Free Space Optical Systems Engineering: Design and Analysis

Abstract

F ree Space Optical Systems Engineering: Design and Analysis, as stated by the author, is intended to be an introduction to electro-optical (EO) systems design for practicing non-EO engineers and for upper level undergraduate and graduate students. It was motivated by his need to find background research materials for his study of EO systems as a graduate student. The book reflects that desire by organizing theoretical developments into one volume. It is primarily for someone wishing to become an EO design researcher, who needs to understand the theoretical underpinnings of EO design. If the reader desires more detailed understanding of each topic, the author provides numerous references at the end of each chapter. A scientist or engineer desiring to understand just the essentials, and not the derivations, will be better served by other books on optical engineering or EO systems. If one wishes to also understand the theory, this book will mostly get you there, as the conclusions of each development will be useful to the EO design engineer. At already over 500 pages, the book omits important design topics, such as polarization, optical coatings, and lens and mirror systems, but these topics are readily available in other books. Generally, the free space EO system design model comprises an analysis of the source or target, the transmission of light through a medium, an optical subsystem to prepare/preprocess (focus, filter, etc.) the light for detection, a detector subsystem, a signal processing subsystem, and an output subsystem. The book’s chapters line up approximately with this view. Chapter 4 discusses the source; Chapters 6 and 7 discuss the effects of transmission through free space; Chapters 2, 3, and 5 discuss the optical subsystem, Chapter 8 EO detectors, and Chapter 9 signal processing. In addition, Chapter 1 reviews the necessary mathematics for the remaining chapters, and Chapter 10 addresses laser theory. Mathematical developments are well referenced, and each chapter ends with a list of references. Each chapter also ends with a set of problems; unfortunately for selfstudy, the solutionsmanual is not readily available on the book’s companion web site to noninstructors. Also, the neophyte reader should watch for inconsistent notation, which may make selfstudy difficult. Overall, though the author compresses a lot of material, which could be expanded to several semesters in EO, the mathematical developments are clear and do not skip steps ( i.e., “handwave”). The first chapter on “Mathematical Preliminaries” provides a good refresher of most of the necessary mathematics for the sequel developments, but the reader should already have aworking knowledge of linear/matrix algebra, Fourier series and Fourier transforms, complex analysis, and probability, which most engineers receive in a standard undergraduate program. Almost half the chapter is devoted to probability theory and types of probability distributions that are applicable to the analysis of optical signal processing. Additional mathematics are developed as needed in the following chapters. With the exception of propagation models in Chapter 7, the author foregoes a discussion of numerical methods programs, but any EO designer or researcher will have to become familiar with them. The next two chapters cover Fourier and geometrical optics, and the diffraction and scattering theory necessary to understand the optical subsystem design. Chapter 2 begins with a review of Maxwell’s equations and the Helmholtz solution, which is fundamental to understanding the behavior of light in systems. The author then reviews four major theoretical approaches, and their approximation limits, to understanding diffraction fields, Rayleigh–Sommerfeld–Debye, Huygens–Fresnel–Kirchhoff, Fresnel, and Fraunhofer. He then shows several applications of these theories to system design. Using Fraunhofer (far-field) theory, the author then develops a view of lenses as converters of a near-field object to be treated as a far-field object at the observation plane. He also uses Fraunhofer approximation to derive its limits of resolution for both coherent and incoherent sources. Finally, in this chapter, he analyzes the system optical resolution of two points using spatial sampling—analogous to digital (time) sampling. Chapter 3 defines nomenclature and optical terms and develops the mathematics of geometrical optics. The calculations of geometrical optics are clearly developed, including refraction, the theory of thin and thick lenses and the effects of apertures and field stops on imaging. This chapter is essential to understanding optical design. Chapter 4 provides a standard development of radiometry. The author defines radiometric terms and then develops the mathematics to understand their distinction and use. (Some photometric terms for visible light are different, but the radiometric terms used are well known and sufficient for developments in the rest of the book.) These terms are frequently misused in common usage and need to be understood. He then develops a historical explanation of blackbody radiation, and theories of absorption, reflection, and exitance based on the works of Rayleigh, and Wien. These developments lead to Planck’s radiation equation for spectral radiance, which is