Mechanical designs often include specifications for surface quality such as roughness or ripple. Inspecting workpiece surfaces as they are manufactured is critical to proper quality control and to avoid premature part failure. White light interferometers can acquire surface parameters in seconds. These 3-D profiles require a much longer time if acquired using traditional tactile processes such as stylus profilometers. Furthermore, white light interferometers can quickly determine figures of merit such as percentage contact area or frequency distribution. Roughness can be optically determined, but the values can deviate from the results of tactile measurements to which the dimensions of the drawing and standards generally refer. New guidelines for calibrating white light interferometers give you the assurance that the measured values can be traced back to calibration standards. Optical measurements also make qualitative roughness parameters available that can help determine whether a surface is too rough leading to high frictional losses or too smooth leading to excessive adhesion.