Hiroaki Koyanagi
Hitachi
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Publication
Featured researches published by Hiroaki Koyanagi.
Journal of the Acoustical Society of America | 1990
Norifumi Miyamoto; Yoshio Sato; Nobuyoshi Tsuboi; Satoshi Shimada; Hiroshi Sasaki; Hiroaki Koyanagi; Hiroyuki Minemura
An optical head is disclosed, in which a plate-shaped optical wave guide comprises an optical system including a collimator lens, a beam splitter and an objective lens; a laser light source for emitting a laser light in the form of a light beam which is to be impinged on an optical recording medium; and electro-acoustic transducers are disposed between the beam splitter and the objective lens, the transducers being adapted to be driven by the outer electrical signal for producing surface acoustic waves in the optical wave guide, thereby establishing a condensation and rarefaction distribution in refractive index in the optical wave guide which distribution influences the direction of transmission and the degree of focusing of the light beam passing therethrough so that regulation of the tracking and the focal length can be effected without any mechanical movements.
Journal of Applied Physics | 1989
Hiroaki Koyanagi; Tetsuo Ito; Norifumi Miyamoto; Yo Sato; Hisashi Ando
A computer simulation method to study a laser‐induced transient temperature profile of a multilayered phase‐change optical recording disk (PCORD) has been developed. The simulation program consists of two parts. One part is an optical analysis program based on the optical characteristic matrix method, and the other is a thermal analysis program based on the finite‐element method. A new estimation method for thermal conductivity of recording films was proposed. The estimated thermal conductivity of the thin‐film recording media was found to be 50% lower than that of the bulk. Reflectivity, absorbance, and temperature values obtained with this simulation method were compared with those measured by a spectrophotometer and an infrared radiation thermometer when the samples were irradiated in an Ar+ laser beam. The accuracy using this simulator was within 8% for reflectivity and absorbance and within 10% for temperature. A method of optimizing the laser‐absorbing layer was studied. With this method simulations...
Archive | 1990
Tetsuo Ito; Hiroshi Sasaki; Yoshio Sato; Satoshi Shimada; Norifumi Miyamoto; Nobuyoshi Tsuboi; Hideki Nihei; Hiroaki Koyanagi
Archive | 1990
Masahiko Ibamoto; Yasuo Morooka; Hiroaki Koyanagi; Manabu Sato; Takeshi Mizumura
Archive | 1989
Hiroyuki Minemura; Yoshio Sato; Nobuyoshi Tsuboi; Hiroaki Koyanagi; Shinji Ohyama
Archive | 1985
Yoshio Sato; Satoshai Shimada; Hiroshi Sasaki; Norifumi Miyamoto; Nobuyoshi Tsuboi; Hideki Nihei; Ryuji Watanabe; Atsumi Watanabe; Tetsuo Ito; Hiroaki Koyanagi
Archive | 1991
Yoshio Sato; Atsumi Watanabe; Satoshi Shimada; Hiroshi Sasaki; Nobuyoshi Tsuboi; Hideki Nihei; Norifumi Miyamoto; Hiroaki Koyanagi; Hiroyuki Minemura
Archive | 1988
Satoshi Shimada; Shinji Ohyama; Manabu Sato; Masahiko Ibamoto; Yoshio Sato; Nobuyoshi Tsuboi; Norifumi Miyamoto; Hiroyuki Minemura; Hiroaki Koyanagi
Archive | 1995
Akira Taniyama; Makoto Morijiri; Haruko Tanaka; Isamu Yuito; Eiji Ashida; Hiroaki Koyanagi; Hideo Tanabe; Tetsuo Kobayashi
Archive | 1992
Shigeru Tadokoro; Shinji Narishige; Hiroaki Koyanagi; Tetsuo Kobayashi