Disk drive, position detection device and method of correction of position detection signal

A disk drive comprising:

• a head arm having a head;
• a motor for rotating said head arm on an axis thereof to move said head in a direction across a track on a disk;
• a tracking position detection device for detecting a tracking position of said head by detecting a position of said head arm portion moving with said head;
• and
• a motor drive portion for driving said motor based on information from said tracking position detection device,
• wherein said tracking position detection device comprises,
• a detector for outputting two position detection signals having a predetermined phase difference as said head moves;
• and
• a signal processor for performing signal processing on said two position detection signals and providing information used in controlling the motor,
• and further wherein said detector outputs four position detection signals having phases successively shifted by 90 degrees along with movement of said head;
• and
• a signal processor obtains a reference voltage level by averaging at least two of said position detection signals.

A position detection device, comprising:

• a detector for outputting four position detection signals having phases successively shifted by 90 degrees along with movement of the object;
• and
• a signal processor for obtaining a reference voltage level by averaging said four position detection signals,
• wherein said signal processor corrects an amplitude of a position detection signal by using two position detection signals having a phase difference of 90 degrees.

A position detection device, comprising:

• a detector for outputting four position detection signals having phases successively shifted by 90 degrees along with movement of the object;
• and
• a signal processor for obtaining a reference voltage level by averaging said four position detection signals;
• wherein said detector comprises:
• a light emitter;
• a reticle having a plurality of slits;
• a scale having a plurality of slits repeating at a constant pitch and relatively moving with respect to said reticle along with movement of an object being detected;
• and
• a light receiver for receiving light from said light emitter passing through said reticle and said scale and outputting four position detection signals having phases successively shifted by 90 degrees forming triangular waves due to a change of relative positions of said slits along with movement of said scale.

A position detection device, comprising:

• a detector for outputting four position detection signals having phases successively shifted by 90 degrees along with movement of the object;
• and
• a signal processor for obtaining a reference voltage level by averaging said four position detection signals,
• wherein between said detector and said signal processor is provided a detection circuit for amplifying said four position detection signals from the detector.

A position detection device, comprising:

• a detector for outputting four position detection signals having phases successively shifted by 90 degrees along with movement of the object;
• and
• a signal processor for obtaining a reference voltage level by averaging said four position detection signals further comprising:
• a selector for selecting one of said four position detection signals;
• and
• an A/D converter for converting a position detection signal selected by said selector from an analog signal to a-digital signal and outputting the result to said signal processor.

A position detection device, comprising:

• a detector for outputting four position detection signals having phases successively shifted by 90 degrees along with movement of the object;
• and
• a signal processor for obtaining a reference voltage level by averaging said four position detection signals further comprising:
• four A/D converters for converting said position detection signals from analog signals to digital signals and outputting the results to said signal processor.