Introduction.
Finding defects in materials using optics has a long and glorious history. The very first optical detection method used by humans was, of course, based on simple visual inspection. After the invention of the microscope (possibly the greatest optical invention ever), material inspection techniques took a great leap forward. In recent decades, with the invention of the laser and other advances in science and technology, there have been dramatic improvements in existing optical inspection techniques and the creation of many new ones. In this issue, we have collected four papers from different areas of optics that highlight important advances that have been made in material inspection techniques.
Duncan
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Bashkansky
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