Microfabricated artificial ommatidia using a coherent UV light based self-writing process

Abstract

A compound eye in nature consists of thousands of individual integrated photoreception units called ommatidia which are spherically arranged along a curvilinear surface and aim at slightly different directions. Individual ommatidium gathers light within a small acceptance angle then ommatidia make a full mosaic image with a wide field of view. To mimic its remarkable advantage with respect to imaging optics, an artificially microfabricated compound eye lens, compatible to a natural compound eye was demonstrated by K. Jeong et al in 2006. It is composed of about 8,400 artificial ommatidium as a single integrated optic unit with spherical arrangement. Each consists of a self-aligned microlens and waveguide by virtue of a light induced self-writing process in a photosensitive polymer resin. From the engineering point of view, the increase of the waveguide length is an indispensible prerequisite for obtaining high resolution images through an artificial compound eye for wide field-of-view imaging and fast motion detection but in the previous work, the length of waveguide is limited to 150~300μm, which is not enough to realize high resolution imaging. In this work, a coherent light based self-writing process was implemented to increase a waveguide length and demonstrated to be an efficient way of increasing the waveguide length over 500μm in an artificial ommatidium. Theoretical backgrounds for increasing waveguide length when using a coherent light, i.e. laser as a light source for a self-writing were studied with respect to the coherence of light source compared with a broadband bulb light. A microelns-assisted self-writing process with a UV sensitive polymer (SU-8) model was studied with the numerical analysis based on beam propagation method. F-number effects of microlens and dose effects for self-writing were analyzed. Microfabricated artificial ommatidia were developed with photosensitive polymer based microlnes arrays and a coherent light based self-w...