Katsuji Hattori

Speaker system with image projection screen

A speaker system has an acoustic diaphragm and an image projection screen provided on a surface of the diaphragm integrally therewith so as to enable the user to enjoy both realistic image on the screen and powerful sound reproduced through the diaphragm. The rear surface of the diaphragm is closed at a peripheral portion thereof while the central portion of the rear surface of the diaphragm is opened to the exterior, so that the speaker system can provide a high level of reproduced sound pressure in low-pitched region, while the thickness of the speaker is reduced remarkably. The diaphgram can be driven by a plurality of driving units so that the speaker system can operate only with an ordinary stereophonic amplifier. The diaphragm can be composed of a pair of diaphragm elements capable of vibrating independently of each other and the screen may be integrally and commonly attached to the surfaces of these diaphragm elements in such a manner as to allow the diaphragm elements to vibrate independently of each other, whereby the speaker system can operate in stereophonic mode. Any variation in the acoustic characteristic attributable to variation in the condition of installation is compensated for by a change in the ratio of the opened area of the rear surface of the diaphragm to the whole effective vibration area or by a selective provision of a sound absorbing member on the rear side of the cabinet.

Fiber‐optic acoustic sensor using the Fabry‐Perot interferometer

A highly sensitive and compact butt‐coupled‐type fiber‐optic acoustic sensor has been developed based on the Fabry‐Perot interferometer (FPI) for use in remote sensing or sensing in narrow spaces. The system consists of a sensor head, a controller, and an optical fiber transmission line. The sensor head is based on the FPI, and is formed from the high‐reflectance‐coated confronting surfaces of an optical fiber and a diaphragm. The sensitivity of the sensor head is related to the finesse of the FPI. As the finesse increases, so does the sensitivity. To ensure system stability and increase the dynamic range, the controller is composed of a DFB laser diode with a wavelength of 1300 nm, double optical isolators, an automatic temperature controller, and an automatic power controller.

C-V Hysteresis Observed in a Splay-Bend Transition: a Novel Method for the Evaluation of a Transition Speed

Abstract The director distributions in thin nematic slabs with parallel structure have been calculated as a function of the applied electric field. They are different from the cells with the anti-parallel structure, in that three solutions exist in a specified voltage range which predict a transition of the director deformation from splay to bend configurations in the parallel structure. This splay-bend transition has been confirmed experimentally by a capacitance-voltage (C-V) hysteresis method. The C-V characteristics showed a hysteresis around the deformation transition and this magnitude corresponded to the facility of a splay-bend transition: a comparison of these hysteresis characteristics for different materials enables us to evaluate the splay-bend transition speed easily.