Patent ID: 8546747
Filing Date: 2013-10-01
Classification: G01D

Abstract:
1. A rotary encoder comprising: a rotary scale including a spiral pattern, whose center is located at a rotation axis of the rotary scale, whose radius continuously changes in a rotation direction of the rotary scale, whose width and pitch in a radial direction of the rotary scale are constant, and whose reflectance or transmittance changes in the rotation direction; a sensor unit disposed facing the rotary scale and including a light source that illuminates the spiral pattern and a first light-receiving part that detects light entering thereinto via the spiral pattern; and a signal processor, wherein the first light-receiving part is constituted by a first sensor array group including at least two sets of sensor arrays arranged at mutually different radial position, wherein the first sensor array group receives light from a first reading area located on the rotary scale and illuminated by the light source, wherein an area through which the first reading area is rotated on the rotation axis of the rotary scale includes at least one cycle of the spiral pattern, wherein the first sensor array group outputs sinusoidal signals corresponding to a radial cycle of the spiral pattern, wherein the signal processor produces a first phase signal from two phase sinusoidal signals produced based on the sinusoidal signals output from the first sensor array group, and wherein the signal processor produces, based on the first phase signal, a rotational angle signal showing a rotational angle of the rotary scale.