Optics in Sweden

Yngve Ohman

Scientific Research during the 18th and 19thCenturies and the Beginning of the 20th Century

Optics has old traditions in Sweden. During the18th century an important contribution to geomet-rical optics was made by S. Klingenstierna (1698-1765), Professor of Physics and Mathematics at theUniversity of Uppsala. In a paper published in 1754in Volume XV of the Transactions (Handlingar) ofthe Royal Swedish Academy of Sciences he presentedtheoretical considerations of great value for the trueunderstanding of the law of refraction. The viewsexpressed there differ from those of Newton, andthey initiated therefore an interesting scientific dis-cussion. Dollond, in his early constructions of ach-romatic telescopes, was considerably stimulated bythis discussion. The appearance of two later papers(1760 and 1762) on chromatic and aplanatic lensesled to considerable progress in the design and manu-facture of lenses. Therefore, Klingenstierna may be saidto have contributed in a valuable way to the inventionof the achromatic telescope.'

During the 19th century several Swedish names wereconnected with pioneering work in optics. The workcarried out in Uppsala by A. J. Angstr6m (1814-1874)has been considered of such fundamental importanceto optics that his name was honored in the selectionof the spectroscopic unit of wavelength. AnotherSwedish pioneer in spectroscopy was J. R. Rydberg(1854-1919), Professor of Physics at the University ofLund. His name, too, is familiar to most students ofphysics by the "Rydberg constant."

An important contribution in radiation-measuringtechniques was made in 1851 by A. F. Svanberg (1806-1857), Professor of Physics in Uppsala. He was thefirst to suggest the bolometer principle, developed laterby Langley into a high sensitivity measuring device.Important radiation-measuring instruments were de-veloped also by K. J. Angstr6m (1857-1910), the son of

The author is at the Stockholm Observatory, Saltsjobaden,Sweden.

Received 1 November 1961.

A. J. Angstr6m. In fact his pyrheliometer of 1896is still considered one of the best instruments whenmeasuring the solar constant of radiation.

At the end of the 19th century and the beginning ofthe 20th, geometrical optics had a prominent repre-sentative in Sweden in A. Gullstrand (1862-1930).Though originally a professor of ophthalmology hedevoted much of his time to mathematics and made aseries of important contributions to the mathematicaltheory of aberrations including those of high order. Healso worked on systems without a common axis, andshowed that the eye itself sometimes constitutes such asystem. In fact he presented very complete data on allthe aberrations of the eye, including effects producedby the motion of the eye itself.

Gullstrand was able to make a very complete explora-tion of the general laws of image-forming systems andarrived at results of great practical use. A mostfruitful collaboration was established with Carl Zeissin Jena ("Die Gullstrandschen Stargldser mit aspharis-chen Flachen," "Das grosse Gullstrandsche Ophthal-moskop," "Monokulares Handophthalmoskop nachGullstrand," etc.).

Gullstrand was awarded the Nobel Prize for medicinein 1911 for his achievements in ophthalmology, and in1914 he was awarded a personal professorship at theUniversity of Uppsala in physiological and physicaloptics.

The mathematical treatment in Gullstrand's papersis sometimes laborious and difficult to follow owing toa strictly geometrical procedure. As expressed byBorn2 : "It is to be admired that Gullstrand was ableto establish in this way fundamental laws of generalvalidity." By considering instead the characteristicfunction (Brun's Eikonal of 1895 etc.) M. Herzbergerand others have later given a somewhat more aptdescription of some of the results achieved by Gull-strand. According to Born2 it seems that Gullstranddid not have full confidence in this method of approachin the case of systems without a common axis (see alsoref. 3).

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Recent Work and Current Research

A considerable part of the optical research in Swedenduring the present century has some direct or indirectconnection with the name of Manne Siegbahn. Pro-fessor Siegbahn received the Nobel Prize for physics in1925 for his spectroscopic discoveries and studies ofx-ray phenomena. Among important contributionsmade by Siegbahn in the field of optics may be men-tioned the design of excellent grating-ruling machines.His interest in ruling gratings originated in about1919, when he succeeded Rydberg as Professor ofPhysics at the University of Lund. The first machinehe designed was completed shortly after he had movedto the University of Uppsala in 1923. His gratingswere intended first for x-ray analysis, but with the crea-tion in 1937 of the "Forskningsinstitutet fr Fysik" inStockholm he could soon supply Swedish optical re-search and also foreign research centers with highquality gratings.

In this field most valuable contributions have alsobeen made by E. Hulth6n, Professor of Physics at theUniversity of Stockholm, who has tried recently, withmuch success, the principle of repeated reflections forthe purpose of increasing the resolving power of grat-ings. For similar purposes he has made promisingexperiments with "refraction gratings."

Important contributions to ultraviolet spectroscopytechnique have been made at Uppsala and Lund byB. Edl6n. Among contributions in the field of spec-troscopic design should be mentioned also the workcarried out by H. Lundegtrdh at Ultuna, Uppsala.

At "Forskningsinstitutet fr Fysik" and at the Geo-graphical Survey Office in Stockholm Erik Bergstrandhas developed a new and very accurate method ofdetermining the velocity of light. The method hasfound valuable practical application in the construc-tion of a "geodimeter" for geodetic field work.

An event which, during the last ten years, has meantconsiderable development of optical research in Swedenwas the creation of The Institute of Optical Research.Already in 1948 a proposal had been made by M.Siegbahn, through the Swedish Natural ScienceResearch Council and the Swedish Council of Tech-nical Research, that an Institute of Optics should beestablished at the Royal Institute of Technology inStockholm. Such an institute had de facto been inoperation since 1950, with E. Ingelstam as director ofresearch. But it was not until 1955 that the Govern-ment guaranteed the permanent character of thisinstitution. According to present rules some mem-bers of the council are nominated by the Governmentand some by a special committee representing Swedishoptical industries and other institutions.

Though only slightly more than ten years haveelapsed since optical research was started at the insti-

tute, a considerable number of investigations have al-ready been completed there by Ingelstam and his col-laborators (O. Bryngdahl, E. Djurle, L. 0. Hendeberg,P. Hjelmstrom, L. Huldt, L. Johansson-Sjbfall, P.Lindberg, and others). Important scientific contri-butions with practical applications have been made,especially in the field of phase contrast technique, andin the design of improved refractometers and interfer-ence microscopes. Valuable contributions to modernprogress in the field of optical image transfer havealso been presented, and the first European ap-paratus for the measurement of transfer functions wasdesigned at the Institute as long ago as 1951. Severalimportant papers have been devoted to the opticalproperties of semiconductors (Huldt) etc., and a groupis doing research in the field of evaporated thin filmsfor use in optics.

The Institute has more and more become the Swedishcenter of optics with intimate connections with cor-responding institutions abroad. In 1959 the Inter-national Commission of Optics held a conference there,and on this occasion Ingelstam was nominated Presi-dent of the ICO. He had been Vice-President of thesame Commission and for many years the executivesecretary of its Swedish national committee.

Among scientific institutions in Sweden where appliedoptical research is being carried on, mention should alsobe made of the institutions for geodetic sciences and forphotography at the Royal Institute of Technology,the Research Institute of National Defence (high-speedphotography, infrared detectors etc.), and the institu-tion for teletechnics (H. Wallman) at Chalmers Tech-nical University in Gothenburg. Special optical designhas been made in connection with some of the chemicaland medical institutions and in several other centers ofresearch.

Finally, reference should be made to the astronomicalinstitutions in Sweden. B. Lindblad, director of theStockholm Observatory in Saltsjbbaden (who once upona time worked in Gullstrand's calculating bureau inUppsala), has always been interested in Swedish opticaldesign, and has taken an active part in the creation of theSwedish Institute of Optics. At the Observatory he haserected an optical workshop for grinding and aluminiz-ing. Several Swedish institutions have had large mirrorsand plates coated here. This work has been per-formed under the supervision of J. Ramberg who hastaken an active part in the design of new instru-ments for the Observatory. He is a member of thespecial instrument commission working out plans forthe European observatory in the southern hemisphere.Various kinds of auxiliary optical instruments have beendesigned at the Stockholm Observatory by the presentwriter, such as the birefringent filter (independent of,though somewhat later than, Lyot), polarigraphs, aphotoelectric clorimeter, visual photometers in solar

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research (in use at the Swedish solar observatory inAnacapri), and thermomagnetic radiation measuringdevice using gadolinium, etc.

At the astronomical observatory in Uppsala an opticalworkshop was erected by the former director, G. Malm-quist, and optical grinding and aluminizing of largemirrors has been performed there under the supervisionof A. Wallenquist in connection with the installationof a large Schmidt telescope at Kvistaberg.

Important constructions of photoelectric devicesfor different purposes have been made at the astronomi-cal observatory in Lund, in collaboration with thePhysical Institute.

Optical Industries in Sweden

Though glass-making has old traditions in Sweden,it was not until this century that large-scale productionof optical products began. The first manufacture ofoptical products is connected with the name of G.Dalen, the Swedish inventor who was awarded theNobel prize for physics in 1912 for his automaticlightsensitive shutter for lighthouses. Dalen becamePresident of AB Gasaccumulator (AGA) in 1909, andsince about that year lenses and prisms have beenmanufactured on a large scale by this company.

A new and much more important period of develop-ment in Swedish optical manufacturing started duringWorld War II. Three different companies-Aga,Jungnerbolaget, and AB G. Arehn-made greatinvestments for the purpose of producing opticalproducts of the highest possible quality on a large scale.

Of these companies Aga and Jungner are still working inthis area with a good capacity. In the Aga companythe late E. Aulin was for many years the scientificauthority on problems related to optics. With greatgenerosity he offered his services not only to his owncompany but also gave much valuable help and adviceto many Swedish scientific institutions. In this wayhe should be given considerable credit for much of theprogress made in Swedish optics during the last twodecades.

The Jungnerbolaget has also been fortunate in havingat their disposal very able specialists in optical design,and has svcceeded in manufacturing products ofvery high precision.

Another company which has meant much to Swedishoptics during the last decades is the LumalampanAB. The research department of this company hasoffered its services to many of the scientific institutionsof Sweden.

All the three companies, Aga, Jungner, and Luma,have intimate connections with the Institute of Opticsin Stockholm and have given support to the activitiesof this institute.

References1. N. V. E. Nordenmark and J. Nordstrom, Lychnos p. 1

(1938); ibid. p. 313 (1939).2. M. Born, Optik (Springer, Berlin, 1933; Edwards, Ann

Arbor, Mich., 1943), p. 106.3. C. W. Oseen, Minnesteckning over Gullstrand, KungI. Sven-

ska Vetenskapsakademiens Levnadsteckningar 6, 2, No. 107,1935.

VIENNA WMO AUGUST 1961Professor .ngstromStockholm andfriends includingD. Q. Wark Wash-ington DC and W.Morikofer Davosduring a convivialinterlude in Vienna

More bon vivantsin Vienna August1961 including F.Steinhauser Vienna,Dr. and Mrs. H.J.Bolle Munich, Mrs.Morikofer Davos,S.D. SmithReading,and C.D. RodgersCambridge Univer-

See page 379 for report. sity

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