| 摘要 |
PURPOSE:To improve an S/N ratio, and also to execute a compensation against lift-off variation, too, by separating an eddy current detecting signal into an X signal and a Y signal of two orthogonal signal components, amplifying each of them by different amplification factors, respectively and also executing a phase compensation. CONSTITUTION:The noise due to a mechanical factor such as a vibration of a magnetic detector is determined well-definedly when the magnetic detector, etc. are determined, therefore, an X signal and a Y signal being orthogonal to each other are obtained by setting suitably a phase angle of a synchronizing detector 11. These X signal and Y signal are inputted to each different amplification factor 14, 15, a phase difference of a flaw component S and a noise component N is expanded, and an S/N ratio is improved. The X signal and Y signal obtained by detecting synchronously are inputted together with a lift-off signal to multipliers 25, 26 which have determined an amplification factor by calculating an amplitude of the flaw component and a phase compensating value basing on the lift- off signal by a microcomputer 22, and signals X', Y' which have compensated a lift-off variation are obtained. |
