Virtual Image Plane Research Articles

Projecting registration error for accurate registration of overlapping range images

In this paper, we propose a novel algorithm for the automatic registration of two overlapping range images. Since it is relatively difficult to compare the registration errors of different point matches, we project them onto a virtual image plane for more accurate comparison using the classical pin-hole perspective projection camera model. While the traditional ICP algorithm is more interested in the points in the second image close to the sphere centred at the transformed point, the novel algorithm is more interested in the points in the second image as collinear as possible to the transformed point. The novel algorithm then extracts useful information from both the registration error and projected error histograms for the elimination of false matches without any feature extraction, image segmentation or the requirement of motion estimation from outliers corrupted data and, thus, has an advantage of easy implementation. A comparative study based on real images captured under typical imaging conditions has shown that the novel algorithm produces good registration results.

Improving the spatial resolution and image noise in densely pixilated detectors for positron emission mammography

In positron emission mammography (PEM) sampling artifacts can be introduced from the use of discrete crystals which form planar stationary detectors. With the breast positioned in between the two detectors, the images are reconstructed by backprojecting lines of response (LORs) onto seven, equally spaced, virtual image planes. LORs are assumed to start and end on a unique point which is the centroid of interaction of gamma rays within each crystal. This effect limits the sampling of the image space and introduces gridlike sampling artifacts due to the variable density of LORs that intersect each pixel in the image. When using crystals that are very densely pixilated, as in PEM, the regions associated with each crystal in the crystal identification matrix may overlap. We postulate that by allowing the LORs to shift away from the centroid, toward the next most probable crystal element, sampling artifacts should be reduced. The solid angle function is an image uniformity correction function that corrects for the varying geometrical efficiencies of image pixels. The solid angle function is the last thing applied before the images are displayed. We postulate that by reordering the solid angle function and the smoothing algorithm, image quality should improve. Reformatting data from contrast resolution and point source phantom studies with the new strategies showed no or very few sampling artifacts. Contrast resolution measurements showed an improvement in both contrast and signal-to-noise ratio. In most cases point source measurements showed an improvement in spatial resolution and a reduction in noise. The clinical PEM images were reformatted with the new strategies where they showed no sampling artifacts and were smoother. The reformatted images were easier to interpret.

Multispectral imaging using compact compound optics

A very thin image capturing system called TOMBO (thin observation module by bound optics) is developed with compound-eye imaging and digital post-processing. As an application of TOMBO, a multispectral imaging system is proposed. With a specific arrangement of the optical system, spatial points can be observed by multiple photodetectors simultaneously. A filter array inserted in front of the image sensor enables observation of the spectrum of the target. The captured image is reconstructed by a modified pixel rearranging method extended to treat multi-channel spectral data, in which pixels in the captured image are geometrically rearranged onto a multi-channel virtual image plane. Experimental results of the image reconstruction show the effectiveness of the proposed system.

複数台ハンドアイシステムにおける複数対象物追従制御

This paper describes a tracking control for plural hand-eye systems with respect to multiple objects. In case that hand-eye systems attempt to realize tracking control in regard to multiple objects simultaneously, there is a situation that it is desirable one of these hand-eye systems changes its target object. For example, if the hand-eye system continues to track the same target object, collision with the other hand-eye system may happen. To avoid such a collision, the optimal selection of the target object for each hand-eye system is required. To address the above issue, this paper proposes an approach for tracking control of multiple objects in plural hand-eye systems. In proposed approach a virtual image plane is introduced so as to take into account kinematics relation with respect to each camera and target. And on the plane the visual tracking controller is constructed by using weight with regard to target objects. This paper also applies the proposed approach to tracking control in two planar manipulator and numerical simulations and experiments show the efficiency.

Perspective angle transform: Principle of shape from angles

This paper introduces a new relation, called the perspective angle transform (PAT), to deal with shape-from-angle problems, together with its application to 3D configuration recovery from an image. Three main aspects of PAT are presented in this paper. The first is the derivation of PAT which holds between the apparent and real angles under perspective projection. A concept is proposed of a virtual image plane and a new coordinate system, named the first perspective moving coordinate (FPMC) system, for analysis of the shape-from-range problems. Characteristics of FPMC are discussed briefly. The second point is the analysis of PAT properties, for which the general PAT form is introduced on another new coordinate system, named the second perspective moving coordinate (SPMC) system. Using this general form, the gradient of the plane including the real angle is constrained on a curve (PAT curve) of the fourth degree in the virtual image plane. The characteristics of PAT curves and relations between the general PAT form and skewed symmetry are summarized briefly. The last point concerns an application of PAT. As an example, we treat 3D configuration recovery from three arbitrary line segments in the image plane. This recovery corresponds to a generalization of the right-angled interpretation problem proposed and discussed by S.T. Barnard. A solution to the problem is shown using the general PAT form in conjunction with the concept of a virtual crossing point. The right-angled interpretation problem is ascribed to a quadratic equation. A simplified solution is also provided for the case where three line segments have a common crossing point in the image plane. This solution is based on the primary PAT form and is applicable to interpretation of a trihedral vertex with at least two right angles.