Book excerpt: The book introduces readers to the basic principle of optical imaging technologies. Focusing on human disease diagnostics using optical imaging methods, it provides essential information for researchers in various fields and discusses the latest trends in optical imaging. In recent decades, there has been a huge increase in imaging technologies and their applications in human diseases diagnostics, including magnetic resonance imaging, x-ray computed tomography, and nuclear tomographic imaging. This book promotes further developments to extend optical imaging to a wider range of disease diagnostics. It is a valuable resource for researchers and students in the field of biomedical optics, as well as for clinicians.