21,070 research outputs found
Non-line-of-sight tracking of people at long range
A remote-sensing system that can determine the position of hidden objects has
applications in many critical real-life scenarios, such as search and rescue
missions and safe autonomous driving. Previous work has shown the ability to
range and image objects hidden from the direct line of sight, employing
advanced optical imaging technologies aimed at small objects at short range. In
this work we demonstrate a long-range tracking system based on single laser
illumination and single-pixel single-photon detection. This enables us to track
one or more people hidden from view at a stand-off distance of over 50~m. These
results pave the way towards next generation LiDAR systems that will
reconstruct not only the direct-view scene but also the main elements hidden
behind walls or corners
Computational periscopy with an ordinary digital camera
Computing the amounts of light arriving from different directions enables a diffusely reflecting surface to play the part of a mirror in a periscope—that is, perform non-line-of-sight imaging around an obstruction. Because computational periscopy has so far depended on light-travel distances being proportional to the times of flight, it has mostly been performed with expensive, specialized ultrafast optical systems^1,2,3,4,5,6,7,8,9,10,11,12. Here we introduce a two-dimensional computational periscopy technique that requires only a single photograph captured with an ordinary digital camera. Our technique recovers the position of an opaque object and the scene behind (but not completely obscured by) the object, when both the object and scene are outside the line of sight of the camera, without requiring controlled or time-varying illumination. Such recovery is based on the visible penumbra of the opaque object having a linear dependence on the hidden scene that can be modelled through ray optics. Non-line-of-sight imaging using inexpensive, ubiquitous equipment may have considerable value in monitoring hazardous environments, navigation and detecting hidden adversaries.We thank F. Durand, W. T. Freeman, Y. Ma, J. Rapp, J. H. Shapiro, A. Torralba, F. N. C. Wong and G. W. Wornell for discussions. This work was supported by the Defense Advanced Research Projects Agency (DARPA) REVEAL Program contract number HR0011-16-C-0030. (HR0011-16-C-0030 - Defense Advanced Research Projects Agency (DARPA) REVEAL Program)Accepted manuscrip
Revealing hidden scenes by photon-efficient occlusion-based opportunistic active imaging
The ability to see around corners, i.e., recover details of a hidden scene
from its reflections in the surrounding environment, is of considerable
interest in a wide range of applications. However, the diffuse nature of light
reflected from typical surfaces leads to mixing of spatial information in the
collected light, precluding useful scene reconstruction. Here, we employ a
computational imaging technique that opportunistically exploits the presence of
occluding objects, which obstruct probe-light propagation in the hidden scene,
to undo the mixing and greatly improve scene recovery. Importantly, our
technique obviates the need for the ultrafast time-of-flight measurements
employed by most previous approaches to hidden-scene imaging. Moreover, it does
so in a photon-efficient manner based on an accurate forward model and a
computational algorithm that, together, respect the physics of three-bounce
light propagation and single-photon detection. Using our methodology, we
demonstrate reconstruction of hidden-surface reflectivity patterns in a
meter-scale environment from non-time-resolved measurements. Ultimately, our
technique represents an instance of a rich and promising new imaging modality
with important potential implications for imaging science.Comment: Related theory in arXiv:1711.0629
Virtual Mirrors: Non-Line-of-Sight Imaging Beyond the Third Bounce
Non-line-of-sight (NLOS) imaging methods are capable of reconstructing
complex scenes that are not visible to an observer using indirect illumination.
However, they assume only third-bounce illumination, so they are currently
limited to single-corner configurations, and present limited visibility when
imaging surfaces at certain orientations. To reason about and tackle these
limitations, we make the key observation that planar diffuse surfaces behave
specularly at wavelengths used in the computational wave-based NLOS imaging
domain. We call such surfaces virtual mirrors. We leverage this observation to
expand the capabilities of NLOS imaging using illumination beyond the third
bounce, addressing two problems: imaging single-corner objects at limited
visibility angles, and imaging objects hidden behind two corners. To image
objects at limited visibility angles, we first analyze the reflections of the
known illuminated point on surfaces of the scene as an estimator of the
position and orientation of objects with limited visibility. We then image
those limited visibility objects by computationally building secondary
apertures at other surfaces that observe the target object from a direct
visibility perspective. Beyond single-corner NLOS imaging, we exploit the
specular behavior of virtual mirrors to image objects hidden behind a second
corner by imaging the space behind such virtual mirrors, where the mirror image
of objects hidden around two corners is formed. No specular surfaces were
involved in the making of this paper
Virtual mirrors: non-line-of-sight imaging beyond the third bounce
Non-line-of-sight (NLOS) imaging methods are capable of reconstructing complex scenes that are not visible to an observer using indirect illumination. However, they assume only third-bounce illumination, so they are currently limited to single-corner configurations, and present limited visibility when imaging surfaces at certain orientations. To reason about and tackle these limitations, we make the key observation that planar diffuse surfaces behave specularly at wavelengths used in the computational wave-based NLOS imaging domain. We call such surfaces virtual mirrors. We leverage this observation to expand the capabilities of NLOS imaging using illumination beyond the third bounce, addressing two problems: imaging single-corner objects at limited visibility angles, and imaging objects hidden behind two corners. To image objects at limited visibility angles, we first analyze the reflections of the known illuminated point on surfaces of the scene as an estimator of the position and orientation of objects with limited visibility. We then image those limited visibility objects by computationally building secondary apertures at other surfaces that observe the target object from a direct visibility perspective. Beyond single-corner NLOS imaging, we exploit the specular behavior of virtual mirrors to image objects hidden behind a second corner by imaging the space behind such virtual mirrors, where the mirror image of objects hidden around two corners is formed. No specular surfaces were involved in the making of this paper
Spicy science: David Julius and the discovery of temperature-sensitive TRP channels.
This invited biographical review covers the career of Dr. David Julius and his discovery of thermosensitive TRP channels. Dr. Julius is currently the Morris Herzstein Chair in Molecular Biology and Medicine and Professor and Chair of Physiology at the University of California, San Francisco Medical School. He is a member of the National Academy of Sciences and has received many distinguished awards for his landmark discoveries of the molecular basis of pain and thermosensation
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