Abstract: A system for measuring (200) a sample (2) by deflectometry comprising: a source (10) for generating a light beam in a source plane (105); an illumination module (19) for forming an illumination beam (9) comprising: a first converging optical element (18); a first selection optical element (16) with a first aperture (160); reflective matrix optical modulation means (30) to form a pattern (7), said first aperture (160) being configured to control the angles of said illumination beam (9) on said reflective matrix optical modulation means (30); a Schlieren lens (20) for obtaining an angle-intensity encoding of said pattern (7) on the sample (2); imaging (40) and detecting means (50) for detecting an image of said sample (2).