"taken together ... the two papers launched modern fiber optics"

Van Heel, A. C. S. ; Hopkins, H. H. and Kapany, N. S.

[Fiber Optics] "A New Method of transporting Optical Images without Aberrations" and "A Flexible Fibrescope, using Static Scanning"

London: MacMillan & Co., Ltd. 1954. First Edition. x, 22, viii, 23-46, xi-xviii pages. The entire issue offered. Self wrappers, stapled. Rusty staples, light soiling to the wrappers. Clean internally. Very Good. Wraps. [29726]


A major issue in the early development of modern fiber optics was the leakage of light from the fibers, reflections internal to the medium, and crossover of light contamination (crosstalk) from one fiber to the next. Van Heel (and his uncredited research partner Brian O'Brien) discovered a solution to this conundrum (cladding the fibers), enabling furture research and the practical exploration of the use of fiber optics in many fields. Van Heel's letter to Nature was to have established his precedence in the matter (his letter was dated May 21st of 1953), but Nature's unexplained delay in publication meant that a more detailed description Van Heel submitted to a Dutch paper De Ingenier, rushed into print in the June 12, 1953 issue, established that precedence. The little known Dutch publication however received little notice. Nature, with it's reputation and wide reach made the discovery much more widely known.

Separately, Harold Horace Hopkins, a "young rising star in the little world of European optics" was asked by a physician if he might develop a flexible device to replace rigid gastroscopes used at the time for endoscopies. He, and a researcher he hired Narinder S. Kapany, set to work trying to figure out how to align the fibers (unclad) in such a way as to transmit light images from one end of a fiber bundle to the other (a non-trival task, something we call coherent fibre optics). They were able to accomplish achieving good image transmission through a large bundle of optical fibers for the first time without clading the fibers, and the second paper here describes that accomplishment. Kapany eventually coined the term fiber optics. Kapany and Hopkins, Van Heel and O'Brien were at serious odds with each other throughout and after the publications of these papers, something Hecht goes into in some detail.

Jeff Hecht, in his excellent book "City of Light, The Story of Fiber Optics" which much of this description is based on, offers this realization:

"Neither paper was quite sufficient by itself. Yet taken together, the two papers in one of the world's most widely read scientific journals launched modern fiber optics."

We have provided the abstract for each paper below from Nature for the reader.

Van Heel article abstract: "The transportation of optical images has been carried out hitherto with the aid of lenses or mirrors or both. As with all optical systems, aberrations are introduced and the parts have to be aligned carefully ; it seemed worth while, therefore, to search for a method by which no aberrations are introduced and which allows (strong) deviations from alignment without deterioration of the image. Consideration of the construction of the eye of some insects suggested another approach. If a bundle or sheaf of thin transparent fibres is cut off perpendicularly at both ends and an optical image is formed on one end, it will be seen at the other end, as the light entering one fibre can only leave this at the other end, provided leakage of light from one fibre to another of the bundle is prevented. Moreover, the cylindrical wall of each fibre must reflect the light as nearly completely as possible, because of the very numerous reflexions occurring when the fibres are thin compared to their length. Preliminary experiments, started in January 1950, have shown that coating the fibres with silver or any other metal yields an unsatisfactory transmission. A much better result was obtained when the fibres were coated with a layer of lower refractive index, which ensured total reflexion. This coating was isolated from the neighbouring fibres by a thin coat of black paint. In this way, flexible ‘image rods’ have been obtained with satisfactory transmission, a very good contrast in the end image, and with the possibility of using forms bent in any direction (up to at least 360°)."

Hopkins abstract: "AN optical unit has been devised which will convey optical images along a flexible axis. The unit comprises a bundle of fibres of glass, or other transparent material, and it therefore appears appropriate to introduce the term ‘fibrescope’ to denote it. An obvious use of the unit is to replace the train of lenses employed in conventional endoscopes. The existing instruments of this kind, for example, cystoscopes, gastroscopes and bronchoscopes, etc., consist of a train of copying lenses and intermediate field lenses. They are either rigid or have only limited flexibility. Moreover, the image quality of these systems is poor, since they consist only of positive lenses which give rise to a very large curvature of field. In existing gastroscopes the total number of lenses employed may be as many as fifty, and in consequence the light transmission is poor, due to the total glass path and the number of air–glass surfaces, in spite of blooming. Even more important in this respect, however, is the need to use small relative apertures for such instruments, this being necessary if acceptable definition is to be obtained with such large field curvature."

In Nature, issue 4392, Jan 2, 1954, Vol 173.

REFERENCES:
Hecht, Jeff, "City of Light The Story of Fiber Optics", pp 46-59.

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