MICROSCOPE-ANTIQUES.COM © 2013-21.
METALLURICAL MICROSCOPE:
c. 1922
Maker: BAUSCH & LOMB
Serial number:155229
DESCRIPTION
This compound microscope is designed for inspection of surfaces, especially metals. It is a portable form, so that it can be brought to the surface to be evaluated. Four adjustable screws allow it to rest on an uneven surface. Coarse focusing is by spiral rack and pinion, fine by long lever. A draw allows variation of tube length. It has an integrated jug handle
. The microscope was designed to be used with a vertical illuminator with self-contained electric illumination.
The instrument is signed BAUSCH & LOMB OPTICAL CO., Rochester New York U.S.A.
ACCESSORIES FOR THE BHM METALLURGICAL MICROSCOPE
Accessories currently with this microscope include the Vertical Illuminator with self-contained electric light source, one compensating eyepiece and seven metallurgical objectives. The short-barreled objectives are designed to be used without a coverslip. Five of these are labeled for tube length and with their focal length, and also their n.a.(numerical aperture). The remaining two are labeled only with the focal length.
Objectives with this microscope at this time include:
| FOCAL LENGTH | TUBE LENGTH | TYPE | N.A. |
|---|
| 2 mm | 165 mm | Apochromatic Oil Imm | 1.30 |
| 2.75 mm | 215 | Flourite Oil Imm | 1.25 |
4 mm | 165 mm | Apochromatic | 0.95 |
| 5.5 mm | 215 mm | Achromat | 0.65 |
| 8 mm | 165 mm | --- | 0.52 |
| 1 inch | --- | --- | --- |
| 1 ½ inch | --- | --- | --- |
The Vertical Illuminator makes use of a piece of clear glass similar to a coverslip as the reflector. With the reflector turned to about 45 degrees, light from the bulb is reflected downward by the reflector onto the object being studied and the light reflected off of it returns to pass back up the objective and through the reflector up to the eyepiece. The reflecting glass is controlled by a small knob allowing its angle to be adjusted by turning and its centration by pulling or pushing on the knob. As shown, the reflector is encased in a metal frame and can be removed by pulling it out when it is horizontal. After the reflector is removed, the support casing for it can be slid off the illuminator, providing access to its inside.
CONDITION:
This microscope is in good working condition, though there is no power supply for the bulb of the vertical illuminator. Draw tube, coarse focus and fine focus all work very well. The tilting glass disk in the vertical illuminator adjusts easily and is not cracked. There are scattered small areas of paint loss. There is no case associated with this microscope.
HISTORY, USE, AND EVOLUTION OF THE B & L METALLURGICAL MICROSCOPES
Metallurgical microscopes are not mentioned in B & L catalogs as late as 1911. By 1922 however, several different models were offered including this portable BHM model. It differs from the other metallurgical models in that the stage is in a fixed position.
On standard microscopes of that era, as in the BHM, focusing was achieved by movement of the optical tube, but for metallurgical microscopes, the stage was moved for coarse focusing. This was provided to allow the vertical illuminator to be lit by a fixed external light source, as moving the optical tube would move the illuminator away from the fixed light source. The vertical illuminator with built-in light source obviates the need for keeping the optical tube in the same position. This is the system which is used with the BHM since the stage is fixed by design.
