Encoder device

Abstract

An encoder device has a main scale with a plurality of slit-like openings at regular intervals, a light-emitting element for emitting and directing substantially parallel rays of light toward the main scale, a light-receiving element including four light-receiving members for receiving light emitted from the light-emitting means via the slit-like openings in the main scale, and a detection unit for detecting a displacement of the main scale by using output signals output from the light-receiving element. The first light-receiving member and the second light-receiving member are positioned a distance apart such that a signal having a phase difference of approximately 270 degrees is obtained therefrom, the first light-receiving member and the third light-receiving member are positioned a distance apart such that a signal having a phase difference of approximately 180 degrees is obtained therefrom, the second light-receiving member and the fourth light-receiving member positioned a distance apart such that a signal having a phase difference of approximately 180 degrees is obtained therefrom, the four light-receiving members are positioned so as to be in an order of the third light-receiving member, first light-receiving member, the second light-receiving member and the fourth light-receiving member in the direction of displacement of the main scale. Accordingly, it is possible to bring the light-emitting member and the light-receiving members closer together and thus make the encoder device slimmer.

Dependencies are inferred from the claim text.