Centroid

About: Centroid is a research topic. Over the lifetime, 4110 publications have been published within this topic receiving 53637 citations. The topic is also known as: barycenter (geometry) & geometric center of a plane figure.

High speed scanning method and apparatus

Abstract: A method and apparatus for determining the spatial coordinates of a workpiece including: a precisely formed jig; a planar light source; an electronic imaging device adapted to view the intersection of the planar light with the jig and the workpiece; a video digitizer for sampling and digitizing output signals from the imaging device and in particular reference pulse signals representative of said intersections; digital logic circuitry for algebraically summing video samples to determine the centroid or geometric mean of the reference pulses; and a computer for calculating calibration parameters based on knowledge of the form of the jig and scans of the jig, and applying those calibration parameters to scans of the workpiece to calculate spatial coordinates of the workpiece. A method of determining the centroid of a sensed pulse signal including the steps of integrating the signal over a selected interval including the pulse by analog or digital means, integrating the result of the first integration in like manner and dividing result of the second integration by the result of the first integration.

Parameterized Centroid Frequency-Chirp Rate Distribution for LFM Signal Analysis and Mechanisms of Constant Delay Introduction

Abstract: This paper presents an extension of the integrated time-chirp rate analysis technique, known as the parameterized centroid frequency-chirp rate distribution (PCFCRD), for noisy multicomponent linear frequency modulated signals analysis The PCFCRD is based on a newly defined correlation function and its auto term accumulation is two-dimensionally coherent The principle, cross term characteristic, implementation, properties, parameter selection criterion, antinoise performance, and estimation accuracy are analyzed for the PCFCRD In this paper, comparisons with the coherently integrated cubic phase function, maximum likelihood method, and Lv's distribution are performed With mathematic analyses and numerical simulations, we demonstrate that the PCFCRD outperforms these three representative counterparts Further, by combining with analyses of the PCFCRD, several unclear mechanisms of the constant delay introduction are mathematically interpreted, especially quantitative influences on the chirp rate resolution and theoretical antinoise performance

Accurate and Robust Line Segment Extraction Using Minimum Entropy With Hough Transform

Abstract: The Hough transform is a popular technique used in the field of image processing and computer vision. With a Hough transform technique, not only the normal angle and distance of a line but also the line-segment’s length and midpoint (centroid) can be extracted by analysing the voting distribution around a peak in the Hough space. In this paper, a method based on minimum-entropy analysis is proposed to extract the set of parameters of a line segment. In each column around a peak in Hough space, the voting values specify probabilistic distributions. The corresponding entropies and statistical means are computed. The line-segment’s normal angle and length are simultaneously computed by fitting a quadratic polynomial curve to the voting entropies. The line-segment’s midpoint and normal distance are computed by fitting and interpolating a linear curve to the voting means. The proposed method is tested on simulated images for detection accuracy by providing comparative results. Experimental results on real-world images verify the method as well. The proposed method for line-segment detection is both accurate and robust in the presence of quantization error, background noise, or pixel disturbances.

Analysis of optimal centroid estimation applied to Shack–Hartmann sensing

Abstract: The problem of estimating the centroid of an incoherently imaged point with a CCD array is analyzed. An exact analysis is presented that uses the actual short-exposure function at the CCD instead of the traditional Gaussian approximation. The analysis shows that, for Poisson noise, the centroid variance depends on the CCD size and that truncation effects play a significant part in determining the optimum CCD size. The effects of this on a wave-front reconstruction formed by a Shack–Hartmann sensor are described.