Hiroaki Koyanagi

Optical head with optical beam control using acoustic wave device

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.

Optical and thermal analyses on multilayered thin films of a phase‐change optical recording disk

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...