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.

A simple and robust method to extend the dynamic range of an aberrometer

Abstract: We present an algorithm to extend significantly the dynamic range of a Shack-Hartmann wavefront sensor With this method, the recorded Shack-Hartmann spots are not constrained to stay in the field of view of their lenslet The proposed algorithm is computationally effective, robust to a high level of noise on the measured centroid positions and also to missing centroid values The principle is closely related to the description of wavefronts using Zernike polynomials, which makes optimization for a given sensor and application achievable thanks to numerical simulation These features make it useful for the measurements of highly aberrated eyes

Systems and methods for generating spherical images

Abstract: An imaging system comprises four image sensors each pointing outwardly from the vertices of a notional tetrahedron with the optical axes of the image sensors substantially collinear with respective medians of the notional tetrahedron, with the focal plane array of each image sensor positioned between the lens system of its respective image sensor and the centroid of the notional tetrahedron. The imaging system and can be used to obtain image data for generating a spherical image of the space surrounding the imaging system. A method for generating a spherical image from this image data assigns spherical coordinates to the pixels in the images according to a cylindrical projection that is individually aligned with the image plane of each image, and blends overlapping pixels and fills blank pixel spaces. The method can be applied to image data representing outward views from the vertices or centroids of faces of any Platonic solid.

Quantitative assessment of flow velocity-estimation algorithms for optical Doppler tomography imaging

Abstract: We present a quantitative comparison of three categories of velocity estimation algorithms, including centroid techniques (the adaptive centroid technique and the weighted centroid technique), the sliding-window filtering technique, and correlation techniques (autocorrelation and cross correlation). We introduce, among these five algorithms, two new algorithms: weighted centroid and sliding-window filtering. Simulations and in vivo blood flow data are used to assess the velocity estimation accuracies of these algorithms. These comparisons demonstrate that the sliding-window filtering technique is superior to the other techniques in terms of velocity estimation accuracy and robustness to noise.

Evaluation of subpixel feature localization methods for precision measurement

Abstract: This paper provides a review of a number of subpixel estimators classified as moment based, local modelling and reconstruction. Three algorithms are described in detail, one from each class. In the first, the basic centroid method is generalized so that it is applicable to a wider class of problems and the general formulation is applied to develop a subpixel ridge estimator. The second algorithm is a restricted polynomial model and is developed based on the assumption that an edge profile remains invariant in a local neighborhood. The third algorithm uses Gaussian interpolation to perform local image reconstruction. Simulations are performed to measure the performance of these three algorithms under ideal and noisy conditions.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.