Position detecting method for use in optical system of a video camera for correcting gain and offset for periodic waveforms

Claim 1

A position detecting method for detecting a position of a moving object by sensing a plurality of repetitive periodic waveforms provided from a position sensor and related to said moving object relative to a reference position, and performing data processing on said plurality of repetitive periodic waveforms to provide corrected repetitive periodic waveforms having corrected gain and offset values, comprising the steps of: moving said moving object by a distance to produce more than one period of said plurality of repetitive periodic waveforms; detecting a maximum value and a minimum value of each of said plurality of repetitive periodic waveforms; obtaining, based on the detected maximum value and the minimum value, an offset value and a gain of each of said plurality of repetitive periodic waveforms; correcting the offset values and the gains of said plurality of repetitive periodic waveforms so that the offset values match each other and the gains match each other; correcting each of said plurality of repetitive periodic waveforms based on the corrected offset values and gains to provide corrected repetitive periodic waveforms representing corrected data representative of movement of said moving object; and detecting the position of the moving object based on the corrected repetitive periodic waveforms; wherein, when a velocity of the moving object has exceeded a predetermined value, detection of said maximum value and said minimum value is stopped and said plurality of repetitive periodic waveforms are corrected based on an offset value and a gain obtained before the detection is stopped.