Encoder using a birefringent element and a system including the same

摘要

An encoder includes a light illuminating device, an optical scale and a photosensor, and detects information of relative displacement between the scale and the illuminating light. A birefringent element, such as a Savart plate or the like, is disposed in the optical path between the light illuminating device and the photosensor to generate a plurality of images of the scale having different phases. A plurality of output signals having a phase difference are obtained using the images of the scale.