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C 0.6 Ñ t, 0.4 E O Z 0.2 0 0 02 0.4 06 08 Ratio of gap to the wavelength go-)J8 Initial Gap (go) + gA/8ABSTRACT The thermal sensor system presented in this paper is based on the mechanical bending due to the incident IR radiation. A diffraction grating is embedded under each pixel to facilitate optical readout. Typically the first diffraction order is used to monitor the sub-micron mechanical displacement with sub-nanometer precision. In this work; two different optical readout systems based on diffraction gratings are analyzed.First setup employs a conventional 4f optical system. In this one-to-one imaging system, collimated light is propagated through a lens, filtered with an aperture and then imaged onto a CCD by a second lens.Second system is more compact to improve image quality and to reduce noise. This is achieved by using an off-axis converging laser beam illumination that forms the Fourier plane near the imaging lens. This approach has important advantages such as reducing number of optical components and minimizing the optical path. The system was optimized considering parameters such as laser converging angle, laser beam size at MEMS chip, and magnification of the imaging system.

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This paper reports a micro electro-mechanical system (MEMS) based sensor array integrated with CMOS-based optical readout. The integrated architecture has several unique features and reported here for the first time. MEMS devices are passive and there are no electrical connections to the MEMS sensor array. Thus the architecture is scalable to large array formats for parallel measurement applications and can even be made as a disposable cartridge in the future using self-aligning features. A CMOS-based readout integrated circuit (ROIC) is integrated to the MEMS chip. Via holes are defined on ROIC by customized post-processing to enable integrated optical readout.A diffraction grating interferometer-based optical readout is realized by pixel-level illumination of the MEMS chip through the via holes and by capturing the reflected light using a photodetector array on the CMOS chip.