A simple technique for the quantitative deformation analysis of reflecting surfaces is presented. A plate with a special printed pattern consisting of crossed line gratings and an electronic camera are the only required equipment. The pattern is reflected by the specular surface and imaged by the camera. The mechanical deformation causes a slight distortion of the pattern image that is evaluated using the Fourier-transform method. The technique was tested on a glass mirror with side lengths of 105 and 132 mm, which was deformed by a central load. The sensitivity for out-of-plane displacements is 100 nm.