Concentric drums target support system for ophthalmic instrument

Abstract

A compact refraction instrument for use in both the objective and subjective examination of human eyes. The instrument incorporates an alignment mode, a retinoscopy mode, a distance mode and near mode. For carrying out the functions associated with these modes, the instrument includes a Brewster stereoscope and a system for supporting a plurality of binocular/monocular vision testing slides. Positioned along the pair of optical paths between the Brewster stereoscope and the slide supporting system are: a first mask/septum system; a mode change system; a second mask/septum system; and a horizontal/vertical target mask system. The instrument also includes a refractor system and apparatus for suspending the refractor system in the optical paths before the Brewster stereoscope. The slide supporting system includes two rotatable concentric drums. Each drum is formed from a plurality of vision testing slide holders supported between a pair of ring gear members. The drums are supported by at least two shafts. The first shaft includes gearing which cooperates with at least one of the ring gear members of the inner drum and rollers which support the outer drum. The second shaft includes gearing which cooperates with at least one of the ring gear members of the outer drum and rollers which support the inner drum. Preferably, third and fourth support shafts are also included which have rollers thereon that are biased into engagement with the drums. The apparatus for rotating the drums includes stepping motors.

Dependencies are inferred from the claim text.