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Proceedings Paper

Novel far infrared imaging sensor based on the use of titanium-nickel shape memory alloys
Author(s): Ho-Pui Ho; Jonathan Chi Yuen Chung; Ki-Cheong Ng; K. L. Cheng; Shu-Yuen Wu
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Paper Abstract

In this paper we describe a novel imaging sensor design1 that uses the thermo-mechanical properties of nickel-titanium (NiTi) shape memory alloys (SMAs) for detecting far infrared radiation (FIR). A thin NiTi SMA cantilever is coated with a FIR absorbing layer on one surface, while the other is coated with a highly reflecting metallic layers such as gold. Upon absorption of FIR, the temperature of the cantilever changes. This causes the tilt angle of the cantilever to change as well. The deflection is very large if the temperature change coincides with the temperature range of the phase transformation of the NiTi SMA. The detection of the mechanical movements in the cantilever is achieved by illuminating the reflective side using a visible laser beam. A Michelson interferometer is used to covert the reflected light into optical modulation. In doing this, very small displacement in the cantilever can be visualized as laser intensity variation. A single element device has been fabricated for this purpose and our initial experimental results have demonstrated the successful detection of FIR. An estimation of angular deflection per unit change of temperature suggests that our approach can offer sensitivity higher than the reported design based on the use of bi-material strips. We envisage that a two-dimensional array of such devices can lead to the possibility of realizing a practical low-cost infrared imaging device operating under room temperature conditions.

Paper Details

Date Published: 14 November 2002
PDF: 5 pages
Proc. SPIE 4935, Smart Structures, Devices, and Systems, (14 November 2002); doi: 10.1117/12.469087
Show Author Affiliations
Ho-Pui Ho, Chinese Univ. of Hong Kong (China)
Jonathan Chi Yuen Chung, City Univ. of Hong Kong (China)
Ki-Cheong Ng, City Univ. of Hong Kong (China)
K. L. Cheng, City Univ. of Hong Kong (China)
Shu-Yuen Wu, City Univ. of Hong Kong (China)

Published in SPIE Proceedings Vol. 4935:
Smart Structures, Devices, and Systems
Erol C. Harvey; Derek Abbott; Vijay K. Varadan, Editor(s)

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