Characterization and Energy Absorption Efficiency Determination of LED as an Effective Photothermal Excitation Source in Lock-In Thermography

This paper studies the use of light-emitting diode (LED) as an excitation source for photothermal lock-in experiments, and investigates the energy absorption efficiency and signal-to-noise ratio of the established setup. Existing lock-in excitation sources usually use high power (in the range of kilowatt) halogen lamps. The present LED excitation source has an advantage of low power consumption making the setup much more energy efficient. Another advantage of LED in this paper is their low infrared (IR) content, in contrast to halogen lamps, the IR content gets reflected into the IR camera, and leads to an unpredicted change in phase image in lock-in thermography.