Abstract: The invention describes a focusing drive for optical instruments that has, in addition to a pinion (1) and toothed rack arrangement (1, 2), slide rods (4) as guidance means for continuously changing the relative position of optical assemblies with respect to one another. The toothed rack (2) has a plurality of support elements (3) that are arranged—for example in angled fashion—on either side of its longitudinal extent. The support elements (3) are designed so that they have a shallow S-shape in cross section. In addition, they are dimensioned in such a way that they touch the contact surface of the one housing module (5) only with their planar end regions (3a). The result is a resilient or flexing motion upon actuation of the pinion (1), thus achieving smooth and zero-backlash adjustment.

Abstract: The invention describes a focusing drive for optical instruments that has, in addition to a pinion (1) and toothed rack arrangement (1, 2), slide rods (4) as guidance means for continuously changing the relative position of optical assemblies with respect to one another. The toothed rack (2) has a plurality of support elements (3) that are arranged—for example in angled fashion—on either side of its longitudinal extent. The support elements (3) are designed so that they have a shallow S-shape in cross section. In addition, they are dimensioned in such a way that they touch the contact surface of the one housing module (5) only with their planar end regions (3a). The result is a resilient or flexing motion upon actuation of the pinion (1), thus achieving smooth and zero-backlash adjustment.