Obtaining 2D surface characteristics from specular surfaces

Today's surface appearance measures often ignore the inherent two-dimensionality. This paper proposes a method to acquire and assess the appearance of larger specular surfaces in 2D. First, we describe a deflectometric setup to obtain a gradient field of the surface microstructure. Hence, we propose an areal measure based on the angular power spectrum, as defined in ISO 25178, to characterize the waviness of coated surfaces in relevant scales. To verify the validity of this measure, we compare it with an 1D industry standard appearance measurement system (wave-scan). While our method shows the same characteristics when mapped to the wave-scan values, we observed differences between both systems. These are mainly caused by the different measurement principles and the resulting information of the surface.