Patent ID: 8422822

Claim:
A deflectometry method for the optical inspection of a phase and amplitude object placed in an optical path between a single grating and an imaging system, at a distance h of the grating, wherein the grating forms a contrast-based periodic pattern with the spatial frequencies μ 0 , v 0 in, respectively, orthogonal axes x,y in an image plane, and the imaging system comprises an objective and an imaging sensor comprising a plurality of photosensitive elements, wherein this method comprises the step of: capturing through the objective, with the imaging sensor, a first image of said pattern distorted by the phase and amplitude object; and is characterised in that said spatial frequencies μ 0 , v 0 are not higher than the respective Nyquist frequencies of the imaging system on said axes x,y, and this method also comprises the steps of: calculating a Fourier transform of said first image in a spatial frequency domain; selecting at least one first— or higher-order spectrum of said Fourier transform and shifting it in said frequency domain so as to substantially place it at a central frequency of said Fourier transform; and carrying out a reverse Fourier transform of said at least one shifted first- or higher-order spectrum of said Fourier transform so as to obtain a complex function g(x,y)=I(x,y)e iφ(x,y) , wherein I(x,y) is an intensity and φ(x,y) a phase linked to optical deflection angles θ x , θ y in, respectively, the directions of the x and y axes, according to the following formula: φ(x,y)=−2πh(μ 0 tan θ x +V 0 tan θy).