Viewfinder with long eye relief having framing and centering means

Claim 1

A VIEWFINDER COMPRISING IN AXIAL ALIGNMENT A NEGATIVE OBJECTIVE, MEANS ADJACENT TO THE NEGATIVE OBJECTIVE FOR DEFINING A RECTANGULAR FRAME, A POSITIVE EYEPIECE FOR RECEIVING LIGHT FROM THE SUBJECT BEING VIEWED THROUGH THE OBJECTIVE AND FOR APPROXIMATELY COLLIMATING SAID LIGHT AND MEANS WITH AN AXIALLY CENTERED RECTANGULAR APERTURE BEHIND THE EYEPIECE A DISTANCE AT LEAST HALF OF, AND AT MOST EQUAL TO, THE SEPARATION OF THE OBJECTIVE AND THE EYEPIECE FOR AUTOMATICALLY IDENTIFYING, TO AN OBSERVER WHOSE EYE IS HELD AT A DISTANCE FROM THE EYEPIECE GREATER THAN THE SEPARATION OF THE OBJECTIVE AND EYEPIECE, WHEN SAID EYE IS SUBSTANTIALLY ON AXIS, SAID EYEPIECE HAVING A DIAMETER NOT SUBSTANTIALLY GREATER THAN THAT OF THE NEGATIVE OBJECTIVE AND AT LEAST ONE-HALF THE DIAGONAL OF SAID RECTANGULAR FRAME SUCH THAT ALL OF SAID FRAME IS VISIBLE THERETHROUGH BY SAID EYE ON AXIS AT SAID DISTANCE.