Photometric device having optionally selective response to light on two photoresistive cells

Claim 1

IN A PHOTOMETRIC SYSTEM RESPONSIVE TO ILLUMINATION OF A PHOTOGRAPHIC SCENE, THE COMBINATION OF: FIRST AND SECOND PHOTORESISTIVE MEANS, EACH OF SAID MEANS HAVING AN ELECTRICAL RESISTANCE THAT DECREASES WITH INCREASING INTENSITY OF LIGHT INCIDENT THEREON, MEANS FOR ILLUMINATING ONE OF THE PHOTORESISTANCE MEANS WITH LIGHT OF INTENSITY SUBSTANTIALLY CORRESPONDING TO THE INTENSITY OF LIGHT INCIDENT UPON A SCENE, MEANS FOR SIMULTANEOUSLY ILLUMINATING THE OTHER PHOTORESISTIVE MEANS WITH LIGHT OF INTENSITY SUDSTANTIALLY CORRESPONDING TO THE AVERAGE INTENSITY OF LIGHT REFLECTED BY SAID SCENE, ELECTRIC POWER MEANS, ELECTRICALLY ACTUABLE MEANS FOR PRODUCING MECHANICAL RESPONSE TO ELECTRICAL CURRENT FLOWING THEREIN AND HAVING ELECTRICAL RESISTANCE TO PREDETERMINED VALVE, IMPEDANCE MEANS HAVING ELECTRICAL RESISTANCE SUBSTANTIALLY EQUAL TO SAID VALVE, CIRCUIT MEANS FORMING A MAIN CIRCUIT THAT INCLUDES IN SERIES THE POWER MEANS AND THE ELECTRICALLY ACTUATED MEANS SAID CIRCUIT MEANS INCLUDING FIRST SWITCH MEANS ACTUABLE SELECTIVELY TO THREE POSITIONS TO INSERT IN SAID MAIN CIRCUIT SAID ONE PHOTORESISTIVE MEANS, SAID OTHER PHOTORESISTANCE MEANS, AND BOTH OF SAID PHOTORESISTIVE MEANS, RESPECTIVELY, AND SECOND SWITCH MEANS ACTUATED WITH THE FIRST SWITCH MEANS FOR SELECTIVELY CONNECTING SAID IMPEDANCE MEANS IN SHUNT TO A PORTION OF SAID MAIN CIRCUIT THAT INCLUDES THE ELECTRICALLY ACTUATED MEANS UNIFORM RESPONSE OF SAID ELECTRICALLY ACTUATED MEANS UNIFORM IN ALL THREE POSITIONS OF THE FIRST SWITCH MEANS WHEN EVEN THE RESPECTIVE RESISTANCES OF THE TWO PHOTORESISTIVE MEANS ARE EQUAL.