Narrow Field Of View Research Articles

The real first weather satellite picture

The real first weather satellite picture

The role of the anterior lateral eyes in the vision-based behaviour of jumping spiders

Jumping spiders, or salticids, sample their environment using a combination of two types of eyes. The forward-facing pair of 'principal' eyes have narrow fields of view, but exceptional spatial resolution, while the two or three pairs of 'secondary' eyes have wide fields of view and function especially well as motion analysers. Motion detected by the secondary eyes may elicit an orienting response, whereupon the object of interest is examined further using the high-acuity principal eyes. The anterior lateral (AL) eyes are particularly interesting, as they are the only forward-facing pair of secondary eyes. In this study, we aimed to determine characteristics of stimuli that elicit orienting responses mediated by the AL eyes. After covering all eyes except the AL eyes, we measured orienting responses to dot stimuli that varied in size and contrast, and moved at different speeds. We found that all stimulus parameters had significant effects on orientation propensity. When tethered flies were used as prey, we found that visual information from the AL eyes alone was sufficient to elicit stalking behaviour. These results suggest that, in terms of overall visual processing, the relevance of spatial vision in the AL eyes has been underestimated in the literature. Our results also show that female spiders are significantly more responsive than males. We found that hunger caused similar increases in orientation propensity in the two sexes, but females responded more often than males both when sated and when hungry. A higher propensity by females to orient toward moving objects may be related to females tending to experience higher nutritional demands than males.

Fundamental matrix of planar catadioptric stereo systems

Planar mirror has been used successfully in catadioptric stereo systems to capture stereo images with a single camera. These planar catadioptric stereo (PCS) systems not only provide radiometric advantages over traditional two-camera stereo, but also reduce the complexity and cost of acquiring stereoscopic video. Although many papers have been published on the design of the PCS system, few studies have been conducted for the analysis of its epipolar geometry, that is, the fundamental matrix. In this study, the authors investigated features of two types of PCS system and verified that they both can be approximated by affine epipolar geometry. This affine property is either because of constraints on the structure of the PCS system or because of the narrow field of view (FOV) of the mirror. This affine model reduces the number of parameters in the fundamental matrix from seven in the conventional stereo system to only four in the PCS system. Experimental results based on various criteria verify that by using the affine model with fewer parameters, estimation of the fundamental matrix for a PCS system can be more robust, precise and much easier to implement. These significant advantages confirm the usefulness of an affine fundamental matrix model for the PCS systems.

A Generic Method for RPC Refinement Using Ground Control Information

Geometric sensor models are used in image processing to model the relationship between object space and image space and to transform image data to conform to a map projection. An Rational Polynomial Coefficient (RCP) is a generic sensor model that can be used to transform images from a variety of different high resolution satellite and airborne remote sensing systems. To date, numerous researchers have published papers about RPC refinement, aimed at improving the accuracy of the results. So far, the Bias Compensation method is the one that is the most accepted and widely used, but this method has rigorous conditions that limit its use; namely, it can only be used to improve the RPC of images obtained from cameras with a narrow field of view and small attitude errors, such as those used on Ikonos or QuickBird satellites. In many cases, these rigorous conditions may not be satisfied (e.g., cameras with a wide field of view and some satellites with large ephemeris and attitude errors). Therefore, a more robust method that can be used to refine the RPC under a wider range of conditions is desirable. In this paper, a generic method for RPC refinement is proposed. The method first restores the sensor's pseudo position and attitude, then adjusts these parameters using ground control points. Finally a new RPC is generated based on the sensor's adjusted position and attitude. We commence our paper with a review of the previous ten years of research directed toward RPC refinement, and compare the characteristics of different refinement methods that have been proposed to date. We then present a methodology for a proposed generic method for RPC refinement and describe the results of two sets of experiments that compare the proposed Generic method with the Bias Compensation method. The results confirm that the Bias Compensation method works well only when the aforementioned rigorous conditions are met. The accuracy of the RPC refined by the Bias Compensation method decreased rapidly with the sensor's position error and attitude error. In contrast to this, the Generic method proposed in this paper was found to yield highly accurate results under a variety of different sensor positions and attitudes.

Computer‐based endoscopic image‐processing technology for endourology and laparoscopic surgery

Endourology and laparoscopic surgery are evolving in accordance with developments in instrumentation and progress in surgical technique. Recent advances in computer and image-processing technology have enabled novel images to be created from conventional endoscopic and laparoscopic video images. Such technology harbors the potential to advance endourology and laparoscopic surgery by adding new value and function to the endoscope. The panoramic and three-dimensional images created by computer processing are two outstanding features that can address the shortcomings of conventional endoscopy and laparoscopy, such as narrow field of view, lack of depth cue, and discontinuous information. The wide panoramic images show an anatomical 'map' of the abdominal cavity and hollow organs with high brightness and resolution, as the images are collected from video images taken in a close-up manner. To assist in laparoscopic surgery, especially in suturing, a three-dimensional movie can be obtained by enhancing movement parallax using a conventional monocular laparoscope. In tubular organs such as the prostatic urethra, reconstruction of three-dimensional structure can be achieved, implying the possibility of a liquid dynamic model for assessing local urethral resistance in urination. Computer-based processing of endoscopic images will establish new tools for endourology and laparoscopic surgery in the near future.

A generalized measurement equation and van Cittert-Zernike theorem for wide-field radio astronomical interferometry

We derive a generalized van Cittert-Zernike (vC-Z) theorem for radio astronomy that is valid for partially polarized sources over an arbitrarily wide field of view (FoV). The classical vC-Z theorem is the theoretical foundation of radio astronomical interferometry, and its application is the basis of interferometric imaging. Existing generalized vC-Z theorems in radio astronomy assume, however, either paraxiality (narrow FoV) or scalar (unpolarized) sources. Our theorem uses neither of these assumptions, which are seldom fulfiled in practice in radio astronomy, and treats the full electromagnetic field. To handle wide, partially polarized fields, we extend the two-dimensional (2D) electric field (Jones vector) formalism of the standard ‘Measurement Equation’ (ME) of radio astronomical interferometry to the full three-dimensional (3D) formalism developed in optical coherence theory. The resulting vC-Z theorem enables full-sky imaging in a single telescope pointing, and imaging based not only on standard dual-polarized interferometers (that measure 2D electric fields) but also electric tripoles and electromagnetic vector-sensor interferometers. We show that the standard 2D ME is easily obtained from our formalism in the case of dual-polarized antenna element interferometers. We also exploit an extended 2D ME to determine that dual-polarized interferometers can have polarimetric aberrations at the edges of a wide FoV. Our vC-Z theorem is particularly relevant to proposed, and recently developed, wide FoV interferometers such as Low Frequency Array (LOFAR) and Square Kilometer Array (SKA), for which direction-dependent effects will be important.

Linear Quasi-Parallax SfM Using Laterally-Placed Eyes

A large class of visual systems in the biological world often has multiple eyes in simultaneous motion and yet has little or no overlap in the visual fields between the eyes. These systems include the lateral eyes found in many vertebrates and the compound eyes in insects. Instead of computing feature correspondences between the eyes, which might not even be possible due to the lack of overlap in the visual fields, we exploit the organizational possibility offered by the eye topography. In particular, we leverage on the pair of visual rays that are parallel to each other but opposite in direction, and compute what we call the quasi-parallax for translation recovery. Besides resulting in parsimonious visual processing, the quasi-parallax term also enhances the information pick-up for the translation, as it is almost rotation-free. The rotation is subsequently recovered from a pencil of visual rays using the individual epipolar constraints of each camera. As a result of using these different and appropriate aspects of visual rays for motion recovery, our method is numerically more effective in disambiguating the translation and rotation. In comparison to the gold standard solution obtained by the bundle adjustment (BA) technique, our method has a better Fisher information matrix for a lateral eye pair, as well as a superior experimental performance under the case of narrow field of view. For other eye configurations, the two methods achieve comparable performances, with our linear method slightly edging the nonlinear BA method when there exists imperfection in the calibration.

Ground-Based Observational Support for Spacecraft Exploration of the Outer Planets

This report presents both a retrospective of ground-based support for spacecraft missions to the outer solar system and a perspective of support for future missions. Past support is reviewed in a series of case studies involving the author. The most basic support is essential, providing the mission with information without which the planned science would not have been accomplished. Another is critical, without which science would have been returned, but missing a key element in its understanding. Some observations are enabling by accomplishing one aspect of an experiment which would otherwise not have been possible. Other observations provide a perspective of the planet as a whole which is not available to instruments with narrow fields of view and limited spatial coverage, sometimes motivating a re-prioritizing of experiment objectives. Ground-based support is also capable of providing spectral coverage not present in the complement of spacecraft instruments. Earth-based observations also have the capability of filling in gaps of spacecraft coverage of atmospheric phenomena, as well as providing surveillance of longer-term behavior than the coverage available to the mission. Future missions benefiting from ground-based support would include the Juno mission to Jupiter in the next decade, a flagship-class mission to the Jupiter or to the Saturn systems currently under consideration, and possible intermediate-class missions which might be proposed in NASA’s New Frontiers category. One of the principal benefits of future 30 m-class giant telescopes would be to improve the spatial resolution of maps of temperature and composition which are derived from observations of thermal emission at mid-infrared and longer wavelengths. In many situations, this spatial resolution is competitive with those of the relevant instruments on the spacecraft themselves.

Endoscopic Repair of Anterior Table Frontal Sinus Fractures

Frontal sinus fractures account for 5 to 15% of all maxillofacial injuries. The majority of these fractures are the result of high-velocity injuries such as motor vehicle accidents, assaults, and sporting events. The treatment algorithm for complex frontal sinus fractures is controversial due to the associated risks of brain injury, meningitis, cerebrospinal fluid fistula, and mucocele formation. However, mild to moderately displaced anterior table fractures carry a relatively low risk of long-term morbidity and are generally treated as aesthetic deformities. Unfortunately, the coronal approach for repair of these injuries is associated with significant sequelae including a large scar, alopecia, paresthesias, and, uncommonly, facial nerve injury. These sequelae may result in a greater cosmetic deformity than does the initial injury. Consequently, an endoscopic approach to these injuries has recently been described. The advantages of endoscopic surgery include limited incisions, reduced soft tissue dissection, reduced risk of alopecia, minimal risk of postoperative paresthesias, reduced hospital stay, and improved patient selection. Disadvantages include a moderate learning curve, narrow field of view, lack of depth perception, and the fact that the surgeon cannot operate bimanually without an assistant.

Contiguous‐slice zonally oblique multislice (CO‐ZOOM) diffusion tensor imaging: Examples of in vivo spinal cord and optic nerve applications

To describe and demonstrate a new technique that allows diffusion tensor imaging of small structures such as the spinal cord (SC) and optic nerve (ON) with contiguous slices and reduced image distortions using a narrow field of view (FOV). Images were acquired with a modified single-shot echo-planar imaging (EPI) sequence that contains a refocusing radio frequency (RF) pulse in the presence of the phase-encoding (rather than slice-select) gradient. As a result, only a narrow volume may be both excited and refocused, removing the problem of signal aliasing for narrow FOVs. Two variants of this technique were developed: cardiac gating is included in the study of the SC to reduce pulsation artifacts, whereas inversion-recovery (IR) cerebrospinal fluid (CSF) suppression is utilized in the study of the ON to eliminate partial volume effects. The technique was evaluated with phantoms, and mean diffusivity (MD) and fractional anisotropy (FA) measurements were made in the SC and ON of two healthy volunteers. The technique provides contiguous-slice, reduced-FOV images that do not suffer from aliasing and have reduced magnetic susceptibility artifacts. MD and FA values determined here lie within the ranges quoted in the literature. Contiguous-slice zonally orthogonal multislice (CO-ZOOM-EPI is a new technique for diffusion-weighted imaging of small structures such as the ON and SC with high resolution and reduced distortions due to susceptibility variations. This technique is able to acquire contiguous slices that may allow further nerve-tracking analyses.

Scaling behavior of auroral luminosity fluctuations observed by Auroral Large Imaging System (ALIS)

Auroral images obtained by the Auroral Large Imaging System, an optical facility with extremely low noise level and large dynamical range, have been examined in order to study the scaling properties of spatial variations in auroral luminosity. The images under examination were obtained during substorm conditions and contained active auroral forms of different types. The field of view was ±17° from magnetic zenith, which allowed the investigation of auroral fluctuations at scales from 6.4 to 51.2 km. The narrow field of view is assumed to decrease the contamination from aspect angle broadening which leads to distortions of scaling characteristics in the horizontal plane. We analyzed the logscale diagrams constructed by discrete wavelet transform of the data as well as the standard deviation, kurtosis, and probability density functions of the fluctuations. It is found that the data series for substorm auroral forms often reveal closeness to self‐similarity, the observed scaling exponent varying between 0.6 and 0.7. Auroral fluctuations in different emission lines exhibit a very similar scaling behavior. A comparison is performed with fluctuations in an electric field observed by the Dynamics Explorer 2 satellite under substorm conditions. It is shown that the intermittency features are more pronounced for substorm electric fields than for auroral fluctuations.

PoGOLite – A high sensitivity balloon-borne soft gamma-ray polarimeter

We describe a new balloon-borne instrument (PoGOLite) capable of detecting 10% polarisation from 200 mCrab point-like sources between 25 and 80 keV in one 6-h flight. Polarisation measurements in the soft gamma-ray band are expected to provide a powerful probe into high energy emission mechanisms as well as the distribution of magnetic fields, radiation fields and interstellar matter. Synchrotron radiation, inverse Compton scattering and propagation through high magnetic fields are likely to produce high degrees of polarisation in the energy band of the instrument. We demonstrate, through tests at accelerators, with radioactive sources and through computer simulations, that PoGOLite will be able to detect degrees of polarisation as predicted by models for several classes of high energy sources. At present, only exploratory polarisation measurements have been carried out in the soft gamma-ray band. Reduction of the large background produced by cosmic-ray particles while securing a large effective area has been the greatest challenge. PoGOLite uses Compton scattering and photo-absorption in an array of 217 well-type phoswich detector cells made of plastic and BGO scintillators surrounded by a BGO anticoincidence shield and a thick polyethylene neutron shield. The narrow field of view (FWHM = 1.25 msr, 2.0 deg × 2.0 deg) obtained with detector cells and the use of thick background shields warrant a large effective area for polarisation measurements (∼228 cm 2 at E = 40 keV) without sacrificing the signal-to-noise ratio. Simulation studies for an atmospheric overburden of 3–4 g/cm 2 indicate that neutrons and gamma-rays entering the PDC assembly through the shields are dominant backgrounds. Off-line event selection based on recorded phototube waveforms and Compton kinematics reduce the background to that expected for a ∼100 mCrab source between 25 and 50 keV. A 6-h observation of the Crab pulsar will differentiate between the Polar Cap/Slot Gap, Outer Gap, and Caustic models with greater than 5 σ significance; and also cleanly identify the Compton reflection component in the Cygnus X-1 hard state. Long-duration flights will measure the dependence of the polarisation across the cyclotron absorption line in Hercules X-1. A scaled-down instrument will be flown as a pathfinder mission from the north of Sweden in 2010. The first science flight is planned to take place shortly thereafter.

Integrated fluorescence and transmission electron microscopy

Correlative microscopy is a powerful technique that combines the strengths of fluorescence microscopy and electron microscopy. The first enables rapid searching for regions of interest in large fields of view while the latter exhibits superior resolution over a narrow field of view. Routine use of correlative microscopy is seriously hampered by the cumbersome and elaborate experimental procedures. This is partly due to the use of two separate microscopes for fluorescence and electron microscopy. Here, an integrated approach to correlative microscopy is presented based on a laser scanning fluorescence microscope integrated in a transmission electron microscope. Using this approach the search for features in the specimen is greatly simplified and the time to carry out the experiment is strongly reduced. The potential of the integrated approach is demonstrated at room temperature on specimens of rat intestine cells labeled with AlexaFluor488 conjugated to wheat germ agglutinin and on rat liver peroxisomes immunolabeled with anti-catalase antibodies and secondary AlexaFluor488 antibodies and 10nm protein A-gold.

Mathematical modeling of the input signals of oceanological lidars

Shipborne and airborne systems for remote laser probing of the ocean (oceanological lidars) are used today both for the bathymetry of near-shore water areas and for reconstructing the characteristics of the marine medium and the bottom from the data of lidar measurements. New applications of lidars have required an increase of the accuracy and reliability of mathematical models of lidar signals. The model proposed in this article for the back-scattering signal of a laser probe pulse from the thickness of sea water is based on the theory developed by Dolin, Levin et al. Unlike earlier results, the lidar equation obtained here takes into account possible deviation of the optical axis from the vertical and is applicable to the case of a lidar receiver with a narrow field of view.

Free-viewpoint images captured using phase-shifting synthetic aperture digital holography

Free-viewpoint images obtained from phase-shifting synthetic aperture digital holography are given for scenes that include multiple objects and a concave object. The synthetic aperture technique is used to enlarge the effective sensor size and to make it possible to widen the range of changing perspective in the numerical reconstruction. The lensless Fourier setup and its aliasing-free zone are used to avoid aliasing errors arising at the sensor edge and to overcome a common problem in digital holography, namely, a narrow field of view. A change of viewpoint is realized by a double numerical propagation and by clipping the wave field by a given pupil. The computational complexity for calculating an image in the given perspective from the base complex-valued image is estimated at a double fast Fourier transform. The experimental results illustrate the natural change of appearance in cases of both multiple objects and a concave object.

Statistical analysis of the ESA optical space debris surveys

In the framework of ESA's space debris research program optical measurements to search for space debris in high-altitude orbits are performed with the ESA 1-m telescope on Tenerife. Observations have been acquired during more than 500 nights during the past 6 years. Most of the data are ‘statistical’ in the sense that no catalogue of orbital data for individual objects is produced but only a list of ‘detections’ including rough orbital information and a visual magnitude for each of these detections. Moreover due to the narrow field of view of the telescope the optical surveys provide only snapshot-like samples of the space debris environment. There is no simple relation between the observed detection rates and the number of objects.In this paper we compare the ESA optical survey data from the year 2006 with simulated observations for different model populations, including the MASTER-2005 population. The simulations are performed with a software suite that links the ESA PROOF tool to our tools and takes into account the detailed observation scenarios and the details of the telescope and the camera system. A simulation using a geostationary (GEO) population with homogeneously distributed orbital elements is performed to analyze potential selection biases in the orbital element space of the observation scenarios. Of particular interest is the question if the observation scenarios may result in ‘artificial clusters’ in the observed distribution of the orbital planes. The simulation results for a GEO catalogue population are directly comparable with correlated detections and objects from the 2006 survey. The main results in this case are the percentage of detected objects with respect to the used catalogue and the coverage in the orbital element space. Finally the comparison of the observations with the results from simulations using the MASTER population represents an independent validation of the MASTER-2005 model. Using the results from the three mentioned simulations, we derive an estimate for the number of debris objects seen by the ESA 2006 surveys.

The Application of Biosignal Feedback for Reducing Cybersickness from Exposure to a Virtual Environment

We examined the efficacy of a new method to reduce cybersickness. A real-time cybersickness detection system was constructed with an artificial neural network whose inputs were the electrophysiological signals of subjects in a virtual environment. The system was equipped with a means of feedback; it temporarily provided a narrow field of view and a message about navigation speed deceleration, both of which acted as feedback outputs whenever electrophysiological inputs signaled the occurrence of cybersickness. This system is named cybersickness relief virtual environment (CRVE). Forty-seven subjects experienced the VR for 9.5 min twice in CRVE and non-CRVE conditions. The results indicated that the frequency of cybersickness and simulator sickness questionnaire scores were lower in the CRVE condition than in the non-CRVE condition. Subjects also showed a higher net increase in tachyarrhythmia from the baseline period to the virtual navigation period in the CRVE condition compared to the non-CRVE condition. These results suggest that a CRVE condition may be a countermeasure against cybersickness.

In-the-spectacle-lens telescopic device

Spectacle-mounted telescopic systems are prescribed for individuals with visual impairments. Bioptic telescopes are typically mounted toward the top of the spectacle lens (or above the frame) with the telescope eyepiece positioned above the wearer's pupil. This allows the wearer to use up and down head tilt movements to quickly alternate between the unmagnified wide view (through the carrier lens) and the magnified narrow field of view (available through the eyepiece). Rejection of this visual aid has been attributed mainly to its appearance and to the limited field of view through the smaller Galilean designs. We designed a wide-field Keplerian telescope that is built completely within the spectacle lens. The design uses embedded mirrors inside the carrier lens for optical pathway folding, and conventional lenses or curved mirrors for magnification power. The short height of the ocular, its position, and a small tilt of the ocular mirror enable the wearer to simultaneously view the magnified field above the unmagnified view of the uninterrupted horizontal field. These features improve the cosmetics and utility of the device. The in-the-lens design allows the telescope to be mass produced as a commodity ophthalmic lens blank that can be surfaced to include the wearer's spectacle prescription.

SLAM in Indoor Environments using Omni-directional Vertical and Horizontal Line Features

An autonomous mobile robot must have the ability to navigate in an unknown environment. The simultaneous localization and map building (SLAM) problem have relation to this autonomous ability. Vision sensors are attractive equipment for an autonomous mobile robot because they are information-rich and rarely have restrictions on various applications. However, many vision based SLAM methods using a general pin-hole camera suffer from variation in illumination and occlusion, because they mostly extract corner points for the feature map. Moreover, due to the narrow field of view of the pin-hole camera, they are not adequate for a high speed camera motion. To solve these problems, this paper presents a new SLAM method which uses vertical lines extracted from an omni-directional camera image and horizontal lines from the range sensor data. Due to the large field of view of the omni-directional camera, features remain in the image for enough time to estimate the pose of the robot and the features more accurately. Furthermore, since the proposed SLAM does not use corner points but the lines as the features, it reduces the effect of illumination and partial occlusion. Moreover, we use not only the lines at corners of wall but also many other vertical lines at doors, columns and the information panels on the wall which cannot be extracted by a range sensor. Finally, since we use the horizontal lines to estimate the positions of the vertical line features, we do not require any camera calibration. Experimental work based on MORIS, our mobile robot test bed, moving at a human's pace in the real indoor environment verifies the efficacy of this approach.

Approach for reconstructing anisoplanatic adaptive optics images

Atmospheric turbulence corrupts astronomical images formed by ground-based telescopes. Adaptive optics systems allow the effects of turbulence-induced aberrations to be reduced for a narrow field of view corresponding approximately to the isoplanatic angle theta(0). For field angles larger than theta(0), the point spread function (PSF) gradually degrades as the field angle increases. We present a technique to estimate the PSF of an adaptive optics telescope as function of the field angle, and use this information in a space-varying image reconstruction technique. Simulated anisoplanatic intensity images of a star field are reconstructed by means of a block-processing method using the predicted local PSF. Two methods for image recovery are used: matrix inversion with Tikhonov regularization, and the Lucy-Richardson algorithm. Image reconstruction results obtained using the space-varying predicted PSF are compared to space invariant deconvolution results obtained using the on-axis PSF. The anisoplanatic reconstruction technique using the predicted PSF provides a significant improvement of the mean squared error between the reconstructed image and the object compared to the deconvolution performed using the on-axis PSF.