Abstract: An optical element of this invention converts incident light having a predetermined shape and a predetermined intensity distribution into output light having a desired shape and a uniform intensity distribution. Furthermore, in an optical device of this invention, which has this optical element as a first optical element, a light source radiates a light beam having the predetermined beam shape and the predetermined intensity distribution, the first optical element shapes the beam shape of the incident light beam into one of rectangular, circular, and elliptic shapes having a uniform intensity distribution, and a second optical element gives a collimation to the incident shaped light beam.

Abstract: An optical disk with sectional trapezoidal pits comprising a substrate having information recorded by a plurality of pit trains formed thereon at a specified track pitch, and a reflective layer formed on the substrate, wherein the information is reproduced by being irradiated with light beam via an objective lens, the track pitch is set within the range of (0.72 to 0.8) .alpha..times..lambda./NA/1.14 .mu.m when a wavelength of the light beam is .mu. nm and a numerical aperture of the objective lens is NA, each of the pits is a multiplication ratio used to secure allowable disk tilt angles in an upper width within the range of (0.3 to 0.50) .alpha..times..lambda./NA/1.14 .mu.m, a bottom width within the range of (0.2 to 0.32) .alpha..times..lambda./NA/1.14 .mu.m and a depth within the range of (1/4.2.times..lambda./n) to (1/5.2 .lambda./n) (n: refractive index of said substrate and .lambda.: a wavelength) and obtained by 2.623.times.10.sup.-7 .times.(d/.lambda.).sup.2 -1.706.times.10.sup.-4 (d.sub.s /.lambda.

Abstract: An optical disk with sectional trapezoidal pits comprising a substrate having information recorded by a plurality of pit trains formed thereon at a specified track pitch, and a reflective layer formed on the substrate, wherein the information is reproduced by being irradiated with light beam via an objective lens, the track pitch is set within the range of (0.72 to 0.8) .alpha..times..lambda./NA/1.14 .mu.m when a wavelength of the light beam is .mu.nm and a numerical aperture of the objective lens is NA, each of the pits is a multiplication ratio used to secure allowable disk tilt angles in an upper width within the range of (0.3 to 0.50) .alpha..times..lambda./NA/1.14 .mu.m, a bottom width within the range of (0.2 to 0.32) .alpha..times..lambda./NA/1.14 .mu.m and a depth within the range of (1/4.2.times..lambda./n) to (1/5.2 .mu./n) (n: refractive index of said substrate and .lambda.: a wavelength) and obtained by 2.623.times.10.sup.-7 .times.(d/.lambda.).sup.2 -1.706.times.10.sup.-4 (d.sub.s /.lambda.)+0.

Abstract: An optical recording medium, which has a land and a groove on which a record mark is formed, comprises a transparent substrate, an inner protection layer formed on the substrate, a recording material layer formed on the inner protection layer and a reflection layer formed on the outer protection layer. The groove is formed to have a depth of .lambda./6 and the ratio of the thickness of the outer protection layer to the thickness of the recording material layer is set in a range between 0.8 and 1.2.

Abstract: An optical disk comprises a substrate, and a recording layer which is formed on the substrate and on which information is recorded at specific pitches in the form of pit trains, wherein the information is reproduced by projecting a light beam via an object lens, and when the wavelength of the light beam is .lambda. .mu.m and the numerical aperture of the object lens is NA, the track pitch is set in the range of (0.72 to 0.8).times..lambda./NA/1.14 .mu.m, and each of the pits has a trapezoid cross section whose upper width is in the range of (0.3 to 0.5).times..lambda./NA/1.14 .mu.m and whose lower width is in the range of (0.2 to 0.32).times..lambda./NA/1.14 .mu.m or whose inner wall has an angle of 30.degree. to 70.degree..

Abstract: An optical information reproducing apparatus according to the present invention optically reproduces information from a recording medium on which the information is recorded as a mark string, and comprises irradiation section for irradiating a light beam onto the recording medium through an object lens, and signal processing section for detecting diffraction light from the recording medium as a reproducing signal and processing the obtained reproducing signal to reproduce the information recorded on the recording medium. With this configuration, the signal processing section includes a transversal filter having delay section with a plurality of taps for receiving the reproducing signal, and section for performing weighted addition of output signals from the respective taps of the delay section with predetermined tap coefficients, the transversal filter having a delay time g between the respective adjacent taps, the delay time g being given by one of .tau.=(0.37 to 0.51).times..lambda. / (v.times.NA) and .tau.

Abstract: An optical head device adapted to be optically coupled to an optical disk includes a light-source laser and an objective lens optically coupled thereto. This lens receives an output light of the light source, and causes it to be projected onto the optical disk to form a focused spot thereon. Photodetectors which are arranged near the light-source laser are optically coupled to the lens in one optical path so that they are responsive to a light component which is reflected from the optical disk toward the photodetectors by way of the objective lens. A beam-shaping prism is located between the lens and a group of the light source and the photodetectors in the optical path. When the laser output light travels toward the lens, the prism reshapes the light into a predetermined isotropic beam profile.

Abstract: An optical disk with sectional trapezoidal pits comprising a substrate having information recorded by a plurality of pit trains formed thereon at a specified track pitch, and a reflective layer formed on the substrate, wherein the information is reproduced by being irradiated with light beam via an objective lens, the track pitch is set within the range of (0.72 to 0.8).alpha..times..lambda./NA/1.14 .mu.m when a wavelength of the light beam is .mu. nm and a numerical aperture of the objective lens is NA, each of the pits is a multiplication ratio used to secure allowable disk tilt angles in an upper width within the range of (0.3 to 0.50).alpha..times..lambda./NA/1.14 .mu.m, a bottom width within the range of (0.2 to 0.32).alpha..times..lambda./NA/1.14 .mu.m and a depth within the range of (1/4.2.times..lambda./n) to (1/5.2 .lambda./n) (n: refractive index of said substrate and .lambda.: a wavelength) and obtained by 2.623.times.10.sup.-7 .times.(d/.lambda.).sup.2 -1.706.times.10.sup.-4 (d.sub.s /.lambda.)+0.

Abstract: An optical disk comprises a substrate, and a recording layer which is formed on the substrate and on which information is recorded at specific pitches in the form of pit trains, wherein the information is reproduced by projecting a light beam via an object lens, and when the wavelength of the light beam is .lambda..mu.m and the numerical aperture of the object lens is NA, the track pitch is set in the range of (0.72 to 0.8).times..lambda./NA/1.14 .mu.m, and each of the pits has a trapezoid cross section whose upper width is in the range of (0.3 to 0.5).times./NA/1.14 .mu.m and whose lower width is in the range of (0.2 to 0.32).times..lambda./NA/1.14 .mu.m or whose inner wall has an angle of 30.degree. to 70.degree..

Abstract: An optical recording medium comprises a transparent substrate, an inner protection layer, a recording material layer, an outer protection layer, and a reflection layer, which are laminated in this order. In an in-groove recording mode, the ratio of the thickness of the recording material layer to the thickness of the outer protection layer is in a range between 0.52 and 0.95. In an on-land recording mode, the ratio of the thickness of the recording material layer to the thickness of the outer protection layer is in a range between 0.32 and 0.6.

Abstract: An optical disk comprises a substrate, and a recording layer which is formed on the substrate and on which information is recorded at specific pitches in the form of pit trains, wherein the information is reproduced by projecting a light beam via an object lens, and when the wavelength of the light beam is .lambda..mu.m and the numerical aperture of the object lens is NA, the track pitch is set in the range of (0.72 to 0.8).times..lambda./NA/1.14 .mu.m, and each of the pits has a trapezoid cross section whose upper width is in the range of (0.3 to 0.5).times..lambda./NA/1.14 .mu.m and whose lower width is in the range of (0.2 to 0.32).times..lambda./NA/1.14 .mu.m or whose inner wall has an angle of 30.degree. to 70.degree..

Abstract: An optical recording medium comprises a transparent substrate, an inner protection layer, a recording material layer, an outer protection layer, and a reflection layer, which are laminated in this order. In an in-groove recording mode, the ratio of the thickness of the recording material layer to the thickness of the outer protection layer is in a range between 0.52 and 0.95. In an on-land recording mode, the ratio of the thickness of the recording material layer to the thickness of the outer protection layer is in a range between 0.32 and 0.6.

Abstract: A optical recording medium having guide grooves which are parallel or substantially parallel, tracks formed among the guide grooves, offset-compensating areas spaced apart in lengthwise direction of the guide grooves and separating each of the tracks into portions, first pits formed in each portion of each of the tracks and arranged in a center line of the track, and second pits formed in the offset-compensating areas and extending in the center line of the tracks. Also disclosed herein is an optical recording apparatus for applying a light beam to the optical recording medium as defined above, thereby to record data on the medium and reproduce data there from. In the apparatus, two tracking error signals, which represent the distance between the center of a light spot formed on the medium and the center line of a target track, are generated from diffracted light beams from any one of the guide grooves and the offset-compensating area adjacent to the guide groove.

Abstract: In an optical head, a converging lens and a holographic optical element are arranged in the optical path of light reflected by the recording surface of an optical memory recording medium and passing through an objective lens. The holographic optical element has a hologram formed in at least one of two regions split by a region splitting line crossing the optical axis of the converging lens. A photodetector is arranged on the extension line of the optical axis. The photodetector has a plurality of detection surfaces which are respectively split along the region partition line of the holographic optical element to detect light beams diffracted by the hologram. The optical head also includes a detecting system for detecting a focusing error of the objective lens of the optical head by performing predetermined arithmetic operations using an incorporated processing circuit on the basis of output signals obtained by the plurality of detection surfaces of the photodetector.