761 research outputs found
Street View Motion-from-Structure-from-Motion
We describe a structure-from-motion framework that handles “generalized ” cameras, such as moving rolling-shutter cameras, and works at an unprecedented scale— billions of images covering millions of linear kilometers of roads—by exploiting a good relative pose prior along vehicle paths. We exhibit a planet-scale, appearance-augmented point cloud constructed with our framework and demonstrate its practical use in correcting the pose of a street-level image collection. 1
Solid-fluid transition in a granular shear flow
The rheology of a granular shear flow is studied in a quasi-2d rotating
cylinder. Measurements are carried out near the midpoint along the length of
the surface flowing layer where the flow is steady and non-accelerating.
Streakline photography and image analysis are used to obtain particle
velocities and positions. Different particle sizes and rotational speeds are
considered. We find a sharp transition in the apparent viscosity ()
variation with rms velocity (). In the fluid-like region above the depth
corresponding to the transition point (higher rms velocities) there is a rapid
increase in viscosity with decreasing rms velocity. Below the transition depth
we find for all the different cases studied and the
material approaches an amorphous solid-like state deep in the layer. The
velocity distribution is Maxwellian above the transition point and a Poisson
velocity distribution is obtained deep in the layer. The observed transition
appears to be analogous to a glass transition.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let
Measuring the Angular Velocity of a Propeller with Video Camera Using Electronic Rolling Shutter
Noncontact measurement for rotational motion has advantages over the traditional method which measures rotational motion by means of installing some devices on the object, such as a rotary encoder. Cameras can be employed as remote monitoring or inspecting sensors to measure the angular velocity of a propeller because of their commonplace availability, simplicity, and potentially low cost. A defect of the measurement with cameras is to process the massive data generated by cameras. In order to reduce the collected data from the camera, a camera using ERS (electronic rolling shutter) is applied to measure angular velocities which are higher than the speed of the camera. The effect of rolling shutter can induce geometric distortion in the image, when the propeller rotates during capturing an image. In order to reveal the relationship between the angular velocity and the image distortion, a rotation model has been established. The proposed method was applied to measure the angular velocities of the two-blade propeller and the multiblade propeller. The experimental results showed that this method could detect the angular velocities which were higher than the camera speed, and the accuracy was acceptable
Direct Sparse Odometry with Rolling Shutter
Neglecting the effects of rolling-shutter cameras for visual odometry (VO)
severely degrades accuracy and robustness. In this paper, we propose a novel
direct monocular VO method that incorporates a rolling-shutter model. Our
approach extends direct sparse odometry which performs direct bundle adjustment
of a set of recent keyframe poses and the depths of a sparse set of image
points. We estimate the velocity at each keyframe and impose a
constant-velocity prior for the optimization. In this way, we obtain a near
real-time, accurate direct VO method. Our approach achieves improved results on
challenging rolling-shutter sequences over state-of-the-art global-shutter VO
Towards High-Frequency Tracking and Fast Edge-Aware Optimization
This dissertation advances the state of the art for AR/VR tracking systems by
increasing the tracking frequency by orders of magnitude and proposes an
efficient algorithm for the problem of edge-aware optimization.
AR/VR is a natural way of interacting with computers, where the physical and
digital worlds coexist. We are on the cusp of a radical change in how humans
perform and interact with computing. Humans are sensitive to small
misalignments between the real and the virtual world, and tracking at
kilo-Hertz frequencies becomes essential. Current vision-based systems fall
short, as their tracking frequency is implicitly limited by the frame-rate of
the camera. This thesis presents a prototype system which can track at orders
of magnitude higher than the state-of-the-art methods using multiple commodity
cameras. The proposed system exploits characteristics of the camera
traditionally considered as flaws, namely rolling shutter and radial
distortion. The experimental evaluation shows the effectiveness of the method
for various degrees of motion.
Furthermore, edge-aware optimization is an indispensable tool in the computer
vision arsenal for accurate filtering of depth-data and image-based rendering,
which is increasingly being used for content creation and geometry processing
for AR/VR. As applications increasingly demand higher resolution and speed,
there exists a need to develop methods that scale accordingly. This
dissertation proposes such an edge-aware optimization framework which is
efficient, accurate, and algorithmically scales well, all of which are much
desirable traits not found jointly in the state of the art. The experiments
show the effectiveness of the framework in a multitude of computer vision tasks
such as computational photography and stereo.Comment: PhD thesi
Development and On-sky Demonstration of Atmospheric Turbulence Profiler for Future Adaptive Optics with Multiple Laser Guide Stars
Tohoku University博士(理学)thesi
Flux profile scanners for scattered high-energy electrons
The paper describes the design and performance of flux integrating Cherenkov
scanners with air-core reflecting light guides used in a high-energy, high-flux
electron scattering experiment at the Stanford Linear Accelerator Center. The
scanners were highly radiation resistant and provided a good signal to
background ratio leading to very good spatial resolution of the scattered
electron flux profile scans.Comment: 22 pages, 17 figure
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