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SIGMA - An Optical Design Legacy

After many years of a mostly academic career, Tina and Michael Kidger decided in 1982 to form a business based on the desktop optical design software Michael had developed for use by designers in both student and professional pursuits. The logo chosen for their software product was SIGMA. Origins of the SIGMA software trace back to Michael's student years preceding 1960 when Michael graduated from Imperial College with an MSc degree. Following graduation Michael joined Rank Taylor Hobson in Leicester, UK where he wrote a lens optimisation program (among the world's earliest) for an Elliott computer.

In 1963 Michael returned to Imperial College (IC) and joined the Optical Design Group as a key member of the team developing software for 'automatic lens design' under the leadership of Charles Wynne. In rapid succession in the 1960's and 70's the team developed software for Elliott, Atlas, Mercury, IBM 709 and CDC 7000 machines. The later programs were written in Fortran and run in batch mode. Nevertheless, they were powerful, and were made available to industry significantly stimulating and revitalizing optical design in the UK.

In the 1970's, at Michael's insistence, the IC group acquired a series of desktop computers. These machines, mostly from Hewlett-Packard, used a BASIC interpreter, had on-screen graphics and were powerful enough to support an optical design package.

A breakthrough came in the late 70's with the appearance of the HP85 computer - the first truly portable computer enabling software development both in the office and at home. The first program using the Sigma name was developed by Michael for the HP85 and shown at the International Lens Design Conference in Oakland in 1980 where it was the cause of considerable interest and excitement. The commercial implications of this led to the establishment of Kidger Optics Limited in 1982.

The 1980's saw a rapid expansion in the use of desktop computers. Kidger Optics met the growing demand for desktop optical design software by supplying programs for the HP9800 series, the Apple II, the IBM PC and the Macintosh all using BASIC interpreters or compilers. Hardware costs were affordable and optical design became the activity of engineers and scientists rather than the 'experts'.

The desktop environment placed new demands on optical design software, particularly on the user interface, and created an urgent need for a new style of training in optical design. Michael created a series of training courses for 'non-experts' implementing a 50-50 mix of theory and practical work based on SIGMA. These courses were run annually by Kidger Optics Ltd, and given internationally.

With the advent of the graphical user interface, first on the Mac and then on the PC, it became clear in the early 90's that the structure of the BASIC SIGMA programs was unsuitable for further development. Michael supervised the 'translation' of the software first into Visual BASIC (the WinSIGMA program) and then into C++ for SIGMA2000 and SIGMA2100. These programs were fast, with good features and good graphics, and conformed to Microsoft standards for Windows.

In the late 80's and early 90's, optional modules were developed for SIGMA which were initially stand-alone programs and were later incorporated into SIGMA2000/2100. These were the Illumination Analysis module, the Narcissus Analysis module, and the Lens Library. Kidger Optics also developed SigmaTol, a program for statistical tolerance analysis, and Film2000 for multi-layer thin film design. These programs were all characterised by the guiding principles for SIGMA - ease-of-use, uncluttered implementation, reliability.

SIGMA2100 was the culmination of 38 years of development by Michael and his colleagues and was, as he said, 'the program we always wanted to have'. Further development of the SIGMA product-line ended in 1998 with Michael's untimely death while on a teaching visit to Australia. The SIGMA program remains in use today by many optical designers, and its legacy continues to build through an enduring influence on the field of commercial optical design. All rights and the source code to SIGMA owned by Kidger Optics Ltd were acquired by Focus Software Inc., now ZEMAX Development Corporation in 1998.

We acknowledge with thanks the use of material by David E. L. Freeman, MSc, DIC, a student, friend and associate of Michael J. Kidger.

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