Patent ID: 7508323
Filing Date: 2009-03-24
Classification: G01D

Abstract:
1. A rotation-angle detecting apparatus for detecting a rotation angle of a rotating disc having radial markings, comprising: a plurality of detectors arranged at opposite sides of the axis of rotation of the rotating disc and facing said markings, each of the plurality of detectors operable to detect a light beam from said markings, each of said detectors outputting a pair of periodic signals having a 90-degree phase difference between the members of the pair; an analog-to-digital converter arranged to convert a plurality of pairs of periodic signals from the plurality of detectors into a plurality of pairs of digital signals; a digital signal processor configured to process the plurality of pairs of digital signals from the analog-to-digital converter; a binarization unit arranged to binarize the plurality of pairs of periodic signals from the plurality of detectors; and a counter arranged to count the plurality of pairs of periodic signals binarized by the binarization unit, wherein the digital signal processor determines the rotation angle of the rotating disc based on the plurality of pairs of digital signals from the analog-to-digital converter and count results from the counter, and wherein the digital signal processor determines the rotation angle of the rotating disc based on a pair of digital values obtained by averaging the plurality of pairs of digital signals corresponding to the plurality of pairs of periodic signals from the plurality of detectors by performing multiplication, addition, and subtraction, and based on a sum of the count results from the counter.