1. Field of the Invention
The present invention relates to an optical recording/reproducing method and apparatus for recording information onto and reproducing information from a phase-change storage medium, such as a DVD-rewritable.
2. Description of the Related Art
DVDs (digital versatile disks) are read-only optical recording media and have their rewritable equivalents, DVD-rewritable disks. DVD-rewritable disks are phase-change storage media that use a process called the phase change technology to write and erase data.
The process writes data to a DVD-rewritable disk by focusing a high-intensity laser beam on a layer of a phase-change material embedded in a plastic base or a substrate of the disk. In its original state of the phase-change material, this layer has a rigid crystalline structure. The laser beam selectively heats areas of a surface portion of the disk to a high temperature. Where the beam strikes, the heat melts the crystals to a non-crystalline, or amorphous phase. These areas reflect less light than the unchanged area surrounding them.
Later, when a weaker laser beam, used only to read data from the recorded disk, strikes the non-crystalline area, the beam is scattered and hard to be picked up by the light-sensitive diode in the read head of the disk drive. With the lower reflectance, these areas become marks, representing xe2x80x9c1xe2x80x9ds. Areas that are not heated are more reflective areas, representing xe2x80x9c0xe2x80x9ds. When the read laser beam strikes the areas, it is reflected directly to the light-sensitive diode of the read head, creating an electrical current that is sent to the controller in the drive. The controller interprets the pattern of electrical pulses, decodes the data that they represent, checks the data for error, and sends the data to a computer.
To erase data or to change a mark back to crystalline phase, DVD-rewritable disk drives use a lower-energy laser beam to heat marked areas to a comparatively low temperature. This amount of heat is below the melting point of the phase-change material, but it still loosens up the phase change media so that it can recrystallize to its original state.
Recently, there is the demand for using a DVD player or the like to reproduce data from a DVD-rewritable disk (or a phase-change storage medium). The DVD player is originally designed to use a laser beam to read the pits of DVD or DVD-ROM disks (or the read-only optical storage media). On the read-only optical storage media, various data blocks are recorded in a seamless formation. If data blocks are recorded on the phase-change medium in a seamless formation that is essentially the same as that of the read-only optical storage media, data can be easily reproduced from the phase-change medium by using the DVD player without a need for substantial changes of the DVD player. This will increase the operability and compatibility of DVD-rewritable media, which considerably benefits the users.
Generally, in optical disk drives using the phase-change media, if data is repeatedly written to a same data block on the phase-change disk, the recording properties of the disk will deteriorate and a defect in the data block will take place. In such a case, the optical disk drives do not effectively reproduce the data from the disk. There are three types of the deterioration pattern that may be revealed in the phase-change media.
The first type is that, if data is repeatedly written to a head end of one data block, defective areas are transferred from the head end of the data block to the following areas in the forward direction. The second type is that, if data is repeatedly written to a tail end of one data block, defective areas are transferred from the tail end of the data block to the preceding areas in the backward direction. The final type is that, if a same pattern of marks is repeatedly recorded onto a same position of one data block, defective areas are transferred from that position in both the forward direction and the backward direction.
The larger the energy of the laser beam applied to overwrite recording marks at the same position of the phase-change disk, the severer the deterioration of the recording properties of the disk.
In order to eliminate the above problem, a conventional optical recording/reproducing apparatus is configured to vary the position of each complete data block in the disk when overwriting data. See, for example, Japanese Patent No.2720876 (which corresponds to Japanese Laid-Open Patent Application No.9-180191). However, the changes of the position of each complete data block is unsuitable for an optical disk drive that records data blocks onto the optical disk in a seamless formation. In the conventional apparatus, the sync positions of data blocks are greatly shifted from each other and it is difficult to create a read clock signal the phase of which is accurately synchronized with the read clock signal of the following data block when reproducing data from the optical disk.
In order to eliminate the above problem, another conventional optical recording/reproducing apparatus is configured to add dummy data to the head end and tail end of each data block and vary the position of the entire data block in the disk so as to protect the recorded data. See, for example, Japanese Laid-Open Patent Application No. 9-219022. However, the changes of the position of the entire data block are unsuitable for an optical disk drive that records data blocks onto the optical disk in a seamless formation.
Another conventional optical recording/reproducing apparatus is configured to produce a write clock signal precisely synchronized with rotation of an optical disk. See, for example, Japanese Laid-Open Patent Application No.10-293926. However, the write clock signal produced is unsuitable for an optical disk drive that records data blocks onto the optical disk in a seamless formation. It is difficult for the above conventional apparatus to create a read clock signal the phase of which is accurately synchronized with the read clock signal of the following data block when reproducing data from the optical disk.
In addition, in the above conventional apparatus, when reproducing data from the optical disk, there is a problem in that the phase of the read clock signal obtained from the preceding data block and the phase of the read clock signal obtained from the next data block are apart from each other by nearly 180 degrees. It is highly possible that the data recorded at the boundaries between the adjacent data blocks on the optical disk are lost.
As described above, in the above-mentioned conventional apparatuses, the gaps between adjacent data blocks are provided, or the dummy data are added to the head end and tail end of each of the data blocks. It is difficult for the above-mentioned conventional apparatuses to record data blocks onto the phase-change disk in a seamless formation while effectively reducing the deterioration of the recording properties of the disk.
In order to overcome the problems described above, preferred embodiments of the present invention provide an improved optical recording/reproducing method and apparatus that accurately records data blocks onto the phase-change disk in a seamless formation while effectively reducing the deterioration of the recording properties of the disk.
According to one preferred embodiment of the present invention, an optical recording/reproducing method for accessing an optical storage medium in which binary data are recorded by applying a light beam to a recording layer of the storage medium and changing a state of the recording layer on a disk drive, includes the steps of: receiving a data signal to record a sequence of data blocks onto the storage medium, each data block having a predetermined block length from one end of the data block to the other end; varying each of the data blocks in length such that data bits are arbitrarily added to or removed from at least one of the ends of the data block in order to allow the data blocks to be written to the storage medium in a seamless formation, the data bits having a predetermined length; and recording the resulting data blocks on the storage medium at fixed positions.
In the optical recording/reproducing method of the above preferred embodiment, the data blocks are recorded onto the optical disk in the seamless formation, and the optical recording/reproducing method is effective in accurately recording data blocks onto the phase-change disk in a seamless formation and in reducing the deterioration of the recording properties of the disk.
According to another preferred embodiment of the present invention, an optical recording/reproducing method for accessing an optical storage medium includes the steps of: receiving a data signal to record a sequence of data blocks onto the storage medium, each data block on the storage medium having a predetermined block length from one end of the data block to the other end and being divided into a number of frames each of which has an information unit that always appears at a same position within the frame with a fixed length when recording of data onto a same portion of the storage medium is repeated; and forming, when marks are recorded onto the storage medium, the information unit of each of the frames in the sequence of data blocks such that the information unit consists of marks of a plurality of sub-units.
The optical recording/reproducing method of the above preferred embodiment is effective in reducing the deterioration of the recording properties of the optical disk on which data blocks are recorded in a seamless formation. It is possible to increase the recording repeatability and the operational life of the optical disk.
According to another preferred embodiment of the present invention, an optical recording/reproducing method for accessing an optical storage medium in which binary data are recorded by applying a light beam to a recording layer of the storage medium and changing a state of the recording layer on a disk drive, includes the steps of: calibrating the disk drive with the storage medium so that a phase error of a readout signal relative to a phase of a recording pulse based on a position-information carrying signal obtained from the storage medium is detected; and adjusting the phase of the recording pulse so as to reduce the phase error of the readout signal.
In the optical recording/reproducing method of the above preferred embodiment, the read clock signal and the write clock signal can accurately accord in phase, and it is possible to prevent the occurrence of a read error when reproducing data from the disk.
According to another preferred embodiment of the present invention, an optical recording/reproducing apparatus for accessing an optical storage medium includes: a read clock generating unit for generating a read clock signal in response to recorded data on the storage medium; a write clock generating unit for generating a write clock signal in response to a position-information carrying signal detected from the storage medium; a detection unit for detecting a phase difference between the read clock signal and the write clock signal when writing data blocks to the storage medium in a seamless formation; and a determination unit for determining whether a phase of the read clock signal is delayed or advanced based on the phase difference detected by the detection unit, wherein the determination unit produces a control signal to adjust a phase of the position-information carrying signal.
In the optical recording/reproducing apparatus of the above preferred embodiment, when the optical disk is recorded in a seamless formation, the read clock signal and the write clock signal can accurately accord in phase, and it is possible to prevent the occurrence of a read error when reproducing data from the disk.