Abstract
Optical sensitivity is a major issue to improve the sensor responsivity and the spatial resolution of uncooled optomechanical focal plane arrays (FPA). The optical sensitivity is closely related to the mirror length and the undesired mirror deformation induced from the imbalanced residual stresses in different layers. In this paper, the influences of mirror length and deformation on the optical sensitivity are discussed by Fourier Optics. Theoretical analysis and experiments demonstrate that the optical sensitivity is seriously degraded by undesired mirror deformation, and that there exists an optimal mirror length which makes the optical sensitivity achieve its maximum under a certain mirror deformation. Based on the results, an optimized mirror configuration is presented to increase the optical sensitivity of substrate-free bi-material microcantilever array (SFBMA).
Highlights
Infrared (IR) imaging system plays a critical role both in military and civilian applications ranging from night vision, surveillance, fire detection to spectral imaging
Theoretical analysis and experiments demonstrate that the optical sensitivity is seriously degraded by undesired mirror deformation, and that there exists an optimal mirror length which makes the optical sensitivity achieve its maximum under a certain mirror deformation
A substrate-free bimaterial microcantilever array (SFBMA) containing 100×100 pixels was fabricated, and thermal images of room temperature objects were obtained with sensor responsivity 13 gray/K (Gray was considered as the unit of the digital number obtained from the CCD) and noise equivalent temperature difference (NETD) 650mK [17, 18]
Summary
Infrared (IR) imaging system plays a critical role both in military and civilian applications ranging from night vision, surveillance, fire detection to spectral imaging. The need for electrical interconnect to each pixel makes it hard to increase the thermal isolation, and leads to fabrication complexity, which has kept the cost prohibitively high for many commercial applications These problems could be solved by non-contact optical inspection methods such as optical lever method and interferometry method. What is deserved to note is that this method solved the low resolution and the susceptibility to environmental vibration successfully [14,15] Based on this optical method, we designed a FPA named substrate-free bimaterial microcantilever array (SFBMA) and obtained room temperature IR images [16,17,18,19]. The influences of mirror length and undesired deformation on the optical sensitivity are discussed by Fourier Optics, and the analysis is validated experimentally
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