MICROSCOPE-ANTIQUES.COM © 2013-15.

MAKER: CARL ZEISS OPTISCHE WERKSTATAETTE

MODEL: LARGE 'STAND 1^b' (Earlier referred to as 1^c)

c. 1907

SIGNED: Carl Zeiss, Jena

SERIAL NUMBER: 43968

SERIAL NUMBER OF MECHANICAL STAGE: 'Nr.15480'

Please Click On Any Picture for a Larger Version

DESCRIPTION: The microscope sits on a horseshoe foot. This form of horseshoe, with rear extension, might be more properly termed 'Y'-shaped, but the 'horseshoe' designation has persisted.

Coarse focus is by diagonal rack and pinion. The coarse adjustment knob has a smaller secondary knob on the left side for rapidly changing the coarse adjustment; this knob can be changed to fit on either side of the microscope.

Fine focus is via the Berger side-fine-adjustment. The left fine focusing knob is graduated as the plate states, in 0.002 mm increments. Because of space limited on the plate by its retaining screw, the letters mm are on top of each other rather than next to each other as normally would be the case. The exact signature on the fine focus plate is: '1interv.' 0.002mm' (but the m's are on top of each other).

It was offered with options of three different stages, this example being equipped with the 'Large Mechanical Stage, No. 44.' shown to the right. The stage has vernier scale graduations in both X and Y axes. A third scale and vernier was added for recording the position of the movable 'check-piece' or slide holder, which secures the position of the left side of the slide. The right side slide holder also slides in the same groove. This allows the X and Y verniers to then be used as a 'finder' to locate a specific spot on the slide repeatedly. This stage also has rotational motion, with a locking screw knob. The rotating stage also has two centering screws with milled knobs. There is also a small lever to lock the mechanical stage forward and backward motion, a feature especially useful when the stand is inclined or even horizontal. Another stage, the 'Photomicrographic Stage' (also shown for comparison on the Zeiss Stage Page) was also offered as an option; this stage had a different kind of adjustment which assumed gross positioning of the slide by hand, and then only a fine adjustment via controls to allow the object to be carefully positioned for photography. This stand could also be provided with a rotating, but otherwise plain vulcanite stage with stage clips.

The substage has diagonal rack and pinion height adjustment. This example is equipped with the Abbe Swing-out Condenser, a plain condenser also being offered. The condenser apparatus currently on this microscope has only one iris diaphragm, below the condenser fitting. This iris can rotate, and via a small diagonal rack and pinion, be offset from center to allow variations in indirect illumination. The iris and the optical component (condenser) can be swung out of the optical axis separately as desired. The fitting that holds the condenser then remains in place to accept other accessories as desired.

The microscope has a graduated draw-tube which is graduated from 14 to 19 cm by 1 mm. There is no stop to hold it in fully extended, making substitution of the Bitumi binocular head simple. There is an extra wide main optical tube to facilitate photography.

The stand is supported between a double upright from the foot, and the inclination is both adjustable and can be secured at any inclination via a locking levered screw controlled from the back of the stage.

The gimballed substage mirror is double sided and planoconvex, extending down from the tailpiece; although gimballed, the distance of the mirror from the stage cannot be varied.

The microscope has a triple nosepiece and is currently equipped with three objectives:
'Carl Zeiss D 1536'
'Carl Zeiss A Z.L. 17.'
'Carl Zeiss Jena' (later insignia)'Homogene Immersion Tubus 160 mm 2mm n.A. 1.3'

Accompanying this microscope is a (later) model of the 'Bitumi' (also 'Bitukni') binocular accessory. This particular model of binocular accessory dates from after 1924, as an earlier model was pictured in the 1924 accessory catalog.

The many adjustments that have locking mechanisms made photography much easier.

HISTORY OF THIS MICROSCOPE AND THE '1^a', '1^b' AND '1^c'

THE BERGER FINE ADJUSTMENT:
This microscope was the first model (when it was called the 1c) to feature the Berger side-fine-adjustment mechanism. Max Berger described this device, the first good side fine adjustment made, in 1898 in the Zeitschrift fur Instrumentenkunde, vol. XVIII, 1898, pp. 129-133 This fine adjustment has advantages over prior designs of, while allowing adjustment from the side of the stand, it at the same time provided a low-friction and very fine control to the fine adjusment. It makes use of a fine screw, the end of which is attached to a gear; turning the knob turns a worm gear, which in turn activates the gear, and precisely turns the long screw. This method imparted a much finer control than a simple knob on the screw, as was the usual standard earlier. Another gear turning in an opposite direction, and engaging the same wormgear, is on the back side of the worm. The purpose of this gear was to limit the travel of the fine adjustment. To limit the fine adjustment, this gear, much wider than the one turning the focusing screw, is threaded and rides a fixed screw to rise or fall inside the stand until it reaches a limit to prevent the fine adjustment travel from being excessive. Backlash is prevented by a powerful spring holding the tube support down on the fine adjusting screw. The Zeiss catalog states that whereas the divisions on the milled knob of the older type of adjustment represented 0.005 mm of travel, the Berger knob divisions equalled 0.002 mm, less than half of that distance. By extrapolation, and knowing the refractive index of the object, an approximation of thickness of objects or coverslips could be made.

THE STANDS:
In the 1902 catalog, the three largest stands, designated 1a, 1b and 1c were quite different. As seen here to the left, the 1a and 1b utilized the older directly-adjusted vertical screw for fine adjustment, and the 1b was specifically designed for polarized light work. In additon, these stands, not intended for photography, had the usual narrow main optical tubes. The 1c, on the other hand, featured both the new Berger side-fine-adjustment, and a wider optical tube to facilitate photography; in fact some of these stands have the letters 'Ph' etched on the back of the foot, which indicated they were for 'photography and projection'. The 1c, as can be seen in the ad shown to the right, was promoted as a 'New Photomicrographic Stand.' The 1d in 1902 was the 'Brain Microscope' and had both the wide tube and Berger fine adjustment and was equipped with a huge stage for studying very large sections.
By the time that the 1906 catalog was released, the designations of 1a, 1b, and 1c were changed. At least in the French version of the 1906 catalog, all were equipped with the Berger fine adjustment. They were now all the same stand, virtually identical to the previously designated 1c, with the exception of the stage; 1a featured the rotating plain vulcanite (ebonite) stage, 1b the 'Large Mechanical Stage' and 1c the 'Photomicrographic Stage.' Even more confusing, although 1c was equipped for photomicrography, 1a could be equipped for this and when done so, was stand 1d. Likewise, 1b, the model featured on this web page, could also be offered with the photographic accessories becomming 1e! In the 1913 catalog this was again simplified to three letters 1a,1b,1c.
In the 1913 catalog, the microphotography accessories were simply offered separately. Apparently by 1906, the Berger fine focus and the wider optical tube were standard equipment for all the number 1 stands, the older fine focus and narrow tubes being abandoned on the largest stands. Whereas 1c was THE microphotographic stand in 1902, by 1906 although the 1c came with photomicrographic stage, the photographer had an option to add the photomicrographic accessories to any of these stands. This makes some sense because the photomicrographic stage has only limited distances for mechanical motion, and some may have preferred other options. To reduce confusion, the table below outlines these changes between 1902 and 1913, utilizing the three catalogs from 1902, 1906, and 1913. I am indebted to Alan Wisner for access to the 1906 and 1913 catalog entries and engravings.

YEAR	MODEL NUMBER
	1a				1b				1c				1d				1e
	TUBE	FINE FOCUS	STAGE		TUBE	FINE FOCUS	STAGE		TUBE	FINE FOCUS	STAGE		TUBE	FINE FOCUS	STAGE		TUBE	FINE FOCUS	STAGE
1902	NARROW	OLD	PLAIN REVOLVING OR LARGE MECHANICAL		NARROW	OLD	PLAIN REVOLVING OR LARGE MECHANICAL		WIDE	BERGER	PLAIN, OR LARGE MECHANICAL OR PHOTOGRAPHIC		WIDE	BERGER	LARGE PLAIN (BRAIN MICROSCOPE)		------	------	------
1906	WIDE	BERGER	PLAIN REVOLVING		WIDE	BERGER	LARGE MECHANICAL		WIDE	BERGER	PHOTOGRAPHIC		WIDE	BERGER	PLAIN REVOLVING (& WITH PHOTOACCESSORIES)		WIDE	BERGER	LARGE MECHANICAL (& WITH PHOTOACCESSORIES)
1913	WIDE	BERGER	PLAIN REVOLVING		WIDE	BERGER	LARGE MECHANICAL		WIDE	BERGER	PHOTOGRAPHIC		---	----	---		---	---	---

ABOUT THE STAGES:
Zeiss offered several stages for their microscopes. For the number 1 stand, there were three options as noted above. The plain stage featured its ability to rotate. The large mechanical stage could also rotate fully and had the usual X and Y movements and could be centered and locked in position as needed; this is the stage with the stand on this website. The photomicrographic stage also allowed movements in the X-axis but only 0.5 mm for a full turn of the knob, compared to 17 mm for the large mechanical stage. In the Y direction, the standard stage movement is 5 mm per complete turn of the knob, whereas on the photo stage, this movement is only 2 mm. Furthermore, the photostage Y movement is not straight but rather around an arc. Although X and Y controls on the large mechanical stage are completely separate, for the photo stage they are coaxial. The large mechanical and the photographic stage are both pictured in more detail on the Zeiss Stage Page here

THE BITUMI BINOCULAR:
Most binocular heads of the nineteenth and early twentieth centuries effected a change in tube length as the interocular distance was adjusted. In the 1920's Siedentopf developed a binocular head in which changing the interocular distance did not result in a change in tube length. This was important at high powers because objectives are designed for specific tube lengths and distortions are introduced if the tube length is changed. Although the early workers compensated for this with the use of correction collars on their objectives, eliminating this problem in the first place simplified higher power work. The original Bitumi used a system of pivoting eyepieces to eliminate the change in tube length seen with the types that extended the tubes on an angle, thereby changing the interocular distance. This resulted in unequal tube lengths for each eye however. As the prism for the right eye and left eye were stacked one on top of the other. The later version, seen here, compensated for changes in interocular distance by moving the prisms at the same time as the interocular distance was changed. The Bitumi head accompanying this instrument dating to after 1924, was a later version than the original, and also a later addition to this microscope. An example of the original version of the Bitumi can be seen on Alan Wisner's website here.

The author is greatly indebted to James Solliday, president of the Microscopical Society of So. California, as well as Alan Wisner, author of Antique-microscopes.com, for pointing out much of the historical and technical details, and helping to sort out the exact date of my microscope.