MicroscopyPioneers
Figure 2 : Peter Hawkes at a recent conference.
humidity-controlled cellars of the college. At a time when unisex clothing and long-haired men were not so common, one might overhear the Russian scholar Peter Squire (another member of the wine committee) asking his wife Natasha “malchik ili devushka?” (boy or girl?). Back to Cosslett’s EM group: the 1960s and 1970s were exciting years to be in electron optics, with Hans Deltrap showing that quadrupoles and octopoles can correct C s (on an optical bench), David Hardy demonstrating C c -correction, and Mike T omson putting the early
computers of the 1960s to work on electron lens problems, soon to be followed by Eric Munro. In 1966 Albert Crewe organized a workshop at Argonne National Laboratory, the object of which was to design a high-voltage aberration- corrected TEM and to persuade the NSF to fund its construction. (T e doormats of the Zero-gradient Synchrotron building were embellished with quadrupoles.) With money no object, Crewe invited experts from Europe, Asia, and the USA to spend a month at ANL, all expenses paid, designing such a microscope. At the end, we presented our recommen- dations to our colleagues and to representatives of the major US funding bodies, unsmiling hard-faced men sitting in the front row. Nothing was forgotten. Architects showed plans of the building that would house the instrument, which was itself described in detail: gun, accelerator, lenses, quadrupole– octopole aberration corrector, image recording… Alas, the NSF said “no,” but many long-term friendships were forged: I am still in touch with Ron Moses and remained in regular contact with Albert Crewe until his death. “I hope you won’t fi nd too many mistakes,” he scrawled across one reprint. I didn’t.
Cambridge was a pioneer in scientifi c computing.
I remember the pleasure of Titan Autocode, the programming language of the Titan computer, which had a very thin manual: “All you need to know is here,” it proclaimed. “If you cannot fi nd the answer to a question, then you didn’t need to ask it!” T is was disconcerting at fi rst but very refreshing in practice. Toward the end of the 1960s, I talked to Cosslett about digital image processing of electron images and suggested that we needed a computer such as the PDP. I expected him to off er to apply for funds, but instead he told me to apply myself. T is was my fi rst such experience, but all went well. We acquired a PDP-8 with 12 kbytes of memory and, with Martyn Horner’s expertise to back them, Owen Saxton and Ralph Gerchberg showed that the “phase problem” could be solved by using the image and diff raction pattern of the same specimen area.
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T e Gerchberg–Saxton algorithm has now spread into a vast range of scientifi c fi elds. Not long aſt er, an application for funding to buy an Optronics Filmwriter was also successful. Cambridge was also one of the very few European nodes on the ARPANet, which was used by John Fitch to develop the computer algebra language CAMAL. I used CAMAL to evaluate aberration integrals for various fi eld models, but this very user-friendly language was later superseded by other programs. However, as recently as 2009 Fitch was pointing out its attrac- tions over more recent languages.
In 1978, Hermann Wollnik, at that time professor in the University of Giessen and well known in the electron optical world for his studies on the aberrations of spectrometers, wrote to suggest that a meeting designed to bring together the disjoint worlds of electron optics, spectrometer optics, and accelerator optics would be benefi cial all round. He and Karl Brown (SLAC) invited me to represent electron optics, and a fi rst meeting on charged-particle optics was held in Giessen in 1980. T is was a great success, and cross-fertilization was visible at all levels. T e second meeting was held in Albuquerque in 1986 with funding from Los Alamos National Laboratory, aſt er which CPO conferences have been held every four years. I organized the 1990 meeting in Toulouse; since this included full-scale French lunches (four courses with unlimited wine and coff ee) every day and a magnifi cent banquet in a nearby château, it was voted a great success. T e optics was good too.
My attention was caught by papers on image algebra,
a mathematical structure that treats entire images as elements of an algebra. T is is especially attractive for mathematical morphology, a non-linear set-theory-based approach to image processing, but is also nice for linear image processing. I made one or two contributions to the subject, notably a paper entitled “T e STEM forms templates” [ 1 ], and was for some years on the editorial board of the Journal of Mathematical Imaging and Vision, the leading serial on the subject.
In 1974 the future of Cosslett’s group in the Cavendish was uncertain, and I received a letter from Bernard Jouff rey, Gaston Dupouy’s successor in the Toulouse Laboratory of Electron Optics where the world’s fi rst high-voltage electron microscope was built, suggesting that I might like to join the laboratory with a view to launching image processing in Toulouse. My application to join the CNRS was successful, and in 1975 I moved to the Toulouse Laboratory, where I remained until (obligatory) retirement in 2002, followed by a few years as Emeritus Director of Research ( Figure 2 ). Aberrations remained a preoccupation throughout all these years, marked by few high points. In 1997, I was invited to give a talk at the EMAG meeting in Cambridge [ 2 ] on the centenary of J. J. T omson’s demonstration that the electron was a particle, for which he in due course received the Nobel Prize. (A few years later, his son received the Nobel Prize for demonstrating that it is, on the contrary, a wave!) T at meeting was memorable for two papers: Ondrej Krivanek and colleagues showed that they had succeeded in correcting the spherical aberration of a STEM by means of quadrupoles and octopoles. And Mick Brown launched the idea of a specialized laboratory
www.microscopy-today.com • 2016 January
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