Patent ID: 8245316

Claim:
A scanning probe microscope for measuring properties of a sample comprising: a probe on a mechanical resonator, an oscillator generating a master signal (S), an actuator driven by said master signal (S) and applying a mechanical force to said mechanical resonator at a frequency f, a DC voltage source applying a DC voltage (Udc) to said probe, an AC voltage source applying an AC voltage (Uac) substantially at said frequency f to said probe, a detector assembly measuring at least one observed signal depending on the frequency (f) of the master signal, the amplitude (K) of the master signal, and/or a phase shift (φ) of said deflection in respect to the master signal (S), said scanning probe microscope further comprising a phase modulator for generating a periodic modulation of a phase shift of said AC voltage in respect to said master signal, said periodic modulation of the phase shift having a frequency fmod, a voltage control loop measuring a spectral component of said observed signal at said frequency fmod and controlling said DC voltage (Udc) to keep said spectral component zero.