Object Plane Research Articles

EDOF intraocular lens design: shift in image plane vs object vergence

BackgroundTo compare 2 different design scenarios of EDOF-IOLs inserted in the Liou-Brennan schematic model eye using raytracing simulation as a function of pupil size.MethodsTwo EDOF IOL designs were created and optimized for the Liou-Brennan schematic model eye using Zemax ray tracing software. Each lens was optimized to achieve a maximum Strehl ratio for intermediate and far vision. In the first scenario, the object was located at infinity (O1), and the image plane was positioned at far focus (I1) and intermediate focus (I2) to emulate far and intermediate distance vision, respectively. In the second scenario, the image plane was fixed at I1 according to the first scenario. The object plane was set to infinity (O1) for far-distance vision and then shifted closer to the eye (O2) to reproduce the corresponding intermediate vision. The performance of both IOLs was simulated for the following 3 test conditions as a function of pupil size: a) O1 to I1, b) O1 to I2, and c) O2 to I1. To evaluate the imaging performance, we used the Strehl ratio, the root-mean-square (rms) of the spot radius, and the spherical aberration of the wavefront for various pupil sizes.ResultsEvaluating the imaging performance of the IOLs shows that the imaging performance of the IOLs is essentially identical for object/image at O1/I1. Designed IOLs perform dissimilarly to each other in near-vision scenarios, and the simulations confirm that there is a slight difference in their optical performance.ConclusionOur simulation study recommends considering the difference between object shift and image plane shift in design and test conditions to achieve more accurate pseudoaccommodation after cataract surgery.

On the role of Poisson’s contraction propagation in the creation of squeeze-film assisted levitation

The paper presents results of computer simulation and experimental observations with the main objective of explaining the role of Poisson’s contraction phenomenon in the mechanism of initiating and maintaining squeeze-film action through which light and planar objects can be levitated. Initial and centrally located shallow dimple, created in a thin plate under plain tensile stress is, with the passage of time, transformed into a pattern of elastic deformations over plate’s surface. As a result of that, a light object levitates not only at the centre of the plate where initial, primary dimple is located but over the entire plate.

Imaging multiple objects through scattering medium under strong background illumination

Speckle correlation imaging is a typical method to image through strongly scattering medium. However, limited by the optical memory effect range, this method is hard to image multiple objects that are randomly distributed on the object plane with strong background illumination. To solve this problem, we proposed a new method that allows to image multiple objects with strong background illumination. It consists of isolating speckle pattern of each object with an image difference process and eliminating the interference of the background noise with the principal components analysis (PCA) technique. Our method can realize imaging of more than two objects through the scattering medium, and compared with other methods, our method can provide better observations of the objects in the bright field scenarios.

An Optimized Error Compensation Method for Phase Measurement Profilometry

Phase measurement profilometry (PMP) is primarily employed to analyze the morphology of a functional surface with precision. Historically, one of the most complex and persistent challenges in PMP has been reducing errors stemming from inconsistent indicators at the edges of a surface. In response to this challenge, we propose an optimized error compensation methodology specifically designed to handle edge artefacts. This methodology introduces the Hilbert transform and object surface albedo as tools to detect the edges of the artefact region that need to be compensated. Moreover, we analyze the characteristics of the sinusoidal fringe waveform propagation direction and investigate the reconstruction results of the fringe vertical to the current directions to compensate for edge artefacts. The experimental results for various objects show that the optimized approach can compensate for edge artefacts by projecting in two directions and reducing the projection by half. The compensated root mean square error (RMSE) for planar objects can be reduced by over 45%.

An Efficient Method for Determining the Output Plane of a Small-Sized Phase Object in Application to Its Image Processing

An Efficient Method for Determining the Output Plane of a Small-Sized Phase Object in Application to Its Image Processing

English-Ukrainian intersemiotic translation within the configuration of modes of modality in literary texts

The article highlights the main features of intersemiotic translation of a literary text, which is considered to be an expression of the author’s modality as a set of signs of various semiotic systems. Thus, the purpose of the study is to determine the linguistic and non-linguistic means of expressing modality in a literary text, the specifics of their interaction to generate meaning, and the features of their reproduction in intersemiotic translation. The object of modality in translation within a literary text is a set of signs encoded by the author of the source text and organized into a system that is decoded and reproduced by the translator both at the phonological, lexical, and syntactic levels and the semantic, emotional, and associative ones. The analysis of the category of modality from the standpoint of semiotics in literary texts involves decoding semiotic resources, symbols, and signs, taking into account the individual author’s, social, political, cultural, and national contexts. The process of interpreting and reproducing the sign configurations of individual author modality is carried out at the syntactic, semantic, and pragmatic levels to achieve the corresponding aims. Thus, at the first stage, the forms and interactions of determinants are defined and interpreted whereas the second level involves consideration of the internal semantic plane of the research object, and, accordingly, at the third level, the influence and use of signs are outlined. It is proved that adequate literary translation is carried out based on the multimodality of the text that is viewed as a multimodal communication, within which meaning is generated by the configuration of different semiotic sign systems that require interpretation according to the principle of optimal relevance and creativity. The central concept of translation is semiosis as a process of interpretation of a sign and generation of meaning, that indicates the relationship of the sign with the outside world.

SHAPE DEPENDENT MOTION INTERPOLANTS FOR PLANAR OBJECTS.

Kinematics is most commonly about the motion of unbounded spaces. This paper deals with the kinematics of bounded shapes in a plane. This paper studies the problem of motion interpolation of a planar object with its shape taken into consideration. It applies and extends a shape dependent distance measure between two positions in the context of motion interpolation. Instead of using a fixed reference frame, a shape-dependent inertia frame of reference is used for formulating the distance between positions of a rigid object in a plane. The resulting distance function is then decomposed in two orthogonal directions and is used to formulate an interpolating function for the distance functions in these two directions. This leads to a shape dependent interpolation of translational components of a planar motion. In difference to the original concept of Kazerounian and Rastegar that comes with a shape dependent measure of the angular motion, it is assumed in this paper that the angular motion is shape independent as the angular metric is dimensionless. The resulting distance measure is not only a combination of translation and rotation parameters but also depends on the area moments of inertia of the object. It derives the explicit expressions for decomposing the shape dependent distance in two orthogonal directions, which is then used to obtain shape dependent motion interpolants in these directions. The resulting interpolants have similarities to the well-known spherical linear interpolants widely used in computer graphics in that they are defined using sinusoidal functions instead of linear interpolation in Euclidean space. The path of the interpolating motion can be adjusted by different choice of shape parameters. Examples are provided to illustrate the effect of object shapes on the resulting interpolating motions.

Model-Free 3-D Shape Control of Deformable Objects Using Novel Features Based on Modal Analysis

Shape control of deformable objects is a challenging and important robotic problem. This article proposes a model-free controller using novel 3-D global deformation features based on modal analysis. Unlike most existing controllers using geometric features, our controller employs physically based deformation features designed by decoupling global deformation into low-frequency modes. Although modal analysis is widely adopted in computer vision and simulation, its usage in robotic deformation control is still an open topic. We develop a new model-free framework for the modal-based deformation control. Physical interpretation of the modes enables us to formulate an analytical deformation Jacobian matrix mapping the robot manipulation onto changes of the modal features. In the Jacobian matrix, unknown geometric and physical models of the object are treated as low-dimensional modal parameters, which can be used to linearly parameterize the closed-loop system. Thus, an adaptive controller with proven stability can be designed to deform the object while online estimating the modal parameters. Simulations and experiments are conducted using linear, planar, and volumetric objects under different settings. The results not only confirm the superior performance of our controller, but also demonstrate its advantages over the baseline method.

A general geometric transformation model for line-scan image registration

A reasonable geometric transformation model is the key to image registration. When the relative motion direction between the line-scan camera and the object is strictly parallel to the planar object, it is possible to align the image by using the eight-parameter geometric transformation model of the line-scan image. However, it will be invalid when the relative motion direction is arbitrary. Therefore, a new general geometric transformation model of line-scan images is proposed for line-scan image registration in this paper. Considering the different initial poses and motion directions of the line-scan camera, the proposed model is established based on the imaging model of the line-scan camera. In order to acquire line-scan images to verify the proposed model, a line-scan image acquisition system was built. The method based on feature points is used to register the line-scan images. The experimental results show that the proposed geometric transformation model can align the line-scan image collected under arbitrary relative motion direction, not just the parallel case. Besides, the statistical errors of the image feature point coordinates are the best performance after registration. The accuracy of the registration results is better than that of other existing geometric transformation models, which verifies the correctness and generality of the geometric transformation model of the line-scan camera proposed in this paper.

Observations of the synthesis of straight single wall carbon nanotubes directed by electric fields in an Environmental Transmission Electron Microscope

We report here observations in real time of the aligning effect of electric fields during the synthesis of carbon nanotubes in an environmental transmission electron microscope (ETEM). Growths took place using C2H2 as precursor gas at ∼10−4 mbar, a temperature of ∼700°C and within a micro-capacitor incorporated in a specifically-designed heating micro-chip. Individual nanotubes are easily resolved as they appear as extremely straight lines growing parallel to the electric field. These nanotubes are predominantly Single Wall Carbon Nanotubes (SWNTs). Owing to the very good alignment of nanotubes in the object plane of the microscope we can obtain unprecedented excellent determination of the nanotubes’ growth rates and follow them dynamically. Constant growth rates are observed in most cases but other behaviours are observed such as growth rate acceleration. For low applied voltages the growing nanotubes can cross the gap and connect to the opposite electrode although some are destroyed by mechanical failure or during the contact. For high applied fields and positive biasing allowing Field Emission (FE), the growth is limited within the gap as FE can occur during growth leading to new saturation or destruction processes. These different mechanisms are presented as well as the observed balance between electrostatic and adhesion forces.

Improving gamma camera imaging using parallel jagged hole collimator

Single photon imaging still remains the most commonly used imaging method in nuclear medicine to date, usually employing a gamma camera furnished with a parallel hole (PH) collimator. Using this type of collimator implies that both the size of the field of view (FOV) and the sensitivity are invariant with the distance from the object plane. Otherwise, the spatial resolution is inversely proportional to the distance from the object plane.In the present study, a modified parallel hole design, i.e., the parallel jagged hole (PJH), is introduced with the aim to improve the relationship between the spatial resolution and the sensitivity of a standard PH collimator.Quantitative characteristics of three PJH test samples were assessed experimentally as well as by applying simulation with the help of the MCNP5 code and using analytical approximation. In addition, the overall qualitative imaging performance was evaluated with the help of a custom-built planar phantom. While the sensitivity of one of the PJH test samples was very close to that of the corresponding PH design, its spatial resolution appeared to be superior by some 5–12%. Another test sample that exhibited nearly identical spatial resolution to its reference PH design was found to have approximately 35% higher sensitivity.So far, the experimental results as well as the outcomes obtained by simulation and by analytical approximation were found to be in good agreement among them what suggests that proposed PJH design could improve the imaging quality beyond that of the standard PH collimator.

A multi-scan refinement technique combining cone-beam tomography and laminography

In a fine-focus geometry, for a given detector, the resolution achievable by conventional tomographic region-of-interest (ROI) imaging is limited by the smallest possible distance of the radiation source from the rotation axis, i.e., the radius of the smallest cylinder about the rotation axis that encloses the object. In situations where the specimen to be imaged is irregularly shaped, or the ROI is off-centre, higher magnification can only be achieved from a limited range of angles, (possibly in a separate scan), and a tomographic reconstruction technique able to incorporate this additional data would be advantageous. Here we present such a technique for imaging planar (or laminar) objects based on a combination of multiple tomography and laminography scans with increasing magnification that employ helical and planar source trajectories respectively. Relative to laminography, this hierarchical combination improves depth resolution, (longitudinal direction), as well as reducing imaging artefacts. Relative to full-field tomography the proposed method increases resolution, particularly in the plane of the specimen, (transverse direction). The foundation of the technique is a generalisation of accelerated multi-grid tomographic reconstruction methods to the case of multiple independent collections of radiographs. Here we first demonstrate the concepts and performance of this technique through a simulated example. We then demonstrate the successful application of the method experimentally to a thin rock section and a printed circuit board.

Investigation of the non-contact flip motion of a planar levitated object using the acoustic jumping phenomenon

Investigation of the non-contact flip motion of a planar levitated object using the acoustic jumping phenomenon

An Improved Four-Pin Gripper for Robust 2.5-D Form-Closure Grasp

The four-pin gripper is an ideal end-effector to achieve form-closure grasps, which is especially useful in scenarios where a stable grasp is necessary. In this article, we propose an improved parallel four-pin gripper design. Compared with the previous designs, the new design achieves more planar configurations while introducing only one more actuator, thus enlarging the possibility of the gripper to stably grasp. Based on the improved design, we extend the environment constraint-based form-closure grasping point search algorithm to find the optimal parameters for the improved four-pin gripper. Furthermore, we apply an inverse kinematics-based planning method to drive the gripper from any initial state to a form-closure state. The simulation and experiment demonstrate that, compared with the previous designs, the improved design can achieve stable grasping for a wider range of planar objects.

HoloForkNet: Digital Hologram Reconstruction via Multibranch Neural Network

Reconstruction of 3D scenes from digital holograms is an important task in different areas of science, such as biology, medicine, ecology, etc. A lot of parameters, such as the object’s shape, number, position, rate and density, can be extracted. However, reconstruction of off-axis and especially inline holograms can be challenging due to the presence of optical noise, zero-order image and twin image. We have used a deep-multibranch neural network model, which we call HoloForkNet, to reconstruct different 2D sections of a 3D scene from a single inline hologram. This paper describes the proposed method and analyzes its performance for different types of objects. Both computer-generated and optically registered digital holograms with resolutions up to 2048 × 2048 pixels were reconstructed. High-quality image reconstruction for scenes consisting of up to eight planes was achieved. The average structural similarity index (SSIM) for 3D test scenes with eight object planes was 0.94. The HoloForkNet can be used to reconstruct 3D scenes consisting of micro- and macro-objects.

Reimagining Affection in a Changing Shanghai

The article examines the dynamics of space surrounding Shanghai’s rampant urban change as experienced by the Chinese artistic duo known as Birdhead. Underpinned by the conceptual framework of the “affective turn”, this study reflects upon and addresses how the photographer’s chaotic photo-essay of Shanghai’s new state housing (Xincun, New Village, 2008) can function as a nexus of place-making. With a claim to impetuous emotion in his works, Birdhead’s contemporary photography pervades a plane of subjects, objects, and affections, in which the city is imagined and experienced as space-body performativity. Understanding Birdhead’s everyday urban practices as performative, we claim that the visual performance of these photographs not just materially shapes the bodies, but also acts as a rhizomatic catalyst for both things-in-themselves and webs of social affection inside and outside Shanghai. As a contribution, this article’s theoretical application to Birdhead’s everyday networks of unruly and frenzied emotional tactics challenges the official formulation of realism. More importantly, their contemporary photography apprehends and territorializes elements of anarchy, at the very same time deterritorializing the omnipresent affective strategies of a propagandistic post-socialist apparatus that pressures the positive over “other” emotional representations of Shanghai.

Dual spectral limited-angle CT imaging regularized by edge-preserving diffusion and smoothing.

Limited-angle CT scan is an effective way for nondestructive inspection of planar objects, and various methods have been proposed accordingly. When the scanned object contains high-absorption material, such as metal, existing methods may fail due to the beam hardening of X-rays. In order to overcome this problem, we adopt a dual spectral limited-angle CT scan and propose a corresponding image reconstruction algorithm, which takes the polychromatic property of the X-ray into consideration, makes basis material images free of beam hardening artifacts and metal artifacts, and then helps depress the limited-angle artifacts. Experimental results on both simulated PCB data and real data demonstrate the effectiveness of the proposed algorithm.

Chemically Customizing Mechanical Properties and Optical Transparency in Underwater Superoleophobic Coating

AbstractThe inherent ability of bio‐inspired underwater superoleophobicity to prevent oil/oily fouling underwater makes it appropriate for a wide range of applications related to environmental remediation, bio‐adhesion, microfluidics, chemical sensing, etc.; however, the co‐association of mechanical durability and optical transparency is essential for realistic performance. While the design of mechanically durable and absolutely optically transparent underwater superoleophobic coating remains challenging, here, a covalently cross‐linked and chemically reactive sol‐gel conversion process is introduced through 1,4‐conjugate addition reaction to achieve a substrate‐independent and tolerant coating for orthogonally modulating the underwater oil wettability, optical transparency, and even mechanical properties of highly deformable porous and fibrous substrates. The post‐modification of residual chemical reactivity in the prepared coating allows to embed underwater superoleophobicity, and the β‐amino‐ester‐cross‐links improve the mechanical property of selected deformable substrates. Moreover, it displayed unperturbed performance even after prolonged (30 days) exposures in practically relevant chemically harsh aquatic conditions—including extremes of pH, artificial seawater, surfactant contaminated water, etc. The approach is successfully applied to coat various substrates—including porous, fibrous, and planar objects, and it would be useful in protecting various relevant marine infrastructures from oil/oily fouling, and various other potential applications.

Robo-vision! 3D mesh generation of a scene for a robot for planar and non-planar complex objects.

This paper presents a novel architecture to generate a world model in terms of mesh from a continuous image stream with depth information extracted from a robot's ego-vision camera. We propose two algorithms for planar and non-planar mesh generation. A Cartesian grid-based mesh fitting algorithm is proposed for mesh generation of planar objects. For mesh generation of non-planar objects, we propose a Self Organization Map based algorithm. The proposed algorithm better approaches the boundary and overall shape of the objects compared to State-Of-the-Art (SOA). Extensive experiments done on three public datasets show that our method surpasses SOA both qualitatively and quantitatively.

Certified grasping

This paper studies the robustness of grasping in the frictionless plane from a geometric perspective. By treating grasping as a process that shapes the free-space object over time, we define three types of certificates to guarantee success of a grasp: (a) invariance under an initial set, (b) convergence toward a goal grasp, and (c) observability over the final object pose. We develop convex-combinatorial models for each of these certificates, which can be expressed as simple semi-algebraic relations under mild-modeling assumptions, such as point-fingers and frictionless contact. By leveraging these models to synthesize certificates, we optimize certifiable grasps of planar objects composed as a union of convex polygons, using manipulators described as point-fingers. We validate this approach in simulations by grasping random polygons, and with real sensorless grasps of several objects.