Establishing a MOEMS process to realise microshutters for coded aperture imaging applications

Coded aperture imaging has been used for astronomical applications for several years. Typical implementations used a fixed mask pattern and are designed to operate in the X-Ray or gamma ray bands. Recently applications have emerged in the visible and infra red bands for low cost lens-less imaging systems and system studies have shown that considerable advantages in image resolution may accrue from the use of multiple different images of the same scene - requiring a reconfigurable mask. Previously reported work focused on realising such a mask to operate in the mid-IR band based on polysilicon micro-optoelectro-mechanical systems (MOEMS) technology and its integration with ASIC drive electronics using a tiled approach to scale to large format masks. The MOEMS chips employ interference effects to modulate incident light - achieved by tuning a large array of asymmetric Fabry-Perot optical cavities via an applied voltage using row/column addressing. In this paper we report on establishing the manufacturing process for such MOEMS microshutter chips in a commercial MEMS foundry, MEMSCAP - including the associated challenges in moving the technology out of the development laboratory into manufacturing. Small scale (7.3 x 7.3mm) and full size (22 x 22mm) MOEMS chips have been produced that are equivalent to those produced at QinetiQ. Optical and electrical testing has shown that these are suitable for integration into large format reconfigurable masks for coded aperture imaging applications.