On the Deformation of Image Intensity and Zero-Crossing Contours Under Motion

Image intensity and edge are two major sources of information for estimating the motion in the image plane. The 2-D motion obtained by analyzing the deformation of intensity and/or edges is used to recover the 3-D motion and structure. In this paper we show that the motion defined by the image intensity differs from the motion revealed by the (zerocrossing) edge. Understanding of this discrepancy is important since most of the 3-D motion recovery algorithms reported so far require accurate 2-D motion as their input. We begin the discussion by assuming the invariance of intensity, that the evolution of image intensity manifests the underlying transformation of the image due solely to the motion of objects. We then raise the question if the zerocrossing of the Laplacian operating on the image intensity is invariant too. The change of perspective view due to relative motion results the zerocrossing not being preserved as the image evolves, thereby deteriorating the accuracy of the 2-D motion obtained from the zerocrossing contour. We derive how much the zero-crossing contour deviates from its correct position due to motion. The result may be used to determine the reliability of the zerocrossing contours for the purpose of the motion estimation

A Contour Base Recovery of Image Flow: Iterative Method

We present an iterative algorithm for the recovery of 2-D motion, i.e., an algorithm for the determination of a transformation which maps one image onto another. The local ambiguity in measuring the motion of contour segments (called the aperture problem ) forces us to rely on measurements along the normal direction. Since the measured normal flow itself does not agree with the actual normal flow, the full flow recovered from this erroneous normal flow possesses substantial error too, and any attempt to recover the 3-D motion from such full flow is doomed to failure. Our method is based on the observation that a polynomial approximation of image flow provides sufficient information for 3-D motion computation. The use of an explicit flow model enables us to improve normal flow estimates through an iterative process. We discuss the adequacy and the convergence of the proposed algorithm. The algorithm has been tested on synthetic and some of simple natural time-varying images. The image flow recovered from this scheme was sufficiently accurate so as to be useful in 3-D structure and motion computation

Second Interim Technical Report for Advanced Research in Range Image Interpretation for Automated Mail Handling

This is the report on range image interpretation of singulated irregular parcels. The overall approach to this problem was to find the most general and generic method that will interpret the data yet is computationally economical. We have observed that the large majority of objects that are classified as Irregular Parcels are convex or can be modeled as such plus some deformation. Hence the primitive model that we have chosen, is the superquadric plus deformations such as tapering and bending along the major axis. The superquadric model is an analytic representation of volume for which cross-sections are a class of curves varying between rectangular to elliptical (of course, circular and square shapes are included). As a side product of this representation we obtain naturally the position, orientation and the scale of the object. The principle of recognition is a fitting procedure which changes the parameters so as to minimize the difference between the data and the volume of the model. We believe that this approach is more general than any previously model based approach including CAD/CAM systems. In comparison to the Generalized Cylinder model proposed by Binford [3] and continued with his students [13], our model has the advantages that: a) It does not require any preprocessing, that is the fitting is performed on raw 3-D data points. b) The interpretation is performed in coarse to fine fashion, or from global to local

Centrality dependence of pi(+/-), K-+/-, p, and (p)over-bar production from root(NN)-N-S = 130 GeV Au+Au collisions at RHIC

Identified pi(+/-), K+/-, p, and (p) over bar transverse momentum spectra at midrapidity in root s(NN) = 130 GeV Au + Au collisions were measured by the PHENIX experiment at RHIC as a function of collision centrality. Average transverse momenta increase with the number of participating nucleons in a similar way for all particle species. Within errors, all midrapidity particle yields per participant are found to be increasing with the number of participating nucleons. There is an indication that K+/-, p, and (p) over bar yields per participant increase faster than the pi(+/-) yields. In central collisions at high transverse momenta (p(T) greater than or similar to 2 GeV/c), (p) over bar and p yields are comparable to the pi(+/-) yields

Net charge fluctuations in Au+Au interactions root s(NN)=130 GeV

Data from Au+Au interactions at s(NN)=130 GeV, obtained with the PHENIX detector at the Relativistic Heavy-Ion Collider, are used to investigate local net charge fluctuations among particles produced near midrapidity. According to recent suggestions, such fluctuations may carry information from the quark-gluon plasma. This analysis shows that the fluctuations are dominated by a stochastic distribution of particles, but are also sensitive to other effects, like global charge conservation and resonance decays

Transverse-mass dependence of two-pion correlations in Au+Au collisions at root(NN)-N-S=130 GeV

Two-pion correlations in roots(NN) = 130 GeV Au+Au collisions at RHIC have been measured over a broad range of pair transverse momentum k(T) by the PHENIX experiment at RHIC. The k(T) dependent transverse radii are similar to results from heavy-ion collisions at roots(NN) = 4.1 , 4.9, and 17.3 GeV, whereas the longitudinal radius increases monotonically with beam energy. The ratio of the outwards to sidewards transverse radii (R-out/R-side) is consistent with unity and independent of k(T)

Measurement of the midrapidity transverse energy distribution from root(NN)-N-S=130 GeV Au+Au collisions at RHIC

The first measurement of energy produced transverse to the beam direction at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory is presented. The midrapidity transverse energy density per participating nucleon rises steadily with the number of participants, closely paralleling the rise in charged-particle density, such that ⟨ET⟩/⟨Nch⟩ remains relatively constant as a function of centrality. The energy density calculated via Bjorken’s prescription for the 2% most central Au+Au collisions at √sNN=130GeV is at least εBj=4.6 GeV/fm3, which is a factor of 1.6 larger than found at √sNN=17.2 GeV ( Pb+Pb at CERN)

Event-by-event fluctuations in mean p(T) and mean e(T) in root s(NN)=130 GeV Au+Au collisions

Distributions of event-by-event fluctuations of the mean transverse momentum and mean transverse energy near mid-rapidity have been measured in Au+Au collisions at roots(NN)=130 GeV at the Relativistic Heavy-Ion Collider. By comparing the distributions to what is expected for statistically independent particle emission, the magnitude of nonstatistical fluctuations in mean transverse momentum is determined to be consistent with zero. Also, no significant nonrandom fluctuations in mean transverse energy are observed. By constructing a fluctuation model with two event classes that preserve the mean and variance of the semi-inclusive p(T) or e(T) spectra, we exclude a region of fluctuations in root s(NN)=130 GeV Au+Au collisions

Centrality dependence of charged particle multiplicity in Au-Au collisions at root(S)NN=130 GeV

We present results for the charged-particle multiplicity distribution at midrapidity in Au-Au collisions at roots(NN) = 130 GeV measured with the PHENIX detector at RHIC. For the 5% most central collisions we find dN(ch)/d eta (|eta =0) = 622 +/- 1(stat) +/- 41(syst). The results, analyzed as a function of centrality show a steady rise of the particle density per participating nucleon with centrality

Measurement of single electrons and implications for charm production in Au+Au collisions at root(NN)-N-S=130 GeV

Transverse momentum spectra of electrons from Au+Au collisions at roots(NN) = 130 GeV have been measured at midrapidity by the PHENIX experiment at the Relativistic Heavy Ion Collider. The spectra show an excess above the background from photon conversions and light hadron decays. The electron signal is consistent with that expected from semileptonic decays of charm. The yield of the electron signal dN(e)/dy for p(T) \u3e 0.8 GeV/c is 0.025 +/- 0.004(stat) +/- 0.010( syst) in central collisions, and the corresponding charm cross section is 380 +/- 60(stat) +/- 200(syst ) mu b per binary nucleon-nucleon collision