Photothermal pyrometry for temperature measurement

Noncontact precision temperature measurement is desirable in many industrial processes. Two major factors limiting the accuracy of temperature measurement by the conventional radiation pyrometry are the ambient radiation and the surface emissivity variations. This work explores the potential of photothermal pyrometry for the temperature measurement of different materials. In this method, a laser is employed to create a small periodic temperature perturbation on the sample, which induces a modulation of the thermal emission signal from the sample. Under appropriate conditions, this modulated radiation signal is independent of the ambient radiation and can be utilized to obtain the temperature of the object. A criterion is established that determines the applicability of the photothermal pyrometry technique. Preliminary results are presented for temperature measurement of silicon and aluminum samples in radiation environment, and of an electrically heated metallic fine wire.