台灣藍鵲羽毛奈米結構與色彩之研究

Research on Nanostructure and Coloration of Formosan Blue Magpie (Urocissa caerulea)

姚淳颺(Chun-yang Yao)

指導教授 ： 李正中

國立中央大學/理學院/光電科學與工程學系/碩士(2014年)

摘要

本論文主要是探討台灣藍鵲身上藍色羽毛的成色機制，在不同角度下，觀察其藍色羽毛，發現在視角大於40度後，它的羽色會隨著視角變大，而越來越藍、越亮，這種現象即為結構色的特徵。此結構色是由入射光被羽支中的髓部角質，及空氣孔洞所形成的「海綿結構」所散射造成。
為了分析其散射的特性，我們利用穿透式顯微鏡，拍攝海綿結構的影像，經過傅氏轉換，由其功率頻譜圖的特徵，證明了看似雜亂無章的海綿結構，在空間中具有短程有序的特性。因此，此海綿結構造成的散射屬於同調性散射。
我們發現利用文獻中的方法，根據功率頻譜圖，預測此海綿結構反射率光譜的變化趨勢，有其缺漏之處；於是我們以此模型為基礎，分析海綿結構的方向性，並考慮此方向性，我們發現遠離羽枝頂點的海綿結構方向性較一致、干涉現象較明顯，印證了在肉眼觀察下觀測角度越大顏色越藍的現象，同時也解釋積分球量測的結果；最後我們提出一套新的分析方法，計算其反射率光譜的變化趨勢，最後成功地提升位置遠離羽枝頂點的海綿結構，其預測光譜趨勢的精準度。

關鍵字

台灣藍鵲 ； 仿生結構 ； 海綿結構 ； 傅氏分析

並列摘要

In this research, we study the coloration mechanism of the blue feather from the Formosa blue magpie (Urocissa caerulea). The color appearance is due to the scattering and interference between the air scatterers of the nanostructure in the feather barb which is called spongy structures. To prove the optical phenomenon induced by the spongy structures, we use Fourier analysis to resolve the distribution of these air holes. We have proved successfully that the distribution of the air holes in the feather barb have the characteristic of quasi-order or short range order and the optical theory in the spongy structures was based on coherent scattering.
Furthermore, we found that the spongy structures have the directionality aligned along the outline of the feather barbs. The quasi-order structures with directionality would enhance the interference between the reflections light. And these characteristic explain the strong blue color is emerged at high incidence larger than 40-degree.
Finally, we used the Fourier power spectrum to predict the reflectance of these structures. We provide a method to improve the accuracy of the predicted reflectance spectrum by analyzing the directional property of the strongest intensity in Fourier power spectrum. And this way truly improved the accuracy of the predicted reflectance spectrum of the spongy structures away from the top of the feather barb

參考文獻

[1] S. J. Wilson and M. C. Hutley, "The Optical Properties of 'Moth Eye' Antireflection Surfaces," Optica Acta: International Journal of Optics, vol. 29, pp. 993-1009, 1982.

[2] P. B. Clapham, M. C. Hutley, "Reduction of Lens Reflexion by the "Moth Eye" Principle," Nature, vol. 244, pp. 281-282, 1973.

[3] W. Barthlott, C. Neinhuis, "Purity of the sacred lotus, or escape from contamination in biological surfaces," Planta, vol. 202, pp. 1-8, 1997.

[4] A. Marmur, "The Lotus Effect: Superhydrophobicity and Metastability," Langmuir, vol. 20, pp. 3517-3519, 2004.

[6] Y. Li, Z. Lu, H. Yin, X. Yu, X. Liu, and J. Zi, "Structural origin of the brown color of barbules in male peacock tail feathers," Physical Review E, vol. 72, 2005.