June 2, 2021

Other Stero Microscopes

These are just some quick notes on other microscopes you may run into.

Leica

Among the best microscope optics that I have had a chance to look through has been a Leica, probably from the MZ series. The MZ6 provides a 4:1 zoom range, and higher numbers provide more range of zoom. The MZ6 and MZ8 are systems to look for on Ebay in the $1000 to $2000 range (new systems sell for about $3500).

Note that Leica picked up the old American Optical and Baush and Lomb lines and these inferior scopes may now be being sold under the Leica label, beware.

Zeiss

Among the very best, and very expensive.

Wild

Wild makes excellent scopes. They offer discrete magnifications rather than zoom. Every Wild scope I have had a chance to use has been excellent and the workmanship is superb.

Bausch and Lomb

The Bausch and Lomb stereozoom 7 is an old standby. I have been underwhelmed by this scope (and every Bausch and Lomb scope I have ever seen). It is an acceptable scope, but nothing special.

Bausch and Lomb makes a whole series of scopes, from economy student models to higher end models. The low end scopes use mirrors rather than prisms, with the degradation in contrast and image quality you might expect. I have been disappointed with all of the Bausch and Lomb optics I have had a chance to look through.

Enough said.

Meiji

Apparently Meiji microscopes can be good, but I have no experience with them.

Some notes on microscope eyepieces

You would like to think that all eyepieces would be interchangeable, as long as the tube diameter would fit properly into the microscope. This is sadly not the case. Some microscopes are designed with an objective that focuses at infinity, which makes the system independent of tube length, and much more flexible with accessories which may be used. The older and perhaps more common scheme is an objective which forms an image at some fixed distance, requiring a specific tube length.

One issue that crops up is the question of tube length. The most commonly encountered situation is an objective that provides a real image at what is refered to as a 160mm tube length. (This is refered to as the intermediate image) The eyepiece is simply a means of studying this real image, and most eyepieces yield a virtual image within the microscope, not a real image behind it. The other arrangement (I have only encountered it in the AO cycloptic microscope) is an objective that places the image at infinity. This of course requires a compatible eyepiece. Some people say this doesn't really make a difference, but my experiences with the cycloptic say otherwise.

I may be muddying the water here somewhat, so if some real expert is reading this and feels in a mood to educate and correct me, please get in touch.

There is another situation, that as far as I know never comes up with the relatively low magnification optical systems in stero microscopes. This is the issue of compensating eyepieces. Some optical systems use an objective which does not provide complete color correction. These systems require an eyepiece which corrects the problems introduced by the objective. Such eyepieces are called "compensating eyepieces" and are often labelled in some special way, often with a "K". This might be something to be aware of if you consider purchasing some used eyepieces. An objective which handles its own color correction issues without relying on help from the eyepiece is called an achromatic objective and is the only thing you can expect to encounter in the stereo microscope world.

Hardcore information on microscopy

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Tom's Mineralogy Info / tom@mmto.org