INFRARED DETECTOR SYSTEMS FOR HIGH DYNAMIC RANGE RADIOMETRY AND IMAGING

RESEARCH AND DEVELOPMENT WILL BE CARRIED OUT ON CRYOGENIC EXTRINSIC SILICON INFRARED (IR) DETECTOR SYSTEMS WHICH PERFORM INTENSITY-TO-FREQUENCY CONVERSION AT THE FOCAL PLANEVIA SIMPLE CIRCUITS WITH VERY LOW POWER CONSUMPTION. THE INCIDENT IR INTENSITY CONTROLS THE REPETITION RATE OF SHORT DURATION OUTPUT PULSES OVER A PULSE RATE DYNAMIC RANGE OF 106. PULSE HEIGHTS ARE TYPICALLY GREATER THAN 3 VOLTS SO THAT NO PREAMPLIFIERS ARE REQUIRED. EACH DETECTOR CAN DRIVEA SEPARATE LED SO THAT PULSE CODED IMAGE DATA CAN BE OPTICALLY TRANSMITTED OUT OF THE CRYOGENIC ENVIRONMENT. PULSE TIMING OR COUNTING PROVIDES ACCURATE MEANS OF SIGNAL DIGITIZATION. MEASUREMENTS OF PULSE RATE AS A FUNCTION OF INTENSITY OVER THE FULL DYNAMIC RANGE WILL BE CARRIED OUT AND COMPARED WITH A RECENTLY DEVELOPED THEORETICAL MODEL. THEORY INDICATES THE POSSIBILITY OF APPROXIMATELY LINEAR RESPONSE OVER THE FULL DYNAMIC RANGE. EXPERIMENTS AND MODELING WILL BE USED TO OPTIMIZE PERFORMANCE AND STUDY TRADEOFFS AMONG FIGURES OF MERIT. THE PROPOSED SYSTEMS WOULD BE USEFUL IN MANY INFRARED RADIOMETRIC AND IMAGING APPLICATIONS, INCLUDING SIMULTANEOUS MEASUREMENT OF INFRAREDSOURCE LUMINOSITIES RANGING OVER MANY ORDERS OF MAGNITUDE.