Terminology for types of fine focus mechanisms?

[josmann]

Hey folks,

Is there a term out there differentiating fine focus adjustment systems which do not also move the coarse focus knob? On some scopes the coarse/fine knobs appear directly coupled such that turning one turns the other. Other scopes (BH2 for instance) the fine focus will turn when the coarse focus is turned (at the same rotational rate, though) but the coarse focus will not turn when the fine focus is turned. I generally associate the latter with being a higher end feature as your reference points on the coarse knob don't move around. I'd like to know if there's a specific name or term for these approaches.

Thanks!

[MichaelG.]

In some cases [notably in microscopes by Vickers] the mechanisms are completely separate ... the fine-focus acting only upon the nosepiece.

I don’t know of any single term which would adequately distinguish between all variations upon the theme.

MichaelG.

[Alexander]

There are even more variants. Some Leitz microscopes had the fine and coarse focus coupled in a way that the coarse focus moved independent while the fine focus had a defined way after which it automatically activated the coarse focus. The SM-Lux had one single knob. Fine Focus was 3/4 of a revolution until coarse was activated. The Dialux and Diavert had separate knobs. Coarse was activated after 2 revolutions of the fine focus knob.

[microcosmos]

On my Radical RPL-3T, the coarse and fine focus knobs are not only separate but also turn in opposite directions (for the same direction of stage movement) for unknown reasons. This makes it very confusing and annoying when you switch between the two and also increases the risk of accidentally smashing a high-powered objective into the slide.

[Dubious]

There are even more variants. Some Leitz microscopes had the fine and coarse focus coupled in a way that the coarse focus moved independent while the fine focus had a defined way after which it automatically activated the coarse focus. The SM-Lux had one single knob. Fine Focus was 3/4 of a revolution until coarse was activated. The Dialux and Diavert had separate knobs. Coarse was activated after 2 revolutions of the fine focus knob.

The Leitz Laborlux 12 is like that--one knob for both. Not sure what to call it but it does work well ,although perhaps not the best system for stacking. Interestingly, the Laborux S, which is otherwise very similar and from the same era, has separate knobs for fine and course focus.