Patent ID: 8565052

Claim:
A method for correcting repeatable runout (RRO), the method comprising: receiving an open loop tracking signal; squaring the open loop tracking signal; obtaining a discrete Fourier transform (DFT) of the squared open loop tracking signal; determining a velocity magnitude and an absolute value of phase of the open loop tracking signal based on the DFT; and iteratively constructing a RRO correction control signal by: selecting an initial phase based on the absolute value of phase; performing a partial control correction based on the initial phase and an initial velocity amplitude; measuring a relative velocity amplitude; determining if the relative velocity amplitude is smaller than the initial velocity amplitude; performing a partial control correction using the initial phase and the relative velocity amplitude if the relative velocity amplitude is smaller than an initial velocity amplitude; performing a partial control correction using the initial phase rotated by one hundred eighty degrees and the relative velocity amplitude if the relative velocity amplitude is larger than an initial velocity amplitude; and repeating the steps of performing a partial control correction using the initial phase and the relative velocity amplitude if the relative velocity amplitude is smaller than an initial velocity amplitude and performing a partial control correction using the initial phase rotated by one hundred eighty degrees and the relative velocity amplitude if the relative velocity amplitude is larger than an initial velocity amplitude until a tracking controller can perform closed loop control of the track to optical pickup unit velocity, wherein at least one of the preceding actions is performed on at least one electronic hardware component.