Ratio-recording spectrophotometer

Claim 1

IN A RATIO-RECORDING SPECTROPHOTOMETER, THE COMBINATION COMPRISING: OPTICAL MODULATING MEANS FOR PRODUCING A FIRST SERIES OF RADIATION PULSES INDICATIVE OF A CHARACTERISTIC OF A REFERENCE MATERIAL AND A SECOND SERIES OF RADIATION PULSES INDICATIVE OF THE SAME CHARACTERISTIC OF A SAMPLE MATERIAL; RADIATION DETECTOR MEANS FOR PRODUCING IN RESPONSE TO SAID RADIATION PULSES IMPINGING THEREON AN ELECTRICAL OUTPUT SIGNAL HAVING FIRST AND SECOND SERIES OF PULSES CORRESPONDING TO SAID FIRST AND SECOND SERIES OF RADIATION PULSED; AMPLIFIER MEANS COUPLED TO SAID DETECTOR MEANS FOR AMPLIFYING SAID OUTPUT SIGNAL, SAID AMPLIFIER MEANS HAVING BALANCED OUTPUTS; A PAIR OF SIGNAL INFORMATION STORAGE CHANNELS; DEMODULATING MEANS COUPLING SAID SIGNAL CHANNELS TO SAID AMPLIFIER MEANS, SAID DEMODULATING MEANS ACTING TO PERIODICALLY COUPLE SAID CHANNELS TO ONE OR THE OTHER OF SAID BALANCED OUTPUTS AND DECOUPLED THEM THEREFROM IN A MANNER WHEREBY THE PULSES OF SAID FIRST SERIES OF SAID DETECTOR SIGNAL PASS INTO THE FIRST OF SAID CHANNELS AND THE PULSES OF THE SECOND SERIES OF SAID DETECTOR SIGNAL PASS INTO THE SECOND OF SAID CHANNELS; AND MEANS FOR PERIODICALLY SAMPLING THE SIGNAL INFORMATION STORED IN SAID CHANNELS AND PRODUCING AN ELECTRICAL FEEDBACK SIGNAL PROPORTIONAL TO SAID STORED SIGNAL INFORMATION TO CANCEL AT LEAST A PORTION OF SAID DETECTOR SIGNAL WHEREBY ONLY THE DIFFERENCE BETWEEN SAID FEEDBACK SIGNAL AND SAID DETECTOR SIGNAL IS AMPLIFIED.