Optical Methods in Experimental Mechanics and Processing Technology

Abstract

The lecture introduces optical and imaging methods to assess structures and material parameters or validate numerical simulations. Selected fabrication technologies and their optical quality control methods are discussed, along with their strengths and limitations in industrial applications. The lecture includes two afternoons of hands-on experience at Empa in Dübendorf.

Objective

The students can describe the process of imaging and image acquisition. They know how to design simple experiments based on optical and imaging methods. They understand the working principle of the optical techniques. Specifically, they can explain how a mechanical measure such as shape, deformation, and strain is transformed into an optical signal such as an interference, a change of the polarization state, or a change of surface temperature. They know the main application field of the individual techniques. They can choose the most appropriate method for solving a specific measurement task and estimate its expected resolution. In addition, they understand the basics of processing technologies from the clean room or 3D printing and how they can assess the quality of layers and structures. Through the hands-on experience, the students gain a more profound and sustained understanding by applying the theoretical foundations to tangible measurement tasks.

Content

After introducing optics and image acquisition, the lecture explains how to transform mechanical quantities such as shape, deformation, strain, or stress into image content. Selected applications to clean room processes for the fabrication of layered structures are explained. The measurement techniques make use of basic principles such as - Triangulation - Interference - Diffraction - Birefringence - Infrared radiation Imaging techniques rely on area detectors, most notably CCD cameras, infrared sensors, and micro-bolometers. Natural white light, halogen lamps, and coherent light sources such as lasers will be used and demonstrated. The topics of the lecture include: - Optics and imaging - Digital Image Correlation (DIC) in 2D and 3D - Diffraction and holography - Terahertz (THz) techniques -Simulations - Device fabrication and 3D printing - Photoelasticity and ellipsometry - Thermoelastic Stress Analysis - Validation of numerical models We show how the methods can be applied to microsystems and large engineering structures. In addition, we explore time-resolved measurements in the context of modal analysis and dynamic events. The lecture will take place two afternoons at Empa, where the students will gain first-hand experience with several optical methods in the laboratory. They will also experience the fabrication of thin films and 3D printing. Depending on the availability of the equipment and the student's interests, these hands-on classes may include, e.g., Digital Image Correlation, THz holography, Time-domain spectroscopy, Thermal Stress Analysis, ellipsometry, and fringe projection.

Resources