Browsing by Author "Kreuz, Silke"
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Item Open Access Double heterodyne interferometer using a multimode laser diode(1994) Han, Sen; Dalhoff, Ernst; Fischer, Edgar; Kreuz, Silke; Tiziani, Hans J.A double heterodyne interferometer using a multimode laser diode with a synthetic wavelength of ~1 mm has been established and the stability of the synthetic wavelength has been investigated.Item Open Access Double heterodyne interferometry for high precision distance measurements(1993) Dalhoff, Ernst; Fischer, Edgar; Kreuz, Silke; Tiziani, Hans J.We present a double-heterodyne interferometer for absolute distance measurements at rough surfaces up to 100 metres. The two wavelengths are generated by frequency shifting the light of a monomode laser diode using a 500 MHz acoustooptic modulator. The synthetic wavelength obtained is λ = 60 cm. In order to yield unambiguity up to 100 meter distance two measurements have to be taken using slightly different frequency shifts of 500 resp. 501.5 MHz. Measurements showing a resolution of 0.1 mm are presented.Item Open Access Interferometry for high resolution absolute distance measuring by larger distances(1993) Dalhoff, Ernst; Fischer, Edgar; Kreuz, Silke; Tiziani, Hans J.Among the incoherent techniques the phase measurement of modulated light seem to have reached some limitation with an resolution of less than 1 mm. This limitation is set by the bandwidth of the photodetector. The coherent techniques operate with two wavelengths to extend the unambiguity range of the classical interferometry. The unambiguity range is then half the synthetic wavelength and can be adjusted quite arbitrarily from some ten micrometers on. Among the incoherent techniques the phase measurement of modulated light seem to have reached some limitation with an resolution of less than 1 mm. This limitation is set by the bandwidth of the photodetector. The coherent techniques operate with two wavelengths to extend the unambiguity range of the classical interferometry. The unambiguity range is then half the synthetic wavelength and can be adjusted quite arbitrarily from some ten micrometers on.Item Open Access Two wavelength heterodyne absolute ranging technique using suppressed carrier modulation(1993) Fischer, Edgar; Dalhoff, Ernst; Ittner, Thomas; Kreuz, Silke; Tiziani, Hans J.For interferometric distance measurements on rough surfaces multiple wavelength interferometry is a powerful tool. It allows to reduce the sensitivity and to extend the range of unambiguity for interferometric measurement. A new kind of a double wavelength heterodyne interferometer is presented which uses only one laser source which generates two wavelengths λ 1 and λ 2 simultaneously. The two different heterodyne frequency shifts of the double heterodyne interferometer (DHI) are achieved by combining an acousto-optical modulator (driven in suppressed carrier mode) with a fixed diffraction grating. In a first prototype a multi-wavelength HeNe laser was used as light source. The synthetic wavelength λ in this system is 55.5 μm and the resolution about 0.15 μm. Measurement results obtained with the setup described are presented.