Focusing screen for reflex cameras having integral range finder means

Claim 1

An improved range finder type focusing screen for reflex camera comprising: a generally planar translucent member forming the body of said screen, said member having upper and lower surfaces; one of said surfaces defining a generally centrally disposed first area having a peripheral border, and a second area surrounding said first area and having a second peripheral border; said first area having a first plurality of microprisms formed on said surface, and oriented to refract light rays falling thereon along an axis substantially perpendicular to the plane of said translucent member in a first direction having a first vector component lying in said plane; said second area having a second plurality of microprisms oriented to refract light rays falling thereon along axes substantially perpendicular to said last mentioned plane in a second direction having a second vector component equal in magnitude to said first vector component and lying in said plane and extending in a direction opposite that of said first vector component; whereby portions of an out-of-focus image cast upon said first and second areas will appear mutually displaced along an axis parallel to that of said first and second vector components, and blurred to a degree depending upon the distance said portions are mutually displaced.