Stereo Projection Research Articles

Hybrid-feature based spherical quasi-conformal registration for AD-induced hippocampal surface morphological changes

Background and objectiveEstablishing accurate one-to-one morphological correspondence between different hippocampal surfaces is a solid foundation for the analysis of AD-induced hippocampal morphological changes. However, owing to the large variations between hippocampal surfaces, exiting registration work either fails to obtain the accurate matching of local and overall morphological features or does not preserve the bijectivity during parametric mapping. For this reason, this study proposes a hybrid-feature based spherical quasi-conformal registration (HSQR) method that can effectively maintain the diffeomorphic property while meeting the hybrid-feature matching constraints in the spherical parameter domain. MethodsThe HSQR algorithm is primarily achieved through hippocampal surface hybrid feature extraction and spherical quasi-conformal registration. First, hybrid features for a comprehensive morphological description of the hippocampal surface were established, which included essential anatomical features (landmarks) and mean curvature (intensity) features to ensure the accuracy of surface morphology alignment. Second, spherical parameterization was applied to genus-0 closed surfaces, such as the hippocampus, which maximized the preservation of the original local surface morphology through area-preserving properties. Third, a novel spherical quasi-conformal registration algorithm that can handle large deformations is established. It transforms a 3D spherical parameter domain into a 2D plane parameter domain using iterative local stereo projection to improve the efficiency of the registration algorithm. Subsequently, by controlling the Beltramin coefficient, the hybrid morphological features could be aligned while ensuring bijection before and after registration. ResultsUsing a cohort including 161 patients with amyloid-β (Aβ) positive Alzheimer disease (AD), 234 Aβ positive mild cognitive impairment (MCI) and 266 Aβ negative cognitively unimpaired (CU) individuals from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database, we set up the experiment which indicated that the HSQR-based whole bilateral hippocampal atrophy features demonstrated the stronger statistical power for group morphological differences of CU vs. MCI with q-value: 0.0453 for left hippocampus and 0.0401 for right hippocampus and group morphological differences of AD vs. MCI with q-value: 0.0282 for left hippocampus and 0.0421 for right hippocampus. ConclusionsOur registration algorithm may provide a solid foundation for the accurate quantification of hippocampal surface morphological changes for the differential diagnosis and tracking of AD.

Propagation of uncertainty for an epipole-dependent model for convergent stereovision structure computation

An analytic model incorporating stereo epipoles is proposed for structure computation using a convergent stereovision setup. The developed model is predicated on the image parameters of both CCD camera sensors, together with two extrinsic parameters, namely the stereo baseline distance and the stereo projection angle of the scene point of interest. In the model, the points on the image planes are measured relative to the principal points, stereo epipoles are featured, and only focal length-normalized camera sensor coordinates are required for structure computation. The reconstruction model could be employed in active vision-based metrology in which the stereo imaging cameras are systematically rotated about their vertical axes relative to each other. The performance of the model is studied, and its accuracy tested by comparing the 3-space coordinates it predicted to the those obtained by a gold standard triangulation and to the ground truth results. In terms of execution speed the proposed reconstruction model exhibited a computation time of 0.6 ms compared to 6.2 ms and 9.9 ms recorded for the direct linear transformation and gold standard triangulation algorithms respectively. The coordinate measurement uncertainties determined by experimental methods are subsequently compared with those obtained by a theoretical approach based on the analytic reconstruction model. Strong correlations were found to exist between the two sets of uncertainty values obtained.

On the Application of Stereoscopic Technologies in Biological Research

The work is devoted to the application of previously developed algorithms and methods of stereo animations construction in the field of biological research on the example of stereo images for functional tomogram of the brain. The construction of stereo images on the autostereoscopic monitor provides an opportunity to obtain an in-depth understanding of the studied object. The autostereoscopic monitor allows viewing stereo images without glasses, while providing a quality not inferior to that of a classical 3D projection stereo system. This work continues the cycle of research conducted at the Keldysh Institute of Applied Mathematics. The specificity of the displayed data allowed to improve authoring libraries for creating stereo images. The research is aimed at developing technologies for constructing stereo images and animations for presenting the results of scientific calculations on classical stereo devices and autostereoscopic monitors. Constructing a stereoscopic visual representation of the results of biological research will enable researchers in the field to gain a deeper understanding of the object under study and its properties.

Enhancing students' understanding of cardiac physiology by using 4D visualization.

Difficulties in achieving knowledge about physiology and anatomy of the beating heart highlight the challenges with more traditional pedagogical methods. Recent research regarding anatomy education has mainly focused on digital three-dimensional models. However, these pedagogical improvements may not be entirely applicable to cardiac anatomy and physiology due to the multidimensional complexity with moving anatomy and complex blood flow. The aim of this study was therefore to evaluate whether high quality time-resolved anatomical images combined with realistic blood flow simulations improve the understanding of cardiac structures and function. Three time-resolved datasets were acquired using time-resolved computed tomography and blood flow was computed using Computational Fluid Dynamics. The anatomical and blood flow information was combined and interactively visualized using volume rendering on an advanced stereo projection system. The setup was tested in interactive lectures for medical students. Ninety-seven students participated. Summative assessment of examinations showed significantly improved mean score (18.1 ± 4.5 vs 20.3 ± 4.9, p=0.002). This improvement was driven by knowledge regarding myocardial hypertrophy and pressure-velocity differences over a stenotic valve. Additionally, a supplementary formative assessment showed significantly more agreeing answers than disagreeing answers (p < 0.001) when the participants subjectively evaluated the contribution of the visualizations to their education and knowledge. In conclusion, the use of simultaneous visualization of time-resolved anatomy data and simulated blood flow improved medical students' results, with a particular effect on understanding of cardiac physiology and these simulations may be useful educational tools for teaching complex anatomical and physiological concepts.

Dynparity: Dynamic disparity adjustment to avoid stereo window violations on stationary stereoscopic displays

AbstractWe propose a novel method to avoid stereo window violations at screen borders. These occur for objects in front of the zero parallax plane, which appear in front of the (physical) screen, and that are clipped for one eye while still being visible for the other eye. This contradicts other stereo cues, particularly disparity, potentially resulting in eye strain and simulator sickness. In interactive and dynamic virtual environments, where the user controls the camera, for example, via head tracking, it is impossible to avoid stereo window violations completely. We propose Dynparity, a novel rendering method to eliminate the conflict between clipping and negative disparity, by introducing a nonuniform stereoscopic projection. For each vertex in front of the zero parallax plane, we compute the stereoscopic projection such that the parallax approaches zero toward the edge of the screen. Our approach works entirely on the GPU in real‐time and can be easily included in modern game engines. We conducted a user study comparing our method to the standard stereo projection on a large‐screen stereo wall with head tracking. Our results show significantly reduced simulator sickness when using Dynparity compared to the standard stereo rendering.

Constructing Stereo Images of Error Surfaces in Problems of Numerical Methods Verification

The tasks of constructing stereo representations of texts and formulas on an autostereoscopic monitor in stereo presentations designed to display the results of numerical modeling are an urgent sub-task in developing methods and algorithms for constructing stereo displays of scientific research results. In this paper, the construction of stereo images on an autostereoscopic monitor is considered. The autostereoscopic monitor allows you to watch stereo images without glasses, while ensuring the quality of the stereo image, which is not inferior to the quality of the stereo image presented using the classic 3D projection stereo system. The possibility of combining several stereo objects with different parameters on one frame with various parameters allowing to achieve the maximum stereo effect is being investigated. This technology has been applied practically to visualize the problems of verification of numerical methods and their comparative analysis. Similar solutions for the two-parameter problem are represented in the form of error surfaces constructed for each numerical method involved in the comparison. The construction of error surfaces in stereo mode is implemented for an autostereoscopic monitor based on a multi-view.

Feature Detection of Focused Plenoptic Camera Based on Central Projection Stereo Focal Stack

Fast and accurate feature extraction can lay a solid foundation for scene reconstruction and visual odometry. However, this has been rather a difficult problem for the focused plenoptic camera. In this paper, to the best of our knowledge, we first introduce an accurate and fast feature extraction algorithm based on central projection stereo focal stack (CPSFS). Specifically, we propose a refocusing algorithm that conforms to the central projection with regard to the center of main lens, which is more accurate than traditional one. On this basis, the feature is extracted on the CPSFS without calculating dense depth maps and total focus images. We verify the precision and efficiency of the proposed algorithm through simulated and real experiments, and give an example of scene reconstruction based on the proposed method. The experimental results show that our feature extraction algorithm is able to support the feature-based scene reconstruction via focused plenoptic camera.

?omparative Analysis of Human Kidney Venous Vessels at Various Method of Radiation Research

The aim of the study was to conduct a comparative assessment of the spatial characteristics of the kidneyveins in a planar projection, in stereo projection, and according to the results of computed tomography after3D modeling. To compare and identify the truth of the morphometric parameters of the renal veins, as wellas the options for their formation during x-ray and computed tomography, 136 corrosive preparations of thekidney veins were made, which were taken as a control group. To identify the degree of similarity of the renalveins parameters on corrosion preparations, X-ray diffraction patterns (2D) and on computed tomograms(CT) with a helix pitch of 1.0 and 2.5 mm after 3D modeling, a comparative assessment of the obtainedparameters was performed (degree of the angle similarity - simPhi; the degree of length similarity is simLen;and the general degree of similarity is sim). It was revealed that the greatest degree of parameters similaritywas found between corrosive preparations and computed tomograms of kidney veins with a spiral pitch of1.0 mm, which was 98.0%. Studies have shown that the informational content of x-ray examination of thekidneys’ veins depends on the options for the formation and location of blood vessels in the gates of thekidney relative to the frontal, horizontal and sagittal planes. The informativeness of computed tomographystudies does not depend on the options for the formation of renal veins, it determines the step of the spiral

A Comparison of Contemporary Prototyping Methods

AbstractPrototypes are a common feature of many product design and development endeavours. An ever widening range of prototyping options are available to designers and engineers. May particular options be superior to others, or more appropriate for particular endeavours? This paper reviews current literature on the nature of what constitutes a prototype and the benefits they offer to the discipline. They principally facilitate communication, aid learning, help gain and provide feedback, inform decision making and generally provide superior design outcomes. In order to determine if any particular manner of prototype is preferable for achieving these benefits a comparative study of some of the contemporary prototyping methods is subsequently conducted: A 3D printed prototype (physical prototype), a CAD prototype (represented using a computer monitor), an augmented reality prototype (represented using a tablet device) and a virtual reality prototype (represented using a stereo projector and polarised glasses). The results indicate that while all provide benefits, overall the physical prototype performs best and the augmented reality prototype performs most poorly.

Edge Fusion Algorithm for Orthogonal Projection of Multiple Overlapping Regions

Stereo projection display technology has become a hot topic in recent years. A edge fusion technology for multiple projection images with multiple overlapping areas is proposed. An edge fusion method is proposed, which can be used for edge fusion of multiple overlapping areas in irregular fusion areas, eliminate the bright band caused by overlapping projection and realize multi-channel seamless Mosaic display. The practical application shows that this method can make the multi-projector display system with multiple planar and different shape and multiple overlapping areas project a seamless vision.

Development of a dynamic surface shape measurement for magnetic fluid

Traditional measurement techniques such as fringe and stereo projection can hardly measure the black surface shape of magnetic liquid in revolving container which has a cover to prevent the liquid spilling out. To solve this problem, a multi-step measurement method based on linear laser projection is proposed. Modulated laser by synchronous revolving chopper is introduced to obtain the steady projection light curve on the measured location of the magnetic fluid surface. In order to capture the instantaneous reflected light of the projection light curve, a camera used a long exposure time of shooting is used. Taking the advantages of multiple exposure luminance enhancement effect of long exposure time, pictures with high brightness and contrast projection light are obtained. The overall surface shape of the fluid can be reconstructed by many laser projection lines extracted from the pictures captured at different angles of revolving container. A high transparency acrylic cover is adopted to provide good sealing performance and light transmission quality in the experiment. On the base of correction of influence of refractive index of the acrylic cover, the height formula of magnetic fluid surface is derived. The camera installation angle and distance between the camera and the container are not required as the size of container are utilized to calibrate the camera. The relationship between image coordinates and world coordinates is also obtained. According to the height curves of the projection lines and their measuring angles on the container, 3-D surface shape of magnetic fluid is reconstructed. The surface shape is verified indirectly by using the imbalance of the container, and the relative unbalance errors between the measurement results and the results by Shenk dynamic balancing machine under different conditions are between 0.8% and 11%. Another performance experiment on measuring the surface shape of an rubber block indicates that the measurement range of the proposed method is that the slope of the measured surface must be less than 3.94, and the sensitivity is 0.18 mm. All performance of the proposed method is acceptable, so such a complex industrial problem is solved only by a daily digital camera.

Microscopic Three-Dimensional Measurement Based on Telecentric Stereo and Speckle Projection Methods.

Three-dimensional (3D) measurement of microstructures has become increasingly important, and many microscopic measurement methods have been developed. For the dimension in several millimeters together with the accuracy at sub-pixel or sub-micron level, there is almost no effective measurement method now. Here we present a method combining the microscopic stereo measurement with the digital speckle projection. A microscopy experimental setup mainly composed of two telecentric cameras and an industrial projection module is established and a telecentric binocular stereo reconstruction procedure is carried out. The measurement accuracy has firstly been verified by performing 3D measurements of grid arrays at different locations and cylinder arrays with different height differences. Then two Mitutoyo step masters have been used for further verification. The experimental results show that the proposed method can obtain 3D information of the microstructure with a sub-pixel and even sub-micron measuring accuracy in millimeter scale.

Tracking a Non-Cooperative Target Using Real-Time Stereovision-Based Control: An Experimental Study.

Tracking a non-cooperative target is a challenge, because in unfamiliar environments most targets are unknown and unspecified. Stereovision is suited to deal with this issue, because it allows to passively scan large areas and estimate the relative position, velocity and shape of objects. This research is an experimental effort aimed at developing, implementing and evaluating a real-time non-cooperative target tracking methods using stereovision measurements only. A computer-vision feature detection and matching algorithm was developed in order to identify and locate the target in the captured images. Three different filters were designed for estimating the relative position and velocity, and their performance was compared. A line-of-sight control algorithm was used for the purpose of keeping the target within the field-of-view. Extensive analytical and numerical investigations were conducted on the multi-view stereo projection equations and their solutions, which were used to initialize the different filters. This research shows, using an experimental and numerical evaluation, the benefits of using the unscented Kalman filter and the total least squares technique in the stereovision-based tracking problem. These findings offer a general and more accurate method for solving the static and dynamic stereovision triangulation problems and the concomitant line-of-sight control.

An HTML Tool for Production of Interactive Stereoscopic Compositions.

The benefits of stereoscopic vision in medical applications were appreciated and have been thoroughly studied for more than a century. The usage of the stereoscopic displays has a proven positive impact on performance in various medical tasks. At the same time the market of 3D-enabled technologies is blooming. New high resolution stereo cameras, TVs, projectors, monitors, and head mounted displays become available. This equipment, completed with a corresponding application program interface (API), could be relatively easy implemented in a system. Such complexes could open new possibilities for medical applications exploiting the stereoscopic depth. This work proposes a tool for production of interactive stereoscopic graphical user interfaces, which could represent a software layer for web-based medical systems facilitating the stereoscopic effect. Further the tool's operation mode and the results of the conducted subjective and objective performance tests will be exposed.

Dislocation characterization in fatigued Cu with nanoscale twins

Previous studies have shown that strain-controlled cyclic stability was maintained in bulk Cu samples with highly oriented nanoscale twins. In order to explore the underlying fatigue mechanism, transmission electron microscopy observations under two-beam diffraction condition were utilized to characterize the dislocation configurations in the twin/matrix layers of as-fatigued nanotwinned Cu. It was clarified that the threading dislocations with Burgers vector parallel to twin boundaries are mainly active during fatigue. A three-dimensional stereo projection was re-configured for demonstrating the special structure of dislocations in nanoscale twins.

3-D imaging of islets in obesity: formation of the islet-duct complex and neurovascular remodeling in young hyperphagic mice.

Obesity and insulin resistance lead to islet hyperplasia. However, how the islet remodeling influences the pancreatic environment and the associated neurovascular networks is largely unknown. The lack of information is primarily due to the difficulty of global visualization of the hyperplasic islet (>200 μm) and the neurovascular environment with high definition. We modulated the pancreatic optical property to achieve 3-dimensional (3-D) whole-islet histology and to integrate transmitted light microscopy (which provides the ground-truth tissue information) with confocal fluorescence imaging. The new optical and imaging conditions were used to globally examine the hyperplastic islets of the young (2 months) obese db/db and ob/ob mice, which otherwise cannot be easily portrayed by the standard microtome-based histology. The voxel-based islet micrographs were digitally processed for stereo projection and qualitative and quantitative analyses of the islet tissue networks. Paired staining and imaging of the pancreatic islets, ducts and neurovascular networks reveal the unexpected formation of the 'neuro-insular-ductal complex' in the young obese mice. The complex consists of the peri- and/or intra-islet ducts and prominent peri-ductal sympathetic nerves; the latter contributes to a marked increase in islet sympathetic innervation. In vascular characterization, we identify a decreased perivascular density of the ob/ob islet pericytes, which adapt to ensheathing the dilated microvessels with hypertrophic processes. Modulation of pancreatic optical property enables 3-D panoramic examination of islets in the young hyperphagic mice to reveal the formation of the islet-duct complex and neurovascular remodeling. On the basis of the morphological proximity of the remodeled tissue networks, we propose a reactive islet microenvironment consisting of the endocrine cells, ductal epithelium and neurovascular tissues in response to the metabolic challenge that is experienced early in life.

Needle guidance using handheld stereo vision and projection for ultrasound-based interventions.

With real-time instrument tracking and in-situ guidance projection directly integrated in a handheld ultrasound imaging probe, needle-based interventions such as biopsies become much simpler to perform than with conventionally-navigated systems. Stereo imaging with needle detection can be made sufficiently robust and accurate to serve as primary navigation input. We describe the low-cost, easy-to-use approach used in the Clear Guide ONE generic navigation accessory for ultrasound machines, outline different available guidance methods, and provide accuracy results from phantom trials.

A New Camera and Projector Calibration Method Based on Discrete Computation

This paper presents a novel method for the calibration of camera and projector based on discrete computation, which uses a linear moving chessboard and project plane to get a calibration database for camera and projector. The camera database contains multi-layers data of the captured chessboard corners and their corresponding practical coordinates in the system. Then by using this database and interpolation algorithm, we can calculate the accurate position for each given pixel position in the captured image. After this we change the chessboard with a white scene and project a chessboard image to the plane. By capturing the projected image and computing the practical position for the corners in the image, we can get a relationship between practical coordinates and the projected image pixels. So another database for the project image and the practical coordinates is established. By using these two databases, we can define the light line for the pixels in a camera captured image and projected image, which can be used for 3D scanning system and other industrial systems, like mask-image projection stereo lithography rapid prototyping system.

3D Archaeology at Çatalhöyük

The project “3D-Digging at Çatalhöyük” began in 2010 thanks to collaboration between Stanford University (Archaeological Center) and the University of California Merced with the scope to record, document (with different digital technologies) and visualize in virtual reality all the phases of archaeological excavation. Phase I (2010 excavation season) of the project was mainly oriented to test different technologies during the excavation (time of flight and optical laser scanners). In phase II (2011 excavation season) the UC Merced team initiated the excavation of a Neolithic house (building 89), recording all the layers by time phase-shift scanners and computer vision techniques. The recording of the excavation process through the use of digital technologies gave the team the ability to generate 3D models of layers and micro-stratigraphies in stereovision during the excavation (using stereo projectors), so as to stimulate a new digital hermeneutics in archaeology. At the end of the fieldwork all the 3D models are accessible through a Teleimmersive system created by UC Merced and UC Berkeley.

Image synthesis for autostereoscopic systems

The article considers image synthesis for autostereoscopic systems -- systems that enable the viewer to perceive three-dimensional images without any special devices, such as glasses. The general image synthesis problem for such systems is stated and an efficient algorithm is proposed for its solution. Some applications of the proposed methodology for two types of units are described: a stereo display and a stereo projection system. We examine the optimization of technical system parameters with the objective of enlarging the region where the viewer sees a three-dimensional image.