This application claims the benefit of a Japanese Patent Application No. 2001-163255 filed May 30, 2001, in the Japanese Patent Office, the disclosure of which is hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to seek control methods and storage apparatuses, and more particularly to a seek control method for making a seek to a desired track on a recording medium such as an optical disk, and to a storage medium which employs such a seek control method.
2. Description of the Related Art
In a conventional magneto-optical disk, a track to which information is recorded and from which the information is reproduced, is formed in a land or a groove of the magneto-optical disk. In addition, a ROM region which is recorded with control information such as information peculiar to the medium is provided in an inner peripheral zone of the magneto-optical disk, and a RAM region to which data is recorded and from which the data is reproduced is provided in other zones, for example. In the ROM region, the control information is recorded as variations in geometrical configuration such as pits. In the RAM region, the data is recorded and reproduced by a magneto-optical system.
A seek to a desired track on the magneto-optical disk may be carried out within the RAM region, from the RAM region to the ROM region or, from the ROM region to the RAM region. Normally, when making the seek to the desired track from an arbitrary track, a tracking error signal (TES) is used. More particularly, a number of tracks traversed is counted from a time when a light beam spot starts to move from the arbitrary track by use of the TES, so as to detect whether or not the desired track is reached.
Generally, when a moving distance of the light beam spot during the seek is long, a moving speed of the light beam spot becomes high, and there is a possibility of making an error when the number of tracks traversed is counted using the TES. However, a track pitch of the conventional magneto-optical disk is relatively large, and a ratio of TES amplitudes obtained in the RAM and ROM regions is 1:08, for example, and a difference between the TES amplitudes obtained in the RAM and ROM regions is not very large. For this reason, the possibility of making an error when the number of tracks traversed is counted using the TES is small even when the seek is made from the RAM region to the ROM region.
However, in addition to the magneto-optical disk unit which records and/or reproduces (records/reproduces) information with respect to only the land or the groove of the magneto-optical disk, a magneto-optical disk unit has been proposed which records/reproduces the information with respect to both the land and the groove of the magneto-optical disk. By employing the so-called land-groove recording system which records the information on both the land and the groove of the magneto-optical disk, it is possible to increase the recording density on the magneto-optical disk.
In the magneto-optical disk which employs the land-groove recording system, the track pitch is extremely small. Hence, it is necessary to amplify the TES to make it easier to read the TES and prevent an error from being made when counting the number of tracks traversed.
But in the case of the magneto-optical disk which employs the land-groove recording system, the ratio of the TES amplitudes obtained from the RAM and ROM regions is 1:0.4, for example, and the difference between the TES amplitudes obtained in the RAM and ROM regions is large. For this reason, even when the TES is amplified, the possibility of making an error when counting the number of tracks traversed is large if the same circuit is used to read the TES obtained from the RAM and ROM regions. In other words, if the sensitivity of the count is adjusted to suit the TES obtained from the RAM region, the sensitivity becomes insufficient for reading the TES obtained from the ROM region. On the other hand, if the sensitivity of the count is adjusted to suit the TES obtained from the ROM region, the sensitivity becomes too sensitive for reading the TES obtained from the RAM region.
If the error is generated when counting the number of tracks traversed, the desired track cannot be reached by one seek, and it takes time to complete the seek because of the need to carry out a seek retry a number of times. Particularly when loading the magneto-optical disk, it becomes necessary to first make a seek to the ROM region in order to read the control information such as the storage capacity and disk type of the loaded magneto-optical disk, but it is undesirable that a long time is required to make this seek.
In addition, when the circuit is designed to suit the TES amplitude obtained from the RAM region, the TES cannot be detected correctly from the ROM region, and a tracking servo cannot be carried out normally in the ROM region. Similarly, when the circuit is designed to suit the TES amplitude obtained from the ROM region, the TES cannot be detected correctly from the RAM region, and a tracking servo cannot be carried out normally in the RAM region. Therefore, in either case, it becomes impossible to obtain an on-track state with respect to the desired track.