使用色彩過濾優化PDLC固體光圈之取像

Abstract

本論文利用色彩過濾技術優化高分子分散型液晶(Polymer-Dispersed Liquid Crystal, PDLC)所造成的乳白色濾鏡效果，並將其影像結果與原圖影像結果進行比較與分析。 實驗中所使用的元件為多段式同心圓固體光圈，此光圈能代替傳統機械式光圈並應用於攝影上，而其製程上利用PET聚脂薄膜、PDLC、氧化銦錫(Indium Tin Oxide, ITO)導電玻璃並結合雷射雕刻技術與3D列印技術完成該光圈。PDLC在光圈中扮演調變的角色，當未施加電壓時，因為散射的現象，呈現乳白色不透明的狀態；當施加電壓時，液晶微滴的光軸受到電場影響而轉向，此時液晶的有效折射率n_0會與高分子聚合物折射率np匹配，呈現透明的狀態。而PDLC有利有弊，雖然能進行快速的調變，但也因為在拍攝上，有部分的散射光被相機的CMOS接收到，造成影像品質不好，因此利用色彩過濾影像，並以對比度、訊雜比、邊緣銳利度分析色彩過濾之影像前後的結果。實驗結果表明，深色過濾對於影像品質有較好的改善度。

In this thesis, we optimized the milky white filter effect obtained through Polymer-Dispersed Liquid Crystal (PDLC) by color filtering. And then we compared the images with the original ones. Within the investigation, a stepped-tuning PDLC aperture was used to replace the traditional mechanical aperture for photography. The diaphragm was done by using the PET film, PDLC, Indium Tin Oxide (ITO) conductive glass, and laser engraving technology and 3D printing technology were applied to the device. PDLC plays a tuning switch in the diaphragm. Without applying any voltage, PDLC will present in a milky white opaque state due to the results of scattering. Under AC bias, optical axes of liquid crystal molecules will be arranged along the direction of the electric field. Simultaneously, n_0 (refractive index of liquid crystal) and np (refractive index of polymer) will match, and it will lead PDLC to present in a transparent state. PDLC has its pros and cons, it is a suitable material for using as a tunable layer because of its fast response time, but the fact that part of the scattered light will be captured by the CMOS is inevitable, and it will result in poor image quality. Therefore, taking advantage of color filtering to improve the results, and then analyze the original images and the post-processing image with contrast, SNR, edge sharpness. The results show that dark color filtering improve greatly on image quality.