Abstract:
A laser data recording system for storing digital information in the form of digital bits ablated from an energy-absorbing storage medium by an intensity modulated laser beam. The system provides instantaneous reflective readout of the local surface state of the storage medium as the ablative recording process is initiated at selected locations along a scan line, in response to the intensity of the modulated laser beam. This reflective readout simultaneously provides a recording surface continuity verification signal which is monitored to insure that the storage medium surface is free from defects at the point of recording. The proper sequence of levels of this instantaneous reflective signal verifies that the portions of the data record which are to be ablated are actually generated, and that the regions which are not to be ablated are void-free, thus insuring a completely correct recording. The laser beam is scanned in parallel scan lines across the storage surface and during read-out of stored information the intensity of the laser beam is set at a fixed level sufficiently low that ablation cannot occur. Signals are also provided for automatically centering the laser beam on selected scan line and for servo control of laser intensity. In one embodiment removable and replaceable recording strips are mounted around the surface of the drum. A rectangular crosssection is optically imparted to the laser beam.
Abstract:
A digital data processing system for transferring digital data from a data channel of the central processor of a computing system or from a temporary storage medium to a high-density laser data recording medium and for nondestructively reproducing the data stored in the high-density medium in a form suitable for transfer to a computer data channel or temporary storage for subsequent use. Input data is transferred into a buffer and control subsystem. This subsystem generates synchronous clock signals and data verification signals which are interleaved with the input data and the composite signal thus produced is recorded on the high-density storage medium. Each recorded bit is checked to insure accuracy of recording at the instant of recording that bit, and remedial action is automatically initiated in the event of error. This remedial action consists of recording a completely unambiguous error indication signal, and re-recording the affected data in such a manner that the final record provides sufficient information to permit correction of all recording errors. During readout the retrieved data is transferred from the high-density storage medium into the buffer and control subsystem for verification of the data. If the data is correct, the synchronous clock and data verification signals are stripped from the output data, the data is reorganized into its original format, and transferred to a computer data channel or other storage medium for subsequent use. If during readout an error is detected, remedial action is automatically initiated before the data is transferred. The buffer and control subsystem includes self-checking diagnostic circuits for detecting and localizing malfunctions in all portions of the high-density data storage and data conversion system.
Abstract:
A laser recording system for scanning a modulated laser beam in spaced parallel lines across a flat elongated strip of energy absorbing material and for ablating minute regions from the material in a linear pattern representing digital bits according to the intensity of the modulating signal. The flat elongated record strip is wound around the surface of a drum during the recording and reproducing operations and the drum is rotated with respect to the laser beam. By means of a servo-controlled linear positioning mechanism, the laser beam is moved transversely to the direction of drum rotation in a manner which will permit selection of any one of a large number of spaced parallel scan lines on the record strip. The final positioning of the laser beam to the selected scan line is performed by a servo-controlled mirror galvanometer mounted on the linear positioning mechanism carriage.