Patent ID: 8476577

Claim:
An optical encoder comprising a scale, which has scale markings, and a readhead, which has a light source that emits light to the scale and a light receiving element that is arranged in parallel with the scale to receive the light reflected by the scale, so that a position of the readhead with respect to the scale is measured based on the light received by the light receiving element, wherein the readhead has a scale-side lens that transmits the light emitted from the light source to the scale and transmits the light reflected by the scale to the light receiving element, wherein the light source is arranged between the scale-side lens and the light receiving element, and wherein an optical axis of the light source is matched with an optical axis of the scale-side lens in a reading direction of the scale markings and is separated from an optical axis of the scale-side lens by a predetermined distance in a direction perpendicular to a reading direction of the scale markings.