Video rate terahertz imaging using Si-technology based micro-bolometer array/camera
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Video rate terahertz imaging using Si-technology based micro-bolometer array/camera Iwao Hosako 1 and Naoki Oda 2 1 Advanced ICT Research Institute, National Institute of Information and Communications Technology, 4-2-1 Nukuikita, Koganei, Tokyo 184-8795, Japan 2 NEC Guidance and Electro-Optics Division, 1-10, Nisshin-Cho, Fuchu, Tokyo 183-8501, Japan ABSTRACT Terahertz (THz) imaging technique has attracted much attention in recent years, because the technique can be applied to many application fields such as nondestructive analysis and imaging method through optically opaque materials. A THz real-time imaging equipment (Terahertz Camera) considered increasingly important in the future has been developed. We report a THz video rate imaging system consisting of a quantum-cascade laser (QCL) light source as a THz illuminator, and a Si-technology based un-cooled micro-bolometer focal-plane array (an infrared detector common in thermal cameras). We also describe two applications of our imaging system: stand-off imaging for search and rescue in a fire disaster, and label-free biomaterial detection. INTRODUCTION THz imaging is a powerful technique that exploits a nonionizing (i.e., safe) portion of the electromagnetic spectrum located between millimeter-waves (MMW) and the infrared (IR). Because of its nondestructive nature, THz imaging is applicable to many areas. For example, it has advantages over x-ray imaging for diagnosis of structural object consisting of soft materials (e.g., hybrid plastics, ceramics, and polymers, etc.) and can detect sketches underlying paintings. THz imaging applications for non-destructive testing, security screening, and biomedical diagnostics are expected to realize. Successful realization and dissemination of THz imaging depends on availability of high-performance and cost-effective focal plane array (FPA) detector technologies. The rapid growth of the imaging industry has relied on the continual evolution of modern silicon (Si) -based integrated circuits. Continuous feature scaling has led to increased pixel formats, integration with read-out circuit, lower cost, higher speed, and compactness, however, the spectral sensitivity of the Si-based imagers (e.g. Complementary Metal Oxide Semiconductor (CMOS) Image Sensor, Charge Coupled Device (CCD) Image Sensor, and Blocked Impurity Band (BIB) Image Sensor, etc.) are limited to visible and (e.g., from near to mid) infrared (IR) band. Meanwhile, the emergence of uncooled micro-bolometer imager based on Si-Micro Electric Mechanical System (MEMS) fabrication technique has opened new opportunities for mid-IR detection. The economies of scale, ready availability of cheap high-quality materials and ability to incorporate electronic functionality make those Si-based imagers attractive for a wide variety of visualizing applications. Approaches to realize THz-FPA by touching up the Si-based imager technology are the natural evolution of the development of THz imager. IMAGING
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A micro-bolometer FPA (320 x 240 elements) has the stru
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