Patent ID: 7487667

Claim:
A probe apparatus for measuring an electron state on a sample surface, comprising: a cantilever provided with a probe opposing the sample surface with a gap, a charge transfer force being applied between the probe and the sample surface; a vibrating unit configured to support and vibrate the cantilever; a first light emitting module configured to emit a first light beam onto the cantilever; a sensor configured to sense the first light beam reflected from the cantilever to generate a sensor signal; a feedback circuit configured to drive the vibrating unit in response to the sensor signal so as to cause the cantilever to be self-excited and vibrated at a resonance frequency which is fluctuated due to a change of the charge transfer force; a second light emitting module configured to emit a second light beam to irradiate the sample surface, intermittently, the irradiation of the second light beam changing the charge transfer force; and a controller configured to control the second light emitting module in response to the sensor signal from the sensor, the controller detecting a current vibrating period of the probe vibrated at the resonance frequency from the sensor signal and setting an irradiation timing of the second light beam based on the current vibrating period.