Patent ID: 7813900

Claim:
A displacement detection method to be implemented in a computer, comprising: a Fourier transform procedure causing the computer to subject an intensity signal of an acquired image to a Fourier transform to obtain a Fourier transformed signal; a procedure causing the computer to carry out a filtering process which destroys an Hermitian symmetry of the Fourier transformed signal to obtain a filtered Fourier transformed signal; a procedure causing the computer to obtain a complex analytic signal by carrying out an inverse Fourier transform on the filtered Fourier transformed signal; a phase singularity acquiring procedure causing the computer to acquire a phase singularity where values of both a real part and an imaginary part of the complex analytic signal become zero; a phase singularity specifying procedure causing the computer to acquire predetermined feature parameters from a phase structure of the phase singularity and to specify the phase singularity based on the feature parameters; and a displacement detecting procedure causing the computer to detect a displacement by detecting a position of the phase singularity after the displacement based on the feature parameters acquired by the phase singularity specifying procedure.