Patent ID: 8305586

Claim:
An optical encoder comprising: a linear power transmission member which moves longitudinally; a reflector which is fixed onto an outer peripheral surface of the linear power transmission member and which is longitudinally movable integrally with the linear power transmission member, the reflector including a slit portion in which two kinds of reflecting portions different in reflectance are longitudinally arranged with a predetermined pattern; a light source which radiates light; a linear light transmitter which guides the light from the light source to the slit portion and to which reflection light reflected from the slit portion is guided; and a holding member which longitudinally movably holds the linear power transmission member and the reflector and also holds the linear light transmitter at such a position that allows the light to enter the slit portion and allows the reflection light from the slit portion to be guided; a light receiving element which receives the reflection light in the slit portion guided from the linear light transmitter and which detects an electric signal indicating a displacement of the reflector and a light amount; a signal processing mechanism configured to convert the electric signal into a pulse signal having a predetermined threshold; and a calculation mechanism configured to calculate the longitudinal displacement of the reflector from a number of pulses of the pulse signal.