Design and fabrication of polymer based diffractive optical elements for laser illuminated rear and brake lights

摘要

Summary form only given. With the advancement of illumination technology in automotive industry, significant amount of interest has arisen for laser based light sources for both front and rear end. While numerous amount of work has been done to incorporate laser based illumination for front lights [1], less attention has been paid towards rear and brake lights. Use of lasers as sources of illumination allows utilization of diffractive optical elements (DOEs) which are smaller in size and diffract the incident light at larger angles as compared to their counterpart refractive optical elements.We present a simple and cost effective method to design and fabricate DOEs onto polymers for projection of incident light in a predefined intensity distribution. The fabricated DOE, i.e., combination of several grating structures, each grating structure diffracting incident light to contribute in the desired pattern are computed in MATLAB with the help of diffraction theory and coupled wave analysis [2]. Once the DOE design is complete, it is transferred to the photoresist coated on a silicon substrate to prepare a stamp with the help of a maskless lithographic optical setup employing digital mirror device and spatial light modulators for two dimensional and three dimensional structures, respectively. After patterning the structures onto the photoresist, the DOEs are coated with PDMS (Polydimethylsiloxane) for preparation of soft stamps and then transferred to the polymer PMMA (Polymethylmethacrylat) using a hot embossing system.