Wide Angle Camera System Research Articles

A Meteor Detection Algorithm for GWAC System

Compared with the international meteor surveillance systems, the ground wide angle camera (GWAC) system exhibits characteristics such as images with the resolution of 4K × 4K and single-site observation. These characteristics present challenges for meteor detection in the GWAC system. Consequently, this paper proposes a new meteor detection algorithm for the GWAC system on the base of the solely mini-GWAC system data algorithm. The new algorithm consists of the following key steps: (1) to compare differences between adjacent frames, applying block-based image binarization thresholds, and incorporating median filtering to reduce noise; (2) to adopt the probabilistic Hough transform (PHT) to identify moving objects and cluster them based on the origin moment of the line segments, while assessing the credibility of clustering; (3) to introduce the so-called maximum disappearance frame for moving objects in the tracking algorithm, enhancing the ability to track multi-frame moving objects. The utilization of the line segment inclination angle of the moving object as the direction of movement facilitates the tracking of multiple moving objects, thereby reducing the probability of mistakenly selecting single-frame moving objects; (4) to leverage the light curves of single-frame moving objects to select meteors to enhance the accuracy of meteor detection. Comparative experiments demonstrate that our proposed algorithm processes each frame image in just 0.39 s, achieving an accuracy of 89.8% in the dataset of 5856 adjacent frames. The experimental results indicate that the algorithm achieved an accuracy of 90.27% when applied in the meteor detection of the image data captured by the GWAC system from Dec. 10th to 19th in 2019 and 2021, obtaining excellent detection results.

Development of an eyeball integrated with a wide-angle lens camera and vision-sharing system for android avatars

Development of an eyeball integrated with a wide-angle lens camera and vision-sharing system for android avatars

Flaring-associated Complex Dynamics in Two M Dwarfs Revealed by Fast, Time-resolved Spectroscopy

Habitability of an exoplanet is believed to be profoundly affected by activities of the host stars, although the related coronal mass ejections (CMEs) are still rarely detected in solar-like and late-type stars. We here report an observational study on the flares of two M dwarfs triggered by the high-cadence survey performed by the Ground-based Wide Angle Camera system. In both events, the fast, time-resolved spectroscopy enables us to identify symmetric broad Hα emission with not only a nearly zero bulk velocity, but also a large projected maximum velocity as high as ∼700–800 km s−1. This broadening could be resulted from either the Stark (pressure) effect or a flaring-associated CME at the stellar limb. In the context of the CME scenario, the CME mass is estimated to be ∼4 × 1018 and 2 × 1019 g. In addition, our spectral analysis reveals a temporal variation of the line center of the narrow Hα emission in both events. The variation amplitudes are at tens of kilometers per second, which could be ascribed to the chromospheric evaporation in one event, and to a binary scenario in the other one. With the total flaring energy determined from our photometric monitor, we show a reinforced trend in which the larger the flaring energy, the higher the CME mass is.

Stray light analysis by ray tracing simulation for the wide-angle multiband camera OROCHI onboard the Martian Moons eXploration (MMX) spacecraft

• Ray tracing analysis was conducted to reduce stray light of OROCHI onboard the MMX. • OROCHI’s optical system is simulated and its CCD reflectance was measured. • Our techniques are incorporated into the preliminary design of OROCHI. The Martian Moons eXploration (MMX) spacecraft is equipped with two cameras, i.e., the TElescopic Nadir imager for GeOmOrphology (TENGOO) and the Optical Radiometer composed Of CHromatic Imagers (OROCHI), for the scientific observation of the Martian moon Phobos. OROCHI is a wide-angle multiband camera system comprising seven cameras with different bandpass filters and one monochromatic camera in the visible and near-infrared range. Thus, OROCHI can simultaneously obtain multiband images. Previous space observations have revealed that the reflection spectra of Phobos exhibit regional differences, including a red unit and a blue unit with weak redness. Moreover, Phobos shows an absorption band near 650 nm, attributed to the red unit of Phobos. Global observations using OROCHI require the determination of such regional variations with high precision; therefore, we must reduce noise in the optical system design. In this study, to meet this requirement, we focus on stray light reduction. Stray light is a source of noise generated by reflections at surfaces of optical components (e.g., sensors, filters, lenses, and lens barrels). We design simulation models of the OROCHI optical system, measure the reflectance of its charge-coupled device (CCD) image sensor, and conduct stray light analysis via ray tracing. We estimate the ratio of the stray light intensity to the target signal intensity by deriving both the reflected (constituting stray light) and unreflected rays. We show that placing the filter away from the sensor and reducing the reflectances of the filter and lenses effectively reduce stray light. Such approaches are incorporated into the preliminary design of OROCHI.

Obstacle avoidance for orchard vehicle trinocular vision system based on coupling of geometric constraint and virtual force field method

Nowadays the use of visual navigation in orchard is rapidly growing, while current research mainly focuses on orchard row detection or obstacle detection separately. The economic, fast and reliable navigation vision system that completing orchard row following and obstacle avoidance simultaneously and the obstacle avoidance algorithm for vision system without complex multiple navigation systems combining are needed further research. In this paper, a trinocular vision system for orchard vehicle is set up and the obstacle avoidance algorithm based on coupling of geometric constraint and virtual force field is designed for its vision system.First of all, based on analyzing the different vision system characteristics and the detection demand of orchard obstacle avoidance the trinocular vision system for orchard vehicle is set up based on a wide-angle camera and binocular stereo vision system. Then, the image processing algorithm of orchard row and obstacle detection is designed. For orchard row detection, the trunk regions enhancement algorithm is designed based on grayscale morphology filtering the trunk regions prediction algorithm is designed based on optical flow method to improve the trunk regions detection speed and accuracy. For obstacle detection, the background equalization algorithm based on H-channel image characteristics and the interference weaken algorithm with G-channel image characteristics are designed. Based on the row and obstacle detection results the algorithm for obstacle avoidance in orchard based on coupling of geometric constraint and virtual force field is designed. In the obstacle avoidance process, the virtual force field method is used as the mainly control of the vehicle obstacle avoidance process, and the geometric constraint between visual model of trinocular vision system and obstacle position is coupling with it to fulfill the avoidance demand of the obstacle with special shape and other condition that influence the virtual force field calculation.The experimental results show that the trinocular vision system for orchard vehicle built in this paper has strong adaptability to the actual environment which is accurate and stable for orchard row detection and obstacle detection simultaneously. The average deviation is 4.76 cm and 7.05 cm at 0.5 m/s and 1.0 m/s respectively, the average deviation of obstacle distance detection in the Z-axis direction is 3.18 cm, and in the X-axis direction is 0.45 cm. And the obstacle avoidance algorithm designed in this paper is effective in the orchard which can meet the actual production requirements. The research results will lay a foundation for the development of intelligent equipment and unmanned management in orchard.

Detection of Flare-associated CME Candidates on Two M-dwarfs by GWAC and Fast, Time-resolved Spectroscopic Follow-ups

Abstract The flare-associated stellar coronal mass ejections (CMEs) of solar-like and late-type stars profoundly impact the habitability of any expolanets in the systems. In this paper, we report the detection of flare-associated CMEs for two M-dwarfs, thanks to a high-cadence survey carried out by the Ground Wide-angle Camera system and fast photometric and spectroscopic follow-ups. The flare energies in the R band are determined to be 1.6 × 1035 erg and 8.1 × 1033 erg based on modeling of their light curves. The time-resolved spectroscopic observations start at about 20 and 40 minutes after the trigger in both cases. The large projected maximum velocity of ∼500–700 km s−1 suggests that the high-velocity wings of their Hα emission lines most likely result from CME events in both stars, after excluding the possibility of chromospheric evaporation and coronal rain. The masses of the CMEs are estimated to be 1.5–4.5 × 1019 g and 7.1 × 1018 g.

The mini-GWAC optical follow-up of gravitational wave alerts – results from the O2 campaign and prospects for the upcoming O3 run

The second (O2) observational campaign of gravitational waves (GWs) organized by the LIGO/Virgo Collaborations has led to several breakthroughs such as the detection of GW signals from merger systems involving black holes or neutrons stars. During O2, 14 GW alerts were sent to the astronomical community with sky regions mostly covering over hundreds of square degrees. Among them, six were finally confirmed as real astrophysical events. Since 2013, a new set of ground-based robotic telescopes called Ground-based Wide Angle Camera system (GWAC) project and its pathfinder mini-GWAC has been developed to contribute to the various challenges of multi-messenger and time domain astronomy. The GWAC system is built up in the framework of the ground-segment system of the SVOM mission that will be devoted to the study of the multi-wavelength transient sky in the next decade. During O2, only the mini-GWAC telescope network was fully operational. Due to the wide field of view and fast automatic follow-up capabilities of the mini-GWAC telescopes, they were adept to efficiently cover the sky localization areas of GW event candidates. In this paper, we present the mini-GWAC pipeline we have set up to respond to GW alerts and we report our optical follow-up observations of eight GW alerts detected during the O2 run. Our observations provided the largest coverage of the GW localization areas with a short latency made by any optical facility. We found tens of optical transient candidates in our images, but none of those could be securely associated with any confirmed black hole – black hole merger event. Based on this first experience and the near future technical improvements of our network system, we will be more competitive in detecting the optical counterparts from some GW events that will be identified during the upcoming O3 run, especially those emerging from binary neutron star mergers.

MODELLING WIDE-ANGLE LENS CAMERAS FOR METROLOGY AND MAPPING APPLICATIONS

Abstract. Wide-angle lenses typically offer fields of view greater than 70°, which are utilized in a variety of imaging, mapping, and navigation applications. Wide-angle lenses are commonly modelled using the central perspective model, compensating for lens distortions through a series of additional parameters. The more extreme the distortions, the further the reality of the lens matches the collinearity equations that define the central perspective model. Fisheye lenses are modelled differently because their fields of view are so wide (typically 180°) that the collinearity model is not applicable. This work studied the effects of modelling wide-angle lenses using both the conventional central perspective model and the fisheye model to determine which model best fits the observations and models the distortions more precisely and accurately. These results were produced by generating observations in a dedicated indoor calibration facility at the University of Calgary: an 11 m × 11 m × 4 m field comprising 291 signalized photogrammetry targets. Multiple free-network, self-calibrating bundle adjustments were performed using different models and different cameras. The results of the self-calibrating bundle adjustments were then utilized in a check adjustment on independent sets of check images to validate their accuracy. Two cameras, a Ladybug5 and a GoPro Hero5, were tested. The GoPro was also calibrated using a checkerboard target pattern, and the results were compared to those of the 3D calibration target-field. The results of the bundle adjustments determined that the fisheye model describes the distortions more precisely in both wide-angle camera systems.

Calibration, Projection, and Final Image Products of MESSENGER’s Mercury Dual Imaging System

We present an overview of the operations, calibration, geodetic control, photometric standardization, and processing of images from the Mercury Dual Imaging System (MDIS) acquired during the orbital phase of the MESSENGER spacecraft’s mission at Mercury (18 March 2011–30 April 2015). We also provide a summary of all of the MDIS products that are available in NASA’s Planetary Data System (PDS). Updates to the radiometric calibration included slight modification of the frame-transfer smear correction, updates to the flat fields of some wide-angle camera (WAC) filters, a new model for the temperature dependence of narrow-angle camera (NAC) and WAC sensitivity, and an empirical correction for temporal changes in WAC responsivity. Further, efforts to characterize scattered light in the WAC system are described, along with a mosaic-dependent correction for scattered light that was derived for two regional mosaics. Updates to the geometric calibration focused on the focal lengths and distortions of the NAC and all WAC filters, NAC–WAC alignment, and calibration of the MDIS pivot angle and base. Additionally, two control networks were derived so that the majority of MDIS images can be co-registered with sub-pixel accuracy; the larger of the two control networks was also used to create a global digital elevation model. Finally, we describe the image processing and photometric standardization parameters used in the creation of the MDIS advanced products in the PDS, which include seven large-scale mosaics, numerous targeted local mosaics, and a set of digital elevation models ranging in scale from local to global.

An optical laser device for mapping 3D geometry of underwater karst structures: first tests in the Ox Bel’Ha system, Yucatan, Mexico

In the course of extended hydrological studies in the coastal Karst plain of Yucatan, near the town of Tulum amongst others, a novel laser scanning device was developed and applied for the acquisition of the 3d-geometry of groundwater conduits. The method is derived from similar industrial systems and for the first time adapted to the specific measurement conditions in underwater cave systems. The device projects a laser line over the whole perimeter at a certain position. This line represents the intersection of a plane with the cave walls. The line is imaged with a wide angle camera system. Through proper design and calibration of the device it is possible to derive the true scale geometry of the perimeter via special image processing techniques. By acquiring regularly spaced images it is possible to reconstruct the true scale and 3d-shape of a tunnel through the incorporation of location and attitude data. In a first test in the Ox Bel Ha underwater cave system, about 800 metres of tunnels have been scanned down to water depths of 20 metres. The raw data is further interpolated using the ODSIM-algorithm in order to delineate the 3D geometry of the cave system. The method provides easy, operable acquisition of the 3-D geometry of caves in clear water with superior resolution and speed and significantly facilitates the measurement in underwater tunnels as well as in dry tunnels. The data gathered represents crucial input to the study of the state, dynamics and genesis of the complex karst water regime.

Optical Coatings as Mirrors for Optical Diagnostics

The aim of this work was to provide a comprehensive insight concerning coated films which might be used for first mirrors in ITER. The influence of the mirror crystallite size has been addressed as well as the coating techniques to provide nanocrystalline films. Tests of coated mirrors both in laboratories and in tokamaks are reviewed. For the tokamak tests a wide angle camera system has been installed in JET-ILW which is composed of a mirror box with 3 stainless steel mirrors coated with rhodium viewing the torus through a conically shaped aperture. The system delivered the required image quality for plasma monitoring and wall protection. No or insignificant degradation of the optical transmittance has been observed during the experimental campaign in 2014 with about 3000 plasma pulses in different magnetic field configurations.

Inflight Calibration of the Lunar Reconnaissance Orbiter Camera Wide Angle Camera

The Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC) has acquired more than 250,000 images of the illuminated lunar surface and over 190,000 observations of space and non-illuminated Moon since 1 January 2010. These images, along with images from the Narrow Angle Camera (NAC) and other Lunar Reconnaissance Orbiter instrument datasets are enabling new discoveries about the morphology, composition, and geologic/geochemical evolution of the Moon. Characterizing the inflight WAC system performance is crucial to scientific and exploration results. Pre-launch calibration of the WAC provided a baseline characterization that was critical for early targeting and analysis. Here we present an analysis of WAC performance from the inflight data. In the course of our analysis we compare and contrast with the pre-launch performance wherever possible and quantify the uncertainty related to various components of the calibration process. We document the absolute and relative radiometric calibration, point spread function, and scattered light sources and provide estimates of sources of uncertainty for spectral reflectance measurements of the Moon across a range of imaging conditions.

CALIBRATION AND EPIPOLAR GEOMETRY OF GENERIC HETEROGENOUS CAMERA SYSTEMS

Abstract. The application of perspective camera systems in photogrammetry and computer vision is state of the art. In recent years nonperspective and especially omnidirectional camera systems were increasingly used in close-range photogrammetry tasks. In general perspective camera model, i. e. pinhole model, cannot be applied when using non-perspective camera systems. However, several camera models for different omnidirectional camera systems are proposed in literature. Using different types of cameras in a heterogeneous camera system may lead to an advantageous combination. The advantages of different camera systems, e. g. field of view and resolution, result in a new enhanced camera system. If these different kinds of cameras can be modeled, using a unified camera model, the total calibration process can be simplified. Sometimes it is not possible to give the specific camera model in advance. In these cases a generic approach is helpful. Furthermore, a simple stereo reconstruction becomes possible using a fisheye and a perspective camera for example. In this paper camera models for perspective, wide-angle and omnidirectional camera systems are evaluated. The crucial initialization of the model’s parameters is conducted using a generic method that is independent of the particular camera system. The accuracy of this generic camera calibration approach is evaluated by calibration of a dozen of real camera systems. It will be shown, that a unified method of modeling, parameter approximation and calibration of interior and exterior orientation can be applied to derive 3D object data.

Imaging and modeling the ionospheric airglow response over Hawaii to the tsunami generated by the Tohoku earthquake of 11 March 2011

[1] Although only centimeters in amplitude over the open ocean, tsunamis can generate appreciable wave amplitudes in the upper atmosphere, including the naturally occurring chemiluminescent airglow layers, due to the exponential decrease in density with altitude. Here, we present the first observation of the airglow tsunami signature, resulting from the 11 March 2011 Tohoku earthquake off the eastern coast of Japan. These images are taken using a wide-angle camera system located at the top of the Haleakala Volcano on Maui, Hawaii. They are correlated with GPS measurements of the total electron content from Hawaii GPS stations and the Jason-1 satellite. We find waves propagating in the airglow layer from the direction of the earthquake epicenter with a velocity that matches that of the ocean tsunami. The first ionospheric signature precedes the modeled ocean tsunami generated by the main shock by approximately one hour. These results demonstrate the utility of monitoring the Earth's airglow layers for tsunami detection and early warning.

Wide-angle camera technology for automotive applications: a review

The development of electronic vision systems for the automotive market is a strongly growing field, driven in particular by customer demand to increase the safety of vehicles both for drivers and for other road users, including vulnerable road users (VRUs), such as pedestrians. Customer demand is matched by legislative developments in a number of key automotive markets; for example Europe, Japan and the US are in the process of introducing legislation to aid in the prevention of fatalities to VRUs, with emphasis on the use of vision systems. The authors discuss some of the factors that motivate the use of wide-angle and fish-eye camera technologies in vehicles. The authors describe the benefits of using wide-angle lens camera systems to display areas of a vehicle's surroundings that the driver would, otherwise, be unaware of (i.e. a vehicle's blind-zones). However, although wide- angle optics provide greater fields of view, they also introduce undesirable effects, such as radial distortion, tangential distortion and uneven illumination. These distortions have the potential to make objects difficult for the vehicle driver to recognise and, thus, potentially have a greater risk of accident. The authors describe some of the methods that can be employed to remove these unwanted effects, and digitally convert the distorted image to the ideal and intuitive rectilinear pin-hole model.

Towards automatic near real-time traffic monitoring with an airborne wide angle camera system

Abstract Purpose Large area traffic monitoring with high spatial and temporal resolution is a challenge that cannot be served by today available static infrastructure. Therefore, we present an automatic near real-time traffic monitoring approach using data of an airborne digital camera system with a frame rate of up to 3 fps. Methods By performing direct georeferencing on the obtained aerial images with the use of GPS/IMU data we are able to conduct near real-time traffic data extraction. The traffic processor consists mainly of three steps which are road extraction supported by a priori knowledge of road axes obtained from a road database, vehicle detection by edge extraction, and vehicle tracking based on normalized cross correlation. Results Traffic data is obtained with a correctness of up to 79% at a completeness of 68%. Conclusions With this system we are able to perform area-wide traffic monitoring with high actuality independent from any stationed infrastructure which makes the system well suited for deployments on demand in case of disasters and mass events.

Panoramic imaging of the ocular fundus.

There are several camera systems available to the ophthalmologist for documenting fundus conditions. We present our results of imaging with a new wide-angle contact camera system, Panoret-1000 (CMT Medical Technologies Inc, Valley Stream, NY). This digital camera provides high-resolution, wide-field imaging of the ocular fundus. Special features include its portability, digital capture, realistic color match, excellent resolution, and lack of distortion. It has the capability of imaging through the relatively small pupil, mild cataract, and pseudophakic intraocular lens, features that hinder other wide-angle camera systems. Imaging of the ocular fundus is important for the documentation of numerous retinal and choroidal conditions. However, fundus photography can be a challenge owing to the small pupillary aperture,whichinhibitsadequateillumination of the interior of the eye. There are currently several fundus imaging systems available, all of which use transpupillary illumination techniques, where the light source is located in the region of the camera and is directed through the pupil into theposteriorsegmentoftheeye.Thesesystems generally provide small-angle, highresolution photography of the posterior pole, measuring approximately 26°, 45°, 65°,and80°oftheposteriorsegment(measured from the center of the vitreous cavity).Photographingthefundusanteriorto the equator of the eye is particularly difficult with small-angle photography systems. Additionally, imaging of large fundus abnormalities is in adequate with the small-anglesystems,astheabnormalityis documented in a piecemeal fashion without the desired broad perspective of the entire lesion. Some of the currently available wide-angle systems include Retcam 120 (Massie Research Laboratories, Dublin,Calif),acontactsystemusingtranspupillary illumination, and Optomap (Optos, Marlborough, Mass), a noncontact system using transpupillary illumination. Retcam120canprovidehigh-resolutionim

A photogrammetric equipment for archeological survey

In close cooperation with architectural circles, Carl Zeiss Oberkochen has developed a special photogrammetric equipment system, which satisfies also the needs of archeologists to a high degree: wide-angle stereometric camera systems with a fixed base for taking photographs from subjects 2.5–40 m far, single cameras with a focal length of 60 mm and 120 mm, and a variable base for long camera-to-subject distances; inclinable camera axis between 0 g and ± 100 g ; extreme close-up range photography by means of short-focus lenses. Plotting in case of three-dimensional objects is done with a stereoplotter; if there is no pronounced relief, one can use a simple rectifier.