Stereo Configuration Research Articles

A Comparative Analysis between Active and Passive Techniques for Underwater 3D Reconstruction of Close-Range Objects

In some application fields, such as underwater archaeology or marine biology, there is the need to collect three-dimensional, close-range data from objects that cannot be removed from their site. In particular, 3D imaging techniques are widely employed for close-range acquisitions in underwater environment. In this work we have compared in water two 3D imaging techniques based on active and passive approaches, respectively, and whole-field acquisition. The comparison is performed under poor visibility conditions, produced in the laboratory by suspending different quantities of clay in a water tank. For a fair comparison, a stereo configuration has been adopted for both the techniques, using the same setup, working distance, calibration, and objects. At the moment, the proposed setup is not suitable for real world applications, but it allowed us to conduct a preliminary analysis on the performances of the two techniques and to understand their capability to acquire 3D points in presence of turbidity. The performances have been evaluated in terms of accuracy and density of the acquired 3D points. Our results can be used as a reference for further comparisons in the analysis of other 3D techniques and algorithms.

Classification of High‐Activity Tiagabine Analogs by Binary QSAR Modeling

Classification of High‐Activity Tiagabine Analogs by Binary QSAR Modeling

Marker-Based Surgical Instrument Tracking Using Dual Kinect Sensors

This paper presents a passive-marker-based optical tracking system utilizing dual Kinect sensors and additional custom optical tracking components. To obtain sub-millimeter tracking accuracy, we introduce robust calibration of dual infrared sensors and point correspondence establishment in a stereo configuration. The 3D localization is subsequently accomplished using multiple back projection lines. The proposed system extends existing inexpensive consumer electronic devices, implements tracking algorithms, and shows the feasibility of applying the proposed low-cost system to surgical training for computer assisted surgeries.

Ultra-sensitive chemosensors for Fe(iii) and explosives based on highly fluorescent oligofluoranthene

Electron-rich oligofluoranthene has been successfully synthesized by a one-step direct chemical oxidative oligomerization of fluoranthene. Key advantages include easy synthesis, high synthetic yield and low cost when compared with electropolymerization. Oligofluoranthene in solution is a very strong cyan fluorescence emitter with 12.2 times higher intensity than the fluoranthene monomer. The strong fluorescence can be effectively quenched by specific electron-deficient species, enabling the fabrication of low-cost, high-performance chemosensors for the selective detection of Fe(III) ions and the explosive 2,4,6-trinitrophenol (picric acid). A concentration range of >9 orders of magnitude with exceedingly low detection limits down to 10−12 M is possible. No sample enrichment is needed likely due to the synergistic effects of well-distributed π-conjugated electrons with a conical stereo configuration that may enhance the detection ability. Common interferents appear to have little effect as Fe(III) can be selectively detected in both tap water and seawater containing many other metal ions and picric acid can be detected at low concentrations even in the presence of inorganic acids.

POTENTIAL OF DENSE MATCHING FOR THE GENERATION OF HIGH QUALITY DIGITAL ELEVATION MODELS

Abstract. Until recently, the acquisition of high quality Digital Elevation Models was dominated by the use of airborne LiDAR. However, the increasing quality of digital airborne cameras in combination with recent improvements in matching algorithms meanwhile allow for the automatic image based collection as a suitable alternative. Within the paper, these progresses will be demonstrated on the example of photogrammetric DEM generation using the Semi-Global Matching (SGM) stereo method. Since this approach aims at a pixel-wise matching, dense 3D point clouds can be generated. The tests described in the paper are based on data collected from different digital airborne cameras at various flight scenarios during a recent test on photogrammetric 3D data capture. By these means, the impact of different stereo configurations on the quality of the final outcome can be evaluated and compared to already available test results. Special interest is also paid to the analysis and combination of multiple stereo image pairs with different base- to-height ratios, which can be used efficiently to increase the accuracy and reliability of the matching result.

Surface maturation scoring for oesophageal squamous intraepithelial neoplasia: a novel diagnostic approach inspired by first endomicroscopic 3-dimensional reconstruction

ObjectiveLoss of surface maturation and cytonuclear atypia have been regarded as the pathological ‘gold standard’ for the diagnosis of oesophageal squamous cell intraepithelial neoplasia. However, there has been no satisfactory...

Opposite-side radargrammetry of Magellan synthetic aperture radar on Venus

In the early 1990s, synthetic aperture radar onboard Magellan spacecraft has imaged 54% of the Venusian surface in the opposite-side stereo configuration while only 21% in the same-side. Much of the data for the opposite-side radargrammetry (OSR) on Venus were underutilized due to higher topographic distortion than the same-side radargrammetry (SSR). In this paper, the performance and limitations of the OSR are demonstrated based on an example over Lullin impact crater, Venus. The initial stereo match points are classified into three categories; GOOD, BAD, and TOPO, and different methods are suggested for each category to improve the quality of digital elevation model. Large areas of gentle slope on Venusian volcanic plain can be successfully matched using conventional stereo-matching algorithm. Image contrast of featureless surface can be improved by enlarging the master image patch at a cost of spatial resolution, while high to moderate relief regions need further treatments such as radarclinometry. Utilization of OSR is expected to provide additional DEM dataset of Venus and to give flexibility for the design of future planetary SAR missions.

Miscibility of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) with high molecular weight poly(lactic acid) blends determined by thermal analysis

AbstractAn important strategy used in the polymer industry in recent years is blending two bio‐based polymers to attain desirable properties similar to traditional thermoplastics, thus increasing the application potential for bio‐based and bio‐degradable polymers. Miscibility of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) with poly(L‐lactic acid) (PLA) were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Three different grades of commercially available PLAs and one type of PHBV were blended in different ratios of 50/50, 60/40, 70/30, and 80/20 (PHBV/PLA) using a micro‐compounder at 175°C. The DSC and TGA analysis showed the blends were immiscible due to different stereo configuration of PLA polymer and two distinct melting temperatures. However, some compatibility between PHBV and PLA polymers was observed due to decreases in PLA's glass transition temperatures. Additionally, the blends do not show clear separation by SEM analysis, as observed in the thermal analysis. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Optimal pixel aspect ratio for enhanced 3D TV visualization

In multiview 3D TV, a pair of corresponding pixels in adjacent 2D views contributes to the reconstruction of voxels (3D pixels) in the 3D scene. We analyze this reconstruction process and determine the optimal pixel aspect ratio based on which the estimated object position can be improved given specific imaging or viewing configurations and constraints. By applying mathematical modeling, we deduce the optimal solutions for two general stereo configurations: parallel and with vergence. We theoretically show that for a given total resolution a finer horizontal resolution, compared to the usual uniform pixel distribution, in general, provides a better 3D visual experience for both configurations. The optimal value may vary depending on different configuration parameter values. We validate our theoretical results by conducting subjective studies using a set of simulated non-square discretized red–blue stereo pairs and show that human observers indeed have a better 3D viewing experience with an optimized vs. a non-optimized representation of 3D-models.

Assessment of Measuring Errors in Strain Fields Obtained via DIC on Planar Sheet Metal Specimens with a Non-Perpendicular Camera Alignment

The determination of strain fields based on displacement components obtained via 2D-DIC is subject to several errors that originate from various sources. In this contribution, we study the impact of a non-perpendicular camera alignment to a planar sheet metal specimen’s surface subject to biaxial loading conditions. The errors are estimated in a numerical experiment. To this purpose, deformed images - that were obtained by imposing finite element (FE) displacement fields on an undeformed image - are numerically rotated for various Euler angles. It is shown that a 3D-DIC stereo configuration induces a substantial compensation for the introduced image-plane displacement gradients. However, higher strain accuracy and precision are obtained - up to the level of a perfect perpendicular alignment - in a proposed ”rectified” 2D-DIC setup. This compensating technique gains benefit from both 2D-DIC (single camera view, basic amount of correlation runs, no cross-camera matching nor triangulation) and 3D-DIC (oblique angle compensation).

Multi-anode wire straw tube tracker

We report on a test of a straw tube detector design having several anode (sense) wires inside a straw tube. The anode wires form a circle inside the tube and are read out independently. This design could solve several shortcomings of the traditional single wire straw tube design such as double hit capability and stereo configuration.

Flavonoids from acai (Euterpe oleracea Mart.) pulp and their antioxidant and anti-inflammatory activities

Five flavonoids, (2S,3S)-dihyrokaempferol 3-O-β-d-glucoside (1) and its isomer (2R,3R)-dihydrokaempferol 3-O-β-d-glucoside (2) , isovitexin (3), velutin (4) and 5,4′-dihydroxy-7,3′,5′-trimethoxyflavone (5), were isolated from acai (Euterpe oleracea Mart.) pulp. The structures of these compounds were elucidated based upon spectroscopic and chemical analyses. To our knowledge, compounds 1, 2, 4 and 5 were identified from acai pulp for the first time. The in vitro antioxidant activities of these compounds were evaluated by the oxygen radial absorbance capacity (ORAC) assay. The ORAC values varied distinctly (4458.0–22404.5μmol Trolox equivalent (TE)/g) from 5,4′-dihydroxy-7,3′,5′-trimethoxyflavone (5) to isovitexin (3) and were affected by the numbers/positions of hydroxyl groups, substitute groups, as well as stereo configuration. The anti-inflammatory effects of these compounds were screened by the secreted embryonic alkaline phosphatase (SEAP) reporter assay, which is designed to measure NF-κB activation. Velutin (4) was found to dose-dependently inhibit SEAP secretion in RAW-blue cells induced by LPS, with an IC50 value of 2.0μM. Velutin (4) also inhibited SEAP secretion induced by oxidised LDL, indicating potential athero-protective effects.

Error estimation in measuring strain fields with DIC on planar sheet metal specimens with a non-perpendicular camera alignment

The determination of strain fields based on displacement components obtained via 2D-DIC is subject to several errors that originate from various sources. In this contribution, we study the impact of a non-perpendicular camera alignment to a planar sheet metal specimen's surface. The errors are estimated in a numerical experiment. To this purpose, deformed images – that were obtained by imposing finite element (FE) displacement fields on an undeformed image – are numerically rotated for various Euler angles. It is shown that a 3D-DIC stereo configuration induces a substantial compensation for the introduced image-plane displacement gradients. However, higher strain accuracy and precision are obtained – up to the level of a perfect perpendicular alignment – in a proposed “rectified” 2D-DIC setup. This compensating technique gains benefit from both 2D-DIC (single camera view, basic amount of correlation runs, no cross-camera matching nor triangulation) and 3D-DIC (oblique angle compensation). Our conclusions are validated in a real experiment on SS304.

Precise Subpixel Disparity Measurement From Very Narrow Baseline Stereo

To obtain depth-from-stereo imagery, it is traditionally required that the baseline separation between images (or the base-to-height ratio) be very large in order to ensure the largest image disparity range for effective measurement. Typically, a <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> / <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> ratio in the range of 0.6-1 is preferred. As a consequence, most existing stereo-matching algorithms are designed to measure disparities reliably with only integer-pixel precision. However, wide baselines may increase the possibility of occlusion occurring between highly contrasting relief, imposing a serious problem to digital elevation model (DEM) generation in urban and highly dissected mountainous areas. A narrow-baseline stereo configuration can alleviate the problem significantly but requires very precise measurements of disparity at subpixel levels. In this paper, we demonstrate a stereo-matching algorithm, based upon the robust <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">phase correlation</i> method, that is capable of directly measuring disparities up to 1/50th pixel accuracy and precision. The algorithm enables complete and dense surface shape information to be retrieved from images with unconventionally low <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> / <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> ratios (e.g., less than 0.01), potentially allowing DEM generation from images that would otherwise not be deemed suitable for the purpose.

Active Stereo Tracking of $N\le 3$ Targets Using Line Scan Cameras

This paper presents a general approach for the simultaneous tracking of multiple moving targets using a generic active stereo setup. The problem is formulated on the plane, where cameras are modeled as “line scan cameras,” and targets are described as points with unconstrained motion. We propose to control the active system parameters in such a manner that the images of the targets in the two views are related by a homography. This homography is specified during the design stage and, thus, can be used to implicitly encode the desired tracking behavior. Such formulation leads to an elegant geometric framework that enables a systematic and thorough analysis of the problem at hand. The benefits of the approach are illustrated by applying the framework to two distinct stereo configurations. In the first case, we assume two pan-tilt-zoom cameras, with rotation and zoom control, which are arbitrarily placed in the working environment. It is proved that such a stereo setup can track up to N = 3 free-moving targets, while assuring that the image location of each target is the same for both views. The second example considers a robot head with neck pan motion and independent eye rotation. For this case, it is shown that it is not possible to track more than N = 2 targets because of the lack of zoom. The theoretical framework is used to derive the control equations, and the implementation of the tracking behavior is described in detail. The correctness of the results is confirmed through simulations and real tracking experiments.

Anion recognition by d-ribose-based receptors

Anion recognition properties of d-ribose-based receptors α- and β-1 were measured by 1H NMR in CDCl3 and MeCN-d3. Receptor β-1 showed effective binding with anions by cooperative hydrogen bonds of cis-diol. The anomeric isomer α-1 is a less effective anion receptor which has similar cis-diol as a recognition site, indicating that the stereo configuration of the anomeric position is of significant influence on the anion recognition ability.

Experimental observation and computer simulation of conic markings on fracture surfaces of polymers

The morphology of conic markings was observed on the fracture surfaces of amorphous polysulfone, polyethersulfone and polyetherimide and semicrystalline polypropylene, polyphenylene sulfide and polybutylene terephthalate by using scanning electron microscopy. Most of conics exhibit the stepped stereo configuration, and the origin of secondary crack is depressed in the crack plane as a result of plastic deformation. The brittle–ductile transition of polymers can be analyzed by comparing the matching morphology of conic markings. According to computer simulations, the type I marking is determined by the ratio of the main to the secondary crack velocity while the type II marking is determined by the distances that two secondary cracks have covered before they meet. Variations of conic shapes can help to determine the changes of crack growth velocity.

Quasi multi‐baseline‐stereo method with single camera for reducing occlusion

AbstractA robust 3D image measurement method is proposed in order to suppress occlusion by a quasi multi‐baseline‐stereo method based on a single camera configuration. There is no way to suppress completely the “occlusion problem” in the field of stereo geometry. In order to deal with this problem, the multi‐baseline‐stereo configuration is often adopted and is basically effective. This paper proposes a new configuration for stereo measurement by means of a single camera, a mechanical feeder for the object, image processing for the baseline calibration, and in particular, diagonal feeding of the object in front of the camera. The concept of this method is to realize a pair of stereo geometries in the stereo configuration with a single camera and a mechanical feeder. It is technically noted that the baseline of this single camera stereo was precisely calibrated by an image processing procedure in both the horizontal and vertical directions. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 93(1): 41–49, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10156

A Novel Biosynthetic Pathway of Archaetidyl-myo-inositol via Archaetidyl-myo-inositol Phosphate from CDP-archaeol and d-Glucose 6-Phosphate in Methanoarchaeon Methanothermobacter thermautotrophicus Cells

Ether-type inositol phospholipids are ubiquitously distributed in Archaea membranes. The present paper describes a novel biosynthetic pathway of the archaeal inositol phospholipid. To study the biosynthesis of archaetidylinositol in vitro, we prepared two possible substrates: CDP-archaeol, which was chemically synthesized, and myo-[(14)C]inositol 1-phosphate, which was enzymatically prepared from [(14)C]glucose 6-phosphate with the inositol 1-phosphate (IP) synthase of this organism. The complete structure of the IP synthase reaction product was determined to be 1l-myo-inositol 1-phosphate, based on gas liquid chromatography with a chiral column. When the two substrates were incubated with the Methanothermobacter thermautotrophicus membrane fraction, archaetidylinositol phosphate (AIP) was formed along with a small amount of archaetidylinositol (AI). The two products were identified by fast atom bombardment-mass spectrometry and chemical analyses. AI was formed from AIP by incubation with the membrane fraction, but AIP was not formed from AI. This finding indicates that archaeal AI was synthesized from CDP-archaeol and d-glucose 6-phosphate via myo-inositol 1-phosphate and AIP. Although the relevant enzymes were not isolated, three enzymes are implied: IP synthase, AIP synthase, and AIP phosphatase. AIP synthase was homologous to yeast phosphatidylinositol synthase, and we confirmed AIP synthase activity by cloning the encoding gene (MTH1691) and expressing it in Escherichia coli. AIP synthase is a newly found member of the enzyme superfamily CDP-alcohol phosphatidyltransferase, which includes a wide range of enzymes that attach polar head groups to ester- and ether-type phospholipids of bacterial and archaeal origin. This is the first report of the biosynthesis of ether-type inositol phospholipids in Archaea.

X-ray structure analysis of lappaconitine

Lappaconitine is an important alkaloid of the aconite family and its biological activity is closely related to its structure. Through an X-ray structure analysis of hydrated lappaconitine hydrobromide, which was synthesised by us through a new method, the absolute configuration of lappaconitine was determined: monoclinic, P2 1 , a = 10.619(2) Å, b = 12.196(3) Å, c = 12.282(2) Å, β = 90.87(1)° and Z = 2; Flack parameter is −0.0083(0.0046) and S = 0.867. Rings A, B, C, D, E and F, respectively, present boat, chair, envelope, boat, boat and envelope forms. The absolute stereo configuration of lappaconitine was determined as 1S, 4S, 5S, 7S, 8S, 9S, 10S, 11S, 13R, 14S, 16S and 17R.