An observer based Q control method for a cantilever in an atomic force microscopy is provided that provides for a "dual" Q behavior such that a particular effective Q is achieved when a sample is present and another effective Q when a sample is absent. In the control method, the transfer function from dither input to photo-diode output is independent of the observer so that the cantilever effectively behaves like a spring-mass-damper system. The effective quality factor and stiffness of the cantilever can be changed by appropriately choosing the state feedback gain. The method provides sample-imaging using transient atomic force microscopy.