Browsing by Author "Fischer, Edgar"

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Open Access
Doppelheterodyn-Interferometrie für hochgenaue Vermessung im Nahbereich
(1992) Fischer, Edgar; Dalhoff, Ernst; Ittner, Thomas; Sodnik, Zoran; Tiziani, Hans J.
In diesem Aufsatz wurde ein Meßsystem vorgestellt, welches sich aus der Kombination der Zweiwellenlängen-Interferometrie mit dem intensitätsunabhängigen Heterodyn-Verfahren zusammensetzt. Die resultierende Doppelheterodyn-Interferometrie vereinigt die Vorteile der beiden Verfahren. Ein großer Eindeutigkeitsbereich entsprechend der effektiven Wellenlänge A entsteht, darüberhinaus sind optisch rauhe Oberflächen als Meßobjekte zulässig; reduzierte Empfindlichkeit gegenüber Vibrationen und Umwelteinflüssen, hohe Auflösung infolge elektronischer Phasenbestimmung sowie hochgenaue Abstandsmessung in Echtzeit sind weitere Vorteile. Das Doppelheterodyn-Interferometer wird in Zukunft zu einem effektiven und dynamischen Meßinstrument zur hochgenauen Entfernungsmessung im Mikrometerbereich bis hin zu Meßdistanzen von 100 m entwickelt werden, für das sich schon jetzt zahlreiche Einsatzmöglichkeiten abzeichnen.
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.
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.
Open Access
Dual wavelength heterodyne interferometry for rough surface measurements
(1990) Fischer, Edgar; Sodnik, Zoran; Ittner, Thomas; Tiziani, Hans J.
For interferometric topography measurements of optically rough surfaces dual wavelength heterodyne Interferometry (DWHI) is a powerful tool. A DWHI system based on a two-wavelength HeNe laser and a matched grating technique is described. This set-up improves system stability and simple heterodyne frequency generation.
Open Access
Dual wavelength heterodyne interferometry using a matched grating set-up
(1992) Fischer, Edgar; Ittner, Thomas; Dalhoff, Ernst; Sodnik, Zoran; Tiziani, Hans J.
Two-wavelength double heterodyne interferometry is applied for topographic measurements on rough target surfaces. A two-wavelength HeNe laser and a matched grating technique are used to improve system stability and to simplify heterodyne frequency generation. Results obtained with an experimental set-up will be presented. The results obtained show that a dual wavelength heterodyne interferometer is appropriate for high precision ranging. Progressing developments for large distances will be discussed.
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, Stefano
The 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-up
Open Access
Heterodynverfahren für hochgenaue Vermessung im Nahbereich
(1992) Fischer, Edgar; Ittner, Thomas; Sodnik, Zoran; Tiziani, Hans J.
Es werden die theoretischen Grundlagen für ein hochgenaues interferometrisches Distanzmeßverfahren, welches auf der Zweilängen-lnterferometrie und der Heterodyn-Technik beruht, dargestellt. Des weiteren werden erste Ergebnisse mit einem Demonstrationsmodell präsentiert, die mit einem Helium-Neon-Lasersystem erzielt wurden und dem prinzipiellen Nachweis der Tauglichkeit des Verfahrens für hochgenaue Abstandsmessungen an technischen Objekten dienten. Es wird ein Ausblick. auf die Realisierung eines fortgeschrittenen Systems zur Messung bei großer Meßdistanz gegeben.
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.
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.
Open Access
Two-wavelength double heterodyne interferometry using a matched grating technique
(1991) Sodnik, Zoran; Fischer, Edgar; Ittner, Thomas; Tiziani, Hans J.
Two-wavelength double heterodyne interferometry is applied for topographic measurements on optically rough target surfaces. A two-wavelength He-Ne laser and a matched grating technique are used to improve system stability and to simplify heterodyne frequency generation.