# US 5,349,481 A · Apparatus and method for distorted track data recovery by rewinding and re-reading the tape at a slower than nominal speed > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,349,481 A - Document ID: US5349481A - Status: Granted - Kind: A - Application number: 08/074,671 - Filed: 1993-06-10 - Granted: 1994-09-20 - Earliest claimed: 1993-06-10 - Assignees: Exabyte Corporation - Inventors: Gerald C. Kauffman; Timothy C. Hughes; Don Heins; Patricia Slovacek; Fadi Abou-Jaoude - Web page: https://patentgrep.com/patent/US5349481A ## CPC - G11B 27/3027: {used signal is digitally coded} - G11B 15/026: {by using processor, e.g. microcomputer} - G11B 15/087: by sensing recorded signals - G11B 15/1875: {adaptations for special effects or editing (signal processing or indexing therefor G11B27/00)} - G11B 15/4673: {by controlling the speed of the tape while the head is rotating} - G11B 20/10: Digital recording or reproducing - G11B 20/12: Formatting, e.g. arrangement of data block or words on the record carriers {(within interface between computers and data recorders G06F3/06)} - G11B 20/18: Error detection or correction; Testing {, e.g. of drop-outs} - G11B 27/005: {Reproducing at a different information rate from the information rate of recording (for television signals H04N5/783)} - G11B 27/107: {of operating tapes} - G11B 2020/183: {wherein at least one additional attempt is made to read or write the data when a first attempt is unsuccessful} - G11B 2220/90: Tape-like record carriers - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) ## Abstract A helical drive system (10) reads tracks (18) on a storage medium (12), including tracks which appear as distorted tracks. Each track (18) comprises a plurality of blocks of data, with each block having unique block-identifying information. A read head (16C) traverses predetermined original azimuthal paths (P0) across the storage medium (12) for reading the blocks recorded along each of the original azimuthal paths (P0). A controller (50) uses the block-identifying information to determine whether any blocks expected to be read during the traversal of the original azimuthal paths (P0) were not read. If expected blocks were not read, the controller (50) rewinds or otherwise reverses the direction of travel of the storage medium (12); sends a signal to a tape transport drive (81) to slow the speed of the medium (12); and, directs that the medium (12) be re-read at a slower tape reread speed. During the slow re-read attempt, the read head (16C) traverses modified azimuthal paths (P1, P2, P3 , . . . P10) which are separated from one another by a distance less than the track pitch, thereby providing opportunities to read blocks which would not otherwise be read due to distortion of the tracks (18). ## Claims ### Claim 1 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 read errors occurred during the traversal of the original azimuthal paths, and which requires 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. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the re-read occurs as the medium travels in the reverse direction. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the controller requires rewinding of the medium and re-reading of the medium as the medium travels in the forward direction. ### Claim 4 (depends on 1) The apparatus of claim 1, wherein the original azimuthal paths and the modified azimuthal paths are essentially linear, with the modified azimuthal paths being essentially parallel to the original azimuthal paths. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the re-read speed is in a ratio in a range of 1:3 to 1:10 the nominal reading speed. ### Claim 6 (depends on 1) The apparatus of claim 1, further comprising memory means wherein the block-identifying information is stored, and wherein the control means examines the memory means to determine whether any blocks expected to be read during the traversal of the original azimuthal paths were not read. ### Claim 7 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. ### Claim 8 (depends on 7) The apparatus of claim 7, wherein the re-read occurs as the medium travels in the reverse direction. ### Claim 9 (depends on 7) The apparatus of claim 7, wherein the controller requires rewinding of the medium and re-reading of the medium as the medium travels in the forward direction. ### Claim 10 (depends on 7) The apparatus of claim 7, wherein the original azimuthal paths and the modified azimuthal paths are essentially linear, with the modified azimuthal paths being essentially parallel to the original azimuthal paths. ### Claim 11 (depends on 7) The apparatus of claim 7, wherein the re-read speed is in a ratio in a range of 1:3 to 1:10 the nominal reading speed. ### Claim 12 (depends on 7) The apparatus of claim 7, further comprising memory means wherein the block-identifying information is stored, and wherein the control means examines the memory means to determine whether any blocks expected to be read during the traversal of the original azimuthal paths were not read. ### Claim 13 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. ### Claim 14 (depends on 13) The method of claim 13, wherein the re-read occurs as the medium travels in the reverse direction. ### Claim 15 (depends on 13) The method of claim 13, wherein the medium is rewound and the medium subsequently travels in the forward direction during the re-read. ### Claim 16 (depends on 13) The method of claim 13, wherein the original azimuthal paths and the modified azimuthal paths are essentially linear, with the modified azimuthal paths being essentially parallel to the original azimuthal paths. ### Claim 17 (depends on 13) The method of claim 13, wherein the re-read speed is in a ratio in a range of 1:3 to 1:10 the nominal reading speed. ### Claim 18 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. ### Claim 19 (depends on 18) The method of claim 18, wherein the original azimuthal paths and the modified azimuthal paths are essentially linear, with the modified azimuthal paths being essentially parallel to the original azimuthal paths. ### Claim 20 (depends on 18) The method of claim 18, wherein the re-read speed is in a ratio in a range of 1:3 to 1:10 the nominal reading speed.