Pixelated polarizer array can be used in the real-time measurement of Stokes parameters. In this paper, pixelated polarizer array based on the aluminum nano-grating is designed and fabricated, and the fabrication technology is electron beam exposure technology. The size of each unit is 7.4 μm, and the polarization directions of each adjacent 2×2 units in the polarizer array are 0, π/4, π/2, and 3π/4. The period, duty cycle, depth and surface type of the grating are 140 nm, 0.5, 100 nm and rectangle type, respectively. The scanning electron micrographs of the pixelated polarizer array show that there is no disconnection, cross and pollution on the fabricated metal nano-grating lines. The nano-grating lines are straight and uniform in thickness, and the surface type of the grating is ideal rectangular type. The polarization optical micrographs show that the pixelated polarizer array has good polarization characteristics. The maximum polarization transmissivity can reach 79.3%, and the extinction ratio can arrive at 454. Furthermore, the pixelated polarizer array is integrated with the charge coupled devise chip, and the Stokes parameters can be calculated from one frame, then the degree of linear polarization and angle of linear polarization can be obtained. Thus, the polarization enhancement of image is achieved, which can be used in the anti-stealth and recognition.
Based on thermal deformation of bi-material microcantilever, the focal plane array (FPA)of uncooled optical readout infrared(IR) imaging system has undergone a development from substrate array to substrate-free array. The experimental imaging result and finite element method (FEM) analysis indicated that the substrate-free focal plane array (FPA) did not accord with the condition of constant frame temperature. This paper proposed a new theoretical model on thermal transmission of substrate-free FPA with electrical analogy method. Considering the system as a whole, the analysis of complex thermal interaction of adjacent elements could be averted while the heat absorption and transmission of frame could be considered. The temperature of outer frame was set to be equal to the ambient temperature as a boundary condition. Although it was not so flexible compared with FEM analysis when dealing with the boundary condition, the theoretical model was proved to correspond with the experimental result, and could be used as an approximate formula in thermal response calculation of substrate-free FPA. The model avoids the complication of FEM analysis, especially for large arrays. Further more, the model can be used for substrate-free FPA dimensions design and optimization under certain response target.
In the theoretical analysis of the optical readout IR imaging, the incoherent area light source with a certain size is typically simplified into an ideal point light source, which leads to analytical errors. In this paper an area light source model is established, and using the Fraunhofer diffraction theory the influence of the optical detection sensitivity on area light source is studied. The dependence of the optical detection sensitivity on light source radius and reflector length of the focal plane array is found. And optimized design criteria for the size of light source and the length of the reflector are proposed. According to theoretical analysis, the experimental verification is carried out, and the results are consistent with theoretical analyses.
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