Method for automatic region segmentation on cartridge case base and selection of the best mark region for cartridge case comparison

摘要

Segmentation of certain regions defined on a firearm cartridge case for successful automatic matching of cartridge cases after a cartridge is fired, on the basis of the marks left on the cartridge cases fired. Disclosed is a method for segmentation of a cartridge case base by using surface height matrix information comprising: detecting the center of the cartridge case base; according to this center, obtaining the polar height matrix by subjecting the surface height matrix to polar transformation; acquiring a one-dimensional signal, “Average Height Signal on the Basis of Radius” (AHSBR), by calculation of the mean value on the radius axis applied on the polar height matrix; determining regions similar to circle signal models on the AHSBR and detecting circles; determining the firing pin mark region by threshold processing of the primer region surface height matrix. Letters on the cartridge case base are detected by using slope matrices.

主权项

1. A method which, while preparing data for comparison methods that compare cartridge cases fired from firearms and compute similarity values, segments the cartridge case bases by using surface height matrices for selection of the best appropriate mark regions to be used in similarity computation, characterized by the following steps which aim at detection of a primer circle (28), primer pocket gap circle (29) and cartridge case base circle (27):
a) finding gradient magnitude values for each element on a surface height matrix (5) that covers all of a cartridge case base (1) region and forming a new matrix by locating the gradient magnitude values in such a way that they correspond to the coordinates of each element on the surface height matrix (5); b) detecting coordinates of a center of the cartridge case base by using Hough transformation on the matrix formed in a); c) transforming the surface height matrix of the cartridge case base according to the coordinates of the detected center of the cartridge case base into polar coordinates and obtaining a polar height matrix; d) on the polar height matrix, for each radius value, selecting all data corresponding to the each radius value and calculating the mean value of the all data corresponding to the each radius value; e) forming a one-dimensional signal, called ‘Average Height Signal on the Basis of Radius’ (AHSBR) with the calculated mean values as a function of radius value, wherein the x-axis of the signal shows the radius value and the y-axis shows the calculated mean values corresponding to the radius; f) detecting the primer circle (28), primer pocket gap circle (29) and cartridge case base circle (27) by using the signal similarity analysis conducted on this AHSBR on the basis of the step model 1 (33) and/or step model 2 (34) and/or step model 3 (35).