Light-field microscopy represents a promising solution for microscopic volumetric imaging, thanks to its capability to encode information on multiple planes in a single acquisition. This is achieved through its peculiar simultaneous capture of information on light spatial distribution and propagation direction. However, state-of-the-art light-field microscopes suffer from a detrimental loss of spatial resolution compared to standard microscopes. In this article, we experimentally demonstrate the working principle of a new scheme, called Correlation Light-field Microscopy (CLM), where the correlation between two light beams is exploited to achieve volumetric imaging with a resolution that is only limited by diffraction. In CLM, a correlation image is obtained by measuring intensity correlations between a large number of pairs of ultra-short frames; each pair of frames is illuminated by the two correlated beams, and is exposed for a time comparable with the source coherence time. We experimentally show the capability of CLM to recover the information contained in out-of-focus planes within three-dimensional test targets and biomedical phantoms. In particular, we demonstrate the improvement of the depth of field enabled by CLM with respect to a conventional microscope characterized by the same resolution. Moreover, the multiple perspectives contained in a single correlation image enable reconstructing over 50 distinguishable transverse planes within a 1 mm3 sample.
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.
Light-field imaging is an inspiring modality for high-speed volumetric imaging We demonstrate diffraction-limited extended volumetric imaging by a light-field microscope exploiting spatio-temporal correlations of light, overcoming the resolution limitations of conventional implementations of light-field imaging.
We proposed a novel tomography approach to the correlation plenoptic imaging of objects described by a distribution of the absorption coefficients. Using the maximum-likelihood absorption tomography we overcome classical plenoptic refocusing algorithm avoiding reconstruction artifacts.
We present a novel approach to three-dimensional optical microscopy, named correlation light-field microscopy (CLM). This approach is based on correlation plenoptic imaging and exploits correlations between intensity fluctuations, intrinsic in chaotic light, to retrieve both spatial information about the intensity distribution of light on the sample and angular information about the directions of propagation of the light rays. Such a plenoptic (or light-field) information about the sample enables an extension of the natural depth of field, while avoiding the intrinsic loss of spatial resolution occurring in conventional light-field microscopy. We discuss the capability of CLM of refocusing out-of-focus planes of the sample, paving the way to scanning-free three-dimensional reconstruction while keeping the at-focus resolution at the diffraction limit showing a brief comparison with light-field microscopy. Finally we discuss the perspective of improvements in CLM acquisition speed by the integration of SPAD array sensors in the setup.
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