1. Principle of the scanning probe microscope

To appreciate the originality of these new instruments, and to pinpoint the origin of their excellent resolving power, we need to return briefly to the operating principle of a traditional microscope.

In traditional microscopes (optical or electronic), a source of waves (or particles) illuminates an object. The scattered radiation is then directed through optics to the detector (CCD, etc.), which gives an enlarged image of the object. The source-sample and sample-detector distances are much greater than the wavelength $\lambda$ of the used radiation.

The smallest distance that can be perceived in the image plane (inverse of the lateral resolving power) is of the order of $\lambda$...