Patent ID: 7946992

Claim:
A velocity measuring method for measuring a velocity of a moving reflection object constituting a velocity measuring object by using N time series signals formed by arranging echo signals of N pulse waves, which are sequentially transmitted toward the velocity measuring object at a predetermined time interval and are received as the echo signals, in order of the transmission time, the velocity measuring method comprising: an acquisition step of acquiring echo signals of the N pulse waves; an expanding step for expanding the N time series signals by using 0-th to (N−1)-th degree discrete Legendre function as a base; a complex expansion coefficient calculating step for calculating a 2n-th degree complex expansion coefficient by multiplying a linear combination of a (2n−1)-th degree expansion coefficient and a (2n+1)-th degree expansion coefficient by an imaginary unit and then linearly combining the result and a 2n-th degree expansion coefficient, and calculating a (2n+1)-th degree complex expansion coefficient by multiplying the (2n+1)-th degree expansion coefficient by an imaginary unit and then linearly combining the result, the 2n-th degree expansion coefficient and a (2n+2)-th degree expansion coefficient, wherein n is a natural number, the expansion coefficients are obtained by the expanding step; and the degree of the expansion coefficients is 1 or over and (N−1) or below; a degree determining step for determining a degree m of a coefficient having the maximum absolute value among the complex expansion coefficients; and a velocity signal calculating step for calculating a velocity of the moving reflection object as a signed velocity signal distinguishing its direction whether it is a transmitting direction of the pulse waves or an opposite direction from a ratio of square sums of the expansion coefficients or complex expansion coefficients corresponding to the degree m.