Light-field ghost imaging

Open Access

Light-field ghost imaging

A. Paniate, G. Massaro, A. Avella, A. Meda, F.V. Pepe, M. Genovese, M. D'Angelo, and I. Ruo-Berchera

Phys. Rev. Applied 21, 024032 – Published 15 February 2024

Abstract

Techniques based on classical and quantum correlations in light beams, such as ghost imaging, allow us to overcome many limitations of conventional imaging and sensing protocols. Despite their advantages, applications of such techniques are often limited in practical scenarios where the position and the longitudinal extension of the target object are unknown. In this work, we propose and experimentally demonstrate an imaging technique, named light-field ghost imaging, that exploits light correlations and light-field imaging principles to enable going beyond the limitations of ghost imaging in a wide range of applications. Notably, our technique removes the requirement to have prior knowledge of the object distance, allowing the possibility of refocusing in postprocessing, as well as performing three-dimensional imaging while retaining all the benefits of ghost imaging protocols.

Received 1 September 2023
Revised 29 November 2023
Accepted 19 January 2024

DOI:https://doi.org/10.1103/PhysRevApplied.21.024032

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Ghost imaging Imaging & optical processing Quantum optics

Atomic, Molecular & Optical

Authors & Affiliations

A. Paniate ^1,2,†, G. Massaro ^3,4,†, A. Avella ^2,*, A. Meda², F.V. Pepe ^3,4, M. Genovese ², M. D'Angelo ^3,4,‡, and I. Ruo-Berchera^2,‡

¹DISAT, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino 10129, Italy
²Quantum metrology and nano technologies division, INRiM, Strada delle Cacce 91, Torino 10135, Italy
³Dipartimento Interateneo di Fisica, Università degli Studi di Bari Aldo Moro, Bari 70125, Italy
⁴Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Bari, Bari 70125, Italy

^*Corresponding author. a.avella@inrim.it
^†These authors contributed equally to this work.
^‡Equal last author contribution.

Article Text

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References

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Issue

Vol. 21, Iss. 2 — February 2024

Subject Areas

Optics

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Images

Figure 1
Schematic of the LFGI: a collimated beam from a cw laser at 532 nm, after being spatially (SPF) and polarization filtered (Pol.), is shone onto a rotating diffusing glass (Arecchi’s disk). The scattered light is collected by a far-field lens with focal length $f_{f} = 75$ mm. The disk and the far-field lens form random speckle patterns at the polarizing beam splitter (PBS). The rotation of the glass generates, in time, different patterns that are equally split by the PBS with a polarization angle of $\pm 45^{\circ}$ with respect to the axis of the linear polarizer. The speckle pattern has a diameter of 2 cm and each speckle has an averaged transversal size of about $8 μ m$ and an averaged longitudinal length of about $1$ mm. One beam is imaged by a light-field camera, composed of a lens with focal length $f_{l} = 80$ mm and an MLA of dimension $30 \times 30$ . Each microlens has a focal length $f_{MLA} = 14.6$ mm and a diameter $d = 300 μ m$ . The MLA is placed at a distance equal to its focal length $f_{MLA}$ from a charge-coupled-device (CCD) camera [Andor Luca R (604)]. The other beam probes the object and is imaged with a lens of focal length $f_{b} = 75$ mm to a CCD camera (Andor iXon Ultra): the bucket detector is obtained by integrating the signal from all illuminated pixels.
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Figure 2
Experimental reconstructions of a “4”-shaped sample as a function of displacement. A two-level mask is moved at different displacements from the GI-on-focus plane and the GI and LFGI reconstructions are retrieved. For each displacement, $5 \times 10^{4}$ independent patterns are acquired with an integration time of 15 ms.
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Figure 3
Resolution of GI and LFGI as a function of the displacement. (a) The curves represent the set of points where the visibility of a double slit is exactly 40% for the GI-microlens-limited, GI-pixel-limited, and LFGI reconstructions, respectively. (b) Examples of GI and LFGI reconstructions of double-slit masks with different separations and different displacements, as indicated by the red circles in (a). The same conclusions can be derived from the other points (“2′,” “3′,” “4,” “4′”) that are not reported for brevity. All LFGI reconstructions show visibility greater than or equal to $40 %$ .
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Figure 4
Refocusing ability of LFGI. (a) Two 1-mm-wide slits ( ${slit}_{1}$ and ${slit}_{2}$ ) are placed with displacement $- 80$ and $+ 80$ mm, respectively, in the configuration shown in the figure. (b) In the picture on the left, LFGI is employed to refocus ${slit}_{1}$ , while ${slit}_{2}$ is out of focus; conversely, in the right-hand picture, LFGI refocuses the plane of ${slit}_{2}$ .
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Figure 5
Schematic representation of the principle of LFGI. Panel (a) shows the scheme when the object is imaged (through correlation measurements) in the zero plane of the light-field camera (i.e., the GI is at focus). Panel (b) shows the scheme when the object is displaced by a distance $δ$ with respect to case (a). The difference between the two cases gives rise to different optical paths for the two pairs of rays emitted by the extreme points of the object. In the focused case, rays emitted by the same object point arrive on the same microlens, regardless of the emission angle. Plenoptic information is irrelevant in this situation. On the contrary, when the ghost image is out of focus, different microlenses are crossed, and specific pixels are illuminated depending on the angle of emission. The quantities and labels appearing in the figure are defined in the text.
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Physical Review Applied