Automatic exposure timing means

Claim 1

A PHOTOGRAPHIC ENLARGER COMPRISING A LIGHT PERMEABLE MEMBER ADAPTED TO SUPPORT A SHEET OF PHOTOGRAPHIC PAPER HAVING A SENSITIZED FACE AND A REAR FACE, MEANS INCLUDING A FIRST ELECTRIC LAMP FOR PROJECTING AN IMAGE TO BE PRINTED UPON SAID SENSITIZED FACE, A FIRST PHOTORESISTANCE ELEMENT SUPPORTED ADJACENT TO AND DIRECTED TOWARD SAID SHEET REAR FACE, MEANS INCLUDING A SOLENOID-ACTUATED SWITCH CONNECTING SAID PROJECTOR LAMP TO A SOURCE OF ELECTRIC CURRENT, A CAPACITOR CONNECTED TO SAID FIRST PHOTORESISTANCE ELEMENT WHEREBY THE CHARGE ON SAID CAPACITOR IS A FUNCTION OF THE INTEGRATED CURRENT THROUGH SAID PHOTORESISTANCE ELEMENT, MEANS RESPONSIVE TO THE CHARGE ON SAID CAPACITOR FOR CONTROLLING THE OPENING AND CLOSING OF SAID SWITCH AND A SECOND COMPENSATING PHOTORESISTANCE ELEMENT CONNECTED IN SHUNT WITH SAID CAPACITOR AND EXPOSED TO NON-IMAGE FORMING LIGHT TO A DISCHARGE SAID CAPACITOR AT A RATE IN ACCORDANCE WITH THE INTENSITY OF SAID NON-IMAGE-FORMING LIGHT INCIDENT ON SAID SECOND COMPENSATING PHOTORESISTANCE ELEMENT.