Patent ID: 6642509
Filing Date: 2003-11-04
Classification: G01D

Abstract:
A linear scale measuring device comprising:a pair of scales; a linear encoder disposed relative to said pair of scales; and an operation unit for detecting the position of said linear encoder relative to said pair of scales based on an output from said linear encoder, wherein said linear encoder includes two sensors with regard to each of said pair of scales, the sensors being previously arranged such that they are inclined at a known angle with respect to the measuring direction of said scales, and wherein said operation unit detects the position of said linear encoder resulting from the inclination of the sensors with regard to the measuring direction of the scales, based on detection signals from the sensors and said known angle which is previously set, by calculating a detection phase of said linear encoder relative to a scale according to &PHgr;O=(&PHgr;A&dgr;+&PHgr;B&dgr;)/2âˆ’2&pgr;/&lgr;Â·L{sin&thgr;+(&PHgr;AOâˆ’&PHgr;BOâˆ’&PHgr;A&dgr;+&PHgr;B&dgr;)/4&pgr;sin&thgr;Â·cos&thgr;}, and wherein the phases detected by said two sensors are &PHgr;A&dgr;, and &PHgr;B&dgr;, respectively, the initial phases of the two sensors are &PHgr;AO, and &PHgr;BO, respectively, said predetermined angle is &thgr;, a wavelength of said scale is &lgr;, and a distance between the rotation center of the sensors and the center point between the two sensors when the sensors are inclined relative to the scale by the predetermined angle &thgr; is L.