12 research outputs found
Intensity interferometry-based 3D imaging
The development of single-photon counting detectors and arrays has made
tremendous steps in recent years, not the least because of various new
applications in, e.g., LIDAR devices. In this work, a 3D imaging device based
on real thermal light intensity interferometry is presented. By using gated
SPAD technology, a basic 3D scene is imaged in reasonable measurement time.
Compared to conventional approaches, the proposed synchronized photon counting
allows using more light modes to enhance 3D ranging performance. Advantages
like robustness to atmospheric scattering or autonomy by exploiting external
light sources can make this ranging approach interesting for future
applications
Multisource Holography
Holographic displays promise several benefits including high quality 3D
imagery, accurate accommodation cues, and compact form-factors. However,
holography relies on coherent illumination which can create undesirable speckle
noise in the final image. Although smooth phase holograms can be speckle-free,
their non-uniform eyebox makes them impractical, and speckle mitigation with
partially coherent sources also reduces resolution. Averaging sequential frames
for speckle reduction requires high speed modulators and consumes temporal
bandwidth that may be needed elsewhere in the system.
In this work, we propose multisource holography, a novel architecture that
uses an array of sources to suppress speckle in a single frame without
sacrificing resolution. By using two spatial light modulators, arranged
sequentially, each source in the array can be controlled almost independently
to create a version of the target content with different speckle. Speckle is
then suppressed when the contributions from the multiple sources are averaged
at the image plane. We introduce an algorithm to calculate multisource
holograms, analyze the design space, and demonstrate up to a 10 dB increase in
peak signal-to-noise ratio compared to an equivalent single source system.
Finally, we validate the concept with a benchtop experimental prototype by
producing both 2D images and focal stacks with natural defocus cues.Comment: 14 pages, 9 figures, to be published in SIGGRAPH Asia 202
Analysis of an Active Deformylation Mechanism of 5‐Formyl‐deoxycytidine (fdC) in Stem Cells
The removal of 5‐methyl‐deoxycytidine (mdC) from promoter elements is associated with reactivation of the silenced corresponding genes. It takes place through an active demethylation process involving the oxidation of mdC to 5‐hydroxymethyl‐deoxycytidine (hmdC) and further on to 5‐formyl‐deoxycytidine (fdC) and 5‐carboxy‐deoxycytidine (cadC) with the help of α‐ketoglutarate‐dependent Tet oxygenases. The next step can occur through the action of a glycosylase (TDG), which cleaves fdC out of the genome for replacement by dC. A second pathway is proposed to involve C−C bond cleavage that converts fdC directly into dC. A 6‐aza‐5‐formyl‐deoxycytidine (a‐fdC) probe molecule was synthesized and fed to various somatic cell lines and induced mouse embryonic stem cells, together with a 2′‐fluorinated fdC analogue (F‐fdC). While deformylation of F‐fdC was clearly observed in vivo, it did not occur with a‐fdC, thus suggesting that the C−C bond‐cleaving deformylation is initiated by nucleophilic activation
Neural \'{E}tendue Expander for Ultra-Wide-Angle High-Fidelity Holographic Display
Holographic displays can generate light fields by dynamically modulating the
wavefront of a coherent beam of light using a spatial light modulator,
promising rich virtual and augmented reality applications. However, the limited
spatial resolution of existing dynamic spatial light modulators imposes a tight
bound on the diffraction angle. As a result, modern holographic displays
possess low \'{e}tendue, which is the product of the display area and the
maximum solid angle of diffracted light. The low \'{e}tendue forces a sacrifice
of either the field-of-view (FOV) or the display size. In this work, we lift
this limitation by presenting neural \'{e}tendue expanders. This new breed of
optical elements, which is learned from a natural image dataset, enables higher
diffraction angles for ultra-wide FOV while maintaining both a compact form
factor and the fidelity of displayed contents to human viewers. With neural
\'{e}tendue expanders, we experimentally achieve 64 \'{e}tendue
expansion of natural images in full color, expanding the FOV by an order of
magnitude horizontally and vertically, with high-fidelity reconstruction
quality (measured in PSNR) over 29 dB on retinal-resolution images
eLearning COLEACP : un dispositif de formation au service des professionnels du secteur agricole en Afrique
Le dispositif de formation à distance du COLEACP (Comité de Liaison Europe-Afrique-Caraïbes-Pacifique) est une composante d'un système complet de formation dédié au renforcement des capacités des opérateurs des filières agricoles des pays ACP (Afrique Caraïbes et Pacifique)
Seifan et al - Field survey information
Species recorded in the field survey under different environmental conditions. DRY/WET – plots with low/high flooding probabilities respectively; M+/ M– – plots with/without mole activity respectively. For each species listed, its abundance (number of individuals found in the survey plots) per environmental condition is given