Heterodyne interferometer microscopy for high precision surface measurement

Dennis Leitz; Maxim Scomarohov; Christian Rembe

doi:10.1117/12.2633313

3 October 2022 Heterodyne interferometer microscopy for high precision surface measurement

Dennis Leitz, Maxim Scomarohov, Christian Rembe

Proceedings Volume 12223, Interferometry XXI; 1222302 (2022) https://doi.org/10.1117/12.2633313
Event: SPIE Optical Engineering + Applications, 2022, San Diego, California, United States

Abstract

Laser Doppler vibrometer (LDV) is typically used to detect and measure vibrations and dynamics of mechanical structures in a non- contacting and non-destructive way. Eckermann et al. proposed 1993 in a patent a technique to apply LDV to surface topography measurements. In this paper we explore the application of the technique to surface-topography analysis, providing the potential of axial resolution in the picometer regime for lateral resolutions defined by a confocal microscope. By moving the sample with high speed perpendicularly through the focused beam of the LDV, the topography of the surface will change the optical pathlength between LDV and specimen which the LDV measures with broad bandwidth. The advantage of this approach is that mechanical vibrations of the specimen and the stage can be filtered as they appear in a much lower frequency range as the topography information of the specimen. For the preliminary setup, we used a commercially available LDV (Polytec OVF-303s) focused on the sample with a 50x microscope objective. The sample is a chrome-covered Siemens Star Target with a step height of 140.8 nm. The high relative speed of the topography with up to 2.5 m/s is realized by rotating the sample using a speed-controlled servo motor. With this preliminary setup, we achieved a focus diameter of 1.4 µm and an axial resolution of 1.53 nm in the full bandwidth of 250 kHz.

Citation Download Citation

Dennis Leitz, Maxim Scomarohov, and Christian Rembe "Heterodyne interferometer microscopy for high precision surface measurement", Proc. SPIE 12223, Interferometry XXI, 1222302 (3 October 2022); https://doi.org/10.1117/12.2633313

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