Pulfrich, Carl

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PULFRICH, CARL

(b. Strässchen [near Burscheid], Solingen, Germany, 24 September 1858; d. Baltic sea, near Timmendorferstrand, Germany, 12 August 1927)

physics.

Pulfrich was an outstanding representative of the school of physics created by Ernst Abbe and a prominent expert in the field of photometry and refractometry. He is considered the father of stereophotogrammentry.

The son of a schoolteacher, Pulfrich attended the Realschule in Mulheim an der Ruhr and then studied physics, mathematics, and mineralogy at the University of Bonn. In 1881 he passed an examination enabling him to teach in secondary schools and in 1882 earned the doctorate under Clausius for his dissertation, “Photometrische Untersuchungen uber die Absorption des Lichtes in isotropen und anisotropen Medien.” From 1883 to 1889 he was an assistant to Clausius and then, after the latter’s death, to Hertz. In 1891 he married Hertz’s sister-in-law.

At Bonn, Pulfrich investigated the refraction of light in crystals, glasses, and fluids and constructed a total reflectometer and a refractometer. On the basis of this research he qualified in 1888 as a university lecturer; and in 1890 he met Abbe, who was then employed at the Zeiss Works in Jena. In the same year (1890) Pulfrich accepted an offer to works as a physicist, under Abbe’s direction, for the Zeiss company, where he was made head of the departments, a post he held for many years.

Pulfrich’s first task was to improve some of the instruments that Abbe had devised including the micrometer, dilatometer, and Abbe refractometer for liquids. In 1895 he designed, for use by chemists, an improved model of the latter device, which became known as “the Pulfrich.” He also constructed, in collaboration with R. Wollny, a butterfat refractometer; and he was instrumental in the development of heatproof glasses, which were manufactured at the Jena glasswork of Schott and Associates.

In 1899, at a scientific congress in Munich, Pulfrich presented the first model of a stereoscopic rangefinder with a staggered scale. He subsequently devoted himself completely to stereophotogrammetry. He introduced the so-called floating mark and constructed new surveying equipment and auxiliary devices, including the stereo comparator and stereo copying machine. (For these devices he employed the ideas of E. von Orel.) In 1925 Pulfrich devised a step photometer adapted to the range of sensitivity of the human eye. This photometer also finds application as a colorimeter and turbidimeter.

BIBLIOGRAPHY

I. Original Works. Pulfrich wrote approximately 100 papers and books. His major works include “Ein neues Totalreflectometer (I. Mitteilung),” inAnnalen der Physik und Chemie, n.s.30 (1887), 193-208, and Zeitschrift fur Instrumentenkunde,7 (1887), 16-27; “Das Totalreflectometer und seine Verwendbarkeit fur weisses Licht (II .Mitteilung),” ibid.,30 (1887), 487-502, and ibid.,7 (1887), 55-65; “Das Totalreflectometer (III. Mitteilung),” ibdi.,31 (1887), 724-736, and ibdi.,7 (1887), 392-396; “ein neues Refraktometer besonders zum Gebrauch fur Chemiker eingerichtet,” in Zeitschrift fur Instrumentenkunde,8 (1888), 47-53; Uber das Totalreflektometer und das Refraktometer fur Chemiker, ihre Verwendung in der Krystalloptik und zur Untersuchung der Lichbrechung von Flussigkeiten (Habilitationsschrift, Univ. of Bonn, 1888-1890; published in book form by W.Engelmann, Leipzig, 1890); and Universalapparat fur refraktometrische und spektrometrische Untersuchungen,” in Zettschrift fur Instrumentenkunde,15 (1895), 389-394.

Subsequent works are “Uber ein neues Refraktometer mit veranderlichem brechenden Winkel,” ibdi.,19 (1899), 335-339; “Uber den von der Firma Carl Zeiss in Jena hergestellten steroskopischen Entfernungsmesser. Vortrag, gehalten auf der Naturforscherversammlung in Munchen am 19. September 1899,” in Physikalische Zeitschrift,1 (1899),98; “Uber Zeitschrift fur Instrumentenkunde,21 (1901), 249-260; “Ueber neuere Anwendungen der Stereoskopie und uber einen hierfur bestimmten Stereo-Komparator,” ibid.,22 (1902),65-81,133-141,178-192,229-246; “The Stereoscope,” in Encyclopaedia Britannica, 11th ed. (1910); “Die “drehbare wandernde Marke,’ eine Neueinrichtung am Stereo-Komparator,” in Zeitschrift fur Instrumentenkunde, 34 (1914),221-223.

Pulfrich’s books on stereoscopy are Neue stereoskopische Methoden und Apparate fur die Zwecke der Astronmie, Topographie Methoden, pt. 1 (Berlin, 1903); Neue ateroskopisches Sehen und Apparate (Berlin, 1909); Stereoskopisches Sehen und Messen, mit einem Literaturverzeichnis der Arbeiten uber Stereoskopie etc. seit 1900 (Jena,1911); Uber die Photogrammetrie aus Luftfahrzeugen und die ihr dienenden Instrumente (Jena.1919); and Die Stereoskopie im Dienste der Photometrie und Pyrometrie (Berlin, 1923).

Pulfrich’s photometer was described in “Uber ein den Enpfindundsstufen des Auges tunlichst angepasstes Photometer, Stufenphoometer genannt, und uber seine Verendung als Farbmesser, Trubungsmesser, Kolloidometer, Kolorimeter und Vergleichsmikroskop,” in Zeitschrift fur Instrumentenkunde,45 (1925),35-44,61-70,109-120; and “Uber einen Zusatzapparat zum Stufenphotometer, der zur bequemeren Ermittelung des Farbtones einer Farbvorlage dient, und daran anschliessend Forderung eines gleichabstandigen Farbenkreises,’ ibdi.,45 (1925), 5212-530.

Pulfrich also wrote on “Methoden zur Bestimmung von Brechungsindizes,” in Handbuch der Physik, ed. by A. Winkelmann,2 (1893),302-344 (1st ed.); and2 (1906), 583-625 (2nd ed.). A biblography is given in Poggendroff, IV, 1199-1200; V, 1010-1011; VI, 2092; and VIIa, supp. 517, in obituaries below.

II. Secondary Literature. On Pulfrich and his work, see O.Lacmann, “Prof. Dr. Pulfrich zum Gedachtnis,” in Internationales Archiv Fur Photogrammetrie,7 , pt.2(1932), 1-7, with a selected bibliography on Pulfrich’s stereoscopic papers; F. Lowe, “Carl Pulfrich,” in Zeitschrift fur Instrumentenkunde, 47 (1927), 561-567, with a complete bibliography, “Carl Pulfrich,” in Vierteljahrsschrift der Astronomischen Gesellschaft, 63 (1928), 7-12, “Prof.Dr.Carl Pulfrich. Ein Gedachtnisblatt zur 25. Wiederkehr seines Todestages(12.August 1927),” in Monatsschrift fur Feinmechanik und Optik, 69 (1952), 147-148; F.Manek, “Pulfrich und der erste Stereoautograph Mod. 1908,” in Jenaer Jahrbuch(1958), pt. 2, 7-18, “Pulfrich und der Stereoautograph Modell 1909,” ibid.(1959), pt. 2, 7-23; “Pulfrich und die Stereoautographen Modell 1911 und Modell 1914,” ibid.(1960), pt. 2, 327-340; and F.Schneider, “Carl Pulfrich. Prof. Dr. Carl Pulfrich zuseinem 100. Geburtstag am 24.September 1958,’ in Jenaer Rundschau, 3 (1958), 127-128.