Automatic optical pyrometer system with automatic gain control

Claim 1

AN OPTICAL PYROMETER SYSTEM COMPRISING: A REFERENCE SOURCE AND A TARGET SOURCE, MODULATOR MEANS FOR CYCLICALLY MODULATING RADIANT ENERGY FROM SAID REFERENCE SOURCE AND FROM SAID TARGET SOURCE, MEANS FOR PRODUCING AN AC SUGNAL OF AMPLITUDE DEPENDENT UPON THE DIFFERENCE BETWEEN THE MODULATED RADIANT ENERGIES FROM SAID SOURCES AND OF PHASE DEPENDENT UPON WHICH OF SAID ENERGIES IS THE GREATER, MEANS FOR PRODUCING TIMING PULSES PHASE-LOCKED TO SAID AC SIGNAL, DEMODULATOR MEANS CONTROLLED BY SAID TIMING PULSES FOR PRODUCING UNIDRECTIONAL PULSES OF AMPLITUDE AND POLARITY DEPENDENT UPON THE AMPLITUDE AND PHASE OF SAID AC SIGNAL, INTEGRATOR MEANS TO WHICH SAID UNIDIRECTIONAL PULSES ARE SUPPLIED TO ADJUST THE TEMPERATURE OF ONE OF SAID SOURCES FOR MATCHING OF SAID ENERGIES, AND AN AUTOMATIC GAIN-CONTROL CIRCUIT RESPONSIVE TO CHANGES IN THE RADIANT ENERGY LEVEL AT WHICH MATCHING IS EFFECTED FOR VARYING THE DURATION OF SAID UNIDIRECTIONAL PULSES IN COMPENSATION FOR THE DISPROPORTIONATE CHANGE OF RADIANT ENERGY WITH CHANGE OF TEMPERATURE AT DIFFERENT RADIANT ENERGY LEVELS.