השתתפות בסמינר תיתן קרדיט שמיעה = עפ"י רישום שם מלא + מספר ת.ז.  בצ'אט

Join Zoom Meeting
https://us04web.zoom.us/j/79530182251
Meeting ID: 795 3018 2251

Speaker: Tal Mund

M.Sc. student under the supervision of Prof. Alex Bronstein

Wednesday, May 6^th, 2020 at 15:00

        ZOOM  Seminar

EEG Source Localization Using Compressed Measurements and the Fabrication of an Anisotropic Phantom Head Model

Abstract

One of the greatest challenges of modern-day science community is understanding how our brain functions. In a human head, a neural activity is usually modeled as a current dipole activation with a specific position and orientation. Brain imaging techniques such as EEG, MEG, fMRI etc. are used to evaluate the neural activities location, orientation and magnitude. One can study the spatiotemporal behavior of the head’s neural circuits using these techniques. However, for us to better understand how our brain works, we need to collect a vast amount of data. One of the main advantages of EEG is its portability, since competing imaging techniques such as fMRI and MEG are stationary. A mobile EEG device can continually collect data from research subjects as they perform their everyday tasks. By compressing the EEG measurements, the hardware requirement of a portable EEG device is reduced, which in turn makes it cheaper and lighter. Hence getting closer to a portable EEG device. In this work, the possibility of using a compressed set of EEG measurements was simulated and analyzed. In addition, a phantom mimicking the electromagnetic properties of the human head is presented. A phantom head is considered an essential validation step between computer simulations and the data processing of EEG recordings on humans. The fabrication is based on 3d-printing technology combined with an electrically conductive gel. The novel key features of the phantom are the controllable anisotropic electrical conductivity of the skull and the densely packed monopolar current sources permitting interpolation of the measured gain function to any dipolar current source position and orientation within the head.

סמינר זה יחשב כסמינר שמיעה לתלמידי תואר שני, למי שמתחבר לסמינר דרך הזום.

You are invited to attend a lecture On Thursday, 30 April 2020, 15:00

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https://us04web.zoom.us/j/73978006567

HIGH POWER DYNAMIC STRUCTURED LIGHT 3D RECONSTRUCTION SYSTEM BASED ON RESONANCE DOMAIN DIFFRACTIVE OPTICS

By:

Omer Stein

M.Sc student under  the supervision of Prof. Michael Golub,

Prof. Menachem Nathan, Prof. Shlomo Ruschin

Abstract

Structured light is one of the most common 3D data acquisition technique used in industry. Traditionally, structured light methods are used to obtain 3D information of an object, using predetermined illumination patterns to encode spatial data for later triangulation and reconstruction. A multitude of pattern types exist, which achieve varying degrees of depth resolution, depending on the needs of the user and the demand on the system. Means of projecting these patterns vary as well, including off the shelf DLP projectors, scanning mirror laser projectors and diffractive optics based laser projectors. Diffractive optics based projectors are one of the most cost effective and power efficient options, but are limited in projection angles. Traditional DLP or scanning mirror projectors can have high angles of projection, but can be very large and power consuming, lack illumination power, or present an eye safety hazard. In this work, we show the feasibility of a gray coded structured light 3D reconstruction system, based on resonance domain diffractive optical elements previously developed by our group, which allow for wide fanout angles with very high diffraction efficiency and close to diffraction-limited fidelity of the projected intensity patterns, leading to a compact, low cost, high preforming 3D reconstruction system. We present the design, characteristics, simulation and experimental results of our proposed setup, using real world objects, and compare our results with comparable commercially available projectors.

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PhD "ZOOM" SEMINAR
Wednesday, June 24, 2020 at 14:00
Microknot optical resonators and their applications
Alexandra Blank
PhD of Dr. Yoav Linzon
Resonating microstructures defined locally on optical fiber tapers are an attractive venue for researchers in the recent years. These engineered microstructures find use in various applications, including photonic filters, lasers, optomechanical light-matter interaction devices, and various sensing elements mimicking human smell and taste sensing system (gas and liquids sensors), known as electronic noses and electronic tongues.
The presented work is devoted to experimental and numerical investigations of the behaviour of microknot resonators (MKRs) defined locally on optical fiber tapers as a promising platform for gas and liquid sensing applications. We demonstrate the two-probe localized heating technique for MKR fusing intended for improving its optical performance and mechanical stability in size and circular profile. We show that an above-threefold dynamical range enhancement has been consistently achieved. The fused MKRs are found to maintain phase stability, as opposed to the unfused knots exhibiting a random phase drift. We prove that e-fusing improves the mechanical strength in the MKR, providing it with transferability that is of importance in sensing applications.
We investigate fused MKRs’ characteristics for in-liquid sensing both local, where the analyte is delivered to the packaged device and the remote sensing. We have suggested and demonstrated two deployment schemes, namely, folded configuration intended for remote sensing, and straight configuration on either hydrophilic or hydrophobic substrate intended for packaged integration of photonic sensors. We found that in folded configuration reversibility remained sustainable over approximately 50 cycles of operation, whereas in most cases of the straight configuration on glass substrate transmission drops to the noise level after a few dewetting cycles. We show that a hydrophobic PDMS substrate can be advantageous relating to surface chemistry as compared to a typical hydrophilic glass substrate. For all those configurations we demonstrated their persistent sensing capabilities and defined unique recognition plots in principle components space specific to pure and diluted volatile liquids tested.
We demonstrate a durable and simple humidity sensing approach based on index-sensitive interference spectroscopy of surface stress birefringence and incorporating tapered microfibers on a silicon substrate coated with an active polymer layer. We show theoretically that the transmission spectrum of coated tapers possess interference patterns induced by the stress applied to the taper due to the coating weight load. The coated device demonstrated persistent detection capability in humid environment and a linear response to calibrated analytes. For each volatile organic analyte tested we defined a calibration plot in principal component space.
Microstructured tapers, when untreated, amenable to low performance in terms of resonance depth (dynamical range), Q and mechanical fragility. In this work we performed a novel comprehensive numerical study of the photonic transmission in manually prepared microknot resonators with different contact coupling area geometries and refractive index variations. Using selective modifications of the MKR coupling area and index profile, the transmission characteristics were studied, and a recipe for the experimental realization of high quality-factor resonators is prescribed.
We present results of the numerical study of the photonic transmission in 3D resonating microstructures defined on optical tapered fibers as functions of both radius and doping and deduce their sensitivities to localized refractive index variations in terms of resonance shifts. Based on the analysis of the transmission characteristics of polymer-coated microstructures, we demonstrated a linear response to the refractive index gradient in NIR wavelength range.
We envision that simple and robust devices with improved optical and mechanical characteristics will be harbored in next generation sensors, as well as optomechanical applications incorporating microfiber-based resonating structures.
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https://zoom.us/j/4962025174
The meeting will be recorded and made available on the School’s site.