Sözak, Ahmet
Enhancement of image resolution has been one of the main interests in optical research for many years. In this context, many different methods have been developed. While some of these methods found use in the field, some remained at the level of laboratory demonstration. There have been numerous approaches to reduce the pixel size of staring focal plane array detectors since 1980, and the number of pixel on unit area and resolution are increased since then. However, the difficulty at the fabrication of small pixel pitch and limited fill-factor of the pixel structure of focal plane array are critical limitations of this method especially at the infrared wavelengths. Micro scanning the other method in order to obtain resolution enhancement has proven its applicability in the field. There are many variants of the application of this technique such as the scanning of lenses, mirrors, prisms and coded mask for resolution enhancement. The macro and micro actuators are utilized for scanning of optical components in different optical architectures. Conventional micro scanning systems for the infrared imaging have a size from 50mm range up to 200 mm, need a large space in optical system and consume high power and excitation voltage from 45V range up to 150 V due to bulky optical components and actuators. Also, the conventional micro scanning systems for infrared imaging have high part quantity and need to use separate compliance mechanism parts for the displacement amplification. The aim of this study is to develop a novel Micro-Opto-Electro-Mechanical System (MOEMS) with small size, large displacement and low power consumption for the stabilization and enhancement of the resolution of a real macro scale infrared imaging system. In this context, throughout this study a piezo electrical, a thermal and an electro-magnetic micro scanning system were designed and optimized by using CAD modeling and parametrical multi-physics finite element analysis with both PTC CREO and ANSYS. Optical architecture, ray tracing and lens designs were done by Zemax. Lumerical software tool were used for designing of the metalens. Silicon on Insulator (SOI) is chosen as the substrate of structure. Deep Reactive Ion and Wet Etching methods were applied to fabricate the integrated MOEMS actuator. Determining the optical architecture and components used for scanning are significant points of the study. A metalens and a coded mask, both of which can be produced by micro fabrication methods, were the optical payload of the actuator. For this purpose, a metalens consisting of nano-holes was designed as the first alternative. Secondly, a specific coded mask was designed and applied to the center of MOEMS structure for obtaining the spatial light modulation. To obtain the desired displacement for subpixel scanning, the excitation voltage of the thermal chevron actuator is 12V, which is %8- %27 of the bulk piezo ceramic actuator counter parts in literature. The best performance of the excitation voltage 10.2V was achieved with a thermal and electro-magnetic hybrid Micro-Opto-Electro-Mechanical System (MOEMS) based scanner by means of additional Lorentz force caused by magnetic field. Core size of MOEMS actuator is 19 mm, which is %10-%38 of macro actuator equivalents.


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Citation Formats
A. Sözak, “MICRO-SCANNING MIRRORS AND LENSES FOR IMPROVING IMAGE RESOLUTION,” Ph.D. - Doctoral Program, Middle East Technical University, 2022.