This paper reports a novel uncooled infrared FPA whose performance is comparable to the cooled FPA's in terms of noise parameters. FPA consist of bimaterial microcantilever structures that are designed to convert IR radiation energy into mechanical energy. Induced deflection by mechanical energy is detected by means of optical methods that measures sub nanometer thermally induced deflections. Analytical solutions are developed for calculating the figure of merits for the FPA. FEM simulations and the analytical solution agree well. Calculations show that for an FPA, NETD of <5mK is achievable in the 8-12 μm band. The design and optimization for the detectors are presented. The mechanical structure of pixels is designed such that it can be possible to form large array size FPA's. Microfabrication of the devices, which can be improved to improve the performance further, employs low cost standard MEMS processes.