to be measured to be positioned on the receiving plane of CCD camera 6, and wherein, matrix β is:

Step S22: mobile accurate translation stage, is placed on target illumination face D by CCD camera ^optimal(k) hot spot is accepted in position, to each micro-reflector unit, calculates the difference d of pre-position on its physical location of measuring flare barycenter and target illumination by step S21 _diff, select d _diffbe greater than the catoptron set M to be corrected of maximum facula deviation amount Δ L _s(s<k, and M _s∈ M _k), from the micro-reflector anglec of rotation 0～γ, get n point (n>=20), measure respectively M _sin each micro-reflector unit at the flare location parameter at this n some place, be designated as P ' (θ, s), adopt least square method the centroid position data of the flare of surveying under different rotary angle θ to be carried out to the data fitting at discrete point place, used nonlinear function f _s(θ) function representation, wherein:

$f_s\left(\mathrm{\&theta;}\right)=\underset{j=0}{\overset{n}{\mathrm{\&Sigma;}}}{a}_j{f}_j\left(\mathrm{\&theta;}\right)$

|f _s(θ)-P′(θ,s)|≤δ ₁ (1-13)

Wherein, a _jfor each coefficient of polynomial fitting, δ ₁for data fitting error, it is relevant with maximum facula deviation amount Δ L.From formula (1-13), obtain S function expression, the flare M to be corrected that the optimization of grid ant group algorithm is drawn _slocation parameter substitution f _s(θ), in expression formula, obtain:

$D^{\mathrm{optimal}}\left(s\right)=\underset{j=0}{\overset{n}{\mathrm{\&Sigma;}}}{a}_j{f}_j\left(\mathrm{\&theta;}\right)---(1-14)$

From above formula, solve θ (s), replaced θ ^optimal(k) value at same position place in.

Step S23: repeating step S22, until being all less than target illumination region, the position difference of each mirror unit flare allows maximum facula deviation amount Δ L, output finally meets the micro-reflector Two Dimensional Rotating angle matrix θ that actual optical system requires ^finnal(k).

Fig. 5 is schematic diagram before and after micro reflector array flare on target illumination face is proofreaied and correct, in the present embodiment, flare size mean value is 2mm, target illumination region allows maximum facula deviation amount Δ L<0.2mm, with micro reflector array, classify example as in center one in the Y direction, it comprises 100 micro mirror unit, and Fig. 5 (a) is the difference curve of light distribution before proofreading and correct and desirable light distribution; The micro-reflector unit deviation of position of keeping to the side before proofreading and correct is as seen from the figure larger, and the corresponding flare of these position micro-reflectors is screened, and it is proofreaied and correct.Fig. 5 (b) for this reason row mirror unit proofread and correct after the difference curve of light distribution and desirable light distribution.After proofreading and correct as seen from the figure, all hot spot deviate is all less than maximum facula deviation amount.

The embodiment that several illumination iris that Fig. 6 produces for application the present invention distribute, Fig. 6 (a), 6 (b) are respectively the free illumination iris distribution plan of simulating in illumination analysis software Lighttools, Fig. 6 (c), 6 (d) correspond respectively to Fig. 6 (a), and Fig. 6 (b), while quantizing for target illumination face being got to 150 * 150 sampling number, the illumination intensity that directions X is crossed in its center cross-sectional distributes and the difference of intending the desirable light distribution of generation, get its each light intensity difference quantizing in grid and do normalization RMS curve map, as can be seen from the figure, apply the inventive method formed free illumination iris and desirable illumination iris difference less, RMS value is no more than 0.1%.

Foregoing description is only the description to preferred embodiment of the present invention, and not to any restriction of the present invention, any change that the those of ordinary skill in field of the present invention is done according to above-mentioned disclosure, discloses, and all belongs to the scope of claims.

Claims (7)

1. based on micro reflector array, realize a method for variable free illumination iris, it is characterized in that: described method comprises the steps:

Step (1), with CCD camera, measure each micro-reflector unit location parameter of flare on illumination target face when static;

Step (2), the location parameter that step (1) is measured to gained flare are brought in grid search ant group algorithm, and optimization produces the micro reflector array anglec of rotation matrix of required light distribution;

Step (3), the anglec of rotation matrix that utilizes step (2) to obtain, generate the control signal of each micro-reflector driver and control micro-reflector and carry out angle rotation, measure now light distribution on illumination target face, using the facula position difference of itself and required light distribution as evaluation index, system is carried out to FEEDBACK CONTROL, until facula position difference meets design requirement.

2. the method that realizes variable free illumination iris based on micro reflector array according to claim 1, it is characterized in that: the method is applicable to utilize micro reflector array to realize the system of any illumination profile, wherein each micro-reflector unit can two-dimentional continuous rotation, and micro reflector array is imaged onto on target illumination face by a collimation condenser group, and micro reflector array position becomes Fourier's relation with target illumination face.

3. according to claim 1ly based on micro reflector array, realize variable free illumination iris method, it is characterized in that: before flare position measurement, by closed loop feedback system, micro reflector array is demarcated carrying out, make each mirror unit of micro reflector array in above-mentioned steps (1), (2), in (3) three processes, all can normally work.

4. the method that realizes variable free illumination iris based on micro reflector array according to claim 1, it is characterized in that: in described step (1), each micro-reflector unit is when static state, and the detailed process of measuring its flare location parameter on illumination target face with CCD camera is as follows:

If micro reflector array unit adds up to M, provide anglec of rotation matrix α of micro reflector array, in this anglec of rotation matrix, remove micro-reflector to be measured unit M _k(k is mirror unit subscript sequence number, and k=1,2, ..., anglec of rotation M) is outside 0, controls other mirror units take array center as boundary line by control module, the mirror unit comprising more than boundary line upward deflects γ angle, and following mirror unit deflects down γ angle, and α is:

The maximum anglec of rotation that wherein γ is each mirror unit, on target illumination face, form one long be the white space of H, and:

H＝2×f _collimator×tan(2γ) (1-2)

Wherein, f _collimatorfocal length for collimation condenser group;

The center position that CCD camera is placed on to target illumination face is accepted the outgoing hot spot of Quasi-straight light-focusing mirror group, light spot image on computer acquisition CCD camera also carries out data processing to it, each micro-reflector unit is repeated to above step, until obtain the centroid position measured value matrix D of each micro-reflector unit corresponding flare when static state ⁰(k).

5. the method that realizes variable free illumination iris based on micro reflector array according to claim 4, it is characterized in that: mirror unit deflection angle more than described micro reflector array center also can be got the value that other are less than γ, mirror unit deflection angle below center also can be got the value of other be greater than-γ, makes to only have flare to be measured on effective receiving plane of CCD.

6. the method that realizes variable free illumination iris based on micro reflector array according to claim 1, is characterized in that: in described step (2), the step of grid search ant group algorithm is:

Step S11: divide Searching Resolution Space region;

Using each micro-reflector unit Two Dimensional Rotating angle as solution space set, by illumination target face grid division, according to the target light intensity distribution situation of required generation, determine the two-dimentional initial rotation angle degree θ of each micro-reflector unit ¹(k)=(θ _x ¹(k), θ _y ¹(k) scope) is as follows:

0＜|θ _x ¹(k)|＜θ _upper

0＜|θ _y ¹(k)|＜θ _upper (1-3)

Wherein, θ _x ¹(k), θ _y ¹(k) be respectively micro-reflector unit along x direction of principal axis and the axial initial rotation angle degree of y, δ _cfor producing the maximum external coherence system factor under required target illumination pattern, Φ _objarea for illumination target face;

By each θ _x ¹(k), θ _y ¹(k) be divided into N decile, if the sequence number in certain corresponding solution space in micro-reflector unit is (p, q), when algorithm starts, each micro-reflector finite element rotation angle random is dispersed in solution space etc. somewhere, subregion, obtain initial rotation angle degree as follows:

${{\mathrm{\&theta;}}_x}^1\left(k\right)=0+\frac{{\mathrm{\&theta;}}_{\mathrm{upper}}}{N}\&times;(p+\mathrm{rand})$

${{\mathrm{\&theta;}}_y}^1\left(k\right)=0+\frac{{\mathrm{\&theta;}}_{\mathrm{upper}}}{N}\&times;(q+\mathrm{rand}),(p,q=\mathrm{1,2},...,N)---(1-4)$

Wherein, rand is the random number between [0,1];

Step S12: initialization population and individual information element distribute;

Iteration is initial, sets ant and adds up to M, and in optimization, maximum cycle is NC _maxinformation degree volatilization parameter is ρ (0 < ρ < 1), convergence precision is ε (0 < ε < 1), makes objective function G equal the difference of the light distribution of target illumination region and the target light distribution of intending producing after the loaded and optimized gained anglec of rotation of micro reflector array matrix.The position measurement matrix of each flare of gained in step (1) when correction iteration is initial, each ant k in the position of target illumination face is:

${D_x}^1\left(k\right)=f_{\mathrm{collimator}}\&times;\tan \left(2{{\mathrm{\&theta;}}_x}^1\left(k\right)\right)+D_x^0\left(k\right)$

${D_y}^1\left(k\right)=f_{\mathrm{collimator}}\&times;\tan \left(2{{\mathrm{\&theta;}}_y}^1\left(k\right)\right)+D_y^0\left(k\right)---(1-5)$

The evaluation function of definition ant k is the objective function G that on its residing target illumination face, u is ordered _uwith the objective function G that in its field, ant l v of living in is ordered _vand, that is:

ΔG _uv＝G _u+G _v (1-6)

By position u point, to position v point mobile status transition probability formula, be:

${P_{\mathrm{uv}}}^k=\frac{{\mathrm{\&tau;}}_{\mathrm{uv}}/d_{\mathrm{uv}}}{\underset{v\&Element;{\mathrm{allowed}}_k}{\mathrm{\&Sigma;}}{\mathrm{\&tau;}}_{\mathrm{uv}}/d_{\mathrm{uv}}},u\&NotEqual;v---(1-7)$

Wherein, d _uvfor the distance between u point in target face and v point, τ _uvfor the pheromones intensity of ant k on mobile route, allowed _knext step space networks lattice point set of paths allowing away for ant k, the initial information element concentration that every ant k position u is ordered is:

τ _u ⁰＝e ^-G(u) (1-8)

Step S13: elitist ants and general ant are determined in grouping;

Load after the micro reflector array initial rotation angle degree matrix as shown in (1-4) formula, select satisfied | the elitist ants of G|≤ε also adds its present position on target illumination face in taboo list to, press mobile each ant of formula (1-7), adopt unidirectional search mechanism that ant is moved to the little position of objective function from the large position of objective function, when once circulation finishes, the pheromones intensity on ant k institute mobile route is pressed following formula and is upgraded:

${{\mathrm{\&tau;}}_{\mathrm{uv}}}^{\mathrm{new}}=\mathrm{\&rho;}\&times;{\mathrm{\&tau;}}_{\mathrm{uv}}^{\mathrm{old}}+e^{-G_{\mathrm{uv}}}---(1-9)$

Pheromones strength range possible on each optimizing path is limited in to [τ _min, τ _max]:

${{\mathrm{\&tau;}}_{\mathrm{uv}}}^{\mathrm{new}}=\left\{\begin{array}{c}{\mathrm{\&tau;}}_{\min },{{\mathrm{\&tau;}}_{\mathrm{uv}}}^{\mathrm{new}}\&le;{\mathrm{\&tau;}}_{\min }\\ {{\mathrm{\&tau;}}_{\mathrm{uv}}}^{\mathrm{new}},{\mathrm{\&tau;}}_{\min }\&le;{{\mathrm{\&tau;}}_{\mathrm{uv}}}^{\mathrm{new}}\&le;{\mathrm{\&tau;}}_{\max }\\ {\mathrm{\&tau;}}_{\max },{{\mathrm{\&tau;}}_{\mathrm{uv}}}^{\mathrm{new}}\&GreaterEqual;{\mathrm{\&tau;}}_{\max }\end{array}\right.---(1-10)$

Step S14: if NC>NC _max, continue to optimize, otherwise go to step S15.Every, take turns after iteration finishes, upgrade ant group's target function value G and taboo list, if the objective function of every ant is less than the convergence precision value ε of definition, goes to step S15, otherwise go to step S13, start next round iterative search;

Step S15: stop optimizing the two-dimensional position matrix D according to current ant k on target illumination face ^optimal(k) calculate best displacement matrix h ^optimaland corresponding Two Dimensional Rotating angle matrix θ (k) ^optimal(k), wherein,

$\begin{array}{cc}{h_x}^{\mathrm{optimal}}\left(k\right)=D_x^{\mathrm{optimal}}\left(k\right)-D_x^1\left(k\right)& {{\mathrm{\&theta;}}_x}^{\mathrm{optimal}}\left(k\right)=\frac{1}{2}\arctan \left(\frac{{h_x}^{\mathrm{optimal}}\left(k\right)}{f_{\mathrm{collimator}}}\right)\end{array}$

$\begin{array}{cc}{h_y}^{\mathrm{optimal}}\left(k\right)=D_y^{\mathrm{optimal}}\left(k\right)-D_y^1\left(k\right)& {{\mathrm{\&theta;}}_y}^{\mathrm{optimal}}\left(k\right)=\frac{1}{2}\arctan \left(\frac{{h_y}^{\mathrm{optimal}}\left(k\right)}{f_{\mathrm{collimator}}}\right)\end{array}---(1-11)$

7. based on micro reflector array, realize according to claim 1 the method for variable free illumination iris, it is characterized in that: anglec of rotation matrix θ after the optimization of correction grid search ant group algorithm in described step (3) ^optimal(k) step is:

Step S21: provide anglec of rotation matrix β of micro reflector array, remove tested micro-reflector M in this angle matrix _ktwo Dimensional Rotating angle be θ ^optimal(k) outside, other mirror units are controlled by control module, take array center position as boundary line, and the mirror unit comprising more than boundary line upward deflects γ angle, and following mirror unit deflects down γ angle, and matrix β is:

Step S22: CCD camera is placed on to D on target illumination face ^optiaml(k) position, measures each micro-reflector M _kthe physical location of flare barycenter, calculates precalculated position D on itself and target illumination ^optimal(k) the position difference d locating _diff, select d _diffbe greater than the catoptron set M to be corrected that target illumination region allows maximum facula deviation amount Δ L _s(s<k, and M _s∈ M _k), in these catoptrons, its anglec of rotation θ is got to n point (n>=20) from 0～γ, measure respectively micro-reflector unit M _sfacula position parameter at this n some place, is designated as P ' (θ, s), uses nonlinear function f _s(θ) it is carried out to data fitting, is expressed as:

$f_s\left(\mathrm{\&theta;}\right)=\underset{j=0}{\overset{n}{\mathrm{\&Sigma;}}}{a}_j{f}_j\left(\mathrm{\&theta;}\right)$

|f _s(θ)-P′(θ,s)|≤δ ₁ (1-13)

Wherein, a _jfor the coefficient of polynomial fitting, δ ₁for data fitting low precision, from formula (1-13), obtain S function expression, the flare M to be corrected that the optimization of grid ant group algorithm is drawn _sposition D ^optimal(s) substitution f _s(θ) in expression formula, that is:

$D^{\mathrm{optimal}}\left(s\right)=\underset{j=0}{\overset{n}{\mathrm{\&Sigma;}}}{a}_j{f}_j\left(\mathrm{\&theta;}\right)---(1-14)$

From above formula, solve θ (s), replaced θ ^optimal(k) value at same position place in.

Step S23: repeating step S22, until being all less than target illumination region, the position difference of each mirror unit flare allows maximum facula deviation amount, export the last micro-reflector Two Dimensional Rotating angle matrix θ that actual optical system requires that meets ^finnal(k).