Mirror Plate Research Articles

Design and thermal performances of Semi-Parabolic Linear Fresnel Reflector solar concentration collector

A Semi-Parabolic Linear Fresnel Reflector (SPLFR) solar concentrator is proposed in this paper. The SPLFR is formed by linear plate mirrors whose edges located at a parabolic line. The ray trace simulation results show the SPLFR has the same concentrating efficiency as that of the parabolic trough concentrator (PTC), but lower manufacture cost. The SPLFR concentrator has higher ground utilization ratio compared with that of Linear Fresnel Reflector (LFR) concentrator because it has no shading and blocking shortcomings. The SPLFR concentrated radiation distribution along the circumference of absorber pipe cross section is investigated and compared with that of LFR concentrator. The thermal performance of linear evacuated absorber for the SPLFR is simulated numerically as well. The nonuniform radiation distribution induces two convection eddies at each side of absorber pipe which enhances the heat transfer from the wall of absorber to the working fluid.

Fabrication and characterization of a piezoelectric micromirror using for optical data tracking of high-density storage

A micromirror actuated by three piezoelectric microcantilevers is presented for optical data tracking of high-density storage application. The microcantilevers are actuated by 2.5-μm-thick lead zirconate titanate (PZT) films which are deposited on the silicon-based substrate by a compatible sol–gel route. The X-ray diffraction result shows that the PZT film is perovskite structure and has a typical good ferroelectric loop. The quasi-static displacement of the mirror plate increases linearly with increasing the driving voltage and the tracking resolution on disk is as high as 8 nm/V. The micromirror also provides a high bandwidth of about 21 kHz, which is high enough to support the optical data tracking of future high-density storage.

Numerical Simulation of Influence of Oil Tank with Different Throat Areas on Mirror-Plate-Pump Performance

In order to study the influence of oil tank with different throat areas on mirror-plate-pump performance, numerical simulation by applying ANSYS CFX software was conducted between four oil tanks with different throat areas, which combined with the same mirror plate respectively. Contrastive analysis of external characteristics of different runner-pumps and energy losses in different oil tanks show that the change of throat area has little effect on the brake horsepower curve, but it has great influence on head and efficiency curve, both of which first move up and then decline with the decrease of throat area in the whole calculation flow range, and at the same time the change of throat area causes great change of losses in oil tank. Achieving the best match relationship between oil tank and mirror plate in design process can make mirror-plate-pump display the best performance.

Endoscopic swept-source optical coherence tomography based on a two-axis microelectromechanical system mirror

A microelectromechanical system (MEMS) mirror based endoscopic swept-source optical coherence tomography (SS-OCT) system that can perform three-dimensional (3-D) imaging at high speed is reported. The key component enabling 3-D endoscopic imaging is a two-axis MEMS scanning mirror which has a 0.8×0.8 mm2 mirror plate and a 1.6×1.4 mm2 device footprint. The diameter of the endoscopic probe is only 3.5 mm. The imaging rate of the SS-OCT system is 50 frames/s. OCT images of both human suspicious oral leukoplakia tissue and normal buccal mucosa were taken in vivo and compared. The OCT imaging result agrees well with the histopathological analysis.

Sub-5 nm hard x-ray point focusing by a combined Kirkpatrick-Baez mirror and multilayer zone plate

Compound optics such as lens systems can overcome the limitations concerning resolution, efficiency, or aberrations which fabrication constraints would impose on any single optical element. In this work we demonstrate unprecedented sub-5 nm point focusing of hard x-rays, based on the combination of a high gain Kirkpatrick-Baez (KB) mirror system and a high resolution W/Si multilayer zone plate (MZP) for ultra-short focal length f. The pre-focusing allows limiting the MZP radius to below 2 μm, compatible with the required 5 nm structure width and essentially unlimited aspect ratios, provided by enabling fabrication technology based on pulsed laser deposition (PLD) and focused ion beam (FIB).

Accurate integration of segmented x-ray optics using interfacing ribs

Future lightweight and long-focal-length x-ray telescopes must guarantee a good angular resolution (e.g., 5 arc sec HEW) and reach an unprecedented large effective area. This goal can be reached with the slumping of borosilicate glass sheets that allow the fabrication of lightweight and low-cost x-ray optical units (XOU). These XOUs, based on mirror segments, have to be assembled together to form complete multishell Wolter-I optics. The technology for the fabrication and the integration of these XOUs is under development in Europe, funded by European Space Agency, and led by the Brera Observatory (INAF-OAB). While the achievement of the required surface accuracy on the glass segments by means of a hot slumping technique is a challenging aspect, adequate attention must be given to the correct integration and coalignment of the mirror segments into the XOUs. To this aim, an innovative assembly concept has been investigated, based on glass reinforcing ribs. The ribs connect pairs of consecutive foils, stacked into a XOU, with both structural and functional roles, providing robust monolithic stacks of mirror plates. Moreover, this integration concept allows the correction of residual low-frequency errors still present on the mirror foil profile after slumping. We present the integration concept, the related error budget, and the results achieved so far with a semi-robotic integration machine especially designed and realized to assemble slumped glass foils into XOUs.

Heterogeneous 3D integration of hidden hinge micromirror arrays consisting of two layers of monocrystalline silicon

We present a complementary metal–oxide–semiconductor (CMOS) compatible heterogeneous 3D integration process that allows the integration of two monocrystalline silicon layers on top of CMOS control electronics. With this process we demonstrate the fabrication of hidden hinge micromirror arrays from monocrystalline silicon for adaptive optics applications. The piston-type micromirror arrays have the flexures underneath the mirror plates on separate silicon layers. Arrays of 48 × 48 mirror elements with an air-gap between mirror and address electrode of 10 µm were fabricated. The mirrors were found to be drift free and showed no imprinting. A maximum electrostatic mirror displacement of 3 µm is demonstrated.

Development of precision stage with magnified displacement system using multi reflection of optical sensor

For high-resolution positioning of a precision stage, conventional positioning systems require laser interferometers or capacitance displacement sensors to measure nanoscale displacements. These can be expensive and complicated. In this study, a new measuring system was developed using multi laser reflection and mechanical magnification of its displacement. The displacement of the stage was measured using a position-sensitive photodiode (PSPD), a laser diode (LD), a hinge-connected rotating mirror plate, and two reflection mirror plates. A beam from the laser diode was focused on the center of the rotating mirror. The beam was reflected onto one of the reflection mirrors, and underwent several reflections. The position variation of the reflected beam from the reflection mirrors was then measured by the PSPD. Using this magnified displacement system a measuring resolution of less than 5 nm was achieved.

Millimeter scale electrostatic mirror with sub-wavelength holes for terahertz wave scanning

This work reports the design, microfabrication, and characterization of highly reflective electrostatic mirrors with sub-wavelength holes for scanning terahertz (THz) waves. The mirror consists of an aluminum coated silicon mirror plate precisely assembled on the top of two axis torsional microactuators. The mirror plate with sub-wavelength microholes not only provides high reflectivity over 98% at THz waves by decoupling the surface plasmon resonance but also reduces air damping by allowing air to flow through the mirror plate during the mirror scanning. The device can provide many opportunities for miniaturized THz time domain spectroscopic imaging systems.

A resonance scanning grating based on SOI for microspectrometer application

A scanning grating is designed and fabricated as a significant dispersing component of a microspectrometer. The designed scanning grating utilizes the slight vertical comb offsets induced mainly by the fabrication imperfections and residual stress in silicon on insulator (SOI) as starting electrodes. According to the spectral resolution and resonance frequency requirements, the scanning grating structure parameters are determined. Based on an SOI substrate, a V-shaped grating structure (〈111〉 plane with an angle of 54.74° to the surface of a 〈100〉 silicon substrate) can be obtained by wet etching on the microscanning mirror plate (3 × 3 mm2). Some measuring principles and experimental results on the main performance of the scanning grating including the resonance frequency, deflection angle and diffraction efficiency are discussed in detail. The mechanical deflection angle of the scanning grating can reach ±5°, corresponding to an optical scan range of 20° at a driving voltage of 30 V.

A tip–tilt–piston micromirror with a double S-shaped unimorph piezoelectric actuator

This paper presents the design, fabrication and characterization of a tip–tilt–piston (TTP) piezoelectric micromirror. A unique double S-shaped unimorph piezoelectric (dSUP) actuator design is employed. The dSUP actuator design can generate large vertical displacement. With four such actuators symmetrically located on the four sides of the mirror plate, both tip and tilt as well as piston motion can be realized. Lead zirconate titanate (PZT) is used due to its high piezoelectric coefficient and it is fabricated with a sol–gel method. The Zr/Ti ratio of the PZT material is 53/47. The dSUP actuators consist of Pt/Ti/PZT/Pt/Ti/SiO2 multilayers. The thickness of the PZT layer is 0.7μm. The 1.1mm×1.1mm mirror plate is backed by a 50μm-thick single-crystal silicon layer to ensure the flatness. Backside deep silicon etching and front-side isotropic silicon undercut are used to release the device. Experiments show that the resonant frequency of the tip–tilt scan modes is 3.5kHz. 27μm vertical displacement was observed under 5V DC driving of one pair of opposite actuator and the scan angle can achieve 9.65° under sine wave resonant driving at 2V amplitude on one pair of opposite actuator.

Tension–Torsion Combined Loading Test Equipment for a Minute Beam Specimen

In this article, the development of quasi-static tension–torsion combined loading test equipment for a microscale beam specimen is described. The equipment is composed of a piezoelectric actuator in actuator case for uniaxial tensile loading, a load cell for measuring X-Y-Z-axes forces and θ-axis torque, a stepping motor for rotating sample stage, X-Y-Z-stages for alignment, and a CCD camera for measuring tensile elongation using original image analysis software. The shape and dimension of all the mechanical jigs were designed by means of finite element analysis (FEA). The tension and torsion loading systems are able to be individually operated, so that uniaxial tension, pure torsion, and combined tension–torsion loadings can be realized. The specimen that was designed in consideration of typical optical microelectromechanical systems (MEMS) devices consists of a mirror plate supported by two microbeam structures, four springs, and a frame with chucking holes. Single crystal silicon (SCS) specimens were fabricated by deep reactive ion etching (DRIE). It was confirmed that the above-described three types of loadings were able to be successfully applied to the beam specimens. All the specimens fractured in a brittle manner and showed different-shape fracture surfaces under different deformation modes.

200kW 탑형 태양열발전시스템의 Heliostat Field 설계

Heliostat field is the most important subsystem in the tower type solar thermal power plant since its optical performance affects the total system efficiency most significantly while the construction cost of it is the major part of total construction cost in such a power plant. Thus a well designed heliostat field to maximize the optical efficiency as well as to minimize the land usage is very important. This work presents methodology, procedures and result of heliostat filed design for 200kW solar thermal power plant built recently in Daegu, Korea. A rectangular shaped receiver located at 43(m) high and tilted toward heliostat field, 450 of heliostats of which the reflective surface is formed by 4 of flat plate mirror facet, and the land area having about size are used to form the heliostat field. A procedure to deploy 450 heliostats in radial staggered nonblocking formation is developed. Also the procedures to compute the cosine effect, intercept ratio, blocking and shading ratio in the field are developed. Finally the heliostat filed is designed by finding the optimal radial distance and azimuthal spacing in radial staggered nonblocking formation such that the designed heliostat field optical efficiency could be maximized. The designed heliostat field has 77% of annual average optical efficiency, which is obtained by annually averaging the optical efficiencies computed between the time of where sun elevation angle becomes after sunrise and the time of where sun elevation angle becomes before sunset in each day.

A water-immersible 2-axis scanning mirror microsystem for ultrasound andha photoacoustic microscopic imaging applications.

Fast scanning is highly desired for both ultrasound and photoacoustic microscopic imaging, whereas the liquid environment required for acoustic propagation limits the usage of traditional microelectromechanical systems (MEMS) scanning mirrors. Here, a new water-immersible scanning mirror microsystem has been designed, fabricated and tested. To achieve reliable underwater scanning, flexible polymer torsion hinges fabricated by laser micromachining were used to support the reflective silicon mirror plate. Two efficient electromagnetic microactuators consisting of compact RF choke inductors and high-strength neodymium magnet disc were constructed to drive the silicon mirror plate around a fast axis and a slow axis. The performance of this water-immersible scanning mirror microsystem in both air and water were tested using the laser tracing method. For the fast axis, the resonance frequency reached 224 Hz in air and 164 Hz in water, respectively. The scanning angles in both air and water under ±16 V DC driving were ±12°. The scanning angles in air and water under ±10 V AC driving (at the resonance frequencies) were ±13.6° and ±10°. For the slow axis, the resonance frequency reached 55 Hz in air and 38 Hz in water, respectively. The scanning angles in both air and water under ±10 V DC driving were ±6.5°. The scanning angles in air and water under ±10 V AC driving (at the resonance frequencies) were ±8.5° and ±6°. The feasibility of using such a water-immersible scanning mirror microsystem for scanning ultrasound microscopic imaging has been demonstrated with a 25-MHz ultrasound pulse/echo system and a target consisting of three optical fibers.

Large size MEMS scanning mirror with vertical comb drive for tunable optical filter

This paper presents the design, fabrication and characterization of a large size MEMS scanning mirror in application of tunable optical filter (TOF). In the design of scanning mirror, vertical comb drive is used for its large force density, low driving voltage and also no influence of pull-in effect. The mirror plate has a size of 2.7mm×1.8mm which is suitable for the optical requirement of TOF. In each side of the mirror, 186 combs are set to provide a suitable rotation angle. The length, width and thickness of the combs are 300μm, 7μm and 25μm, respectively. The gap between the adjacent combs is 4μm. The scanning mirror with vertical comb drive has been successfully realized using the bulk micromachining technologies. The measured static and dynamic characteristics show that the scanning mirror can achieve a maximal rotation angle of 2.3° with a direct current (DC) driving voltage of 95V. The turn-on responding time of the scanning mirror is 1.887ms and the turn-off responding time is 4.194ms. The tuning function has also been demonstrated and a 1.507ms tuning time between two adjacent channels is obtained.

MEMS mirrors based on a curved concentric electrothermal actuator

A curved concentric electrothermal actuator has been designed and developed to actuate circular micromirrors with improved area efficiency, while at the same time achieving large scan range at low voltage. This actuator consists of three curved concentric Aluminum/Tungsten bimorphs for fast thermal response and high responsivity, and two rigid frames connected in between for scan range amplification. A tip–tilt–piston micromirror with a circular mirror plate based on this actuator design has been proposed and fabricated. The mirror is capable of scanning ±11° at 0.6V, and generating a 227μm piston displacement at only 0.8V. The measured lateral shift and tilt angle of the mirror plate are less than 7μm and 0.7°, respectively, through the entire piston displacement. A piston-only micromirror has also been demonstrated, and it has even smaller lateral shift of less than 3μm and tilt of less than 0.4° through the piston scan range. This mirror generates large vertical displacement of about 200μm at only 0.9V.

Highly selective trapping of enteropathogenic E. coli on Fabry–Pérot sensor mirrors

Untreated recycled water, such as sewage and graywater, will almost always contain a wide range of agents that are likely to present risks to human health, including chemicals and pathogenic microorganisms. The microbial hazards, such as large numbers of enteric pathogens that can cause gastroenteric illness if ingested, are the main cause of concern for human health. The presence of the enteropathogenic Escherichia coli (EPEC) serotype is of particular concern, as this group of bacteria is responsible for causing severe infant and travelers’ diarrhea, gastroenteritis and hemolytic uremic syndrome. A biosensing system based on an optical Fabry–Pérot (FP) cavity, capable of directly detecting the presence of EPEC within 5min, has been developed using a simple micro-thin double-sided adhesive tape and two semi-transparent FP mirror plates. The system utilizes a poly(methyl methacrylate) (PMMA) or glass substrates sputtered by 40-nm-thick gold thin films serving as FP mirrors. Mirrors have been activated using 0.1M mercaptopropionic acid, influencing an immobilization density of the translocated intimin receptor (TIR) of 100ng/cm2. The specificity of recognition was confirmed by exposing TIR functionalized surfaces to four taxonomically related and/or distantly related bacterial strains. It was found that the TIR-functionalized surfaces did not show any bacterial capture for these other bacterial strains within a 15min incubation period.

A beam shaping design for coupling high power diode laser stack to fiber with capability of spectral narrowing and stabilizing

We applied a VHG-FAC lens in our design in this work to collimate the fast axis and lock the output spectrally. We used a beam shaping technique to improve the beam symmetry and power density of a high power diode laser stack with a stripe mirror plate, a V-Stack mirror and polarization beam combining elements. By this technique, the beam of a high power diode laser stack is effectively coupled into a standard 365μmcore diameter and a NA=0.22 fiber. By this technique, compactness, higher efficiency, narrower spectral line width and lower production cost of the diodes are possible.

Multiple-Height Microstructure Fabricated by Deep Reactive Ion Etching and Selective Ashing of Resist Layer Combined with Ultraviolet Curing

UV-cured photoresist is applied to the delay masking process to realize a multiple-height microstructure for the first time. Although the UV-cured photoresist is a soft mask, its material property becomes stable against resist thinner and UV exposure. A layered resist pattern can be realized by stacking normal photoresist on the UV-cured photoresist. The UV curing increases the glass transition temperature from 120 to 160 °C. By controlling the temperature, the normal photoresist can be ashed twice as fast as the UV-cured photoresist. This selectivity can be combined with the deep reactive ion etching of Si, and a microstructure having three different etching depths is realized, thus forming a micromirror. The multiple-height structure is advantageous for reducing the inertia of the mirror plate. For the same rotational spring constant, the micromirror has a higher resonant frequency, which is required for realizing higher-resolution laser displays.

Multiple-Height Microstructure Fabricated by Deep Reactive Ion Etching and Selective Ashing of Resist Layer Combined with Ultraviolet Curing

UV-cured photoresist is applied to the delay masking process to realize a multiple-height microstructure for the first time. Although the UV-cured photoresist is a soft mask, its material property becomes stable against resist thinner and UV exposure. A layered resist pattern can be realized by stacking normal photoresist on the UV-cured photoresist. The UV curing increases the glass transition temperature from 120 to 160 °C. By controlling the temperature, the normal photoresist can be ashed twice as fast as the UV-cured photoresist. This selectivity can be combined with the deep reactive ion etching of Si, and a microstructure having three different etching depths is realized, thus forming a micromirror. The multiple-height structure is advantageous for reducing the inertia of the mirror plate. For the same rotational spring constant, the micromirror has a higher resonant frequency, which is required for realizing higher-resolution laser displays.