Morpho Rhetenor蝴蝶翅膀结构光学散射电磁特性FDTD分析
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摘要
应用时域有限差分(FDTD)方法对Morpho rhetenor热带蝴蝶翅膀的光学散射特性进行电磁分析研究。通过数值分析的方法研究其在太阳光下发出绚丽蓝光的结构机理,为进一步应用这种特性开发特殊的军用及民用产品奠定研究基础。论文主要做了以下几方面的工作:
1) 本文应用外延平面技术,摒弃了传统FDTD中计算区域“回”字形划分模式和相应入射波加入方式,从而可以方便地在较小计算区域内对数万波长的整个蝴蝶翅膀结构的散射特性进行分析,最终数值结果验证了该方法的可行性。
2) 在数据输出边界上只对关心的部分频率点进行傅里叶变换,再在频域内进行近远场外推,从而适合同时计算若干频点上多个角度的电磁散射特性,大大减小了计算复杂度和内存消耗。
3) 为了本论文研究成果能在隐身技术和其它材料结构设计领域有所帮助,文中除了对散射光强特性进行了分析,把雷达散射截面(RCS)引入计算分析,从而利于相关研究工作的进一步深入。
4) 在以上研究基础上,利用缩比原理,对毫米波段的结构模型参数进行了设计,并应用FDTD方法进行分析计算,验证了这种蝴蝶翅膀结构的散射特性在毫米波频段应用的可行性,从而为我国毫米波段的吸波材料设计奠定了一定的理论基础。
这种蝴蝶翅膀结构具有如下两个特点:1)只反射蓝光而其它颜色光线可以透射到蝴蝶翅膀背面;2)后向散射场很弱而偏离后向一定角度处散射较强。以上特点的结构材料正是现代隐身技术中所期望的,这为相应吸波材料的研制提供了一个全新的思路。
The thesis emphasize on electromagnetic (EM) analysis of the optical scattering by wings of tropical butterfly called Morpho rhetenor with finite difference time domain (FDTD) method. The reason why wings of the butterfly look blue is analyzed in this thesis, and furthermore, this characteristic can be used for special commercial or military products design. The thesis includes the following works:1. Extensional plane technique is applied in the thesis, as a result, the traditional computational region selection method and corresponding incidence wave adding approach is modified, so that FDTD can be employed to analyze the EM scattering of the whole electrically large wings of butterfly in a smaller calculation region conveniently.2. Fourier transforming method is used only at several concerned frequencies, then near field to far field transformation is applied within these frequencies, consequently, calculation complexity and memory consuming is reduced rapidly with FDTD analysis for several frequency points and all angles.3. Aiming at the application to stolen technique or other material structural designing, not only the total reflection of intensity of light is analyzed, but also the radar cross section (RCS) is computed, thereby, the research can benefit to the future work.4. Based on the research above, parameters of the structural model in the millimeter wave band are designed, and then the associate model is analyzed with FDTD. The numerical results presented validate the feasibility of extending the bluffer wing model to millimeter wave band, so some initial works are done with the goal of absorbing material designation in the millimeter wave band for our country.The configuration of wings of butterfly have two characteristics as follows: 1) it only reflect blue light and other lights can pass though the wings of butterfly, 2) the scattering filed in back direction is very weak, it is strengthened in other directions 30 degrees to 60 degrees away from the back. These two characteristics mentioned above are what we want in modern stolen techniques, it provides a new approach for the absorbing material designation.
1) 本文应用外延平面技术,摒弃了传统FDTD中计算区域“回”字形划分模式和相应入射波加入方式,从而可以方便地在较小计算区域内对数万波长的整个蝴蝶翅膀结构的散射特性进行分析,最终数值结果验证了该方法的可行性。
2) 在数据输出边界上只对关心的部分频率点进行傅里叶变换,再在频域内进行近远场外推,从而适合同时计算若干频点上多个角度的电磁散射特性,大大减小了计算复杂度和内存消耗。
3) 为了本论文研究成果能在隐身技术和其它材料结构设计领域有所帮助,文中除了对散射光强特性进行了分析,把雷达散射截面(RCS)引入计算分析,从而利于相关研究工作的进一步深入。
4) 在以上研究基础上,利用缩比原理,对毫米波段的结构模型参数进行了设计,并应用FDTD方法进行分析计算,验证了这种蝴蝶翅膀结构的散射特性在毫米波频段应用的可行性,从而为我国毫米波段的吸波材料设计奠定了一定的理论基础。
这种蝴蝶翅膀结构具有如下两个特点:1)只反射蓝光而其它颜色光线可以透射到蝴蝶翅膀背面;2)后向散射场很弱而偏离后向一定角度处散射较强。以上特点的结构材料正是现代隐身技术中所期望的,这为相应吸波材料的研制提供了一个全新的思路。
The thesis emphasize on electromagnetic (EM) analysis of the optical scattering by wings of tropical butterfly called Morpho rhetenor with finite difference time domain (FDTD) method. The reason why wings of the butterfly look blue is analyzed in this thesis, and furthermore, this characteristic can be used for special commercial or military products design. The thesis includes the following works:1. Extensional plane technique is applied in the thesis, as a result, the traditional computational region selection method and corresponding incidence wave adding approach is modified, so that FDTD can be employed to analyze the EM scattering of the whole electrically large wings of butterfly in a smaller calculation region conveniently.2. Fourier transforming method is used only at several concerned frequencies, then near field to far field transformation is applied within these frequencies, consequently, calculation complexity and memory consuming is reduced rapidly with FDTD analysis for several frequency points and all angles.3. Aiming at the application to stolen technique or other material structural designing, not only the total reflection of intensity of light is analyzed, but also the radar cross section (RCS) is computed, thereby, the research can benefit to the future work.4. Based on the research above, parameters of the structural model in the millimeter wave band are designed, and then the associate model is analyzed with FDTD. The numerical results presented validate the feasibility of extending the bluffer wing model to millimeter wave band, so some initial works are done with the goal of absorbing material designation in the millimeter wave band for our country.The configuration of wings of butterfly have two characteristics as follows: 1) it only reflect blue light and other lights can pass though the wings of butterfly, 2) the scattering filed in back direction is very weak, it is strengthened in other directions 30 degrees to 60 degrees away from the back. These two characteristics mentioned above are what we want in modern stolen techniques, it provides a new approach for the absorbing material designation.
引文
1. T.H.Hubing, "Survey of Numerical Electromagnetic Modeling Techniques" University of Missouri-Rolla EMC Laboratory, Sep, 1991
2. K.S.Yee, "Numerical solution of initial boundary value problems involving Maxwell's equations in isotropic media," IEEE Trans. Antennas Propagant.,May 1966, AP-14(3), P302-307
3. R.F.Harrington, "Field Computation by Moment Methods[M]", IEEE PRESS
4. H.C.Martin and G..F.Carey. Introduction to finite element analysis:theory and application. New York, McGraw-Hill,1973
5. Vukusic, P.,Sambles J. R.,Lawrence C.R.& Wootton, R, J. "Quantified interference and diffraction in single Morpho butterfly scales," Proc. R. soc. Lond. B 26. 1999, p. 1403-1411
6. Vukusic. P., Sambles. J. R, & Ghiradella. H. "Optical classification of microstructure in butterfly wing-scales," Photonics Science News 6, 2000 p.61-68
7. Cowan, J, J. "Aztec surface-relief volume diffractive structure," J.Opt.Soc.Am.A 7, p.1529-1544, 1990
8.姚启钧 “光学教程[M]”,高等教育出版社
9.郁道银 谈恒英 “工程光学[M]”,机械工业出版社
10. Luca Plattner, "Optical properties of the scales of Morpho Rhetenor butterflies: theoretical and experimental investigation of the back-scattering of light in the visible spectrum," J. R. Soc. Lon
11. Fung A K,Shah M R and Tjuatja S. Numerical simulation of scattering from three-dimensional randomly rough surfaces. IEEE Trans. Geosci. Remote Sensing, Sept. 1994,GRS-32(5):986～994
12. Chen M F and Bai S Y .Computer simulation of wave scattering from a dielectric random surface in two dimension-cylindrical case. J. Electromagn. Wave Appl. , 1990,4(10):963～982
2. K.S.Yee, "Numerical solution of initial boundary value problems involving Maxwell's equations in isotropic media," IEEE Trans. Antennas Propagant.,May 1966, AP-14(3), P302-307
3. R.F.Harrington, "Field Computation by Moment Methods[M]", IEEE PRESS
4. H.C.Martin and G..F.Carey. Introduction to finite element analysis:theory and application. New York, McGraw-Hill,1973
5. Vukusic, P.,Sambles J. R.,Lawrence C.R.& Wootton, R, J. "Quantified interference and diffraction in single Morpho butterfly scales," Proc. R. soc. Lond. B 26. 1999, p. 1403-1411
6. Vukusic. P., Sambles. J. R, & Ghiradella. H. "Optical classification of microstructure in butterfly wing-scales," Photonics Science News 6, 2000 p.61-68
7. Cowan, J, J. "Aztec surface-relief volume diffractive structure," J.Opt.Soc.Am.A 7, p.1529-1544, 1990
8.姚启钧 “光学教程[M]”,高等教育出版社
9.郁道银 谈恒英 “工程光学[M]”,机械工业出版社
10. Luca Plattner, "Optical properties of the scales of Morpho Rhetenor butterflies: theoretical and experimental investigation of the back-scattering of light in the visible spectrum," J. R. Soc. Lon
11. Fung A K,Shah M R and Tjuatja S. Numerical simulation of scattering from three-dimensional randomly rough surfaces. IEEE Trans. Geosci. Remote Sensing, Sept. 1994,GRS-32(5):986～994
12. Chen M F and Bai S Y .Computer simulation of wave scattering from a dielectric random surface in two dimension-cylindrical case. J. Electromagn. Wave Appl. , 1990,4(10):963～982
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