Automatic identification of gray porosity and its influence on shielding effectiveness for electromagnetic shielding fabric

Purpose – The purpose of this paper is to propose a new indicator-gray porosity that can objectively evaluate real porosities of electromagnetic shielding (EMS) fabric based on computer image analysis, which aims to address current porosity evaluation by tightness. Design/methodology/approach – A method for the fabric image acquisition is determined and a gray digital model is established. The porosity membership region of true porosity is judged according to the total gray wave. A bi-directional judgment method based on horizontal and vertical single gray waves is proposed to automatically identify the gray porosity in the porosity membership region. After experiments, the differences between the gray porosity indicator and the tightness indicator are analyzed, the influence of the gray porosity on the shielding effectiveness (SE) is discussed, and the advantages of the gray porosity indicator are detailed. Findings – Results show that the proposed indicator can accurately represent the real porosity size of the EMS fabric without pre-acquiring the structure parameters of the fabric, which provides a reference for the study of the electromagnetic characteristic of the EMS fabric. Originality/value – The gray porosity presented in this paper is a new method to objectively evaluate real porosities of the EMS fabric, and can be applied to the research and evaluation of the electromagnetic characteristic for the EMS fabric.