Patent ID: 9587965
Date: 2017-03-07
CPC Classifications: G01D

Claim:
1. A reference signal generation method for an optical encoder, the optical encoder comprising: a scale including a reference point detection pattern and a displacement detection pattern; and a detection head including: a light source that emits light to the scale; a first light-receiving element and a second light-receiving element which receive light emitted from the reference point detection pattern when light is irradiated on the reference point detection pattern by the light source, the first light-receiving element and the second light-receiving element being arranged in parallel in a length measuring direction of the scale; and a main signal detection unit that detects a main signal from light transmitted through the displacement detection pattern, the reference signal generation method comprising: generating a first output signal based on an amount of light received by the first light-receiving element when the detection head is moved along the scale; generating a second output signal based on an amount of light received by the second light-receiving element when the detection head is moved along the scale; performing a first amplitude adjustment to adjust an amplitude of one of the first output signal and the second output signal in such a manner that a level of the first output signal and a level of the second output signal become equal when a phase of the main signal is a first reference phase; performing a second amplitude adjustment to adjust an amplitude of one of the first output signal and the second output signal in such a manner that the level of the first output signal and the level of the second output signal become equal when the phase of the main signal is a second reference phase; and outputting a reference signal that starts at a timing when the level of the second output signal and the level of the first output signal subjected to the first amplitude adjustment become equal and ends at a timing when the level of the second output signal and the level of the first output signal subjected to the second amplitude adjustment become equal.