Patent ID: 9360347
Filing Date: 2016-06-07
CPC Classification: G01B,G01D,G02B,G03F

Claim Text:
1. An encoder system structured to measure relative movement between first and second members, the encoder system comprising: an encoder head disposed on one of the first and second members, the second member being moveable relative to the first member along a first line in a first direction; and a diffraction grating disposed on another of the first and second members such that, when the encoder head directs a measuring beam of light incident thereon to a first position on the grating, the grating forms, from said measuring beam directed by the encoder head, first and second diffracted measuring beams at first and second angles with respect to a reference direction that corresponds to propagation of light specularly reflected by the grating, wherein the first and second angles have different signs, and wherein the encoder head is configured