Patent ID: 9065468
Filing Date: 2015-06-23
Classification: G01D,H03M

Abstract:
1. An encoder signal processing circuit, connected to encoder heads outputting an encoder signal in accordance with a relative displacement with respect to a corresponding scale in such a way that signals can be transmitted to and received from the encoder heads, which processes encoder signals from the encoder heads, the circuit comprising: a processing unit that generates displacement information from the encoder signal; and a processing decision unit that decides at least one of content of processing for the encoder heads and content of processing on encoder signals read from the encoder heads after starting to read an encoder signal from one of the encoder heads; wherein the processing for the encoder head is the processing in which the processing decision unit selects from among the encoder heads or changes the encoder head from which an encoder signal is next read, the encoder signals are periodic signals, the encoder heads are unable to detect a position if the encoder signal exceeds a fixed period between two continuous read times, the encoder signal processing circuit further comprises a maximum permissible displacement holding unit that holds a maximum permissible displacement indicating a limit value of the relative displacement permitted between the two continuous read times of the encoder signal for each of the encoder heads, and the processing decision unit calculates a latest readable time as a latest read time of the encoder signal for each of the encoder heads while maintaining signal processing of each of the encoder heads in the processing unit by using the maximum permissible displacement corresponding to each of the encoder heads and compares the latest readable times calculated for each of the encoder heads to decide, from among the encoder heads, the encoder head from which the encoder signal is next read.