發(fā)布時(shí)間：2018-06-21 22:36

  本文選題：大偏轉(zhuǎn)角 + 液晶光柵　； 參考：《長江大學(xué)》2016年碩士論文

【摘要】：光學(xué)相控陣技術(shù)的工作原理是在電光材料的電光效應(yīng)下,通過改變加載在不同相控單元的電壓來改變通過不同相控單元光波的相位、光強(qiáng)等光學(xué)特性,以此來達(dá)到對(duì)每個(gè)單元光波的獨(dú)立控制。它在實(shí)現(xiàn)激光束偏轉(zhuǎn)中應(yīng)用很廣泛。本文講述的液晶光柵相控陣就是以液晶分子充當(dāng)電光材料的光學(xué)相控陣。液晶分子在電場(chǎng)作用下,排列方向得到改變,且它們的折射率不同,使得通過它的光束方向發(fā)生一定角度的偏轉(zhuǎn)。為了更夠更好的實(shí)現(xiàn)液晶光柵角度的偏轉(zhuǎn),就要了解它的波前畸變情況。本文概括描述了液晶光柵相控陣和波前測(cè)量技術(shù)的發(fā)展情況,以及液晶光柵的性質(zhì)和工作原理。分析了不同類型相位輪廓誤差對(duì)液晶光柵器件性能的影響,以及液晶光柵的衍射光場(chǎng)特性,并用matlab仿真技術(shù)模擬了在不同情況下衍射光場(chǎng)光強(qiáng)、相位的分布情況,為液晶光柵波前測(cè)試方法的選擇提供科學(xué)依據(jù)。通過分析選擇出合適的波前測(cè)試方法即單一衍射級(jí)反演法來測(cè)量液晶光柵的誤差相位輪廓,測(cè)量系統(tǒng)測(cè)出近場(chǎng)+1級(jí)衍射波前,用單一衍射級(jí)反演法來反演出此時(shí)液晶光柵的波前相位情況,把這個(gè)情況反饋給波控器。波控器就是對(duì)液晶光柵施加電壓指令的裝置,在它得到相位反饋后,根據(jù)測(cè)得的已知的電壓-相位關(guān)系來改變施加電壓數(shù)據(jù),從而再度調(diào)整出射光束質(zhì)量。這樣不斷反饋重復(fù)就可以得到高質(zhì)量的偏轉(zhuǎn)光束。研究了液晶光柵波前測(cè)量系統(tǒng)的光路結(jié)構(gòu)。采用四邊形徑向剪切干涉法來測(cè)量衍射波前,該方法有剪切干涉法的優(yōu)點(diǎn),就是不需要引入?yún)⒖疾�。通過液晶光柵發(fā)生衍射的光束在分束棱鏡后被分成了兩束光：反射光和透射光,分別對(duì)其擴(kuò)束和縮束,最后在分束棱鏡后面會(huì)合,一大一小兩個(gè)光斑重合產(chǎn)生干涉條紋圖。通過條紋圖即可重構(gòu)出衍射波前。通過光學(xué)設(shè)計(jì)軟件來模擬這個(gè)光路結(jié)構(gòu),為能精確測(cè)量衍射波面,各元件間距符合4f系統(tǒng)的要求。建立一個(gè)開普勒望遠(yuǎn)系統(tǒng)結(jié)構(gòu)用于縮、擴(kuò)光束,模擬它的光路,并分析透鏡參數(shù)對(duì)望遠(yuǎn)系統(tǒng)像差的影響以及分束棱鏡偏轉(zhuǎn)時(shí)的光路發(fā)生的變化。對(duì)不同載波頻率的干涉條紋頻譜和幾種特殊波面入射時(shí)的干涉情況進(jìn)行了仿真。仿真結(jié)果對(duì)測(cè)量系統(tǒng)的搭建及調(diào)試具有指導(dǎo)意義。搭建了液晶光柵波前測(cè)量系統(tǒng),并對(duì)實(shí)際的大偏轉(zhuǎn)角液晶光柵進(jìn)行了實(shí)測(cè)實(shí)驗(yàn)。首先對(duì)該剪切干涉儀進(jìn)行標(biāo)定,并測(cè)試了液晶光柵的靜態(tài)相位分布及光束偏轉(zhuǎn)時(shí)的液晶光柵相位輪廓,最后對(duì)實(shí)驗(yàn)結(jié)果進(jìn)行了分析。
[Abstract]:The principle of optical phased array technology is to change the phase and intensity of light waves through different phase control units by changing the voltage loaded in different phase control units under the electro-optic effect of electro-optic materials. In order to achieve independent control of each unit of light waves. It is widely used in the realization of laser beam deflection. The liquid crystal grating phased array described in this paper is an optical phased array using liquid crystal molecules as electro-optic materials. Under the action of electric field, the alignment direction of liquid crystal molecules is changed, and their refractive index is different, which makes the beam direction of liquid crystal deflect at a certain angle. In order to better realize the angle deflection of liquid crystal grating, it is necessary to understand its wavefront distortion. This paper describes the development of liquid crystal grating phased array and wavefront measurement technology, as well as the properties and working principle of liquid crystal grating. The effect of different phase profile errors on the performance of liquid crystal grating devices and the diffraction light field characteristics of liquid crystal grating are analyzed. The intensity and phase distribution of the diffraction light field are simulated by matlab simulation technology. It provides a scientific basis for the selection of liquid crystal grating wavefront measurement method. By analyzing and selecting the suitable wave front measurement method, that is, single diffraction order inversion method, the error phase profile of liquid crystal grating is measured, and the near field 1 order diffraction wave front is measured by the measuring system. The inversion method of single diffraction order is used to invert the wavefront phase of the liquid crystal grating at this time, and the situation is fed back to the wave controller. A wave controller is a device that applies voltage instructions to liquid crystal gratings. After phase feedback is obtained, the applied voltage data are changed according to the known voltage-phase relationship, and the beam quality is adjusted again. In this way, a high quality deflection beam can be obtained by repeated feedback. The optical structure of liquid crystal grating wavefront measurement system is studied. The quadrilateral radial shearing interferometry is used to measure diffraction wavefront. This method has the advantage of shearing interferometry, that is, there is no need to introduce reference wave. The beam diffracted by the liquid crystal grating is divided into two beams after beamsplitting prism: reflected light and transmitted light, which are expanded and shrunk respectively. Finally, they meet behind the splitter prism, and the interference fringes are produced by the coincidence of two light spots, one large and one small. Diffraction wavefront can be reconstructed by fringe pattern. The optical design software is used to simulate the optical structure. In order to accurately measure the diffraction wave surface, the distance between the elements meets the requirements of the 4f system. A Kepler telescope system structure is established to reduce and spread the beam, to simulate its optical path, and to analyze the influence of lens parameters on the aberration of the telescope system and the changes of the beam path when the beam splitting prism is deflected. The interference patterns of different carrier frequencies and several special wave planes are simulated. The simulation results are of guiding significance to the construction and debugging of the measurement system. The liquid crystal grating wavefront measurement system is built, and the real liquid crystal grating with large deflection angle is tested. First, the shear interferometer is calibrated, the static phase distribution of liquid crystal grating and the phase profile of liquid crystal grating during beam deflection are measured. Finally, the experimental results are analyzed.
【學(xué)位授予單位】：長江大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：O753.2

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