Development of an Infrared Direct Viewer Based on a MEMS Focal Plane Array

Abstract

Microelectromechanical Systems (MEMS) technologies have allowed the development of novel, uncooled infrared imaging detectors consisting of arrays of bi-material structures that deflect linearly as a function of temperature associated with infrared radiation from a scene. An optical readout system can be used to measure the deformation of the structures based on reflected light, and offers several advantages over the microbolometer sensors that are currently in widespread use including the ability to sense each structure without the need for complex addressing and sensing circuitry in the array. This leads to lower production costs, easier scalability, and reduced conduction between the substrate and individual sensing elements. However, it has been shown that optical readout methods based on reflectometry suffer from the effects of low array uniformity and offer only a qualitative response. Our previous work has shown that live digital holography can be used to compensate for initial non-uniformity across a small subsection of a representative array of sensing elements, and interferometric techniques have been used to observe a responsivity of 1.5 nm/K along with an NEDT of 220 mK. The current work explores the use of unpowered interferometric techniques such as Nomarski differential interference and live phase holography to overcome the previously mentioned limitations of reflectometry based measurements in order to demonstrate the viability of creating an infrared direct viewer.