Abstract: In a shift correction decoder which processes d,k-constrained RLL data that is encoded in accordance with a shift correction code whose symbols in GF(p) comprise modulo p reductions of cumulative sums of successive run symbols of the RLL data (where p is an odd prime), additive errors (i.e., drop-out and drop-in errors) in the received RLL data are corrected by relying in part on information pertaining to the sequence of the polarities of successive 1-bits in the received RLL data. The polarity information is used to either insert missing 1-bits (due to drop-outs) or delete spurious 1-bits (due to drop-ins) and specify to the shift correction decoder the location of an additive error as an erasure. Synchronization slips are corrected by pre-multiplying the received codeword polynomial by a factor which reduces to two the number of errors created by a single synchronization slip. GF(p) is selected such that p.ltoreq.

Abstract: In a shift-correcting code which represents (d,k)-constrained run-length-limited (RLL) channel data as symbols drawn from GF(p.sup.m), the encoding process produces a set of redundant parity ternary GF(p.sup.m) symbols representing three shift error conditions: forward shift, backward shift and no shift, for p=3 and m=1 for example. The encoder of the invention transforms the parity symbols into (d,k)-constrained RLL channel bits to produce a binary data sequence that can be inserted in the RLL channel data stream without a large number of linking bits to maintain compliance with the (d,k) RLL constraints. A shift error in the RLL channel data representing parity symbols affects no more than one decoded parity symbol.

Abstract: A method for coding/decoding ternary symbols to d,k-constrained binary runs in a way that (i) associates (codes) a number of ternary symbols with a lesser number of d,k-constrained binary runs and (ii) provides that an individual single-shift error in any of the received binary runs that constitute a binary data codeword will cause at most one ternary symbol to be in error in the associated (decoded) ternary symbol codeword. This method allows shift-correction codeword parity checks to be transmitted (i.e., transformed to a d,k-constrained channel data sequence) with increased efficiency, so that the required number of channel bits needed to represent the parity checks is decreased.

Abstract: Channel encoded data (for example run length limited encoded data) is further encoded in accordance with a shift correction code prior to transmission. Upon reception, forward and backward shift errors present in the received channel encoded data are corrected by a shift correction decoder. The shift error correction is accomplished using a code, such as (for example) a BCH code over GF(p) or a negacyclic code, which treats each received symbol as a vector having p states. For a single shift error correction, p=3 and there are three states (forward shift, backward shift, no shift). In one embodiment, conventional error correction codewords which encode the user data may be interleaved within successive shift correction codewords prior to channel encoding, thereby enabling the error correction system to easily handle a high rate of randomly distributed shift errors (which otherwise would result in a high rate of short error bursts that exceed the capacity of the block error correction code).

Abstract: A photorefractive system is disclosed containing interposed between electrodes an electrophotographic photoreceptor layer unit and a layer having a second order polarization susceptibility of greater than 10.sup.-9 electrostatic units comprised of organic polar aligned noncentrosymmetric molecular dipoles having an electron donor moiety linked through a conjugated .pi. bonding system to an electron acceptor moiety. The device can be employed to transfer information from one source of electromagnetic radiation to another.

Abstract: A photographic contact printing process is disclosed having application in the mass production of replicate video discs from a master disc, and other applications wherein it is desired to replicate micro-detail over a relatively large area. A problem with conventional contact printing from a mask to a photographic medium is one of maintaining intimate contact over a relatively large area since dust, dirt, etc., are almost impossible to completely eliminate in any practical manner. In accordance with the present invention, a contact printing process is provided wherein intimate contact is not necessary for making high quality contact prints. The present invention recognizes that in contact printing information from a master disc to a replicate disc, the contact printing process is significantly less sensitive to imperfect contact between the master disc and the replicate disc if one employs a replicate disc comprising a photosensitive material having a certain optical properties.

Abstract: An improved method of optically writing and/or reading high density information involves: (1) predeterminedly positioning a flat, uniformly thick, flexible, optical disc with respect to an axis of rotation; (2) rotating the disc on such axis at a high speed and in a predeterminedly spaced relation to a predeterminedly shaped, smooth, featureless reference surface and (3) coupling a central region between the disc and reference surface to an ambient gas source. Related apparatus and disc configurations, including embodiments having flexible disc covers, also are disclosed.

Abstract: A method for writing and/or reading information on an optical recording element, such as an optical disk, utilizes a recording element comprising a recording layer having physical and optical properties which are optimized for phase-shift read-out. The optical properties of the recording layer give rise to a non-linear relative phase shift/layer thickness curve which, in combination with a predetermined nominal thickness of the recording layer, enhances the signal-to-noise ratio of the read-out signal.

Abstract: An optical disk unit, of the kind having a record element and a flexible cover sheet that are attached around an outer periphery in a manner providing an outer spacing and a generally enclosed inter-space therebetween, has an improved construction which significantly reduces the likelihood of contact between the record element and cover sheet. Central spacing means provide a central sheet-to-element spacing that is significantly larger than said outer spacing and vent means, into and out of the inter-space cause a reduction in the spacing between the record portion of the element and the cover sheet during write/read operation. The air flow through the vent means also reduces the formation of visible debris in the enclosed record element/cover sheet inter-space.

Abstract: A recording element comprising a support having thereon a heat-deformable optical recording layer having a transparent ceramic overcoat characterized in that the overcoat has a thickness up to about 0.05 .mu.m is disclosed.

Abstract: The quality of spot-focus of optical writing and reading light upon the information surface of a flexible optical disc is passively enhanced by (1) rotating the disc with its neutral plane stabilized in space and (2) directing such light through the optical disc support into precise spot-focus on the information surface. With this technique spherical aberration induced by the disc support compensates for thickness variation of the support. Various structural embodiments are disclosed.

Abstract: High information density retrieval method and system which employ the scanning of an optical disk, having a thermally-deformable record layer overlying a reflective support, with a read light beam. The optical disk tracks contain information in the form of variable-width, approximately 0.5.pi. phase-depth, pit regions interleaved between nominal thickness land regions. The pits have varying track lengths within a pit-length range constituting a disk fractional band-width of greater than 4.0 and read light reflected from the tracks is split-detected. The split-detected, electrical analog signal is peak-detected to reconstruct recorded digital data on the disk.

Abstract: An improved method of optically writing and/or reading high density involves: (1) predeterminedly positioning a flat, uniformly thick, flexible, optical disc with respect to an axis of rotation; (2) rotating the disc on such axis at a high speed and in a predeterminedly spaced relation to a predeterminedly shaped, smooth, featureless reference surface and (3) coupling a central region between the disc and reference surface to an ambient gas source. Related apparatus and disc configurations, including embodiments having flexible disc covers, also are disclosed.

Abstract: In accordance with the present invention, methods and apparatus are provided for making optical disk recordings having marks in radial format, representing information signals, of total fractional bandwidths greater than about 3 wherein information is recorded along constant width tracks irrespective of the radial position of recording. Specifically, constant track width recording is achieved by controlling the various recording parameters (recording spot size, tangential velocity of the optical disk, and the modulation of the recording spot) such that the optical disk receives approximately the same maximum energy density during recording of all information marks.

Abstract: Optical disc structure physically optimized for real-time recording and playback of high-density information and methods and apparatus pertaining to such disc structure. One disclosed disc embodiment is designed for heat-deformation recording and reflective read-out and, in regard to the chosen reading wave-length, is optimized in recording stratum thickness and optical constants for high sensitivity writing and high contrast, phase interference reading. Another disclosed disc embodiment is further optimized in thickness and optical constants with respect to a chosen writing wavelength to further enhance writing sensitivity and reduce requisite writing power.

Abstract: An optical disc of the type having a thermally deformable recording layer overlying a reflectively surfaced support features a crenelated disc support surface having grooves of predetermined depth and interleaved lands arranged in a spiral or concentric pattern. The recording layer's outer surface is nominally planar so that the differences in thickness between "over-land" and "over-groove" portions thereof impart high phase-shift contrast to light of a given read wavelength.

Abstract: Apparatus and method for reading optical discs containing information in the form of tracks of high-spacial-frequency, phase-modulating marks (e.g., depressions or pits) includes means for directing the zero and one first diffraction order of read light returned from the scanned track into superimposed relation on a photodetector and means for predeterminedly masking a portion of the zero diffraction order light so that its magnitude is more equal to that of the first diffraction order light.

Abstract: A recording element adapted for real-time writing and reading with light of a single given wave-length utilizes a recording stratum, including a heat-deformable dye-binder layer, overlying a reflective support and is characterized by the dye-binder layer having optical constants such that its reflectance versus thickness variation curve has a first reflectance minimum having a high depth of modulation and the recording stratum having a nominal thickness sufficiently greater than the thickness corresponding to the first reflectance minimum to effect reflection of a significant portion of light of such given wavelength.

Abstract: In accordance with the present invention, the optical characteristics of a thermal deformation record device are so altered that the device can be read back using the same beam as was used for recording. Moreover, the read beam can be used for playback at an arbitrarily high power level to enhance the signal-to-noise ratio of the recovered signal and yet not damage the deformation recording.

Abstract: A frame-rate converting film scanner suitable for use with a solid-state line sensing array for producing a television signal from motion picture film is disclosed. The scanner is capable of projecting film at continuously moving projection rates that are not necessarily submultiples of the standard television field rate. The scanner includes a rotating multifacet mirror such as a reflecting polygon that sweeps a succession of images of the moving film past the line scanner at a rate sufficient to cause the line scanner to scan one full frame in the time required for generating a standard television field. Each successive image deflected by the polygon is displaced from the preceding image by one film frame height, whereby, the transition from one image to the next, as the successive images sweep across the line scanner, proceeds from a location in one frame to a corresponding location in an adjacent frame.