Patent Document ID: 9891042
Application ID: 14907009
Patent Status: 1

Claim One:
1. A method for measuring a deformation of a surface of an object on which a two-dimensional grid is provided on the basis of a two-dimensional grid image of the surface of the object taken by a camera, comprising: taking the two-dimensional grid on the surface of the object with the camera to obtain the two-dimensional grid image in such a state that the directions of camera pixels are adjusted to the two-dimensional grid image of the surface of the object, and at the same time one period of said two-dimensional grid image in an x direction is adjusted to Nx pixels of the camera and one period in a y direction is adjusted to Ny pixels of the camera, where Nx and Ny are integers greater than 2 and smaller than the number of pixels in the x and y directions on an imaging surface of the camera; cutting out a pixel region of Nx×Ny which corresponds in the x direction and the y direction from the two-dimensional grid image; carrying out a two dimensional Fourier transformation to the cut out pixel region, and sampling a set of components (1, 0) and (0, 1) or (−1, 0) and (0, −1) of the frequencies in the Fourier transform plane; finding the phases of either set of the frequencies in each pixel of the two-dimensional grid image for the frequencies in the x direction and the y direction that correspond to one period of said grid in said image of the two-dimensional grid image; and after the surface of the object is deformed, the finding the phases on the two-dimensional grid image taken by the camera, is carried out on each pixel of the image to obtain the deformation of the object on the basis of the phases of each pixel before and after the deformation of the surface of the object.