On the physical nonexistence of signals going backwards in time, and quantum mechanics

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Correlation plenoptic imaging

Plenoptic imaging is a promising optical modality that simultaneously captures the location and the propagation direction of light in order to enable three-dimensional imaging in a single shot. However, in classical imaging systems, the maximum spatial and angular resolutions are fundamentally linked; thereby, the maximum achievable depth of field is inversely proportional to the spatial resolution. We propose to take advantage of the second-order correlation properties of light to overcome this fundamental limitation. In this paper, we demonstrate that the momentum/position correlation of chaotic light leads to the enhanced refocusing power of correlation plenoptic imaging with respect to standard plenoptic imaging.Comment: 6 pages, 3 figure

Signal-to-noise properties of correlation plenoptic imaging with chaotic light

Correlation Plenoptic Imaging (CPI) is a novel imaging technique, that exploits the correlations between the intensity fluctuations of light to perform the typical tasks of plenoptic imaging (namely, refocusing out-of-focus parts of the scene, extending the depth of field, and performing 3D reconstruction), without entailing a loss of spatial resolution. Here, we consider two different CPI schemes based on chaotic light, both employing ghost imaging: the first one to image the object, the second one to image the focusing element. We characterize their noise properties in terms of the signal-to-noise ratio (SNR) and compare their performances. We find that the SNR can be significantly higher and easier to control in the second CPI scheme, involving standard imaging of the object; under adequate conditions, this scheme enables reducing by one order of magnitude the number of frames for achieving the same SNR.Comment: 12 pages, 3 figure

Exploring plenoptic properties of correlation imaging with chaotic light

In a setup illuminated by chaotic light, we consider different schemes that enable to perform imaging by measuring second-order intensity correlations. The most relevant feature of the proposed protocols is the ability to perform plenoptic imaging, namely to reconstruct the geometrical path of light propagating in the system, by imaging both the object and the focusing element. This property allows to encode, in a single data acquisition, both multi-perspective images of the scene and light distribution in different planes between the scene and the focusing element. We unveil the plenoptic property of three different setups, explore their refocusing potentialities and discuss their practical applications.Comment: 9 pages, 4 figure

Correlation Plenoptic Imaging With Entangled Photons

Plenoptic imaging is a novel optical technique for three-dimensional imaging in a single shot. It is enabled by the simultaneous measurement of both the location and the propagation direction of light in a given scene. In the standard approach, the maximum spatial and angular resolutions are inversely proportional, and so are the resolution and the maximum achievable depth of focus of the 3D image. We have recently proposed a method to overcome such fundamental limits by combining plenoptic imaging with an intriguing correlation remote-imaging technique: ghost imaging. Here, we theoretically demonstrate that correlation plenoptic imaging can be effectively achieved by exploiting the position-momentum entanglement characterizing spontaneous parametric down-conversion (SPDC) photon pairs. As a proof-of-principle demonstration, we shall show that correlation plenoptic imaging with entangled photons may enable the refocusing of an out-of-focus image at the same depth of focus of a standard plenoptic device, but without sacrificing diffraction-limited image resolution.Comment: 12 pages, 5 figure

Campi di battaglia allo zenith: le foto aeree come strumenti di misura delle forze nemiche e la conoscenza del territorio durante la Prima Guerra Mondiale

Il XXXV Convegno Nazionale della SISFA si è sviluppato in diverse sezioni sui principali temi di ricerca in storia della scienza, dall’antichità fino alla fisica del XX e XXI secolo. Due sessioni del congresso sono state dedicate alla didattica scientifica nelle scuole e nei musei, alla strumentaria scientifica e alle relative collezioni. Oltre che su tali temi “istituzionali” il Convegno SISFA si è focalizzato su argomenti speciali collegati all’Anno Internazionale della Luce 2015 e ai diversi anniversari celebrati durante il 2015, come il centenario dell’intervento dell’Italia nella Prima Guerra Mondiale, il centenario della Teoria della Relatività Generale, il settantesimo anniversario del bombardamento di Hiroshima e Nagasaki. La sessione “History of Light” ha stimolato importanti riflessioni sui diversi approcci scientifici allo studio della luce, sui suoi usi sociali e spettacolari. Infine la sessione “Science and World War I” ha evidenzato le posizioni degli scienziati italiani riguardo il primo conflitto mondiale, rivelando peculiari attitudini verso la Guerra, le interazioni con i contesti internazionali e gli effetti sulla ricerca scientifica fino al periodo post-bellico.Between 1915 and 1918 having good quality aerial photo shooting taken from balloons, airships and airplanes inspired the development of new image capturing techniques and the research for new scientific methods to interpret images aiming at providing troops at war with strategic information about the enemy and its position on the battle field. The new reading from the air of the territory presented itself as a scientific approach that supported war planning. Pioneers in Italy were the photographers from the Military Photographic Division of the Regiment of the Engineering Corps, which saw collaboration between military representatives, photographers and scientists. The integration of different disciplinary competencies made it possible to transform the two-dimensional representation of the landscape into a meaningful description of the 3-dimensional reality of a bombardier. Notions of descriptive geometry were associated to geological knowledge, to high-speed photography techniques and stereoscopy, to experiences in photo developing and printing. All this produced a measuring of the war based on a description, that for the time qualified as “very faithful”, of the enemy positioning and the territory that bring to a new vision of time and space

Diffraction-limited plenoptic imaging with correlated light

Traditional optical imaging faces an unavoidable trade-off between resolution and depth of field (DOF). To increase resolution, high numerical apertures (NA) are needed, but the associated large angular uncertainty results in a limited range of depths that can be put in sharp focus. Plenoptic imaging was introduced a few years ago to remedy this trade off. To this aim, plenoptic imaging reconstructs the path of light rays from the lens to the sensor. However, the improvement offered by standard plenoptic imaging is practical and not fundamental: the increased DOF leads to a proportional reduction of the resolution well above the diffraction limit imposed by the lens NA. In this paper, we demonstrate that correlation measurements enable pushing plenoptic imaging to its fundamental limits of both resolution and DOF. Namely, we demonstrate to maintain the imaging resolution at the diffraction limit while increasing the depth of field by a factor of 7. Our results represent the theoretical and experimental basis for the effective development of the promising applications of plenoptic imaging.Comment: 10 pages, 10 figure

Correlation Plenoptic Imaging between Arbitrary Planes

We propose a novel method to perform plenoptic imaging at the diffraction limit by measuring second-order correlations of light between two reference planes, arbitrarily chosen, within the tridimensional scene of interest. We show that for both chaotic light and entangled-photon illumination, the protocol enables to change the focused planes, in post-processing, and to achieve an unprecedented combination of image resolution and depth of field. In particular, the depth of field results larger by a factor 3 with respect to previous correlation plenoptic imaging protocols, and by an order of magnitude with respect to standard imaging, while the resolution is kept at the diffraction limit. The results lead the way towards the development of compact designs for correlation plenoptic imaging devices based on chaotic light, as well as high-SNR plenoptic imaging devices based on entangled photon illumination, thus contributing to make correlation plenoptic imaging effectively competitive with commercial plenoptic devices.Comment: 12 pages, 6 figure

Nonclassical noise features in a correlation plenoptic imaging setup

Sub-shot-noise imaging and correlation plenoptic imaging are two quantum imaging techniques that enable to overcome different problems of classical imaging systems. Combining the two techniques is not trivial, since the former is based on the detection of identical corresponding modes to subtract noise, while the latter requires the detection of different modes to perform directional reconstruction. In this paper, we experimentally show the possibility to obtain a noise-reduction factor smaller than one, a necessary condition to perform sub-shot-noise imaging, in a setup that can be adapted to correlation plenoptic imaging