Optical sensors are electronic detectors that function by the conversion of light into electrical signals. Such electro-optical sensors are used across industries for both simple and complex purposes as well as in devices like smartphones, smartwatches, medical devices, etc. There has been rapid progress in this field and its applications are finding their way across multiple fields like civil and transportation engineering, pipeline monitoring, medical diagnostics, etc. From theories to research to practical applications, case studies related to all contemporary topics of relevance to this field have been included in this book. It is compiled to provide a general overview of the subject while also providing details about the modern advancements in the field. It strives to be a valuable source of knowledge for students, researchers and experts.