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 surface-emitting
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.
Numerous approaches to seismic detection have been proposed. Usual methods to sense seismic vibrations use either
accelerometers to measure the ground acceleration or geophones based on electro-dynamic actuator velocimeters. In this
paper, we present the design and the development of a polarimetric transducer using a single-mode optical fiber for low
level and low frequency vibration measurements such as those encountered in seismology. Polarimetric sensors can be
optimized to have a reduced sensitivity to temperature. The mechanical part of our one-dimensional seismic sensor is
based on a spring-mass device. A small section of the fiber is squeezed between a substrate connected to the ground and
the sprung mass. The resulting force acts along a vertical direction onto a small section of the optical fiber. The elastooptic
effect induces stress birefringence which varies temporally with the frequency of the applied force. We used a
polarized and single-mode laser diode source to couple light in the fiber. The induced polarization modulation measured
at the output of the fiber gives information of the seismic signals. The physical model of the developed inertial
seismometer has been considered as a mass-and-spring system with viscous damping. Firstly, we expose the principle
behind our optical fiber seismic sensor. Next, we computed the dynamic characteristics of the seismic sensor. Physical
simulation results obtained using the analytical model are presented and discussed. Finally, we present experimental
results measured with our seismic fiber sensor. Both model and experimental results demonstrate the potential of the
sensor for low level and low frequency vibrations characterization.
We present a simple concept for a low-cost pressure transducer. The transducer is a polarimetric device consisting
of a pressure sensitive dielectric material in-between polarizing optics. The pressure on the sensitive material
creates a stress-induced birefringence which is detected through a change in state of polarization. We show the
theoretical behaviour of this device and the various ways of optimizing its sensitivity.