24,050 research outputs found
The Double Sphere Camera Model
Vision-based motion estimation and 3D reconstruction, which have numerous
applications (e.g., autonomous driving, navigation systems for airborne devices
and augmented reality) are receiving significant research attention. To
increase the accuracy and robustness, several researchers have recently
demonstrated the benefit of using large field-of-view cameras for such
applications. In this paper, we provide an extensive review of existing models
for large field-of-view cameras. For each model we provide projection and
unprojection functions and the subspace of points that result in valid
projection. Then, we propose the Double Sphere camera model that well fits with
large field-of-view lenses, is computationally inexpensive and has a
closed-form inverse. We evaluate the model using a calibration dataset with
several different lenses and compare the models using the metrics that are
relevant for Visual Odometry, i.e., reprojection error, as well as computation
time for projection and unprojection functions and their Jacobians. We also
provide qualitative results and discuss the performance of all models
General-purpose and special-purpose visual systems
The information that eyes supply supports a wide variety of functions, from the guidance systems that enable an animal to navigate successfully around the environment, to the detection and identification of predators, prey, and conspecifics. The eyes with which we are most familiar the single-chambered eyes of vertebrates and cephalopod molluscs, and the compound eyes of insects and higher crustaceans allow these animals to perform the full range of visual tasks. These eyes have evidently evolved in conjunction with brains that are capable of subjecting the raw visual information to many different kinds of analysis, depending on the nature of the task that the animal is engaged in. However, not all eyes evolved to provide such comprehensive information. For example, in bivalve molluscs we find eyes of very varied design (pinholes, concave mirrors, and apposition compound eyes) whose only function is to detect approaching predators and thereby allow the animal to protect itself by closing its shell. Thus, there are special-purpose eyes as well as eyes with multiple functions
Future Directions in Astronomy Visualisation
Despite the large budgets spent annually on astronomical research equipment
such as telescopes, instruments and supercomputers, the general trend is to
analyse and view the resulting datasets using small, two-dimensional displays.
We report here on alternative advanced image displays, with an emphasis on
displays that we have constructed, including stereoscopic projection, multiple
projector tiled displays and a digital dome. These displays can provide
astronomers with new ways of exploring the terabyte and petabyte datasets that
are now regularly being produced from all-sky surveys, high-resolution computer
simulations, and Virtual Observatory projects. We also present a summary of the
Advanced Image Displays for Astronomy (AIDA) survey which we conducted from
March-May 2005, in order to raise some issues pertitent to the current and
future level of use of advanced image displays.Comment: 13 pages, 2 figures, accepted for publication in PAS
Quantum Optics in Maxwell's Fish Eye Lens with Single Atoms and Photons
We investigate the quantum optical properties of Maxwell's two-dimensional
fish eye lens at the single-photon and single-atom level. We show that such a
system mediates effectively infinite-range dipole-dipole interactions between
atomic qubits, which can be used to entangle multiple pairs of distant qubits.
We find that the rate of the photon exchange between two atoms, which are
detuned from the cavity resonances, is well described by a model, where the
photon is focused to a diffraction-limited area during absorption. We consider
the effect of losses on the system and study the fidelity of the entangling
operation via dipole-dipole interaction. We derive our results analytically
using perturbation theory and the Born-Markov approximation and then confirm
their validity by numerical simulations. We also discuss how the
two-dimensional Maxwell's fish eye lens could be realized experimentally using
transformational plasmon optics.Comment: 20 pages, 7 figure
Fisheye Photogrammetry to Survey Narrow Spaces in Architecture and a Hypogea Environment
Nowadays, the increasing computation power of commercial grade processors has actively led to a vast spreading of image-based reconstruction software as well as its application in different disciplines. As a result, new frontiers regarding the use of photogrammetry in a vast range of investigation activities are being explored. This paper investigates the implementation of
fisheye lenses in non-classical survey activities along with the related problematics. Fisheye lenses are outstanding because of their large field of view.
This characteristic alone can be a game changer in reducing the amount of data required, thus speeding up the photogrammetric process when needed. Although they come at a cost, field of view (FOV), speed and manoeuvrability are key to the success of those optics as shown by two of the presented case studies: the survey of a very narrow spiral staircase located in the Duomo di Milano and the survey of a very narrow hypogea structure in Rome. A third case study, which deals with low-cost sensors, shows the metric evaluation of a commercial spherical camera equipped with fisheye lenses
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Evolution of the eyes of vipers with and without infrared-sensing pit organs
We examined lens and brille transmittance, photoreceptors, visual pigments, and visual opsin gene sequences of viperid snakes with and without infrared-sensing pit organs. Ocular media transmittance is high in both groups. Contrary to previous reports, small as well as large single cones occur in pit vipers. Non-pit vipers differ from pit vipers in having a twotiered retina, but few taxa have been examined for this poorly understood feature. All vipers sampled express rh1, sws1 and lws visual opsin genes. Opsin spectral tuning varies but not in accordance with the presence/absence of pit organs, and not always as predicted from gene sequences. The visual opsin genes were generally under purifying selection, with positive selection at spectral tuning amino acids in RH1 and SWS1 opsins, and at retinal pocket stabilization sites in RH1 or LWS (and without substantial differences between pit and nonpit vipers). Lack of evidence for sensory trade-off between viperid eyes (in the aspects examined) and pit organs might be explained by the high degree of neural integration of vision and infrared detection; the latter representing an elaboration of an existing sense with addition of a novel sense organ, rather than involving the evolution of a wholly novel sensory system
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