SOLUTION TO THE BISTABILITY PROBLEM IN SHEAR FORCE DISTANCE REGULATION ENCOUNTERED IN SCANNING FORCE AND NEAR-FIELD OPTICAL MICROSCOPES

The bistability problem, common to scanning microscopes employing late ral dithering of the probe for image formation (i.e., shear force micr oscope) or probe-sample distance control (i.e., near-field optical mic roscope) is shown to stem from the two nearly degenerate vibration deg rees of freedom possessed by a laterally dithered fiber. Controlling t he fiber vibration direction by means of a four-sectioned piezo was fo und to be a simple and effective solution of the problem. An image of a microtubule is presented to demonstrate the improved imaging ability . (C) 1997 American Institute of Physics. [S0003-6951(97)03843-6].