本文關(guān)鍵詞：基于近場(chǎng)聲學(xué)的超透鏡成像改進(jìn)方法研究　出處：《中北大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 近場(chǎng)聲學(xué) 聲子晶體 負(fù)折射 聲學(xué)超透鏡 倏逝波

【摘要】：近場(chǎng)聲學(xué)是近年來(lái)在光學(xué)飛速發(fā)展的基礎(chǔ)上發(fā)展起來(lái)的,該技術(shù)在保密防偽、軍事偵察、醫(yī)用檢查、水下探測(cè)、等各個(gè)方面獲得了廣泛的應(yīng)用,引起人們的關(guān)注。近場(chǎng)聲全息技術(shù)作為全息技術(shù)的一種,是光全息基礎(chǔ)上發(fā)展起來(lái)的,本文對(duì)基于空間Fourie變換的近場(chǎng)聲全息進(jìn)行了研究,分析了近場(chǎng)聲全息在成像中產(chǎn)生誤差的原因,并充分利用聲學(xué)超材料透鏡的完美成像性質(zhì)有針對(duì)性的對(duì)此進(jìn)行改進(jìn),對(duì)提高近場(chǎng)聲全息的分辨率,準(zhǔn)確識(shí)別和定位聲源具有指導(dǎo)意義。本文從聲波輻射理論入手,對(duì)理想流體介質(zhì)中穩(wěn)態(tài)小振幅聲波場(chǎng)分別在平面、柱面以及球面坐標(biāo)系下的Helmholtz方程求解,詳細(xì)研究了基于空間Fourie變換的近場(chǎng)聲全息在不同坐標(biāo)系下的算法實(shí)現(xiàn)以及誤差產(chǎn)生原因。產(chǎn)生誤差原因有:(1)全息面上的聲壓傳感器的離散分布帶來(lái)的“窗效應(yīng)”;(2)實(shí)測(cè)信號(hào)和分布在孔徑周圍無(wú)限多個(gè)“虛像”造成卷繞誤差;(3)攜帶聲源細(xì)節(jié)信息的倏逝波只存在于近場(chǎng)中,而全息面布置位置離聲源較遠(yuǎn),丟失聲源細(xì)節(jié)信息。通過(guò)第三章對(duì)亞波長(zhǎng)聲學(xué)超材料透鏡的成像研究,因負(fù)折射聲子晶體對(duì)攜帶聲源細(xì)節(jié)信息的倏逝波具有放大作用,所以倏逝波在通過(guò)超透鏡后才開(kāi)始衰減,受此啟發(fā),本文提出創(chuàng)新思想,即設(shè)計(jì)亞波長(zhǎng)聲學(xué)探頭置于聲源近場(chǎng)中,將聲源信息先匯聚于一點(diǎn),再在聚焦點(diǎn)用聲傳感器采集并重建。該方法不僅減小了因離散采集帶來(lái)的誤差,同時(shí)也將近場(chǎng)中的倏逝波一并重建,采集到的聲源信息完整,成像效果效果良好。文中運(yùn)用運(yùn)用COMSOL軟件對(duì)聲學(xué)超透鏡進(jìn)行了建模,并模擬仿真了點(diǎn)源通過(guò)透鏡的成像效果,像點(diǎn)聲壓值與物點(diǎn)聲壓值非常相近,成像效果良好,為上文創(chuàng)新思想提供有力的理論證據(jù)。
[Abstract]:Near-field acoustics has been developed in recent years on the basis of the rapid development of optics. The technology has been widely used in security, military reconnaissance, medical inspection, underwater detection, and so on. As a kind of holography technology, the near-field acoustic holography is developed on the basis of optical holography. In this paper, the near-field acoustic holography based on spatial Fourie transform is studied. The causes of errors in near-field acoustic holography are analyzed and the resolution of near-field acoustic holography is improved by making full use of the perfect imaging properties of acoustic metamaterial lens to improve the resolution of near-field acoustic holography. It is significant to identify and locate the sound source accurately. This paper starts with the theory of sound wave radiation, and the steady state small amplitude acoustic wave field in the ideal fluid medium is respectively in the plane. The Helmholtz equations in cylindrical and spherical coordinates are solved. The algorithm realization of near-field acoustic holography based on spatial Fourie transform in different coordinate systems and the cause of error are studied in detail. The "window effect" caused by the discrete distribution of the acoustic pressure sensor on the holographic surface; (2) the winding error caused by the measured signals and the infinite "virtual images" distributed around the aperture; 3) the evanescent wave with detail information of sound source only exists in the near field, but the position of the holographic plane is far away from the sound source, and the detail information of the sound source is lost. In chapter 3, the imaging of subwavelength acoustic metamaterial lens is studied. Because the negative refraction phonon crystal can amplify the evanescent wave which carries the detail information of the sound source, the evanescent wave only begins to decay after passing through the superlens. The sub-wavelength acoustic probe is designed to be placed in the near field of the sound source, the sound source information is gathered at a point first, and then the acoustic sensor is used to collect and reconstruct the sound source information in the focus. This method not only reduces the error caused by discrete acquisition. At the same time, the evanescent wave in the near field is reconstructed together, the sound source information collected is complete, and the imaging effect is good. In this paper, we use COMSOL software to model the acoustic superlens. The imaging effect of point source passing through lens is simulated. The image point sound pressure value is very close to the object point sound pressure value, and the imaging effect is good, which provides strong theoretical evidence for the above innovative ideas.
【學(xué)位授予單位】：中北大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：O429

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