A Simple Deflectometric Method for Measurement of Quasi-Plane Specular Surfaces

Deflectometric methods have been extensively used, both in research and industry, to measure the shape of specular surfaces. The method presented in this paper makes it possible to evaluate the planarity of quasi-flat surfaces, i.e. to measure angular deviations between the average normal vector of the surface and the actual vector at each point of the surface (vector field errors). The method is based on homographies, a mathematical tool that has been widely tested in computer vision. Furthermore it is simple, computationally efficient and robust. Besides that, the proposed system does not require precise positioning of the measured part. The system requires only a single camera and an LCD screen, so it is a low cost solution. Simulations have been performed to validate the system, having obtained errors on the measured vector field that are in the order of less than 1 mrad, suitable for many applications. This is a work in progress and further experiments need to be carried out and several extensions could be considered.