We propose a structured light micro-opto electromechanical system (MOEMS) projector specially designed to display successively a set of patterns in order to extract the 3-D shape of an object using a CCD cameras module and a small ARM-based computer for control, registration and numerical analysis. This method consists in a temporal codification using a modified Gray code combined with a classical phase shifting technique. Our approach is to combine the unambiguous and robust codification of the Gray code method with the high resolution of the phase shifting method to result in highly accurate 3D reconstructions. The proposed MOEMS is based on an array of vertical-cavity surfaceemitting laser (VCSEL) combined with two planar static diffractive optical elements (DOEs) arrays. DOEs masters on quartz substrate have been fabricated using photolithography therefore replication in polycarbonate is possible at low cost. The first DOE array is designed to collimate the VCSEL light (Fresnel-type element) and the second one to project the codification patterns. DOEs have been designed and fabricated by surface etching to achieve a good diffraction efficiency using four phase levels. First we introduce the MEOMS principle and the features of the different components. We present the layout design of the DOEs and describe the issues related to the micro-fabrication process. An experimental study of the topography of the DOEs is presented and discussed. We then discuss fabrication aspects including the DOEs integration and packaging.
A new rigorous vector-based design and analysis approach of diffractive lenses is presented. It combines the use of two methods: the Finite-Difference Time-Domain for the study in the near field, and the Radiation Spectrum Method for the propagation in the far field. This approach is proposed to design and optimize effective medium cylindrical diffractive lenses for high efficiency structured light illumination systems. These lenses are realised with binary subwavelength features that cannot be designed using the standard scalar theory. Furthermore, because of their finite and high frequencies characteristics, such devices prevent the use of coupled wave theory. The proposed approach is presented to determine the angular tolerance in the cases of binary subwavelength cylindrical lenses by calculating the diffraction efficiency as a function of the incidence angle.
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