Means for automatically controlling the exposure time of charge carrier beam apparatu

Claim 1

APPARATUS FOR AUTOMATICALLY CONTROLLING EXPOSURE TIME OF FILMS TO THE ELECTRON BEAM OF AN ELECTRON MICROSCOPE WHICH IS PROVIDED WITH AN ELECTRON BEAM GENERATOR TO GENERATE SAID ELECTRON BEAM, AN OBJECT THE ENLARGED IMAGE OF WHICH IS TO BE STUDIED MOUNTED IN THE PATH OF SAID ELECTRON BEAM, MEANS FOR MOUNTING A PHOTOGRAPHIC FILM AND POSITIONING SAID FILM IN THE PATH OF THE ELECTRON BEAM, A FLUORESCENT SCREEN HINGEDLY MOUNTED AND BEING SWINGABLE ABOUT SAID HINGE FROM A FIRST POSITION OVERLYING SAID FILM AND INTERRUPTING SAID BEAM FROM IMPINGING ON SAID FILM TO A SECOND POSITION OUT OF THE PATH OF THE ELECTRON BEAM, THE ELECTRON OPTICAL LENSES CONSISTING OF AT LEAST ONE OBJECTIVE AND ONE PROJECTING LENS FOR PRODUCING AN ENLARGED IMAGE OF SAID OBJECT ON SAID FLUORESCENT SCREEN WHEN SAID FLUORESCENT SCREEN IS IN SAID FIRST POSITION, A SHUTTER ARRANGED IN FRONT OF SAID FLUORESCENT SCREEN, AND RELAY MEANS TO OPEN AND CLOSE SAID SHUTTER, COMPRISING A COLLECTOR ELECTRODE MOUNTED ON SAID FLUORESCENT SCREEN, STORAGE MEANS COUPLED TO SAID COLLECTOR ELECTRODE AND SERVING TO STORE A SIGNAL THE AMPLITUDE OF WHICH IS PROPORTIONAL TO THE SIGNAL DELIVERED BY THE COLLECTOR ELECTRODE, MEANS TO CONVERT THE STORAGE SIGNAL INTO A TIMING SIGNAL, THE DURATION OF WHICH IS INVERSELY PROPORTIONAL TO THE AMPLITUDE OF THE STORED SIGNAL, MEANS FOR CLOSING SAID SHUTTER AND FOR UNCOUPLING SAID STORAGE MEANS FROM SAID COLLECTOR ELECTRODE AND FOR COUPLING SAID STORAGE MEANS TO SAID CONVERTING MEANS WHEN SAID FLUORESCENT SCREEN IS SWUNG FROM SAID FIRST POSITION TO SAID SECOND POSITION, AND MEANS COUPLED TO SAID CONVERTING MEANS AND SERVING TO OPEN SAID SHUTTER AFTER THE FLUORESCENT SCREEN HAS REACHED SAID SECOND POSITION AND TO SHUT SAID SHUTTER AT THE END OF SAID TIMING SIGNAL.