Building Electro-Optical Systems: Making It All Work

Ein Buch mit ausgesprochen interdisziplinärem Horizont! Die meisten der bisher auf dem Gebiet der Elektrooptik erhältlichen Werke konzentrieren sich auf einen bestimmten Teilbereich. "Building Electro-Optical Systems" bietet Ihnen eine breit angelegte Übersicht: Ob Mikroskope, Kameras, Spektrometer oder Computerausrüstung - hier erhalten Sie viele interessante Einblicke.
Dieses Buch erläutert, nach welchen Grundsätzen man moderne elektrooptische Instrumente wie Mikroskope, Kameras, Überwachungsgeräte und Spektrometer durchrechnet und baut. Dabei werden auch potentielle Fehlerquellen ausführlich behandelt.

You are fools, to say you learn from your mistakes. I learn from the mistakes of other men. - Otto von Bismarck

This is a book of lore. The word evokes many images: Merlin singing spells under the oak trees, a 'San bushman drinking from a hidden sip well through a reed, an angler trying to hook the wisest old trout in the lake. What I mean by it is altogether more homely: a mixture of rules of thumb, experience, bits of theory, and an indefinable feeling for the right way to do things, a sort of technical taste. It is what makes the difference between merely being able to analyze a design once completed, and being able to rapidly synthesize a good design to fit a particular purpose. Coursework and textbooks teach analysis reasonably efficiently, but most contain no lore whatsoever.

This book is an attempt to provide a systematic and accessible presentation of the practical lore of electro-optical instrument design and construction--to be the book I needed as a graduate student. It is intended for graduate students at all levels, as well as practising scientists and engineers: anyone who has electro-optical systems to build and could use some advice. Its applicability ranges from experimental apparatus to CD players.

One of the odd things about lore is that it lives in the fingers more than in the brain, like piano playing. In writing this book, I have often run up against the difference between how I do something and how I think I do it, or how I remember having done it once. Since it's the actual lore of doing that is useful, I have where possible written or revised each section when I was actually doing that task as part of my job or was consulting with someone who was doing so. I hope that this gives those sections a sense of immediacy and authenticity.

Mission

Designing and constructing electro-optical instruments is without a doubt one of the most interdisciplinary activities in engineering. It makes an absorbing and rewarding career, with little danger of growing stale. On the other hand, the same interdisciplinary quality means that instrument building is a bit scary, and keeps us on our toes. The very broad range of technologies involved means that at least one vital subsystem lies outside the designer's expertise, presenting a very real danger of major schedule slippage or outright failure, which may not become apparent until very late in the project.

We in electro-optics rely on whatever subset of these technologies we are familiar with, together with a combination of outside advice, collaboration, and purchased parts. Often, there are many ways of reaching the goal of a robust, working system; then the problem is where to start among a range of unfamiliar alternatives. It's like the classic computer game Adventure: "You are in a maze of twisty little passages, all different." Some judicious advice (and perhaps a map left by a previous adventurer) is welcome at such times, and that's what this book is about, the lore of designing and building electro-optical instruments that work.

To have confidence in an instrument design, we really need to be able to calculate its performance ahead of time, without needing to construct an elaborate simulation. It is a nontrivial matter, given the current fragmented state of the literature, to calculate what the resolution and SNR of a measurement system will be before it is built. It's not that there isn't lots of information on how to calculate the performance of each lens, circuit, or computer program, but rather the complexity of the task and the very different ways in which the results are expressed in the different fields encountered. For example, what is the effect of fourth-order spherical aberration in the objective lens on the optimal band-setting filter in the analogue signal processor, and then on the signal-to-noise ratio of the ultimate digital data set? Somebody on the project had better know that, and this book aims to make you that somebody.

The book is intended in the first instance for use by oppressed graduate students in physics and electrical engineering, who have to get their apparatus working long enough to take some data before they can graduate. When they do, they'll find that real-world design work has much the same harassed and overextended flavour, so in the second instance, it's intended for working electro-optical designers. It can be used as a text in a combined lecture-laboratory course aimed at graduate students or fourth-year undergraduates, and as a self-teaching guide and professional reference by working designers.

Organization

Textbooks usually aim at a linear presentation of concepts, in which the stuff on page n does not depend on your knowing pages n + 1...N. This is very valuable pedagogically, since the reader is initially unfamiliar with the material and usually will go through the book thoroughly, once, under the guidance of a teacher who is presenting information rapidly. Reference books are written for people who already have a grasp of the topic but need to find more detail or remind themselves of things dimly remembered. Thus they tend to treat topics in clumps, emphasizing completeness, and to be weak on explanations and on connections between topics.

Those two kinds of presentation work pretty well in some subject areas, but design lore is not one of them. Its concepts are not related like a tree, or packed like eggs in a crate, but rather are interlinked like a fishnet or a sponge; thus a purely linear or clumped presentation of lore is all but impossible without doing violence to it. Nonetheless, to be any use, a lore book must be highly accessible, both easy to work through sequentially and attractive to leaf through many times. The book is organized into three sections: Optics; Electronics and Signal Processing; and Special Topics In Depth (Front Ends and Bringing Up The System).

The material is presented in varying levels of detail. The differences in the detail levels reflect the amount of published lore and the measured density of deep potholes that people fall into. For example, there are lots of potholes in optomechanical design, but weighty books of relevant advice fill shelf after shelf. Anyway, mechanical problems aren't usually what cause instrument projects to fail--unexamined assumptions, inexperience, and plain discouragement are. To get the job done, we talk instead about how to avoid common mistakes while coming up with something simple that works reliably.

Computer scientists use the concept of locality of reference--it's a good thing if an algorithm works mainly with data near to each other in storage, since it saves cache misses and page faults, but all the data has to be there, regardless. That's the way this book is organized: most of the lore on a particular topic is kept close together in the book for conceptual unity and easy reference, but the topics are presented in a sufficiently linear order that later chapters build mainly on earlier ones, and important connections are noted in both forward and backward directions. A certain amount of messiness results, which (it is to be hoped) has been kept close to a minimum.

The one big exception to this general scheme is Chapter 1, Basic Optical Calculations. It pulls in strands from everywhere, to present the process and the rhythm of conceptual design, and so will contain things that many readers (especially beginners) may find somewhat unfamiliar. Don't worry too much about the technical aspects, because there's more on all those things later in the book, and pointers to other sources. (Teachers may want to leave this chapter until late in the course.) A complete instrument design course based on this book would probably have to wait for a first or second year graduate class. Undergraduate students with a good grasp of electromagnetism, physical optics, and Fourier transforms might benefit from a fourth-year...