In this paper, a high resolution Vernier-type displacement sensing mechanism is proposed by utilizing Vernier-type suspended gate field-effect transistors (SGFETs), The field-effect transistor benefits from its linear output signal and simple structure, and the concept of Vernier gate is used to enhance the resolution. The displacement of the comb-drive actuator is sensed via the output drain current of SGFET. Design and analysis for Vernier-type suspended gate were presented and some characteristics of the Vernier-type SGFETs were also discussed in simulation results.
We proposed and demonstrated an optical system for high-speed and high-resolution imaging of surface profiles. The
system is a fiber-based composite interferometer in which a Michelson interferometer is used for the measurement of the
surface profile of the sample and a Mach-Zehnder interferometer is used for compensation of phase deviation due to the
systematic errors and environmental perturbations. In the system, a laser diode with wavelength of 531 nm was used as
the light source. A two-axis translation stage was used for lateral scanning of the sample. In the reference arm, a
reflection mirror was arranged on a translation stage driven by a piezoelectric transducer as the axial scanning
component. The phase difference between the interferograms of both interferometers was acquired to obtain the surface
height of the sample. The axial accuracy of ±5 nm was achieved where the imaging was acquired within one minute for a
frame. The lateral resolution was at the diffraction limit of light. The system possesses the advantages of low cost,
portability and flexibility. Furthermore, it can perform
high-resolution imaging in large area without special shielding of
the system as well as any special preparation of the sample.
An in-plane rotary comb drive actuator was designed for variable optical attenuators (VOAs) that achieved large attenuation with fast response at low driving voltage. Actuator performance was improved by using a higher density of comb fingers for a smaller moment of inertia, serpentine flexure springs for a larger rotational angle, and symmetric spring arrangement for a higher radial shock resistance. A rotation of a tilted reflective mirror was used to further enhance the optical attenuation of VOA. The actuator, proposed with the size of 2 mm×2 mm, achieved the bandwidth of 350 Hz and the deflection angle of 2.5 deg at 5 V, resulting in the maximum attenuation of 57 dB.
One of the most interested aspects in the development of optical coherence tomography (OCT) is to construct a stable
and easy fabricated optical delay line that can perform real-time imaging for clinical applications. There are many
methods that have been used for fast scanning in OCT. However, most of the configurations are difficult to construct or
variational intensity loss exists during the scanning because of the walk-off of different wavelength components and
different tilted angle of the scanner. We proposed and constructed an optical delay line with all reflective components
that is compact, easy to fabricate and can avoid the intensity loss during the scanning. The optical delay line was
constructed of a retro-reflector fabricated with two right-angled prisms assembled on an aluminum jig, a reflection
mirror and a galvoscanner. The size of the optical delay line is within 2 cm x 2 cm and the system can provide a scanning
rate in the kilohertz range. The achieved imaging depth is 3.3 mm when the vibration angle of the scanning mirror is ±9°.
This system can perform a real-time scanning and thus is supposed suitable for clinical applications.
Micro-Rings have been widely used for measurement of residual tensile stress in thin films. This measurement approach provides a simple and convenient way to estimate the stress. However, it still lacks accuracy compared to other methods. In this study, we propose an alternative design, which arranges the central beam in the vertical orientation, shrinks the beam width, and widens the ring width to limit the undesired out-of-plane deformation of the ring portion and thus to improve the measurement results. The simulation result both has verified our design. The ring portion of conventional micro-ring is easily deformed in the out-of-plane direction when subjected to residual stress. In our design, such undesired out-of-plane buckling can be effectively prevented. Some suggestions for limiting the undesired out-of-plane deformation have been proposed. Following these suggestions, the more precise critical buckling length and the more accurate stress measurement will be obtained.
A surface-micromachined focusing mirror with variable focal length, which is controlled by adjusting the mirror’s curvature, is fabricated and characterized. The bowl-shaped micromirror, which is fabricated from the micro bilayer circular plate, focuses light beam through thermal actuation of the external heat source. Both the initial and operational curvatures are manipulated by the residual stresses in two layers of the mirror. Improper stresses would lead to the failure of the bowl-shaped structure. We analyze and design geometrical dimensions for simultaneously avoiding the structure failure and increasing the tuning range of the focal length. The interferometer has been used to measure the focal length and the focusing ability. Mirrors with nominal focal lengths approximately 730 μm, and tuning ranges of about 50 microns were demonstrated. The measurement directly through optical approach has also been tried, but requires further investigation, because the laser beam affects the focusing of the micromirror seriously.
KEYWORDS: Micromirrors, Finite element methods, Shape analysis, Mirrors, Reflection, Solids, Ray tracing, 3D modeling, Computer simulations, Microopto electromechanical systems
In this paper, we analyze the shape of the cylindrical micromirror, which directly defines the profile of the reflecting surface, and is very important for the function on focusing. A cylindrical micromirror can converge incident rays to a real focal line after reflection, namely angular focusing. Therefore, under specific design two cylindrical micromirrors, the primary and secondary, can converge incident rays into a real focal point after twice reflection. The curved shape of micromirror, formed due to the stress-induced bending of the bilayer microstructure upon release, has been theoretically analyzed and numerically simulated. The results show that the reflecting surface, especially at boundaries, is not perfectly cylindrical, while adding longitudinal frames can make some improvement.
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