On Amplitude Estimation for High-Speed Atomic Force Microscopy

Amplitude estimation or demodulation plays a vital part in the control loop of dynamic mode high-speed atomic force microscopy (AFM). The closed-loop bandwidth will be limited by the convergence speed of the estimator. Recent developments have introduced new ways of demodulating the measured deflection signal. This article reviews and compares present methods for AFM amplitude demodulation and introduces a new Lyapunov based estimator. The performance of the techniques are discussed in terms of bandwidth, measurement noise, convergence time, unwanted harmonics, and complexity.