三田 信

Explorers attempting to land on a lunar or planetary surface must use three-dimensional image sensors to measure landing site topography for obstacle avoidance. Requirements for such sensors are similar to those mounted on vehicles and include the need for time synchronization within one frame. We introduce a 1K (32 x 32)-pixel three-dimensional image sensor using an array of InGaAs Geiger-mode avalanche photodiodes capable of photon counting in eye-safe bands and present evaluation results for sensitivity and resolution.

GEO-X (GEOspace X-ray imager) is a 50 kg-class small satellite to image the global Earth's magnetosphere in X-rays via solar wind charge exchange emission. A 12U CubeSat will be injected into an elliptical orbit with an apogee distance of ∼40 Earth radii. In order to observe the diffuse soft X-ray emission in 0.3-2 keV and to verify X-ray imaging of the dayside structures of the magnetosphere such as cusps, magnetosheaths and magnetopauses which are identified statistically by in-situ satellite observations, an original light-weight X-ray imaging spectrometer (∼10 kg, ∼10 W, ∼10×10×30 cm) will be carried. The payload is composed of a ultra light-weight MEMS Wolter type-I telescope (∼4×4 deg2 FOV, <10 arcmin resolution) and a high speed CMOS sensor with a thin optical blocking filter (∼2×2 cm2, frame rate ∼20 ms, energy resolution <80 eV FWHM at 0.6 keV). An aimed launch year is 2023-25 corresponding to the 25th solar maximum.

Three-dimensional (3D) image sensors have many applications, including enabling autonomous vehicles to avoid obstacles and providing guidance, navigation, and control for spacecraft immediately before landing on a celestial body. Flash LIDAR is a system that can acquire a 3D image by emitting a diffuse pulsed laser beam, and hence is suitable for both obstacle detection and terrain measurement. In the 3D image sensors used for Flash LIDAR, a photosensor array and time measurement integrated circuit are vertically bonded. Here, we report the results of a detailed evaluation of the principles, functions, sensitivity, and time measurement accuracy of a prototype 1-k pixel (32 x 32 pixels) 3D image sensor based on a multi-pixel photon counting avalanche photodiode. By counting photons, a 3D image sensor is realized that has both high sensitivity and the ability to measure light intensity.

Copyright © 2019 by the International Astronautical Federation (IAF). All rights reserved. This paper presents the proto-flight model results of X band synthetic aperture radar for 100ok class satellites including the RF power amplifier, the high speed data storage/transmission system, and the SAR response test results on ground. The specifications of SAR performance are single polarization SAR with 3m ground resolution for strip map mode. 1 m ground resolution can be achieved with sliding spot light mode under condition of limited value of NESZ. The data down link is high speed X band down link with max.2.65Gbps. We will launch the first demonstration SAR satellite in 2020 as collaboration with a private company.

This paper presents the proto-flight model test results of X hand synthetic aperture radar for small satellites with 130kg mass. The specification of SAR performance is single polarization SAR with 3m ground resolution for strip map mode. Optional 1 m ground resolution can he achieved with sliding spot light mode under condition of limited valus of NFSZ. The paper describes the unique antenna system, the RF power amplifier, high speed data storage/transmission system, and the ground SAR response test results.

The exploration of energization and radiation in geospace (ERG) satellite, nicknamed "Arase," is the second satellite in a series of small scientific satellites created by the Institute of Space and Astronautical Science of the Japan Aerospace Exploration Agency. It was launched on December 20, 2016, by the Epsilon launch vehicle. The purpose of the ERG project is to investigate how high-energy (over MeV) electrons in the radiation belts surrounding Earth are generated and lost by monitoring the interactions between plasma waves and electrically charged particles. To measure these physical processes in situ, the ERG satellite traverses the heart of the radiation belts. The orbit of the ERG is highly elliptical and varies due to the perturbation force: the apogee altitude is approximately 32,200-32,300 km, and the perigee altitude is 340-440 km. In this study, we introduce the scientific background for this project and four major challenges that need to be addressed to effectively carry out this scientific mission with a small satellite: (1) dealing with harsh environmental conditions in orbit and electromagnetic compatibility issues, (2) spin attitude stabilization and avoiding excitation of the libration by flexible structures, (3) attaining an appropriate balance between the mission requirements and the limited resources of the small satellite, and (4) the adaptation and use of a flexible standardized bus. In this context, we describe the development process and the flight operations for the satellite, which is currently working as designed and obtaining excellent data in its mission.

The fluxgate magnetometer for the Arase (ERG) spacecraft mission was built to investigate particle acceleration processes in the inner magnetosphere. Precise measurements of the field intensity and direction are essential in studying the motion of particles, the properties of waves interacting with the particles, and magnetic field variations induced by electric currents. By observing temporal field variations, we will more deeply understand magnetohydrodynamic and electromagnetic ion-cyclotron waves in the ultra-low-frequency range, which can cause production and loss of relativistic electrons and ring-current particles. The hardware and software designs of the Magnetic Field Experiment (MGF) were optimized to meet the requirements for studying these phenomena. The MGF makes measurements at a sampling rate of 256 vectors/s, and the data are averaged onboard to fit the telemetry budget. The magnetometer switches the dynamic range between +/- 8000 and +/- 60,000 nT, depending on the local magnetic field intensity. The experiment is calibrated by preflight tests and through analysis of in-orbit data. MGF data are edited into files with a common data file format, archived on a data server, and made available to the science community. Magnetic field observation by the MGF will significantly improve our knowledge of the growth and decay of radiation belts and ring currents, as well as the dynamics of geospace storms.

We propose an all-silicon multi-layer interference filter composed solely of silicon with sub-wavelength structure (SWS) in order to realize high performance optical filters operating in the THz frequency region with robustness against cryogenic thermal cycling and mechanical damage. We demonstrate fabrication of a three-layer prototype using well-established common micro-electro-mechanical systems (MEMS) technologies as a first step toward developing practical filters. The measured transmittance of the three-layer filter agrees well with the theoretical transmittances calculated by a simple thin-film calculation with effective refractive indices as well as a rigorous coupled-wave analysis simulation. We experimentally show that SWS layers can work as homogeneous thin-film interference layers with effective refractive indices even if there are multiple SWS layers in a filter.

PROCYON is a first full-scale, 50-kg-class probe featuring most of the key technologies for deep-space exploration. It was developed by the University of Tokyo and ISAS/JAXA and launched with Hayabusa 2 on 3 Dec 2014. PROCYON has a newly developed X-band telecommunication system fully compatible with the frequency range, up- and down-link turn-around ratio, modulation scheme, and DDOR tones following CCSDS-recommended standards, and it can establish X-band coherent two-way communication and ranging links with deep-space stations as larger deep-space probes have done. The total mass of the onboard telecommunication system is 7.3 kg excluding its RF coaxial harness, and total power consumption during two-way communication, 15 W of RF output power at SSPA, is 54.3 W. After launch, PROCYON's telecommunication system has been successfully working according to the system design. These achievements will provide core technologies for nextgeneration deep-space exploration by ultra-small probes.

A focal plane based on MKID has been designed for cosmic microwave background (CMB) B-mode polarization experiments. We are designing and developing a focal plane with broadband corrugated horn array, planar OMT, 180 degree hybrid, bandpass filters, and MKIDs. The focal plane consists of 3 octave bands (55 - 108 GHz, 80 - 160 GHz, 160 - 320 GHz), 10 hexagonal modules. Broadband corrugated horn-array has been directly machined from an Al block and measured to have a good beam shape which is consistent with electromagnetic field simulations in octave bands. The horn array is designed to be low standing-wave, light weight, and electromagnetic shield. The broadband 4 probes ortho-mode transducer (OMT) is fabricated on Si membrane of an SOI wafer. A broadband 180 degree hybrid made with coplanar waveguide (CPW) is used to reduce higher modes of the circular waveguide. Two bandpass filters of each polarization are patterned with Nb microstrip. A prototype of the broadband corrugated horn coupled MKIDs has been fabricated and tested.

We report the development of the visored shutter structure for astronomical instrument and the electrostatic operation in a 140K cryogenic environment without thermo-mechanical failure.

An equivalent circuit model for a semiparallel plate electrostatic torsion mirror has been developed based on an electrical circuit simulator. An analytical model for the electrostatic torque has been translated into a nonlinear dependent current source as a function of the input voltages that interpret the drive voltages and the mirror angle. Use of the suspension width as a fitting parameter explained well the experimental results on frequency response and the mirror's static deflection. (c) 2013 Wiley Periodicals, Inc. Electron Comm Jpn, 97(1): 37-47, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.11486

This paper presents a multiphysics simulation and layout design technique for complementary metal-oxide-semiconductor-microelectromechanical systems (MEMS)(CMOS-MEMS) based on an electrical circuit simulator. An equivalent circuit model for the mechanical equation of motion has been translated into a Verilog-A-compatible hardware description language (HDL) in the Cadence Virtuoso environment to attain new designing capabilities such as automatic mask-layout synthesis, design rule check, and layout-versus-schematic verification for MEMS structures. Microelectromechanical components such as parallel-plate actuator and bending suspension, whose analytical equation models are already known, are also interpreted into HDL-coded equivalent circuits. Behavior of a MEMS device, including the electrostatic displacement hysteresis and the negative spring constant effect, is numerically simulated as a lumped mass-and-spring system, which has been verified to quantitatively agree with that of the corresponding analytical simulation results. A multiphysics model for the Colpitts oscillator circuit has been built in the developed simulation environment by replacing a quartz resonator with a compact model of an electrostatic silicon resonator, and its self-excited resonance has been confirmed by the simulation after the coordination of the device and circuit parameters. A prototype conversion tool for MEMS parameterized cell has also been developed to demonstrate automatic generation of mask layouts for a silicon resonator, which has been crosschecked against the experimental measurements to verify the simulation accuracy. [2012-0365]

We have successfully fabricated electrostatic microactuators in a flexible sheet (i.e. microactuators made of the flexible sheet). In this fabrication, we used Kapton® sheets (DU PONT-TORAY) of 25μm thick as the flexible (structural) material, one mask and one additional shadow-mask to form comb-drive electrostatic microactuators in the sheet. As the first result, we could obtain the lateral displacement of 1μm to 14μm with applied voltage from 20V to 120V. We also could drive the actuators in the sheet fixed on a curved surface. © 2013 IEEE.

We have developed a new microelectromechanical logic device using the MEMS (Micro Electro Mechanical Systems) technology. This device consists simply of a single cantilever and two driving electrodes with two contact pads for electrostatic operation. Both exclusive NOR (XNOR) and exclusive OR (XOR) logic devices have been realized using this simple construction.

We report on our first X-ray imaging test of our novel ultra-lightweight and high-resolution MEMS X-ray optics for future space astronomical missions. We have fabricated a single-stage test optic made of Si from a Si (1 1 1) wafer with a thickness of 300 mu m. We conducted a dry etching and made 20 mu m line and space through holes to use their side walls for X-ray mirrors. We have smoothed the side walls by annealing and plastically bending the wafer to a spherical shape with a curvature of radius of 1000 mm. We have irradiated Al K alpha 1.49 key to the test optic and, for the first time. have verified X-ray focusing. An evaluated angular resolution ranged from 26 to 130 arcmin, which is two orders of magnitude worse than our goal of 15 arcsec. We found that this degraded resolution is mainly due to a large surface roughness of the side walls >10 mu m scale and possibly the deformation process. An estimated X-ray reflectivity was also an order of magnitude lower than the theoretical value assuming flat side walls. We concluded that this could be due to the loss of the reflective area by the rough surface. Therefore, the future improvement on the large scale surface roughness is indispensable for the better angular resolution and effective area. (C) 2012 Elsevier B.V. All rights reserved.

An electrostatic micro actuator with an electrical contact between the electrodes is known to show a limit-cycle behavior due to the combination of electrostatic pull-in and release. We newly used an electrical circuit simulator to make an equivalent circuit model to reproduce the limit-cycle by multi-physics simulation. This simulation results were found to explain the experimenntally observed behavior of the developedMEMS voltage to frequency convertor (VFC).

We have developed an inertia-driven micro actuator for harsh environment of space. Different from the conventional PZT-driven or other actuators, the newly developed electrostatic mechanism is free from the material property change due to temperature. A mass suspended in the actuation system is designed to collide with the internal wall to give thrust by the impact-type inchworm mechanism.

An equivalent circuit model for the semi-parallel plate electrostatic torsion mirror has been developed based on the electrical circuit simulator. An analytical model for the electrostatic torque has been translated into a nonlinear dependent current source as a function of input voltages that interpret the drive voltages and the mirror angle. A use of the suspension width as a fitting parameter explained well the experimental results of frequency response and the mirror's static deflection.

A newly developed multi-physics simulation tool for MEMS (microelectromechanical systems) has been applied to a branched suspension structure to study the versatility of analysis. More than two suspension modules or actuator modules can be connected to a mass module that solves the equation of motion without modifying the internal equivalent circuit module, thanks to the carefully designed signal handling method, where displacement and velocity are interpreted as voltage while mechanical force as electrical current. A 4-bit microelectromechanical digital-to-analog converter of displacement has been modeled as a verification to reproduce the micromechanical behavior.

In this paper, we present demonstrations of autonomous decentralized MEMS (ADM). The ADM is a large scale array of "monolithically integrated cell", in which "microactuators" are integrated with a "micro sensor" and a "micro processing unit (MPU)" (Fig. 1a). We applied autonomous decentralized algorithms based on "cellular automata" to our developed micro manipulator. This manipulator is not monolithically integrated one but an equivalent system to the ADM by stacking an actuator array on a sensor array (Fig. 1b). We could observe smart functions of micro object manipulations.

We present the current status of the development of the SPICA Coronagraph Instrument (SCI). SPICA is a next-generation 3-meter class infrared telescope, which will be launched in 2022. SCI is high-contrast imaging, spectroscopic instrument mainly for direct detection and spectroscopy of extra-solar planets in the near-to-mid infrared wavelengths to characterize their atmospheres, physical parameters and evolutionary scenarios. SCI is now under the international review process. In this paper, we present a science case of SCI. The main targets of SCI, not only for direct imaging but also for spectroscopy, are young to matured giant planets. We will also show that some of known exoplanets by ground-based direct detection are good targets for SCI, and a number of direct detection planets that are suitable for SCI will be significantly increased in the next decade. Second, a general design of SCI and a key technology including a new high-throughput binary mask coronagraph, will be presented. Furthermore, we will show that SCI is potentially capable of achieving 10(-6) contrast by a PSF subtraction method, even with a telescope pointing error. This contrast enhancement will be important to characterize low-mass and cool planets.

An equivalent circuit model for the resonant-type vertical comb-driven optical MEMS (micro electro mechanical system) scanner has been developed based on the simple extension of the parallel-plate model. Both the electrostatic torque and the induction charge models are interpreted by using the equation-defined nonlinear dependent current source on the electrical circuit simulator platform. A systematic procedure has been investigated to fit the analytical model with the experimental results by using fitting parameters including the damping coefficient, the suspension width, and the comb gap. The developed simulation model has been used to verify a new control scheme to tune the scanner's oscillation amplitude in resonance by means of the pulse-width modulation of voltage at a given pulse height the result indicates the effective use of digital electronics for the comb-driven optical scanner. © 2012 The Institute of Electrical Engineers of Japan.

We have been developing our original MEMS-based X-ray optics for future astronomical missions. To date, we verified the focusing of optical light and X-ray for the first time. The concept and recent advances are reviewed.

A lithium-ion battery was developed using off-the-shelf pouch cells and launched with a small scientific satellite "REIMEI." The cells were potted with polyurethane or epoxy resin to protect the battery from vacuum in space. Preliminary experimental test results of pouch cells potted in a soft aluminum cap suggested that the cells tended to swell in vacuum, although they had been reinforced with the resins. Bread board models (BBMs), in which pouch cells were potted with resins in a hard aluminum case, were fabricated for cycle life performance tests in the laboratory. The test results indicated that the performance of epoxy-potted BBM was superior to that of the polyurethane-potted BBM. The measured cell resistance implied that the electrolyte solution leaked through the polyurethane resin, resulting in premature deterioration. The epoxy resin was used for the flight battery. The end-of-discharge-voltage (EoDV) trend of the flight battery on orbit was compared with the laboratory test results corrected based on a post-launch cycle test using a fresh cell. The corrected EoDV trend in the laboratory was in good agreement with the on-orbit trend for the early cycle period, indicating that the on-orbit battery was not inadvertently affected by conditions in space. (C) 2011 Elsevier B.V. All rights reserved.

The plasticity of covalently bonded materials is a subject at the forefront of materials science, bearing on a wide range of technological and fundamental aspects. However, covalent materials fracture in a brittle manner when the deformation exceeds just a few per cent. It is predicted that a macroscopically brittle material like silicon can show nanoscale plasticity. Here we report the exceptional plasticity observed in silicon nanocontacts ('nanobridges') at room temperature using a special experimental setup combining a transmission electron microscope and a microelectromechanical system. When accounting for surface diffusion, we succeeded in elongating the nanocontact into a wire-like structure, with a fivefold increase in volume, up to more than twenty times the original length. Such a large plasticity was caused by the stress-assisted diffusion and the sliding of the intergranular, amorphous-like material among the nanocrystals.

This paper describes the outline and the five years' on-orbit results of the small scientific satellite REIMEI for aurora observations and demonstrations of advanced small satellite technologies. REIMEI is a small satellite with 72 kg mass, and is provided with three-axis attitude control capabilities for aurora observations. REIMEI was launched into a nearly sun synchronous polar orbit on Aug. 23rd, 2005, from Baikonur, Kazakhstan, by Dnepr rocket. REIMEI satellite has been satisfactorily working on the orbit for five years at present as of January, 2011. Three-axis control is achieved with accuracy of 0.1 degrees (3 sigma). Multi-spectrum images of aurora are taken with 8 Hz rate and 2 km spatial resolution to investigate the aurora physics. REIMEI is performing the simultaneous observation of aurora images and particle measurements. REIMEI indicates that even a small satellite launched as a piggy-back can successfully perform unique scientific mission purposes. (C) 2011 Elsevier Ltd. All rights reserved.

We present the SPICA Coronagraphic Instrument (SCI), which has been designed for a concentrated study of extra-solar planets (exoplanets). SPICA mission provides us with a unique opportunity to make high contrast observations because of its large telescope aperture, the simple pupil shape, and the capability for making infrared observations from space. The primary objectives for the SCI are the direct coronagraphic detection and spectroscopy of Jovian exoplanets in infrared, while the monitoring of transiting planets is another important target. The specification and an overview of the design of the instrument are shown. In the SCI, coronagraphic and non-coronagraphic modes are aplicable for both an imaging and a spectroscopy. The core wavelength range and the goal contrast of the coronagraphic mode are 3.5-27 μm, and 10 , respectively. Two complemental designs of binary shaped pupil mask coronagraph are presented. The SCI has capability of simultaneous observations of one target using two channels, a short channel with an InSb detector and a long wavelength channel with a Si:As detector. We also give a report on the current progress in the development of key technologies for the SCI. © 2011 COSPAR. Published by Elsevier Ltd. All rights reserved. 31. -6

We report a newly developed equivalent electrical circuit for microelectromechanical systems (MEMS) based on a circuit simulator Qucs (Quite Universal Circuit Simulator). An analog computing solver for the equation of motion (EOM) has been interpreted to an electrical equivalent circuit by using an electrical capacitor as an ideal mathematic integrator. Viscoelastic suspension and electrostatic parallel-plate actuator are modeled as equivalent subcircuits that can be cosolved with the EOM module. Those subcircuit models are used as building blocks to numerically simulate the behavior of various types of MEMS actuators. Thanks to the well-prepared simulation toolbox of Qucs, multiphysics analysis of micromechanical and electrical quantities has become straightforward on a single platform. Equivalent circuit models for coupled oscillator and parallel-plate electrostatic actuator (including mechanical contact after electrostatic pull-in) are presented as a verification program to examine the simulation accuracy. (C) 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

This paper proposes a novel structure of microelectromechanical-systems-based 1-D spatial light phase modulator (SLPM) that consists of a micromirror array on a silicon-on-insulator (SOI) wafer and indium tin oxide (ITO) electrodes on a glass plate. Each micromirror can exhibit bidirectional single-axis tilt, as well as up-and-down piston motions by combining the applied voltage on two ITO electrodes placed over the micromirror and the substrate of SOI (in the case that the substrate is energized, all micromirrors go down simultaneously). This device configuration enables SLPM to be fabricated by a simple process. Part I of this paper focuses on the principles and the design of the device. The optimum parameters of the device are derived to realize both tilt and piston motions, considering ways to reduce mirror warpage and crosstalk from the ITO electrode from the adjacent mirror. We simulate the dc and ac characteristics of the device and confirm that the designs that we optimized satisfy the target specifications to be widely used in optical communication systems.

In part I of this paper, we have proposed a novel structure of microelectromechanical-systems-based 1-D spatial light phase modulator (SLPM). We have discussed the design of the device and derived the optimum parameters to satisfy the target specifications. In part II, we focus on the fabrication process and experimental results of the device. We show that this device configuration allows us to use a simple fabrication process. We fabricated the device consisted of 24 micromirrors and realized the tilt and piston motions successfully. The measured dc (rotation angle and displacement on driving voltage) and ac (frequency response) characteristics matched well to the simulated data derived in part I. We also examined the distribution of the resonant frequencies over 24 micromirrors and verified that the variance was kept within 2%. As one of the applications of the device, we applied the device to optical beam shaping and succeeded in shaping the optical beam properly depending on the surface patterns of the SLPM. With these achievements, we show that the device can be adopted to a wide variety of applications in optical communication systems and optical signal processing.

We report a new structure of electrostatically addressable and latchable multi-slit shutter array for the astronomical spectrograph with an improved optical and electromechanical performance using the electroplated visors.

We are trying to develop high performance mid-infrared (MIR) and far-infrared (FIR) optical filters with mechanical strength and robustness for thermal cycling toward cryogenic infrared astronomical space missions. Multilayer interference filters enable us to design a wide variety of spectral response by controlling refractive index and thickness of each layer, however, in longer MIR and FIR (30-300 mu m) wavelength regions, there are a few optical materials known to have both good transparency and physical robustness, which makes difficult to realize high performance filters because of limited refractive index values. It is also difficult to deposit thick layers required for MIR/FIR multilayer filters by conventional method. Furthermore, multilayer interference filters are realized by thin film coatings having different coefficients of thermal expansion (CTE), which makes filters fragile for thermal cycling. To clear these problems, we introduce sub-wavelength structures (SWS) for controlling the refractive index. Then, only one material is necessary for fabricating filters, which enables us to fabricate filters with mechanical strength and robustness for thermal cycling. In 30-300 mu m wavelength regions silicon is very suitable for filter material because not only silicon has little absorption and physical robustness but also SWS are easily fabricated by micro-electro mechanical systems (MEMS) technology. As a first step, we have fabricated anti-reflection SWS layer on silicon wafers to demonstrate the refractive index control by simple SWS (periodic cylindrical holes on a silicon wafer). Comparing measured transmittance with both effective medium approximation (EMA) theory and rigorous coupled wave analysis (RCWA) simulation, we confirm that the refractive control of SWS layer is verified.

X-ray optics based on MEMS technologies can provide future astronomical missions with ultra light-weight and high performance optical systems. A silicon optics was fabricated using dry etching and annealing technologies. An angular resolution evaluated in the X-ray wavelength range was about 20 arcmin in full width half maximum, corresponding to 3.1 mm. In this paper, to achieve a better angular resolution, the silicon dry etching and annealing processes are conditioned. The surface roughness of sidewalls were measured at a 100 mu m scale. After the conditionings, it has been improved by a factor of four.

Basic studies of nanometer scale phenomena, such as tribology, fusion bonding and deformation, are important for a MEMS/NEMS device. To better understand these nanometer scale phenomena, the combination of MEMS and transmission electron microscopy (TEM) setup is an invaluable tool. This combination allows for the direct observation of a deformation process at the nano-scale when a MEMS for the investigation of a nano-interface (MINI) device with sharp opposing tips is placed under a TEM. This paper describes the design and fabrication of a MINI that can perform an in situ experiment under TEM observation. We designed the MINI to minimize the misalignment of the opposing tips in order to provide adequate observation possibilities of the nanocontacts. In addition, we developed processes for the fabrication of a MINI and characterized it inside the TEM. Furthermore, silicon-silicon, gold-gold and silicon-gold opposing tips were designed and fabricated for experiments of the nano-interface of homogeneous and heterogeneous material. The MEMS tips were used to show an approach-contact-retraction-fracture cycle of a gold nanocontact under real-time TEM observation.

The x-ray reflectivity of an ultralightweight and low-cost x-ray optic using anisotropic wet etching of Si (110) wafers is evaluated at two energies, C K-alpha 0.28 keV and Al K-alpha 1.49 keV. The obtained reflectivities at both energies are not represented by a simple planar mirror model considering surface roughness. Hence, an geometrical occultation effect due to step structures upon the etched mirror surface is taken into account. Then, the reflectivities are represented by the theoretical model. The estimated surface roughness at C K-alpha (similar to 6 nm rms) is significantly larger than similar to 1 nm at Al K-alpha. This can be explained by different coherent lengths at two energies. (C) 2010 Optical Society of America

In this paper, we present a versatile planar manipulator composed of a stack-integrated arrays of microactuators and sensors. In this system, a transparent actuator array chip of 16 x 16 cells is stacked on a photo sensor array chip of the same cell size as the actuator array (1.5mm x 1.5mm). Each cell of the actuator array has four orthogonal thermo-bimorph actuators of 500μm in length, 100μm in width and 6μm in thickness. The system can manipulate an object by XY planar positioning (planar conveyance) as well as by posture (i.e. direction of an object) control (rotational conveyance). These manipulations are performed by feedback controls of actuators based on the information from sensor arrays. Especially, in this paper, we focus on the posture control (rotational conveyance) of the system, because this function is indispensable for the manipulation (not just conveyance) of objects. An experimental result shows the rotation of 180 degrees in 33 seconds with the feedback operation of the system. © 2010 IEEE.

An X-ray imaging test for an X-ray optical system based on MEMS technologies was conducted at the ISAS 30 m beamline. An X-ray reflection and focusing were successfully verified at Al Kα 1.49 keV for the first time. The image quality estimated as a half power diameter was ∼20 arcmin. This was consistent with the angular resolution estimated from the surface roughness of 200 nm rms at 100 ìm scale. In this paper, the experimental setup and the result of X-ray imaging analysis are reported. ©2010 IEEE.

We have already proposed a simulation model for a 90-deg-tilted MEMS mirror, but in some reasons, numerical simulation methods for several angle counter electrode devices are not established. In order to solve these problems, we propose a cascade drive voltage signal technique and demonstrate a 51.5 deg tilted angle counter electrode and assure the effectiveness of the equivalence circuit. ©2010 IEEE.

We have developed a novel 2-axis MEMS scanner of the small laser radar for landing to the planet. The scanner has to overcome launching vibration and impact and can be used in harsh environment of the space. ©2010 IEEE.

We are developing high performance mid-infrared (especially 30-40 mu m wavelength regions) multilayer interference filters with mechanical strength and robustness for thermal cycling toward cryogenic infrared astronomical missions. Multilayer interference filters enable us to design a wide variety of spectral response by controlling refractive index and thickness of each layer. However, in mid-and far-infrared (MIR/FIR) regions, there are a few optical materials so that we can only use limited refractive index values to design filters, which makes difficult to realize high performance filters. It is also difficult to deposit thick layers required for MIR/FIR multilayer filters. Furthermore, deposition of two materials, which have different coefficients of thermal expansion, makes filters fragile for thermal cycling. To clear these problems, we introduce sub-wavelength structures (SWS) for controlling the refractive index. Then, only one material is necessary for fabricating filters, which enables us to fabricate filters with mechanical strength and robustness for thermal cycling. According to the effective medium approximation (EMA) theory, the refractive index of randomly mixing materials in sub-wavelength scale is controllable by changing the ratio of mixing materials. However, it is not clear that EMA can be applied to such simple SWS, periodic cylindrical holes on a bulk material, which is easily fabricated by photolithography. In order to verify the controllability of refractive index by simple SWS, we have fabricated simple SWS on a silicon substrate and measured its transmittance. Comparing measured transmittance with theoretical transmittance calculated by EMA, we confirm that EMA can be applied to simple SWS fabricated by photolithography.

We propose a concept of mono-material multilayer interference optical filter that can be fabricated using simple micro-electro-mechanical systems (MEMS) technologies. The key point of this concept is to control the refractive index of each layer by sub-wavelength structure (SWS), not by selecting different materials. A homogeneous composition of material results in robustness in cryogenic thermal cycle, which is essential for highly sensitive infrared observations. We have fabricated antireflection (AR) SWS layers on silicon wafers as a demonstration of this concept. The evaluation of optical characteristics shows that the SWS layers can be used as layers of interference filters in infrared wavelength. (C) 2010 The Japan Society of Applied Physics