A Liquid-Crystal Negative Lens with Multi-Ring Electrodes in Unequal Widths
Chao, Paul C.-P.
|關鍵字:||液晶透鏡;負型透鏡;不等寬度電極;liquid crystal lens;negative lens;unequal width electrodes|
|摘要:||本論文主軸為設計一新型之液晶負透鏡(LC negative lens)，使其可取代相機上之傳統負型透鏡。其電極之設計利用多圈不等寬度電極，彌補傳統餅型變焦液晶透鏡因孔徑過大，造成折射率分佈不若漸進式折射率透鏡(GRIN lens)完美之缺憾，使其折射率分佈更為接近負型漸進式折射率透鏡。此透鏡為對稱型之結構，用以產生對稱之電場分佈。在產生理想負型透鏡之折射率分佈情形下，電極寬度之設計，以最內圈電極所需供應給液晶之電壓對位置之斜率為參考斜率，利用不同位置之電壓對位置之斜率對參考之斜率比和電極寬度成反比之方式，於此論文中總共設計了八圈之電極，並應用於大孔徑5mm之透鏡上。設計之結果先以液晶模擬軟體DIMOS.2D模擬出等電位線與液晶轉動角度，再利用軟體MATLAB計算出折射率分佈，最後經由此折射率分佈推算出相對應之等效焦距。此外，也利用光追跡軟體TracePro做光強度分佈之模擬，用以模擬與比較設計之液晶負透鏡與理想之負型漸進式折射率透鏡於光強度分佈上之差異。而於電極製作之製程上，此論文中採用多層蝕刻之方式，用以避免電極產生破裂之情形，將可使電場分佈更為平順。最後，成功地製作出孔徑比傳統液晶透鏡大之多圈不等寬度之液晶負透鏡，並藉由量測干涉條紋計算出其等效焦距；製作之透鏡孔徑為5mm，最小等效焦距為-357.9mm，並可將其應用於相機上。|
This study is dedicated to design a liquid crystal (LC) negative lens with multi-ring electrodes in unequal widths, which is intended for a camera lens and with the aim to replace conventional negative lenses. In this study, using multi-ring electrodes in unequal width improves the refractive index distribution while the conventional LC negative lens with a pie-typed electrode performs as a non-gradient index lens in large aperture. The structure of the LC negative lens is symmetric for producing a symmetrical electric field. For producing gradient index distribution, using the slope of desired applied voltages versus radial position at the most inner electrode as slope of reference. The unequal widths are adopted and determined in inversely proportional to the ratios of the slopes of the desired applied voltages at varied radial positions and slope of reference. There are eight ring electrodes in the lens and the aperture of the designed LC negative lens is as large as 5mm. The equivalent potential lines and tilting angles of LCs are simulated by the software DIMOS.2D. Refractive index distribution is calculated by software MATLAB with data extracted from DIMOS.2D. The effective focal length is calculated by the fitted curves of refractive index distributions. In addition, light intensity distribution is simulated by software TracePro for comparing the difference between the designed LC negative lens and negative gradient index lens. Special structure and material are used to realize the designed LC lens. A new fabrication process in the wafer level to bury voltage bus lines is developed in order to smooth the generated electric field distribution. Finally, the proposed LC negative lens whose aperture larger than conventional LC lens has been fabricated, and then the effective focal length has been extracted by measuring interference pattern. The LC negative lens with 5mm aperture and -357.9mm effective focal length has been successfully fabricated, and then it could apply on cameras.