Apparatus and method for plenoptic reconstruction of indirect images of object

Abstract

Disclosed herein is an apparatus (10; 10 ') for plenoptic reconstruction of an indirect image of an object (OBJ). 20; 30); 40); 50; 60; 70; 80); 90; 100) is provided. Different from the prior art, due to the characteristics of the plenoptic image acquisition device PC, the problem of focusing an indirect image under the condition that an object (OBJ) is positioned outside a focusing plane can be solved, and the image does not need to be newly acquired. Although indirect images are only visible after evaluation of correlation, refocusing may be performed by using data available in plenoptic acquisition if such images are out of focus. Therefore, regardless of the position of the object, an indirect image of the object can be reconstructed, and an indirect image of a moving object can be reconstructed.

Description

Technical Field

[0001] The present invention relates to an apparatus and a method for indirect reconstruction of an image, commonly known as ghost imaging. Background Art

[0002] Ghost imaging (GI) is a non-invasive technique by which the image of an object can be reconstructed without the need for a detector provided with a spatial resolution suitable for directly acquiring the image of the object. The image is obtained by using two spatially correlated electromagnetic emissions: the former, the reference emission (the emission of the space arm), which never interacts with the object but is measured by a detector with spatial resolution; the latter, the emission illuminating the object, which is measured by a single-pixel detector without spatial resolution (a so-called bucket detector). The image is reconstructed by temporally correlating the signal intensity collected by each pixel of the sensor on the reference arm (or space arm) with the signal recorded by the single-pixel detector in the object arm.

[0003] Ghost imaging acquires an image of only the relevant electromagnetic emission, which can in principle be located anywhere as long as it is related to the electromagnetic emission impinging on the object and is acquired by a single-pixel sensor.

[0004] In other words, ghost imaging is based on the assumption that the intensity distribution of the electromagnetic emission recorded by the detector with spatial resolution is related to the intensity distribution of the electromagnetic emission interacting with the object. Since the intensity distributions of both emissions vary during propagation, one of the technical requirements for ghost imaging is the exact knowledge of the position of the object plane.

[0005] In practice, it is not easy to reconstruct indirect images (ghost images) outside laboratory conditions, since the need to have correlated electromagnetic emissions (especially light rays) limits the positioning of objects to a well-defined plane, which is not always known accurately enough under real operating conditions. In this regard, the reconstruction of an image with an acceptable signal-to-noise ratio requires the acquisition of a large number of frames and the subsequent calculation of correlations; thus, methods of finding a focused image of an object with unknown position by trial and error take a long time or are even impossible if the object is moving or even if it is damaged by radiation.

[0006] This situation may reduce the applicability of ghost imaging because, unlike conventional imaging techniques, focus may not be obtained using a single intensity measurement, as the indirect image is only visible after the evaluation of the correlation. In other words, ghost imaging does not enable real-time acquisition or reconstruction of images.

[0007] Purpose of the Invention

[0008] The present invention aims to solve the above technical problems. Specifically, the present invention aims to use ghost imaging technology to perform image reconstruction while relaxing the constraints on the knowledge of the object's plane position and / or the object's state (stationary or moving). Summary of the invention

[0009] The objects of the invention are achieved by means of an apparatus and a method having the characteristics set out in the following claims, which constitute an essential part of the technical disclosure related to the invention provided herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The invention will now be described with reference to the accompanying drawings, which are provided by way of non-limiting example only, and in which:

[0011] - Figure 1 , Figure 2 , Figure 2A , Figure 3 , Figure 4 each showing an embodiment of a device according to the invention,

[0012] - FIG. 5A to FIG. 5D The application of the device according to the invention in the case of different types of objects is shown,

[0013] - Figures 6 to 10 Further embodiments of the invention are also shown, which feature different configurations of the space arms. DETAILED DESCRIPTION

[0014] Reference numerals 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 in the above listed figures denote corresponding embodiments of an apparatus for plenoptic reconstruction of an indirect image according to the present invention.

[0015] In various embodiments, the apparatus 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 comprises:

[0016] a first electromagnetic emissions detector BD configured to be struck by first electromagnetic emissions E1, in particular light emissions, coming from a source S and having a first propagation path P1, wherein in use an object OBJ, the indirect image of which is to be reconstructed, is arranged along the first propagation path P1,

[0017] - A second electromagnetic emissions detector PC configured to be struck by second electromagnetic emissions E2 , in particular optical emissions, coming from the source S and having a second propagation path P2 .

[0018] The first electromagnetic emission detector BD is a so called "bucket type detector" and comprises a first (single) sensor element configured to emit a signal proportional to the intensity of the first electromagnetic emission E1 impinging on the first sensor element. An object OBJ is arranged between the detector BD and the source S along a propagation path P1.

[0019] According to the invention, the second electromagnetic emission detector PC comprises a plenoptical image acquisition device (i.e. a so-called light field image acquisition device; therefore, throughout the description, reference PC may be used to denote a plenoptical image acquisition device), comprising a second sensor element configured to detect the spatial distribution of the intensity of the second electromagnetic emission E2, as well as information about the direction of origin of the second electromagnetic emission E2 at a plurality of spatial positions on the second sensor element.

[0020] In various embodiments, the device 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 further comprises a processing unit configured to reconstruct an indirect image or a ghost image of the object OBJ by means of a correlation measure of the signals from the electromagnetic emission detectors BD and PC. In particular, the correlation measure is obtained based on a reconstruction of the electromagnetic emission E2 on a focusing plane π by using information from the second electromagnetic emission detector PC, in particular a signal from a second sensor element. The plane π is arranged upstream of the detector PC and at a distance z from the source S. b .

[0021] The processing unit may conveniently be arranged as a device external to the apparatus 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or an integrated structure may be envisaged in which the control unit is part of the apparatus 10, 20, 30, 40, 50, 60, 70, 80, 90, 100.

[0022] Figures 1 to 10 The various embodiments in the drawings are intended to show different functional and / or structural configurations of the basic device according to the present invention.

[0023] Figures 1 to 4 Detailed description of the drawings shows embodiments of a device according to the invention which differ from one another in the type of source S generating electromagnetic emissions and / or in the configuration of the device.

[0024] Reference Figure 1, in the device 10, the first electromagnetic emission E1 and the second electromagnetic emission E2 are secondary electromagnetic emissions. Specifically, the related emissions E1 and E2 are separated from the same primary electromagnetic emission E0, which originates from a single source S corresponding to a quantum light source. Examples of such sources include SPDC (spontaneous parametric down conversion) sources, FWM (four wave mixing) sources, atomic cascade sources.

[0025] To this end, the device 10 comprises a beam splitter BS configured to be struck by the emission E0 and to separate the emission E0 into emissions E1 and E2. With respect to the so-called "object arm", i.e. the optical arm in which the electromagnetic emission strikes the object OBJ and the object OBJ is "seen" by the detector BD, a lens IL with a focal length F has a beam splitter BS located at a distance z from the source S. a and a reference plane at a distance z0 from the object OBJ, which is arranged between the lens IL and the detector BD. For example, in the case of a thin lens, the reference plane coincides with the plane of the lens, while in the case of a thick lens, the reference plane may include the main plane of the lens or one of the adjacent faces of the lens.

[0026] With respect to the so-called "space arm", emission E2 has a propagation path P2 starting from emission E0 and ending in impinging on the plenoptic image acquisition device PC. The focal plane π at which the indirect image of the object OBJ is reconstructed (as described above) is arranged at a distance Z from the source S. b at, and upstream of the detector PC.

[0027] As shown in the figure, in order to reconstruct the indirect image of the object OBJ focused on the plane π, the following relationship must be satisfied in the ghost imaging: 1 / (z a +z b )+1 / z0=1 / F. If this condition is not verified, the out-of-focus image can be refocused by using the plenoptic information provided by the plenoptic image acquisition device PC.

[0028] Reference Figure 2 , the device 20 differs from the device 10 in the absence of both the lens IL and the beam splitter BS. The source S is a quantum light source that produces two correlated emissions. Examples of such sources include SPDC (spontaneous parametric down conversion) sources, FWM (four wave mixing) sources, atomic cascade sources. In the device 20, the first electromagnetic emission E1 and the second electromagnetic emission E2 are primary electromagnetic emissions of the same source S. As for the so-called "object arm", i.e., the optical arm in which the electromagnetic emission E1 impinges on the object OBJ, this arm is located between the source S and the detector BD, at a distance z1 from the source S itself.

[0029] With respect to the spatial arm, the emission E2 has a propagation path P2 developing from the source S to the plenoptic image acquisition device PC. The focus plane π at which the indirect image of the object OBJ is reconstructed is located at a distance z2 from the source S. If the distances z1 and z2 are the same, the indirect image on the plane π is focused. If this is not the case, the out-of-focus image can be refocused by using the plenoptic information provided by the plenoptic image acquisition device PC.

[0030] exist Figure 2 In the figure, the distances z1 and z2 are chosen so that they are in the far field relative to the source S; this condition can be achieved by lenses or free propagation).

[0031] Reference Figure 2A , the device 20A differs from the device 20 by the presence of the lens IL. The source S is again a quantum light source producing two correlated emissions. In the device 20A, the first electromagnetic emission E1 and the second electromagnetic emission E2 are primary electromagnetic emissions of the same source S. With respect to the so-called "object arm", i.e. the optical arm in which the electromagnetic emission E1 impinges on the object OBJ, the object OBJ is located between the source S and the detector BD, at a distance z0 from the source S itself.

[0032] With respect to the spatial arm, a lens with focal length F has a reference plane arranged at a distance z'0 from the source S. The focus plane π of the indirect image of the object OBJ is arranged at a distance z"0 from the reference plane of the lens IL and upstream of the detector PC. As shown in the figure, in order to reconstruct the indirect image of the object OBJ, the following relationship must be satisfied:

[0033] 1 / (z0+z'0)+1 / z'0=1 / F

[0034] If the condition is not verified, the out-of-focus image may be refocused by using the plenoptic information provided by the plenoptic image acquisition device PC.

[0035] Reference Figure 3 , the device 30 corresponds substantially to Figure 1 and Figure 2 The device maintains a hybrid configuration. Figure 1 The general structure of , with a beam splitter BS, but without a lens IL. The source S is a chaotic light source, for example, thermal light or pseudo-thermal light. The beam splitter BS is arranged in the field of view of the source, and it is configured to be impacted by the emission E0 and to separate the emission E0 into emissions E1 and E2. With respect to the object arm, the object OBJ is arranged at a distance z1 from the source S, and it is located between the source S and the detector BD.

[0036] With respect to the spatial arm, emission E2 has a propagation path P2 starting from emission E0 and ending at the impact of the plenoptic image acquisition device PC. The focus plane π, where the indirect image of the object OBJ is formed, is arranged at a distance z2 from the source S. In order to reconstruct a focused indirect image of the object OBJ on the focus plane π, in ghost imaging, the distances z1 and z2 must be the same. If this is not the case, the out-of-focus image can be refocused by using the plenoptic information provided by the plenoptic image acquisition device PC.

[0037] Figure 4 The device 40 in is similar to the device 30, but the source S is a classical or quantum light source generating primary emissions E0 with two different wavelengths. To this end, the device 40 comprises a dichroic mirror or beam splitter BS, which is located in the field of view of the source S and is configured to be struck by the emission E0 and to separate the emission E0 into emissions E1 and E2 at two wavelengths, respectively. With respect to the object arm, the object OBJ is arranged at a distance z1 from the source S and it is located between the source S and the detector BD.

[0038] With respect to the space arm, emission E2 has a propagation path P2 starting from emission E0 and ending at an impact on the plenoptic image acquisition device PC. The focal plane π, on which the indirect image of the object OBJ is formed, is arranged at a distance z2 from the source S. In order to reconstruct a focused indirect image of the object OBJ on the focal plane π, in ghost imaging, the distances z1 and z2 must satisfy the relationship z1=(λ2 / λ1)z2, where λ1 and λ2 are the wavelengths of the light in the object arm (secondary emission E1) and in the space arm (secondary emission E2). If this is not the case, the out-of-focus image can be refocused by using the plenoptic information provided by the plenoptic image acquisition device PC.

[0039] FIG. 5A to FIG. 5D The figure in FIG. 1 shows the behavior of a device according to the invention (all devices 10 to 100, although for simplicity only one of them is shown in each example) in the following situation: there is a reflecting object OBJ (device 50A, Figure 5A ; detector BD is obviously arranged on the same side of source S relative to the object, the object is reflective), diffuse object (device 50B, Figure 5B ), launching objects (device 50C, Figure 5C ; Transmitters E1, P1 continue to be transmitters E1', P1') and objects OBJ (device 50D, which behave as saturated reactors Figure 5D ).

[0040] Reference Figures 6 to 10 , embodiments of the device according to the invention will now be described which differ from one another in the configuration of the plenoptic detector PC. Again, with reference to FIG. Figure 2) (chosen only as an example), but the structure of the detector PC is more detailed than in the previous figure.

[0041] Reference Figure 6 , the device 60 includes the plenoptic image acquisition device PC as described above, usually referred to as "Plenoptic Camera 1.0". The plenoptic image acquisition device of the device 60 includes a device having a focal length f s The microlens array MLA has a focal length f m A main lens ML and a sensor element MS having a pixel array configuration, wherein a microlens array MLA is arranged between the microlens array ML and the sensor element MS.

[0042] The sensor element MS is positioned at a distance f from the microlens array MLA. s At, that is, with the focal length f s The main lens ML is arranged at a distance z2 from the microlens array MLA, and the focusing plane π on which the indirect image is formed is positioned at a distance z1 from the main lens ML so as to satisfy the relationship 1 / z1+1 / z2=1 / f m . In other words, the main lens ML is configured to reconstruct an image of the focal plane π on the plane on which the microlens array MLA is positioned (wherein the indirect image is reconstructed according to the above-described process). Furthermore, each microlens produces a far field of the light impinging on it on the sensor. In the case of a source S of chaotic light, the distance z0 between the object OBJ and the source S and between the plane π and the source S can have any length, while if the source S emits quantum-modulated electromagnetic radiation, the distance z0 must ensure that the object and the plane π are in the far field of the source S itself. By using the plenoptic information provided by the plenoptic image acquisition device PC, the out-of-focus image on the plane π can be refocused.

[0043] The reference RFI denotes the refocusing interval of the plenoptic camera PC, ie the beam of parallel planes on which the indirect image of the object can be refocused.

[0044] Reference Figure 7 , the device 70 is configured as a modification of the device 60, so that the main lens ML is again configured to create an indirect image of the object OBJ on the microlens array MLA.

[0045] In this case, the sensor element MS is positioned at a distance z3 from the microlens array MLA, the main lens ML is positioned at a distance z2 from the microlens array MLA, and the focal plane π forming the indirect image is positioned at a distance z1 from the main lens ML. Each microlens of the array MLA forms an image of the main lens ML on a corresponding (usually smaller) part of the sensor.

[0046] In order for each microlens to project a focused image of the plane of the lens ML onto the sensor MS, the following relationship must be satisfied: 1 / z2+1 / z3=1 / f s In order for the lens ML to project the plane π onto the plane of the microlens MLA, the following relationship must be satisfied: 1 / z1+1 / z2=1 / f m If this is not the case, the out-of-focus image can be refocused by using the plenoptic information provided by the plenoptic image acquisition device PC.

[0047] In the case of a source S of chaotic light, the distance z0 between the object OBJ and the source and between the plane π and the source can be of any length, whereas if the source S emits entangled photons, the object must be located in the far field. As in the case of the device 60, the value RFI represents the operating interval of the plenoptic camera PC, i.e. the beam of parallel planes on which the indirect image of the object can be refocused.

[0048] Reference Figure 8 , the device 80 is configured as a modification of the device 70, wherein the main lens ML is configured to create an indirect image of the object OBJ on an intermediate plane π' arranged between the microlens array MLA and the lens ML itself.

[0049] Furthermore, each microlens forms an image of the plane π' in the corresponding part of the sensor MS.

[0050] The plenoptic image acquisition device PC of the device 80 is generally referred to as a plenoptic camera 2.0.

[0051] The sensor element MS is positioned at a distance z4 from the microlens array ML, the main lens ML is positioned at a distance z2 from the plane π' and the microlens array MLA is positioned at a distance z3 from the plane π'. The focus plane π forming the focused indirect image is positioned at a distance z1 from the main lens ML.

[0052] In order to focus the indirect image on the plane π', the following relationship must be satisfied: 1 / z1+1 / z2=1 / f m , and in order to form an image of plane π' on the sensor of each microlens, the following relationship must be satisfied: 1 / z3+1 / z4=1 / f s If the previous condition is not verified, the out-of-focus image can be refocused by using the plenoptic information provided by the plenoptic image acquisition device PC.

[0053] In the case of a source S with chaotic light, the distance z0 between the object OBJ and the source and between the plane π and the source can be of any length, whereas if the source S emits entangled photons, they must be in the far field. As in the case of the device 60, the value RFI represents the operating interval of the plenoptic camera PC, i.e. the beam of parallel planes that can refocus the indirect image of the object OBJ.

[0054] Reference Fig. 9 , the device 90 is configured as a modification of the device 60 without the main lens ML and in which the microlens array MLA is arranged in a position coinciding with the focal plane π at which the indirect image of the object OBJ is reconstructed. In this configuration, each microlens forms an image of the source on a corresponding portion of the sensor element MS. The plenoptic image acquisition device PC of the device 90 is again of the type generally referred to as a plenoptic camera 1.0.

[0055] The sensor element MS is positioned at a distance z1 from the microlens array MLA, which in turn is located at a distance z0 from the source S, which is the same as the distance between the object OBJ and the source itself.

[0056] As mentioned before, in the case of a source S with chaotic light, the distance z0 between the object OBJ and the source S and between the plane π and the source S can have any length, while if the source S emits quantum correlated electromagnetic radiation, the distance z0 must ensure that the object OBJ and the plane π are located in the far field of the source S itself.

[0057] In order for the microlens to form an image of the source, the following relationship must be satisfied: 1 / z0+1 / z1=1 / f s .

[0058] In order to form an indirect image of the object OBJ on the microlens, the plane of the microlens must be positioned at a distance z0 from the source.

[0059] If the second relationship is not satisfied, the out-of-focus image may be refocused by using the plenoptic information provided by the plenoptic image acquisition device PC.

[0060] As in the case of the device 60 , the value RFI represents the operating interval of the plenoptic camera PC, ie the beams of parallel planes that make it possible to refocus the indirect image of the object OBJ.

[0061] Reference Fig.10 , the device 100 is configured as a modification of the device 80 without the main lens ML and wherein the microlens array MLA is arranged at a distance z1 from the focal plane π of the indirect image. The plenoptic image acquisition device PC of the device 100 is of a type generally referred to as a plenoptic camera 2.0.

[0062] The sensor element MS is positioned at a distance z2 from the microlens array MLA, which in turn is located at a distance z1 from the plane π, which is located at a distance z0 from the source S (this distance is the same as the distance between the object OBJ and the source itself). As mentioned before, in the case of a source S with chaotic light, the distance z0 between the object OBJ and the source S and between the plane π and the source S can be of any length, while if the source S emits quantum correlated electromagnetic radiation, the distance z0 must ensure that both the object OBJ and the plane π are located in the far field of the source S itself.

[0063] The out-of-focus image on plane π can be refocused by using the plenoptic information provided by the plenoptic image acquisition device PC.

[0064] In order for the indirect image to be focused on plane π, the following relationship must be true: 1 / z1+1 / z2=1 / f s If this is not true, then the out-of-focus image can be refocused by using the plenoptic information provided by the plenoptic image acquisition device PC.

[0065] As in the case of the device 60 , the value RFI represents the operating interval of the plenoptic camera PC, ie the beams of parallel planes that make it possible to refocus the indirect image of the object OBJ.

[0066] The general operation of the devices 10 to 100 will now be described.

[0067] Each of the devices 10 to 100 is configured for plenoptic reconstruction of an indirect image (ghost image) of an object OBJ. Unlike the ghost imaging techniques of the known art, the devices according to the invention are not constrained by the positioning of the object in a specific plane, since they can refocus an out-of-focus indirect image by exploiting the characteristics of the plenoptic image acquisition device PC. In other words, in contrast to the known devices, the spatial arm uses a plenoptic image acquisition device instead of a conventional image acquisition device providing two-dimensional acquisition.

[0068] Using the apparatuses 10 to 100, a plenoptic reconstruction of an indirect image of an object may be obtained by a method comprising the following steps:

[0069] A method for plenoptic reconstruction of an indirect image, comprising:

[0070] - propagating a first electromagnetic emission E1 and a second electromagnetic emission E2 from a source S, the first electromagnetic emission E1 having a first propagation path P1 and the second electromagnetic emission E2 having a second propagation path P2,

[0071] - placing along said first propagation path P1 an object OBJ whose indirect image is to be reconstructed,

[0072] - detecting intensity information of said first electromagnetic emission by means of a first electromagnetic emission detector BD, said first electromagnetic emission detector BD comprising a first sensor element configured to emit a first signal proportional to the intensity of said first electromagnetic emission E1 impinging on a first sensor, said object OBJ being arranged along a first propagation path P1 between the source (S) and the first electromagnetic emission detector,

[0073] - detecting intensity information of the second electromagnetic emission by means of a second electromagnetic emission detector PC, the second electromagnetic emission detector comprising a plenoptic image acquisition device comprising a second sensor element configured to detect a spatial distribution of the intensity of the second electromagnetic emission E2, and information about the direction of origin of the second electromagnetic emission E2 at a plurality of spatial positions on the second sensor element,

[0074] - reconstructing an indirect image of said object OBJ by means of a correlation measure of a first signal from the first electromagnetic emission detector BD and a second signal from the second electromagnetic emission detector PC within a time interval, wherein:

[0075] Each first signal is proportional to the intensity of said first electromagnetic emission E1,

[0076] Each second signal comprises information on the spatial distribution of the intensity of the second electromagnetic emission E2 and information on the direction of origin of the second electromagnetic emission E2 at a plurality of spatial positions on the second sensor element.

[0077] The reconstruction of the image of the object OBJ is obtained by an algorithm that combines the time series of the signal emitted by the detector BD due to the interaction with the electromagnetic emission E1 and the signal associated with each pixel of the plenoptic image acquisition device PC and provides a measure of their statistical dependence.

[0078] One class of algorithms ideally comprises two parts: the former consists in reconstructing the intensity distribution of the emission E2 on a plane relative to the plane of the object OBJ by means of a combination of the pixel signals of the plenoptic image acquisition device PC. This part of the algorithm depends on the type of plenoptic image acquisition device PC used (see Figures 6 to 10 ). The second part of the algorithm envisages applying a statistical function which provides a measure of the dependence between each point of the reconstructed image of the emission E2 and the signal of the detector BD.

[0079] Information about the image of the object OBJ and the direction of the light interacting with it is contained in the function S(x j ), where x j is the position of the jth pixel of the reconstructed frame of the intensity distribution of emission E2 (measurement starting from the plenoptic image acquisition device PC).

[0080] Generally speaking, S(x j ) relates to the signal N1 acquired by the barrel BD and the signal N2 acquired by each pixel of the plenoptic camera PC (x j ). An example of a statistical function is the covariance, which provides an array of values ​​as many as there are pixels of the plenoptic image acquisition device PC, obtained by estimating, for each pixel of the plenoptic image acquisition device PC, the time average of the product of the difference of its value from its mean value and the difference of the signal of the detector BD from its mean value:

[0081] S(x j )=<(N1- <n1>)(N2(x j )- <N2(x j )>)>

[0082] Another example is the Pearson correlation coefficient, ie the value of the covariance divided by the product of the standard deviation of the pixel's signal and the standard deviation of the signal of the detector BD, pixel by pixel.

[0083] A further example is the correlation coefficient of differential ghost imaging, i.e. the covariance of the plenoptic image acquisition device PC and the detector BD (pixel by pixel), from which the product of the sum of all pixels of the reconstructed image and the time average of the detector BD is subtracted, divided by the time average of the sum of the pixels of the plenoptic image acquisition device PC.

[0084] An alternative algorithm (although it produces equivalent results) envisages calculating the above mentioned statistical function between the signal of the detector BD and each pixel of the sensor MS of the plenoptic image acquisition device PC. Subsequently, the plenoptic reconstruction algorithm for each map will be applied to the resulting array.

[0085] Due to the devices 10 to 100 according to the present invention, the field of application of indirect image reconstruction (ghost imaging) can be broadened, because even if the object OBJ is not located at a position that satisfies the focusing condition on the plane π, the out-of-focus image can be refocused by using the plenoptic information provided by the plenoptic image acquisition device PC. In other words, although the indirect image is only visible after the evaluation of the correlation, if the image is out of focus, it can be refocused by using the data available in the plenoptic acquisition. Therefore, it is possible to reconstruct the indirect image of an object regardless of where such an object is located, as well as the indirect imaging of a moving object.

[0086] Of course, the implementation details and the embodiments may vary considerably with respect to what has been described and illustrated above, without departing from the scope of protection of the invention as defined in the appended claims.

Claims

1. A device (10; 20; 30; 40; 50; 60; 70; 80; 90; 100) for plenoptic reconstruction of an indirect image of an object (OBJ), the device comprising: a first electromagnetic emission detector (BD) configured to be struck by a first electromagnetic emission (E1) coming from a source (S) and having a first propagation path (P1), wherein during use, an object (OBJ) of which an indirect image is to be reconstructed is arranged at a position along said first propagation path (P1) between said source (S) and the first detector (BD), - a second electromagnetic emission detector (PC) configured to be struck by a second electromagnetic emission (E2) coming from said source (S) and having a second propagation path (P2), in: - said first electromagnetic emission detector (BD) comprises a first sensor element configured to emit a signal proportional to the intensity of said first electromagnetic emission (E1) impinging on said first sensor element, -The second electromagnetic emission detector (PC) comprises a plenoptic image acquisition device comprising a second sensor element, the second sensor element being configured to detect the spatial distribution of the intensity of the second electromagnetic emission (E2) and information about the origin direction of the second electromagnetic emission (E2) at multiple spatial positions on the second sensor element.

2. The device (10; 20; 30; 40; 50; 60; 70; 80; 90; 100) according to claim 1, further comprising a processing unit configured to reconstruct an indirect image of the object (OBJ) by means of a correlation measure of a first signal from the first electromagnetic emission detector (BD) and a second signal from the second electromagnetic emission detector (PC) within a time interval, wherein: each first signal is proportional to the intensity of said first electromagnetic emission (E1), Each second signal comprises information on the spatial distribution of the intensity of the second electromagnetic emission (E2) and information on the direction of origin of the second electromagnetic emission (E2) at a plurality of spatial positions on the second sensor element.

3. The device (10; 30; 40) according to claim 1 or claim 2, wherein: The first electromagnetic emission (E1) and the second electromagnetic emission (E2) are separate secondary electromagnetic emissions from the same primary electromagnetic emission (E0) of a source.

4. The device (20; 50; 60; 70; 80; 90; 100) according to claim 1 or claim 2, wherein: The first electromagnetic emission (E1) and the second electromagnetic emission (E2) are mutually related primary electromagnetic emissions of a source (S).

5. A method for plenoptic reconstruction of an indirect image, the method comprising: - propagating a first electromagnetic emission (E1) and a second electromagnetic emission (E2) from a source (S), the first electromagnetic emission (E1) having a first propagation path (P1) and the second electromagnetic emission (E2) having a second propagation path (P2), - placing along said first propagation path (P1) an object (OBJ) whose indirect image is to be reconstructed, - detecting intensity information of the first electromagnetic emission by means of a first electromagnetic emission detector (BD) comprising a first sensor element, the first sensor element being configured to emit a first signal proportional to the intensity of the first electromagnetic emission (E1) impinging on the first sensor element, the object (OBJ) being arranged along the first propagation path (P1) between the source (S) and the first electromagnetic emission detector, - detecting intensity information of the second electromagnetic emission by means of a second electromagnetic emission detector (PC), the second electromagnetic emission detector comprising a plenoptic image acquisition device, the plenoptic image acquisition device comprising a second sensor element, the second sensor element being configured to detect a spatial distribution of the intensity of the second electromagnetic emission (E2), and information about the direction of origin of the second electromagnetic emission (E2) at a plurality of spatial positions on the second sensor element, - reconstructing an indirect image of said object (OBJ) by means of a correlation measure of a first signal from said first electromagnetic emission detector (BD) and a second signal from said second electromagnetic emission detector (PC) within a time interval, wherein: each first signal is proportional to the intensity of said first electromagnetic emission (E1), Each second signal comprises information on the spatial distribution of the intensity of the second electromagnetic emission (E2) and information on the direction of origin of the second electromagnetic emission (E2) at a plurality of spatial positions on the second sensor element.

6. The method according to claim 5, wherein: The first electromagnetic emission (E1) and the second electromagnetic emission (E2) are separate secondary electromagnetic emissions of the same primary electromagnetic emission (E0) from the source (S).

7. The method according to claim 6, wherein: The first electromagnetic emission (E1) and the second electromagnetic emission (E2) are related primary electromagnetic emissions from the source (S).

8. The method according to claim 5, wherein: The reconstructing of the indirect image of the object (OBJ) by means of a correlation measure comprises reconstructing the second electromagnetic emission (E2) on a focus plane (π) using the second signal, wherein the focus plane (π) is arranged upstream of the second electromagnetic emission detector (PC).

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