Patent ID: 8937278
Filing Date: 2015-01-20
Classification: G01B,G01D

Abstract:
1. A rotation angle detecting apparatus, comprising a shaft portion space formed in a rotation shaft, a bearing holder space formed in a bearing holder, a first condenser lens accommodated in said shaft portion space, a second condenser lens provided in said bearing holder space and provided to face said first condenser lens, a detection pattern provided at a focal position of one of said first condenser lens and said second condenser lens, an image sensor provided at a focal position of the other of said first condenser lens and said second condenser lens, and an arithmetic unit for calculating an angle displacement of said rotation shaft based on a signal from said image sensor, wherein said detection pattern has 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, and a reference designation pattern for indicating a reference position of said angle detection pattern, and said arithmetic unit carries out a total circumferential scanning on said track with a predetermined radius with a center of said angle detection pattern as the center in regard to a projection image of said detection pattern obtained by said image sensor, extracts a frequency component, carries out a scanning of said reference designation pattern, and calculates said angle displacement of said rotation shaft 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.