Bi-material mircocantilever array room-temperature IR imaging

Abstract

The uncooled IR thermal imaging technology with its wide applications in military, medical and industrial areas has been an active topic in international research. Thermal imaging based on optical readout bi-material microcantilever array is a new concept in methodology. In this paper, a new kind of bi-material micro-cantilever unit with multi-fold legs and interval gild structure is designed and its thermal and thermo-mechanical performance are analylized. A 100×100 microcantilever array is fabricated as a FPA (focal plane array), and by using this FPA, a thermal image of a room-temperature body (human body) is successfully detected. The NETD (noise-equivalent temperature difference) is about 200mK.The experimental results are well accordant with the thermal analysis of the microcantilever unit.

Optical sensitivity analysis of a bent micro reflector array in uncooled infrared imaging

“…The primary definition of optical sensitivity is based on the theory of Fraunhofer diffraction and can be expressed as [12][13][14] I θ = 2LN λ , where I is the CCD gray-level change, θ is the thermal-induced angle change of the reflector, L is the length of the reflector, N is the quantization level of the CCD, and λ(=0.5 μm) is the wavelength of the illumination light. Obviously, this definition is built on the hypothesis that the reflector is a flat one.…”

“…In order to solve these problems, a self-supported (substrate-free) multi-fold interval metallized leg (IML) structure (shown in figure 1(a)) of FPA is designed and fabricated by the author's group. With non-coherent lighting and optical readout method using knife edge filter, which eliminates the influence of the environment vibration, the thermal images of 200 • C targets were obtained in 2003 and the NETD is about 20 K [12], subsequently, thermal images of room temperature objects were obtained in 2005 [13,14] and the NETD is around 600 mK [15][16][17][18].…”

“…Recently, the author's group endeavored to diminish the pixel size and enhance the spatial resolution of the FPA for practical applications. The pixel sizes of fabricated FPAs are reduced from 200 μm [10][11][12][13][14][15][16], 120 μm [17][18][19] to 60 μm (a photograph is shown in figure 1(b)). Based on the primary definition of optical detection sensitivity [12][13][14], the sensitivity is severely compromised by the diminishing of the pixel size (that is, the length of the reflector).…”

“…The pixel sizes of fabricated FPAs are reduced from 200 μm [10][11][12][13][14][15][16], 120 μm [17][18][19] to 60 μm (a photograph is shown in figure 1(b)). Based on the primary definition of optical detection sensitivity [12][13][14], the sensitivity is severely compromised by the diminishing of the pixel size (that is, the length of the reflector). However, our previous experiments reveal that the sensitivity does not inevitably decrease with the diminishing of pixel size [12][13][14][15][16][17].…”

“…Based on the primary definition of optical detection sensitivity [12][13][14], the sensitivity is severely compromised by the diminishing of the pixel size (that is, the length of the reflector). However, our previous experiments reveal that the sensitivity does not inevitably decrease with the diminishing of pixel size [12][13][14][15][16][17]. In addition, Miao et al [17] analyze that the sensitivity decreases by 50% when the reflector of the 120 μm FPA has a deformation of λ/5 (λ is the wavelength of illumination light), which shows that the sensitivity is seriously influenced by the reflector bend, and Shi et al [20] analyze the performance of the FPA's structure and the relations between the optical sensitivity and geometry of the FPA's pixel.…”