微光學液晶元件於裸眼式立體顯示器之應用研究

Abstract

近年來，為了得到更真實的影像，已有許多專家及廠商投入裸眼式立體顯示器的研究。目前多數裸眼式立體顯示器皆使用固定式光學元件作為分光元件，但此種顯示器僅能提供三維立體影像，無法提供傳統高畫質二維影像。此外，目前多數裸眼式立體顯示器僅能顯示低解析度三維立體影像也為一大缺點。因此，開發次世代可二維/三維切換顯示，且具備顯示高畫質二維/三維影像顯示器的發展便為本論文研究之課題。 在諸多光學元件中，可電控式液晶透鏡具有電控變焦及體積小等優點，同時也可與現行面板製程相搭配製造，充分顯示其應用於裸眼式立體顯示器的優勢。因此，利用液晶透鏡取代傳統固定式光學元件，除了可預期得到可二維/三維切換顯示功能外，本論文更首次提出液晶透鏡也具有掃描(或是移動)的功能，藉由循序切換電控方式，液晶透鏡可表現出動態掃描的功能。將此動態掃描功能應用於立體顯示器研究上，利用時間多工補償空間多工所損失的資訊概念，預期可得到次世代高畫質三維影像顯示器。然而，液晶透鏡目前仍有許多問題，如反應速度過慢、驅動電壓高、較差的光學品質等等問題，都大大影響到液晶透鏡應用於立體顯示器之實用性。 本論文首先針對液晶透鏡的問題進行改善，進而將研發之液晶透鏡與面板搭配，最後做可二維/三維切換顯示功能及動態掃描高畫質立體顯示器之驗證。首先，我們針對液晶透鏡不易精準控制問題，提出一多電極控制液晶透鏡結構。藉由多電極之高控制自由度，可有效控制液晶層分布，提升透鏡聚焦品質(光分布面積較傳統液晶透鏡小約35%)。在此階段也改善操作電壓需求(較傳統液晶透鏡約小50%)，以及三維影像互擾問題(較傳統液晶透鏡約少60%)。第二階段部分，我們更提出雙向過電壓驅動方式，可有效減少傳統厚液晶透鏡反應速度過慢問題，可將其反應時間大幅減少約75% (超過10秒降至約2秒)。我們更進一步提出突破性的多電極菲涅爾液晶透鏡，在此架構下，液晶層厚度可被有效降低達到快速反應目的。而操作電壓5伏特也遠低於傳統多電極液晶透鏡的30伏特。藉由實作驗證，多電極菲涅爾液晶透鏡可在低於1秒的時間內快速有效聚焦；若搭配前述過電壓驅動方式，反應時間可大大再減低至僅0.2秒，並且也展示出初步可掃描液晶透鏡結果，此對液晶透鏡研究領域為一大發展。 最後，我們將提出之多電極菲涅爾液晶透鏡陣列實現於4吋及7吋的裸眼式立體顯示器上，實現可快速二維/三維切換顯示功能，以及驗證動態掃描液晶透鏡概念確實可有效補償因空間多工而損失之影像資訊，達到未來高畫質立體顯示器之成果。相較於之前研究課題，本論文最大特點為首次提出液晶透鏡不僅具可調控焦距功能，也可表現出動態掃描(移動)之功能。此動態掃描功能預期可被使用於多項應用，本論文則進一步將此動態掃描透鏡概念應用於改善三維立體顯示器影像品質的初期研究。

Since current high image quality displays are still two-dimensional (2D) displays, they cannot reproduce the images as real as the three-dimensional (3D) world. Thus, the advanced three-dimensional displays which can reconstruct the 3D scene from displays have been regarded as a critical technology for next generation displays. Many researchers have realized this interesting topic and have invested in developing 3D display technologies. The conventional auto-stereoscopic 3D displays utilize the fixed optical components to display 3D images that the displays cannot display the normal high quality 2D image. In addition, the current glasses-free 3D displays also suffer from the 3D image degradation issue. Therefore, developing the next generation 3D displays which can provide 2D/3D switchable function and high quality 3D image become the main subject in this dissertation. The Liquid Crystal Lens (LCLs) has unique features such as electronically tunable focal lengths without mechanical movement, as well as its compact volume. Moreover, the LCLs also has high potential for integrated manufacturing with current LCD industries. In this dissertation, we first propose that the LCLs not only performs the switch on/off function, it also performs the dynamic scanning function. Therefore, the LCLs could be a candidate for 3D applications, such as the 2D/3D switchable displays, and the temporal switching 3D displays. Nevertheless, the inferior optical performance, high driving voltage, and slow response of current LCLs make this device an impractical device for commercialization. In this dissertation, we first proposed the Multi-electrode Driving Liquid Crystal Lens (MeDLCLs), which can provide highly controlling-freedom in LCs distribution. Based on this proposed structure, the optical property of MeDLCLs could be improved (beam size reduced by 35% compare to conventional LCLs). Besides, the driving voltage and 3D crosstalk were also reduced by 50% and 60%, respectively. Second, we proposed the dual-directional overdriving method to reduce the response time of the thick LCLs by 75%. Following, we further proposed the superzone Fresnel LC lens (SFLCLs) in order to much more reduce the lens’ response time. Because the SFLCLs cell gap could be effectively reduced, that the response time of the SFLCLs finally could be decreased to 0.2sec with the overdriving method. In addition, the driving voltage of the SFLCLs was also suppressed to only 5 Vrms. We had also demonstrated the preliminary results on the first proposed fast scanning SFLCLs. Consequently, we not only dramatically improved the performance for the LCLs, but also broke though the current researches. Finally, this dissertation successfully established the fast response LCLs array on the 3D displays to demonstrate the fast 2D/3D switchable function, and to verify the most interesting topic, the temporally switching LCLs array technique for compensating the lost 3D image resolution of a spatial-multiplexed 3D display in a time-multiplexed manner. To the best of our knowledge, this is the first study on the temporally scanning LCLs technique and using this technique to approach future high quality 3D display.