Coherence artifacts in second harmonic microscopy

In SHG microscopy interferences from constant background contributions can lead to severe distortions of the SH image as compared to the true interfac e morphology. Similar phenomena may occur in time dependent SH measurements . We present an analysis of these effects and demonstrate a simple, yet power ful technique to eliminate these coherence artifacts. The technique relies on a superposition of the signal field with a coherent auxiliary SH-field o f controllable phase and amplitude and allows a direct observation of the t rue chi((2))-morphology of the interface.