Patents by Inventor Nobuo Imada

Nobuo Imada has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 6388976
    Abstract: A dichroic mirror of a polarized beam splitter is installed between a mirror and an objective lens as a beam synthesize/split means, in an optical system corresponding to a second dick and an optical system corresponding to a first disk arranged so as to form a two-layer structure. The dimension of the optical head in the width, length, and thickness directions are designed moderately.
    Type: Grant
    Filed: February 29, 2000
    Date of Patent: May 14, 2002
    Assignees: Hitachi, Ltd., Hitachi Media Electronics Co., Ltd.
    Inventors: Shinji Fujita, Hidenori Shinohara, Toshio Sugiyama, Nobuo Imada, Yukio Fukui
  • Patent number: 6069862
    Abstract: The dichroic mirror or a polarized beam splitter is installed between a mirror and an objective lens as a beam synthesize/split means, in an optical system corresponding to a second disk and an optical system corresponding to a first disk arranged so as to form a two-layer structure. The dimension of the optical head in the width, length, and thickness directions are designed moderately.
    Type: Grant
    Filed: December 12, 1997
    Date of Patent: May 30, 2000
    Assignees: Hitachi, Ltd., Hitachi Media Electronics Co., Ltd.
    Inventors: Shinji Fujita, Hidenori Shinohara, Toshio Sugiyama, Nobuo Imada, Yukio Fukui
  • Patent number: 5872761
    Abstract: The present invention comprises an arrangement with removable optical element having a predetermined focal distance in the light path between a light source and an objective lens, so as to insert said optical element into the light path between the light source and the objective lens for playing back or recording onto one type of thickness of disk plates, as well as to remove it therefrom for playing back or recording onto another type of thickness of disk plates. Alternatively, by retaining variably the distance between the light source and the collimator lens, the distance between the light source and the collimator lens along with the light path is variably changed according to the thickness of the disk plate being inserted. Then by determining the type of the disk inserted and accordingly selectably inserting/removing the optical element, only one objective lens may be used to conform to the disk plates having different thicknesses.
    Type: Grant
    Filed: August 28, 1997
    Date of Patent: February 16, 1999
    Assignee: Hitachi, Ltd.
    Inventors: Yasuyuki Sugi, Toshio Sugiyama, Nobuo Imada, Hidenori Shinohara, Yukio Fukui
  • Patent number: 5699341
    Abstract: The present invention comprises an arrangement with removable optical element having a predetermined focal distance in the light path between a light source and an objective lens, so as to insert said optical element into the light path between the light source and the objective lens for playing back or recording onto one type of thickness of disk plates, as well as to remove it therefrom for playing back or recording onto another type of thickness of disk plates. Alternatively, by retaining variably the distance between the light source and the collimator lens, the distance between the light source and the collimator lens along with the light path is variably changed according to the thickness of the disk plate being inserted. Then by determining the type of the disk inserted and accordingly selectably inserting/removing the optical element, only one objective lens may be used to conform to the disk plates having different thicknesses.
    Type: Grant
    Filed: September 11, 1996
    Date of Patent: December 16, 1997
    Assignee: Hitachi, Ltd.
    Inventors: Yasuyuki Sugi, Toshio Sugiyama, Nobuo Imada, Hidenori Shinohara, Yukio Fukui
  • Patent number: 5404344
    Abstract: A recording/reproducing optical head capable of causing a light spot on a photodetector for detecting a focusing error signal to stand still without being affected by variations in wavelength of light used, capable of adjusting a tracking error signal independently of the focusing error signal, and capable of utilizing light having an order of diffraction of -1 for the purpose of detecting a signal, in which a cylindrical lens for generating astigmatism and a diffraction grating made up of two regions different in the direction of diffraction or the angle of diffraction from each other are interposed between a beam splitter and a photodetector, a light beam diffracted from the diffraction grating and including the diffracted light of the zero-th order (that is, light which has passed through the diffraction grating without being deflected) is received by the photodetector, the diffracted light of the zero-th order is used for detecting a focusing error signal according to the astigmatism method, and diffracte
    Type: Grant
    Filed: November 19, 1993
    Date of Patent: April 4, 1995
    Assignee: Hitachi, Ltd.
    Inventors: Nobuo Imada, Kunikazu Ohnishi, Tohru Sasaki, Masayuki Inoue, Akira Arimoto, Shigeru Nakamura, Takeshi Nakao