The first forays into computer designed lenses

The early years of lens design, and particularly photographic lens design, were not for the faint-of-heart. Calculations were performed using mechanical calculators, books of trigonometric tables, Fuller’s cylindrical slide rules with helical scales, and people who known as ‘computers’ as assistants. Probably the most important tool in lens design was geometrical ray tracing, a technique by which the paths of light rays emanating from a point in an object are traced through several lens elements following the laws of geometrical optics to determine the manner in which these rays recombine in the image. An ideal lens would see all rays from a point recombine a corresponding point [3].

A Fuller’s spiral cylindrical slide rule (Keuffel & Esser 4015). This had a helical scale which allowed for 50 turns around the cylinder. It was equivalent to a traditional slide rule 500 inches (12.7m) in length. They could provide results of up to 4-5 significant digits.

One of the original pioneers of the use of computers in designing lenses was Charles Wynne. The design of his revolutionary f/0.71 lens took more than two years. At the time Alan Turing, working on the Manchester computer at Manchester University was looking for some arduous tasks to test the capability of the new machine. Wynne send the provisional design for the lens, including copies of the ray-trace equations. The computer wasn’t exactly up to the task, due to something like its thermionic valves failing, so the calculations results appeared long after the prototype had been completed.

By 1955 the next generation of computers were appearing, and with increased complexity a realization that they would be required to enhance optical formulae. This lead to the creation of dedicated computers to perform lens calculations. In continental Europe, by 1953 Leitz had in operation the Z5, a relay computer from Conrad Zuse. To keep up with the number crunching needs of lens design, Carl Zeiss Jena developed a relay computer, the Oprema [6], in 1954/55 (the first in the GDR). The computer was developed by a team led by Wilhelm Kämmerer and Herbert Kortum – it took up a floor area of 55m², had 17,000 relays, and used 500km of cables. It was in operation until 1963, and reduced calculations that would have taken an hour by hand to a few seconds. On the other side of the globe in 1956, Dr. Okazaki Bunji created Japan’s first electronic computer, for Fuji [5]. Known as the FUJIC, it was designed to perform lens calculations, and supposedly was 2000 times faster than the equivalent human calculation.

Post 1955, Wynne began work on the first Atlas computer, developing programs for ray-tracing. In 1959 Wynne, with his colleague at the Wray company, Michael Nunn, published their pair of classic papers on Wynne’s invention for iterative lens design with digital computers, with work performed on a Ferranti Mark 1 [1,2]. Later work [4] continued on a Ferranti Mercury computer.

Further reading:

  1. Wynne, C.G., “Lens Designing by Electronic Digital Computer: I”, Proceedings of the Physical Society, 73(5), pp.777-787 (May 1959)
  2. Nunn, M., Wynne, C.G., “Lens Designing by Electronic Digital Computer: II”, Proceedings of the Physical Society, 74(3), pp.316-329 (Sept. 1959)
  3. Finkelstein, N.A., “Small digital computers and automatic optical design”, in Proc. Eastern Joint Computer Conference: Design and Application of Small Digital Computers, pp. 81-85 (1954)
  4. Wynne, C.G., Wormell, P.M.J.H., “Lens Design by Computer”, Applied Optics, 2(12), pp.1233-1238 (1963)
  5. Okazaki, B., “The first electronic computer in Japan: The birth of FUJIC and its death”, BIT (Tokyo), 3(12), pp.1091-1097 (1971)
  6. Winkler, J.F.H., “Oprema – The Relay Computer of Carl Zeiss Jena“, (2019)
  7. Kidger, M.J., “The Application of Electronic Computer to the Design of Optical Systems, including Aspheric Lenses”, PhD Dissertation, University of London (1971)
  8. The World’s Largest Commercial Cylindrical Slide Rule has a Scale Length of 24m, Herbert Bruderer (2020)
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