Abstract: The present invention relates to a rotary encoder for detecting a rotational angle. A rotary encoder according to the present invention comprises a rotating body provided on its surface with a plurality of digital code patterns representative of absolute angle ranges and a plurality of relative angle patterns representative of relative angles, a high-order angle data producing means (1,2,5,7) for reading the absolute angle patterns to produce high-order angle data, and a low-order angle data producing means (1,2,5,7) for reading the relative angle patterns to produce low-order angle data. The rotary encoder according to the present invention ensures medium resolution by means of the digital code patterns and attains finer resolution by means of the relative angle patterns, whereby the rotational angle can be detected with superior resolution.

Abstract: A passive tank stabilizer is mounted on a watergoing vessel in the athwartship direction for counteracting the roll of the vessel so that the vessel can be stabilized. The passive tank stabilizer comprises at least two tanks or two holders obtained by dividing one tank into two parts, with the tanks or the holders having different space volume and containing quantities of stabilizing liquid such as water. The passive tank stabilizer is capable of producing stabilizing effects over a wide range of roll frequencies of the vessel.

Abstract: The present invention is directed to a gyroscopic instrument comprising concentric containers, the inner container enclosing a rotating electric gyro rotor, magnetic fluid enclosed between the inner and outer concentric containers, and magnetic flux producing means mounted on at least one of the two concentric containers, so that magnetic fluxes reach the magnetic fluid to support the inner container without contacting the outer container. The magnetic flux producing means are preferably mounted and oriented on a line drawn on at least one of the concentric containers at predetermined distances so that magnetic fluxes transmitted from the pole of one flux means reach the opposite pole of an adjacent means by passing through the magnetic fluid.

Abstract: An ultrasonic detection system having an array of ultrasonic transducers that are uniformly closely disposed relative to each other such that the active surfaces for transmission or reception are maintained on a straight or curved line. The transducers form radiation or reception beams in a specific direction. Beam orientation is accomplished by selecting a group of transducers from the array and/or respectively applying appropriate phase-shifts to the signals to be fed to each of the transducers or to the signals produced from each of the transducers. Shields are maintained between two adjacent transducers for suppression of sidelobes.

Abstract: A gravity stabilized drive mechanism varies the orientation of an underwater ultrasonic transducer in both azimuth and elevation while stabilizing the transducer against the pitching and rolling of a ship. The transducer is freely suspended by a universal joint from a vertical tilt control shaft. The tilt control shaft passes through a hollow azimuth control shaft which, in turn, is rotatably mounted on a platform attached to the ship. Elevation of the transducer is adjusted by rotating the tilt control shaft, and azimuth of the transducer is adjusted by rotating the azimuth control shaft.

Abstract: Scanning angle control for a linear array of spaced transducers in a pulse echo receiver is implemented by mixing the respective transducer outputs with progressively shifted output signals from a multi-stage, variable phase shifter fed by a local oscillator. The additively combined mixer outputs thus contain frequency sum and difference components, which are extracted by low or high pass filters to implement scanning control on either side of a perpendicular to the array. When a two dimensional array of transducers arranged in a row and column coordinate grid is employed, scanning in both azimuth and elevation may be implemented by coupling each column of transducer mixers to the respective phase shifter stages through digital delay circuits arranged in rows and fed by a variable frequency clock pulse generator, whereby progressive delays are provided in the columnar direction.