Asahi Glass Company, Limited

Yuzuru Tanabe

Hiromasa Sato

Yoshiharu Ooi

Tomoki Gunjima

Hiroki Hotaka

Takuji Nomura

Mitsuo Oosawa

Koji Ikawa

Masahiro Murakawa

Naomitsu Umemura

Ryuichiro Shimizu

Takehiko Nishiyama

Tomohiro Sakai

Kazuo Sunahara

Hiroshi Usui

Iori Yoshida

Yoshihisa Beppu

Satoshi Kashiwabara

Kara Yoshida

Yoshinori Kon

Katsuaki Miyatani

Osamu Miyahara

Toshimasa Kakiuchi

Nobuhiko Takeshita

Kouichi Murata

Mitsuru Kurosawa

Mitsuru Horie

Motoichi Ohtsu

Tadanori Senoh

A method for producing a glass substrate for a magnetic disk by polishing a circular glass plate, which comprises a step of polishing the principal plane of the circular glass plate by using a slurry containing a CeOcrystal powder, the CeOcrystal powder being obtained in such a manner that a melt containing CeOis quenched to obtain an amorphous material, and the amorphous material is subjected to heat treatment to obtain a CeOcrystals-precipitated amorphous material, which is subjected to acid treatment to separate and extract the CeOcrystal powder from the CeOcrystals-precipitated amorphous material.

Method for producing glass substrate for magnetic disk, and magnetic disk

A liquid crystal lens element capable of finely adjusting focal length according to the magnitude of applied voltage, and an optical head device employing such a liquid crystal lens element, are provided. On one surface of a transparent substrate, a transparent electrodeand a concave-convex portionmade of a transparent material having a cross section shape approximated by a saw-tooth shape, are formed so as to constitute a plurality of annular portions, and on one surface of a transparent substrate, a transparent electrodeis formed. The transparent electrodesandconstitute annular divided electrode segments, and division positions of the annular electrode segments are made to be agree with division positions of annular portions of the saw-tooth-shaped concave-convex portionof the transparent substrate

Liquid crystal lens element and optical head device

A liquid crystal lens element is provided, which does not produce change of transmission wavefront regardless of polarization state of incident light when it is off-state at a time of no voltage application, and which exhibits concave lens function for extraordinarily polarized incident light when it is on-state at a time of voltage application. In a liquid crystal lens elementcomprising a pair of transparent substratesandand a liquid crystal layersandwiched between the transparent substrates, which is configured to change convergent point of light transmitted through the element according to the magnitude of voltage applied to the liquid crystal layerthe liquid crystal lens elementfurther comprises a Fresnel lenshaving a concave-convex-shaped cross section formed on the transparent substrate, a first transparent electrodeformed on a flat surface of the transparent substrateon which the Fresnel lensis formed, and a second transparent electrodeformed on a flat surface of the other transparent substrate

Liquid crystal lens element optical head device

The present application relates to a liquid crystal lens element and an optical head device, in particular order, to a liquid crystal lens capable of switching the focal length among a plurality of different focal lengths according to switching of applied voltage among a plurality of applied voltages, and an optical head device employing the liquid crystal lens, for writing and/or reading an information to/from an optical recording medium.

To provide optical elements such as a phase plate suitably used in a broadband range and a polarizing diffraction element excellent in diffraction efficiency, a polymerizable liquid crystal composition to be used for them, and an optical head device using them. A polymerizable liquid crystal composition containing a polymerizable compound having a mesogen structure comprising the following condensed benzene ring group (A) and the following 6-membered cyclic group (B) bonded to at least one bond in the group (A) directly or via a connecting group &#x2014;OCO&#x2014; or &#x2014;COO&#x2014;, and a monovalent terminal group bonded to each of both terminals of the mesogen structure, at least one of the terminal groups being a monovalent organic group having a polymerizable moiety:

Polymerizable liquid crystal composition, optical anisotropic material, optical element and optical head device

A liquid crystal lens element having a lens function is provided, which is small sized without having moving part, and which can stably carry out correction of spherical aberration containing a power component corresponding to focal point change of incident light. A liquid crystal lens element which changes a focal length of light transmitted through a liquid crystalaccording to the magnitude of the voltage applied to the liquid crystalsandwiched between a pair of transparent substratesand, which comprises transparent electrodesandprovided on the respective transparent substratesandfor applying a voltage for the liquid crystal, and a concave-convex portionhaving a saw-tooth-shaped cross-sectional shape having a rotational symmetry about an optical axis and formed on one surface of the transparent electrodewith a transparent material, wherein at least concave portions of the concave-convex portionare filled with the liquid crystalso as to change the substantial refractive index of the liquid crystalaccording to the magnitude of applied voltage.

An adhesive is coated on at least one surface of a thin film of organic material having birefringent properties and a phase-difference producing function, and a fixing substrate having transmitting or reflecting properties is bonded to the thin film of organic material by the adhesive, wherein materials satisfying relations of E&#x3c;Eand E&#x3c;Ewhere Eis the linear expansion coefficient of the thin film of organic material, Eis the linear expansion coefficient of the adhesive and Eis the linear expansion coefficient of the fixing substrate, and the glass transition temperature of the thin film of organic material being 150&#xb0; or more, are selected. With such structure, temperature characteristics of a phase difference can be obtained so as to reduce a temperature change of an oscillated wavelength emitted from a semiconductor laser source whereby the phase difference can be kept constant even when there is a fluctuation in a wavelength of light emitted from the semiconductor laser source due to temperature.

Retarder and optical head device installing the same

Phase shifter and optical head device mounted with the same

As an optically anisotropic diffraction grating in an optical head for reading and/or writing of an optically recording medium, optically anisotropic diffraction grating which comprises an optically anisotropic polymer liquid crystal sandwiched between two transparent substrates are used. The optically anisotropic polymer liquid crystal can have an alignment direction periodically changed to form a grating of different refractive indices, obtaining a high-utilization efficiency by light ray and a high degree of reliability.

Optical head, method of manufacturing the same, and diffraction element suitable therefor

Optical head device including an optically anisotropic diffraction grating and process for its production

High molecular liquid crystal obtained by photopolymerizing a liquid crystal composition which comprises CH,&boxH;CHCOO&mdash;X&mdash;OC,H,&mdash;C,H,CN (X is an alkylene group) and CH,&boxH;CHCOOC,H,&mdash;C,H,CN. An optical element which is a polarized hologram element made by using the high molecular liquid crystal and an optical head having the polarized hologram element as a beam splitter.

Liquid-crystal composition and polymeric liquid crystal obtained by polymerizing the same

Optical head device including an optically anisotropic diffraction

A harmonic wave generator comprises a semiconductor laser for generating a fundamental wave and a KNbO.sub.3 crystal which transforms the fundamental wave to a harmonic wave, wherein the KNbO.sub.3 crystal is provided with electrodes for applying an electric field to a pair of opposing surfaces of the crystal.

Harmonic wave generator, a method of producing a harmonic wave and a

An optical information readout system including a record medium having a record layer capable of storing information and of reading the same optically, a resonating mirror arranged in substantially parallel to and apart at a predetermined distance from the record medium, a laser medium arranged between the record medium and the resonating mirror, a light source for pumping the laser medium, and a detector for detecting changes in a laser resonance, wherein the information recorded in the record medium is read by utilizing the surface of the recording medium as the other resonating mirror of the laser resonator and by detecting the changes of laser resonance resulted from the changes of the record medium surface by the detector.

Optical information readout apparatus

A temperature-measuring method comprises inputing laser pulses into an optical fiber to be measured and measuring temperature distribution in the fiber from the ratio of the amplitudes and the delay time of Stokes light and anti-Stokes light contained in the return beam from the optical fiber, wherein the temperature distribution is measured by using equations: ##EQU1## where T(x) is temperature to be measured, .THETA. is the reference temperature, R' (T) is the relative ratio of amplitude at the measuring point, R' (.THETA.) is the relative ratio of amplitude at the reference temperature point, k is Boltzmann's constant, h is Planck's constant, c is velocity of light, .nu. is Raman shift, .alpha. is distance, wherein the attenuation difference .alpha. is represented by a function .alpha.{T(.tau.)} dependent on temperature T(.tau.) at the measuring point .tau., and the exponential function in which the exponential part is represented by a value obtained by integrating the function .alpha.{T(.tau.)} with the variation d.tau. in distance, is employed as a correction factor.

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Chiyoda-ku, Japan

Yuzuru Tanabe