Optical interferometry is a technique that uses the interference of light waves to measure small distances, changes in refractive index, or surface irregularities. By combining light from two or more sources, it creates patterns of light and dark fringes, which can be analyzed to extract precise information about the object being studied. This method is widely used in various fields, including astronomy, metrology, and materials science. It allows scientists to achieve high-resolution measurements that are essential for applications like telescopes and surface profiling, making it a valuable tool in both research and industry.