Absolute encoder

摘要

Provided is an absolute encoder capable of detecting the absolute angle at high resolution and with high precision. An image sensor receives light in an absolute value code pattern of a scale, an edge detecting unit detects from the received light signal an edge pixel position and an edge direction, and an edge position correcting unit corrects the edge pixel position based on the edge direction. A phase detecting unit detects from the corrected edge pixel position the phase shift amount of a shift from a reference pixel position of the image sensor, and a high precision detection unit uses a rough absolute position detected by a rough detection unit and the phase shift amount detected by the phase detecting unit to detect the absolute position with high precision.

主权项

1. An absolute encoder, comprising:
a scale comprising an absolute value code pattern; a light emitting element for irradiating the scale with light; an image sensor for receiving light from the scale; an A/D converter for converting an output from the image sensor into a digital output; and an absolute position computing unit, wherein the absolute position computing unit comprises:
an edge detecting unit for detecting, based on a signal strength of a signal from the A/D converter and a threshold level that is set in advance, an edge pixel position of the absolute value code pattern on the image sensor, and an edge direction of the absolute value code pattern at the edge pixel position; andan edge position correcting unit for correcting the edge pixel position that is acquired by the edge detecting unit in a manner that varies depending on whether the detected edge direction is a rising edge or a falling edge, and wherein the absolute position computing unit acquires an absolute position of the scale based on the corrected edge pixel position.