Hensoldt PROTAMI field microscope, ca. 1930
The years between the two world wars reflect the revival of the pocket microscope. This concept, originally, was first invented by Benjamin Martin in the early-mid 18th century (see here). As opposed to folding or case-mounted microscopes, a “pocket microscope” (German: taschenmikroskop) is a miniaturization of the standard bench-top configuration of the compound microscope, preserving most or all of the basic features (base, limb, stage, tube and varying magnifications). As opposed to the miniscope, which is basically just the full or partial optical system of a microscope miniaturized to pocket size, this feature makes the pocket microscope an interesting engineering challenge.
The heydays of the pocket microscope should be evaluated in their historical, social and economic context, rather than just from an object perspective. While in the late 19th century, small relatively inexpensive “drum microscopes” and miniscopes gained popularity in Europe and the USA, these instruments did not serve professional microscopists, and their mass production was intended for popular use.
The peak of success of the high-quality pocket microscopes covers approximately one decade, or slightly more, between the end of World War I and the Great Depression (i.e., roughly 1920 to 1930 and slightly later). Because this was mainly a German phenomenon, the rise of Nazi Germany in 1933 had a significant impact on the production of the taschenmikroskop, where production varied inversely with the growth of the German military.
This was an era of exploration when expeditions into the interior of Africa, Asia and South America became common, and field research under unorthodox conditions became popular. Small but powerful microscopes were essential to the explorer traveling in exotic countries. Such conditions required high-quality microscopes that could occupy a minimal space without significantly compromising their optical quality and magnification power.
Several innovative microscopes were developed, primarily by some of the top German optical makers (Earnst Leitz, Moritz Hensoldt & Sons, Carl Zeiss, Goerz, Georg Kremp, and Spindler & Hoyer). However, this requirement for civilian applications diminished almost as abruptly as it started, when the economic crisis of late 1929 was followed by the rise of Nazi Germany and the Nazi's disregard for the provisions of the Versailles Treaty. This led to the renewal of military production by the same optical companies. After World War II the production of pocket-sized microscopes for professional scientists almost completely diminished.
After World War I, most of the distinguished German optical makers were facing severe economic problems. The military prohibitions set on Germany in June 1919 by the Versailles Treaty brought the affluent army market with its demand for binoculars, telescopes, rifle scopes, periscopes etc, to an abrupt halt. Consequently, the optical companies were forced to seek new niches in the civilian domain. The obvious market lay in science and medicine. However, bench-top microscopes were already produced by many makers and the competition was harsh. German companies pushed their microscope divisions which, in response, developed innovative solutions for the mobile civilian scientific market with the development of compact, effective, and high-quality travel microscopes of professional caliber.
The “Protami" (professionellen- taschenmikroskop) is the high end model of the Hensoldt “Tami family”. It was introduced in 1925, with production continuing until the beginning of World War II. Design improvements occurred between the 1920s and 1930s. The example seen here is of the later improved model, portraying a wider knurled focusing collar than the original.
The Protami is constructed of brass with chrome and a japanned surface finish. Its saltshaker-like outer case is made of aluminum alloy finished in black-crinkled enamel. Compared to the two smaller Tami models, the Tami and Metatami, the Protami is provided with a three-objective turret, which makes changing magnifications an easy and speedy process. Together with the draw tubes, this provides a broad choice of magnifications ranging between 40X and a theoretical 1450X, when used in the oil immersion mode. When the lower achromatic objective "T" (for "Tami") is selected, it provides the magnification sequence of 45-250 times. The "M" ("Metami") marked dry objective provides the magnifications of 340-760X, as indicated by the scale on the tube. The "P" ("Protami") objective is an oil-immersion of 1/12" with the numerical aperture of 1.34, yielding the magnification range of 915-1450X. The microscope is equipped with an Abbe condenser with iris diaphragm, flip-up stage clip, substage slide-out canister containing a tube for immersion oil, and flat and concave mirrors on an adjustable arm. The stage can be flipped out of the optical path for easier replacement of the objectives.
The Protami was an expensive microscope for its time. In 1933, its price was 230 RM. As mentioned previously, this was more than twice the price of a standard laboratory-quality bench-top microscope, which averaged around 150-160 RM.
The primary weakness of the Protami, apart from its cost, is present only if the optional base is not available. Then, as with the Ultra-Lomara without the tiltable stand, the observer is forced to lean forward and look vertically down into the microscope, making it uncomfortable for prolonged use. Fortunately, the manufacturer was able to overcome this shortcoming by supplying an optional tilting base stand.
During World War II, the world's largest armies equipped their field hospitals with microscopes in the years that followed. The Imperial Japanese Army provided its troops with the Tiyoda "Mkatera" MKH folding microscope. US military hospitals often used the folding Spencer Model 60, and the Italian Army used the small Fratelli Koristka Regio Esercito - Sanità Miltare model. And the German Army, well the Wehrmacht, did not use the Protami despite its apparent suitability for the task. Instead, it was a full-sized, heavy, and robust Ernst Leitz desktop microscope that was used, carried in a heavy wooden box with steel protective corners. Though we may never know the reasons for this decision, possibly it was the performance and versatility of a desktop instrument compared to a field microscope or the extremely high price of the Protami that dictated this choice. Of course, it might not have been performance or cost, but corporate favoritism of the type we sometimes see from governments today, or perhaps some other reason.
© Microscope History all rights reserved
© Microscope History all rights reserved