S. Komatsu：Laser Microscopes Based on Optical Heterodyne Detection, Rev. Laser Eng., Vol. 24 (1996) 1068-1076.

Abstract: Laser scanning microscopes based on optical heterodyne detection are reviewed. Optical heterodyne phase detection technique allows noncontact surface profile measurement with height sensitivity of the order of 1 Å or even better. Combined with atomic force microscopy, the lateral spatial resolution of laser heterodyne phase micrscopy is much improved up to several Å, which enables atomic resolution imaging of a sample surface. On the other hand, optical heterodyne intensity detection technique has a unique feature of confocal imaging ability, and its high signal to noise ratio due to heterodyne detection allows us to observe 3 dimensional distribution of light scattering particles through an obstructing rough surface.