Patent ID: 9080898
Filing Date: 2015-07-14
Classification: G01D

Abstract:
1. An encoder comprising: a slit array comprising a plurality of reflection slits arranged side by side along a measurement axis; and an optical module capable of relatively moving on the measurement axis with respect to the slit array while facing part of the slit array, the optical module comprises: a point light source configured to irradiate the part of the slit array with light; and a light receiving array comprising a plurality of light receiving elements arranged side by side along the measurement axis and arranged around the point light source in a plane parallel to the slit array, the light receiving elements being respectively receiving light irradiated from the point light source and reflected from the reflection slit, the light receiving array includes: a first light receiving array configured to receive reflection light from the slit array comprising an incremental pattern in the measurement axis direction and to output an incremental signal; and a second light receiving array configured to receive reflection light from the slit array comprising an absolute pattern in the measurement axis direction and to output an absolute signal, and the point light source, the first light receiving array and the second light receiving array are arranged in the manner that a shortest distance between the point light source and the first light receiving array is smaller than a shortest distance between the point light source and the second light receiving array.