RECOGNITION OF FISSION TRACKS ON MINERAL PHOTOMICROGRAPHS USING THE DUAL-TREE COMPLEX WAVELET TRANSFORM

• Grant number: 15/24582-4
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• Start date: January 18, 2016
• End date: January 17, 2017
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geophysics
• Principal Investigator: Sandro Guedes de Oliveira
• Grantee: Alexandre Fioravante de Siqueira
• Supervisor: Lothar Ratschbacher
• Host Institution: Instituto de Física Gleb Wataghin (IFGW). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Institution abroad: Technische Universität Bergakademie Freiberg (TU Bergakademie Freiberg), Germany
• Associated to the scholarship: 14/22922-0 - Segmentation and recognition of fission tracks in photomicrographs from different materials using the wavelet transform, BP.PD

Abstract

The fission track method, employed to estimate the age of natural minerals, requires the counting of tracks from the fission of Uranium-238 formed on the mineral volume. When the mineral is polished, tracks cut by the surface are chemically etched. The process of track counting is usually performed using an optical microscope or photomicrographs obtained from it. The track length can be measured; when these tracks are confined, i.e. entirely located into the mineral, they present the optimal estimate for the real length of the tracks. Confined tracks can be measured if they are etched through another mineral track or fracture. The distribution of frequencies of the length of confined tracks allows the inference of the geological thermal history the mineral was submitted to. Besides being time expensive, the procedures of measurement and counting could introduce practical problems, as the variation of the observing efficiency. An automatic method of fission-track identification can solve such issues and increase the speed of track counting. Some commercial solutions are available, but they often do not lead to satisfactory results. At this point we developed a preliminar methodology using undecimated wavelet transforms (UWT) and threshold segmentation methods to automatically recognize fission tracks in a photomicrograph set. Directional wavelets, according to the proposed methodology, presents a promising technique to solve the discussed issues. During the research internship we intend to widen the possibilities of the methodology, adding the complex dual-tree wavelets (DT-CWT) as another option to process the input datasets. The proposed wavelets have different structure and direction of analysis, leading to distinct results. Also, we will test the effect of the pre and post processing filters (namely, histogram equalization and watershed) on the photomicrographs. At the end of the research internship, we expect to improve the methodology, making it capable of recognizing, enumerating and measuring fission tracks on photomicrograph sets.

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

DE SIQUEIRA, ALEXANDRE FIORAVANTE; NAKASUGA, WAGNER MASSAYUKI; GUEDES, SANDRO; RATSCHBACHER, LOTHAR. Segmentation of nearly isotropic overlapped tracks in photomicrographs using successive erosions as watershed markers. MICROSCOPY RESEARCH AND TECHNIQUE, v. 82, n. 10, JULY 2019. (15/24582-4, 14/22922-0)