以石英為基片之二進階微透鏡的設計與製作

Abstract

二進階光學元件大部份被應用於微透鏡陣列或特殊的透鏡上；然而在這些二進階光學元件的設計與應用時，效率是其中最重要的考慮因素。為了得到很好的光學演示性能，通常都希望使其繞射結構能有最大的效率才行。而這些元件主要是利用超大型積體電路的製作技術來完成，且當我們採用標量繞射理論來分析時，這些光學元件所得到的理論效率非常高。然而此理論是基於幾個假設條件之基礎上才成立的，故有些情況下就不再適用了；另一方面由於在製程上最小線寬的技術限制，也會降低原本在物理之理論上所能達到的繞射效率。 在本論文中利用傳統的標量繞射理論來進行分析與討論，並提出如何在設計時考慮製作技術的限制，而又能獲得可能最大繞射效率的方法。文中並描述在石英基片上製作出傳統的八階與新的六階微透鏡陣列。光學量測本實驗所得到微透鏡之聚焦光點對六階結構為57μm、對八階結構為59μm。至於繞射效率的量測方法則需要更進一步的研究了。

Most of binary optical elements are used as microlens array or special lenses. However, the efficiency of binary optical elements is one of the most important considerations in their design and applications. To achieve good performance, usually it is desirable to maximize the efficiency of the diffractive structure. These elements fabricated with VLSI techniques normally have very high theoretical diffraction efficiencies, based on scalar diffraction theory. However, the scalar theory is based on several assumptions, which are invalid in some cases. The minimum feature size is also limited by the current fabrication technique, that reduces the achievable diffraction efficiency. In this thesis the diffractive micro-lens and its design were discussed and analyzed with the conventional scalar diffraction theory. A new design concept was proposed, in which the fabrication limitation is consided in the design and possible best diffraction efficiency could be gotten. Based on this idea, a six-level microlens was fabricated with quartz (fused silica) substrate. A conventional eight-level microlens was also fabricated. The spot sizes, 57μm for six-level and 59μm for eight-level were measured. But the method for the measurement of diffraction efficiency needs to be improved in feature.