Hitachi, Ltd.

Yooji Maruyama

Takeshi Shimano

Kenchi Ito

Hiroyuki Awano

Kazuhisa Fujimoto

Ryo Imura

Yutaka Sugita

Yoshito Tsunoda

Naoki Koyama

Hiroshi Umezaki

An optical head including a semiconductor laser source, a condenser lens, a photodiode for detecting a laser light emitter from said semiconductor laser source, and an optical coupler unit for collecting the laser light to the photodiode. A chromatic aberration W of condenser lens is satisfied by an expression W(h, NA)&equals;&lcub;(NA) &Dgr;&lgr;/4&lgr;&rcub;h, where h is a height of incident light from an optical axis on a hologram, NA is a numerical aperture, &Dgr;&lgr; is a wavelength fluctuation, and a &lgr; is a wavelength at recording. The height h is determined so that the chromatic aberration W becomes equal to or less than &lgr;/4.

Flying type optical head integrally formed with light source and photodetector and optical disk apparatus with the same

The optical head is arranged such that a semiconductor laser and a photodetector are formed via a buffer layer on the same substrate; and an opening portion is formed in the substrate under the semiconductor laser and the photodetector. This optical head is further arranged by that the opening portion is filled with a first transparent layer; a diffraction grating is formed on a lower surface of the first transparent layer; a second transparent layer is stacked on a lower surface of the first transparent layer; and a condenser lens is formed on a lower surface of the transparent layer. In this optical head, laser light emitted from the semiconductor laser is penetrated through the substrate, the first transparent layer, the diffraction grating, and the second transparent layer, and condensed toward a place just under the condenser lens by the condenser lens, thereby forming a light spot on an optical storage medium positioned apart from the condenser lens, whereas reflection light reflected from the optical storage medium is penetrated through the condenser lens and the second transparent layer, diffracted by the diffraction grating toward a light receiving plane of the photodetector, and further penetrated through the first transparent layer to be received by the photodetector.

Flying type optical head integrally formed with light source and

An information recording and reproducing apparatus which has a memory portion which uses the Bloch lines occurring at the magnetic domain walls at the periphery of magnetic domains present in magnetic garnet films as the information carrier, a drive portion to write information into or read information from the said memory portion, and in which the memory portion is constructed to be connectable to and disconnectable from the drive means, wherein the signal transfer is carried out via a connection means when the said memory portion is set in the drive portion. In this information recording and reproducing apparatus, since the recording portion can be freely connected to or disconnected from the drive portion, it is possible to selectively insert portable substrates storing different information in the same apparatus body portion.

Information recording and reproducing apparatus

In a solid state magnetic memory device wherein the information storing region of a Bloch line memory device using Bloch lines generated in magnetic domain walls as information carriers is covered with a magnetic material film having stripe domains perpendicular to the magnetic domain walls, the information storing position is determined by the stripe domains and a memory density of more than several tens giga bits per cm.sup.2 can be realized.

Solid state magnetic memory device

A magnetic bubble memory device comprises an ion-implanted region for information storage formed in a surface of a magnetic material layer and a permalloy transfer path formed near an ion implantation transfer path defined by the edge of the ion-implanted region for reading information from the ion implantation transfer path or writing information in the ion implantation transfer path. The ion implantation depth in a portion of the ion-implanted region near the permalloy transfer path is continuously changed to provide an inclined edge of the ion-implanted region.

Growing community of inventors

Iruma, Japan

Yooji Maruyama