Abstract: Disclosed herein is a method and apparatus for simultaneously measuring a displacement and angular variations. The method and apparatus of the present invention allows light radiated from a single light source to be placed along a light axis so as to simultaneously measure a distance (displacement) and angular variations that are different physical quantities, so that the displacement and angular variations of the measuring device of a precision measuring apparatus or machining device of a machine tool moved by a stage can be simultaneously measured without an Abbe error.

Abstract: Disclosed is an atomic force microscope. A Fabry-Perot interferometer where the intensity of light reflected at a cantilever through an optical fiber varies sensitively to a displacement of the cantilever is constructed to accurately measure a distance between the optical fiber and the cantilever. A Fabry-Perot resonator is formed by the optical fiber having an end of a concave mirror shape and a reflective surface of the cantilever. A displacement of a cantilever tip is measured by detecting a signal reflected at the resonator and a feedback signal corresponding to a variation in the displacement of the cantilever tip is generated. The displacement of the cantilever tip is kept constant by actuating a piezoelectric element in a Z-axis direction.

Abstract: Disclosed is an atomic force microscope. A Fabry-Perot interferometer where the intensity of light reflected at a cantilever through an optical fiber varies sensitively to a displacement of the cantilever is constructed to accurately measure a distance between the optical fiber and the cantilever. A Fabry-Perot resonator is formed by the optical fiber having an end of a concave mirror shape and a reflective surface of the cantilever. A displacement of a cantilever tip is measured by detecting a signal reflected at the resonator and a feedback signal corresponding to a variation in the displacement of the cantilever tip is generated. The displacement of the cantilever tip is kept constant by actuating a piezoelectric element in a Z-axis direction.

Abstract: Disclosed is a method for correcting a nonlinearity error in a two-frequency laser interferometer which measures the phase angle using 90° phase mixing technique and a method for measuring a phase angle by using the same. The phase angle correcting method includes the steps of: calculating ellipse parameters, such as amplitudes, offsets and a phase difference of two sine and cosine output signals from the nonlinearity error correcting electronics; calculating an adjusting voltages for correcting offsets, amplitudes and a phase of the output signals; conducting a correction wherein offsets of output signals become zero, amplitudes are same, and a phase difference beyond 90° between the output signals becomes zero; and applying the output signals whose offsets, amplitudes and phase are corrected to Equation (&thgr;=arctan(Iy′/Ix′)) to calculate the phase angle.