Head positioning controller for information recording and/or reproducing apparatus with head tracking of nonsynchronous radial runout (NRRO) of the disk

An apparatus for recording information on and/or reproducing information from a disk which is an information recording medium, the apparatus comprising:

• a recording/reproducing head;
• a first driving motor that supports and rotationally drives the disk;
• a first encoder unit attached to said first driving motor that detects a rotational speed of said first driving motor and outputs a first signal;
• a second driving motor that supports and rotationally drives said recording/reproducing head;
• a second encoder unit attached to said second driving motor that detects a rotational angle of a rotating part of said second driving motor and outputs a second signal;
• a detection unit that detects a nonsynchronous deflection component of a rotating part of said first driving motor and outputs a third signal, said detection unit comprising a semiconductor laser diode that uses an interference between an emitted beam and a reflected beam;
• and
• a control unit that receives the first signal, the second signal and the third signal, and converts the third signal into a rotational angle of the rotating part of said second driving motor,
• wherein said control unit controls said first driving motor based on a target speed and the first signal, and controls said second motor based on a target position, the second signal and the converted third signal so as to drive said recording/reproducing head to the target position and to compensate the nonsynchronous deflection component.