| 摘要 |
PURPOSE:To achieve a position detecting signal with good linearity, by writing four detection pulses with different phase toward circumferential direction into a servo track repetitively each 4 tracks and constituting a servo head with a specific width. CONSTITUTION:Position detecting pulses, Q1, Q2, E1 and E2 with different phase are written in each track from a track T1' to track T4' between clock pulse groups C1, C2, and the core width of a signal detecting servo head 20 is made wider than twice the servo track width Tw. When a servo head 20 is moved radially X, the phase relation due to change in amplitude of the Q1, Q2, E1 and E2 pulses is detected to be head position signals. The difference between the Q1 pulse amplitude and the E1 pulse amplitude is a position error signal (solid lines) of the 1st phase, and similarly, the position error signal (dotted lines) of the 2nd phase is obtained, the phase of the position signal is shifted by one track width toward radial (X) direction mutually, the waveform pulse of zero points 1-4 at track boundary is selected and the 4-phase tracks are discriminated. |
