Times for this live event are all Central European Summer Time, CEST (UTC+2:00 hours)


8:30 to 8:35
Introduction
Peter Lehmann, Univ. Kassel (Germany)


8:35 to 8:50

This event occurred in the past.

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Tomography imaging based on three-color digital holography



Saoucene Hassad, Lab. d'Acoustique de l'Univ. du Maine, CNRS (France)

Data acquisition and processing is a critical issue for high-speed applications especially for three-dimensional imaging and analysis. Digital holographic tomography is a potential approach that can quantitatively measure the three-dimensional distribution of the refractive index of any phase object or transparent specimen. Generally, tomography is operated by acquiring projections of the sample and numerically mapping those projections onto a 3D representation using an inverse problem, such as the filtered back projection algorithm. From the practical point of view, there are mainly two ways for recording the data. First, the set of data can be acquired when varying the illumination angle. Last, the data can be acquired by the sample rotation. In both approaches, the sample and the optical set-up must be highly stationary whereas the illumination beam or the object is rotated. Another option is to simultaneously acquire the necessary set of data with a single shot acquisition and then to process them. This would have for advantage of permitting 3D imaging of non-stationary targets or transient time-varying object. The use of multiple camera sensors is complicated and not cost efficient. So, this paper presents the proof of concept for a novel approach based on three color digital holography and the use of a single monochromatic sensor. The principle is based on off-axis holography and spatial multiplexing of multi-wavelength holograms. Three wavelengths from three different laser lines are used to illuminate the target at different incidence angles. The reference beams from the lasers are combined into a single three color beam and the spatial frequencies of the reference waves are adjusted so as to allow for the spatial multiplexing of digital holograms with the monochromatic sensor. After de-multiplexing and processing the color holograms, the amplitude and phase of the target along the views are obtained. Further processing in order to compensate for aberrations of the set-up are proposed and discussed. As proof of concept, we provide results for 3D shape of a 3D ball reconstructed using the inverse Radon transform. These first results are adequate to be exploited in the study of the acoustic field of an ultrasound transducer, for a frequency of 40Khz.

Biography: Saoucène HASSAD is PhD student in the Acoustics Laboratory at Le Mans University, France. She received her Master degree in Optics and Applied Photonics from the University of Sétif 1, Algeria, in 2015. S. HASSAD joined Le Mans University in 2018 as part of her PhD thesis preparation with co-supervision from Prof. Bouamama (Sétif) and Prof. Picart (Le Mans). Her research interests are related to the development of digital holographic methods and tomography imaging for the investigation of acoustic phenomena.


8:55 to 9:00
Introduction
Ettore Stella, CNR-Istituto dei Sistemi e Tecnologie Industriali Intelligenti per il Manufatturiero Avanzato (Italy)


9:00 to 9:30

This event occurred in the past.

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Recent progresses of near-eye display for AR and VR



Byoungho Lee, Seoul National University (Korea, Republic of)

Near-eye displays (NEDs) for augmented and virtual reality (AR/VR) are spotlighted because they have a possibility to provide much more immersive experiences never possible before. With the virtue of recent progress in sensors, optics, and computer science, several commercial products are already available, and the consumer market is expanding rapidly. However, there are several challenging issues for AR and VR NEDs to become closer to our lives. Here, we will explore these issues and important topics for AR and VR, and introduce some of the ideas to overcome them: diffractive optical elements (DOEs), retinal projection displays, and 3D display with focus cues. First, unlike VR with a simple optical system, AR that needs to merge an artificial image with an outer scene requires additional optics. The diffractive elements have the merit of being thin and transparent, suitable for the image combiner. Among them, holographic optical elements (HOEs) have great potential as they can record the desired volume grating from the simple lens to the complex wavefront using light interference. Second, in order to wear the NEDs for a long time, it must deal with the visual fatigue as well as the form factor. Retinal projection display can effectively prevent the vergence-accommodation conflict problem even with a simple optical design. In the retinal projection display, the light rays from the display are adjusted to converge into a small point using a lens. It ensures a wide depth range in which the images are clearly visible. Furthermore, it is possible to provide observers with accurate focus cues for the alleviation of visual fatigue via multi-layer displays and holographic displays. Recently, we conceived tomographic NED that can reproduce dense focal planes. We confirm that this system provides quasi-continuous focus cues, semi-original contrast, and considerable depth of field. The experimental results of our prototypes are explained. We also explain the recent activities of using deep learning in holographic NED system.

Biography: Dr. Byoungho Lee is a professor at Seoul National University (SNU), Korea. He received his Ph.D. degree in EECS from University of California at Berkeley in 1993. Since September 1994, he has been with SNU as a faculty member. Prof. Lee is a Fellow of SPIE, OSA, IEEE, and SID. He is a Senior Member of the National Academy of Engineering of Korea and a Member of the Korean Academy of Science and Technology. He is currently serving as a Director of SPIE and also the President of the Korean Information Display Society. He has served as the 2019 President of the Optical Society of Korea. Prof. Lee’s research fields are AR/VR/3D display and metasurface devices. He received many awards including the Jin-Bo-Jang National Science Badge of Korea.


9:35 to 9:40
Introduction
Haida Liang, Nottingham Trent Univ. (United Kingdom)
Roger M. Groves, Technische Univ. Delft (Netherlands)


9:40 to 10:10

This event occurred in the past.

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Sensing through the surface of art materials with advanced Raman spectroscopy techniques



Claudia Conti, CNR-ISPC (Italy)

Recent advances on micro Spatially Offset Raman Spectroscopy (micro-SORS), an optical spectroscopy method able to non-invasively investigate at the microscale the molecular composition of the subsurface of turbid materials, will be presented. The recent research topics include the application of micro-SORS to non-invasively reconstruct the diffusion profiles of conservation treatments applied in calcium-based matrices, the first in-situ surveys of prestigious panel paintings with a portable micro-SORS prototype derived modifying a commercial portable Raman spectrometer, and proof-of-concept experiments performed coupling micro-SORS with Time-Gated Raman Spectral Multiplexing method for the non-invasive suppression of the fluorescence originated by the subsurface.

Biography: Dr. Claudia Conti is a senior researcher at the Institute of Heritage Science (ISPC) of the Italian National Research Council (CNR) where she leads the Raman Spectroscopy Laboratory. She established expertise in the area of advanced applications of vibrational spectroscopy to the material analysis, in particular, in Cultural Heritage.

She conducted her research through several scientific visits (2014-2018) to the Rutherford Appleton Laboratory (Oxford, UK) that lead to the successful transformation of macro-SORS conceptually to the area of Cultural Heritage. She has been selected as the 2020 recipient of the “Craver award”, presented by the Coblentz Society at SciX 2020.