Patent ID: 7439489

Claim:
A photoelectric encoder including a light emitting element and a light receiving section to detect a movable object which has a light transmitting/reflecting zone for transmitting or reflecting light emitted from the light emitting element toward the light receiving section and a light non-transmitting zone for blocking light emitted from the light emitting element, wherein the light receiving section for receiving light derived from the light emitting element and transmitted or reflected by the light transmitting/reflecting zone in the movable object is composed of 2n (n is an integer, where n≧2) light receiving elements which are provided side by side in succession within a region having a width L times (L is a natural number, L and 2n are coprime to each other) larger than one pitch P of the light transmitting/reflecting zone or the light non-transmitting zone of the movable object, the photoelectric encoder further comprising: a first rectangular-wave generation section for, in every one cycle T during which the light transmitting/reflecting zone and the light non-transmitting zone travel by the one pitch P, generating 2n rectangular waves whose phases differ from one another in units of 360°/4n and each of which has a cycle T, based on output signals from the 2n light receiving elements; and a second rectangular-wave generation section for, in every one cycle T, generating 2 rectangular waves whose phases differ from each other in units of 360°/4n and each of which has a cycle (1/n)T, based on the 2n rectangular waves generated by the first rectangular-wave generation section.