Patent ID: 6772101
Filing Date: 2004-08-03
Classification: G01D

Abstract:
A position detection apparatus comprising:a recording medium on which a periodic position signal is recorded; a detection section having a first detection head that moves relative to said recording medium along a recording direction of said position signal for detecting said position signal and a second detection head disposed apart from said first detection head by a predetermined distance along said recording direction of said position signal that moves relative to said recording medium and that operates with said first detection head for detecting said position signal; a polar conversion section for converting said position signal detected by said first detection head and said second detection head into an angle signal that represents a relative position of said recording medium and said detection section as an angle; a low pass filter for removing a high frequency component in said angle signal output from said polar conversion section to output a smoothed angle signal having a frequency such that a phase error is zero; and an output section for outputting relative position information of said recording medium and said detection section based on said smoothed angle signal from which said high frequency component has been removed by said low pass filter, wherein said low pass filter comprises: a frequency control oscillator for outputting a periodic signal having a frequency controlled based on a frequency control signal; a phase comparator for comparing a phase of said angle signal output from said polar conversion section and said periodic signal output from said frequency control oscillator to output said phase error; first gain-controllable amplifier means for one of increasing and decreasing said phase error output from said phase comparator; second gain-controllable amplifier means for one of increasing and decreasing said phase error output from said first gain-controllable amplifier means; an integrator for integrating said phase error output from said second gain-controllable amplifier means to output a velocity error; and an adder for adding said velocity error output from said integrator and phase error output from said first gainfier controllable amplifer means to generate said frequency control signal, wherein said frequency control oscillator controls said frequency of said periodic signal such that said phase error is zero based on said frequency control signal and outputs said periodic signal as said smoothed angle signal from which said high frequency component has been removed.