Hadamard Transform Optics focuses on Hadamard transform optics and Hadamard encoded optical instruments. The techniques developed to date are described, and a unified mathematical treatment that should facilitate comparisons between different classes of instruments is presented. With this approach, encoded Hadamard transform spectrometers are discussed in very much the same way as encoded imaging devices. The advantages offered by singly and multiply encoded instruments designed for a wide variety of purposes are also considered. This book is comprised of seven chapters and begins with an introduction to optical multiplexing techniques, as well as the connections with weighing designs, along with the best masks for use in optical instruments and the improvement in signal-to-noise ratio that should be produced by multiplexing. Spectrometers which make use of multiplexing, including the Michelson and Mach-Zehnder interferometers and Golay's multislit spectrometers, are then described. Subsequent chapters deal with the basic theory of Hadamard transform spectrometers and imagers; factors that affect the signal-to-noise ratio; and instrumental considerations and systematic errors in instruments. The final chapter looks at some of the applications of Hadamard transform optics, including image processing and in fields such as astronomy and medicine. This monograph will be a useful resource for physicists.