Abstract: A method and apparatus for improving optical disk recording performance is disclosed, which comprises reading data from an optical disk while writing data to the disk in order to verify the data, to control the power of the recording laser and to prevent overwriting of the disk.

Abstract: A method of reducing the surface noise of optical disk products of the type having a surface relief pattern is disclosed. In one embodiment, an adherent layer is applied to the substrate of the disk before it is coated with the recording material layer. In another embodiment, a polymeric replica produced from a master disk is treated by spin coating or dipping in a weak solvent which serves to smooth out microscopic roughness thereby removing surface irregularities. In a third embodiment, a metal coated replica is subjected to an electropolishing operation which again serves to remove a small amount of metal material, preferentially from "high spots".

Abstract: A data storage medium is provided which is suitable for production or replication by moulding, casting, embossing or a similar process against a tool. The data storage medium comprises an optically sensitive layer at or adjacent to one surface of the medium, said one surface of the medium comprising a plurality of topographical features or structures disposed in a regularly repeating pattern, said pattern being free from undercutting so that the medium can be produced and/or replicated by molding, casting, embossing or similar process against a tool. The optically sensitive layer is preferably overcoated with a thin film of a metallic material which conforms to the topography of said surface.

Abstract: A pre-formatted optical data storage member is described in which format zones are generated by the provision in the surface of the optical medium of a "moth-eye" structure, i.e. regular surface pattern in the form of an arrangement of grooves or protuberances. The pitch and depth of the pattern is such that when irradiated with illumination of predetermined optical characteristics, the format zones display a reflectivity substantially lower than that of the remainder of the optical storage member. Methods of producing optical data storage members with such pre-formatting are also described.

Abstract: A process for producing an optical recording medium, comprising heat-treating an optical recording medium formed of a thin metal film on the minutely roughened surface of a plastic substrate, the medium being capable of strongly absorbing laser light of a specific wavelength region thereby being able to be written upon.

Abstract: An optical recording medium which is made up of a plastic substrate having a surface of minute roughened structure and a metal thin film formed on the substrate and is capable of strongly absorbing laser light of a specific wavelength region, thereby writing data on the medium. The optical recording medium is characterized by an intermediate layer interposed between the plastic substrate and the metal thin film, the intermediate layer having a higher melting point or lower thermal conductivity than the metal thin film and having a thinner average thickness than the metal thin film. The optical recording medium has a definite recording threshold value and permits stable recording with a high CNR by using a broadly ranged recording power.

Abstract: An interferometer which comprises: (1) a single, coherent light source; (2) a first converging lens positioned on the optical axis of said coherent light source; (3) a beam-splitting arrangement positioned on said optical axis and spaced from said first converging lens by a distance greater than the focal length of said lens; (4) a second converging lens positioned on said lens; (4) a second converging lens positioned on said optical axis to receive and to focus the two beams emanating in use from the beam-splitting arrangement; and (5) a mirror arrangement positioned so that the beams focussed by said second converging lens impinge on the mirror system and so that the reflected beams are brought to intersect at a focal point and with a large angle between the principal rays of the two beams.

Abstract: A method of forming an image and a radiation-sensitive medium suitable for carrying an image is disclosed. The medium comprises a substrate having a surface structure comprising grooves with a depth of 20 to 100 nanometers. At or close to the surface structure there is a layer of radiation-responsive material which is such that irradiation of selected parts of the structure with radiation of a predetermined polarization causes radiation to be absorbed at the irradiated parts of the surface so that corresponding areas of the radiation-responsive layer are affected in a way which makes such areas distinguishable from the remaining, non-irradiated areas of the radiation-responsive layer. An image and/or data may be stored in such a medium in analogue, digital or pictorial form, or in a combination of any two or all three of these forms. The invention also provides primary and secondary pre-formed data carrying media, the secondary media being replicated from the primary media.

Abstract: A data storage medium is provided which is suitable for production or replication by moulding, casting, embossing or a similar process against a tool. The method for manufacturing a data storage medium has a surface or a surface region which is strongly absorbent of at least a predetermined band of wavelengths of electromagnetic radiation. The surface or surface region includes a layer of a heat sensitive material which has a textured surface pattern the pitch of which is smaller than the shortest wavelength of the predetermined band of wavelengths, and the depth (peak-to-trough) of which is at least 100 nm. The surface pattern is free from undercutting, and can comprise an array of protuberances or one or more sets of grooves (which may be intersecting). The textured surface pattern is further coated with a thin film of a high-opacity material, e.g. gold, the thickness of the overcoating preferably being such as to give no more than 10% transmission of incident radiation.

Abstract: A data storage medium is provided which is suitable for production or replication by moulding, casting, embossing or a similar process against a tool. The data storage medium has a surface or a surface region which is strongly absorbent of at least a predetermined band of wavelengths of electromagnetic radiation. The surface or surface region includes a layer of a material which undergoes a large volume change or degradation and has a regular, sinuous textured surface pattern which is free from undercutting. The textured surface pattern is coated with a thin film of platinum or a platinum alloy, the thickness of the overcoating preferably being such as to give no more than 10% transmission of incident radiation.A method of storing information on such a data storage medium is also disclosed. The data storage medium may be prepared in blank form for use as the consumer desires, or it may be pre-recorded in part or in entirety.

Abstract: Optical data storage members in which the guard bands present between data-carrying tracks of conventional data storage members are used to carry information recorded in a manner which avoids the danger of cross-talk between adjacent tracks. One preferred arrangement consists of an optical data storage member comprising an optically recordable surface having a plurality of tracks in which information may be recorded in analogue or digital form, the tracks being of a first type in which the material constituting the track is sensitive to radiation of a first predetermined characteristic and a second type in which the material thereof is sensitive to radiation of a second predetermined characteristic, wherein tracks of the first type alternate across the surface of the second type. The tracks may be constituted by a surface region (1,2,3,4,5) carrying a plurality of closely spaced grooves (11,12,13,14,15), the grooves of one track being orthogonally directed with respect to those of its adjacent tracks.