Automatic gain control for photomultiplier tubes employing a monitoring photocell

Claim 1

IN A PHOTOMETER HAVING A PULSED LIGHT SOURCE FOR ALTERNATELY ILLUMINATING STANDARD AND UNKNOWN SAMPLE MATERIALS AND AT LEAST ONE MAIN PHOTOSENSOR FOR DETECTING THE PULSES OF LIGHT DIRECTED THERETO FROM SAID STANDARD AND UNKNOWN SAMPLE MATERIALS, MEANS FOR REDUCING THE PHOTOMETER OUTPUT NOISE ERROR RESULTING FROM VARIATIONS IN OUTPUT AMPLITUDE OF THE LIGHT PULSES PRODUCED BY SAID SOURCE, SAID MEANS COMPRISING: PULSE LIGHT MONITORING MEANS FOR PRODUCING A CONTROL SIGNAL PROPORTIONAL IN AMPLITUDE TO THE LIGHT OUTPUT FROM SAID LIGHT SOURCE, SAID MEANS INCLUDING A MONITORING PHOTOSENSOR WITH OPTICAL MEANS FOR IMAGING A PORTION OF THE LIGHT PRODUCED BY SAID PULSED LIGHT SOURCE ON SAID MONITORING PHOTOSENSOR, AND GAIN MODULATION MEANS RESPONSIVE TO SAID CONTROL SIGNAL FOR VARYING THE AMPLITUDE OF THE OUTPUT SIGNAL FROM SAID MAIN PHOTOSENSOR INVERSELY AS A FUNCTION OF THE AMPLITUDE OF SAID OF SAID CONTROL SIGNAL.