Acute focus is necessary in order to achieve the maximum resolution of optical devices used to enhance human vision, such as monoculars, binoculars, telescopes, and microscopes. In practice, acute focus is achieved by a step-wise method, frequently known as "rocking" . During the rocking method, a focusing mechanism is moved in one direction until an image comes into focus, and then beyond the point of focus to the point where the image begins to degrade. The direction of focus is then reversed, and the process is repeated until the operator has established that the best possible image has been achieved. The nature of rocking can cause the components of an optical device to experience backlash, which can be defined as the play resulting from loose connections between mechanical elements in the optical device. Backlash can be particularly problematic in the focusing mechanism of an optical device. Current focusing devices which employ screw threads or rack and pinion gears are particularly susceptible to backlash.