Three-dimensional Image Formation Research Articles

Апроксимація дистрибутивної функції відбивної здатності поверхні поліном третього степеня

In the article a bidirectional reflectance distribution function based on a polynomial of the third degree is developed. The main disadvantages of Schlick, Phong, Blinn reflectance models are analyzed. The approximation of Blinn-Phong model by a cubic polynomial is proposed to improve the productivity of three-dimensional image formation. Formulas for the coefficients of the approximation cubic polynomial are calculated. The disadvantages of using the proposed cubic polynomial for reproducing the glare’s attenuation zone are considered. A function for high-precision reproduction of this zone is proposed, formulas of its coefficients are calculated. A combined function, combining a cubic polynomial for reproducing the glare’s epicenter zone and a function for reproducing the attenuation zone, is proposed. The plot of the combined function is built. It is shown that the combined function reproduces the glare’s epicenter and attenuation zones with small relative and absolute errors. The developed reflectance model provides a highly-productive formation of three-dimensional scenes in computer graphics systems. The proposed distribution function of surface reflectivity can be used in computer graphics systems.

Multi-Circular SAR Three-Dimensional Image Formation via Group Sparsity in Adjacent Sub-Apertures

Multi-circular SAR(MCSAR) can obtain holographic three-dimensional (3D) images of interesting observation targets, which is a significant research field at present. For anisotropic scatterers, the multi-circular SAR incoherent 3D imaging strategy combines the principle of tomography SAR inversion to obtain better reconstruction results. However, in incoherent 3D imaging, the traditional L1-norm regularization method only considers sparse representation and reconstruction in the sub-aperture pixel unit along the elevation direction, and the target structural sparsity in the same pixel unit between adjacent sub-apertures is not considered. The hierarchical sparsity constraint method in multi-circular SAR 3D target reconstruction is proposed in this paper, the L1-norm regularization is used in sub-aperture elevation, and the L2,1-regularization-based group sparsity constraint is adopted in elevation of the adjacent sub-aperture. In this paper, the sparse group thresholding iterative method is proposed to reconstruct the 3D observed target image with MCSAR data. Compared with the traditional L1-norm regularization method and IAA-GLRT method for MCSAR target reconstruction in elevation, the proposed method in this paper could obtain clearer 3D observation target images, with fewer desultory points along the elevation direction. Detailed simulation data analysis and 3D imaging processing of real MCSAR data demonstrate the advantages of the proposed method.

РОЗРОБКА МОДЕЛІ ВІДБИВНОЇ ЗДАНОСТІ ПОВЕРХНІ З ВИКОРИСТАННЯМ ПОЛІНОМІВ ЧЕБИШЕВА

At this stage of computer graphics development, an important task is to ensure high productivity of graphic scenes, sufficient for real-time and interactive mode, when it is assumed that the trajectories of objects are not set in advance, but determined by user actions in interaction with the system. For such modes there are strict requirements for the time of formation of three-dimensional graphic scenes. In the formation of three-dimensional images for the optical properties of the surface is responsible for the two-beam distributive function of reflectivity (DFVZ). It is a model of illumination and determines what proportion of the radiation received at a point from the direction of the light source will be reflected in the direction of the observer. A fundamental requirement for DFVZ is its calculation through the cosine of the angle between the corresponding vectors of normals, which is easy to find through the scalar product of vectors. When developing the model, it is important that the image of the reflection relative to the reference implementation has no visual differences. Simple hardware implementation of the function is possible when using low-degree polynomials, provided that the calculation does not use complex functions and long-term operations that take place for known approaches. When forming glare, it is important to reproduce its epicenter with sufficient accuracy. For peripheral areas, which characterize the attenuation of light intensity to a minimum value, it is necessary to ensure the monotony of color intensity change, which eliminates the appearance of artifacts. The paper develops a new model of surface reflectivity using Chebyshev polynomials, which has a second degree and a simple hardware implementation and satisfies the above requirements. Formulas for calculating the component coefficients are obtained. The developed model reproduces the epicenter of the glare with high accuracy. Estimates of the accuracy of the approximation are obtained. The structural scheme of the device for formation of a two-beam distributive function of reflectivity is developed. The developed model of surface reflectivity can be used in systems of dynamic three-dimensional graphics.

Can Abbe theory of image formation be improved ?

Abbe theory of image formation can be expanded from two-dimensional to three-dimensional space. It has to consider an optical system that forms an image of a grating in an object space. It is possible to introduce various inclinations of this grating relatively the optical axis round the axis in the object plane that is parallel to its slits. In this case, the minimum resolvable period and the corresponded spatial cut off frequency of the optical system may be calculated as the functions of the angle of grating inclination, the numerical apertures and the wavelength using the idea of Abbe theory. In case of axial symmetry of the optical system, the function for calculation of the spatial cut off frequencies describes a surface in the three-dimensional space of spatial frequencies that covers the three-dimensional spatial bandwidth. The spatial harmonics with spatial frequencies inside this spatial bandwidth can pass through an optical system and they participate in formation of three-dimensional images. The other spatial harmonics cannot pass through it. This approach makes understanding and explanation of formation of three-dimensional images clearer, faster and logically completed.

Formation of Dynamic and Binocular Three-Dimensional Images in Protective Holograms with Zero Diffraction Order

Variants of implementing trackograms, one of the types of zero-order holograms, for the formation of protective features for non-expert verification of their authenticity are considered. The three-dimensional image in trackograms is formed by glares on the walls of toroidal surfaces-tracks that represent relief stripes with the recording material. Variations in the shape of tracks, their length, and the number of sections of different tracks at one point in the image can provide security features that are convenient for non-expert identification of holograms. Track sizes and depths are compatible with the technology of conventional embossed holograms. Photos of holograms forming images in white light are shown.

Ray tracing 3D spectral scenes through human optics models.

Scientists and engineers have created computations and made measurements that characterize the first steps of seeing. ISETBio software integrates such computations and data into an open-source software package. The initial ISETBio implementations modeled image formation (physiological optics) for planar or distant scenes. The ISET3d software described here extends that implementation, simulating image formation for three-dimensional scenes. The software system relies on a quantitative computer graphics program that ray traces the scene radiance through the physiological optics to the retinal irradiance. We describe and validate the implementation for several model eyes. Then, we use the software to quantify the impact of several physiological optics parameters on three-dimensional image formation. ISET3d is integrated with ISETBio, making it straightforward to convert the retinal irradiance into cone excitations. These methods help the user compute the predictions of optics models for a wide range of spatially rich three-dimensional scenes. They can also be used to evaluate the impact of nearby visual occlusion, the information available to binocular vision, or the retinal images expected from near-field and augmented reality displays.

Формирование объемных изображений на полиметилметакрилате под воздействием излучения волоконного лазера

Формирование объемных изображений на полиметилметакрилате под воздействием излучения волоконного лазера

Research on remelting phenomena and metal joining of fused-coating additive manufacturing

Metal fused-coating is a novel additive manufacturing technology used to building complex components. In order to determine good metallurgical bonding between layers, a two-dimensional model was established to predict the temperature needed to promote the metallurgical bonding of multi-layer specimens. The temperature of the cladding process was tracked and measured by the thermal imaging system. The influence of heat transfer on the forming characteristics of the fusion track was studied systematically. In addition, the maximum remelting depth of the liquid-solid interface was evaluated and the interlaminar bonding state was further confirmed by the formation of three-dimensional samples and optical microscopy images. This work may help to develop metal fused-coating to the produce effective process control and performance prediction.

Range Decoupling Algorithm for Accelerating Metamaterial Apertures-Based Computational Imaging

Metamaterial apertures-based computation imaging system enables interrogating the scene information with frequency-diverse complex radiation fields, reducing the complicated active components and mechanical scanning equipments. Nevertheless, when pursuing an accurate perception of the surrounding environment, the natural discretization of imaging volume would inevitably pose the massive amount of data and burdensome computation for the three-dimensional (3-D) image formation. In this paper, we propose a range decoupling algorithm to accelerate the image generation of metamaterial apertures imaging system operating in the far-field. The algorithm could achieve the dimension reduction through exploiting the local frequency coherence of the metamaterial apertures antenna radiation fields, allowing the scene to be decomposed into a number of range cells and reconstructed in a parallel fashion. In this sense, the crucial memory requirements and prohibitively high computation costs could be mitigated while the high-quality 3-D images are maintained. Extensive imaging simulations are conducted to illustrate the effectiveness of the proposed algorithm.

System analysis of formation and perception processes of three-dimensional images in volumetric displays

One of the promising devices is currently a volumetric display. Volumetric displays capable to visualize complex three-dimensional information as nearly as possible to its natural – volume form without the use of special glasses. The invention and implementation of volumetric display technology will expand opportunities of information visualization in various spheres of human activity. The article attempts to structure and describe the interrelation of the essential characteristics of objects in the area of volumetric visualization. Also there is proposed a method of calculation of estimate total number of voxels perceived by observers during the 3D demonstration, generated using a volumetric display with a rotating screen. In the future, it is planned to expand the described technique and implement a system for estimation the quality of generated images, depending on the types of biplanes and their initial characteristics.

Formation of three-dimensional image of the medium by the sum of CDP for the studies of geological structure of mine fields

Traditionally, seismic observations are carried out by the reflected wave method with multiple overlaps. Thus, the primary result of the processing of such data is the sum of CDP. For further imaging there is necessary to have the correct variant of migration without restrictions on the angle of reflectors, which is particularly important for the study of the geological structure of the mine fields. The paper presents a three-dimensional variant of the full-wave finite-difference migration in the time scale of the depths. That variant allows defining delicate structural features of the environment, the velocity model of which can be non-uniform across the board. The effectiveness of the proposed method to study the geological structure of the mine fields is demonstrated on a model example and practical materials observed in the Donbas region.

Combined Vision System for Mobile Robots

The article is devoted to examination of the method for formation of a panoramic image in conjunction with formation of detailed fragments of space objects for the vision systems of the mobile robots. As is known, navigation of the mobile robots often should take into account three coordinates in conjunction with a detailed analysis of the individual objects. It is a common assumption that a vision system operates with a certain set of specific objects, which must be prepared or in some way marked and allocated. The dynamic objects also should be taken into account in the field review. It is proposed that the formation of three-dimensional images of the space objects should be done by combining the stereoscopy methods and highlighting the structural aspect. In preparation of the materials for publication a system was considered which combines vision with a panoramic optoelectronic system, which implements the method of the structural illumination and stereovision, at the same time.

Experiments on a Ground-Based Tomographic Synthetic Aperture Radar

This paper presents the development and experiment of three-dimensional image formation by using a ground-based tomographic synthetic aperture radar (GB-TomoSAR) system. GB-TomoSAR formulates two-dimensional synthetic aperture by the motion of antennae, both in azimuth and vertical directions. After range compression, three-dimensional image focusing is performed by applying Deramp-FFT (Fast Fourier Transform) algorithms, both in azimuth and vertical directions. Geometric and radiometric calibrations were applied to make an image cube, which is then projected into range-azimuth and range-vertical cross-sections for visualization. An experiment with a C-band GB-TomoSAR system with a scan length of 2.49 m and 1.86 m in azimuth and vertical-direction, respectively, shows distinctive three-dimensional radar backscattering of stable buildings and roads with resolutions similar to the theoretical values. Unstable objects such as trees and moving cars generate severe noise due to decorrelation during the eight-hour image-acquisition time.

Mid-Wave Infrared 3D Integral Imaging at Long Range

Integral imaging is an established method for passive three-dimensional (3D) image formation, visualization, and ranging. The applications of integral imaging include significantly improved scene segmentation and the ability to visualize occluded objects. Past demonstrations of this technique have been mainly conducted over short ranges achievable in the laboratory. In this paper, we demonstrate 3D computational integral imaging for ranges out to 2 km using multiple looks from a single moving mid-wave infrared (MWIR) imager. We also demonstrate 3D visualization of occluded objects at ranges over 200 m. To our knowledge, this paper is the first such demonstration at these ranges and the first example of this technique using a mid wave IR imaging system. In addition to presenting results, we also outline our new approach for overcoming the technical challenges unique to long range applications of integral imaging. Future applications of long range 3D integral imaging may include aerospace, search and rescue, satellite 3D imaging, etc.

Real-time reconstruction of three-dimensional cylindrical near-field radar images using a single instruction multiple data interpolation approach

During the last decade, radar imaging has been used in near-field scenarios where a cylindrical scan geometry is required to properly illuminate the scan region, such as breast microwave radar imaging and microwave wood inspection. Nevertheless, current cylindrical near-field radar image formation algorithms are not fast enough to provide the throughput required by these novel applications. A real-time wavefront reconstruction approach for the formation of three-dimensional cylindrical near-field radar images is proposed in this study. This technique parallelises the mapping procedures during the reconstruction process in order to increase its computational efficiency. To further reduce the execution time of the proposed approach, it was implemented in a general purpose graphic processing unit in order to take advantage of the computing capabilities of this platform. The proposed method yielded accurate results when applied to simulated and experimental data sets and yielded speed improvements of two orders of magnitude compared to conventional cylindrical near-field radar reconstruction approaches.

Computer simulation of the formation of three-dimensional image of the pyrolytic graphite surface by scanning tunneling microscopy using a boron-doped diamond tip

A developed physico-mathematical model has made it possible to obtain an image of the pyrolyti graphit surfac b scannin tunnelin microscop usin semiconductin boron-dope diamon tip.

Use of a temporal approach to the three-dimensional image formation of a distant rough nonplanar object

A method is proposed to reconstruct three-dimensional images of a distant nonplanar rough object by the speckle pattern of its flat image, which is calculated using the temporal approach based on the time correlation function of probe radiation with a coherence length smaller than the size of the probed object. We analyse the influence of the angular resolution of the optical system, forming an image of the object, and additive noises on the reconstruction accuracy of the object surface shape using the proposed method.

Interferometric Synthetic Aperture Microscopy: Computed Imaging for Scanned Coherent Microscopy

Three-dimensional image formation in microscopy is greatly enhanced by the use of computed imaging techniques. In particular, Interferometric Synthetic Aperture Microscopy (ISAM) allows the removal of out-of-focus blur in broadband, coherent microscopy. Earlier methods, such as optical coherence tomography (OCT), utilize interferometric ranging, but do not apply computed imaging methods and therefore must scan the focal depth to acquire extended volumetric images. ISAM removes the need to scan the focus by allowing volumetric image reconstruction from data collected at a single focal depth. ISAM signal processing techniques are similar to the Fourier migration methods of seismology and the Fourier reconstruction methods of Synthetic Aperture Radar (SAR). In this article ISAM is described and the close ties between ISAM and SAR are explored. ISAM and a simple strip-map SAR system are placed in a common mathematical framework and compared to OCT and radar respectively. This article is intended to serve as a review of ISAM, and will be especially useful to readers with a background in SAR.

The optics of microscopy

The optical microscope is a standard optical instrument that is used as an example to introduce the principles of optics. However, some of the assumptions that are used to describe image formation are highly suspect. Take the paraxial approximation, for example, which assumes angles are small when in practice they can be greater than 70°. Research into new microscope techniques and improvements in understanding quantitatively the image formation process has led to investigations in various areas of optics including diffraction theory, pupil filters, non-paraxial focusing, vectorial effects, finite Fresnel number, partial coherence, three-dimensional image formation, beam propagation, ultra-short pulse propagation and scattering theory. Some of these topics are reviewed, with particular emphasis on their applications in microscopy. Also, in addition to their intrinsic scientific interest, some of these areas have other applications, in optical information storage and lithography for example. This paper is based on a plenary presentation at Photonics06, Manchester UK, on the award of the Institute of Physics Optics and Photonics Division Prize 2006.

Education of Machine Design Using 3-D CAD/CAE

In recent years, 3-D CAD/CAE system has come into wide use in Japanese manufacturers. So, engineering education is required to respond to the trend quickly and effectively. The program shall be enough for undergraduate to acquire a basic level of proficiency in skills needed for machine-designing using 3-D CAD/CAE system. In Meisei University, 150 junior students of mechanical engineering department study computer-aided machine-design with 3-D CAD/CAE system. A model Stirling engine is designed in the first semester and a small reciprocating air compressor is designed in the second semester. Students gain experience of performance and strength calculation, formation of three-dimensional image of parts, stress analysis, collision and clearance check, assembly of parts, movement check, and making drawings for manufacture. The effect of our education was confirmed by the questionnaire survey done to the students.