LASER REFERENCE PLANE FOR FLATNESS MEASUREMENT OF LARGE-SCALE MACHINED SURFACES

Recently, a practical method has been developed to establish optically a precise reference plane for direct measurement of the flatness of medium and large-scale machined surfaces. In this method, a finely collimated laser beam is swept by a rotating pentaprism in an ideal plane parallel to the surface to be measured. In this paper, the geometrical accuracy of the laser reference plane is theoretically analyzed in terms of geometrical error of the pentaprism as well as the rotational error. Based on the analysis, prototype flatness measurement systems have been developed and the measurement accuracy and feasibility has been compared with those of a conventional method. The experimental results clarified that the present laser reference plane shows superior performance when the size of a surface to be measured is larger than around one meter square.