What is Optical scanning? Let me offer a definition. Optical scanning is a systematic articulation of light to provide information transfer. Then, what is information? Consider that it means simply organized knowledge. What were the first optical scanning innovations? Semaphores? Or, how about, smoke signals? That is, amplitude modulation of scattered light from controlled groups of particulate aerosol, which disperse as they rise, as observed from a distance. This is a form of serial information transfer.
The two principal forms of optical information transfer are identified as serial and parallel. The parallel form is represented classically by fields such as telescopy, microscopy, and photography—effectively rendering simultaneous transport of the information. The serial form is dominated currently by familiar fields such as television, E-mail, and the reproduction of the graphic arts and sounds, utilizing an arranged timed series of pixels, pels, or voxels. This temporal factor is of basic interest, for it allows (via the optical/electrical transducer—modulator and detector), efficient electronic processing. It is because of this fundamental flexibility that optical scanning has engendered such a commanding role for information transfer. As is surely recognized, many of the classic parallel systems have evolved to either hybrid serial/ parallel or fully serial utilizing various forms of spatial scanning to gain the operational advantages in data manipulation and transfer. Adept development requires, however, dedicated attention to the breadth of the disciplines that may be integrated into these typically diverse systems. An objective of this work is to render a unified orientation to these fundamental and often secluded related factors.
Optical scanning may be conducted with many "shades" of "light," ranging spectrally from UV through the visible to IR and exhibiting incoherent to coherent order. Although the transfer of optical information that is outside that range of electromagnetic radiation is perfectly valid, as notably by CT (X-ray) scans, they are limited in the angular scan flexibility manifest in the dominant forms of optical scanning. Similarly, with the introduction of the laser in the early 1960s, exhibiting its extremely disciplined propagation characteristics, active optical scanning is typically of the laser beam, identified compactly as laser scanning.
One important exception is the field of remote sensing. Here, passive incoherent radiation from a remote source is collected optically at a distance. Its spatial and spectral composition is analyzed by scanning/detection devices to form organized patterns of pixels for subsequent reconstitution. Significant for us is that the scanning devices for each field—operating from very independent viewpoints—exhibit remarkably common factors. This has been highlighted only recently in a publication by this author and R. Barry Johnson, with the objective of unification of the technology. The background and comparative disciplines are expanded in this work.
Other aspects of commonality are the fundamental analogies between different disciplines, as in optical and electronic scanning theory, and in the sampling requirements for effective image, data, and acoustic reconstitution. Recurrent cross-referencing of related factors appears in different portions of this volume. Included is attention to significant arcane techniques such as the Scophony system and several other enlightening acoustooptic scanning methods. Another realization of this work is the periodic heuristic clarification of the fundamentals, with little dependence on the use of detailed mathematical affirmation—which may be accessed readily in the referenced literature.
In recognizing a scanning technology with an extensive background, which has been enhanced under government support for over a decade, this volume offers the first general publication on the advancing field known as agile beam steering. Germinating over the past three decades (reported by this author in 1974), it has attained serious R&D attention for broad application. Agile beam steering is reviewed and presented comprehensively as another unifying dimension.
Rendering now only the thematic highlights, it is noteworthy that the final chapter in this volume summarizes the principal thrust of each chapter. It closes with a unique and potentially controversial independent compilation of the major scanner types, avoiding the almost inevitable preferences that can appear in summaries published by well-meaning researchers, developers, or manufacturers.
Taking a moment to reflect on and recognize the people who have nurtured this work, I extend my unlimited admiration and thanks first to my loving wife, Edith, who has tolerated the diversions, machinations, interruptions, and seclusions, for the sake of whatever accomplishment this may have represented in our minds. Since I have retired officially recently, after 25 years of independent consultation practice, with many prior rewarding writing experiences behind me, and now looking forward to long-delayed relaxation, I'd be out of my mind to even think of doing this again.
Valued support and guidance was rendered in astute review of several chapters by R. Barry Johnson of Optical ETC. Inc., with whom I have had the pleasure of working closely in prior co-authorship and in many exhilarating discussions. Another esteemed review was conducted by Ed Watson of the Air Force Research Labs, rendering revealing and supportive comment on my coverage of a technology of his renowned specialty. The collective total of my professional relationships has surely nurtured this work. My colleague Gerald Marshall, who, after joining the consultation field, also joined me in cochairing many of our SPIE Technical Conferences and rendering valued diversity. More recently, this resource was enhanced with the cochairman-ship of Steven Sagan, who adds the inspiration of youth and the breadth of lens design to our conference skills. Many more—far too many to identify—have surely formed a composite inspiration. You know who you are. Special regard is accorded to George Telecki, Associate Publisher at John Wiley & Sons, Inc., who has provided much appreciated patience and understanding in his guidance of this work.
My sincere thanks to all.