7,078 research outputs found
Study of a MEMS-based Shack-Hartmann wavefront sensor with adjustable pupil sampling for astronomical adaptive optics
We introduce a Shack-Hartmann wavefront sensor for adaptive optics that enables dynamic control of the spatial sampling of an incoming wavefront using a segmented mirror microelectrical mechanical systems (MEMS) device. Unlike a conventional lenslet array, subapertures are defined by either segments or groups of segments of a mirror array, with the ability to change spatial pupil sampling arbitrarily by redefining the segment grouping. Control over the spatial sampling of the wavefront allows for the minimization of wavefront reconstruction error for different intensities of guide source and different atmospheric conditions, which in turn maximizes an adaptive optics system's delivered Strehl ratio. Requirements for the MEMS devices needed in this Shack-Hartmann wavefront sensor are also presented
Microelectromechanical system gravimeters as a new tool for gravity imaging
A microelectromechanical system (MEMS) gravimeter has been manufactured with a sensitivity of 40 ppb in an integration time of 1âs. This sensor has been used to measure the Earth tides: the elastic deformation of the globe due to tidal forces. No such measurement has been demonstrated before now with a MEMS gravimeter. Since this measurement, the gravimeter has been miniaturized and tested in the field. Measurements of the free-air and Bouguer effects have been demonstrated by monitoring the change in gravitational acceleration measured while going up and down a lift shaft of 20.7âm, and up and down a local hill of 275âm. These tests demonstrate that the device has the potential to be a useful field-portable instrument. The development of an even smaller device is underway, with a total package size similar to that of a smartphone
Design of ultraprecision machine tools with application to manufacturing of miniature and micro components
Currently the underlying necessities for predictability, producibility and productivity remain big issues in ultraprecision machining of miniature/microproducts. The demand on rapid and economic fabrication of miniature/microproducts with complex shapes has also made new challenges for ultraprecision machine tool design. In this paper the design for an ultraprecision machine tool is introduced by describing its key machine elements and machine tool design procedures. The focus is on the review and assessment of the state-of-the-art ultraprecision machining tools. It also illustrates the application promise of miniature/microproducts. The trends on machine tool development, tooling, workpiece material and machining processes are pointed out
MOEMS deformable mirror testing in cryo for future optical instrumentation
MOEMS Deformable Mirrors (DM) are key components for next generation
instruments with innovative adaptive optics systems, in existing telescopes and
in the future ELTs. These DMs must perform at room temperature as well as in
cryogenic and vacuum environment. Ideally, the MOEMS-DMs must be designed to
operate in such environment. We present some major rules for designing /
operating DMs in cryo and vacuum. We chose to use interferometry for the full
characterization of these devices, including surface quality measurement in
static and dynamical modes, at ambient and in vacuum/cryo. Thanks to our
previous set-up developments, we placed a compact cryo-vacuum chamber designed
for reaching 10-6 mbar and 160K, in front of our custom Michelson
interferometer, able to measure performances of the DM at actuator/segment
level as well as whole mirror level, with a lateral resolution of 2{\mu}m and a
sub-nanometric z-resolution. Using this interferometric bench, we tested the
Iris AO PTT111 DM: this unique and robust design uses an array of single
crystalline silicon hexagonal mirrors with a pitch of 606{\mu}m, able to move
in tip, tilt and piston with strokes from 5 to 7{\mu}m, and tilt angle in the
range of +/-5mrad. They exhibit typically an open-loop flat surface figure as
good as <20nm rms. A specific mount including electronic and opto-mechanical
interfaces has been designed for fitting in the test chamber. Segment
deformation, mirror shaping, open-loop operation are tested at room and cryo
temperature and results are compared. The device could be operated successfully
at 160K. An additional, mainly focus-like, 500 nm deformation is measured at
160K; we were able to recover the best flat in cryo by correcting the focus and
local tip-tilts on some segments. Tests on DM with different mirror thicknesses
(25{\mu}m and 50{\mu}m) and different coatings (silver and gold) are currently
under way.Comment: 11 pages, 12 Figure
Generalized Parity-Time Symmetry Condition for Enhanced Sensor Telemetry
Wireless sensors based on micro-machined tunable resonators are important in
a variety of applications, ranging from medical diagnosis to industrial and
environmental monitoring.The sensitivity of these devices is, however, often
limited by their low quality (Q) factor.Here, we introduce the concept of
isospectral party time reciprocal scaling (PTX) symmetry and show that it can
be used to build a new family of radiofrequency wireless microsensors
exhibiting ultrasensitive responses and ultrahigh resolution, which are well
beyond the limitations of conventional passive sensors. We show theoretically,
and demonstrate experimentally using microelectromechanical based wireless
pressure sensors, that PTXsymmetric electronic systems share the same
eigenfrequencies as their parity time (PT)-symmetric counterparts, but
crucially have different circuit profiles and eigenmodes. This simplifies the
electronic circuit design and enables further enhancements to the extrinsic Q
factor of the sensors
Micro-manufacturing : research, technology outcomes and development issues
Besides continuing effort in developing MEMS-based manufacturing techniques, latest effort in Micro-manufacturing is also in Non-MEMS-based manufacturing. Research and technological development (RTD) in this field is encouraged by the increased demand on micro-components as well as promised development in the scaling down of the traditional macro-manufacturing processes for micro-length-scale manufacturing. This paper highlights some EU funded research activities in micro/nano-manufacturing, and gives examples of the latest development in micro-manufacturing methods/techniques, process chains, hybrid-processes, manufacturing equipment and supporting technologies/device, etc., which is followed by a summary of the achievements of the EU MASMICRO project. Finally, concluding remarks are given, which raise several issues concerning further development in micro-manufacturing
Sagnac loop in ring resonators for tunable optical filters
General filter architecture using co- and counterpropagation signals are studied. A specific configuration based on a Sagnac loop within a ring resonator is analyzed. Novel tuning, apart from conventional tuning, is achieved by changing the coupling ratio of a coupler through the adjustment of the equivalent loop length. Full equations describing the filter behavior in passive and active configurations, and simple closed-form formulas to compute the tuning, tolerance, and full-width at half-maximum are reported. The performance of these devices is discussed for their application as selective or channel-dropping ultra-narrow-band filters. The effect of losses and their dispersion properties are also discussed. These devices can be conveniently implemented, using silicon- or InP-integrated optic technology, for they have high free spectral ranges.Publicad
- âŠ