A novel oscillated probing technique for a nano-CMM is proposed, which uses an optically trapped particle. A micro-silica particle as a probe is trapped by tightly focused Nd: YAG laser light using an objective in the air. The trapped particle is laterally oscillated at the focal plane of the objective using AOD (acousto-optical deflector). In order to monitor the oscillating state, He-Ne laser beam is arranged coaxially with the trapping laser beam. Both the amplitude and the phase delay are analyzed by detecting the backscattered light from the particle. First, we examined the lateral spring constant of the probe using the theoretic model. Next, the property of the probe was examined while approaching to a workpiece. The oscillating state was found to be changed with the resolution of several dozen nanometers due to the interaction between the workpiece and the probe, and by the reflected light from the surface of the workpiece. Then, we conducted the fundamental measurement of a step height specimen and obtained a agreement between measurement results by our proposed probe and by the AFM.
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