Device for splitting the light beam incident

摘要

This invention relates to a device for splitting a light beam applicable to a light metering apparatus of a single lens reflex camera. Having a diffraction lattice structure built in the condenser lens, this device has both a beam splitting function and a light condensing function. More in detail, this device includes a condenser lens section and a transparent sheet having a diffraction lattice in one portion which are interconnect by having a lower index layer inbetween. One portion of the light that passes through the taking lens of the camera and is incident on said transparent sheet is diffracted by said diffraction lattice, and further the diffracted light is totally reflected at the boundary surface between said lower index layer and transparent sheet, and transmitted to the end surface of the transparent sheet when it is detected.