Cushman, Darby & Cushman
Attachment lens system for single-lens reflex cameras
 An attachment lens system for single-lens reflex cameras capable of being interposed between an ordinary interchangeable lens system and camera body and formed with a negative lens component, a beam splitter arranged at the image side of the negative lens component and a positive lens component arranged at the image side of the beam splitter, in order to enable the use of an ordinary interchangeable lens system as an interchangeable lens system provided with a focus detection optical system for auto-focus. The light from an object which has passed a master lens is divided by the beam splitter so as to be guided onto the film face or finder screen and to the focus detection means. 
Olympus Optical Co., Ltd.
G G G
G02B G02B G03B
inventional inventional inventional
Toru
Fujii