Applicability of reactive ion etching to fabrication of micro-prism-array for dioptrics system

This study aims to develop a new lens system using an integrated arrangement of micro-prism-cell (MPC) and to obtain similar focusing performance as an optical lens. In this lens system, the respective prisms have different apex angle which is fabricated by precision processing. Further development of this system would make it possible to manufacture a multifocal lens in a small area, which leads to wide applications not only in optical devices, such as glasses and intraocular lenses, but also in pickup lenses for optical storage and so on. In this study, a new software was first developed to design a micro-prism-array (MPA), in which the apex angles of respective MPC were precisely computed. Based on the computed design, the photo-resist shape pattern was produced on trial by reactive ion etching (RIE). Then, the formation of a smooth prism slope was tried by using the resist mask whose shape was whittled away with an O₂ (oxygen) RIE. Then, as a preliminary experiment, the apex angle was experimentally optimized with varying the etching conditions. In the experiment, the size of each MPC was set to 10μm, and the formation of the MPC, which had different apex angles ranging from zero to about 15° was achieved by four process stages of the RIE. A good focusing performance of the manufactured MPA could be obtained despite a diffusion of light. Nevertheless, the performance is not yet up to the specified design, and there remain some problems to be solved in order to achieve precise focusing performance with the MPA.