Patent ID: 9228858
Filing Date: 2016-01-05
CPC Classification: G01B,G01D

Claim Text:
1. A rotation angle detecting apparatus, comprising a detection pattern, an image sensor on which said detection pattern is projected and capable of relatively rotating with respect to said detection pattern, and an arithmetic unit for calculating an angle displacement between said detection pattern and said image sensor based on a signal from said image sensor, wherein said detection pattern comprises an angle detection pattern in which bar-like line segments extending in a radial direction are arranged at a predetermined angle pitch and a ring-like track is formed by bar-like line segments, a reference designation pattern for indicating a reference position of said angle detection pattern, and a centering pattern provided at a center of said angle detection pattern, a X-Y rectangular coordinate is set on said image sensor, said arithmetic unit coarsely detects a center of said detection by scanning said centering pattern in two directions of X axis and Y axis, in regard to a projection image of said detection pattern obtained by said image sensor, carries out two or more total circumferential scanning on said track with a circle with a coarse center obtained by coarse detection as the center, extracts a frequency component and scans said reference designation pattern, and calculates the angle displacement between said detection pattern and said image sensor based on a phase difference of said frequency component and the number of frequencies corresponding to a change in position of said reference designation pattern.