Apparatus and method for distorted track data recovery by rewinding and re-reading the tape at a slower than nominal speed

Apparatus for reading information recorded on a storage medium in helical tracks, with each track comprising a plurality of blocks of data with each block having unique block-identifying information, said apparatus comprising:

• a transport for selectively transporting the storage medium in forward and reverse directions of medium travel;
• a rotatable drum having a portion of a peripheral surface thereof contiguous with the storage medium as the storage medium is transported therepast by the transport;
• a reading head mounted on the drum for traversing original azimuthal paths across the storage medium and for reading blocks including the block-identifying information recorded along at least a portion of each of the original azimuthal paths;
• a controller which uses the block-identifying information to determine whether any blocks expected to be read during the traversal of the original azimuthal paths were not read, and which generates a plurality of control signals in accordance with the determination for application to the transport, a first of the control signals causing the transport to transport the storage medium in the reverse direction of medium travel, a second of the control signals causing the transport to transport the storage medium at a re-read speed which is slower than a nominal reading speed, whereby, as the storage medium is transported at the re-read speed, the read head traverses modified azimuthal paths in an attempt to read a block which should have been previously read but was not previously read, the modified azimuthal paths being closer together in the direction of medium travel than the original azimuthal paths.

A method for reading information recorded on a storage medium in helical tracks, with each track comprising a plurality of blocks of data with each block having unique block-identifying information, the method comprising:

• transporting the storage medium in a forward direction of medium travel at a nominal reading speed past a rotatable drum, the rotatable drum having a portion of a peripheral surface thereof contiguous with the storage medium as the storage medium is transported therepast;
• rotating the rotatable drum whereby reading means mounted on the drum traverses original azimuthal paths across the storage medium;
• reading blocks including the block-identifying information recorded along at least a portion of each of the original azimuthal paths;
• using the block-identifying information to determine whether any read errors occurred during the traversal of the original azimuthal paths;
• and,
• requiring, in response to the determination, that the read head re-read portions of the storage medium where the error occurred by traversing modified azimuthal paths, the modified azimuthal paths being separated from one another by a distance less than the track pitch.

A method for reading information recorded on a storage medium in helical tracks, with each track comprising a plurality of blocks of data with each block having unique block-identifying information, the method comprising:

• transporting the storage medium in a forward direction of medium travel at a nominal reading speed past a rotatable drum, the rotatable drum having a portion of a peripheral surface thereof contiguous with the storage medium as the storage medium is transported therepast;
• rotating the rotatable drum whereby reading means mounted on the drum traverses original azimuthal paths across the storage medium;
• reading blocks including the block-identifying information recorded along at least a portion of each of the original azimuthal paths;
• using the block-identifying information to determine whether any blocks expected to be read during the traversal of the original azimuthal paths were not read;
• transporting the storage medium in a reverse direction of medium travel in response to the determination;
• then,
• transporting the storage medium in the forward direction at a re-read speed which is slower than the nominal reading speed, whereby, as the storage medium is transported at the re-read speed, the read head traverses modified azimuthal paths in an attempt to read a block which should have been previously read but was not previously read, the modified azimuthal paths being closer together in the direction of medium travel than the original azimuthal paths.