Fluorescent digital image correlation techniques in experimental mechanics

Abstract

White light has often been used for surface illumination to acquire images for digital image correlation (DIC) analysis. In recent years, fluorescent imaging technique has been introduced for illumination, surface deformation and topography measurements with applications on various materials including biomaterials (biofilms, etc.) at the microscale. Traditional imaging, with the use of white light, encounters technical issues such as specular reflection owing to moisture or smooth shiny surfaces (e.g., metallic or glass surfaces). As an alternative to white light, fluorescent imaging serves as a solution to resolve the issues of specular reflection. Fluorescent DIC techniques, especially the fluorescent stereo DIC, allow 3D surface profilometry and deformation measurements at the microscale and submicron scale. Fluorescent stereo imaging under a microscope utilizes emission wavelengths that are different from illumination wavelengths to ensure clear images on any surface that might give reflections at certain angles when white light is used, allowing accurate metrology and deformation measurement. In addition microscopic fluorescent imaging provides nanoscale resolutions surpassing Abbe’s diffraction limit. This paper provides a review of the recent advances in fluorescent DIC.