Very large scale phase measuring interferometry for profile measurement of aspheric surfaces with nanometer accuracy

To fulfil metrological requirements of profiling aspheric surfaces, a very-large-scale phase measuring interferometric system is presented that has been developed at Korea Advanced Institute of Science and Technology. The measurement system comprises an interference microscope probe mounted on the z-axis and a precision xy-stage. The probe operates with principles of white light scanning interferometry to sample three-dimensional data in discrete form with a sub-nanometer resolution. A 640x480 pixel array CCD camera is used, thus the area of a single patch is limited within 0.64x0.48 mm with 1.0 /spl mu/m lateral resolution. The stage is controlled in the xy-directions with the aid of three plane mirror type heterodyne laser interferometers with 2.5 nanometer positioning resolution.