Optical encoder

An optical encoder comprising:

• a scale having a scale pattern provided along the measurement direction;
• a head that opposes to the scale and moves relatively to the scale along the measurement direction;
• and
• a calculating unit for performing a calculation based on the relative movement of the scale and the head,
• wherein:
• the head comprises a light source irradiating the scale with light and a light receiving unit having a light receiving surface for receiving light from the light source through the scale;
• the scale includes a step portion formed as a step with a height difference in the scale surface facing at least one of the light source or the light receiving unit;
• the step portion generates interference light having a contrast pattern on the light receiving surface when light is irradiated from the light source, and generate a darkest portion with the highest contrast in the contrast pattern;
• the light source irradiates the step portion with light from a direction inclined with respect to a direction perpendicular to the scale surface;
• and
• the calculating unit includes an origin calculating unit that identifies the darkest portion from the contrast pattern in the interference light received by the light receiving unit through the step portion and calculates the identified darkest portion as the origin position that is a reference of the relative movement between the scale and the head.