Stereo Microscope Part 3: Common Main Objective Stereo Microscopes
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Stereo Microscopy Stereo Microscope Part 3: Common Main Objective Stereo Microscopes 3rd Edition R. Jordan Kreindler (USA) Figure 56. Woven fabric pattern through Zeiss "Opton" CMO microscope 66 Stereo Microscopy ___________________________________________________________________ This paper is the third in a multi- part series on stereo microscopes, including their history, design, and, applications. The paper concludes with considerations for potential stereo microscope buyers. In this Part Common Main Objective (CMO) microscopes are discussed. ______________________________________________________________________________ Figure 57. From the Zeiss brochure: Microscopy from Carl Zeiss. Stemi DR, Stemi DV4, Stemi 2000 Stereomicroscopes, Courtesy, and with permission of Carl Zeiss Microscopy, LLC. A comparison of Greenough and CMO (Telescope) design microscopes 67 Stereo Microscopy The Common Main Objective (CMO) Stereo Microscope A comparison of the Greenough and CMO (called telescope design by Zeiss) designs is shown in Fig. 57. In CMO designs there are two distinct light paths through both halves of a relatively large common objective lens. This design can have the benefit of long working distances. The modern common main objective (CMO) concept, although this designation appeared later, appears to have been developed by Carl Zeiss, Jena 1938-1941 (Michel, 1962). Dr. Kurt Michel worked on the Praepariermikroskop "Citoplast" (Preparation and dissection microscope “Citoplast”) from its inception. He joined Zeiss' Microscope Department in 1934, and became its Vice Head in 1938. When first developed, the Citoplast was to be priced at 816 RM (Zeiss, 1942). However, in response to the German government's direction, commercial manufacturing of the Citoplast was delayed until after WW II, i.e., until 1946 (Zeiss, 1946). Zeiss' East German R&D department received a Citoplast on October 3, 1946, and another went to Moscow. According to Zeiss' internal documents, most shipments went to Russia. [Author: These were probably supplied to state run agencies.] In private email received from Berndt-Joachim Lau of Carl Zeiss (Lau, 2012), by the author, Herr Lau explained Zeiss' situation at the end of WW II as follows, In June 1945 the US Army took the action "We take the brain" before Jena was given to the Russians. At October 24, 1945 the Russian Army ordered the demounting of Zeiss factory and the deportation of ca. 800 Zeiss people to Soviet Union. The Russians viewed the movement of Zeiss factories, manufacturing equipment, and personal as appropriate reparations for their WW II costs. However, this was not the view shared by many of the affected Zeiss personnel. Some of Zeiss' relocated resources were used to establish the Kiev camera works, makers of the Zeiss Ikon and Contax. As noted above, the U.S. Army occupied Jena before the partition of Germany. They moved many of Zeiss, Jena's leading technicians, and upper management, to the Contessa plant in Stuttgart, West Germany. In 1947 this was the core team that formed the Zeiss-Opton Optische Werke Oberkochen GmbH in Oberkochen, West Germany. The first modern CMO was developed at Carl Zeiss, Jena decades before the first American CMO, the AO Cycloptic. The first Zeiss CMO microscopes appeared commercially in East Germany as the Zeiss "Citoplast", Fig. 58, and in West Germany, Figs. 59 and 60, under the Opton label. 68 Stereo Microscopy In his book Armin Herman (Hermann, 1991) mentions that the first West German Zeiss-Opton Stereomicroscope was given in a small ceremony on January 23, 1949 to Professor Bauersfeld on the occasion of his 70th birthday. The Opton CMO version was manufactured by the Opton-Optische Werstatte Oberkochen GmbH Zeiss factory at Oberkochen, West Germany. For a period, versions of this CMO microscope were made by both East and West German Zeiss companies. The Zeiss Opton-branded CMO was taller, wider, and heavier than most previous stereo microscopes. At 12 pounds, it weighed almost 50% more than the c. 1929 B&L Greenough microscope shown in Fig. 25. Production of the West German Opton version, ceased in 1954, when the name of the West German Zeiss company was changed to Carl Zeiss, about three years before the introduction of AO's Cycloptic (Orlowski, 2012), (Zeiss, undated), (Walker, 2011). An Opton-style CMO microscope continued in production by the West German Zeiss company until 1959, under the Carl Zeiss label. (Schulze, 2011, 2012). At least until the 1980s, Zeiss West Germany appears to have used CMO designs in their stereo microscopes, except for models 01, 02, I, Ib, III, and the D-series. 69 Stereo Microscopy Figure 58. from East German Citoplast brochure, date unknown Courtesy, and with permission, of Carl Zeiss Microscopy, LLC 70 Stereo Microscopy Figure 59. From West German Opton brochure (translated to English), date unknown, Courtesy, and with permission, of Carl Zeiss Microscopy, LLC 71 Stereo Microscopy Figure 60. Zeiss Opton-branded CMO Microscope 72 Stereo Microscopy Early model Zeiss CMO microscopes continued to be manufactured for some years. Sander (1994) in his interesting and informative Centennial Essay mentions that "many [Citoplast stereo microscopes] must still be in service", and examples of early East and West German Zeiss CMO microscopes are often seen for sale on eBay. The Citoplast morphed, sometime in the 1950/60s, to the Zeiss SM-XX (sometimes, perhaps inappropriately, called the SM 20), with only changes from the earlier design. The Citoplast and its derivative microscopes were popular in Eastern Bloc countries and China. The SM-XX started its life finished in black, sometime later its color was changed to off-white. Two separate Zeiss companies had developed in the aftermath of the Second World War. So, CMOs were manufactured by both Zeiss East and West German companies. Most East German models were made about 54 miles (about an 1-1/2 hour drive) from Berlin in Brandenburg, Germany in the city of Rathenow by the Optische Werke Rathenow. Rathenow had contained the only spectacle manufacturing facility in the GDR. It was integrated with Zeiss as the Kombinat VEB Carl Zeiss Jena after the close of WWII, possibly c. 1970. [As an aside, after the disintegration of the Soviet Union, a location near Rathenow was found to contain the graves of Adolph Hilter and some of his associates.] Shortly after the fall of the Berlin wall in November 1989, the two separate Zeiss companies began talks and reunited in the early 1990s after East Germany's first free elections. After the reunification of the East and West German Zeiss companies, the unified company introduced the first of the Stemi Greenough, stereo microscope, models. After Unification Kombinat VEB Carl Zeiss Jena became Zeiss Jena, Gesellschaft mit beschränkter Haftung (GmbH). In 1991 after a division of functional assets, the new microscopy group Carl Zeiss AG (Oberkochen) reunited the previous Zeiss company's microscopy groups and relocated back to Jena, Germany along with its planetarium group. The new combined Zeiss company designed a new logo combining at its top a portion of the square used by the West German company in its last logo before unification, and at the bottom the curve from the logo used by the East German company. 73 Stereo Microscopy Common Main Objective (CMO) and Greenough Pros and Cons Fig. 61 provides examples of Greenough and CMO microscopes, although not to scale. The Zeiss CMO is taller than the Leitz Greenough. Leitz Greenough design Zeiss CMO design Figure 61. Greenough and CMO stereo microscopes 74 Stereo Microscopy Each design has its strengths and weaknesses The Greenough design suffers, slightly, from "keystone" distortion, i.e., distortion due to the viewing angles involved. An exaggerated version of keystone distortion is produced when a projector is aimed at a steep angle to a wall so that the projected image has the shape of the "keystone" in an arch, that is a trapezoidal shape. This can result in focus distortion, where some portions of the image are slightly out of focus and may cause eyestrain for some users after extended viewing periods. CMO stereomicroscopes have parallel paths, i.e., for practical purposes the two eyes view images at right angles to the object plane, and so do not suffer from keystoning. Viewing objects with the eyes focused at infinity can, perhaps, be less stressful with continuous use. However, quality CMOs are expensive to make, are usually heavier, and have some optical problems of their own, see below. We usually see nearby objects with both eyes, at an angle, and not images in parallel. If we interpret the parallel images as coming into the eyes at an angle, this results in "perspective distortion", as the central portion of the object appears thicker than it actually is. For non-photographic use the CMO has two minor problems: (1) we are used to processing parallel paths for objects at infinity, not for nearby objects, so our minds normally process parallel images from nearby objects inappropriately, and (2) there is some degradation of images that pass through the edges of a lens. The first issue is not a problem in photography through the microscope where images are two dimensional, and the second problem can be minimized in trinocular photomicrography by using the objective lens so its optical center coincides with the, usually, single light path used for photography. Zeiss helped minimized the perception problems inherent in the CMO's design with their development of multi-element, non-APO, PLS objectives. 75 Stereo Microscopy AO's Cycloptic Microscope: The first American CMO American Optical (AO), hoped to dominate stereo microscope sales in the late 1950s, when they achieved a major landmark in American stereo microscope development. They brought out the Cycloptic microscope (Phillips, 2011, 2012), (NikonU, undated), the first American CMOs. The AO Cycloptic was designed on the Zeiss model. As with the Zeiss Citoplast, the microscope received images for both eyepieces through a bottom main objective, large enough to easily support two light paths.