Surface characterization of a diamond turned XY sinusoidal grating

Surface characterization of an XY sinusoidal grating, which is fabricated by FTS (fast tool servo) on a diamond turning machine, is presented. The grating has a three dimensional micro-structured surface, which is a superposition of sinusoidal waves in the X- and Y-direction. The pitches and amplitudes of the sine waves are 10 μm and 0.4 μm, respectively. The surface form of the grating is imaged by a confocal microscope, a white light interference microscope and an atomic force microscope. The 3D images from the microscopes are compared with each other to distinguish the measurement uncertainties. The microscope images are analyzed by the two-dimensional discrete Fourier transform technique, which perfectly matches the nature of sinusoidal waves. The spatial spectrum of the grating surface is employed to identify the specific error factors introduced in the diamond turning process.