Patent ID: 9134144
Filing Date: 2015-09-15
Classification: G01D

Abstract:
1. A displacement detecting device comprising: a scale which has an optical lattice; a detecting unit which is disposed so as to be movable in a scanning direction relative to the scale and which has n (n is an integer not smaller than 3) detection portions, inclusive of at least a first detection portion, a second detection portion and a third detection portion, arranged in the scanning direction for detecting position information from the optical lattice; and a calculating portion configured to obtain a self-calibration curve on graduations of the scale by specifying positions of the detection portions and calculating measurement error based on the position information detected by the detecting unit, wherein: the detecting unit is provided so that a distance between the first detection portion and the second detection portion and a distance between the second detection portion and the third detection portion are different from each other and do not form an integral multiple; and the calculating portion obtains the self-calibration curve on the graduations of the scale by repeating operation of moving the detecting unit in the scanning direction until position information detected by one of the first to third detection portions is detected by another detection portion, and calculating measurement error based on the detected position information and a distance between the detection portions which have detected the position information, wherein the scale has a rectangular shape, the optical lattice comprising bright portions and dark portions, boundary lines between the bright portions and the dark portions being parallel to each other.