Patent ID: 6941798

Claim:
A scanning probe microscope comprising: a cantilever having a probe at a distal end thereof; an oscillator for generating a resonance signal near a resonance of the cantilever; vibrating means connected to receive the resonance signal generated by the oscillator as a driving signal for vibrating the cantilever while the probe is in close proximity to a surface of a sample; extracting means for extracting a displacement signal corresponding to displacement of the cantilever during vibration thereof; a variable gain amplifier for adjusting a gain of the displacement signal extracted by the extracting means so as to satisfy the equation G=(A/A 0 )*G 0 to control a quality factor value of the cantilever resonance to an optimal quality factor value, where G represents a gain value of the variable gain amplifier, A represents a preselected oscillation amplitude of the oscillator, A 0 represents an initial oscillation amplitude of the oscillator, and G 0 represents a gain value of the variable gain amplifier when the initial oscillation amplitude of the oscillator is A 0 ; and an adder for superimposing an output signal from the variable gain amplifier with an output signal from the oscillator to generate a signal for use as the driving signal received by the vibrating means for vibrating the cantilever.