Lateral Force Microscopy (LFM) differs from AFM because it uses a position-sensitive photodetector (PSPD) to detect the lateral defection of the cantilever rather than the vertical deflection. An LFM's PSPD is divided into quadrants (A-D), rather than an AFM's halves, to allow for the sensation of the later components of the cantilevers deflection. A system can generate both LFM and AFM data simultaneously if it is engineered properly.
These lateral deflections of the cantilever result from forces parallel to the plane of the sample surface. This can be caused by changes in surface friction or slope. LFM is useful for imaging these surface variations.