Correlation plenoptic imaging

Abstract

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 standard plenoptic 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 correlation in both momentum and position of chaotic light leads to the enhanced refocusing power of correlation plenoptic imaging with respect to standard plenoptic imaging.Plenoptic imaging (PI) is a technique aimed at capturing information on the three-dimensional lightfield of a given scene in a single shot [1]. Its key principle is to record, in the image plane, both the location and the propagation direction of the incoming light. The recorded propagation direction is exploited, in post-processing, to computationally retrace the geometrical light path, thus enabling the refocusing of different planes within the scene and the extension of the depth of field of the acquired image. As shown in Fig.1b, PI resembles standard imaging ( Fig.1a), however, a microlens array is inserted in the native image plane and the sensor array is moved behind the microlenses. On the one hand, the microlenses act as imaging pixels to gain the spatial information of the scene; on the other hand, each microlens reproduces on the sensor array an image of the camera lens, thus providing the angular information associated with each imaging pixel [2]. As a result, a trade-off between spatial and angular resolution is built in the plenoptic imaging process.Plenoptic imaging is currently used in digital cameras enhanced by refocusing capabilities [3]; in fact, in photography, PI highly simplifies both auto-focus and low-light shooting [2]. A plethora of innovative applications in 3-D imaging and sensing [4,5], stereoscopy [1,6,7] and microscopy [8-10] are also being developed. In particular, high-speed large-scale 3D funcional imaging of neuronal activity has been demonstrated [11]. However, the potentials of PI are strongly limited by the inherent inverse proportionality between image resolution and maximum achievable depth of field. Attempts to decouple resolution and depth of field based on signal processing and deconvolution have been proposed in literature [10][11][12][13][14][15].Our idea is to exploit the second-order spatio-temporal correlation properties of light to overcome this fundamental limitation. Using two correlated beams, from either a chaotic or an entangled photon source, we can perform imaging in one arm [16][17][18][19][20][21], and simultaneously obtain the angular information in the other arm. In fact, the position and momentum correlations at the core of our proposal have been demonstrated more than ten years ago by performing separate imaging and d...

Correlation plenoptic imaging between arbitrary planes

“…Furthermore, for the chaotic-light based setup, the light propagation along two almost identical optical paths provides the possibility to exploit in the most efficient way (and without adding artificial intensity balancing or amplifications), the dynamic range of the camera, as required when the two detectors are implemented by using disjoint parts of the same sensor [34].…”

Correlation Plenoptic Imaging: An Overview

“…In this case, the refocusing algorithm must be applied for different values of z b , until the optimal sharpness of the image is found. This is shown in Figure 4, where we present a simulation of different images of an out of-focus object [67]: (a) the blurred ghost image; (b) the refocused CPI image; (c) and (d) two refocusing attempts with the correct value of z a and an incorrect value of z b . The last two images are evidently less sharp than the one in (b).…”

“…We show an image (b) refocused by using the correct value of z b , and two images (c,d) refocused at wrong distances z b = 60 mm and z b = 90 mm, respectively. Reproduced with the permission from[67], copyright 2017 Society of Photo-Optical Instrumentation Engineers.…”