Ray Projection Research Articles

Ray Projection for Recovering Projective Transformations and Illumination Changes

The ray projection and its application to recovering a projective geometric transformation and an affine lighting change between two objects are mathematically studied. A novel technique, viz., variable contour, is proposed for accurately evaluating the ray projection. Moreover, a novel flexible framework of the ray projection is devised for the joint recovery of the eight parameters for the projective transformation and the two parameters for the lighting change. Finally, the framework is experimentally evaluated by recovering a variety of geometric and photometric transformations between real images of indoor and outdoor scenes. Its robustness to image blur and occlusion is demonstrated. Its versatility is illustrated through matching different objects in different classes.

Control de calidad en radiodiagnóstico podológico: propuesta de criterios de calidad de imagen y dosis de referencia

Spanish legislation transposing the Community legislation on the quality of radiological acts obliges holders of diagnostic radiology facilities to follow a quality assurance program. The program should cover both aspects of radiation protection of patients and quality of the image obtained. This work aims to facilitate the achievement of these goals in podiatric consultation. To this goal, quality criteria based on anatomical findings are proposed for the most usual podiatric X–ray projections, and a provisional reference dose value for the dorso–plantar projection of 2,2 mGy is also proposed.

On evolutionary ray-projection dynamics

We introduce the ray-projection dynamics in evolutionary game theory by employing a ray projection of the relative fitness (vector) function, i.e., a projection unto the unit simplex along a ray through the origin. Ray-projection dynamics are weakly compatible in the terminology of Friedman (Econometrica 59:637–666, 1991), each of their interior fixed points is an equilibrium and each interior equilibrium is one of its fixed points. Furthermore, every interior evolutionarily stable strategy is an asymptotically stable fixed point, and every strict equilibrium is an evolutionarily stable state and an evolutionarily stable equilibrium. We also employ the ray-projection on a set of functions related to the relative fitness function and show that several well-known evolutionary dynamics can be obtained in this manner.

Effect of the Diffuse Radiation Reflection from Exterior wall on Shading Device Integrated Photovoltaic Case of Thailand building

Abstract Presently, a green building concept is the design trend for new building. The Shading Device Integrated Photovoltaic system (SIPV) is one option can be applied for building energy conservation. Although, SIPV has some weakness when a building creates the shadow on SIPV by the sun ray projection. Nevertheless, SIPV operation has many benefits that are reduction and compensation the cooling load of air condition system that it follow from building code as OTTV indicator. Furthermore, Design can avoid a high performance glass window that is an expensive material. Therefore, the aim of this paper is to evaluate the annual energy yield per square meter of SIPV of the different slopes and directions of SIPV installation and different types of PV module as used for SIPV was compared. The evaluated location refers to building in Bangkok as 14o North latitude. The results shown that SIPV produces maximum energy yield when the slope nearly 120o on South, Southeast or Southwest direction, which is installed on the exterior wall that has the diffuse reflectance value approximately 30% like a rough semi-glossy surface. Amorphus Silicon and Polycrystalline Silicon technology produces the annual energy yield is 84 and 149 kWh/m2-Year respectively. Which replaces absolutely the cooling load from the glass area is 0.85 and 1.51 m2 respectively.

Calibration of a Shack–Hartmann wavefront sensor as an orthographic camera

We demonstrate a method to calibrate a Shack-Hartmann sensor as an orthographic camera. This calibration method permits us to obtain the distance, the rotation matrix between the microlens array and CCD imaging planes, and the projection matrix, which models the projection of the incoming rays to the CCD imaging plane. The proposed calibration method introduces a very compact matrix notation and allows wavefront reconstruction without an explicit centroid search between the reference and distorted spot diagrams. We show a set of simulations in code V that prove the effectiveness of the proposed method.

Glacier velocities from time-lapse photos: technique development and first results from the Extreme Ice Survey (EIS) in Greenland

AbstractAutomated digital cameras were installed in May–June 2007 beside major West Greenland marine-terminating glaciers as part of the Extreme Ice Survey (EIS). EIS cameras began imaging the lowest 4 km2 of the glacier at hourly intervals throughout sunlit periods of the year. This study presents the development of techniques for quantifying glacier velocity from a single camera perspective. A Multi-Image/Multi-Chip matching procedure yields higher matching skill than conventional matching, and facilitates false-match rejection via a clustering scheme. The matching of motionless on-land features facilitates compensating camera motion. Ray projection to a known terrain elevation allows the assigning of scale to convert pixel displacements to velocity units. With the 10.2-megapixel camera system, velocities on relatively fast glaciers can be resolved at distances up to ∼4 km. At a distance of 2 km, a demonstrated precision of ∼0.5 pixels yields a ∼0.5 m footprint size. Daily velocities indicate progressive multi-day velocity accelerations associated with calving. Deceleration trends are associated with the regrowth of resistive stress after major calving. The higher observation frequency available to terrestrial photogrammetry indicates higher observed intra-seasonal velocity range than observable by the at-best weekly satellite snapshots.

Tomographic observation of shallow-water inhomogeneities in the case of probing by a focused high-frequency acoustic field. I. Structure of simulation model

We study the possibilities of acoustic tomography observation of small-size bodies in shallow-water layered oceanic waveguides within the framework of geometric acoustics. For increasing the spatial resolution and sensitivity in the considered inverse problem, we used the waveguide-matched focusing of the received and radiated fields into the region of expected location of the observed body. The algorithm of observation in this case consists of search for a global extremum of decision statistics, which is determined by the difference between the measured data and the hypothetic body location. Such hypotheses are formed on the basis of a priori information in the form of the waveguide model and the data on the structure of the observation system. For decreasing the influence of noise associated with the interference of fields in the waveguide, selection of separate tomographic ray projections with the subsequent incoherent accumulation of partial images is used. A tomographic shallow-water observation model based on such principles is analyzed.

Deep Lamellar Keratoplasty for Recurrent Advanced Pterygium

The authors report a case of recurrent advanced pterygium managed by deep lamellar keratoplasty and conjunctival autograft. A woman presented with bilateral recurrent advanced pterygium (more prevalent in the left eye) associated with corneal thinning in the left eye. Two-thirds of the cornea was covered by pterygia. Her visual acuity was counting fingers at 1 meter in the right eye and light perception with projection of rays being accurate in all quadrants in the left eye. She underwent deep anterior lamellar keratoplasty and conjunctival autograft in her left eye. Clarity, state of corneal graft, and postoperative visual acuity were noted. The graft was clear and the patient's best-corrected visual acuity improved to 20/60 after the surgery. Deep lamellar keratoplasty with conjunctival autograft is a good option as a single-stage surgery for recurrent advanced pterygium.

Approach to modeling and virtual-reality-based simulation for plant canopy lighting

Over the past 20 years, significant progress has been made in virtual plant modeling corresponding to the rapid advances in information technology. Virtual plant research has broad applications in agronomy, forestry, ecology and remote sensing. As many biological processes are driven by light, it is the key for virtual plant to estimate the light absorbed by each organ. This paper presents the radiance equation suitable for calculating sun and sky light intercepted by plant organs based on the principles of the interaction between light and plant canopy firstly; analyzes the process principles of plant canopy primary lighting based on ray casting and projection secondly; describes the multiple scattering of plant lighting based on Monte Carlo ray tracing method and on the radiosity method thirdly; and confirms the research with 3D visualization based on Virtual Reality Modeling Language (VRML) finally. The research is the primary work of digital agriculture, and important for monitoring and estimating corn growth in Northeast China.

Bilateral acute angle closure glaucoma in a 50 year old female after oral administration of flavoxate

Bilateral acute angle closure glaucoma in a 50 year old female after oral administration of flavoxate

Proyección de Rosenberg en la evaluación radiológica de la osteoartrosis de rodilla

Knee osteoarthritis is highly prevalent in our country. An early diagnosis is very important to provide an accurate and early treatment, and eventually delay its progression.To compare the diagnostic yield for osteoarthritis of two projections in knee X ray examination.We evaluated 44 knees with conventional (AP weight-bearing, in full extension) and Rosenberg (PA weight-bearing in 45 degrees of flexion) X ray projections in 32 patients (24 women and 8 men), aged 26 to 78 years. All patients were symptomatic at the time of evaluation, with a suspicion of knee osteoarthritis. Both projections were analyzed and compared.Joint space in the lateral compartment with conventional AP weight-bearing and Rosenberg projections were 8.6+/-11.5 mm and 7.8+/-10.9 mm, respectively (NS). The joint space for the medial compartment were 8.2+/-10.9 mm and 6.7+/-8.6 mm, respectively (p <0.05).Rosenberg projection is more sensitive to detect knee joint space narrowing as compared with conventional AP weight-bearing projection, at least in the medial compartment of the knee. Therefore, Rosenberg projection should be included in the initial study of any patient with suspicion of knee osteoarthritis.

Comparison of Quantitative Coronary Angiography with Intracoronary Ultrasound. Can Quantitative Coronary Angiography Accurately Estimate the Severity of a Luminal Stenosis?

In this study we investigated the accuracy of monoplane and biplane quantitative coronary angiography in estimating the luminal dimensions, using intracoronary ultrasound as gold standard. Biplane angiography and intracoronary ultrasound were performed in 24 arterial segments. The end-diastolic intracoronary ultrasound frames were manually selected and segmented. In 2 end-diastolic X ray projections, quantitative coronary angiography was performed and a novel methodology was applied to register the segmented frames onto the processed angiographic images. The luminal areas determined by quantitative coronary angiography in 1 (monoplane) and 2 projections (mean) were compared with those determined by intracoronary ultrasound. The obtained correlation coefficients for the monoplane and mean estimations were 0.69 +/- 0.12 and 0.77 +/- 0.08, respectively. It would appear that by increasing the angle between the biplane projections, the correlation between intracoronary ultrasound and mean estimations improves. Our results provide evidence that orthogonal biplane angiography is more reliable and should be preferred to assess luminal dimensions.

The Ray Projection Method: A Numerical Approach for Determining Ideal Camera Placement

Data piloting is important to ensure accurate marker coordinate data and to minimize camera dropout. Camera dropout results when a camera fails to image a marker, which often occurs when markers merge or become occluded. In this article, we present the conceptual framework for a numerical method of determining where video cameras, if placed, would have an occluded or a merged view of the tracking markers. Experimental data are presented to demonstrate the efficacy of the method as a tool to complement existing data piloting procedures.

The ultrasonic probe for the investigating of internal object structure by ultrasound transmission tomography

The main component of every device used for investigating internal object structure by Ultrasound Transmission Tomography (UTT) is a special ultrasonic probe. This paper presents the structure of model multielement ring probe for examining objects using this method in divergent ray projection geometry. The probe is made up of 1024 rectangular separate piezoelectric transducers working at frequency f = 1.7 MHz, placed inside a ring with diameter D = 30 cm and height h = 9 cm. Each element of the probe is equipped with a quarter-wave matching layer. All the transducers function as transmitters and receivers, and can be joined in groups both during transmitting and during receiving. Some examples of admittance characteristics of a single piezoelectric transducer and examples of shapes of pulses generated and received by particular transducers were presented. Important factors affecting the measurement resolution are the sizes of the active surface of the transducers.

Three-dimensional identification of biological microorganism using integral imaging

In this paper, we address the identification of biological microorganisms using microscopic integral imaging (II). II senses multi-view directional information of 3D objects illuminated by incoherent light. A micro-lenslet array generates a set of elemental images by projecting a 3D scene onto a detector array. In computational reconstruction of II, 3D volumetric scenes are numerically reconstructed by means of a geometrical ray projection method. The identification of the biological samples is performed using the 3D volume of the reconstructed object. In one approach, the multivariate statistical distribution of the reference sample is measured in 3D space and compared with an unknown input sample by means of statistical discriminant functions. The multivariate empirical cumulative density of the 3D volume image is determined for classification. On the other approach, the graph matching technique is applied to 3D volumetric images with Gabor feature extraction. The reference morphology is identified in unknown input samples using 3D grids. Experimental results are presented for the identification of sphacelaria alga and tribonema aequale alga. We present experimental results for both 3D and 2D imaging. To the best of our knowledge, this is the first report on 3D identification of microorganisms using II.

Noise field anisotropy of surface sources in a coastal region with arbitrary bottom relief and sound velocity profile

The noise field anisotropy of surface sources in a coastal region with an arbitrary three-dimensional bottom relief and an arbitrary sound velocity profile is investigated. The results of computations performed by a computer code in two stages are presented. The first stage consists in the computation of horizontal rays, i.e., the projections of the real rays multiply reflected from the bottom and sea surface onto the horizontal plane. The second stage summarizes the contributions of the noise sources lying within the surface elements that are cut out on the sea surface by a narrow ray tube launched from the point of observation in a given direction. The computations show that, in the coastal region, the noise field is essentially anisotropic, and this anisotropy occurs not only in the vertical plane, which is characteristic of the deep ocean, but in the horizontal plane as well.

3-D shape reconstruction in an active stereo vision system using genetic algorithms

The recovery of 3-D shape information (depth) using stereo vision analysis is one of the major areas in computer vision and has given rise to a great deal of literature in the recent past. The widely known stereo vision methods are the passive stereo vision approaches that use two cameras. Obtaining 3-D information involves the identification of the corresponding 2-D points between left and right images. Most existing methods tackle this matching task from singular points, i.e. finding points in both image planes with more or less the same neighborhood characteristics. One key problem we have to solve is that we are on the first instance unable to know a priori whether a point in the first image has a correspondence or not due to surface occlusion or simply because it has been projected out of the scope of the second camera. This makes the matching process very difficult and imposes a need of an a posteriori stage to remove false matching. In this paper we are concerned with the active stereo vision systems which offer an alternative to the passive stereo vision systems. In our system, a light projector that illuminates objects to be analyzed by a pyramid-shaped laser beam replaces one of the two cameras. The projections of laser rays on the objects are detected as spots in the image. In this particular case, only one image needs to be treated, and the stereo matching problem boils down to associating the laser rays and their corresponding real spots in the 2-D image. We have expressed this problem as a minimization of a global function that we propose to perform using Genetic Algorithms (GAs). We have implemented two different algorithms: in the first, GAs are performed after a deterministic search. In the second, data is partitioned into clusters and GAs are independently applied in each cluster. In our second contribution in this paper, we have described an efficient system calibration method. Experimental results are presented to illustrate the feasibility of our approach. The proposed method yields high accuracy 3-D reconstruction even for complex objects. We conclude that GAs can effectively be applied to this matching problem.

New mathematical model based on affine transformation for remote sensing image with high resolution

This paper calculates the parameters of image position and orientation, proposes a mathematical model and adopts a new method with three steps of transformations based on parallel ray projection. Every step of the model is strict, and the map function of each transformation is the first order polynomials and other simple function. The final calculation of the parameters is for the linear equations with good status. As a result, the problem of the relativity of image parameter calculation is solved completely. Some experiments are carried out.

Shape measurement of columnar objects with specular surfaces by slit ray projection method

AbstractIn this paper, a method for measuring the shape of a columnar object with specular surfaces by a slit ray projection method is proposed. Although the slit ray projection method is effective for measuring the shape of an object having diffuse reflective characteristics, applying the method to an object with specular surfaces has hitherto been difficult. In this paper, a triangulation equation for a columnar object with specular surfaces is derived and used as the basis of a method for measuring the shape of an object having specular surfaces using applicable slit rays. The basic principle is that the angle of incidence of a slit ray reflected from the measured object into an image sensor is restricted specifically by the special design of the optical system. In addition to the theoretical study of the proposed principle, a system for measuring the shape of a columnar specular object and a diffuse object was created and its effectiveness was verified. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 33(4): 50–60, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1119

다중 슬릿광을 이용한 3차원 Solder Paste 검사 시스템

A 3-dimenstional automatic solder paste inspection system is described that can be used to find defects occurring in solder paste printing process. This system extracts height and volume information very fast as well as area of solder paste printed, using multiple slit ray projection and Galvano-mirror scanning. Methods are presented on calibration of camera and slit projector, real-time image processing of multiple slit images, determination of reference height, and extraction of paste height information are proposed. Performance of the system was successfully demonstrated through field tests.