Nikon Multiphot modification
Here is an answer which may be helpful:
The focus adjustment on the lower standard of the Multiphot is a "fine focus" mechanism. "Coarse" focus is achieved by movement of the specimen platform which is attached to the Multiphot's diascopic base rather than the bellows.
Focus stacking is a software method of deconvolution of multiple views which gives a simulation of confocal imaging. The query is correct that if a specimen has so much depth that near and far focus points cannot be imaged with sharp focus via adjustment of the fine focus, the deconvolution will never be complete. In such a case, the SPECIMEN should be moved (as in the, long unavailable, Dynaphot system).
The rack and pinion on which the Multiphot specimen stage rides is not likely to be fine enough for the use in question. The design parameters of the Multiphot diascopic base and specimen stage was largely for histologic sections so the fine focus of the objective lens is more than sufficient. A finer mechanism for specimen movement should be easily available and adaptable to the situation encountered by the originator of the query, if somewhat pricey.
Howard J. Radzyner, FBCA
Visualization & Communication
for Medicine, Science, Law & Art
510 East 23rd Street
New York, NY 10010