Patent ID: 6473714
Filing Date: 2002-10-29
Classification: G01C

Abstract:
A position measuring apparatus, comprising:a pattern arranged so as to indicate two-dimensional position; a first optical system for splitting a light beam traveling from the pattern into two beams directed in two directions; a first condensing element for condensing the light beam from the first optical system in a first direction; a second condensing element for condensing the light beam from the first optical system in a second direction different from the first direction; a first light receiving element for receiving the pattern image condensed by the first condensing clement; a second light receiving element for receiving the pattern image condensed by the second condensing element; and calculating means for calculating a position on the pattern based on light receiving signals of the first condensing element and the second condensing element; wherein the pattern is composed of a two-dimensional pattern arrayed at a regular interval in the longitudinal directions of the respective first condensing element and second condensing element, the two-dimensional pattern arrayed in each of the longitudinal directions being arranged to have the same width as viewed from the direction perpendicular to the longitudinal direction; and wherein the pattern is formed of at least a first pattern modulated with a first period and a second pattern modulated with a second period different from the first period in terms of each of the first and second directions, and the first pattern and the second pattern are orderly arrayed at a regular interval.