Conference Agenda

TOM10 S02: Frontiers in Optical Metrology: Interferometry
Wednesday, 14/Sept/2022:
4:30pm - 6:00pm

Session Chair: Ralf B. Bergmann, BIAS, Germany
Location: B031

Ground floor, 60 seats

4:30pm - 5:00pm
ID: 305 / TOM10 S02: 1
TOM 10 Frontiers in Optical Metrology

Toward tomography imaging of acoustic fields using digital holography

Pascal Picart, Saoucene Hassad

Le Mans University, France

The characterization and control of waves in acoustics, and more generally in wave physics, is of great interest because resulting technological innovations may impact several domains: environmental and energy transition, health sector, and industrial sector in the broadest sense. The characterization requires to develop new approaches to provide qualitative and quantitative insight of the acoustic fields of interest. Generally, imaging acoustic fields is performed by using microphone arrays which have a low spatial resolution. Here, we aim at demonstrating the proof-of-concept of simultaneous full-field and multi-view imaging of acoustic field in the free space using digital color holography and a single monochromatic high-speed sensor. The simultaneous acquisition of the necessary set of data is thus realized "single shot" and then numerical process yields images of both the amplitude and phase of the acoustic field along three different directions of observation. This has for advantage of permitting consistent and rapid data acquisition. We present the first experimental results and the first tomographic reconstruction of an acoustic field propagating in the free-field at 40 k Hz.

5:00pm - 5:15pm
ID: 183 / TOM10 S02: 2
TOM 10 Frontiers in Optical Metrology

Investigation of dynamic influences in tilted-wave interferometry

Gregor Scholz, Michael Schulz, Ines Fortmeier

Physikalisch-Technische Bundesanstalt (PTB), Germany

Aspherical and freeform lenses allow for compact optical systems and have therefore gained high interest in optics. The interferometric measurement of these forms is a challenge, for which the tilted-wave interferometer (TWI) has been developed. To evaluate the measurement uncertainty of the TWI, both the static and the dynamic influence parameters have to be investigated. In this work, we focus on the dynamic influences on the measurement data of the interferometer. To this end, the individual influences as well as their point of insertion into the process chain are identified. Then the measurement of the interferogram data is modelled as a Monte Carlo simulation. The propagation of different influences through the data process chain to the optical path length differences (OPDs) is also simulated, and the resulting variation of the OPDs is estimated. Furthermore, the variation of the OPDs resulting from measured interferogram data is investigated for comparison. The analysis and quantification of variation of the OPDs along with its contributing influence sources are important steps on the way towards a full uncertainty estimation of optical form measurement with the TWI.

5:15pm - 5:30pm
ID: 290 / TOM10 S02: 3
TOM 10 Frontiers in Optical Metrology

Quasi-analytical and rigorous modeling of interference microscopy

Tobias Pahl, Johannes Breidenbach, Peter Lehmann

University of Kassel, Germany

We present an extended vectorial Kirchhoff model of coherence scanning interferometry including several vector rotations occurring in the imagining and scattering process as well as polarization dependent reflection coefficients. For validation simulated results are compared to those of the conventional scalar Kirchhoff model and a rigorous finite element modeling.

5:30pm - 5:45pm
ID: 289 / TOM10 S02: 4
TOM 10 Frontiers in Optical Metrology

Low divergence structured beam In view of precise long-range alignment

Miroslav Sulc1,2, Jean-Christophe Gayde3

1Technical University of Liberec, Czech Republic; 2Institute of Plasma Physics of the Czech Academy of Sciences, Czech Republic; 3CERN, Switzerland

A new method of generation of a Structured Laser Beam (SLB) with non-diverging central core was proposed and is promising for creating long distance multipoint alignment systems. This beam is generated by a set-up consisting of two convex lenses in Kepler telescope arrangement. The first one is a high refractive index ball lens, second one is a standard lens. The beam, in cross-section consisting of light and dark concentric circles, propagates over a large distance. The central core of the SLB has a very small divergence which can be tuned. A divergence of 10 μrad was proven experimentally. In this experiment, the small initial beam core diameter of 10 μm, and its diameter of 1.5 mm at a distance of 150 m, show its ability for use as a multipoint fiducial reference line. This small beam divergence seemingly lies beyond the diffraction limit for laser beams.

5:45pm - 6:00pm
ID: 393 / TOM10 S02: 5
TOM 10 Frontiers in Optical Metrology

Holographic single-image depth reconstruction

Simon Hartlieb, Christian Schober, Tobias Haist, Stephan Reichelt

Institut für Technische Optik, Universität Stuttgart, Germany

In this article a camera-based single-image sensor is presented, that is able to measure the distance of multiple object points. The experimental results show an accuracy of 8,51 µm within a depth range of 20 mm. The sensor consists of a camera, whose lens is upgraded with a diffractive optical element (DOE). It fulfils two tasks: adding a vortex point spread function (PSF) and replication of the vortex PSFs to a predefined pattern of K spots. Both, shape and rotation of the vortex PSF is sensitive to defocus. By applying the depth reconstruction to each of the K replications and averaging the results, we experimentally show, that the reconstruction of the depth signal can be improved by a factor of up to 3.