Electrically balanced pyroelectric radiometer

Abstract

A TGS Pyroelcctric detector has been used for absolute measurements of low level optical radiation. The front electrode of the detector is used as: (i) a high efficiency radiation absorption film (ii) an electrode for the pyroelectric condenser; and (iii) as an electric heater for producing heating pulses. Radiation is chopped by a 20%open mechanical chopper. The pyroelectric signal of the detector contains pulses due to radiation and electric heating. These two pulses are balanced by a null detection method in a lock-in amplifier. Thus electrical power is matched with radiation power for the absolute measurement of the latter. The operating frequency of the detector lies between the thermal relaxation frequency and the electrical cut-off frequency. Applications of this radiometer include absolute measurements of black body radiation and spectral radiation.