Abstract: 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 E1<E2 and E3<E2 where E1 is the linear expansion coefficient of the thin film of organic material, E2 is the linear expansion coefficient of the adhesive and E3 is the linear expansion coefficient of the fixing substrate, and the glass transition temperature of the thin film of organic material being 150° or more, are selected.

Abstract: 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 E1<E2 and E3<E2 where E1 is the linear expansion coefficient of the thin film of organic material, E2 is the linear expansion coefficient of the adhesive and E3 is the linear expansion coefficient of the fixing substrate, and the glass transition temperature of the thin film of organic material being 150° or more, are selected.

Abstract: An optically anisotropic diffraction grating for an optical read/write head, comprising optically isotropic polymer liquid crystal held between two transparent base plates. Gratings of different refractive indexes are formed by periodically changing the orientation of the polymer liquid crystal of the diffraction grating. This enables a high light-utilization efficiency and a high reliability to be obtained.

Abstract: 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.

Abstract: An object is to provide an optical head device whereby the light utilization efficiency can be increased and which can be produced at a low cost. A glass substrate 1 having projections and recesses 2 formed by patterning a SiON type transparent thin film on its inner surface by dry etching, and a second glass substrate 3 having a polyimide film 4 formed as an alignment film on its inner surface, are laminated with a space, the periphery is sealed by a sealing material made of an epoxy resin 5, and liquid crystal 6 is injected under vacuum into the interior to form an optically anisotropic diffraction grating. On the outer surface of this second glass substrate 3, a quarter-wave film 7 is laminated, and a third glass substrate 9 is bonded by a photopolymer 8 to obtain a diffracting element 10. This diffracting element 10 is disposed between a light source and an optical recording medium to obtain an optical head device.

Abstract: High molecular liquid crystal obtained by photopolymerizing a liquid crystal composition which comprises CH2═CHCOO—X—OC6H4—C6H4CN (X is an alkylene group) and CH2═CHCOOC6H4—C6H4CN. 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.

Abstract: Swimming goggles that include a pair of lens assemblies each having an inner end portion formed with a recess and an end wall extending forward. A bridge is formed at each end with an outer leg, an inner leg and an intermediate leg. The outer leg is adapted to be firmly engaged with the recess of the lens assembly and cooperate with the inner leg to retain the end wall therebetween. The intermediate leg is adapted to be firmly engaged with a groove formed in the end wall. The swimming goggles thus constructed allow the bridge to be firmly engaged with the lens assemblies.

Abstract: An object is to provide an optical head device whereby the light utilization efficiency can be increased and which can be produced at a low cost. A glass substrate 1 having projections and recesses 2 formed by patterning a SiON type transparent thin film on its inner surface by dry etching, and a second glass substrate 3 having a polyimide film 4 formed as an alignment film on its inner surface, are laminated with a space, the periphery is sealed by a sealing material made of an epoxy resin 5, and liquid crystal 6 is injected under vacuum into the interior to form an optically anisotropic diffraction grating. On the outer surface of this second glass substrate 3, a quarter-wave film 7 is laminated, and a third glass substrate 9 is bonded by a photopolymer 8 to obtain a diffracting element 10. This diffracting element 10 is disposed between a light source and an optical recording medium to obtain an optical head device.

Abstract: A diving face mask including a lens, a main frame and a lens holding frame. The main frame and the holding frame are integrally interlocked together by first projections and second recesses arranged between an outer peripheral surface of the main frame and an outer edge of the holding frame covering this outer peripheral surface.

Abstract: A diving face mask comprises a purge valve assembly in a lower central area of a body frame. The purge valve assembly comprises a nose frame projecting from the body frame such that a V-shape cross-section is formed, a laterally elongated, and generally oblong valve which is configured to sit on a valve seat on a front wall of the nose frame for closing a laterally elongated, oblong opening passage. The purge valve assembly further comprises a nose cover having a configuration conforming to that of the nose frame for covering the nose frame, and a discharge opening defined between the nose frame and the nose cover.