Adaptive thresholding by region of interest applied to quality control of gas electron multiplier foils

Abstract

This paper presents a variation of the technique of adaptive thresholding, as a robust method for segmentation of holes in quality assurance of the Gas Electron Multiplier Foils by analyzing high-resolution images. The proposed thresholding is applied to the region of interest around the holes and offers an effective solution to lighting variations on the GEM-foil image. This technique together with some operations of mathematical morphology allows extracting contours of the holes for accurate quantification. The inner radius and roundness of the holes are used and proposed as a measure to characterize defects in GEM-foils. Techniques and methods described in this work were developed in JAVA programming language and implemented in the Software for Foils Analyzer (SOFA).