Three decades of optical metrology at IIT Madras (1971–2000): a personal perspective

This article presents a personal retrospective of three decades of research and education in optical metrology at the Applied Optics Laboratory (AOL), Indian Institute of Technology Madras, India from 1971 to 2000. I describe the evolution of the laboratory from its early activities in holography and optical instrumentation to research in hologram interferometry, speckle metrology, multiplexed speckle interferometry, electronic speckle pattern interferometry, digital shearography, contouring, and optical testing. Attention is given to the development of methods for laser beam collimation testing, and for measuring very large radii of curvature and long focal lengths using Talbot phenomenon and moiré techniques. The transition from photographic recording to electronic and digital methods marked an important change in both experimental practice and the scope of optical metrology, enabling simultaneous measurements of displacement, slope, and curvature, and opening new approaches to nondestructive testing. The article also reflects on the development of optical instrumentation, optics education, doctoral training, and interactions with Indian industry. Rather than providing a comprehensive survey of the literature, the article describes these developments from the perspective of one of the participants and highlights the contributions of students, colleagues, and collaborators who helped establish a sustained program of optical metrology at IIT Madras.