Eugenio Pugliese

Imaging live humans through smoke and flames using far-infrared digital holography

The ability to see behind flames is a key challenge for the industrial field and particularly for the safety field. Development of new technologies to detect live people through smoke and flames in fire scenes is an extremely desirable goal since it can save human lives. The latest technologies, including equipment adopted by fire departments, use infrared bolometers for infrared digital cameras that allow users to see through smoke. However, such detectors are blinded by flame-emitted radiation. Here we show a completely different approach that makes use of lensless digital holography technology in the infrared range for successful imaging through smoke and flames. Notably, we demonstrate that digital holography with a cw laser allows the recording of dynamic human-size targets. In this work, easy detection of live, moving people is achieved through both smoke and flames, thus demonstrating the capability of digital holography at 10.6 μm.

Complex dynamics of a dc glow discharge tube: Experimental modeling and stability diagrams

We report a detailed experimental study of the complex behavior of a dc low-pressure plasma discharge tube of the type commonly used in commercial illuminated signs, in a microfluidic chip recently proposed for visible analog computing, and other practical devices. Our experiments reveal a clear quasiperiodicity route to chaos, the two competing frequencies being the relaxation frequency and the plasma eigenfrequency. Based on an experimental volt-ampere characterization of the discharge, we propose a macroscopic model of the current flowing in the plasma. The model, governed by four autonomous ordinary differential equations, is used to compute stability diagrams for periodic oscillations of arbitrary period in the control parameter space of the discharge. Such diagrams show self-pulsations to emerge remarkably organized into intricate mosaics of stability phases with extended regions of multistability (overlap). Specific mosaics are predicted for the four dynamical variables of the discharge. Their experimental observation is an open challenge.

Optimal Phase-Control Strategy for Damped-Driven Duffing Oscillators.

Phase-control techniques of chaos aim to extract periodic behaviors from chaotic systems by applying weak harmonic perturbations with a suitably chosen phase. However, little is known about the best strategy for selecting adequate perturbations to reach desired states. Here we use experimental measures and numerical simulations to assess the benefits of controlling individually the three terms of a Duffing oscillator. Using a real-time analog indicator able to discriminate on-the-fly periodic behaviors from chaos, we reconstruct experimentally the phase versus perturbation strength stability areas when periodic perturbations are applied to different terms governing the oscillator. We verify the system to be more sensitive to perturbations applied to the quadratic term of the double-well Duffing oscillator and to the quartic term of the single-well Duffing oscillator.

Automatic Digital Hologram Denoising by Spatiotemporal Analysis of Pixel-Wise Statistics

In this paper, a new technique to reduce the noise in a reconstructed hologram image is proposed. Unlike all the techniques in the literature, the proposed approach not only takes into account spatial information but also temporal statistics associated with the pixels. This innovative solution enables, at first, the automatic detection of the areas of the image containing the objects (foreground). This way, all the pixels not belonging to any objects are directly cleaned up and the contrast between objects and background is consistently increased. The remaining pixels are then processed with a spatio-temporal filtering which cancels out the effects of speckle noise, while preserving the structural details of the objects. The proposed approach has been compared with other common speckle denoising techniques and it is found to give better both visual and quantitative results.

Remote monitoring of building oscillation modes by means of real-time Mid Infrared Digital Holography

Non-destructive measurements of deformations are a quite common application of holography but due to the intrinsic limits in the interferometric technique, those are generally confined only to small targets and in controlled environment. Here we present an advanced technique, based on Mid Infrared Digital Holography (MIR DH), which works in outdoor conditions and provides remote and real-time information on the oscillation modes of large engineering structures. Thanks to the long wavelength of the laser radiation, large areas of buildings can be simultaneously mapped with sub-micrometric resolution in terms of their amplitude and frequency oscillation modes providing all the modal parameters vital for all the correct prevention strategies when the functionality and the health status of the structures have to be evaluated. The existing experimental techniques used to evaluate the fundamental modes of a structure are based either on seismometric sensors or on Ground-based Synthetic Aperture Radar (GbSAR). Such devices have both serious drawbacks, which prevent their application at a large scale or in the short term. We here demonstrate that the MIR DH based technique can fully overcome these limitations and has the potential to represent a breakthrough advance in the field of dynamic characterization of large structures.

Lensless Digital Holography Improves Fire Safety

House fires cause thousands of deaths every year. Firefighters and first responders are called on to work in these hostile environments where their vision is impaired due to curtains of smoke and walls of flames.

Control of entanglement dynamics in a system of three coupled quantum oscillators

Dynamical control of entanglement and its connection with the classical concept of instability is an intriguing matter which deserves accurate investigation for its important role in information processing, cryptography and quantum computing. Here we consider a tripartite quantum system made of three coupled quantum parametric oscillators in equilibrium with a common heat bath. The introduced parametrization consists of a pulse train with adjustable amplitude and duty cycle representing a more general case for the perturbation. From the experimental observation of the instability in the classical system we are able to predict the parameter values for which the entangled states exist. A different amount of entanglement and different onset times emerge when comparing two and three quantum oscillators. The system and the parametrization considered here open new perspectives for manipulating quantum features at high temperatures.

Mid-IR and terahertz digital holography based on quantum cascade lasers

Infrared (IR) digital holography (DH) based on CO2 lasers has proven to be a powerful coherent imaging technique due to the reduced sensitivity to mechanical vibrations, to the increased field of view, to the high optical power and to possible vision through scattering media, such as smoke. In this contribution we report IR DH based on the combination of quantum cascade laser (QCL) sources and a high resolution microbolometric camera. QCLs combine highly desirable features for coherent imaging, such as compactness, high optical power, and spectral purity. The present availability of external cavity mounted QCLs having a broad tuning range, makes them suitable sources for multiple wavelength holographic interferometry. In addition, QCL emission covers several windows throughout a large portion of the IR spectrum, from the mid-IR to the terahertz region. This allows taking advantage of the different optical response of the imaged objects at different frequencies, which is crucial for applications such as non-destructive testing and biomedical imaging. Our holographic system is suitable for the acquisition of both transmission holograms of transparent objects and speckle holograms of scattering objects, which can be processed in real time to retrieve both amplitude and phase.

Looking beyond Smoke and Flames by Lensless Infrared Digital Holography

To reveal what’s behind the flames is a key and challenging aim both in the industrial and, above all, in security field.

Seeing through smoke and flames: a challenge for imaging capabilities,met thanks to digital holography at far infrared

We show that imaging alive people through smoke and flames is possible by Digital Holography at far infrared. This capability is of crucial importance in the security field to provide a new tool for firefighters and first responders in fire accidents. So far, the existing thermographic infrared cameras allows to see people through dense smoke, sensing the radiation emitted by human body. However, these devices are often blinded due to the flame emission, which is collected by the zoom lenses employed for the scope, and the information of the targets beyond the flames is unavoidably lost. On the contrary, lensless Digital Holography at far infrared avoids the typical saturation of the camera detectors returning clear images of targets seen behind veils of smoke and curtains of flames. Moreover, we demonstrate that human-size holograms can be recorded, allowing to move this promising technology outside the lab for safety applications.