| Zugriffsnummer | 12593 |
| Dokumenttyp | Konferenzartikel |
| Sprache | Englisch |
| Titel | Multiwavelength diode laser interferometry for measurements of surface topography [Poster] |
| Autor(in); Institution |
Wolf, Michael; 5.23, Längenmessmaschinen und -messmittel, PTB-Braunschweig
Abou-Zeid, Ahmed; 5.23, Längenmessmaschinen und -messmittel, PTB-Braunschweig
Löbau, Jörg; 5.23, Längenmessmaschinen und -messmittel, PTB-Braunschweig
|
| Quelle/Jahr | X. International Colloquium on Surfaces = X. Internationales Oberflächenkolloquium:(2000), Proceedings + Poster, 465 - 469 |
| Herausgeber(in) |
Dietzsch, M.
Trumpold, H.
|
| ISBN | 3-8265-6999-7 |
| Verlag | Aachen: Shaker |
| Konferenzangaben | X. International Colloquium on Surfaces, Chemnitz, 31, January - 2, February, 2000, Germany |
| Freie Schlagworte | profilometry ; interferometry ; diode lasers |
| Zusammenfassung | Interferometry used for surface profilometry is known to be a technique ensuring high accuracy, however, it also requires a great effort. Another important problem of interferometric methods is their ambiguousness if distance variations of more than half the wavelength of the light used, λ1, have to be covered. An approach taken to solve the problems connected with interferometry is the use of diode lasers which allow the experimental set-up to be simplified and, therefore, the costs of a scanning surface profilometer to be reduced. The specific feature of a laser diode is its tunability by current variation. Exploiting this property, a RF modulation of the diode current causes a frequency modulation of the emitted radiation. Using lock-in amplifiers to detect the second and third harmonic of the modula-tion frequency, quadrature signals can be obtained from the interferometer with only one photo detector. For the profilometer a modulation frequency of 1 MHz is used, allowing scanning speeds of up to 100 kHz. To extend the accessible measurement range and make the interferometric information unequivo-cal even for distance variations exceeding λ1/2 a second diode laser emitting a different wavelength λS is used. The resulting synthetic wavelength λS = λ1*λ2/(λ1-λ2) allows a direct calculation of the surface topography, including tilted or spherical surfaces. No counting phase unwrapping process is necessary. The performance of the profilometer developed is demonstrated on the grooved glass surface of a tilted depth setting standard. The results agree quite well with the reference val-ues stated by the PTB. |
