Patent ID: 8138477
Filing Date: 2012-03-20
Classification: G01J,G01N

Abstract:
1. Apparatus for measurement of a sample, comprising: means for generating electromagnetic radiation comprising a photoconductive device, the generating means being arranged to generate an output signal comprising electromagnetic radiation in dependence upon radiation received by the photoconductive device and to transmit the output signal towards a sample space; a first radiation source and a second radiation source, arranged such that the radiation received by the photoconductive device comprises a mixture of radiation from the first radiation source and radiation from the second radiation source; control means for varying the frequency of the electromagnetic radiation of the output signal by varying the temperature of the first radiation source and/or the temperature of the second radiation source; and detecting means for detecting a response signal, wherein the control means is adapted to vary the temperature of the first radiation source within a first pre-determined range of temperature and to vary the temperature of the second radiation source within a second pre-determined range of temperature, wherein each of the first pre-determined range of temperature and the second pre-determined range of temperature is a range of temperature within which no mode hop occurs in the first radiation source or in the second radiation source respectively.