Abstract: An acquiring unit acquires, from a storage device capable of storing a file by dividing the file into a plurality of blocks, managing information indicating an address of each block configuring the file. A creating unit creates a table indicating a start address and a size of each continuous region by extracting the address of each block from the acquired managing information, and aggregating blocks having continuous addresses as a continuous region. A reading unit reads a file stored in a non-volatile memory. A dividing unit divides the read file into a plurality of blocks. A writing unit writes the divided file to the storage device in units of the continuous region, which is from the start address over the size, based on the table, so as to maintain the addresses indicated in the managing information.

Abstract: An XY array of sync bits and information bits is recorded in a recording medium through the use of holography. The sync bits are in parallel Y-direction-extending groups having an X-direction minimum inversion interval of 2 or more. The information bits are placed between the parallel Y-direction-extending groups of the sync bits. One of the parallel Y-direction-extending groups of the sync bits and ones of the information bits neighboring said one of the parallel Y-direction-extending groups of the sync bits are scanned to reproduce a Y-direction sync bit sequence and at least one Y-direction information bit sequence. The reproduced Y-direction sync bit sequence is re-sampled through the use of a digital phase locked loop to obtain corrected Y-direction sync bit frequency and phase. The Y-direction information bit sequence is re-sampled in response to the corrected Y-direction sync bit frequency and phase. The Y direction is vertical, horizontal, or halfway therebetween.

Abstract: An information signal is read from a recording medium to generate a reproduced signal. A sync detector detects a sync signal in the reproduced signal on a pattern search basis during operation in a direct mode. The sync detector sets a detection window and detects a sync signal in the reproduced signal in the detection window during operation in an inertia mode. A special pattern signal in the reproduced signal is detected and counted to generate a count result. The count result is reset in response to detection of a first special signal in the reproduced signal. A detection flag is generated in cases where a second special signal in the reproduced signal is detected when the count result denotes a last sector in a block of the reproduced signal. The sync detector changes its operation from the inertia mode to the direct mode when the detection flag is generated.

Abstract: An optical disk unit capable of correcting a spherical aberration without using special patterns is provided. Also provided is an aberration correcting method used for such an optical disk unit. An objective lens 7 is moved along an optical axis by a predetermined distance from an in-focus position in a first direction, and then, is moved by the predetermined distance from the in-focus position in a second direction that is opposite to the first direction. In each of the objective lens moved states, a random signal having a plurality of amplitudes and periods is reproduced from an optional area of an information recording layer 12 of an optical disk 11.

Abstract: A first run length encoder implements run length modulation of a first information signal to generate a second information signal of a run-length-limited code while subjecting the second information signal to DSV control and adding a sync signal to the second information signal to get a third information signal. A converter changes the third information signal into an NRZI signal including information code words. A parity generator produces original parity signals in response to the information code words in the NRZI signal, and combines the information code words and the original parity signals to form a first parity-added signal. A second run length encoder implements run length modulation of only the original parity signals in the first parity-added signal to convert the first parity-added signal into a second parity-added signal while subjecting the second parity-added signal to DSV control. The second parity-added signal is recorded on a recording medium.

Abstract: A signal of a run-length-limited code is read out from a recording medium. The read-out signal is converted into a reproduced digital signal. A decoder subjects the reproduced digital signal to first decoding different from run length decoding to get a first decoded signal. Information bit streams are generated from the first decoded signal. The information bit streams are different in timing by 1-bit-correpsonding intervals. Run length decoders subject the information bit streams to run length decoding to get run-length-decoded bit streams respectively. Each of the run-length-decoded bit streams undergoes one of error correction and error detection. A decision is made as to which of the run-length-decoded bit streams is the smallest in error number on the basis of results of the one of error correction and error detection. The run-length-decoded bit stream being the smallest in error number is selected and outputted as a likeliest information bit stream.

Abstract: In a PLL circuit, a phase error of a reproduced signal is extracted in either a way based on a zero-cross timing or a way based on a self-running timing. A decision is made as to whether the reproduced signal is in a continuous-wave interval where an inversion period of the reproduced signal remains constant or in a random-wave interval where the inversion period of the reproduced signal varies at random. When the reproduced signal is in a continuous-wave interval, a phase error is extracted on the self-running-timing basis. When the reproduced signal is in a random-wave interval, a phase error is extracted on the zero-cross-timing basis. A continuous-wave interval may be replaced by a specified-pattern repetition interval where the inversion period of the reproduced signal changes in accordance with a repetition of a specified pattern.

Abstract: A transversal filter subjects a reproduced signal to partial-response waveform equalization responsive to tap coefficients to generate an equalization-resultant signal. There is generated 0-point information representing whether or not the reproduced signal corresponds to a zero-cross point. A temporary decision device calculates a temporary decision value of the equalization-resultant signal on the basis of a PR mode signal, an RLL mode signal, at least four successive samples of the 0-point information, and at least four successive samples of the equalization-resultant signal. Calculation is made as to a difference between the temporary decision value of the equalization-resultant signal and an actual value thereof. An error signal is generated in response to the calculated difference. The tap coefficients of the transversal filter are controlled in response to the generated error signal. The partial-response waveform equalization is PR(a, b, b, b, a).

Abstract: An XY array of sync bits and information bits is recorded in a recording medium through the use of holography. The sync bits are in parallel Y-direction-extending groups having an X-direction minimum inversion interval of 2 or more. The information bits are placed between the parallel Y-direction-extending groups of the sync bits. One of the parallel Y-direction-extending groups of the sync bits and ones of the information bits neighboring said one of the parallel Y-direction-extending groups of the sync bits are scanned to reproduce a Y-direction sync bit sequence and at least one Y-direction information bit sequence. The reproduced Y-direction sync bit sequence is re-sampled through the use of a digital phase locked loop to obtain corrected Y-direction sync bit frequency and phase. The Y-direction information bit sequence is re-sampled in response to the corrected Y-direction sync bit frequency and phase. The Y direction is vertical, horizontal, or halfway therebetween.

Abstract: In a PLL circuit, a phase error of a reproduced signal is extracted in either a way based on a zero-cross timing or a way based on a self-running timing. A decision is made as to whether the reproduced signal is in a continuous-wave interval where an inversion period of the reproduced signal remains constant or in a random-wave interval where the inversion period of the reproduced signal varies at random. When the reproduced signal is in a continuous-wave interval, a phase error is extracted on the self-running-timing basis. When the reproduced signal is in a random-wave interval, a phase error is extracted on the zero-cross-timing basis. A continuous-wave interval may be replaced by a specified-pattern repetition interval where the inversion period of the reproduced signal changes in accordance with a repetition of a specified pattern.

Abstract: In a PLL circuit, a phase error of a reproduced signal is extracted in either a way based on a zero-cross timing or a way based on a self-running timing. A decision is made as to whether the reproduced signal is in a continuous-wave interval where an inversion period of the reproduced signal remains constant or in a random-wave interval where the inversion period of the reproduced signal varies at random. When the reproduced signal is in a continuous-wave interval, a phase error is extracted on the self-running-timing basis. When the reproduced signal is in a random-wave interval, a phase error is extracted on the zero-cross-timing basis. A continuous-wave interval may be replaced by a specified-pattern repetition interval where the inversion period of the reproduced signal changes in accordance with a repetition of a specified pattern.

Abstract: An information signal is read from a recording medium to generate a reproduced signal. A sync detector detects a sync signal in the reproduced signal on a pattern search basis during operation in a direct mode. The sync detector sets a detection window and detects a sync signal in the reproduced signal in the detection window during operation in an inertia mode. A special pattern signal in the reproduced signal is detected and counted to generate a count result. The count result is reset in response to detection of a first special signal in the reproduced signal. A detection flag is generated in cases where a second special signal in the reproduced signal is detected when the count result denotes a last sector in a block of the reproduced signal. The sync detector changes its operation from the inertia mode to the direct mode when the detection flag is generated.

Abstract: An optical information recording medium (1) is composed of a pit recording area (2), wherein various control information is recorded by a prepit, and a user recording area (3) having a guide groove formed in a groove format, and a phase depth for the prepit and the groove are approximately the same wherein the phase depth is less than or equal to ?/10, wherein ? is a wavelength for reproducing light source. A recording/reproducing apparatus (4) for the optical information recording medium (1) includes decoding means (12) for decoding information by detecting a tangential push-pull reproduced signal from the prepit recording area (2) and detecting an aggregated signal from the user recording area (3).

Abstract: A first run length encoder implements run length modulation of a first information signal to generate a second information signal of a run-length-limited code while subjecting the second information signal to DSV control and adding a sync signal to the second information signal to get a third information signal. A converter changes the third information signal into an NRZI signal including information code words. A parity generator produces original parity signals in response to the information code words in the NRZI signal, and combines the information code words and the original parity signals to form a first parity-added signal. A second run length encoder implements run length modulation of only the original parity signals in the first parity-added signal to convert the first parity-added signal into a second parity-added signal while subjecting the second parity-added signal to DSV control. The second parity-added signal is recorded on a recording medium.

Abstract: An optical disk unit capable of correcting a spherical aberration without using special patterns is provided. Also provided is an aberration correcting method used for such an optical disk unit. An objective lens 7 is moved along an optical axis by a predetermined distance from an in-focus position in a first direction, and then, is moved by the predetermined distance from the in-focus position in a second direction that is opposite to the first direction. In each of the objective lens moved states, a random signal having a plurality of amplitudes and periods is reproduced from an optional area of an information recording layer 12 of an optical disk 11.

Abstract: An information signal is read from a recording medium to generate a reproduced signal. A sync detector detects a sync signal in the reproduced signal on a pattern search basis during operation in a direct mode. The sync detector sets a detection window and detects a sync signal in the reproduced signal in the detection window during operation in an inertia mode. A special pattern signal in the reproduced signal is detected and counted to generate a count result. The count result is reset in response to detection of a first special signal in the reproduced signal. A detection flag is generated in cases where a second special signal in the reproduced signal is detected when the count result denotes a last sector in a block of the reproduced signal. The sync detector changes its operation from the inertia mode to the direct mode when the detection flag is generated.

Abstract: A signal of a run-length-limited code is read out from a recording medium. The read-out signal is converted into a reproduced digital signal. A decoder subjects the reproduced digital signal to first decoding different from run length decoding to get a first decoded signal. Information bit streams are generated from the first decoded signal. The information bit streams are different in timing by 1-bit-correpsonding intervals. Run length decoders subject the information bit streams to run length decoding to get run-length-decoded bit streams respectively. Each of the run-length-decoded bit streams undergoes one of error correction and error detection. A decision is made as to which of the run-length-decoded bit streams is the smallest in error number on the basis of results of the one of error correction and error detection. The run-length-decoded bit stream being the smallest in error number is selected and outputted as a likeliest information bit stream.

Abstract: A transversal filter subjects a reproduced signal to partial-response waveform equalization responsive to tap coefficients to generate an equalization-resultant signal. There is generated 0-point information representing whether or not the reproduced signal corresponds to a zero-cross point. A temporary decision device calculates a temporary decision value of the equalization-resultant signal on the basis of a PR mode signal, an RLL mode signal, at least four successive samples of the 0-point information, and at least four successive samples of the equalization-resultant signal. Calculation is made as to a difference between the temporary decision value of the equalization-resultant signal and an actual value thereof. An error signal is generated in response to the calculated difference. The tap coefficients of the transversal filter are controlled in response to the generated error signal. The partial-response waveform equalization is PR(a, b, b, b, a).

Abstract: A signal of a run-length-limited code is reproduced from a recording medium. The reproduced signal is sampled to generate a sampling-resultant signal. An odd-sample signal and an even-sample signal are generated in response to the sampling-resultant signal. A first transversal filter subjects the odd-sample signal to first partial-response waveform equalization to generate an equalization-resultant odd-sample signal. The first partial-response waveform equalization depends on first tap coefficients. The first tap coefficients are controlled on a feedback basis to minimize an error of the equalization-resultant odd-sample signal. A second transversal filter subjects the even-sample signal to second partial-response waveform equalization to generate an equalization-resultant even-sample signal. The second partial-response waveform equalization depends on second tap coefficients. The second tap coefficients are controlled on a feedback basis to minimize an error of the equalization-resultant even-sample signal.

Abstract: A binarizing device operates for controlling a slice level relative to a DC level of a reproduced signal in response to a slice level control signal to generate a controlling-resultant slice level, and for comparing the reproduced signal with the controlling-resultant slice level to convert the reproduced signal into a binary signal. A signal generating device operates for generating the slice level control signal in response to the binary signal. An offset detecting device operates for detecting an offset in a modulation-resultant-code pattern in response to the binary signal, and for generating code pattern offset information in response to the detected offset. An offset-responsive controlling device operates for implementing one of (1) changing a response characteristic of a loop formed by the binarizing device and the signal generating device and (2) suspending the slice level control by the binarizing device in response to the code pattern offset information.