PURPOSE: To enable the judging of the availability of an open hole and the presence of a foreign matter in the hole by a method wherein inspection light is analyzed spectrally into transmission light and split light orthogonal in the direction of polarization to be converted into binary coded signals and a logical operation of both the signals is performed.
CONSTITUTION: When a polarization beam splitter 10 is provided which transmits light having a polarization surface parallel with the polarization surface of inspection light while the light having other polarization surfaces than that is turned to a split light in the direction orthogonal to the direction of impingement thereof, a part or the whole of the inspection light is turned to a transmission light to be impinged into a photosensor 91, hence, bringing a signal A to a logic value 1 according to intensity of light with the presence of an open hole at a specified position of a substrate 1. At this point, when there is no change in the polarization property of the inspection, no split light is outputted and hence, the logic value of a signal B of a photosensor 92 becomes zero, which leads a judgement that the open hole is through completely. On the other hand, when the passing light is turned to an eliptically polarized light, the split light raises an output level of the sensor 92, bringing the signal B to 1 thereby enabling the judging of the presence of a eliptically polarized light characteristics material in a through hole like Mylar.
ANDO MORITOSHI
OKA KOJI
