Stereoscopic Image Pairs Research Articles

Research on the Stereoscopic Image Pairs with 3D Automatic Architectural Objects Modeling Techniques

Research on the Stereoscopic Image Pairs with 3D Automatic Architectural Objects Modeling Techniques

Micro-prism type single-lens 3D aircraft telescope system

Based on the image payload on an Unmanned Aircraft System, this study utilizes a micro-prism array and single-lens remote camera to assess the feasibility of having two virtual cameras shoot terrain image pairs with inclined ±10°. The software, LightTools, is applied for simulating and verifying the feasibility of the optical system. In comparison with traditional frame-type remote cameras, this study not only could acquire highly overlapped stereoscopic image pairs from different viewing angles, but could also increase the stereoscopic image pairs by two times. The system we propose obtains more stereoscopic digital terrain information than do traditional systems.

Automatic calculation of tree diameter from stereoscopic image pairs using digital image processing

Automatic operations play an important role in societies by saving time and improving efficiency. In this paper, we apply the digital image processing method to the field of lumbering to automatically calculate tree diameters in order to reduce culler work and enable a third party to verify tree diameters. To calculate the cross-sectional diameter of a tree, the image was first segmented by the marker-controlled watershed transform algorithm based on the hue saturation intensity (HSI) color model. Then, the tree diameter was obtained by measuring the area of every isolated region in the segmented image. Finally, the true diameter was calculated by multiplying the diameter computed in the image and the scale, which was derived from the baseline and disparity of correspondence points from stereoscopic image pairs captured by rectified configuration cameras.

Two eyes see more than one: double echo stereoscopic MRA for rapid 3D visualization of vascular structures

A three-dimensional (3D) visualization of the target region during intravascular interventions in real-time is challenging since the acquisition of a time-consuming 3D dataset is required. In this work, a novel stereoscopic double echo sequence for achieving 3D depth perception by sampling only two oblique projection images is presented. A double echo (DE) FLASH pulse sequence was developed to acquire continuously stereoscopic image pairs of the vascular target anatomy. Stereo image data were displayed on a stereoscopic 3D LCD monitor in real time after image reconstruction. Phantom experiments followed by a depth perception test were performed to assess the usability of the stereo image pairs for 3D visualization. In an animal experiment the sequence was tested in vivo and was compared with a slower interleaved (IL) sequence variant. In the phantom experiments an SNR difference of 6 % between left and right image was found which did not influence the depth perception. The DE acquisition was superior to the IL sequence (SNR(DE) = 10.3, 2.3 images/s over SNR(IL) = 7.1, 1.7 images/s), and during contrast enhancement the abdominal arterial vasculature was clearly perceived as a 3D structure. A novel stereoscopic DE pulse sequence can be utilized for the fast 3D stereoscopic visualization of vascular structures in real-time.

EXACTRACx-ray and beam isocenters-What's the difference?

To evaluate the geometric accuracy of the isocenter of an image-guidance system, as implemented in the exactrac system from brainlab, relative to the linear accelerator radiation isocenter. Subsequently to correct the x-ray isocenter of the exactrac system for any geometric discrepancies between the two isocenters. Five Varian linear accelerators all equipped with electronic imaging devices and exactrac with robotics from brainlab were evaluated. A commercially available Winston-Lutz phantom and an in-house made adjustable base were used in the setup. The electronic portal imaging device of the linear accelerators was used to acquire MV-images at various gantry angles. Stereoscopic pairs of x-ray images were acquired using the exactrac system. The deviation between the position of the external laser isocenter and the exactrac isocenter was evaluated using the commercial software of the exactrac system. In-house produced software was used to analyze the MV-images and evaluate the deviation between the external laser isocenter and the radiation isocenter of the linear accelerator. Subsequently, the deviation between the radiation isocenter and the isocenter of the exactrac system was calculated. A new method of calibrating the isocenter of the exactrac system was applied to reduce the deviations between the radiation isocenter and the exactrac isocenter. To evaluate the geometric accuracy a 3D deviation vector was calculated for each relative isocenter position. The 3D deviation between the external laser isocenter and the isocenter of the exactrac system varied from 0.21 to 0.42 mm. The 3D deviation between the external laser isocenter and the linac radiation isocenter ranged from 0.37 to 0.83 mm. The 3D deviation between the radiation isocenter and the isocenter of the exactrac system ranged from 0.31 to 1.07 mm. Using the new method of calibrating the exactrac isocenter the 3D deviation of one linac was reduced from 0.90 to 0.23 mm. The results were complicated due to routine maintenance of the linac, including laser calibration. It was necessary to repeat the measurements in order to perform the calibration of the exactrac isocenter. The deviations between the linac radiation isocenter and the exactrac isocenter were of an order that may have clinical relevance. An alternative method of calibrating the isocenter of the exactrac system was applied and reduced the deviations between the two isocenters.

Super deep 3D images from a 3D omnifocus video camera

When using stereographic image pairs to create three-dimensional (3D) images, a deep depth of field in the original scene enhances the depth perception in the 3D image. The omnifocus video camera has no depth of field limitations and produces images that are in focus throughout. By installing an attachment on the omnifocus video camera, real-time super deep stereoscopic pairs of video images were obtained. The deeper depth of field creates a larger perspective image shift, which makes greater demands on the binocular fusion of human vision. A means of reducing the perspective shift without harming the depth of field was found.

Automated 3D-Objectdocumentation on the Base of an Image Set

Digital stereo-photogrammetry allows users an automatic evaluation of the spatial dimension and the surface texture of objects. The integration of image analysis techniques simplifies the automation of evaluation of large image sets and offers a high accuracy [1]. Due to the substantial similarities of stereoscopic image pairs, correlation techniques provide measurements of subpixel precision for corresponding image points. With the help of an automated point search algorithm in image sets identical points are used to associate pairs of images to stereo models and group them. The found identical points in all images are basis for calculation of the relative orientation of each stereo model as well as defining the relation of neighboured stereo models. By using proper filter strategies incorrect points are removed and the relative orientation of the stereo model can be made automatically. With the help of 3D-reference points or distances at the object or a defined distance of camera basis the stereo model is orientated absolute. An adapted expansion- and matching algorithm offers the possibility to scan the object surface automatically. The result is a three dimensional point cloud; the scan resolution depends on image quality. With the integration of the iterative closest point- algorithm (ICP) these partial point clouds are fitted to a total point cloud. In this way, 3D-reference points are not necessary. With the help of the implemented triangulation algorithm a digital surface models (DSM) can be created. The texturing can be made automatically by the usage of the images that were used for scanning the object surface. It is possible to texture the surface model directly or to generate orthophotos automatically. By using of calibrated digital SLR cameras with full frame sensor a high accuracy can be reached. A big advantage is the possibility to control the accuracy and quality of the 3d-objectdocumentation with the resolution of the images. The procedure described here is implemented in software Metigo 3D.

Benefits of Matching Accommodative Demands to Vergence Demands in a Binocular Head-Mounted Display: A Study on Stereo Fusion Times

Current head-mounted displays (HMDs) provide only a fixed lens focus. Viewers have to decouple their accommodation and vergence responses when viewing stereoscopic images presented on an HMD. This study investigates the time taken to fuse a pair of stereoscopic images displayed on an HMD when the accommodative demand is matched to the vergence demand. Four testing conditions exhausting the factorial combinations of accommodative demands (2.5 D and 0.5 D) and vergence demands (2.5 MA and 0.5 MA) were investigated. The results indicate that viewers take a significantly shorter amount of time to fuse a pair of stereoscopic images (i.e., fusion time) when the accommodative demand and the stereoscopic depth cues match. Further analysis suggests that an unnatural demand for the eyes to verge toward stereoscopic images whose stereo depth is farther than the accommodative demand is associated with significantly longer fusion time. This study evaluates the potential benefits of using a dynamically adjustable lens focus in future designs of HMDs.

Multi-perspective stereoscopy from light fields

This paper addresses stereoscopic view generation from a light field. We present a framework that allows for the generation of stereoscopic image pairs with per-pixel control over disparity, based on multi-perspective imaging from light fields. The proposed framework is novel and useful for stereoscopic image processing and post-production. The stereoscopic images are computed as piecewise continuous cuts through a light field, minimizing an energy reflecting prescribed parameters such as depth budget, maximum disparity gradient, desired stereoscopic baseline, and so on. As demonstrated in our results, this technique can be used for efficient and flexible stereoscopic post-processing, such as reducing excessive disparity while preserving perceived depth, or retargeting of already captured scenes to various view settings. Moreover, we generalize our method to multiple cuts, which is highly useful for content creation in the context of multi-view autostereoscopic displays. We present several results on computer-generated content as well as live-action content.

Stereoscopic photon counting passive sensing for extraction of distance information

Photon-counting sensing has been widely used in low-light level imaging applications. Photon-counting images can be processed in a simpler and faster manner especially when the binary photon numbers are considered. In this paper, a distance extraction method with stereoscopic photon-counting passive sensing is proposed. Distance extraction is carried out with a stereoscopic photon counting image pair. Nonlinear correlation obtains horizontal discrepancy that maximizes the similarity between two rectified photon-counting images. Computer experiments confirm that the proposed method can extract distance information to an object under low-light level conditions. Performance is evaluated by mean and variance of distance obtained with varying expected number of photons in the scene.

Data fusion using aerial photographs and satellite images for detailed landslide assessment

Hong Kong is one of the world's mountainous international cities, and landslides are a constant threat to human life and property. Monitoring landslides in Hong Kong is important and this is always done by field surveying. However, although conventional survey techniques provide accurate landslide information, they are limited to small areas and physical contact with the slope may be dangerous. Remote sensing techniques can provide an alternative for collecting information about landslide causes and occurrences, and they may assist in the prediction of future landslide occurrences. This article demonstrates the use of monoscopic and stereoscopic aerial photographs, along with satellite images from the IKONOS very high resolution (VHR) sensor for detailed landslide hazard assessment over Hong Kong. For monoscopic aerial photographs, a fusion technique for generating pseudo true colour images from false colour aerial photographs was demonstrated. The pseudo true colour image is useful for better visual analysis in the photogrammetric model. For monoscopic IKONOS image, a set of image fusion techniques was applied in order to improve landslide interpretation, and the results were examined visually and statistically. The Pan-sharpening method among all the image fusion techniques has been demonstrated to have superior performance for identifying both landslide trails and crowns. Stereoscopic viewing using a stereoscopic pair of aerial photographs and stereoscopic IKONOS images was employed for more detailed landslide investigation such as landscape positional relationships (e.g. streams and ridges). Digital elevation models (DEM) were generated from aerial photographs and IKONOS stereoscopic images, and they were compared with digital contour data with 2 m contour interval. The DEMs generated from digital photogrammetric model and IKONOS stereoscopic images are consistently more accurate than an existing DEM, and are sensitive to micro-scale terrain features. The Hong Kong Civil Engineering Department may use the derived monoscopic fused images, stereoscopic images, DEM and anaglyph as objective measures for a detailed landslide study within Hong Kong.

3DTV Broadcasting and Distribution Systems

In this paper, the authors present three-dimensional television (3DTV) broadcasting and distribution systems that are employed to deliver a pair of stereoscopic images to mobile users, as well as users at home. First, mobile 3DTV systems and services based on DMB and DVB-H are respectively introduced. Second, fixed and high-definition 3DTV systems and services based on terrestrial digital broadcasting are described along with an introduction of experimental 3DTV services in Korea. To be specific, the authors summarize 3DTV systems from the viewpoints of target services, system and user requirements, system configurations, broadcasting trials, related standards, and technical challenges.

Binocular Just-Noticeable-Difference Model for Stereoscopic Images

Conventional 2-D Just-Noticeable-Difference (JND) models measure the perceptible distortion of visual signal based on monocular vision properties by presenting a single image for both eyes. However, they are not applicable for stereoscopic displays in which a pair of stereoscopic images is presented to a viewer's left and right eyes, respectively. Some unique binocular vision properties, e.g., binocular combination and rivalry, need to be considered in the development of a JND model for stereoscopic images. In this letter, we propose a binocular JND (BJND) model based on psychophysical experiments which are conducted to model the basic binocular vision properties in response to asymmetric noises in a pair of stereoscopic images. The first experiment exploits the joint visibility thresholds according to the luminance masking effect and the binocular combination of noises. The second experiment examines the reduction of visual sensitivity in binocular vision due to the contrast masking effect. Based on these experiments, the developed BJND model measures the perceptible distortion of binocular vision for stereoscopic images. Subjective evaluations on stereoscopic images validate of the proposed BJND model.

In-line phase-contrast stereoscopic X-ray imaging for radiological purposes: An initial experimental study

We report results from a pilot study in which the in-line propagation-based phase-contrast imaging technique is combined with the stereoscopic method. Two phantoms were imaged at several sample–detector distances using monochromatic, 30 keV, X-rays. High contrast- and spatial-resolution phase-contrast stereoscopic pairs of X-ray images were constructed using the anaglyph approach and a vivid stereoscopic effect was demonstrated. On the other hand, images of the same phantoms obtained with a shorter sample-to-detector distance, but otherwise the same experimental conditions (i.e. the same X-ray energy and absorbed radiation dose), corresponding to the conventional attenuation-based imaging mode, hardly revealed stereoscopic effects because of the lower image contrast produced. These results have confirmed our hypothesis that stereoscopic X-ray images of samples with objects composed of low-atomic-number elements are considerably improved if phase-contrast imaging is used. It is our belief that the high-resolution phase-contrast stereoscopic method will be a valuable new medical imaging tool for radiologists and that it will be of help to enhance the diagnostic capability in the examination of patients in future clinical practice, even though further efforts will be needed to optimize the system performance.

3-D reconstruction of active regions with STEREO

We review data analysis and physical modeling related to the 3-D reconstruction of active regions in the solar corona, using stereoscopic image pairs from the STEREO/EUVI instrument. This includes the 3-D geometry of coronal loops (with measurements of the loop inclination plane, coplanarity, circularity, and hydrostaticity), the 3-D electron density and temperature distribution (which enables diagnostics of hydrostatic, hydrodynamic, and heating processes), the 3-D magnetic field (independent of any theoretical model based on photospheric extrapolations), as well as the 3-D reconstruction of CME phenomena, such as EUV dimming, CME acceleration, CME bubble expansion, and associated Lorentz forces that excite MHD kink-mode oscillations in the surroundings of a CME launch site. The mass of CMEs, usually measured from white-light coronagraphs, can be determined independently from the EUV dimming in the CME source region. The detailed 3-D density and temperature structure of an active region can be modeled using the method of instant stereoscopic tomography with orders of magnitude higher spatial resolution than with standard solar-rotation tomography.

Retinal Vascular Fractal Dimension Measurement and Its Influence from Imaging Variation: Results of Two Segmentation Methods

Aim: To assess the influences of imaging variation (different photographic angle) on the measurement of retinal vascular fractal dimension (Df), using two segmentation methods.Materials and methods: Nonlinear orthogonal projection segmentation (International Retinal Imaging Software-Fractal, termed IRIS-Fractal) and curvature-based segmentation (Singapore Institute Vessel Assessment-Fractal, termed SIVA-Fractal) methods were used to measure Df and were assessed for their reproducibility in detecting retinal vessels of 30 stereoscopic pairs of optic disc color images. Each pair was taken from the same eye with slightly different angles of incidence. Each photograph of the pairs had subtle variations in brightness between areas temporal and nasal to the optic disc.Results: Intragrader reproducibility of Df measurement was similar (intraclass correlation 0.81 and 0.96, respectively) for IRIS-Fractal and SIVA-Fractal. Within-image pair Pearson’s correlation coefficients (r) of Df measurements were moderate for both methods (0.57 and 0.48, respectively).Conclusions: Both nonlinear orthogonal projection and curvature-based retinal vessel segmentation methods were found to be sensitive to variations in image brightness, resulting from iris shadowing associated with different angle of photographic incidence.

Interacting with the biomolecular solvent accessible surface via a haptic feedback device

BackgroundFrom the 1950s computer based renderings of molecules have been produced to aid researchers in their understanding of biomolecular structure and function. A major consideration for any molecular graphics software is the ability to visualise the three dimensional structure of the molecule. Traditionally, this was accomplished via stereoscopic pairs of images and later realised with three dimensional display technologies. Using a haptic feedback device in combination with molecular graphics has the potential to enhance three dimensional visualisation. Although haptic feedback devices have been used to feel the interaction forces during molecular docking they have not been used explicitly as an aid to visualisation.ResultsA haptic rendering application for biomolecular visualisation has been developed that allows the user to gain three-dimensional awareness of the shape of a biomolecule. By using a water molecule as the probe, modelled as an oxygen atom having hard-sphere interactions with the biomolecule, the process of exploration has the further benefit of being able to determine regions on the molecular surface that are accessible to the solvent. This gives insight into how awkward it is for a water molecule to gain access to or escape from channels and cavities, indicating possible entropic bottlenecks. In the case of liver alcohol dehydrogenase bound to the inhibitor SAD, it was found that there is a channel just wide enough for a single water molecule to pass through. Placing the probe coincident with crystallographic water molecules suggests that they are sometimes located within small pockets that provide a sterically stable environment irrespective of hydrogen bonding considerations.ConclusionBy using the software, named HaptiMol ISAS (available from ), one can explore the accessible surface of biomolecules using a three-dimensional input device to gain insights into the shape and water accessibility of the biomolecular surface that cannot be so easily attained using conventional molecular graphics software.

Time-multiplexed dual-focal plane head-mounted display with a liquid lens

Focus cues play a significant role in three-dimensional (3-D) depth perception. Conventional stereoscopic displays, however, lack the ability to correctly render these cues, because they present a pair of stereoscopic images on a fixed image plane while forcing the eyes to converge at different distances to view objects at different depths. Using a fast liquid-lens device, we present the design and implementation of a time-multiplexed dual-focal plane display that is capable of rendering correct or near-correct focus cues as well as other depth cues, such as occlusion and shading for a 3-D scene. The focus range of the dual focal planes can vary from infinity to as close as 8 diopters. Two driving mechanisms are proposed to render near-correct focus cues and their effects on image sharpness, flicker, and brightness are compared.

FIRST THREE-DIMENSIONAL RECONSTRUCTIONS OF CORONAL LOOPS WITH THESTEREO A+BSPACECRAFT. III. INSTANT STEREOSCOPIC TOMOGRAPHY OF ACTIVE REGIONS

Here we develop a novel three-dimensional (3D) reconstruction method of the coronal plasma of an active region by combining stereoscopic triangulation of loops with density and temperature modeling of coronal loops with a filling factor equivalent to tomographic volume rendering. Because this method requires only a stereoscopic image pair in multiple temperature filters, which are sampled within 1 minute with the recent STEREO/EUVI instrument, this method is about four orders of magnitude faster than conventional solar rotation-based tomography. We reconstruct the 3D density and temperature distribution of active region NOAA 10955 by stereoscopic triangulation of 70 loops, which are used as a skeleton for a 3D field interpolation of some 7000 loop components, leading to a 3D model that reproduces the observed fluxes in each stereoscopic image pair with an accuracy of a few percents (of the average flux) in each pixel. With the stereoscopic tomography we infer also a differential emission measure distribution over the entire temperature range of T 104-107, with predictions for the transition region and hotter corona in soft X-rays. The tomographic 3D model provides also large statistics of physical parameters. We find that the extreme-ultraviolet loops with apex temperatures of Tm 3.0 MK tend to be super-hydrostatic, while hotter loops with Tm 4-7 MK are near-hydrostatic. The new 3D reconstruction model is fully independent of any magnetic field data and is promising for future tests of theoretical magnetic field models and coronal heating models.

Diagnostic role of new circulating markers in bone metastases from breast cancer

The BepiColombo space mission is one of the European Space Agency's cornerstone projects; it is planned for launch in 2013 to study the planet Mercury. One of the imaging instruments of BepiColombo is a STereo Camera (STC), whose main scientific objective is the global stereo mapping of the entire surface of Mercury. STC will permit the generation of a Digital Terrain Model (DTM) of Mercury's surface, improving the interpretation of morphological features at different scales and clarifying the stratigraphic relationships between different geological units.To evaluate the effectiveness of the STC-derived DTM for geological purposes, a series of simulations has been performed to find out to what extent the errors expected in the DTM may prevent the correct classification and interpretation of geological features. To meet this objective, Earth analogues (a crater, a lava cone and an endogenous dome) of likely components of the Hermean surface, small enough to be near the detection limit of the STC, were selected and a photorealistic three-dimensional (3D) model of each feature was generated using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) stereo images. Stereoscopic pairs of synthetic images of each feature were then generated from the 3D model at different locations along the BepiColombo orbit. For each stereo pair, the corresponding Hermean DTM was computed using image correlation and compared to the reference data to assess the loss of detail and interpretability. Results show that interpretation and quantitative analysis of simple craters morphologies and small volcanic features should be possible all along the periherm orbit arc. At the apoherm only the larger features can be unequivocally distinguished, but they will be reconstructed to a poor approximation.