Universität Stuttgart
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Item Open Access Dual-wavelength interferometer for surface profile(1990) Manhart, Sigmund; Maurer, R.; Tiziani, Hans J.; Sodnik, Zoran; Fischer, Edgar; Mariani, A.; Bonsignori, R.; Margheri, Giancarlo; Giunti, C.; Zatti, StefanoThe design and first experimental results of a dual-wavelength heterodyne interferometer (DWHI) for precise surface profile measurements are presented. The DWHI is based on a Mach-Zehnder type interferometer with the surface to be measured in the sensing arm of the interferometer. Two adjacent wavelengths are simultaneously used in the interferometer; the range information is gained from the beat frequency of both heterodyne interferometer signals. Thus, the extreme range ambiguity of classical interferometers and their sensitivity to mechanical distortions are reduced by the ratio of laser frequency to beat frequency. The DWHI is expected to have the good SIN performance a of coherent detection system but also the capability of measuring to diffusely scattering targets. The main features of the system presented here are: - use of a single diode laser in combination with a high frequency Bragg cell to generate two adjacent wavelengths - use of an all-fiber concept for the optomechanical build-upItem Open Access The use of optical transfer function for assessing the quality of optical systems(1976) Tiziani, Hans J.The optical transfer function (OTF) has proved to be a highly valuable aid in comparing and evaluating the quality of optical systems. The measuring instrument developed is briefly described. The OTF measurements agreed well with theoretical results obtained from lens data, especially for the modulation transfer function (MTF). With the aid of a model based on experiments, a threshold curve was obtained which enabled the results based on the MTF to be compared with those from conventional resolution tests. To enable workable focusing and quality criteria to be derived, an attempt was made to condense the profuse data resulting from the MTF.