Patent ID: 7663093
Filing Date: 2010-02-16
Classification: G01D

Abstract:
1. An absolute position encoder comprising: a scale having formed therein a first incremental track with first incremental patterns including first light and dark patterns formed at equal intervals in first periods, an absolute track with absolute patterns representing absolute positions, and a second incremental track with second incremental patterns including second light and dark patterns formed at equal intervals in second periods longer than the first periods; a light source emitting a measurement light to the scale; a photodetector receiving the measurement light reflected at or transmitted through the scale; and a signal processing circuit processing the received light signal of the photodetector to detect an absolute position of the scale, wherein the absolute patterns and the second incremental patterns are formed on the same track, and the second incremental patterns and the absolute patterns are integrated, and wherein the integration of the second incremental patterns with the absolute patterns is performed in such a way that patterns are formed only in those regions where both the absolute patterns and the second incremental patterns exist.