Electro-magnetic detection apparatus

摘要

An infrared or other electromagnetic radiation detector (282) disposed in a detector circuit generates an output signal (36). This signal represents the total radiation received by the detector, which is composed of a) light originating from a source and reflected from a sample (light to be detected) and b) light emitted by a controlled source (32). The detector is stabilised by using a part of the output signal from the detector as feedback to adjust the intensity of the controlled source. The detector is therefore stabilised by a negative feedback loop which maintains the overall illumination irradiating the detector (and consequently the detectors output signal (36)) at a constant predetermined level by the application of a bias voltage (39). The stabilisation tends to linearise and extend the frequency response of the detector to the radiation detected.