Diaphragm control device for cameras

Abstract

A diaphragm control device for a lens exchangeable type camera includes diaphragm driving means providing a uniform speed over the entire diaphragm control range, so that accurate diaphragm control is achieved even in the vicinity of a fully open aperture value. The start position of the diaphragm drive means is determined such that the diaphragm control member of an exchangeable lens is engaged by a stopper to define a fully open aperture position in the course of return movement of the diaphragm drive means to the start position. A coupling spring coupling the diaphragm drive means with a diaphragm control member of a camera body as an integral unit is deformed to allow separation of the diaphragm drive means from the diaphragm control member of the camera body so that the diaphragm drive means can return to the start position after the engagement of the stopper with the diaphragm control member of the exchangeable lens. The loaded coupling spring serves, in cooperation with a stop-down drive spring, to accelerate the driving movement of the diaphragm driving means sharply, so that the driving speed is substantially uniform after the diaphragm drive means and the diaphragm control member of the camera body are again integrally intercoupled due to depletion of the stored energy of the coupling spring.