Patent ID: 6867871

Claim:
In a grating irradiation type moiré fringe measuring and analyzing method in which a moiré grating disposed between a light source and a surface to be inspected is irradiated with light from said light source, so as to project a shadow of said moiré grating onto said surface, and moiré fringes formed by said shadow and said moiré grating are captured by imaging means so as to analyze a shape of said surface; a moiré grating noise eliminating method comprising: a first step of moving said moiré grating within a grating plane formed by grating lines of said moiré grating in y direction orthogonal to said grating lines by increments of a distance L y satisfying the following expression (1) from an initial position in said y direction, while capturing an image of said moiré fringes by using said imaging means with an imaging magnification set such that a pixel pitch W of an image pickup device of said imaging means and a grating pitch p of said moiré grating when forming an image on said image pickup device satisfy the condition of the following expression (2) each of times when said moiré grating is located at said initial position and moved by said distance L y , so as to form M y-direction positional moiré fringe images satisfying the condition of the following expression (3): L y =p /(2 n 1 ) (1) W=p /(2 n 1 n 2 ) (2) M= 2 n 1 n 3 (3) where n 1 , n 2 , and n 3 are natural numbers; a second step of averaging thus obtained M y-direction positional moiré fringe images so as to attain an average moiré fringe image; and a third step of determining shape information of said surface according to thus attained average moiré fringe image.