Abstract: A camera captures a predetermined range including a beam spot of a laser beam irradiated on the first and second sheet metals to be welded. An image analysis device determines whether a welding defect has occurred, based on an image signal obtained by capturing the first and second sheet metals. The image analysis device sets an analysis window in a frame of the image signal, and a center of the beam spot is located at a reference point set in the analysis window. A region extractor extracts pixels of a region of interest whose position is set with reference to the reference point corresponding to a welding defect of a determination target, among pixels included in the analysis window. A welding defect determination unit determines whether the welding defect of the determination target has occurred, based on luminance in the region of interest.

Abstract: A method for fabricating an HBT in which the subcollector-base junction, which contributes to the base-collector capacitance of the device, is reduced by using a selective subcollector. In particular, subcollector areas of the device that do not contribute to collector resistance reduction are eliminated, thereby reducing the subcollector area, which, in turn, reduces the base-collector capacitance. As such, the maximum power-gain frequency f.sub.max is increased.