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.

Abstract: In a method of manufacturing a diffraction grating, the grating-bearing surface of a master grating is coated with a release agent, and a rigid substrate has a layer of ultravoilet sensitive liquid resin applied thereto before bringing the master grating and the substrate together to trap a film of the liquid resin therebetween, whereafter the liquid resin is cured by exposure to ultraviolet light through the master grating and the master grating and resin-profiled substrate are separated prior to completion of the diffraction grating by deposition of a thin metal film on the resin-profiled surface of the substrate.

Abstract: Apparatus for measuring displacement comprises a member, such as a reading head, which carries a stepped index diffraction grating (14) and is movable with respect to a reflective scale grating (16). The head also carries a source (10) and lens for directing light on to the index grating and then on to the scale grating for reflection to the index grating, with the resultant Moire bands detected by a photodetector (18) on the reading head. In order to determine the phase separation or offset, and to avoid high sensitivity thereof to the spacing between the gratings, the index grating (14) has a square-stepped profile resulting in graded, increasing thickness. Alternatively, a conventional index grating may be employed in conjunction with a stepped profile optical element interposed between the two gratings.

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 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 camera zoom lens system comprising; means for generating and storing a first information signal representing a predetermined position of the first movable lens group, means for generating a second information signal whose value determines a relationship between the respective positions of said first and second movable lens groups, first computing means for deriving from the stored first information signal a third signal representing the position to which the second movable lens group must move so that both lens groups produce an in-focus image of the object at infinity, second computing means responsive to the first and second information signals for generating a correction signal which when combined with the third signal produces an output signal representing the position to which the second movable lens group must move so that both lens groups will produce an in-focus image of an object at a specified distance, third computing means responsive to the correction signal and the third signal for generating a

Abstract: An apparatus for recording information in the form of a two dimensional array of miniature images on a recording material such as electrophotographic, photographic or photochromic material. Means are included for forming those images (by such of the processes of sensitizing, charging, exposing, developing or fixing as are appropriate to the particular material used) from originals or copies of legible size. A facility is provided to form one or more miniature images occupying only part of a storage member on one occasion, and to record a further such image or images on later occasions. Guide means and propulsion means in two dimensions are included for adjusting the relative positions of the storage member and the image forming or image viewing device so that any image space may be presented to the image forming device and any image may be presented to an image viewing device.

Abstract: A thermoplastics data storage member carries information which can be imaged using non-coherent light and, in addition to and distinct from that information, control data which defines a two-coordinate system for the member which controls random access to the information. A reading apparatus comprises a non-laser optical system for imaging selected areas of the information and a servo-system, including a microprocessor and transducers for reading the control data, for positioning a reading head of the optical system in desired locations relative to the storage member. The invention affords cheap optical data bases readable by apparatus not requiring a laser optical system.