Photometric device having greater response to a preferential central portion of a scene

Claim 1

A PHOTOMETRIC DEVICE COMPRISING A SINGLE LENS STRUCTURE FOR FORMING A SINGLE IMAGE OF A SCENE, A SINGLE MEANS RESPONSIVE TO THE LIGHT OF SAID IMAGE AND OPERABLE TO VARY AN ELECTRICAL SIGNAL IN ACCORDANCE WITH THE BRIGHTNESS THEREOF, SAID LIGHT RESPONSIVE MEANS INCLUDING MEANS FOR INTRODUCING A DIFFERENCE IN RESPONSE BETWEEN DIFFERENT PORTIONS OF SAID IMAGE SO THAT EACH LUMEN COMING FROM A PREFERENTIAL CENTRAL PORTION OF THE SAID IMAGE CORRESPONDING PREFERENTIAL CENTRAL PORTION OF SAID IMAGE WILL CAUSE A GREATER ELECTRICAL OUTPUT SIGNAL THAN EACH LUMEN COMING FROM THE REMAINING PORTION OF THE SCENE AND BEING IN A REMAINING PORTION OF SAID SAME IMAGE PRODUCED BY SAID SAME LENS STRUCTURE, SAID LIGHT RESPONSIVE MEANS INCLUDING A PHOTOELECTRIC CELL ONTO WHICH THE LIGHT OF SAID IMAGE IS DIRECTED AND FILTER MEANS SERVING AS SAID MEANS FOR INTRODUCING A DIFFERENCE IN RESPONSE AND CONSTRUCTED TO REDUCE THE BRIGHTNESS OF SAID REMAINING PORTION OF THE IMAGE RELATIVE TO SAID PREFERENTIAL CENTRAL PORTION, AND AN ELECTRICALLY ACTUATED UNIT OPERABLE BY SAID LIGHT RESPONSIVE MEANS IN RESPONSE TO LIGHT IN EACH OF SAID PORTIONS OF SAID IMAGE AND TO A GREATER EXTENT BY EACH LUMEN FROM SAID PREFERENTIAL CENTRAL PORTION OF THE SCENE THAN BY EACH LUMEN FROM SAID REMAINING PORTION THEREOF, SAID FILTER MEANS BEING LOCATED AT THE FOCAL PLANE OF SAID IMAGE PRODUCED BY SAID LENS STRUCTURE, AND SAID PHOTOELECTRIC CELL BEING LOCATED SLIGHTLY BEYOND SAID FILTER MEANS IN THE DIRECTION OF LIGHT TRAVEL.