Virtual Plane Research Articles

Endoscopic Treatment of Adversely Located Osteomas of the Frontal Sinus

We assess the utility and limitations of an endoscopic technique in the treatment of osteomas that are considered difficult to manage endoscopically, ie, those located superiorly or laterally in the frontal sinus, extending beyond a virtual plane through the lamina papyracea, and we describe the principles of a surgical technique that facilitates removal of such tumors. We performed a retrospective study on 8 patients with symptomatic frontal sinus osteomas, including tumors extending past the commonly recognized limits of endoscopic resection because of their size or site of attachment. All tumors were removed by a purely transnasal endoscopic approach. No major complications were observed during or after the operation. All patients experienced improvement or total regression of their symptoms. With appropriate instruments and specific endoscopic techniques, it is possible to resect osteomas that not long ago were deemed inaccessible to endoscopic surgeons. The commonly recognized limits of endoscopic treatment of such tumors may be exceeded in some cases; however, favorable anatomic conditions are decisive for a successful operation.

A Laser Projection Device for Locating Points on the Plane Object

Digital image processing technology can extract the main feature of an image. In order to achieve the interaction between virtual points and plane objects, we propose the equipment for indicating points on the plane object using laser projection. We designed the equipment with a bracket, stepper motor, two-dimensional turntable, PC control unit, and a laser pointer. Next, we analyzed the mathematical model of the equipment and developed an algorithm for solving the motor rotation angle. Finally, we verified our design with an image. Here, we develop a system that can control a laser projection to a specified location by adjusting coordinates of virtual points on a computer.

Enhancing the pictorial content of digital holograms at 100 frames per second

We report a low complexity, non-iterative method for enhancing the sharpness, brightness, and contrast of the pictorial content that is recorded in a digital hologram, without the need of re-generating the latter from the original object scene. In our proposed method, the hologram is first back-projected to a 2-D virtual diffraction plane (VDP) which is located at close proximity to the original object points. Next the field distribution on the VDP, which shares similar optical properties as the object scene, is enhanced. Subsequently, the processed VDP is expanded into a full hologram. We demonstrate two types of enhancement: a modified histogram equalization to improve the brightness and contrast, and localized high-boost-filtering (LHBF) to increase the sharpness. Experiment results have demonstrated that our proposed method is capable of enhancing a 2048x2048 hologram at a rate of around 100 frames per second. To the best of our knowledge, this is the first time real-time image enhancement is considered in the context of digital holography.

Precise X-ray and video overlay for augmented reality fluoroscopy

The camera-augmented mobile C-arm (CamC) augments any mobile C-arm by a video camera and mirror construction and provides a co-registration of X-ray with video images. The accurate overlay between these images is crucial to high-quality surgical outcomes. In this work, we propose a practical solution that improves the overlay accuracy for any C-arm orientation by: (i) improving the existing CamC calibration, (ii) removing distortion effects, and (iii) accounting for the mechanical sagging of the C-arm gantry due to gravity. A planar phantom is constructed and placed at different distances to the image intensifier in order to obtain the optimal homography that co-registers X-ray and video with a minimum error. To alleviate distortion, both X-ray calibration based on equidistant grid model and Zhang's camera calibration method are implemented for distortion correction. Lastly, the virtual detector plane (VDP) method is adapted and integrated to reduce errors due to the mechanical sagging of the C-arm gantry. The overlay errors are 0.38±0.06mm when not correcting for distortion, 0.27±0.06mm when applying Zhang's camera calibration, and 0.27±0.05mm when applying X-ray calibration. Lastly, when taking into account all angular and orbital rotations of the C-arm, as well as correcting for distortion, the overlay errors are 0.53±0.24mm using VDP and 1.67±1.25mm excluding VDP. The augmented reality fluoroscope achieves an accurate video and X-ray overlay when applying the optimal homography calculated from distortion correction using X-ray calibration together with the VDP.

The University Münster model surgery system for Orthognathic surgery. Part I – The idea behind

BackgroundWe describe a procedure for diagnosis and planning for orthognatic surgery based on international standards. A special 2D planning based on lateral cephalograms (Axis Orbital Marker Lines System) realize a transmission to the SAM 2P articulator (3D) by means of the Axis Orbital Plane.MethodsFormer intraoperative measurement of the average height of the LeFort I osteotomy plane relative to the molar occlusal plane allow to construct a virtual osteotomy plane in the lateral cephalogram. This is the basis for the development of the Axis Orbital Marker Lines System (AO-MLS).ResultsThe AO-MLS is presented graphically, and in detail, with construction guidelines. The system could be integrated into various lateral cephalometric analysis- and surgical prediction schemes. It forms the basis for a standardized transfer of the 2D planning to the 3D planning in the articulator, and vice versa. This procedure makes it possible to generate surgical planning protocols based on the model surgery, which represent the dislocations in the proximity of the real osteotomy planes.ConclusionsThe Axis Orbital Marker Lines System (software component) in conjunction with the University Münster Model Surgery System (hardware system) increases the predictability of model operations in orthognathic surgery.

Visual Servoing Path Planning for Cameras Obeying the Unified Model

This paper proposes a path planning visual servoing strategy for a class of cameras that includes conventional perspective cameras, fisheye cameras and catadioptric cameras as special cases. Specifically, these cameras are modeled by adopting a unified model recently proposed in the literature and the strategy consists of designing image trajectories for eye-in-hand robotic systems that allow the robot to reach a desired location while satisfying typical visual servoing constraints. To this end, the proposed strategy introduces the projection of the available image features onto a virtual plane and the computation of a feasible image trajectory through polynomial programming. Then, the computed image trajectory is tracked by using an image-based visual servoing controller. Experimental results with a fisheye camera mounted on a 6-d.o.f. robot arm are presented in order to illustrate the proposed strategy.

손동작을 이용한 상호작용 증강현실 시스템

본 논문에서는 컴퓨터 비전 기술 기반으로 사용자의 손 움직임과 가상객체 사이의 자연스러운 상호작용을 위한 증강현실 시스템을 제안한다. 기존의 증강현실 시스템은 마커를 이용하거나 트랙커 같은 센서를 직접 조작해야 했기 때문에 사용자에게 불편함을 제공한다. 우리는 이러한 문제점을 해결하기 위해서 손 움직임을 증강현실 시스템에 적용한다. 또한 가상객체의 움직임에 물리적 현상을 적용하여 현실감을 부여한다. 제안한 시스템은 마커를 이용하여 기하학적 정보를 얻어 가상의 공이 움직이는 가상공간, 벽돌 등의 시스템 환경을 구성하였으며, 사용자의 손 움직임은 테이핑을 통하여 특징점을 추출하여 정보를 얻는다. 이 특징점을 이용하여 손 위에 가상 평면을 안정적으로 정합한다. 가상의 공의 움직임은 포물선 방정식을 이용하여 기본적으로 포물선 움직임을 보이고, 평면 또는 벽돌에 충돌이 발생할 경우에는 가상 공의 위치와 평면의 법선벡터를 이용하여 가상 공의 움직임을 보였다. 실험을 통해 충돌 시 발생되는 잘못된 공의 위치에 대해 보정되는 과정을 보였고, 증강된 가상객체의 떨림과 수행속도에 대해 마커를 이용한 시스템과 비교하여 제안한 시스템으로 대체할 수 있다는 것을 확인하였다. In this paper, We propose Augmented Reality (AR) System for the interaction between user's hand motion and virtual object motion based on computer vision. The previous AR system provides inconvenience to user because the users have to control the marker and the sensor like a tracker. We solved the problem through hand motion and provide the convenience to the user. Also the motion of virtual object using a physical phenomenon gives a reality. The proposed system obtains geometrical information by the marker and hand. The system environments like virtual space of moving virtual ball and bricks are made by using the geometrical information and user's hand motion is obtained from the hand's information with extracted feature point through the taping hand. And it registers a virtual plane stably by getting movement of the feature points. The movement of the virtual ball basically is parabolic motion with a parabolic equation. When the collision occurs either the planes or the bricks, we show movement of the virtual ball with ball position and normal vector of plane and the ball position is faulted. So we showed corrected ball position through experiment. and we proved that this system can replaced the marker system to compare to jitter of augmented virtual object and progress speed with it.

Omni-Directional Gait of Multi-Legged Robot on Rough Terrain by Following the Virtual Plane

This paper proposes a simple gait algorithm for multilegged robots on slopes or rough terrain. This algorithm enables a robot follow a virtual plane defined by grounding points of the legs. The robot does not recognize the surrounding rough terrain. This proposed algorithm has been applied to an actual robot and proven. The robot has a touch sensor on the tip of each leg. The sensors detect contact with the ground, allowing the leg to be planted stably. When the robot moves over rough terrain, the robot body inclines as if becoming parallel to the virtual plane that is defined by the support points of the legs. The ASTERISK robot to which the algorithm has been applied has six limbs that radiate out in six directions, giving it rotational symmetry. Each leg of the robot has a cylindrical working space; the robot can move omnidirectionally without changing its posture. The movement algorithm is an easy, single-pattern operation that maintains a stable state at all times, and the robot can move without high-speed, real-time processing. The operation and effectiveness of this algorithm are verified on a slope and on steps through the experiment.

Three-dimensional reconstruction based on multiple virtual planes by using fusion-based camera network

A novel approach for three-dimensional (3D) volumetric reconstruction of an object inside a scene is proposed. A camera network is used to observe the scene. Each camera within the network is rigidly coupled with an Inertial Sensor (IS). A virtual camera is defined for each IS-camera couple using the concept of infinite homography, by fusion of inertial and visual information. Using the inertial data and without planar ground assumption, a set of virtual horizontal planes are defined. The intersections of these inertial-based virtual planes with the object are registered using the concept of planar homography. Moreover a method to estimate the translation vectors among virtual cameras is proposed, which just needs the relative heights of two 3D points in the scene with respect to one of the cameras and their correspondences on the image planes. Different experimental results for the proposed 3D reconstruction method are provided on two different types of scenarios. In the first type, a single IS-camera couple is used and placed in different locations around the object. In the second type, the 3D reconstruction of a walking person (dynamic case) is performed where a set of installed cameras in a smart-room is used for the data acquisition. Moreover, a set of experiments are simulated to analyse the accuracy of the translation estimation method. The experimental results show the feasibility and effectiveness of the proposed framework for the purpose of multi-layer data registration and volumetric reconstruction.

Dual-polarity plasmonic metalens for visible light

Surface topography and refractive index profile dictate the deterministic functionality of a lens. The polarity of most lenses reported so far, that is, either positive (convex) or negative (concave), depends on the curvatures of the interfaces. Here we experimentally demonstrate a counter-intuitive dual-polarity flat lens based on helicity-dependent phase discontinuities for circularly polarized light. Specifically, by controlling the helicity of the input light, the positive and negative polarity are interchangeable in one identical flat lens. Helicity-controllable real and virtual focal planes, as well as magnified and demagnified imaging, are observed on the same plasmonic lens at visible and near-infrared wavelengths. The plasmonic metalens with dual polarity may empower advanced research and applications in helicity-dependent focusing and imaging devices, angular-momentum-based quantum information processing and integrated nano-optoelectronics.

Investigation of the collapse of laser-induced bubble near a cone boundary

The effect of the cone boundary on collapse of the laser-induced bubble is investigated under the assumption of virtual plane, and the methods of shadow photography, optical beam deflection and simulation are also used to obtain the effect of cone angle on the bubble dynamics. The results indicate that the effects of the cone angle on the shape of bubble, collapse time and the formation of liquid jet are obvious. The degree of departure of bubble shape from spherical shape and the collapse time are found to increase with the increase of cone angle, and the valid liquid jet is able to form at a lager cone angle. The experimental value and theoretical value of collapse are in good agreement with each other, and the assumption of virtual plane and the modification of dimensionless distance parameter proposed in this study are valid.

Measurement of LED Spatial Intensity Distribution Using Imaging

This paper, through studying of LED luminescence properties, presents a fast measurement method and device of LED sources spatial intensity distribution. This method is based on planar imaging, and it has significant merits of fast, easy operated, informative and real–time. The basic structure is LED luminous energy converges on image space through optical lens of a certain numerical aperture(NA). In image space, the energy on the defocused plane is collected with the imaging detector. Then, calculating energy distribution on object virtual plane from that on the image space defocused plane through imaging relationship. Thus, each point of the LED luminous intensity distribution on object virtual plane can be calculated. Tracepro simulation software is used to simulate energy distribution of the model, and the corresponding data analysis shows that planar imaging can accurately reflect the distribution of the LED light. This method has practical meanings for luminous flux measurement of some LEDs.

Measurement of LED Spatial Intensity Distribution Using Imaging

This paper, through studying of LED luminescence properties, presents a fast measurement method and device of LED sources spatial intensity distribution. This method is based on planar imaging, and it has significant merits of fast, easy operated, informative and real–time. The basic structure is LED luminous energy converges on image space through optical lens of a certain numerical aperture(NA). In image space, the energy on the defocused plane is collected with the imaging detector. Then, calculating energy distribution on object virtual plane from that on the image space defocused plane through imaging relationship. Thus, each point of the LED luminous intensity distribution on object virtual plane can be calculated. Tracepro simulation software is used to simulate energy distribution of the model, and the corresponding data analysis shows that planar imaging can accurately reflect the distribution of the LED light. This method has practical meanings for luminous flux measurement of some LEDs.

Random-phase-shift Fizeau interferometer

A new and potentially cost efficient kind of vibration-tolerant surface measurement interferometer based on the Fizeau-principle is demonstrated. The crucial novelty of this approach is the combination of two optoelectronic sensors: an image sensor with high spatial resolution and an arrangement of photodiodes with high temporal resolution. The photodiodes continuously measure the random-phase-shifts caused by environmental vibrations in three noncollinear points of the test surface. The high spatial resolution sensor takes several "frozen" images of the test surface by using short exposure times. Under the assumption of rigid body movement the continuously measured phase shifts of the three surface points enable the calculation of a virtual plane that is representative for the position and orientation of the whole test surface. For this purpose a new random-phase-shift algorithm had to be developed. The whole system was tested on an optical table without vibration isolation under the influence of random vibrations. The analysis of the root-mean-square (RMS) over ten different measurements shows a measurement repeatability of about 0.004 wave (approximately 2.5 nm for 632.8 nm laser wavelength).

Accurate calibration method for 3D freehand ultrasound probe using virtual plane

In this paper a new, easy-to-manufacture and easy-to-use ultrasound (US) probe calibration phantom for 3D freehand scanning is presented and evaluated, together with a new method for achieving an accurate and user-robust calibration using virtual plane. The phantom allows the optically tracked US probe to perform two rotations and two translations while keeping the image of a tensioned wire in the image plane. This approach allows obtaining a sharp image of the wire independently from the probe pose. The virtual plane allows the calibration algorithm to converge minimizing the required number of US probe tracked poses. The US image and position data are synchronized via a CORBA interface, created within the Image Guided Surgery Toolkit (IGSTK) framework. The calibration algorithm and the calibration protocol were evaluated in a set of experiments carried out by different test-users. The calibration method proved to be accurate and precise: 3D point reconstruction accuracy resulted 0.2 mm as mean value, while the precision was 0.4 mm as standard deviation. The technique showed to be suitable for medical applications from morphological diagnosis to intraoperative surgical planning adaption.

An Evaluation of Face-Bow Transfer for the Planning of Orthognathic Surgery

The purpose of this study was to evaluate the error magnitude in the clinical application of face-bow devices. Technical and methodologic inaccuracies, as well as deviations from reference planes, were determined. The presented method is part of a 3-dimensional virtual planning procedure for orthognathic surgery and included 15 patients with dentoskeletal deformities. Cone beam computed tomography datasets obtained from patients with a referenced face-bow plane and a centric registration splint were matched with cone beam computed tomography datasets of the registered plaster model of the maxilla mounted in an articulator. To assess potential sources of methodologic errors, angulations were measured between the virtual face-bow plane and the horizontal cross bar of the virtual articulator. To evaluate the reproducibility of the anatomic reference plane, angulations between the Frankfort plane and the horizontal cross bar of the articulator were measured. Statistical significance was set at P < .05 and tested by univariate analysis of variance. Technical and methodologic errors showed a mean deviation of 3.5°, with a median of 3.6° and SD of 2.7°. The values did not reach statistical significance (P = .1). However, there was a significant error (P < .05) in determining the position of the anatomic reference plane by face-bow transfer. The mean deviation was 7.7° (values ranged between 1.2° and 18.9°), with a median of 6.7° and SD of 5.3°. In this study the traditional use of face-bow devices showed inaccuracies in model mounting as well as in assignment of anatomic reference planes. Three-dimensional virtual computer-assisted planning seems to be more accurate than conventional methods.

Optimized Design for Cockpit Protective Glass Construction against High Power Microwave Using Genetic Algorithm

According to main challenges to aircraft protection against high power microwave (HPM), the formula of electromagnetic transmission rate and reflectivity both for the perpendicularly and parallely polarized incident field are modified and simplified, a shielded cockpit glass construction is designed by a new optimized method on genetic algorithm, and protective efficiency analysis on military aircraft’s cockpit against HPM is carried out on a virtual 3D plane, airborne equipments and pilot model with a scale of 1:1. The verification simulation tests show the optimized construction has good protective efficiency in the range of carrier frequencies between 1-20 GHz, and protective intensity does not exceed limits of relevant international standard.

Fast and automatic image-based registration of TLS data

The fast and automatic registration of laser scanner data is of great interest in photogrammetric research. Recent developments show that for registration purposes characteristic 3D points can be extracted from the measured laser data, where the data are also represented as image. In this paper, radiometric and geometric information derived from TLS data are utilized for estimating the transformation parameters between two unregistered point clouds. After the extraction of characteristic 2D points based on SIFT features, these points are projected into 3D space by using interpolated range information. From these 3D conjugate points and their corresponding 2D projections onto a virtual plane 3D-to-2D correspondences are established. The fast, accurate and robust RANSAC-based registration scheme including the EPnP algorithm provides a framework to estimate the coarse transformation parameters from these 3D-to-2D correspondences. The coarse estimates are further refined by a single step outlier removal to gain a higher accuracy by introducing additional geometric constraints. These new constraints are based on 3D-to-3D correspondences which are much stronger than the 3D-to-2D correspondences alone. It will be shown that the presented approach is successfully applied to a benchmarked data set with millions of points resulting in a fast and accurate estimation of the transformation parameters with a processing speed of several seconds on a standard PC and an accuracy in the low centimeter range.

Coal powder measurement by digital holography with expanded measurement area

The field of view of digital in-line holography for flow field diagnostics is restricted to a small volume due to the finite size and the low spatial resolution of the available CCD. Expansion of the measurement cross section of digital holographic particle image velocimetry was investigated with a lens-based holography configuration. By sampling the chirp signal in the center lobe completely and undersampling the chirp signal in the second- and higher-order lobes by a magnified virtual recording plane produced by an imaging camera lens, the field of view is expanded. Simulation results show that the three-dimensional (3D) location and size of the relatively large particle can be reconstructed with good accuracy. A digital holographic particle image velocimetry system was established for coal particle flow field diagnostics. Compared with the lensless configuration, the field of view of the digital holography system was enlarged 1.9 times, up to 2.78 cm × 2.78 cm × 3 cm. The 3D location, size distribution, and the 3D vector field of coal powder were obtained. The results show that the application of digital in-line holography to measure large particle flow field is feasible.

Field Test on Conversion of Natural Watershed into Kinematic Wave Rectangular Plane

AbstractConversion of a natural watershed into its equivalent kinematic wave rectangular plane has long been a concern in the practice of storm water numerical simulations. Based on the principles of mass and energy, the actual watershed and its virtual kinematic wave plane can be related by the watershed shape factor that involves the waterway length and slope and watershed area. In this study, two dimensionless watershed shape functions are derived to use parabolic function and trigonometric sine curve for watershed conversion. These two watershed shape functions produce good agreements with the maximum overland flow length method for hypothetical square watersheds. Also, these two watershed shape functions are able to reproduce similar kinematic wave plane widths as reported in a calibrated model. Furthermore, in this study, these two watershed shape functions are tested by nine observed rainfall events and three levels of modeling details. These 54 case studies reveal that the parabolic shape function...