Autoconfocal microscopy with nonlinear transmitted light detection

We describe a simple and robust technique for transmission confocal laser scanning microscopy wherein the detection pinhole is replaced by a thin second-harmonic generation crystal. The advantage of this technique is that self-aligned confocality is achieved without the need for signal descanning. We derive the point-spread function of our instrument and quantify both signal degradation and background rejection when imaging deep within a turbid slab. As an example, we consider a slab whose index of refraction fluctuations exhibit Gaussian statistics. Our model is corroborated by experiment. © 2004 Optical Society of America OCIS codes: 110.0180, 180.1790, 180.5810, 030.6600, 190.4160.