Patent ID: 8884483

Claim:
An optical entire-circumference encoder comprising: a substrate comprising a first surface and a second surface; a light source disposed on a rotation axis and disposed on the first surface of the substrate; a disc disposed on the second surface of the substrate and rotatable about the rotation axis, the disc comprising a first rotation track and a second rotation track each comprising a plurality of rotating slits disposed around the rotation axis; and a light guiding unit configured to radially guide light radiated from the light source toward an approximately entire outer circumferential area of the disc so as to guide the light to the first rotation track and the second rotation track, the light guiding unit comprising: a first light guiding section comprising an approximately ring-shaped surface directly or indirectly opposed to a rotation track among the rotation tracks, the first light guiding section being configured to radially guide the light so as to make the light go out from the approximately ring-shaped surface toward the first rotation track; and at least two second light guiding sections configured to guide part of the radially guided light to the second rotation track.