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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.

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.

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.

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., In this paper the theoretical fundamentals of a high precision interferometric distance measuring system based on dual wavelength heterodyne interferometry will be given. Furthermore first results obtained with a HeNe demonstration set-up will be presented. They show that it is possible to use a dual wavelength heterodyne interferometer for high precision ranging. A view on an advanced system for large distances which is on progress will be discussed.