Patent ID: 6262802
Filing Date: 2001-07-17
Classification: G01B,G01D

Abstract:
A sensing apparatus for sensing position of a moving object, comprising:a scale comprising an angular grid, wherein the grid is formed on or in a surface of a scale substrate, wherein the substrate includes a planar surface and a freely curved surface, and wherein a slope of the angular grid varies in two different directions (x and y directions) in a form of a known function; andat least one two-dimensional angle sensor confronting the surface of said scale having the grid, the sensor being capable of sensing angles along each of the x and y directions;one of said scale and said angle sensor being attachable to a moving object and a position of the moving object in two-dimensional coordinates being detectable by relative movement between said scale and said angle sensor;wherein an angular variation of said angular grid is implemented in a form obtained by superimposing a plurality of sine waves having different frequencies.