A scanning probe microscope and method for operating the same are disclosed. The microscope includes a probe mount for attaching a probe, an electro-mechanical actuator, a probe position signal generator, an impulse signal generator and a servo. A probe tip is mounted on a first end of a cantilever arm, a second end of the cantilever arm being mounted on a mechanical vibrator that causes the second end to vibrate in response to a drive signal. The probe position signal generator generates a position signal indicative of a position of the probe relative to the second end of the cantilever arm. The impulse signal generator measures a quantity related to an impulse imparted to the probe tip by the interaction between the tip and the local characteristics of the sample. The servo operates the electro-mechanical actuator so as to maintain the measured quantity at a predetermined value.