In general, the authors of scientific and technical books collect the subject material scattered in literature, especially research articles, and combined with their personal theoretical and experimental knowledge and experience, try to present it in a cohesive and easily readable and understandable manner, to enable the reader to choose the direction in which to move, once he has decided the topic of his research. The present attempt of the author is to acquaint the reader with various theoretical and experimental studies of various topics of interest in modern optics, and further enable him to choose the topic of research based on his interest and understanding. The choice of the topics has been made by the author on the basis of his theoretical and experimental background and various interactions with scientists and academicians, while working in DRDO labs (like LASTEC, IRDE, and GTRE), IIT, Delhi, and foreign labs in France, Austria, Switzerland, and Italy. Various important topics including night vision instruments, compensation of aberrations, and digital holographic microscopy, have been discussed from the points of view of concepts and research applications.