(The) research of anodic aluminum oxide based IR emitter device application for IR scene projector

Abstract

Infrared scene projector is a system that evaluates the performance of infrared sensors in a safe and cost / time-efficient by generating virtual infrared rays in lab environment. IRSP has been developed since 1970, and several devices (DMD, laser diode, etc.) have been developed and used as an IR emission device of IRSP, but resistive array type has been shown to have the desired qualifications for infrared scene projection applications. The foremost requirement for the next generation of resistive array is higher operating speed, high temperature dynamic range, and larger array size. Several studies have been conducted for high-speed operation of resistive IR emitter arrays. By reducing the volume of the unnecessary area, there was a structural approach to the device, but there was a limitation in per-formance due to the fundamental physical property, and it was possible to increase the speed by about 30 ~ 40% by using the over-driving technique in terms of circuit. However, there is still a demand for emitter devices with higher operating speeds In this study, the research was carried out targeting the high-speed operation of the IR emitter device, and the AAO material with a porous structure was selected to improve the speed of the device and applied. Especially, Alumina has a high thermal conductivity among ceramics, so it has advantage of high-speed operation by de-crease the thermal time constant related to operation speed. If AAO is used as a constituent of the membrane, speed enhancement of the emitter device is expected. However, in order to apply a new material as a membrane component of an emitter device, mechanical properties and fabrication process set up are required. Especially, when the mechanical stability is not guaran-teed, the optical cavity between the reflect layer at the bottom of the device and the membrane is not formed due to the membrane deformation issue, so that normal infrared radiation is not occurring. Therefore, in order to use AAO as a membrane component of a floating structure, first, a thin film stress anal-ysis was performed. Based on the stress analysis, a layer design was carried out to form a flat membrane. Sub-sequently, the device was successfully fabricated after set up the fabrication process, and then the operating speed of the device was measured. As a result of the operation speed measurement, the AAO-based emitter de-vice has been confirmed to have a two times faster operation speed compared with the $Si_3N_4$ based device due to the high thermal conductivity of AAO. In addition, due to the effect of reducing the heat capacity with in-creasing porosity of AAO, a device with a rise time of 5 milliseconds (with an operating speed of 200 Hz) was fabricated. Therefore, if an AAO-based emitter device is applied to an IRSP, it will be possible to project higher levels of infrared images, including representing fast moving objects, because of its high operating speed.