This paper describes development of electromagnetically-driven 2-axis MEMS mirror which steers an optical beam, and dependences of tilting angles on magnet shape, size and initial gap of planar coils - magnet surface. A reflective Au mirror (1.8×1.8mm2) can be tilted bi-directionally with electromagnetic force induced by current of planar coils and magnetic field of a permanent magnet. A developed MEMS mirror device (10×10×t0.2 mm3) was set on a printed circuit board (15×15×t1.0 mm3), and the board was fixed on a holder in which a magnet was inset. Utilized magnets were cubic ( 6, 8, 15mm and 5mm thick), cylindrical (φ6, φ8mm and 5mm thick) and spherical (diameter 8mm) for investigating efficient actuation. Initial gaps of planar coils and magnet surface were 0, 500, 1000 and 2000μm. Magnetic flux density and its gradient decreased with distance from magnet surface. Tilting angles of MEMS mirror increased with smaller square magnet and shorter distance, and were largest by using 6mm magnet and 500μm gap in which condition maximum tilting angle toward X and Y direction were 2.95 and 3.68 deg./mA, respectively. In addition, we have obtained 3D-OCT images of human finger tissue by using a Fourier domain fiber interferometer with a developed MEMS mirror.
We propose a new 2- axis electromagnetic scanning mirror that utilizes radial magnetic fields. By positioning magnets under the mirror, we were able to develop a greatly miniaturized mirror device. This device volume is 300 mm3. Moreover, the mirror driving magnetic induction can be enlarged by forming the closed magnetic field with the york and the magnets. To assemble it easily, the upper part of all magnets was assumed to be N pole. To optimize the composition of the yoke and the magnets, the magnetic induction of the space was calculated using magnetic simulation. We made the mirror using the bulk micromachining process, and did the driving experiment. The mirror scanning angle is 10 degrees at 100 mAP-P for a resonant frequency of 6 kHz, and the frame scanning angle is 1 degree at 100 mAP-P for a non-resonant frequency of 60 Hz. The calculation and the measurement result were almost the same.
We have developed a novel debris-free low-stress high-speed laser-assited dicing technology for multi-layered MEMS wafers, which generally consist of glass and Si. Our technology combines two processes: fabrication of dicing guidelines and wafer separation process. The first process is an internal transformation using a pulsed 1μm laser. The second process is non-contact separation by thermally-induced crack propagation using a CO2 laser or mechanical separation by bending stress. We tested several pulsed lasers with different pulsewidths, including a Nd:YVO4 laser and an Yb fiber laser for generating the internal transformation in Si and/or glass. The internal transformed lines worked well as a guide of the separation. We found that internal transformation only in the Si layer was enough for dicing the glass/Si double-layered wafers. Also the thermal stress induced by the CO2 laser was quite effective in propagating the crack inside the glass layer without internal transformation. The double-layered wafer consisting of glass and silicon can be diced with low stress by our technology.
For the multiplication of sensor output voltage, series-connected PZT elements are proposed. The series-connected PZT device is successfully fabricated using dry-etching process of PZT. To validate the multiplication, the output voltages are measured when the device is vibrated. The output voltage of eight series-connected PZT elements roughly corresponds to the sum of the output voltage obtained from each single element. Using circuit simulator, SPICE, the influence of the parasitic capacitances is investigated. The calculated output voltages are in excellent agreement with the measured ones. Reducing the parasitic capacitances properly, the output voltage is linearly multiplied with the number of series-connection.
Recently, a new flexible structure made of a single-crystal silicon substrate has been reported from a Stanford group. The structure consists of many isolated islands and extremely thin silicon springs connecting those silicon islands. Their technique seems very innovative since single crystalline silicon has been regarded to be solid and never flexible. In this paper, it will be reported that a different flexible structure with a 6-fold rotational symmetry was designed. The flexibly deforming single-crystal silicon network consisting of silicon islands, each of which has three spiral springs, has been successfully fabricated. The structure was expanded to wrap a hemisphere with the diameter 10 mm. The 120 silicon islands, which were contained in the silicon network, were nearly uniformly distributed on the hemisphere. This technique may be useful if there are needs to uniformly distribute small silicon devices on a structure such as a fingertip.
In this paper, a non-resonant 2D micro optical scanner with extremely large optical scan angle has been reported for wide field of view in a LASER application. Two pairs of permanent magnets are mounted on the Si mirror and supporting gimbal structure, respectively, to generate large tilting angle without a thermal degradation of the driving property. The scanner can be driven in two- axis independently by a rotational magnetic torque using orthogonal oriented external electromagnets. The maximum optical scan-angle of 118 degree has been achieved with applying 120mA to the electromagnet.
The three events to the window and the key occurring when a thief attempts to intrude into the house are detected by the different sensors conventionally. This paper proposes a method detecting the three events by using the simple light-sensor consisting of an infrared LED and a photodiode. In the experiments, the light sensor shows the different tendencies that can detect each event. This fact indicates that our proposal can realize a sensor module more efficiently instead of using different sensors.