Patent ID: 7266567

Claim:
An absolute encoder comprising: a plurality of slit streams having different pitch numbers from each other, in which positional information of the same pitch is formed; a plurality of sensors which are relatively moved with respect to said slit streams so as to detect said positional information; a phase modulating section for converting a signal derived from said sensor into a phase signal; a phase difference signal producing section for converting both said phase modulation signal and a phase difference signal between two pieces of arbitrary phase signals into a digital signal; and an absolute value signal producing section for producing a signal which is related to an absolute value position in a constant time period based upon the digital signal converted by said phase difference signal producing section and the phase difference signal; wherein: the absolute encoder is arranged by: a first memory for storing thereinto an absolute value signal which is produced by said absolute value signal producing section every constant time period; a second memory for storing thereinto an absolute value signal which has been produced in one-preceding time period with respect to a time period of an absolute value signal entered into said first memory; a comparing/calculating section for comparing the absolute value signal stored in said first memory with the absolute value signal which has been produced in said one-preceding time period and has been stored in said second memory so as to calculate an increase/decrease amount; a dividing process section for dividing said increase/decrease amount in an equal rate within a producing time period of said absolute value signal; and an interpolated absolute value signal producing section for reading the absolute value signal which has been produced in said one-preceding time period, and thereafter, for adding/subtracting said divided increase/decrease amount in a stepwise manner with respect to the read absolute value signal wherein the absolute encoder is operable to provide the result of adding/subtracting as a position information.