Unlike a binocular microscope, which feeds one image to both eyes, a the Leica Stereo Zoom 4 microscope gives each eye its own view, so that you see in three dimensions. Stereo microscopes are often used for dissection (hence the alternative term "dissecting microscope," not always stereo), inspecting electronic and machine shop work, and handling specimens to prepare slides for more powerful microscopes.
The Leica StereoZoom 4 gives an erect image, provides an ample working distance, and incorporates a zoom system in a self-contained optical "pod" which could be put on many different bases and mounts. StereoZoom 4's are abundant on eBay and in the rest of the secondhand market today.
The most common variety of "pod" zooms from 0.7× to 3×, although 1–3× and fixed-power versions exist. The eyepieces are normally 10×, non-compensating, with 23.2-mm tubes (the standard size on older microscopes). The eyepieces originally marketed with this microscope are an excellent match to it. Inexpensive non-compensating eyepieces from other vendors also work well.
It is quite possible to improvise a stand if you buy a "pod" by itself. For low-power examination of hand-held specimens, you don't actually need a focusing mechanism; just support the "pod" far enough above the table and hold the specimen underneath it.
You can use a desk lamp for illumination, but Bausch & Lomb and Leica made a special Nicholas (collimated-beam) illuminator that could be used separately or inserted into a hole in the back of the "pod" (Fig. 2). There is also a transillumination base for the StereoZoom 4 that accepts that same illuminator as its light source.
The Nicholas illuminator has one quirk: dust on the innermost lens surface, near the bulb, is projected sharply into the spot of light. Accordingly, a standard maintenance procedure is to open it up and swab the dust out.
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