The present invention relates to a method of recording servo information whereby servo information which is used to position a head is written onto a servo surface of a magnetic disk by using a servo track writer and, more particularly, to a servo information recording method whereby servo information is written and, thereafter, the servo information is read out and is verified to discriminate whether the servo information has correctly been recorded or not.
In the manufacturing steps of a magnetic disk apparatus, at a time point of the completion of the assembly of a disk enclosure, servo information is written onto the servo surface of a magnetic disk in the disk enclosure by using a servo track writer. The writing step of the servo information comprises: a step called a laser mode for writing the servo information onto the servo surface of the magnetic disk while precisely measuring a rotational angle of a voice coil motor by a laser length measuring device; and a step called a magnetic mode for reading out the servo information written on the servo surface of the magnetic disk and on-track controlling the head by a position signal derived from a read signal, thereby verifying a quality of the servo information.
A conventional servo information recording method by the servo track writer will be further described in detail. In the laser mode, first, the head position is detected by the laser length measuring device and the servo head is precisely positioned to a track position at which the servo information should be written. Subsequently, the servo information is written to one circumference of the track of the magnetic disk medium by the servo head. Remaining tracks are done in similar fashion. Such a writing process of the servo information is repeated in the direction from the outer track of the magnetic disk toward the inner track.
After the servo information was written in the laser mode, the quality of the written servo information is verified in the magnetic mode. That is, the servo information written on the magnetic disk is read out by the servo head and a position signal is formed. The servo head is positioned over the track (on-track) by the servo control based on the position signal. A read signal of the servo information which is obtained in an on-track state of the servo head is supplied to a hardwired verifying circuit thereby verifying the quality of the servo information. The verifying circuit discriminates whether pulses in the read-out background of the servo information are missing or not, whether extra pulses exist or not, and the like. After the servo information of one track was verified, the servo head is sought to the next track. Such a verifying process is repeated in the direction from the outer track to the inner track of the magnetic disk medium.
However, such a conventional recording method using the servo track writer has a problem in that it takes a long time to write and verify the servo information. First, in the laser mode, it takes a time corresponding to a total of two rotations of the disk: One rotation of the disk in order to write the servo information per track and one rotation in order to control the operation to seek the servo head to the next track. Therefore, a processing time in the laser mode is equal to the time which is obtained by multiplying the total number of tracks to the time which is required for two rotations of the disk. In the magnetic mode, it takes a time corresponding to total two rotations of the disk: One rotation to read out the servo information per track and one rotation for the seeking control to the next track. Therefore, a processing time in the magnetic mode is equal to the time which is obtained by multiplying the total number of tracks to the time which is required for two rotations of the disk. Thus, the time necessary to write and verify the servo information is equal to the time which is obtained by multiplying the total number of tracks to the time that is required for four rotations of the disk.
Additionally, since a special verifying circuit constructed by the hardware is needed, costs are high and the verifying circuit is influenced by noises due to the characteristics of the verifying circuit or the like, an adjustment to accurately perform the inspection is troublesome.