Hitachi, Ltd.

Hitachi Media Electronics Co., Ltd.

Hitoshi Yanagihara

Nobuhiro Tokushuku

Katashi Hazama

Masaaki Kurebayashi

Katsuo Konishi

Yoshihiko Noro

Masamichi Yamada

Jun Yamada

Takashi Shiba

Akitsuna Yuhara

Kiyoharu Kishimoto

Yoshie Kodera

Katsuyuki Tanaka

Toshio Tsuchiya

Masaki Yoshii

Masakatsu Saito

Michiyori Miura

Katsumi Itoh

Naotake Ebinuma

Kouichi Moritani

There is provided a surface acoustic wave device for use as a filter in a television receiver set which can reduce reflection waves generated from outermost electrodes of input and output interdigital transducers to improve various filter characteristics. In the surface acoustic wave device having, on a piezoelectric substrate, the input interdigital transducer for converting an electric signal into a surface acoustic wave and the output interdigital transducer, disposed to oppose the input interdigital transducer, for converting the surface acoustic wave resulting from the conversion by the input interdigital transducer into an electric signal, a first dummy electrode is provided to a first outermost electrode finger of the output interdigital transducer, the first outermost electrode finger being located at one end of the output interdigital transducer opposite to the input interdigital transducer, and having an electrode aperture length of .lambda./4 where n represents a wavelength of the surface acoustic wave, and a second dummy electrode is provided to a second outermost electrode finger of the input interdigital transducer, the second outermost electrode finger being located at one edge of the input interdigital transducer opposite to the output interdigital transducer, and having an electrode aperture length of .lambda./4.

Surface acoustic wave device

A video optical disk system which can record/reproduce information in the same recording format as that of a read only type optical disk such as an LD, and is therefore compatible with both the read only type optical disk and a writable optical disk. A writable optical disk exhibiting a C/N ratio of at least 60 [dB] is employed, and has information recorded thereon with the same address signals as those of the LD and in the NTSC direct FM recording format. An optical head and an image processing circuit which are included in a player unit are made common to the recorded disk and the LD, and characteristics of a focusing/tracking control circuit, an RF signal preamplifier circuit and a tilt control circuit which are included in the player unit are changed over on the basis of reflectances of both types of optical disks, thereby enabling both the recorded disk and the LD to be reproduced. The users of the optical disk system can produce original video software by themselves, and can effectively utilize a software stock of read only type optical disks.

Video optical disk system compatible with both read only and writable

The present invention relates to an optical information medium for recording and reproducing information optically. Particularly, it is concerned with a so-called sample servo type optical information medium wherein an optical head traces over the center line of an imaginary track on the basis of information obtained from at least a pair of wobble pits disposed on both sides of the said imaginary track center line. A continuous groove is formed between the paired wobble pits along the imaginary track center line in a certain area of the optical information medium so that the deviation of each wobble pit from the imaginary track center line can be easily grasped and the conditions of the wobble pits being formed can be estimated. The quality of the medium being manufactured can be easily judged by the presence of such continuous groove.

Optical information medium having paired wobble pitts with continuous

An optical disc consists of a base plate, a reflective thin layer, and a protective thin layer. The optical disc has a sample mark area having two sample marks, one of which is off-set on one side of a track, another of which is off-set at an opposite side of a track. These sample marks are produced by an injection molding with replica technique. At the time of the injection molding, additional pressure moves soft injected plastic resin, which causes double transcription of the sample marks. For preventing the double transcription, groove areas are provided on opposite sides of the sample mark area. The groove areas provide an anchor effect at the time of injection molding.

Optical information medium with sample mark area and multiple

In a thin film magnetic head consisting of a non-magnetic substrate, and a multilayer structure superposed thereon and including a lower core, a gap material layer, a thin film coil and an upper core, etc., the head sliding surface of the lower core and that of the upper core are so formed that they become wider with increasing distance from the surface of the gap material layer.

Thin film magnetic head

A surface acoustic wave device is provided with plural sets of input and output transducers arranged on a piezoelectric substrate with the input transducers and the output transducers being connected electrically in parallel, respectively. In order to minimize a loss which occurs due to the parallel connections of the input and output transducers, aperture dimensions of either the input transducers or the output transducers are selected such that static capacitances of the respective transducers are equal.

To eliminate disturbance signals caused by the reflection from the unitary stem areas of comb-like electrodes of an interdigital transducer in an elastic surface wave device, the edges of the unitary stem areas perpendicular to the surface wave propagating direction includes at least one pair of partial edges, the positions of the partial edges in each of the at least one pair of partial edges differ by (2n+1).multidot..lambda./4 from each other in the surface wave propagating direction, and the lengths of the partial edges in the each pair are equal to each other, where n represents zero or a positive integer and .lambda. represents the wavelength of the elastic surface.

Elastic surface wave device

Growing community of inventors

Kamakura, Japan

Hitoshi Yanagihara