| 摘要 |
PURPOSE:To reduce a minor lobe to improve a direrctional pattern, by winding an eddy current generating coil so that the windig density is high in the inside and is low in the outside. CONSTITUTION:When a DC is flowed to a magnetic field generating coil 2 wound around an iron core 1, a magnetic field B is generated near the surface of a material 4 to be examined. A gnerating coil 3a arranged on the lower face of the iron core 1 is wound spirally so that the winding density is high in the inside and is low in the outside. When a current (i) is flowed to the eddy current generating coil 3a, an inside density II of the eddy current is higher than an outside density Iphi, and an inside force FI of a force F generated on the surface of the material to be examined is larger than an outside force Fphi. It is known that a minor lobe is suppressed when the peripheral part is oscillated more weakly than the center in the field of the ultrasonic oscillator, and thus, the minor lobe becomes smaller than conventional lobes. |
