The use of a pulsed laser with a lock-in amplifier has been shown to increase the detection sensitivity of scanning optical microscopes by a factor of ten. In this article, the authors explain how they implement laser pulsing without a lock-in amplifier through software control. The detection sensitivity of their method, which is based on a digital signal integration algorithm, has been shown to be comparable to that achieved with a lock-in amplifier. Several case studies illustrate the effectiveness of the technique for locating various types of defects.

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