Interferometric Testing of Materials
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Local surface properties of a material are analyzed by means of a two-beam phase-sensitive interferometric device in which one of the pulsed beams has a high intensity to periodically heat the surface locally and both beams are used to analyze the time-dependent growth and decay of the local thermal expansion. Fig. 1 shows an example of testing a conductor 5 embedded in a substrate 4, e.g., a printed circuit board. An intensity-modulated polarized laser beam L0 is deflected at semi-transparent mirror 2 to a birefringent crystal 3 which is oriented such that beam L0 is split into a high intensity beam L1 to be focussed on conductor 5 and a low intensity reference beam L2 impinging on substrate 4.