A Design of Excitation Source for the Optical Lock-In Thermography

摘要

Optical lock-in thermography is an important non-destructive testing (NDT) method which has been widely used in many industrial applications, such as modern aerospace, renewable energy and nuclear industry. This method has advantages of better signal-to-noise (S/N) ratio and adjustable depth range for defect detection. The excitation source is an important part of the optical lock-in thermography system whose performance has a decisive effect on the defect detection. It is challenging for the design of the excitation source because of wide frequency range requirement (typically 0.01Hz to several hundred kHz) and high power (typ-ically hundreds of W to several kW). This paper presents the design of a novel excitation source with a maximum output power of 2.5kW and a frequency range of 0.01Hz to 100 kHz which is used to drive halogen lamps. The proposed topology, operating principle, the design procedure of the circuit parameters have been described in detail. The essential performance and its effectiveness of the proposed excitation source are demonstrated by an experiment where a lead-steel sample with metal-metal bonded structure has been tested-for validation.