Stewart Bell

STEWART BELL was an optical designer who worked on the development of the cervical cancer smear test and was the original patentee of the key technologies of flight simulators.

Arthur Richard Napier Stewart Bell, optical designer: born 16 March 1920; married 1966 Daphne Woods; died Cirencester, Gloucestershire 9 December 2002.

Stewart Bell was an optical designer who worked on the development of the cervical cancer smear test and was the original patentee of the key technologies of flight simulators.

Arthur Richard Napier Stewart Bell should have been born an American, but his heavily pregnant mother, visiting Scotland, was advised not to make the return sea crossing and so he was born, in 1920, in Ayrshire. Educated in New England and later New Jersey, he watched as his father, Arthur Bell, who was chief engineer on the Chrysler Building in New York, lost out to the engineer from the Empire State Building as builder of the tallest structure in the world.

The accident of his Scottish birth allowed Stewart Bell to volunteer for the Argyll and Sutherland Highlanders in the early part of the Second World War, and he became a training sergeant. His active military service seemed to have been brought to an end when one recruit threw a grenade not forwards but upwards, and Bell was caught in the ankle by the non-fragmenting base section.

While he was convalescing, Bell was asked by a visiting officer what his hobbies were, with rugby or football suggested as good, manly examples. After a glib reply that stamp collecting or even printing were more likely, Bell found himself transferred to a unit specialising in both the identification and production of forged documents.

As the war in Europe was drawing to a close, he was again transferred, this time to the Combined Intelligence Objective Sub-Committees, an organisation charged with liberating commercial secrets, patents and even trademarks from German industry and distributing them equally amongst the Allies.

This was supposed to happen after the factories were secured by the infantry. However, on arriving at Wetzlar in Germany, Bell and his colleagues seized and sealed the Ernst Leitz optical works, only to find themselves coming under fire from Patton's Fifth Army. Luckily for the team, Ernst Leitz's daughter, Else Leitz, surrendered the town to the American force. Although Bell retrieved the plans for both the Leica IIIc and IIIf rangefinder cameras, only the former found their way back to Britain, and the Reid camera company ended up producing an effectively pre-war copy of the famous German camera.

Following his demobilisation, Stewart declined an offer to convert his British Sergeant's stripes into a Private First Class rank in the US army in the Pacific and instead went up to Glasgow University to read Chemical Engineering.

Rediscovering a childhood love of microscopy, Bell proposed a new system of increasing phase contrast (and thus the clarity of microscope imaging) based on cellulose acetate sheets, which were non-destructive to the organic life being examined. He wrote up his work in an article in The Microscope, which was read by Professor John Baker of the Zoology Department at New College, Oxford. An offer to join Baker soon followed. While at New College, Bell switched from microscopy to zoology, gaining a doctorate for his work on the visual response of Annelids (worms), investigating the beginnings of sight in organic life.

Switching fields once again, Bell moved to Air Trainers Limited, designing and building simulators for aeroplanes such as the Hawker Hunter, Vickers Viscount, Lockheed Lightning and even the TSR-2, and producing the world's first all-electronic flight simulator, for the Gloucester Meteor. He was patentee of the key optical technology for flight simulators and the system is still in use today.

In the late 1950s, Bell moved back into mainstream optical design in the Gillett and Sibert company, working on developments in blue light fluorescent microscopy, and designed the examination system used to develop the first cervical cancer smear tests.

Cheap microscope imports from Japan over the next decade effectively killed the British microscope industry and Stewart's livelihood with it. But the mid-Sixties were not an unhappy time – in 1966 he married Daphne Woods, protocol secretary at the American Embassy. The two shared the same mischievous sense of humour, and on the installation of a new "sprinkler system" at the embassy that miraculously seemed not to need any pipes but used wires instead, Daphne would make a point of "talking treason" in the corridors.

The ramifications of this joke emerged when Stewart thought he was being charged wrongly by the GPO for his home telephone bill, and so built a timer to show when calls were in progress. On testing his machine, Bell noticed that the power of the phone signal fell off significantly very shortly after his calls started – they were being bugged.

Following the disappearance of his optical work, Bell turned to commerce. A distant relation of the Bell distilling family, he sold whisky in bond to South Vietnamese businessmen eager to shift their assets out of the country as the North Vietnamese edged closer. By the late 1970s, he had returned to optical design and eventually optical testing. In the final chapter of his varied career, he was, until his death, the main lens tester for the best-known photographic magazines.

He designed and built a new lens-testing system based on variable contrast, and providing a much simpler explanation than the Modulation Transfer Function used by the lens companies themselves. His charts became the final word on the worth of any photographic lens, and he was responsible for the replacement of the iconic, but unscientific, "ships across the Thames" lens-testing system of Amateur Photographer magazine with a repeatable, measurable and accurate system used from 1987 to this day. His uncompromising and occasionally hilarious irascibility with pseudo-scientific writers and editors was in stark contrast to his generous instruction to those who really wanted to learn.

Joël Lacey