1. Technical Field
The present invention relates to an improved information-retrieval apparatus. In particular, the present invention relates to an improved digitally-based information-retrieval apparatus. More particularly, the present invention relates to magnetic storage media, such as digital recording tapes. Still more particularly, the present invention relates to magnetic recording heads for writing and reading data to digital recording tapes.
2. Description of the Related Art
Various magnetic recording techniques exist for recording data to and from magnetic storage media, such as magnetic tape. Magnetic tapes are used for data storage in computer systems requiring data removability, low-cost data storage, high data-rate capability, high volumetric efficiency and reusability. The constantly increasing operational speeds of digital computers are creating a demand for corresponding increases in the data storage capacities of magnetic tape recording and reproducing systems, while maintaining the special requirements of high speed digital tape systems.
Tape recording and reproducing systems for use as computer data storage devices are required to provide high data transfer rates and to perform a read check on all written data. To satisfy these requirements, conventional tape systems typically employ methods of recording known as linear recording, in which the tracks of data lie parallel to each other and to the edge of the tape. Linear recording techniques offer high data transfer rates. However, it is desirable to obtain even higher data densities while retaining the advantages of such recording techniques.
Digital linear tape (DLT) is a magnetic linear tape medium that is increasingly being utilized as a medium for data storage. DLT is a magnetic storage medium used to back up data, typically in computer systems. DLT allows for the rapid transfer of data, in comparison to other tape storage technologies. For example, various forms of magnetic read/write heads can be utilized in association with servo mechanisms to read and write data to and from a track of a particular DLT.
Because DLT is currently being utilized as an important tool for data storage, it is desirable to increase the recording density, thus allowing for the faster and more efficient retrieval and writing of data. One method of increasing this storage density involves azimuth recording. The term "azimuth" refers to the horizontal angular distance from a particular reference direction. The use of the word "azimuth" in "azimuth recording" thus suggests a form of angular recording.
Azimuth recording involves the use of a rotating recording head, such that data tracks on a tape may be recorded at different angles with respect to the edge of the tape. Azimuth recording results in a recorded track pattern in which the magnetization directions of adjacent data tracks lie at different azimuth angle to each other. To date, most recording systems have relied strictly on magnetic heads which contain read/write elements but which record only vertically, thus not allowing for angular or "azimuthal" recording of data. One of the principal advantages of azimuth recording over non-azimuth recording is that azimuth recording promotes very high data track packing. Azimuth recording provides much denser track packing than regular track packing spacing because regular track packing spacing typically requires gaps between tracks.
Those systems which do attempt to implement azimuth recording techniques are faced with the challenge of providing fine positioning servo tracking. Servo tracking techniques have been developed to reduce the effects of tracking error and thus improve the data capacity of tape systems. Known servo techniques vary widely, but most involve methods of dynamically moving a read head gap to continually reposition it over a written servo track. The movement of a servo read head gap compensates for lateral tape motion during a read. However, lateral tape motion during writing is not controlled with respect to the write head gap. Thus, the distance between tracks is still limited to the magnitude of the lateral tape motion in order to avoid over-writing previously written tracks.
Based on the foregoing it can be appreciated that a need exists for an improved azimuth recording system which does not encounter problems associated fine positioning servo tracking. A need also exists for an inexpensive and easy to implement apparatus and method which provides fine positioning servo tracking. It is believed that the apparatus and method presented herein solves these problems.