Optical encoder with a beam-shaping element

An optical encoder, comprising:

• a scale having a scale grating arranged with a predetermined period along a measurement direction;
• a light source that emits light toward the scale;
• and light-receiving means that has a light-receiving area, the light-receiving area having multiple light-receiving elements arranged with a predetermined period in the measurement direction, and receiving light that has passed through the scale, wherein:
• the optical encoder comprises a beam-shaping element that shapes the beam shape, which is the shape of the light emitted from the light source, wherein
• the beam-shaping element is a single opening disposed between the light source and the scale, and
• the beam-shaping element defines the beam shape such that a shape of a long-length contour portion and a shape of a long-length side section have no correlation with each other, wherein
• the long-length contour portion is a portion of the beam shape extending in the measurement direction at a contour of the beam shape of the light from the light source to be emitted to the light-receiving means via the scale, and the long-length side section is a section of the light-receiving area extending in the measurement direction at a contour of the light-receiving area,
• the beam-shaping element includes a beam-shaping part with edges having predetermined shapes;
• and
• the predetermined shape of an edge of the beam-shaping part defining the long-length contour portion includes multiple circular arcs with a common radius.