Zooming apparatus for a viewfinder optical system

Abstract

A camera having zoom lenses of a photographing optical system, zoom lenses of a viewfinder optical system, and a driving motor for driving both zoom lenses. A transmitting mechanism for transmitting the force of the driving motor to the zoom lenses of the viewfinder optical system having a gear train connected to the driving motor and a rotation cam which is provided coaxially with the last gear of the gear train to drive the zoom lenses of the viewfinder lens. A key projects from the end of the periphery of a rotation shaft included in the cam. The last gear is mounted around an end of the rotation shaft of the cam and has a key groove engaging the key. A play is provided between the key groove and the key. In carrying out a back focal distance compensation by reversing the driving motor a slight amount when a zooming operation is completed by moving the zoom lenses of the photographing optical system in a predetermined direction, a slight amount of the reverse rotation of the least gear of the gear train is absorbed by the play provided in the transmitting mechanism of the viewfinder optical system. Thus, the rotation cam is not rotated, i.e., the zoom lenses of the viewfinder optical system is not moved.