Patent ID: 8130427

Claim:
A method of generating an origin signal of an encoder having a scale on which an incremental pattern and an origin pattern are formed, the method comprising detecting a variable origin position during an initial operation following power-on of the encoder and memorizing said origin position, wherein the origin position detected during the initial operation after power-on of the encoder is a position of a detection head of the encoder at a time of power-on of the encoder, the origin position being a position of the encoder at a time of an immediately preceding power-off, and generating an origin signal having a necessary position and width by software based on the detected origin position and an origin waveform obtained from the origin pattern, wherein, the origin signal is generated in synchronization with a main signal waveform obtained from the incremental pattern, and the origin position detected during the initial operation following power-on of the encoder is indicated until a subsequent power-off of the encoder.