Patent ID: 8546744
Filing Date: 2013-10-01
Classification: G01D

Abstract:
1. A rotary encoder comprising: a disc-shaped disk disposed rotatably about a rotation axis and having a first ring-shaped track in which a first optical rotating grating is formed and a second ring-shaped track in which a second optical rotating grating is formed; and at least one optical fixed grating disposed fixedly so as to face the disk so that the fixed grating and the first and second optical rotating gratings construct a diffraction interference optical system, wherein each of a plurality of slits included in the first rotating grating in the first track is formed along a curved line obtained by making each of a plurality of radial lines using the rotation axis as a center curved in the circumferential direction at a predetermined curve degree so that a pitch of the slits is set to a predetermined value, and wherein the first track is radially spaced apart from the second track such that a gap is provided between the first track and the second track.