Akihiro Koga

Electrostatic linear microactuator mechanism for focusing a CCD camera

A newly developed linear electrostatic microactuator mechanism employing a vibrating motion is described. In order to achieve a miniature charge coupled device (CCD) camera with autofocusing and zoom functions, we developed an electrostatic linear microactuator with a large movement range. In miniature CCD cameras, extremely thin electrostatic actuators are needed because the space available for the focusing mechanism is reduced. The moving part (slider) of this actuator is sandwiched between fixed electrodes (stator), is alternately attached and detached to these fixed electrodes, and actuates linearly on a macroscopic level. The fundamental feasibility of this vibrating motion mechanism was first confirmed in experiments. This actuator was then applied to the focusing mechanism of a miniature CCD camera. A microlens was fitted inside the slider and it was possible to adjust the focus by moving the slider (with microlens). The size of the prototype for the focusing mechanism is 3.6/spl times/4.6/spl times/8.0 mm, and a 2-mm movement range is achieved. The minimum driving voltage is 60 V and the maximum velocity is 1.0 min/s.

Integrated flexible microactuator systems

The flexible microactuator (FMA) is a novel pneumatic rubber actuator developed for use in microrobots. This paper reports on integrated FMA systems to achieve distributed motion as occurs in intestinal villi, and with multi-legged arthropods such as centipedes. For the purpose of miniaturization and integration of FMAs, the authors focussed on two technical issues : A new fabrication process based on stereo lithography and a new FMA design called a restraint beam FMA. Stereo lithography enables fabrication of micro-structures with rubber-like materials suitable for integrated FMAs. The restraint beam FMA makes it possible to fabricate FMAs from a single material, allowing stereo lithography to be used. As examples of integrated FMA systems, four prototypes are shown : a 5 X 5 FMA array, a 3 X 3 FMA array which has pneumatic circuits at its base, a pipe interior mobile robot, and an amusement system consisting of 30 FMAs, which demonstrates ball handling ability.

Attachment/detachment electrostatic micro actuators for pan-tilt drive of a micro CCD camera

Newly developed linear electrostatic micro actuators employing an attachment/detachment mechanism and fabricated by a bulk silicon micromachining process are described. The moving part (slider) of these actuators is sandwiched between two glass plates whose surfaces have many electrodes (fixed electrodes), is attached to these fixed electrodes by turns up and down, and is actuated in the course of the linear motion. A feature of these actuators is that anti-friction bearings are not required and the influence of friction is reduced significantly. Several difficulties have been identified regarding attachment/detachment operation actuators. The accumulation of charge caused by contact between each stator and slider is one of the most difficult problems, and it can lead to complete actuator failure. The newly developed actuators have micro pyramid stoppers which prevent the accumulation of charge on both surfaces of the moving part. When a diving voltage of about 80 [V] is applied, the slider moves successfully with a /spl plusmn/1 [mm] stroke at a speed of 1.0 mm/sec under the condition of no load. The authors further apply these actuators to a micro pan-tilt mechanism for altering the vision angle of a micro CCD camera and experimentally confirm their practical utility.

A trench-type anti-wear microprobe with nano-scale electric contacts for AFM LAO lithography

A novel trench-type anti-wear microprobe with nano-scale electric contacts was proposed as an AFM probe to overcome the problem of probe tip wear and improve patterning stability in Atomic force microscope (AFM) local anodic oxidation (LAO) lithography. The proposed microprobe was fabricated using MEMS technique. The patterning and wear properties of the fabricated microprobe in AFM LAO lithography were investigated in terms of the change in the drawn line width and probe tip shape before and after a 20 mm scan. SEM images of the probe tips before and after the scan indicated that there was no obvious damage in the fabricated probe tip while apparent damage could be found on the conventional type probe tip. AFM LAO lithography results showed that the fabricated microprobe maintained a stable pattering performance before and after the 20 mm scan while the conventional type probe was unable to draw due to tip wear after the scan.

Electrostatic linear micro actuators with vibrating motion for pan-tilt drive of a micro CCD camera

Newly developed linear electrostatic micro actuators employing a vibrating motion and fabricated by a bulk silicon micromachining process are described. The moving part (slider) of these actuators is sandwiched between two glass plates whose surfaces have many electrodes (fixed electrodes), is attached and detached to these fixed electrodes by turns, and actuates linearly on a macroscopic level. A feature of these actuators is that the influence of friction is reduced significantly and a large stroke is achieved. However, several difficulties have been identified regarding attachment/detachment operation actuators. The interactive forces, including the accumulation of charge caused by contact between each stator and slider create one of the most difficult problems. Our developed actuators incorporate micro pyramid stoppers, which prevent the accumulation of charge and other interactive forces, on both surfaces of the moving parts. The casing size of the prototype is 8/spl times/8/spl times/1.2 mm and achieves a 2 mm range of movement. The minimum driving voltage is 60 V and maximum velocity is 2.0 mm/s. The behavior of the slider is not simple and further analysis is very important in order to improve positioning accuracy, increase output force, and decrease driving voltage. The characteristics of the actuator (Stepping Model) obtained by experiments is reported. The authors further apply these actuators to a micro pan-tilt mechanism for altering the vision angle of a micro CCD camera and experimentally confirm their practical utility.

Electric contact stability of anti-wear probes

For the practical realization of precise processes or devices utilizing scanning nanoprobes, not only improvement in the wear resistance of the probe tip but also a stable electric contact at the sliding probe electrode is required. To meet both these requirements, the authors developed an anti-wear probe having a supporting Si tip and a metal electrode, both of which slide on the substrate simultaneously. Probes with various electrode materials were evaluated to investigate the key factors of the material choice for maintaining good electric contact over a long sliding distance. The results show that the optimal management of material hardness, surface roughness, and probe contact force was important to realize an optimum performance from the probe.

Novel Adaptive Optics System with an Electrostatically-driven Deformable Mirror and Wavefront Compensation Algorithm

We have fabricated a membrane deformable mirror (DM) for ophthalmologic adaptive optics. An algorithm is demonstrated to compensate wavefront aberration of eyes, effectively. We have developed analysis systems that can predict the DM characteristics.

Electrostatic linear micro actuator with vibrating motion (application to the focusing mechanism of a miniature CCD camera)

A newly developed linear electrostatic micro actuator mechanism employing a vibrating motion is described. Features of this mechanism are that anti-friction bearings are not required, the influence of friction is reduced significantly, and a large stroke is achieved. The moving part (Slider) of this actuator is sandwiched between fixed electrodes (Stator), is alternately attached and detached to these fixed electrodes, and actuates linearly on a macroscopic level. Several difficulties have been identified regarding actuators operated by attachmen/ detachment. The interactive forces, including the accumulation of charge caused by contact between each slider and stator, create one of the most difficult problems. Our developed actuator incorporates micro stoppers, which prevent the accumulation of charge and other interactive forces on the surface of the slider or the stator. A voltage supply pattern such that the positive and negative charge appear alternately, is employed. The first prototype, casing size ...