METHOD FOR FORMING TWO-DIMENSIONAL IMAGE IN AC MAGNETIC FIELD AND METHOD AND DEVICE FOR INSPECTING ARTICLE UTILIZING METHOD CONCERNED

摘要

PURPOSE:To execute the two-dimensional display of a density distribution in an AC magnetic field and to detect other foreign matter than a metal, as well by sampling successively the outputs of many reception coils distributed on the magnetic field detection surface, and displaying them in color, etc., in the corresponding position of a TV screen. CONSTITUTION:On the surface of a rectangular substrate 1 consisting of an insulating material, (i)X(j) pieces of reception coils Lij are arranged and an outgoing coil W for generating a high frequency magnetic field is provided with an interval against the coils Lij. Subsequently, the parts 3 to be inspected is arranged between the coil W and the Lij. Next, the TV screen is allowed to correspond to the coils Lij, and divided into (i)X(j) pieces of display areas Pij. A high or low induced voltage obtained by bringing successively the outputs of the coils Lij to sampling is displayed by light and darkness or color of a picture element in the corresponding display area on the TV screen. In such a manner, the density of an AC magnetic field in each place on the magnetic field detection surface can be looked at microscopically. Accordingly, other foreign matter than the metal can also be detected.