The measurement of surface finish has been recognized as an important element of Computer Integrated Manufacturing (CIM) systems which perform on-line machining systems control. Optical methods for the in-process measurement of surface roughness have been developed for this purpose, but these systems have in many cases introduced excessive complexity in the CIM system. This work presents an area-based surface characterization technique which applies the basic light scattering principles used in other optical measurement systems. These principles are applied in a novel fashion which is especially suitable for in-process measurement and control. A prototype of the optical system to implement these principles is developed in this work. The experimental results are presented to demonstrate the capabilities and future potential for integrating the measurement system into a machining process to achieve significant improvement of quality and productivity.