Patent ID: 6018990
Filing Date: 2000-02-01
Classification: G01B

Abstract:
A flatness measuring and analyzing method in which, of predetermined three sheets of plates, different pairs of two sheets are successively selected three times, thus selected each pair of plates are disposed so as to oppose each other with a predetermined gap therebetween upon each selecting operation, a difference between those opposed surfaces to be measured is two-dimensionally measured, and a form of the surface to be measured of each of the plates is determined by operating results of the three sets of measurement, said method comprising the steps of:measuring the difference between a pair of surfaces to be measured at a first position where, with respect to one plate, the other plate is set at a predetermined rotational position and at a second position where the two plates are rotated from each other by 90.degree. from the first position;subsequently preparing a relational expression correlating results of measurement of the difference between the opposed surfaces at the first and second positions with predetermined symmetry power series polynomials approximating a form of the surface of the plate to be measured;then determining the form of the surface to be measured in each of the plates by operating the relational expressions prepared for the respective surfaces to be measured in each of the pairs with each other;wherein said symmetry power series polynomials include a rotationally symmetrical term and a nonrotationally symmetrical term; and wherein, included as said nonrotationally symmetrical term is a term in which, when a coordinate axis is rotated by 90 degrees, only a sign of a coefficient is reversed with respect to the expression before rotation; andwherein said symmetry power series polynomials include a rotationally symmetrical term and a nonrotationally symmetrical term; and wherein, included as said nonrotationally symmetrical term is a term in which, when a coordinate axis is rotated by 90 degrees, of two nonrotationally symmetrical terms which form a pair, the expression before rotation of one term and the expression after rotation of the other term exchange coefficients thereof or reverse signs of coefficients thereof.