Showing papers on "Image plane published in 2007"

Projection optical system and method for photolithography and exposure apparatus and method using same

Abstract: Optical Projection System and Method for Photolithography. A lithographic immersion projection system and method for projecting an image at high resolution over a wide field of view. The projection system and method include a final lens which decreases the marginal ray angle of the optical path before light passes into the immersion liquid to impinge on the image plane.

Level Set Methods

Abstract: The shape of a real-world object can be represented by a parametric or a nonparametric contour in the image plane. The parametric contour representation is referred to as an explicit representation, and is defined in the Lagrangian coordinate system. In this coordinate system, two different objects have two different representations stemming from the different sets of control points that define the object contours. The control points constitute the finite elements, which is a common formalism used to represent shapes in the Lagrangian coordinates. In contrast to the parametric Lagrangian representation, the nonparametric representation defines the object contour implicitly in the Eulerian coordinates, which remains constant for two different objects. The level set method is a nonparametric representation defined in the Eulerian coordinate system and is used commonly in the computer vision community to represent the shape of an object in an image. The level set method has been introduced in the field of fluid dynamics by the seminal work of Osher and Sethian in 1988. After its introduction, it has been applied successfully in the fields of fluid mechanics, computational physics, computer graphics, and computer vision. In the level set representation, the value of each grid point (pixel) is set traditionally to the Euclidean distance between the grid point and the contour. Hence, moving the contour from one configuration to the other is achieved by changing the distance values in the grid points. During its motion, the contour can change its topology implicitly by splitting into two disjoint contours or by merging from two contours to one. The implicit nature of the representation becomes essential to handle the topology changes for the case when an initial configuration is required to solve a time-dependent problem. Upon initialization, the level set converges to a solution by re-evaluating the values at the grid points iteratively. This iterative procedure is referred to as the contour evolution. Keywords: segmentation; contour tracking; implicit representation; topology changes; splitting; merging; contour representation; fast marching

The background oriented schlieren technique: sensitivity, accuracy, resolution and application to a three-dimensional density field

Abstract: Three-dimensional density information of a double free air jet was acquired using optical tomography. The projections of the density field were measured using the background oriented schlieren method (BOS). Preceding the free jet measurements, the sensitivity, accuracy and resolution of the BOS method were investigated. The sensitivity depends mostly on the focal length of the lens used, the relative position of the object between camera and background and the smallest detectable shift in the image plane. The accuracy was found to be sufficiently high to apply a tomographic reconstruction process. The resolution is determined by the transfer function of the BOS-method. It is not constant and depends on the size of the interrogation windows used for the cross-correlation-algorithm. The reconstruction of the free jet was computed, using filtered back projection. The reconstructed 3D density field shows with good resolution the typical diamond structure of the density distribution in under-expanded free jets.

Three-Dimensional Shape Knowledge for Joint Image Segmentation and Pose Tracking

Abstract: In this article we present the integration of 3-D shape knowledge into a variational model for level set based image segmentation and contour based 3-D pose tracking. Given the surface model of an object that is visible in the image of one or multiple cameras calibrated to the same world coordinate system, the object contour extracted by the segmentation method is applied to estimate the 3-D pose parameters of the object. Vice-versa, the surface model projected to the image plane helps in a top-down manner to improve the extraction of the contour. While common alternative segmentation approaches, which integrate 2-D shape knowledge, face the problem that an object can look very differently from various viewpoints, a 3-D free form model ensures that for each view the model can fit the data in the image very well. Moreover, one additionally solves the problem of determining the object's pose in 3-D space. The performance is demonstrated by numerous experiments with a monocular and a stereo camera system.

Probing the submillimetre number counts at f(850um) < 2mJy

Abstract: We have conducted a submillimetre mapping survey of faint, gravitationally lensed sources, where we have targeted twelve galaxy clusters and additionally the NTT Deep Field. The total area surveyed is 71.5 arcmin^2 in the image plane; correcting for gravitational lensing, the total area surveyed is 40 arcmin^2 in the source plane for a typical source redshift z=2.5. In the deepest maps, an image plane depth of 1sigma r.m.s. ~0.8 mJy is reached. This survey is the largest survey to date to reach such depths. In total 59 sources were detected, including three multiply-imaged sources. The gravitational lensing makes it possible to detect sources with flux density below the blank field confusion limit. The lensing corrected fluxes ranges from 0.11 mJy to 19 mJy. After correcting for multiplicity there are 10 sources with fluxes 50 per cent) to the integrated background arises from sources with fluxes S(850) between 0.4 and 2.5 mJy, while the bright sources S(850) > 6mJy contribute only 10 per cent.

Passivity-Based Dynamic Visual Feedback Control for Three-Dimensional Target Tracking: Stability and $L_{2}$ -Gain Performance Analysis

Abstract: This paper investigates vision-based robot control based on passivity for three-dimensional (3-D) target tracking. First, using standard body-attached coordinate frames (the world frame, camera frame, and object frame), we represent the relative position and orientation between a moving target and a camera as an element of SE(3). Using this representation we derive a nonlinear observer to estimate the relative rigid body motion from the measured camera data. We then establish the relationship between the estimation error in a 3-D workspace and in the image plane. We show passivity of the dynamic visual feedback system by combining the passivity of both the visual feedback system and the manipulator dynamics which allows us to prove stability in the sense of Lyapunov for the full 3-D dynamic visual feedback system. The L2 -gain performance analysis, which deals with the disturbance attenuation problem, is then considered via dissipative systems theory. Finally, experimental results are presented to verify the stability and L2-gain performance of the dynamic visual feedback system

An algorithm for extrinsic parameters calibration of a camera and a laser range finder using line features

Abstract: This paper presents an effective algorithm for calibrating the extrinsic parameters between a camera and a laser range finder whose trace is invisible. On the basis of an analysis of three possible features, we propose to design a right-angled triangular checkerboard and to employ the invisible intersection points of the laser range finder's slice plane with the edges of the checkerboard to set up the constraints equations. The extrinsic parameters are then calibrated by minimizing the algebraic errors between the measured intersections points and their corresponding projections on the image plane of the camera. We compared our algorithm with the existing methods by both simulations and the real data of a stereo measurement system. The simulation and experimental results confirmed that the proposed algorithm can yield more accurate results.

Closed loop, DM diversity-based, wavefront correction algorithm for high contrast imaging systems

Abstract: High contrast imaging from space relies on coronagraphs to limit diffraction and a wavefront control systems to compensate for imperfections in both the telescope optics and the coronagraph. The extreme contrast required (up to 10(exp -10) for terrestrial planets) puts severe requirements on the wavefront control system, as the achievable contrast is limited by the quality of the wavefront. This paper presents a general closed loop correction algorithm for high contrast imaging coronagraphs by minimizing the energy in a predefined region in the image where terrestrial planets could be found. The estimation part of the algorithm reconstructs the complex field in the image plane using phase diversity caused by the deformable mirror. This method has been shown to achieve faster and better correction than classical speckle nulling.

A generic fisheye camera model for robotic applications

Abstract: Omnidirectional cameras have a wide field of view and are thus used in many robotic vision tasks. An omnidirectional view may be acquired by a fisheye camera which provides a full image compared to catadioptric visual sensors and do not increase the size and the weakness of the imaging system with respect to perspective cameras. We prove that the unified model for catadioptric systems can model fisheye cameras with distortions directly included in its parameters. This unified projection model consists on a projection onto a virtual unitary sphere, followed by a perspective projection onto an image plane. The validity of this assumption is discussed and compared with other existing models. Calibration and partial Euclidean reconstruction results help to confirm the validity of our approach. Finally, an application to the visual servoing of a mobile robot is presented and experimented.

Dynamic Visual Tracking for Manipulators Using an Uncalibrated Fixed Camera

Abstract: This paper presents a new controller for controlling a number of feature points on a robot manipulator to trace desired trajectories specified on the image plane of a fixed camera. It is assumed that the intrinsic and extrinsic parameters of the camera are not calibrated. A new adaptive algorithm is developed to estimate the unknown parameters online, based on three original ideas. First, we use the pseudoinverse of the depth-independent interaction matrix to map the image errors onto the joint space of the manipulator. By eliminating the depths in the interaction matrix, we can linearly parameterize the closed-loop dynamics of the manipulator. Second, to guarantee the existence of the pseudoinverse, the adaptive algorithm introduces a potential force to drive the estimated parameters away from the values that result in a singular Jacobian matrix. Third, to ensure that the estimated parameters are convergent to their true values up to a scale, we combine the Slotine-Li method with an online algorithm for minimizing the error between the estimated projections and real image coordinates of the feature points. We have proved asymptotic convergence of the image errors to zero by the Lyapunov theory based on the nonlinear robot dynamics. Experiments have been carried out to verify the performance of the proposed controller.

Method and apparatus for controlling user interface of electronic device using virtual plane

Abstract: Provided is a method and apparatus for controlling a user interface (UI) of an electronic device by using a specific region of a virtual plane. In the method, the virtual plane is initialized according to spatial coordinates of two or more images detected by using locations of the images displayed in an image display unit of a first image capture device and an image display unit of a second image capture device. Furthermore, the location of a marker is determined and is indicated by a specific image on the virtual plane. Furthermore, a screen pointer corresponding to the marker is displayed at a position where the marker is located in an image display unit corresponding to the virtual plane. Furthermore, a menu of the electronic device is selected which is pointed to by the screen pointer while moving the marker. Accordingly, a user can conveniently control the UI of the electronic device by performing a simple operation.

Light field microscope with lenslet array

Abstract: A light field microscope incorporating a lenslet array at or near the rear aperture of the objective lens. The microscope objective lens may be supplemented with an array of low power lenslets which may be located at or near the rear aperture of the objective lens, and which slightly modify the objective lens. The result is a new type of objective lens, or an addition to existing objective lenses. The lenslet array may include, for example, 9 to 100 lenslets (small, low-power lenses with long focal lengths) that generate a corresponding number of real images. Each lenslet creates a real image on the image plane, and each image corresponds to a different viewpoint or direction of the specimen. Angular information is recorded in relations or differences among the captured real images. To retrieve this angular information, one or more of various dense correspondence techniques may be used.

Electronic camera and image processing apparatus

Abstract: An electronic camera includes an image pickup device, a memory, a face detecting section, a face recognizing section, and an object specifying section. The image pickup device photo-electrically converts an image of an object into an electric signal and generates an image signal as the electric signal. The memory has recorded registration data representing characterizing points of faces as recognizing targets. The face detecting section detects face areas in a shooting image plane based on the image signal and extracts characterizing points of faces of objects from the face areas. The face recognizing section determines whether or not the face areas are the recognizing targets based on data of the characterizing points corresponding to the face areas and on the registration data. The object specifying section specifies as a main object an object present on nearest side of the electronic camera of objects as the recognizing targets.

Real-time image plane full-color and full-parallax holographic video display system

Abstract: For practical holographic video display, it is important to generate holographic fringes as fast as possible. It is also important to display the full-color image with a simple display system. In our previous study, a full-color hologram was realized as a rainbow hologram, which discards the vertical parallax to reduce computation complexity. Its color reproduction, however, is not enough. Since this hologram uses the horizontal slit, proper color reproduction can be obtained only from a narrow viewing area in the vertical direction. In contrast, the image hologram provided a good contrast image, although it had only a single color. Also, the image hologram has full-parallax information. In this work, we investigate the image hologram for fast calculation and the display optics for full-color holograms with full parallax. Since image points are located close to the hologram, the required computation area of the image hologram becomes much smaller than that of the entire hologram. Therefore, vastly improved computational speed is obtained. The full-color hologram is displayed on a holographic video display system, which uses part of the original optics and liquid crystal on silicon (LCoS) panels of the conventional video projector to separate and combine color components. From the experimental results, we obtain a full-parallax reconstructed image and better color reproduction compared with the rainbow hologram.

Toward a Theory of Shape from Specular Flow

Abstract: The image of a curved, specular (mirror-like) surface is a distorted reflection of the environment. The goal of our work is to develop a framework for recovering general shape from such distortions when the environment is neither calibrated nor known. To achieve this goal we consider far-field illumination, where the object-environment distance is relatively large, and we examine the dense specular flow that is induced on the image plane through relative object-environment motion. We show that under these very practical conditions the observed specular flow can be related to surface shape through a pair of coupled nonlinear partial differential equations. Importantly, this relationship depends only on the environment's relative motion and not its content. We examine the qualitative properties of these equations, present analytic methods for recovery of the shape in several special cases, and empirically validate our results using captured data. We also discuss the relevance to both computer vision and human perception.

Stereo-Based Visual Odometry Method and System

Abstract: A method for estimating pose from a sequence of images, which includes the steps of detecting at least three feature points in both the left image and right image of a first pair of stereo images at a first point in time; matching the at least three feature points in the left image to the at least three feature points in the right image to obtain at least three two-dimensional feature correspondences; calculating the three-dimensional coordinates of the at least three two-dimensional feature correspondences to obtain at least three three-dimensional reference feature points; tracking the at least three feature points in one of the left image and right image of a second pair of stereo images at a second point in time different from the first point in time to obtain at least three two-dimensional reference feature points; and calculating a pose based on the at least three three-dimensional reference feature points and its corresponding two-dimensional reference feature points in the stereo images. The pose is found by minimizing projection residuals of a set of three-dimensional reference feature points in an image plane.

Relative Motion Estimation for Vision-based Formation Flight using Unscented Kalman Filter

Abstract: This paper describes a vision-based relative motion estimator in the formation ∞ight of two unmanned aerial vehicles (UAV’s). The navigation of a follower aircraft relative to a target (or leader) aircraft is performed by vision-only information from a single camera flxed to the follower aircraft. The images of the target aircraft projected on the videocamera plane of the follower aircraft are captured and processed into vision information. The vision information for the relative motion estimator in this work is composed of three target angles: an azimuth angle, an elevation angle, and a subtended angle. Using this vision information measurement, the follower aircraft estimates a target relative position, a target relative velocity, a target size, and target acceleration components in the framework of an unscented Kalman fllter (UKF). The UKF is applied to the relative motion estimator due to the highly nonlinear characteristics of the problem at hand. In order to evaluate the performance of the vision-based navigation fllter, vision information obtained through a real-time ∞ight test is post-processed by the fllter. The real-time vision information, obtained by a geometric active contour method on an onboard computer, is composed of three points of the target aircraft on the camera image plane of the follower aircraft. These target points are the center point, the left wingtip point, and the right wingtip point. The target center point on the image plane provides information about the azimuth and the elevation angles of the target in the camera frame, and the two wingtip points provide information about the subtended angle of the target, which ultimately provides the target size. The vision-based estimation results of the target-follower relative motion and target characteristics are compared to actual data that are independently obtained from the onboard integrated navigation systems of both aircraft during the ∞ight test. Each integrated navigation system is composed of an inertial measurement unit (IMU), a global positioning system (GPS), and a magnetometer. Comparisons indicate that the vision-based estimation fllter produces satisfactory estimation results and thus successfully overcomes the highly nonlinear system characteristics by the UKF framework.

Global Correlation Based Ground Plane Estimation Using V-Disparity Image

Abstract: This paper presents the estimation of the position of the ground plane for navigation of on-road or off-road vehicles, in particular for obstacle detection using stereo vision. Ground plane estimation plays an important role in stereo vision based obstacle detection tasks. V-disparity image is widely used for ground plane estimation. However, it heavily relies on distinct road features which may not exist. In here, we introduce a global correlation method to extract the position of the ground plane in V-disparity image even without distinct road features.

Target Tracking Using a Joint Acoustic Video System

Abstract: In this paper, a multitarget tracking system for collocated video and acoustic sensors is presented. We formulate the tracking problem using a particle filter based on a state-space approach. We first discuss the acoustic state-space formulation whose observations use a sliding window of direction-of-arrival estimates. We then present the video state space that tracks a target's position on the image plane based on online adaptive appearance models. For the joint operation of the filter, we combine the state vectors of the individual modalities and also introduce a time-delay variable to handle the acoustic-video data synchronization issue, caused by acoustic propagation delays. A novel particle filter proposal strategy for joint state-space tracking is introduced, which places the random support of the joint filter where the final posterior is likely to lie. By using the Kullback-Leibler divergence measure, it is shown that the joint operation of the filter decreases the worst case divergence of the individual modalities. The resulting joint tracking filter is quite robust against video and acoustic occlusions due to our proposal strategy. Computer simulations are presented with synthetic and field data to demonstrate the filter's performance

Integral holography: white-light single-shot hologram acquisition

Abstract: A new method for obtaining digital Fourier holograms, under spatially incoherent white-light illumination and in a single camera shot, is presented. Multiple projections of the 3-D scene are created in the image plane of a microlens array, and a digital camera acquires the entire projections in a single shot. Then, each projection is computer processed to yield a single point in a Fourier hologram. The new method, designated as integral holography, is proved for the general case and demonstrated experimentally for a simple case.

Separate plane compression using plurality of compression methods including ZLN and ZLD methods

Abstract: Methods, medium, and machines which compress, enhance, encode, transmit, decode, decompress and display digital video images. Real time compression is achieved by sub-sampling each frame of a video signal, filtering the pixel values, and encoding. Real time transmission is achieved due to high levels of effective compression. Real time decompression is achieved by decoding and decompressing the encoded data to display high quality images. A receiver can alter various setting including, but not limited to, the format for the compression, image size, frame rate, brightness and contrast. In a Doppler improvement aspect of the invention, Doppler velocity scales are incorporated into grayscale compression methods using two bits. Variable formats may be selected and Doppler encoding can be turned on and off based on the image content. A separate plane compression aspect of the invention provides for distinguishing between regions of an image, separating and masking the original image into multiple image planes, and compressing each separated image plane with a compression method that is optimal for its characteristics. From a video stream, separate image streams can be compressed with different methods, and the separate image streams can be stored or transmitted at different rates. Alternatively, frame differencing can be applied to the separated streams. Regions may be distinguished by user input or by automated analysis of the characteristics of various regions of an image, such as the presence of Doppler enhanced pixels.

A Novel Algorithm for Estimating Vehicle Speed from Two Consecutive Images

Abstract: In this paper, we present a new algorithm for estimating individual vehicle speed based on two consecutive images captured from a traffic safety camera system. Its principles are first, both images are transformed from the image plane to the 3D world coordinates based on the calibrated camera parameters. Second, the difference of the two transformed images is calculated, resulting in the background being eliminated and vehicles in the two images are mapped onto one image. Finally, a block feature of the vehicle closest to the ground is matched to estimate vehicle travel distance and speed. Experimental results show that the proposed method exhibits good and consistent performance. When compared with speed measurements obtained from speed radar, averaged estimation errors are 3.27% and 8.51% for day-time and night-time test examples respectively, which are better than other previously published results. The proposed algorithm can be easily extended to work on image sequences

A Homographic Framework for the Fusion of Multi-view Silhouettes

Abstract: This paper presents a purely image-based approach to fusing foreground silhouette information from multiple arbitrary views. Our approach does not require 3D constructs like camera calibration to carve out 3D voxels or project visual cones in 3D space. Using planar homographies and foreground likelihood information from a set of arbitrary views, we show that visual hull intersection can be performed in the image plane without requiring to go in 3D space. This process delivers a 2D grid of object occupancy likelihoods representing a cross-sectional slice of the object. Subsequent slices of the object are obtained by extending the process to planes parallel to a reference plane in a direction along the body of the object. We show that homographies of these new planes between views can be computed in the framework of plane to plane homologies using the homography induced by a reference plane and the vanishing point of the reference direction. Occupancy grids are stacked on top of each other, creating a three dimensional data structure that encapsulates the object shape and location. Object structure is finally segmented out by minimizing an energy functional over the surface of the object in a level sets formulation. We show the application of our method on complicated object shapes as well as cluttered environments containing multiple objects.

Particle-based volume rendering

Abstract: In this paper, we introduce a novel point-based volume rendering technique based on tiny particles. In the proposed technique, a set of tiny opaque particles is generated from a given 3D scalar field based on a user-specified transfer function and the rejection method. The final image is then generated by projecting these particles onto the image plane. The particle projection does not need to be in order since the particle transparency values are not taken into account. During the projection stage, only a simple depth-order comparison is required to eliminate the occluded particles. This is the main characteristic of the proposed technique and should greatly facilitate the distributed processing. Semi-transparency is one of the main characteristics of volume rendering and, in the proposed technique the quantity of projected particles greatly influences the degree of semi-transparency. Sub-pixel processing was used in order to obtain the semi-transparent effect by controlling the projection of multiple particles onto each of the pixel areas. When using sub-pixel processing, the final pixel value is obtained by averaging the contribution from each of the projected particles. In order to verify its usefulness, we applied the proposed technique to volume rendering of multiple volume data as well as irregular volume data.

3-D Displays and Telepresence Systems and Methods Therefore

Abstract: A telepresence system enhances the perception of presence of a remote person involved in a video conference. The system preferably has a two-way mirror, which is between the observer and the display device, positioned at an angle to reflect a backdrop surface. The backdrop surface, which is further away from the two-way mirror than the image plane of the image display device, appears superimposed in a position behind the image of a person from the remote location. The system preferably minimizes image distortion via an optical path for the camera line of sight that is substantially longer than the physical distance between the user and the camera. The system may be asymmetrical, in that one camera is on axis with the user's line of sight while the other camera is off axis with the user's line of sight.

System and method for region classification of 2d images for 2d-to-3d conversion

Abstract: A system and method for region classification of two-dimensional (2D) images for 2D-to-3D conversion of images to create stereoscopic images are provided. The system and method of the present disclosure provides for acquiring a two-dimensional (2D) image (202), identifying a region of the 2D image (204), extracting features from the region (206), classifying the extracted features of the region (208), selecting a conversion mode based on the classification of the identified region, converting the region into a 3D model (210) based on the selected conversion mode, and creating a complementary image by projecting (212) the 3D model onto an image plane different than an image plane of the 2D image (202). A learning component (22) optimizes the classification parameters to achieve minimum classification error of the region using a set of training images (24) and corresponding user annotations.

Scale Invariant Feature Matching with Wide Angle Images

Abstract: Numerous scale-invariant feature matching algorithms using scale-space analysis have been proposed for use with perspective cameras, where scale-space is defined as convolution with a Gaussian. The contribution of this work is a method suitable for use with wide angle cameras. Given an input image, we map it to the unit sphere and obtain scale-space images by convolution with the solution of the spherical diffusion equation on the sphere which we implement in the spherical Fourier domain. Using such an approach, the scale-space response of a point in space is independent of its position on the image plane for a camera subject to pure rotation. Scale-invariant features are then found as local extrema in scale-space. Given this set of scale-invariant features, we then generate feature descriptors by considering a circular support region defined on the sphere whose size is selected relative to the feature scale. We compare our method to a naive implementation of SIFT where the image is treated as perspective, where our results show an improvement in matching performance.

Scale-Invariant Features on the Sphere

Abstract: This paper considers an application of scale-invariant feature detection using scale-space analysis suitable for use with wide field of view cameras. Rather than obtain scale- space images via convolution with the Gaussian function on the image plane, we map the image to the sphere and obtain scale-space images as the solution to the heat (diffusion) equation on the sphere which is implemented in the frequency domain using spherical harmonics. The percentage correlation of scale-invariant features that may be matched between any two wide-angle images subject to change in camera pose is then compared using each of these methods. We also present a means by which the required sampling bandwidth may be determined and propose a suitable anti-aliasing filter which may be used when this bandwidth exceeds the maximum permissible due to computational requirements. The results show improved performance using scale-space images obtained as the solution of the diffusion equation on the sphere, with additional improvements observed using the anti-aliasing filter.