Search Results for light illumination

This chapter discusses the tools and techniques of light microscopy and how they are used in the study of materials. It reviews the basic physics of light, the inner workings of light microscopes, and the relationship between resolution and depth of field. It explains the difference between amplitude and optical-phase features and how they are revealed using appropriate illumination methods. It compares images obtained using bright field and dark field illumination, polarized and cross-polarized light, and interference-contrast techniques. It also discusses the use of photometers, provides best practices and recommendations for photographing structures and features of interest, and describes the capabilities of hot-stage and hot-cell microscopes.

The analysis of composite materials using optical microscopy is a process that can be made easy and efficient with only a few contrast methods and preparation techniques. This chapter is intended to provide information that will help an investigator select the appropriate microscopy technique for the specific analysis objectives with a given composite material. The chapter opens with a discussion of macrophotography and microscope alignment, and then goes on to describe various illumination techniques that are useful for specific analysis requirements. These techniques include bright-field illumination, dark-field illumination, polarized-light microscopy, interference and contrast microscopy, and fluorescence microscopy. The chapter also provides a discussion of sample preparation materials such as dyes, etchants, and stains for the analysis of composite materials using optical microscopy.

The formation of microcracks in composite materials may arise from static-, dynamic-, impact-, or fatigue-loading situations and also by temperature changes or thermal cycles. This chapter discusses the processes involved in the various methods for the microcrack analysis of composite materials, namely bright-field analysis, polarized-light analysis, contrast dyes analysis, and dark-field analysis. The analysis of microcracked composites using epi-fluorescence is also covered. In addition, the chapter describes the procedures for the determination and recording of microcracks in composite materials.

Several specialized instruments are available for the metallographer to use as tools to gather key information on the characteristics of the microstructure being analyzed. These include microscopes that use electrons as a source of illumination instead of light and x-ray diffraction equipment. This chapter describes how these instruments can be used to gather important information about a microstructure. The instruments covered include image analyzers, transmission electron microscopes, scanning electron microscopes, electron probe microanalyzers, scanning transmission electron microscopes, x-ray diffractometers, microhardness testers, and hot microhardness testers. A list of other instruments that are usually located in a research laboratory or specialized testing laboratory is also provided.

This chapter describes the various features of the metallurgical microscope. Key concepts are defined such as resolving power, the virtual image, bright- and dark-field illumination, numerical aperture, focal length, image contrast, depth of field, and spherical and chromatic aberration. Metallurgical microscope features such as apochromatic objectives, hyperplane oculars, vertical illuminators, counting reticles, widefield oculars, polarization filters, field diaphragms, interferometers, and tungsten-halogen lamps are explained. The optical system, nosepiece, types of objectives (the lens assembly close to the specimen) and eyepieces, and components of the illumination system are all explained. The last part of this chapter describes special procedures involved in using and calibrating the metallurgical microscope.

Moore's Law has driven many degree circuit features below the resolving capability of optical microscopy. Yet the optical microscope remains a valuable tool in failure analysis. This article describes the physics governing resolution and useful techniques for extracting the small details. It begins with the basic microscope column and construction. The article discusses microscope adjustments, brightfield and darkfield illumination, and microscope concepts important to liquid crystal techniques. It also discusses solid immersion lenses, infrared and ultraviolet microscopy and concludes with laser microscopy techniques such as thermal induced voltage alteration and external induced voltage alteration.

Analyzing the structure of composite materials is essential for understanding how the part will perform in service. Assessing fiber volume variations, void content, ply orientation variability, and foreign object inclusions helps in preventing degradation of composite performance. This chapter describes the optical microscopy and bright-field illumination techniques involved in analyzing ply terminations, prepreg plies, splices, and fiber orientation to provide the insight necessary for optimizing composite structure and performance.