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系統識別號 U0026-1402202022230900
論文名稱(中文) 固定厚度之液晶分層結構對圓孔型電極液晶透鏡光電性能之影響
論文名稱(英文) Variously subdivided layers of a constant liquid crystal thickness affect electro-optical performance in the hole-patterned electrode liquid crystal lenses
校院名稱 成功大學
系所名稱(中) 光電科學與工程學系
系所名稱(英) Department of Photonics
學年度 108
學期 1
出版年 109
研究生(中文) 陳慶泓
研究生(英文) Ching-Hong Chen
學號 L76061252
學位類別 碩士
語文別 中文
論文頁數 64頁
口試委員 指導教授-許家榮
口試委員-黃啟炎
口試委員-鄭協昌
中文關鍵字 圓孔型電極  液晶分層透鏡  雙電壓驅動  不連續線抑制 
英文關鍵字 hole-patterned electrode  subdivided layers of liquid crystal lens  dual driving voltage  disclination line 
學科別分類
中文摘要 本論文主要探討在固定液晶層厚度條件下對其進行分層結構,以了解其對圓孔型電極液晶透鏡光電性能之影響,該透鏡是由上下玻璃基板與薄蓋玻片所構成之雙液晶層結構液晶盒,研究針對不同液晶層厚度比例進行實驗,包括雙電壓操作、透鏡焦距以及影像能力的評估。
液晶分層透鏡是利用圓孔型電極於兩液晶層中產生非均勻對稱電場以轉動液晶分子使其液晶分子分佈滿足適當的折射係數梯度分佈而具有調制入射光波前的能力達到匯聚或發散光束的效果。
實驗結果顯示在相同電壓下的非均勻電場分佈中,較厚的液晶層可使電場的平均水平分量下降,結果表明上層75 μm與下層25 μm搭配之液晶分層透鏡,明顯降低了抑制不連續線產生的垂直場臨界電壓值,同時增加了透鏡的調焦範圍,其成像的品質也相較於其他厚度比例的液晶分層透鏡優異。
英文摘要 SUMMARY
In this thesis, electro-optical performance of hole-patterned electrode liquid crystal lenses with a constant liquid crystal layer affected by variously subdivided layers was investigated. As a result, the experiment found that under the same non-uniform electric field distribution, the thicker liquid crystal layer reduces the average horizontal component of the electric field. As a result, it obviously reduces the threshold voltages of vertical electric field to effectively prevent disclination line occurrence when the LC lens with an upper layer of 75 μm and a lower layer of 25 μm. Meanwhile, the tunable focuses achieve larger increase and better imaging performance than others.

Key words: hole-patterned electrode, subdivided layers of liquid crystal lens, dual driving voltage, disclination line

INTRODUCTION
Although the stacked structure of liquid crystal layers brings many improvements to the liquid crystal lens, it also causes additional defects to lens, that is, the disclination lines at the short focal length. Due to the upper LC layer closing to the hole-patterned electrode, there is a larger electric field gradient. If we extend the upper LC layer to the bottom of lens for a short thickness, the average horizontal components of the electric field in the layer will be reduced to a certain extent. By restraining part of LC molecules from reversed rotating, we can prevent the occurrence of disclination lines, and the voltage controlling the vertical field also be operated with a lower value.
In this study, three type of LCLs fabricated with subdivided LC layers are demonstrated and evaluated their optical performance.

EXPERIMENTAL MATERIALS

Fig. 1 Cross-section view of the subdivided layers in a hole-patterned liquid crystal lens structure.

Figure 1 shows the cross-section view of the subdivided layers in a hole-patterned liquid crystal lens, which is composed of top glass substrate (0.55 mm thickness) and bottom glass substrate (1.1 mm thickness) with whole ITO films and the second substrate (0.55 mm thickness) is a hole-patterned (radius 3 mm) with aluminum film. There is a cover slip between upper and lower LC layers (filled with E7 LCs, purchased from ECHO CHEMICAL CO.). In this experiment, we fabricate three type of LCLs subdivided LC layers of a constant liquid crystal thickness (100μm). LCL (50-50) is the lens with 50 μm upper and lower layers. LCL (75-25) is the lens with 75 μm upper layer and 25 μm upper. The last one which is LCL (25-75) with 25 μm upper layer and 75 μm upper.

RESULT AND DISCUSSION
Figure 2 is shown comparisons of interference patterns at the beginning of disclination lines for three type of above LC lenses when we control the driving voltage V2 at 80 Vrms. As a result, we observe that a small area of disclination line starting to appear in the center of LCL(25-75) and LCL(50-50) when V1 operated to a value lower than the threshold voltage. This area will slowly spread as time goes on and eventually extend to both sides of the lens edge. However, there is the smaller average horizontal component of the electric field in the LCL(75-25), the threshold voltage of V1 can be operated at a lower value than the other two structures, as shown in Fig.2 (c).

Fig. 2 Comparisons of interference patterns at the beginning of disclination lines for three type of LC lenses when V2 at 80 Vrms. (a) LCL (25-75) with V1 at 30 Vrms (b) LCL (50-50) with V1 at 5 Vrms (c) LCL (75-25) with V1 at 0 Vrms.

Finally, various experimental parameters to affect the image performance of LCLs are evaluated which results are shown in Fig. 3. We control the three type lenses at the same focal length of 7cm. Black and white line pair imaging, it is obvious that the edge of LCL (75-25) is sharper than LCL (50-50) and single LC layer lens.

Fig. 3 Observation of imaging performance in three types of lenses (a) LCL (50-50) applied voltage V2=80 Vrms and V1=15 Vrms (b) LCL (75-25) applied voltage V2=80 Vrms and V1=0 Vrms (c) LCL with single LC layer applied voltage V2=80 Vrms and V1=10 Vrms (d) glass lens.

CONCLUSION
This study has demonstrated the stacked structure liquid crystal lens with thicker upper LC layer effectively reducing the average horizontal component of the electric field. It obviously reduces the threshold voltage of vertical field and restrain disclination line at the same time. The proposed LCL (75-25) with 40 Vrms operated by V2 obtained the focal length reduction effectively and good imaging quality is also maintained compared to another two LCLs.
論文目次 目錄
摘要 I
Abstract II
致謝 VI
目錄 VII
表目錄 X
圖目錄 XI
第一章 緒論 1
1.1 前言 1
1.2 研究動機 5
第二章 液晶材料與透鏡原理 6
2.1 液晶簡介 6
2.2 液晶分類 7
2.2.1 向列型液晶(Nematics) 8
2.2.2 層列型液晶(Smectics) 9
2.2.3 膽固醇型液晶(Cholesterics) 9
2.3 液晶的光學特性 9
2.3.1 秩序參數(Order parameter) 10
2.3.2 雙折射性(Birefringence)[11] 10
2.3.3 連續彈性體理論(The elastic continuum theory) [12] 12
2.3.4 電場對液晶分子的影響 13
2.4 液晶透鏡原理 14
2.4.1 圓孔型圖樣電極液晶透鏡 15
2.4.2 圓孔電極液晶透鏡之干涉條紋 16
2.4.3 圓孔電極液晶透鏡之不連續線成因 19
2.5 Quick MTF軟體影像分析原理[15-17] 21
第三章 實驗材料與裝置 23
3.1 液晶分層透鏡製作 23
3.1.1 實驗材料 23
3.1.2 圓孔圖樣電極液晶透鏡製作 25
3.1.3 液晶分層透鏡之雙電壓操作方式 30
3.2 實驗裝置架設 31
3.2.1 量測干涉條紋 32
3.2.2 量測焦距 35
3.2.3 成像拍攝 36
第四章 實驗結果與討論 38
4.1 液晶分層透鏡 38
4.1.1 液晶分層透鏡之干涉條紋 38
4.1.2 液晶分層透鏡之液晶層厚度對不連續線影響 43
4.1.3 液晶分層透鏡之波前誤差RMS分析 44
4.1.4 液晶分層透鏡之焦距量測比較 48
4.2 單液晶層透鏡 51
4.2.1 單液晶層透鏡之干涉條紋 51
4.2.2 單液晶層透鏡之波前誤差RMS分析與焦距量測 53
4.3 Quick MTF軟體進行影像評估 56
第五章 結論與未來展望 61
5.1 結論 61
5.2 未來展望 62
參考文獻 63
參考文獻 參考文獻
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[4]H. Ren, S. T. Wu, “Tunable electronic lens using a gradient polymer network liquid crystal,” Appl. Phys. Lett. 82,22-24. (2003)
[5]M. Ye and S. Sato, “Optical properties of liquid crystal lens of any size,” Jpn J Appl Phys. 41, 571-573. (2002)
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[8]T. Scharf, P. Kipfer, M. Bouvier And J. Grupp, “Diffraction limited liquid crystal microlenses with planar alignment,” Jpn. J. Appl. Phys, 39. P. 6629. (2000)
[9]松本正一、角田市良,“液晶之基礎與應用” 第八版,第四章,國立編譯館,民國94年
[10]D. K. Yang, S. T. Wu, “Fundamentals of Liquid Crystal Devices,” Chap. 1, John Wiley & Sons (2006)
[11]Toralf Scharf, “Polarized Ligh in Liquid Crystal and Polymers,” Chap. 6, John Wiley & Sons (2007)
[12]F. C. Frank, “On the theory of liquid crystals,” Faraday Soc, Volume 25. Number 19 (1958)
[13]張繼鴻,“發展一可用電壓調控焦距的液晶元件”,私立中原大學應用物理研究所碩士論文,中華民國92年
[14]A. Bagramtan, T. Galstian, “Dynamic control of polarization mismatch and coma aberrations in rod-GRIN assemblies,” Opt. Express, 10. 14144. (2019)
[15]Greer PB, van Doorn T. “Evaluation of an algorithm for the Assessment of the MTF using an edge method.” Med Phys. (2000)
[16]I. A. Cunningham and A. Fenster “A method for modulation transfer function determination from edge profiles with correction for finite-element differentiation,” Med Phys. 14, 533. (1987)
[17]M. Estribeau, P. Magnan, “Fast MTF measurement of CMOs imagers using ISO 12233 slantededge methodology,” Proc. SPIE, vol. 5251. pp. 243-252. (2004)
[18]Iam-Choon Khoo, “Liquid Crystals,” 2nd. Edition, Chap. 1, John Wiley & Sons (2007)
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