Field Microscope
weight of the microscope as pictured, with lenses and fl ashlight with two AA batteries, is only 1 pound, 6 oz. (614 grams). Its overall sturdiness and simplicity of design (it is about as basic as a compound microscope can get) meet the portability and ruggedness criteria. T is device is generally off ered as pictured in Figure 1 , with the removable fl ashlight attachment, a standard 10× eyepiece, and either a 4× or 10× objective. Both lenses are industry- standard; the widefi eld eyepiece fi ts in a 23 mm body tube, and the achromat objective is RMS-threaded and fi ts on the nosepiece of any standard microscope. T is meets criterion #4. T e eyepiece comes with a measuring reticle calibrated as a line divided into 100 parts so that with a 10× objective, specimens in the fi eld of view can be directly measured with reasonable precision in hundredths of a millimeter.
Most models of this microscope come equipped with a sliding collar on the body tube, which can be tightened with a thumb-screw, setting it to a fi xed height to avoid focal driſt during photography or damage to an objective or specimen from focusing too far downward. T e collar ensures photographic stability even with heavier cameras, thus meeting criterion #5. T e epi-illuminating fl ashlight slides into a socket on a cantilevered arm that is easily detached for storage and transport. T is microscope was designed for use in machine shops and other places where handy portability for inspecting materials and measuring tight tolerances is required. Illumination of surfaces from above the specimen is its primary purpose. T at utility ensures that it is not likely to be a discontinued model (meeting criterion #9). But for fi eld microscopy, the rugged appeal of this simple microscope is off set by its awkwardness for transmitted light applications, with no obvious way to position a glass slide under the objective. Microscope stage platform . The authors incorporated transmitted light capability and easy slide positioning by designing a stage platform to be made out of readily available carpentry materials: wooden board, dowels, wood screws, insulator strips, and metal washers. Fabrication required only a table saw, a drill press, and a router. These materials are available at any lumberyard or home repair center, and, if not personally owned, the tools can be used at a hobby center or high school woodshop. A little woodshop training or help from a skilled woodworker is helpful. In my case, I had the basic tools but also had significant help from co-author Robert Hoelter, who is an experienced tool-and- die-shop technician. T e basic idea is modeled on Quekett’s design for a single-lens dissection microscope [ 1 ] illustrated in Figure 2 . T e Quekett design is a simple platform with four legs and a hole in the table surface to allow light from below to shine up through a specimen. T e authors modifi ed this design so that the stage itself elevates a compound “shop inspection” microscope on a pair of rails running along two edges of a rectangular lower plain on which a microscope slide can be positioned (see Figure 3 ). T e microscope is held in position by a pair of insulation strips with rubber edging, running above the rails. T ese allow the microscope to be slid into position above the central light hole while stabilizing the microscope from lateral movement or tipping over during use.
38 Figure 2 : Quekett’s single-lens dissection microscope and platform [ 1 ].
Figure 3 : Do-it-yourself platform stage for the shop inspection microscope.
The stage is fashioned from standard 1" × 4" wood board (preferably a hardwood, but even PVC boarding would work) cut to a 5" length. Using a router, the centered section stripe is cut down the length of the board segment, 1/4" deep × 2 1/2" wide. This is the exact outer diameter of the circular bottom of the shop-inspection microscope stand. Then a
www.microscopy-today.com • 2015 July
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