This paper proposes a method to distinguish the key-type of human fingers attached with the small permanent magnets. The Hall sensors arrayed in the credit card size area feel the distribution of the magnetic field due to the key-typing movement of the human fingers as if the keyboard exists, and the signal is analyzed using the generic algorithm or the neural network algorism to distinguish the typed keys. By this method, the keyboard can be miniaturized to the credit card size (54mm×85mm). We called this system `The virtual keyboard system'.

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The wireless smart sensors have been proposed not only for high-risk and chronically ill patients but also in the healthcare field. The radio frequency (RF) transmitter is necessary to fabricate wireless smart sensors. This paper presents a proposal of the complementary metal-oxide-semiconductor (CMOS) RF transmitter using pulse width modulation (PWM) method. The major advantage of the PWM is a performance with low consumption power. In this paper, we designed and simulated the circuitry for the transmitter. The proposed transmitter consists of pulse width modulator, oscillator and on-chip antenna. With the transmitter using PWM method, it will be possible that wireless smart sensor perform with lower power consumption than the RF transmitter using conventional ring oscillator.

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A diaphragm-type optical fiber pressure sensor, which has a sleeve for fiber insertion, is proposed and the fundamental characteristics of this sensor is demonstrated. The sleeve structure is fabricated by DRIE (Deep Reactive Ion Etching). The diaphragm with a sleeve is suitable for high reliable and easy bonding between the sleeve and the optical fiber. The light intensity change by the Fabry-Perot interferometer according to the pressure is increased by the improved DRIE method. The mass production method of the developed diaphragm will be useful to realize a low cost pressure sensor.

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A novel eddy current testing probe composed of double uneven step distributing planar coils is researched to be used in crack detection. Because of the novel coil structure, the probe can not only detect the crack existence but also the crack position directly and quickly in measurable range of test metallic surface in non-scanning detection mode. This static crack detection can reduce measurement work and advance test efficiency greatly compared with traditional dynamic crack detection by scanning. The eddy current sensor using this probe can realize the line detection for defects which is improved from the traditional point detection. Experimental results show that in crack detection the difference inductance of double probe coils is approximately linear with crack position in measurable range. Through curve fitting of the dependence of difference inductance on crack position based on the least squares principle, finally a formula of crack position estimation is deduced, and its estimation error is studied.

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In a bathroom and a toilet, a security camera cannot be used for the conservation of privacy. In order to solve the problem, a sensing system using infrared sensors arranged at grid is proposed in this study. From the output of infrared sensors, human's state is judged. As the result, the human's state is recognized at high accuracy. This system does not use the image focused by lens like a camera and infrared sensor-array.

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