(p.489) Appendix Publication Statistics
(p.489) Appendix Publication Statistics
Over its first half century, holography has been influential at a wide range of scales. Numbers can put its impact into perspective. The subject has attracted thousands of researchers, designers, and other creators, and hundreds of discrete applications. Some 20,000 papers have been published, and over 10,000 conference presentations presented. Some 7000 patents have been granted, a thousand books published, nearly as many theses defended, and at least 500 exhibitions staged. These could be called 'public statistics'. But there are also private statistics. Perhaps market-tracking organizations like Reconnaissance International can suggest how much money has been generated or lost by holographic firms or provided by grant agencies, corporations, and other sponsors. This is one semi-public statistic that is still difficult to discern.
This scale is considerably greater than some other late twentieth-century technologies and nascent sciences. So large, in fact, that the scale itself allows certain trends to be tracked. One relevant approach is 'bibliometry'-the measuring of publications.
Databases of publications, maintained by academic libraries, institutions, and private indexing firms, suggest the rate of activity in the subject of holography. Figure A.1 plots the annual rate of publications of several kinds: books, dissertations, conference presentations, exhibitions, papers, and patents. No single source is complete, because papers on holography have been distributed among a wide variety of journals, magazines, publishers, organizers, and countries. And some forms of publication, such as art exhibitions, are poorly represented in such databases, being listed, if at all, in the form of exhibition catalogues. Even patents can be awkward to quantify, because they may be filed in more than one country.
This kind of analysis can be skewed inadvertently in other ways. A major contribution to inaccuracy is the fact that much research is unpublished. For example, the side-looking radar research that led to holography studies by Leith and Upatnieks was supported by the American military and is still confidential, in parts. The same is true of some of the expertise in Head Up Displays (HUDs) and Holographic Optical Elements (HOEs). Even more commonly, commercial research is often unpublished to ensure a business advantage.
Even with these potential drawbacks, the attempt to quantify publications in holography can still reveal useful information. It is apparent, for example, that the venue of publication shifted with time. Books (see Figure A.1(a)) appeared at a near-constant rate 1970-90, but declined thereafter. The completion of theses (see Figure A.1(b)) peaked in the early 1970s, during the first pulse of interest when research money was relatively plentiful, and again in the early 1990s, when a wider range of applications were identified and investigated. Perhaps surprisingly, the heyday of conference publications (see Figure A.1(c)) was between the mid-1970s and early 1980s, despite the proliferation of regular conferences under the auspices of the SPIE and IS&T from the 1980s. Holography exhibitions (see Figure A.1(d)), both artistic and for wider publics, were an important setting for information transfer during the 1980s, but have declined significantly since then. From the handful of yearly publications from 1947, papers in scientific journals (see Figure A.1(e)) (p.490) exploded in 1965; indeed, the earlier publications by Gabor, El-Sum, and others are scarcely visible at this graphical scale. Papers peaked in 1971, about the time that some highly visible players such McDonnell Douglas were actively promoting holographic technology for advertising displays, pulsed-laser portraiture and non-destructive testing. McDonnell Douglas closed its production facility in 1973, reflecting a wider loss of confidence by American sponsors of holography. Scientific and engineering papers gradually rose to a higher maximum in the mid-1990s, but since that time they have fallen twofold. The granting of patents (see Figure A.1(f)) also evinced a peak in the early 1970s and then, from the early 1980s, has risen steadily.
(1) Kallard, Thomas, Holography: State of the Art Review 1969 (New York: Optosonic Press, 1969); Kallard, Thomas, Holography: State of the Art Review 1970 (New York: Optosonic Press, 1970); Kallard, Thomas, Holography: State of the Art Review 1971-1972 (New York: Optosonic Press, 1972).