Pulse phase infrared thermography

Abstract

In this paper a novel approach is proposed which combines simultaneously advantages both of pulse (PT) and modulated (MT) infrared thermography. In a nondestructive evaluation perspective, the specimen is pulse-heated as in PT and the mix of frequencies of the thermal waves launched into the specimen are unscrambled by performing the Fourier transform of the temperature evolution over the field of view. Of interest is the maximum phase image with many attractive features: deeper probing, less influence of surface infrared and optical characteristics, rapid image recording (pulse heating, surface-wide inspection), possibility to inspect high thermal conductivity specimens. Several results are presented and the theory is discussed as well.-2 -

Thermographic Signal Reconstruction with periodic temperature variation applied to moisture classification

“…Moreover it is taken into account a possible slow trend in the laboratory conditions such that it could be described by a simple linear function. With such assumptions the temperature of each pixel in the thermographic sequence is well approximated by a function such that: (2) where T is temperature, i,j are indexes of the pixel in the image matrix. The amplitude of the periodic part of the temperature function and its phase are given respectively by:…”

“…It is named TSR for the capability to reconstruct the temperature signal from few polynomial coefficients with great compression capabilities and noise reduction. Very popular is the PPT (Pulsed Phase Thermography) [2] also. It is well known that a suitable superposition of sines and cosines could approximate almost any function.…”

Development of Infrared Techniques for Practical Defect Identification in Bonded Joints

“…The software is only able to export video image files and does not export the corresponding calibration files. The data presented in 131 this section is taken from video files and no calibration to temperature has been carried out, as such results are presented in grey level. The aim of this section is to explore the potential of using such a low cost device for NDE applications.…”

“…All free surfaces of the sample were set so that convection could occur controlled by appropriate heat transfer coefficients found in the literature [116,131]. …”

Non-Destructive Testing by Means of Frequency Modulated Infrared Imaging

“…Thermographic methods broadly divided into two types: passive , in which the temperature pattern of thesurface of material is measured without any external thermal excitation, and active in which thermal energy is artificially injected in to the material to be tested [1] . Although several methods have been proposed over the years to detect delamination defects in solid materials, three of them are predominantly in use: Pulse Thermography (PT), lock in Thermography (LT) and Pulse Phase Thermography (PPT) [2], [3], [4].…”