Patent ID: 6521885
Filing Date: 2003-02-18
Classification: G01D

Abstract:
A linear scale measuring device comprising:a scale; a linear encoder disposed relative to said scale; and operation means for calculating a detection phase of said linear encoder by &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;}, wherein said linear encoder includes a two sensors with regard to said scale, the sensors being collinearly arranged such that an array of the sensors is inclined at a predetermined angle with respect to the longitudinal direction of said scale, 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 by the predetermined angle &thgr;is L.