Interferometric observations need snapshots of very high time resolution of the order of (i) frame integration of about 100 Hz or (ii) photon-recording rates of several megahertz (MHz). Detectors play a key role in astronomical observations, and since the explanation of the photoelectric effect by Albert Einstein, the technology has evolved rather fast. The present-day technology has made it possible to develop large-format complementary metal oxide–semiconductor (CMOS) and charge-coupled device (CCD) array mosaics, orthogonal transfer CCDs, electron-multiplication CCDs, electron-avalanche photodiode arrays, and quantum-well infrared (IR) photon detectors. The requirements to develop artifact-free photon shot noise-limited images are higher sensitivity and quantum efficiency, reduced noise that includes dark current, read-out and amplifier noise, smaller point-spread functions, and higher spectral bandwidth. This book aims to address such systems, technologies and design, evaluation and calibration, control electronics, scientific applications, and results.One of the fastest growing applications is signal sensing, especially wavefront sensing for adaptive optics and fringe tracking for interferometry, which is important for long-baseline optical interferometry. The coherence time of the atmosphere is a highly variable parameter. Depending upon the high velocity wind, it varies from

Professor Swapan K. Saha has a strong interest in experimental physics, optical interferometry in particular, and has developed various instruments. He has taught observational astronomy, high-resolution imaging, aperture synthesis, adaptive optics, atmospheric science, and image processing at a couple of premiere institutes in India. Prof. Saha has delivered several invited and plenary talks at various national and international conferences and universities on these topics. Author of a few more books, he is on the editorial boards of the Asian Journal of Physics and the Journal of Optics (Springer) and has edited a book, 21st Century Astrophysics, as well as a special issue of the Asian Journal of Physics on astrophysics in 2004.