Terahertz pulsed spectroscopy apparatus and method

摘要

Apparatus for investigating an object 21 comprises a source 17 of terahertz radiation 18 for irradiating points on the object with pulses of radiation, the pulses comprising a plurality of frequencies in the range of 100 GHz to 100 THz, a detector 26 for detecting radiation 25 transmitted and/or reflected from the object to obtain a time domain waveform, means for irradiating a plurality of points on the object and means for combining time domain waveforms from each of the points to produce a time domain waveform for the object which has been averaged over the plurality of points. Methods of separating a portion of the radiation detected by the detector which corresponds to directly transmitted or reflected radiation and applying a Fourier transform to the remaining portion of the detected radiation, and using a diffuse irradiating beam of terahertz radiation by focussing the beam at a different point on or within the object to the point from which the transmitted or reflected radiation is detected are also disclosed.