CN1912563A - Atmospheric turbulent optical effect luboratory analog system based on micro-optical technology - Google Patents

Abstract

A laboratory analog system of atmosphere turbulent optical effect based on micro optical technology uses driving unit to drive random phase disc to rotate for simulating dynamic modulation effect of atmospheric turbulence to optical wave phase.

Description

Atmospheric turbulence optical effect laboratory analog system based on the micro-optic technology

Technical field

The present invention relates to a kind of atmospheric turbulence optical effect laboratory analog system, be under the jurisdiction of technical fields such as micro-optic, atmospheric optics, adaptive optics.

Background technology

Along with atmospheric optics and space optics continuous advancement in technology, become focus gradually in the research of testing lab simulation atmospheric turbulence optical effect.When electromagnetic wave was propagated in atmosphere, turbulent perturbation made air refraction generation random variation, thereby causes electromagnetic phase place generation random fluctuation.For example phenomenons such as wavefront distortion, arrival angle fluctuation, beam drift promptly are the results of atmospheric turbulence influence.In many important military, civilian technology field, as astronomical imaging, optical communication, homing guidance, remote sensing, and other relates to electromagnetic wave transmission technology field in air, and the influence of atmospheric turbulence has seriously reduced the quality of electro-optical system.Therefore, in the middle of the process of these systematic researches, design and debugging, turbulent flow just becomes the research contents of a key to the electro-optical system Effect on Performance.In order to obtain essential to work in experimental data under the atmospheric turbulence environment about electro-optical system, one of approach is to carry out field experiment.Because above-mentioned field, field experiment is often time-consuming, complicated, and cost is very high.Especially Xian Chang turbulent flow comes from nature, and neither can artificially control does not have repeatability yet, and this obviously is extremely inconvenient from the angle of experimental study.These restrictions of field experiment make people know little about it to many problems that are related to the optical property of turbulent flow.Therefore, a kind of thought at experiment lab simulation atmospheric turbulence has appearred in recent years.This thought is a kind of experimental system of design under laboratory condition, it to light intensity and position when the statistical nature-structure function, power spectrum etc. of modulation pass through natural atmospheric turbulence with light mutually modulated statistical nature consistent.This system can remedy the deficiency of field experiment well.It both can be used for studying the behavior that electromagnetic wave is propagated in atmospheric turbulence, obtain important experimental data, also played irreplaceable effect in research, design and the test of electro-optical system.

At present, how tame in the world unit has all carried out the research of this respect, as aerodynamic experiment chamber, the adaptive optics center of University of Arizona, the University of Maryland of the U.S., the Bu Laikete laboratory of Britain and Muscovite Moscow State University etc.The scheme that realizes the turbulent flow simulation system mainly contains gas methods and liquid processes, distorting lens method and liquid crystal method.Gas and liquid processes are to utilize the convection current of gas or liquid to form turbulent flow under laboratory condition, its physical principle is simple, do not have too many theory hypothesis, it is a kind of traditional method, but poor repeatability, the heat that distributes have adverse effect to optical instrument, time and space can not independently be regulated and control, the also bad control of the intensity of the turbulent flow that can simulate.Distorting lens and liquid crystal method are to utilize the fundamental function of known light wave, produce corresponding Stochastic Modulation device, and the distorting lens method is to utilize the surface deformation of distorting lens, and the liquid crystal method is that the refractive index that changes liquid crystal realizes.The advantage of these two kinds of methods is that repeatability can independently be controlled, be had to the adverse effect to instrument, compact conformation, the time and space that do not have heat to cause, but its shortcoming also is clearly: (1) system complex, cost height; (2) because the restriction of its driver density makes that position phase surface figure accuracy is limited, thus the accuracy of influence simulation turbulent flow.The deficiency of above-mentioned these methods is limiting people in varying degrees to atmospheric turbulence and the research that works in electro-optical system wherein.

Summary of the invention

Technology of the present invention is dealt with problems: overcome the deficiencies in the prior art, but provide a kind of accuracy good, convenient dynamic similation, system compact, the lower-cost atmospheric turbulence optical effect laboratory analog system based on the micro-optic technology regulated.

Technical solution of the present invention: based on the atmospheric turbulence optical effect laboratory analog system of micro-optic technology, its characteristics are: it is made up of random order photograph and gearing, gearing drives the random order photograph and rotates, with the dynamic modulation effect of simulation atmospheric turbulence to light wave position phase.

The design of described random order photograph and making:

(1) according to the power spectrum model of atmospheric turbulence and the spatial coherence length r of atmospheric turbulence ₀, utilize fourier transform method to produce random phase and distribute;

Adopt fourier transform method, produce random phase by power spectrum and distribute, promptly

$\mathrm{\φ}\left(\stackrel{\→}{\mathrm{\ρ}}\right)=\frac{1}{\sqrt{2}}\∫\sqrt{F\left(k\right)}\left\{a\left(\stackrel{\→}{k}\right)\cos \right\{\stackrel{\→}{k}\·\stackrel{\→}{\mathrm{\ρ}}\}+b\left(\stackrel{\→}{k}\right)\sin \{\stackrel{\→}{k}\·\stackrel{\→}{\mathrm{\ρ}}\left\}\right\}d\stackrel{\→}{k},---\left(1a\right)$

$F\left(k\right)=0.489r_0{}^{-\frac{5}{3}}k^{-\frac{11}{3}},---\left(b\right)$

Wherein

Be two-dimensional random position phase distribution function, Be the two-dimensional space coordinate, F (k) is the turbulent flow power spectrum function,

Be the two-dimensional space wave vector, and $k=\left|\stackrel{\→}{k}\right|,$

Be Gaussian random field, following condition is satisfied in its statistical average:

$\⟨a\left({\stackrel{\→}{k}}_1\right)b\left({\stackrel{\→}{k}}_2\right)\⟩=0$

$\⟨a\left({\stackrel{\→}{k}}_1\right)a\left({\stackrel{\→}{k}}_2\right)\⟩=\mathrm{\δ}(k_1-k_2),$

$\⟨b\left({\stackrel{\→}{k}}_1\right)b\left({\stackrel{\→}{k}}_2\right)\⟩=\mathrm{\δ}(k_1-k_2)$

$a\left(\stackrel{\→}{k}\right)=a(-\stackrel{\→}{k}),b\left(\stackrel{\→}{k}\right)=-b(-\stackrel{\→}{k}).---\left(3\right)$

The related function that (1) formula of utilization can obtain random phase is

$C_{\mathrm{\φ}}({\stackrel{\→}{\mathrm{\ρ}}}_1,H,{\stackrel{\→}{\mathrm{\ρ}}}_2,H)=\⟨\mathrm{\φ}({\stackrel{\→}{\mathrm{\ρ}}}_1,H)\mathrm{\φ}({\stackrel{\→}{\mathrm{\ρ}}}_2,H)\⟩$

$=\∫d\stackrel{\→}{k}{F}_{\mathrm{\φ}2}\left(k\right)\cos \{\stackrel{\→}{k}\·({\stackrel{\→}{\mathrm{\ρ}}}_1-{\stackrel{\→}{\mathrm{\ρ}}}_2)\}.$

Just the related function of this random phase satisfies the requirement of the power spectrum of atmospheric turbulence.

(2) surface that above-mentioned resulting position phase data is converted to suitable substrate height relief at random forms position photo.

(3) adopt microlithography technology to make position photo.

Principle of the present invention: under laboratory condition, have the position phase mudulation effect of the position photo simulation atmospheric turbulence of height relief at random to light with the surface, the employing gearing is used to simulate the promotion effect of wind-force to turbosphere.Because the spatial coherence length r of atmospheric turbulence ₀Directly related with the intensity of turbulent flow, so by changing r ₀Design load, can simulate the position phase mudulation effect of the turbulent flow of varying strength.Again because the temporal coherent length of turbulent flow is τ ₀=r ₀/ v, wherein v is a wind speed, then by regulating the velocity of rotation of gearing, can change temporal coherent length easily.The random order photograph is used to simulate the position mutually modulation of static turbulent flow to light, and this position photo can produce has the random phase that certain statistical distributes.

The present invention's advantage compared with prior art is: but but accuracy is good, the time of turbulent flow, spatial coherence length independent regulation dynamic similation, system compact, cost are lower.Accuracy well mainly be have benefited from the position mutually design be based on fast and effective Fourier industry transform method, in addition, the microlithography technology of making position photo can enter sub-micrometer scale so that make error.But but the time of turbulent flow, spatial coherence length independent regulation dynamic similation are by the characteristics decision of the system schema that adopts itself, but time, spatial coherence length independent regulation are because of r ₀Be a design parameter, it can suitably be regulated by design.As preceding described, temporal coherent length is relevant with the rotational speed of position photo, and therefore changing rotational speed just can change temporal coherent length.These two parameters are very important in the correlative study of atmospheric turbulence.Compactness of the present invention, cost are low be because the present invention for additive method, it is very little to take up room, and job operation make cost lower for mature technology.

Description of drawings

Fig. 1 is a schematic diagram of the present invention;

Fig. 2 is embodiments of the invention r ₀The design drawing of the random phase of=10cm;

The r that Fig. 3 makes for the embodiment of the invention ₀The face shape distribution (interferometer measurement) of the random order photograph of=10cm;

Fig. 4 is the comparison diagram of Design Theory power spectrum and measured power spectrum.

Embodiment

As shown in Figure 1, be embodiments of the invention 1, incident light comes from front end optical system, and clear aperture is adjustable, and bore is φ 40mm, and optical wavelength is 0.6328 μ m.Random order photograph profile is circular, and radius needs greater than clear aperture, is φ 100mm herein, and at the center rolling bearing is installed, and random phase in addition distributes in bearings mounted zone.The random phase sheet material is quartzy, and thickness is 6mm (generally according to material the through performance and the physical strength of light being decided).Utilize gearing to be motor, make the rotation of random order photograph, the position phase modulation effect that promptly can simulate dynamic turbulent flow by the driven by motor rolling bearing.Rotational speed does not have specific (special) requirements, according to the requirement decision of measurand.Entered the terminal optical system by the light beam after the modulation of random order photograph, promptly need under laboratory condition, finish the system that it works in the performance test in the atmospheric turbulence environment.By changing r ₀Design load, the position phase mudulation effect of turbulent flow of simulation varying strength; By regulating velocity of rotation, change temporal coherent length.

In the process of design data,, utilize the conversion of quick Fourier industry to produce the position and distribute mutually based on (1a) formula.In manufacturing process, utilize the mask of position phase distributed data design modulation light distribution, this mask is used to the position distributed mutually and is converted to light distribution, exposes on substrate, technologies such as development, etching, finally processes position photo.

As shown in Figure 2, be that the random phase of design distributes, horizontal ordinate represent the position on two orthogonal directionss on the position photo, and highly represents the random phase that is obtained through numerical evaluation by (1) formula.

As shown in Figure 3, be the interferometer measurement figure of position photo, horizontal ordinate is represented the position on two orthogonal directionss on the position photo, and the random phase of highly representing interferometer to measure.

As shown in Figure 4, horizontal ordinate is a spatial frequency, and ordinate is a spectral intensity.The comparison that on behalf of the design power spectrum and the measured power of position photo, this figure compose, the latter is obtained through the conversion of Fourier industry by related function.

Claims (2)

1, based on the atmospheric turbulence optical effect laboratory analog system of micro-optic technology, it is characterized in that: it is made up of random order photograph and gearing, and gearing drives the random order photograph and rotates, and the simulation atmospheric turbulence is to the dynamic modulation effect of light wave position phase.

2, the atmospheric turbulence optical effect laboratory analog system based on the micro-optic technology according to claim 1 is characterized in that: the making step of described random order photograph:

(1) according to the power spectrum model of atmospheric turbulence and the spatial coherence length r of atmospheric turbulence ₀, utilize fourier transform method to produce random phase and distribute;

(2) surface that above-mentioned resulting position phase data is converted to substrate height relief at random forms position photo;

(3) adopt microlithography technology to make position photo.

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