Patent ID: 9127967
Filing Date: 2015-09-08
Classification: G01D

Abstract:
1. An encoder comprising: a scale that includes a pattern row that has a plurality of patterns configured to spatially modulate an energy distribution; a detector array that includes a plurality of detectors that are configured to detect the energy distribution from the pattern row and arranged in a moving direction, the detector array being configured to move relatively to the scale; and a signal processor configured to process and convert into positional information, an output signal from the detector array, wherein the pattern row has a first modulation period and a second modulation period different from the first modulation period in the moving direction, and wherein the signal processor includes: a first phase acquirer configured to acquire a first phase of the first modulation period based on the output signal of the detector array; a second phase acquirer configured to acquire a second phase of the second modulation period based on the output signal from the detector array; and a positional information acquirer configured to acquire Sv as a position signal that represents a position of the scale in the moving direction, wherein Sv satisfies: where A and B are coefficients that satisfy A/B=n/m using integers m and n that satisfy: where Φ