CN102540474B - Flat-top light beam shaping control method for achieving abrupt edge and low light-intensity variation and shaping device thereof - Google Patents

Abstract

The invention discloses a shaping control method of a flat-top light beam shaping device for achieving an abrupt edge and low light-intensity variation, and the flat-top light beam shaping control method and the shaping device relate to a flat-top light beam shaping device for achieving the abrupt edge and the low light-intensity variation, and further relate to a shaping control method, so as to solve the problems in the prior art that a position cannot be flexibly set to shape a light beam, the shape and the caliber of the shaped light beam cannot be changed flexibly, the edge is not abrupt, and further, the flat top light-intensity variation of the light beam is large. A lens in the shaping device provided by the invention is positioned between a surface where an optical phase array is positioned and an output surface; the light beam passes through the optical phase array, and then goes through a Fourier transform lens, so that the light beam is shaped; a light field is obtained at the output surface; and an intensity distribution collecting module collects the intensity distribution of the light beam of the shaped light field of the output surface and outputs the intensity distribution of the light beam to a processor module, and judges whether to adjust the phase of the optical phase array or not through calculating an RMSE (root-mean-square error ) value. By using the device provided by the invention, the anticipative shaping of the light beam is achieved by the shaping control method. The flat-top light beam shaping control method and the shaping device are applied to the technical field of diffraction optics and laser shaping.

Description

A kind of reforming control method of realizing the flat top beam apparatus for shaping that edge is precipitous and light-intensity variation is low

Technical field

The invention belongs to diffraction optics and laser shaping technical field, be specifically related to a kind of flat top beam apparatus for shaping that edge is precipitous and light-intensity variation is low of realizing, the invention still further relates to reforming control method.

Background technology

Flat top beam shaping methods and device, in field extensive application such as laser direct-writing, inertial confinement fusion, laser communication, laser radar, Laser Processings.Especially in Laser Processing, need to accomplish the position that can artificially set in far field, realize the flat top beam shaping that shape is any and bore is variable of laser beam, and it is extremely low to be shaped the light-intensity variation of light beam flat-top of precipitous while of edge of light beam.The fields such as laser hologram, Materialbearbeitung mit Laserlicht, laser medicine, often require the uniform laser beam of light intensity space distribution, and direct light beam is out generally Gaussian beam from laser instrument, and for little same laser instrument, waist radius is unequal, therefore need to pass through laser beam reshaping device, could be the equally distributed flat top beam of light intensity by Gauss beam reshaping.But existing technology cannot realize any desired location to far field, the shape of the laser beam of flat top beam shaping and bore are immutable, are shaped the large problem of edge light-intensity variation not precipitous and light beam flat-top of light beam.

Summary of the invention

The present invention cannot realize any desired location in order to solve existing technology to far field, and the shape of the laser beam of flat top beam shaping and bore are immutable, is shaped the large problem of edge light-intensity variation not precipitous and light beam flat-top of light beam.

A kind ofly realize the flat top beam apparatus for shaping that edge is precipitous and light-intensity variation is low, it comprises optical phased array, lens, output face, intensive analysis acquisition module and processor module, lens are between the face and output face at optical phased array place, distance between lens and phased array and output face is one times of focal distance f, incident beam carries out shaping through lens Fourier pair light beam again by optical phased array, focal plane position at lens is that output plane obtains the light field after shaping, the beam intensity of the light field of intensity distributions acquisition module after to the shaping of output face gathers, by the data transmission collecting to processor module, processor module is by calculating RMSE value and judging the value of RMSE, thereby determine whether to adjust the phase place of optical phased array.

Realize a reforming control method for the flat top beam apparatus for shaping that edge is precipitous and light-intensity variation is low, it comprises the steps: one, according to formula (1), obtains initial phase φ ₁,

φ ₁=φ _F+2π(rand-0.5)sinc ^-1(|A _F|) (1)

φ _fintensity distributions I for light beam expection _tafter fast fourier transform, the space phase of light field distributes, A _fintensity distributions I for light beam expection _tafter fast fourier transform, the spatial amplitude of light field distributes, and rand is the stochastic distribution between 0 to 1, sinc ^-1inverse function for sinc function;

Two, the φ of step 1 ₁according to formula (2), obtain U _k, the fast fourier transform of scioptics calculates the PHASE DISTRIBUTION Φ of output face _k, according to formula (4), calculate the intensity distributions I of the actual acquisition of output face _k, the intensity distributions I that intensive analysis acquisition module collects _k, the actual intensity distributions I obtaining _kprogressively to approach the intensity distributions of shaping light beam expection be I in convergence _t, i.e. k=∞ ideally, I _k=I _t,

$U_k=\sqrt{I_G}\exp \left({\mathrm{i\φ}}_k\right)---\left(2\right)$

Φ _k=arg(FFT(U _k)) (3)

I _k=|FFT(U _k)| ² (4)

Wherein, I _gfor the intensity distributions of incoming laser beam, U _kfor the light field complex amplitude of output face outgoing, k is iterations, k=1, and 2 ... n, n>=2, arg is the function of asking argument of a complex number, and FFT is fast fourier transform, and exp represents e index, and i is the definition for imaginary unit in plural number;

Three, according to the intensity distributions I of step 2 _twith PHASE DISTRIBUTION Φ _kby step (5), calculate light field V _k,

$V_k=w_k\·\sqrt{I_T}\exp \left({\mathrm{i\Φ}}_k\right)$ (5)

Wherein, w _kfor adaptive weighting w ₁=1, k=1,2 ... n, n>=2;

Four, utilize the root-mean-square error RMSE of the light-intensity variation that formula (6) calculates as the standard of optimizing assessment, processor module is for calculating current RMSE value and judging whether current RMSE value meets the RMSE value that user requires, be judged as YES, processor module stops carrying phase to optical phased array _k; Be judged as NO, proceed next iteration, operation formula (7) and formula (8) calculate the phase that is written into optical phased array _k+1, system continues iteration until processor module is judged as YES jumps out, and its expression formula is:

$\mathrm{RMSE}=\sqrt{\underset{p=1}{\overset{N}{\mathrm{\Σ}}}{(I_k-I_T)}^2/\underset{p=1}{\overset{N}{\mathrm{\Σ}}}{I}_T}---\left(6\right)$

φ _k+1=arg(IFFT(V _k)) (7)

w _k+1=w _k(I _T/|V _k| ²) ^c (8)

Wherein, p=1,2....N, N>=2, are the employing point-number sequence in intensity distributions region, and C is Optimization Factor, and value is in 0 to 1 scope, w _k+1for the adaptive weighting of algorithm iteration next time, IFFT is invert fast fourier transformation,

The RMSE value that user requires and the optimization acquisition methods of the C value in formula (8) are: setting iterations k is some, in C span 0 to 1, C value is since 0, adjusting stepping is 0.01, after often completing the algorithm iteration of set point number, C increases by 0.01, until C=1 optimizes, finish, choose C value and optimize and revise the RMSE value that RMSE minimum in process requires for user, now corresponding C value is adopted by formula (5).

Advantage of the present invention is: the position that can artificially set in far field, realize arbitrary shape and the variable flat top beam shaping of bore of laser beam; The edge that is shaped light beam is precipitous; The light-intensity variation that is shaped light beam is low; Can realize the flat top beam shaping that real-time adaptive shape is any and bore is variable.The present invention utilizes phase calculation optimisation strategy, according to shaping, needs, and optimizes and needs corresponding PHASE DISTRIBUTION, then PHASE DISTRIBUTION is written into optical phased array, thereby reaches the object of real-time adaptive beam shaping.

Accompanying drawing explanation

Fig. 1 is a kind of apparatus structure schematic diagram of realizing the flat top beam shaping adaptive shaping that edge is precipitous and light-intensity variation is very low; Fig. 2 is incoming laser beam intensity distribution, and Fig. 3 is the sectional view along center horizontal direction of incoming laser beam intensity distributions; Fig. 4 is the intensity distribution of light beam after expection shaping; Fig. 5 is the sectional view along center horizontal direction of the intensity distributions of light beam after expection shaping; Fig. 6 is that the strength fluctuation RMSE of light beam is along with the curve of the variation of C value; Fig. 7 is the amplification of Fig. 6 curve map; Fig. 8 is for to calculate based on apparatus for shaping and control method the PHASE DISTRIBUTION that meets shaping demand; Fig. 9 is for calculating and meet the PHASE DISTRIBUTION of shaping demand along the sectional view of center horizontal direction based on apparatus for shaping and control method; Figure 10 is for completing based on apparatus for shaping and control method the flat top beam intensity distributions obtaining on output plane 3 after shaping; Figure 11 is for completing the flat top beam intensity distributions that obtains on output plane 3 after shaping along the sectional view of center horizontal direction based on apparatus for shaping and control method; Figure 12 is the 128x128x (λ with expection _f/D) to be target complete the intensity distributions that obtains on far field output plane 3 after shaping along the sectional view of center horizontal direction based on apparatus for shaping and control method to um bore square intensity distributions; Figure 13 is the 96x96x (λ with expection _f/D) to be target complete the intensity distributions that obtains on far field output plane 3 after shaping along the sectional view of center horizontal direction based on apparatus for shaping and control method to um bore square intensity distributions; Figure 14 is the 64x64x (λ with expection _f/D) to be target complete the intensity distributions that obtains on far field output plane 3 after shaping along the sectional view of center horizontal direction based on apparatus for shaping and control method to um bore square intensity distributions; Figure 15 is the 47x (λ with expection _f/D) to be target complete the intensity distributions that obtains on far field output plane 3 after shaping along the sectional view of center horizontal direction based on apparatus for shaping and control method to um ring radius annular intensity distributions; Figure 16 is the 37x (λ with expection _f/D) to be target complete the intensity distributions that obtains on far field output plane 3 after shaping along the sectional view of center horizontal direction based on apparatus for shaping and control method to um ring radius annular intensity distributions; Figure 17 is the 27x (λ with expection _f/Dd) to be target complete the intensity distributions that obtains on far field output plane 3 after shaping along the sectional view of center horizontal direction based on apparatus for shaping and control method to um ring radius annular intensity distributions.

Embodiment

Embodiment one, a kind ofly realize the flat top beam apparatus for shaping that edge is precipitous and light-intensity variation is low, it comprises optical phased array 1, lens 2, output face 3, intensive analysis acquisition module 4 and processor module 5, lens 2 are between the face and output face 3 at optical phased array 1 place, distance between lens 2 and phased array 1 and output face 3 is one times of focal distance f, incident beam carries out shaping through lens 2 Fourier pair light beams again by optical phased array 1, focal plane position at lens 2 is that output plane 3 obtains the light field after shaping, the beam intensity of the light field after the shaping of 4 pairs of output faces 3 of intensity distributions acquisition module gathers, by the data transmission collecting to processor module 5, processor module 5 is by calculating RMSE value and judging the value of RMSE, thereby determine whether to adjust the phase place of optical phased array 1.

Lens 2 play Fourier variation effect, and this device has the position that can artificially set in far field, realize any given shape of laser beam and the flat top beam shaping characteristic of given bore.

Embodiment two, for a kind of reforming control method of realizing the flat top beam apparatus for shaping that edge is precipitous and light-intensity variation is low described in embodiment one, it comprises the steps:

One, according to formula (1), obtain initial phase φ ₁,

φ ₁=φ _F+2π(rand-0.5)sinc ^-1(|A _F|) (1)

φ _fintensity distributions I for light beam expection _tafter fast fourier transform, the space phase of light field distributes, A _fintensity distributions I for light beam expection _tafter fast fourier transform, the spatial amplitude of light field distributes, and rand is the stochastic distribution between 0 to 1, sinc ^-1inverse function for sinc function;

Two, the φ of step 1 ₁according to formula (2), obtain U _k, the fast fourier transform of scioptics 2 calculates the PHASE DISTRIBUTION Φ of output face 3 _k, according to formula (4), calculate the intensity distributions I of the actual acquisition of output face 3 _k, the intensity distributions I that intensive analysis acquisition module 4 collects _k, the actual intensity distributions I obtaining _kprogressively to approach the intensity distributions of shaping light beam expection be I in convergence _t, i.e. k=∞ ideally, I _k=I _t,

$U_k=\sqrt{I_G}\exp \left({\mathrm{i\φ}}_k\right)$

Φ _k=arg(FFT(U _k)) (3)

I _k=|FFT(U _k)| ² (4)

Wherein, I _gfor the intensity distributions of incoming laser beam, U _kfor the light field complex amplitude of output face outgoing, k is iterations, k=1, and 2 ... n, n>=2, arg is the function of asking argument of a complex number, and FFT is fast fourier transform, and exp represents e index, and i is the definition for imaginary unit in plural number;

Three, according to the intensity distributions I of step 2 _twith PHASE DISTRIBUTION Φ _kby step (5), calculate light field V _k,

$V_k=w_k\·\sqrt{I_T}\exp \left({\mathrm{i\Φ}}_k\right)$

Wherein, w _kfor adaptive weighting w ₁=1, k=1,2 ... n, n>=2;

Four, utilize the root-mean-square error RMSE of the light-intensity variation that formula (6) calculates as the standard of optimizing assessment, processor module 5 is for calculating current RMSE value and judging whether current RMSE value meets the RMSE value that user requires, be judged as YES, processor module 5 stops carrying phase to optical phased array _k; Be judged as NO, proceed next iteration, operation formula (7) and formula (8) calculate the phase that is written into optical phased array _k+1, system continues iteration until processor module 5 is judged as YES jumps out, and its expression formula is:

$\mathrm{RMSE}=\sqrt{\underset{p=1}{\overset{N}{\mathrm{\Σ}}}{(I_k-I_T)}^2/\underset{p=1}{\overset{N}{\mathrm{\Σ}}}{I}_T}---\left(6\right)$

φ _k+1=arg(IFFT(V _k)) (7)

w _k+1=w _k(I _T/|V _k| ²) ^c (8)

Wherein, p=1,2....N, N>=2, are the employing point-number sequence in intensity distributions region, and C is Optimization Factor, and value is in 0 to 1 scope, w _k+1for the adaptive weighting of algorithm iteration next time, IFFT is invert fast fourier transformation, the RMSE value that user requires and the optimization acquisition methods of the C value in formula (8) are: setting iterations k is some, in C span 0 to 1, C value is since 0, adjusting stepping is 0.01, after often completing the algorithm iteration of set point number, C increases by 0.01, until optimizing, finishes C=1, choose C value and optimize and revise the RMSE value that RMSE minimum in process requires for user, now corresponding C value is adopted by formula (5).

The difference of embodiment three, present embodiment and embodiment one is: focal distance f can reach axial zoom with the lens 2 formation combined focal lengths in device by the PHASE DISTRIBUTION of the lens 2 that superpose on optical phased array 1, thereby reaches the object that is shaped beam intensity in axial given position output; Intensity distributions by artificial setting shaping light beam expection is I _tshape and bore, can obtain in output face 3 positions the flat top beam of respective shapes and bore.

Present embodiment can reach the position that far field can artificially be set, and realizes any given shape of laser beam and the flat top beam shaping characteristic of given bore.Incident light source is that wavelength is the laser of λ, and its beam intensity can be expressed as:

I _Gauss=exp[-2(x ²+y ²)/ω ²] (9)

ω is that Gaussian beam is at 1/e ²radius, make ω=5mm, wave filter bore D is 7.68mm; Their 512 * 512 points of sampling number, incoming laser beam as shown in Figures 2 and 3.Wavelength is λ, and focal length is f, and the spatial resolution of the output plane in far field is λ f/D, for far field, adopts 512 * 512 the some situations of counting, and the spatial dimension in far field is (λ f/D) 512 μ m.The intensity distributions scope that makes the expection light beam of given position, far field be 256 * 256 * λ f/D as shown in Figure 4 and Figure 5.The RMSE value requiring according to the user in step 4 in embodiment two and the C value optimisation strategy in formula (5), RMSE value and the C value in formula (5) that user's requirement is obtained in optimization are as follows: setting iterations k is 100 times, C value is since 0, adjusting stepping is 0.01, after often completing the algorithm iteration of set point number, C increases by 0.01, until C=1 optimizes, finishes.The strength fluctuation RMSE of the light beam obtaining along with the change curve of C value as shown in Figure 6 and Figure 7.Fig. 6 and Fig. 7 are all the strength fluctuation RMSE of light beam of acquisition along with the curve of the variation of C value, and wherein Fig. 7 is the amplification of Fig. 6.By optimizing, can obtain when the C=0.49, RMSE minimum is 0.0094; Be RMSE value that user requires be 0.0094 and formula (5) in C value be 0.49.Utilizing a kind of described in embodiment one to realize edge is precipitous and light-intensity variation is low flat top beam apparatus for shaping and the reforming control method described in embodiment two calculates for expecting that PHASE DISTRIBUTION that beam intensity divides shaping as shown in Figure 8 and Figure 9, the far-field intensity distribution of acquisition after shaping completes, as shown in Figure 10 and Figure 11.Intensity distributions by artificial setting shaping light beam expection is I _tbe difformity and bore, for example, the flat top beam of expection is respectively 128 * 128 * (λ _f/D) μ m, 96 * 96 * (λ _f/D) μ m, 64 * 64 * (λ _f/D) μ m square intensity distributions and ring radius be respectively 47 * (λ _f/D) μ m, 37 * (λ _f/D) μ mand27 * (λ _f/D) annular intensity distribution of μ m. for the intensity distributions of each expection, utilize respectively above-mentioned steps for aforesaid incoming laser beam, implement respectively as shown in Figures 2 and 3 shaping, in given far field, being the beam intensity that obtains of output plane 3 places corresponds to respectively Figure 12 along the sectional view of center horizontal direction, Figure 13, Figure 14, Figure 15, Figure 16, shown in Figure 17.

Claims (1)

1. a reforming control method of realizing the flat top beam apparatus for shaping that edge is precipitous and light-intensity variation is low, the described flat top beam apparatus for shaping that edge is precipitous and light-intensity variation is low of realizing comprises optical phased array (1), lens (2), output face (3), intensive analysis acquisition module (4) and processor module (5), lens (2) are positioned between the face and output face (3) at optical phased array (1) place, distance between lens (2) and phased array (1) and output face (3) is one times of focal distance f, incident beam passes through lens (2) Fourier pair light beam by optical phased array (1) again and carries out shaping, focal plane position at lens (2) is that output plane (3) obtains the light field after shaping, the beam intensity of the light field of intensity distributions acquisition module (4) after to the shaping of output face (3) gathers, by the data transmission collecting to processor module (5), processor module (5) is by calculating RMSE value and judging the value of RMSE, thereby determine whether to adjust the phase place of optical phased array (1),

It is characterized in that: the method comprises the steps:

One, according to formula (1), obtain initial phase φ ₁,

φ ₁=φ _F+2π(rand-0.5)sinc ^-1(|A _F|) (1)

φ _fintensity distributions I for light beam expection _tafter fast fourier transform, the space phase of light field distributes, A _fintensity distributions I for light beam expection _tafter fast fourier transform, the spatial amplitude of light field distributes, and rand is the stochastic distribution between 0 to 1, sinc ^-1inverse function for sinc function;

Two, the φ of step 1 ₁according to formula (2), obtain U _k, the fast fourier transform of scioptics (2) calculates the PHASE DISTRIBUTION Φ of output face (3) _k, according to formula (4), calculate the intensity distributions I of the actual acquisition of output face (3) _k, the intensity distributions I that intensive analysis acquisition module (4) collects _k, the actual intensity distributions I obtaining _kprogressively to approach the intensity distributions of shaping light beam expection be I in convergence _t, i.e. k=∞ ideally, I _k=I _t,

$U_k=\sqrt{I_G}\exp \left({\mathrm{i\φ}}_k\right)$

Φ _k=arg(FFT(U _k)) (3)

I _k=|FFT(U _k)| ² (4)

Wherein, I _gfor the intensity distributions of incoming laser beam, U _kfor the light field complex amplitude of output face outgoing, k is iterations, k=1, and 2 ... n, n>=2, arg is the function of asking argument of a complex number, and FFT is fast fourier transform, and exp represents e index, and i is the definition for imaginary unit in plural number;

Three, according to the intensity distributions I of step 2 _twith PHASE DISTRIBUTION Φ _kby step (5), calculate light field V _k,

$V_k=w_k\·\sqrt{I_T}\exp \left({\mathrm{i\Φ}}_k\right)$

Wherein, w _kfor adaptive weighting w ₁=1, k=1,2 ... n, n>=2;

Four, utilize the root-mean-square error RMSE of the light-intensity variation that formula (6) calculates as the standard of optimizing assessment, processor module (5) is for calculating current RMSE value and judging whether current RMSE value meets the RMSE value that user requires, be judged as YES, processor module (5) stops carrying phase to optical phased array _k; Be judged as NO, proceed next iteration, operation formula (7) and formula (8) calculate the phase that is written into optical phased array _k+1, system continues iteration until processor module (5) is judged as YES jumps out,

Its expression formula is:

$\mathrm{RMSE}=\sqrt{\underset{p=1}{\overset{N}{\mathrm{\Σ}}}{(I_k-I_T)}^2/\underset{p=1}{\overset{N}{\mathrm{\Σ}}}{I}_T}---\left(6\right)$

φ _k+1=arg(IFFT(V _k)) (7)

w _k+1=w _k(I _T/|V _k| ²) ^c (8)

Wherein, p=1,2....N, N>=2, are the employing point-number sequence in intensity distributions region, and C is Optimization Factor, and value is in 0 to 1 scope, w _k+1for the adaptive weighting of algorithm iteration next time, IFFT is invert fast fourier transformation,

The RMSE value that user requires and the optimization acquisition methods of the C value in formula (8) are: setting iterations k is some, in C span 0 to 1, C value is since 0, adjusting stepping is 0.01, after often completing the algorithm iteration of set point number, C increases by 0.01, until C=1 optimizes, finish, choose C value and optimize and revise the RMSE value that RMSE minimum in process requires for user, now corresponding C value is adopted by formula (5).