Viewfinder for camera with adjustable diopter

摘要

A viewfinder for a camera with an adjustable diopter includes an objective lens and an eyepiece lens each having an optical axis extending parallel to a longitudinal axis of the camera. Light rays from the objective lens are reflected by a mirror and directed in one direction parallel to a transverse axis of the camera onto a focusing screen to form an object image. A first triangular prism receives light rays from the object image and reflects and directs the received light rays in opposite direction parallel to the transverse axis. A second triangular prism receives light rays from the first prism and reflects and directs the received light rays in the direction parallel to the longitudinal axis and toward the eyepiece lens. The first prism is supported and guided for linear displacement along the transverse axis, while the second prism is fixed to the body frame of the camera. A control knob operable by the camera operator is interconnected with the first prism through an interconnection mechanism composed of a two-arm lever and a spring cooperating with the lever. The interconnection mechanism responds to the operation of the control knob by causing linear displacement of the first prism along the transverse axis so as to change optical distance between the focusing screen and the eyepiece lens to achieve adjustment in diopter of the viewfinder.