Gearing for adjusting focal point of microscopes

摘要

The drive is actuated by a coarse adjustment knob (8) and a two-stage fine adjustment knob (7) with toothed gearing (1). The object plate (5) is raised and lowered by means of a rack (10) and pinion (6). The fine adjustment knob is fixed to a rotary axel (11) whose longitudinal mobility is varied between two positions stabilised by a spring-loaded ball (4) in circumferential grooves (2a,2b). The axel carries gear wheels (12,13) of different diameter which are engaged one at a time with the gearing. Alternatively the ratio may be continuously variable by means of a friction-wheel-and-cone transmission.