Feedback stabilized digital infrared detector circuit

Claim 1

A digital control circuit operated by changes of radiation received by an infrared detector comprising: an infrared detector with first and second terminals which varies the current flowing through it based upon variations of radiation within its field of view with its first terminal interconnected with a circuit return; a first capacitor with first and second terminals the first terminal being connected to the second terminal of the infrared detector; a diode with a positive and a negative terminal and its negative terminal connected to the junction of the first capacitor and the infrared detector; a digital clock generator generating a clock pulse; a sample pulse generator connected to the output of the clock generator and generating a sample pulse synchronized to the clock pulse, the sample pulse being of sufficient voltage, current and pulse length to charge the first capacitor to a measurable voltage during the sample pulse length, and the sample generator pulse output being connected to the positive terminal of the diode; a first logic circuit, with an input and an output, which generates an output pulse on its output when the voltage on its input is raised to a specific level, the input of the first logic circuit being connected to the positive terminal of the diode and the output being interconnected with the second capacitor terminal; a reference pulse generator connected to the output of the clock generator and synchronized with the sample pulse generator, the reference pulse generator producing a reference pulse which begins during the sample pulse; and a trigger circuit, one input connected to the output of the reference pulse generator and another input to the output of the first logic circuit, the trigger circuit generating a signal on a first output to activate an external control circuit when the reference pulse and the output of the first logic circuit deviate in time by more than a preselected amount.