Hitachi, Ltd.

Hoya Corporation

Yoshihiko Noro

Jun Yamada

Nobuhiro Tokushuku

Masaaki Kurebayashi

Katashi Hazama

Hitoshi Yanagihara

Kenji Hayashi

Satoshi Kobayashi

Makoto Miyamoto

Shigemitsu Higuchi

Takanori Hisada

Takesuke Maruyama

Tadashi Saito

Manabu Wakabayashi

Tohru Sampei

Masaharu Deguchi

Yoshie Kodera

Katsuyuki Tanaka

Katsuo Konishi

Kazutoshi Konno

Yoshio Ariki

Shunichi Taguchi

Michiyori Miura

Shiro Takahashi

Hisanori Suzuki

Yoshifumi Honma

Kouichi Moritani

Naomi Suzuki

An optical waveguide apparatus comprises a substrate ( ), a patterned waveguide as a core ( ), and an upper cladding layer ( ) formed on the substrate. The core is surrounded by a cladding comprising the substrate as a lower cladding layer and the upper cladding layer and smaller in refractive index than the core. The core and the cladding are integrally coupled to each other in a manner such that temperature-dependent expansion or contraction is performed substantially in accordance the characteristic of the cladding. The core and the cladding are made of materials selected so that the variation in optical path length according to the temperature-dependent expansion or contraction of the cladding is canceled by the variation in optical path length according to temperature-dependent variation in refractive index of the core.

Optical waveguide apparatus and method of producing the same

A recording apparatus includes a recording medium, a frequency modulator for conducting frequency modulation on a digital-modulated signal to generate a recording signal, and a recording unit for recording the recording signal on the recording medium.

Recording/reproducing apparatus including frequency modulator for

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

A light scanning system employing a rotating mirror, spherical lens, and a toric-surfaced reflecting mirror. The toric-surfaced reflecting mirror is disposed in the optical path between the spherical lens and the image plane. The spherical lens sufficiently corrects field curvature and the toric-surfaced reflecting mirror corrects scan nonlinearity. And by the spherical lens and the toric-surfaced reflecting mirror together, the field curvature and the scan nonlinearity are satisfactorily corrected. The toric-surfaced reflecting mirror is surfaced to have a circular arc with a larger radius of curvature in the scan plane and to have a circular arc with a smaller radius of curvature in the cross-scan plane.

Light scanning system

A tracking servo system for a magnetic recording and reproducing apparatus uses a flexible magnetic disk having thereon at least first, second and third tracks each of which includes a data track portion and a pair of servo track portions located on both sides of the data track portion. Tracking signals having different frequencies are recorded on the first, second and third servo track pairs. Servo and data heads are formed in a unitary structure. When the data head records an information signal on the second data track portion or reads out the recorded information signal therefrom, the servo head reads out the tracking signals recorded on the first and third servo track portions.

Tracking servo system for magnetic recording and reproducing apparatus

An elastic surface wave filter for use as an intermediate frequency filter in a color television receiver, comprising an input electrode provided on a piezoelectric substrate plate for converting an electric signal into elastic surface waves propagating through the surface layer of the piezoelectric substrate plate, a propagation path for the elastic surface waves in the piezoelectric substrate plate and an output electrode for converting the propagated elastic surface wave into an electric signal, wherein the fingers of the input electrode are so arranged that the position at which the overlap of the interleaved fingers is maximum is farther with respect to the output electrode than the middle point along the lengthwise direction of the input electrode and wherein the pitch between the adjacent interleaved fingers is non-uniform on both the sides of the position of the maximum overlap, whereby desired group delay and amplitude characteristics for predetermined frequencies are easily and simultaneously obtained.

Elastic surface wave filter

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

Yokohama, Japan

Yoshihiko Noro